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Takuma Ohashi, [Linawati Sutrisno](https://orcid.org/0000-0003-3085-9660), [Yu Yamashita](https://orcid.org/0000-0001-7966-3197), [Katsuhiko ARIGA](https://orcid.org/0000-0002-2445-2955)

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[Biochemical pathways for device nanoarchitectonics: organic semiconductors interfaced with biomolecular systems](https://mdr.nims.go.jp/datasets/165feb8a-4052-48eb-af05-9740ab254957)

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Biochemical pathways for device nanoarchitectonics: organic semiconductors interfaced with biomolecular systemsApplied PhysicsExpress      APEX REVIEW • OPEN ACCESSBiochemical pathways for devicenanoarchitectonics: organic semiconductorsinterfaced with biomolecular systemsTo cite this article: Takuma Ohashi et al 2026 Appl. Phys. Express 19 040106 View the article online for updates and enhancements.You may also likeThe Application of OrganicElectrochemical Transistors in BiosensorsFeng Yan-Electrochemical, EPR and QuantumChemical Study of Pyrene-CyclobuteneConjugatesLucie Kolacna, Jií Klíma, Alan Liška et al.-Foreword-This content was downloaded from IP address 144.213.253.16 on 01/05/2026 at 08:55https://doi.org/10.35848/1882-0786/ae6166/article/10.1149/MA2010-02/29/1817/article/10.1149/MA2010-02/29/1817/article/10.1149/MA2021-01421708mtgabs/article/10.1149/MA2021-01421708mtgabs/article/10.1149/MA2021-01421708mtgabs/article/10.1088/1742-6596/704/1/011001aaaBiochemical pathways for device nanoarchitectonics: organic semiconductorsinterfaced with biomolecular systemsTakuma Ohashi1,2, Linawati Sutrisno3, Yu Yamashita1,4, and Katsuhiko Ariga1,2,4*1Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044,Japan2Graduate School of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Japan3International Center for Young Scientists (ICYS), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan4The Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba277-8561, Japan*E-mail: ARIGA.Katsuhiko@nims.go.jpReceived March 16, 2026; revised April 7, 2026; accepted April 17, 2026; published online April 30, 2026This review discusses organic semiconductors interfaced with biomolecular systems, focusing on the construction of material systems throughbiochemical pathways for device nanoarchitectonics. The initial section highlights biosensors as representative applications at the interface ofdevice engineering and biosystem science. The subsequent sections describe nanoarchitectonics approaches for the synthesis and organizationof organic semiconductor devices using bioprocessing. In particular, doping of organic semiconductors in water under ambient conditions coupledwith bioprocessing are emphasized, including proton-coupled electron transfer and sugar redox reactions. Inspired by the sophisticated moleculararchitectures that enables ultra-high-level functions in biological systems, nanoarchitectonics is expected to facilitate further advances in organicsemiconductor biodevices. © 2026 The Author(s). Published on behalf of The Japan Society of Applied Physics by IOP Publishing Ltd1. IntroductionHuman civilization depends on the availability of materials,machines, and devices, and advances in these technologieshave significantly improved our quality of life. From amaterials perspective, scientific progress during the 20thcentury represented a major turning point. In addition tonaturally occurring substances, developments in variousfields of chemistry have enabled the creation of a widerange of new materials. This trend continues today inchemistry-related disciplines such as organic chemistry,1–4)inorganic chemistry,5–8) polymer chemistry,9–12) supramole-cular chemistry,13–16) coordination chemistry,17–20) materialschemistry,21–24) and biochemistry.25–28) Physics also playsan essential role in the detailed investigation of the physicalproperties of these materials. In particular, the developmentof highly accurate, high-resolution analytical techniques hasclarified the fundamental principles underlying the propertiesand mechanisms of microstructures and nanostructures.29–31)Owing to these advances in chemistry and physics, it hasbecome widely recognized that controlling nanostructuresand their properties at the nanoscale is crucial.32–34) Theproperties of a given material can vary dramatically de-pending on its nanostructures. In some cases, precise controlof nanostructure can lead to unique properties and highlyfunctional systems.35–37) In this context, the emergence ofthe concept of nanotechnology marked a critical step in thisscientific trend.38,39)Nanotechnology has enabled the observation40–42) andmanipulation43,44) of structures at atomic and molecularlevels. Furthermore, it has significantly advanced the char-acterization of physical properties at these correspondingscales.45–48) These developments have deepened our under-standing of the fundamental principles governing nanoscalephysics. Such knowledge should now be applied to thedevelopment of functional materials. Nanoarchitectonics, apost-nanotechnology concept, has been proposed to achievethis goal (Fig. 1).49) It involves constructing functionalmaterial systems from atomic- and molecular-scale buildingblocks.50–52) By integrating nanotechnology with materialschemistry and physics, nanoarchitectonics provides a com-prehensive framework for the creation of functional mate-rials. In this approach, materials are assembled using avariety of techniques, including atomic and molecularmanipulation, chemical transformations (including organicsynthesis), physical transformations, self-assembly and self-organization, alignment and structurization induced by ex-ternal forces or fields, micro- and nanofabrication, andbiochemical processes.53–55) This concept emphasizes theintegration of multiple technologies, and the constructionprocess often involves multiple stages. Compared withsingle-step self-assembly, nanoarchitectonics is particularlyadvantageous for fabricating asymmetric and hierarchicalstructures.56) Because all materials are composed of atomsand molecules, nanoarchitectonics can, in principle, beapplied to the creation of virtually any material system. Ifthe ultimate theory of physics is regarded as a “theory ofeverything,”57) nanoarchitectonics may be considered amethodology applicable to virtually everything in materialsscience.58,59)Although the term “nanoarchitectonics” is relatively new, thefundamental concepts underlying this methodology have beenexplored for decades. Two representative examples can beconsidered—one artificial and the other natural. The firstexample is the development of devices such as highlyintegrated circuits, which have progressed through increasinglevels of integration enabled by ultrafine processing technolo-gies. Subsequently, the importance of various materialinnovations,60–63) quantum effects,64–66) and structural organi-zation techniques—such as interface manipulation,67–69) andsupramolecular organization70–72) —has become evident.Device development is therefore a field in which the integrationof top-down and bottom-up processes is steadily advancing.This research and technological field can be regarded as aContent from this work may be used under the terms of the Creative Commons Attribution 4.0 license. Any further distribution ofthis work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.040106-1© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdApplied Physics Express 19, 040106 (2026) APEX REVIEWhttps://doi.org/10.35848/1882-0786/ae6166https://crossmark.crossref.org/dialog/?doi=10.35848/1882-0786/ae6166&domain=pdf&date_stamp=2026-04-30mailto:ARIGA.Katsuhiko@nims.go.jphttps://creativecommons.org/licenses/by/4.0/https://doi.org/10.35848/1882-0786/ae6166representative example of nanoarchitectonics as a comprehen-sive approach for constructing functional structures.73–75)Biofunctional structures provides prime examples ofsuccessful molecular architectures, and demonstrate thepotential for constructing functional material systems basedon concepts similar to nanoarchitectonics. In variousbiological systems, including those involved inphotosynthesis,76,77) functional molecules are arranged ina highly organized manner, enabling the execution ofcomplex functions. These structures are as if functionalmolecules were assembled according to an ingeniousblueprint. Such biological systems can therefore be re-garded instructive models for nanoarchitectonics.77–79)Examples like these provide important inspiration for thedevelopment of nanoarchitectonics strategies. To constructsuch advanced functional systems, we should aim toachieve in a few decades what nature has accomplishedover billions of years.Integrating these two successful concepts of nanoarchi-tectonics—artificial device fabrication and biological func-tional systems—is highly significant. In particular, thisintegration leads to device development involving biopro-cesses. This review discusses the development of devicematerials utilizing bioprocesses and devices from the per-spective of nanoarchitectonics. Accordingly, we focus onmaterials that can function from intermediaries betweenbiosystems and electronic devices. Such materials are softand flexible, similar to biosystems, while possessing specificelectronic functions. Representative candidates include con-ductive polymers80–82) and organic semiconductors83–85)including polymeric semiconductors.86–88) Consequently,this review primarily focus on the coupling of organicsemiconductor nanoarchitectonics with bioprocesses fordevice applications.With this background, we briefly summarize the advan-tages of organic semiconductors and explain why they haveattracted considerable attention. Organic semiconductors arecomposed of organic compounds and exhibit several advan-tages compared with conventional inorganic semiconductorssuch as silicon. These advantages includes low cost, lightweight, ease of fabrication, and compatibility with flexiblesubstrates. In addition, organic semiconductors offer asignificant advantage in terms of functionality because theirproperties can be readily tailored through moleculardesign.89–91) For example, substituents can be introducedand the length of aromatic conjugation can be adjusted tooptimize performance for specific applications. Furthermore,organic semiconductors with systematically varied molecularstructures can be synthesized. Low-temperature processing isalso possible, and large-area thin films can be readilyfabricated using solution-based processes.92–94) Thus, or-ganic semiconductors are well suited to nanoarchitectonicsinvolving molecular design and the fabrication of thin-filmstructures.Accordingly, this review discusses “organic semiconduc-tors interfaced with biomolecular systems,” with a focus onthe constructing material systems through “biochemicalpathways for device nanoarchitectonics.” Biological pro-cesses offer several advantages, including low environmentalimpact, high specificity and selectivity, and low toxicity tothe human body. In addition, biomolecular reactions enableprecise control of electron transfer, which can be utilized inthe development of electronic materials. The flexibility andlightweight nature of organic semiconductors also makethem promising candidates for wearable devices.95–97)Therefore, incorporating biomolecular processes that exertminimal impact on the human body is highly attractive forthe development of such devices. This review highlightsFig. 1. Outline of nanoarchitectonics, a post-nanotechnology concept, for constructing functional material systems from atomic and molecular-scaleobjects through fusing nanotechnology with material chemistry and physics.040106-2© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWrecent research trends in organic semiconductors systemsthat employ biomolecular processes.The following section focuses on biosensors as represen-tative examples of applications at the interface betweendevice engineering and biosystem science. Several examplesinvolving both small molecules and polymers are presentedto illustrate the potential functionalities of organic semicon-ductors when interfaced with biomolecular systems. Thesubsequent section discusses nanoarchitectonics approachesfor the synthesis and organization of organic semiconductordevices, with particular emphasis on bioprocessing. Thisincludes the fabrication of electronic materials throughbioprocesses and the organization of device materials withininterfacial environments. The next section addresses na-noarchitectonics related to doping, which is essential forthe processing of organic semiconductors. First, a generaloverview of doping is provided as a methodological guide,followed by recent examples of its coupling with bioproces-sing, including proton-coupled electron transfer (PCET) andsugar redox reactions. In addition, examples of devicestabilization through bioprocessing are introduced.Although the integration of bioprocessing with organicsemiconductor engineering is a relatively recent develop-ment, it holds significant potential. The final section dis-cusses future perspectives. This review aims to stimulatefurther exploration of biological reactions in the fields oforganic semiconductors and nanomaterials research.2. Usage examples of organic semiconductor devicefor biology: biosensorFirst, we provide an overview of the relationship betweenbioprocesses and organic semiconductor devices using ex-amples to illustrate this. Biosensors are devices that interfacewith biological systems. We then provide brief examples ofbiosensors that use organic semiconductors, and give anoverview of their structures and target materials.We focus on two types of transistor structures used forsensing: organic electrochemical transistors (OECTs) andextended-gate field-effect transistors. OECTs use electrolytesconsisting of aqueous solutions or ionic liquids and offergreater capacitance and transconductance than solid-statethin-film transistors. Consequently, they can be driven byextremely low voltages. Conversely, extended-gate transis-tors are constructed by attaching an extended gate to anexisting organic field-effect transistor (OFET), which en-ables the OFET to be operated in a dry environment. Thisavoids water, which contributes to device degradation, andenables long-term stable operation. Below, we introduce thespecific sensing targets and analytical methods employedwith these devices.2.1. Biosensor for small molecular gest2.1.1. Glucose sensor. Abnormal blood glucose levelsand impaired regulation of glucose metabolism can causeserious health problems, making the development of afford-able glucose sensors essential for effective health manage-ment on an individual level. OECTs have emerged as apromising platform for biosensing applications due to theirinherent advantages, such as low operating voltage require-ments and exceptional sensitivity. Glucose detection can beachieved by immobilizing the glucose-selective glucoseoxidase on the gate electrode. Several examples employingp-type channels based on PEDOT:PSS have been reported.One representative case, reported by Berggren, Stavrinidouand co-workers [Fig. 2(a)], involves a gate electrodefunctionalized with platinum nanoparticles and glucoseoxidase.98) In this system, the addition of glucose triggersan enzyme-catalyzed redox reaction that generates hydrogenperoxide. The Pt nanoparticles on the gate subsequentlyoxidize the hydrogen peroxide, leading to electron transferand a shift in the effective gate potential, which results in adecrease in the channel current. Specifically, glucose exportwas directly monitored in isolated chloroplasts from tobaccoplants. The OECT sensor was interfaced with the chloro-plasts, enabling the detection of glucose release with a timeresolution of 1 min.In contrast, Xu and co-workers reported the use of an n-type conductive polymer, the polymeric semiconductor poly(benzimidazobenzophenanthroline) (BBL), as the channelmaterial in an OECT [Fig. 2(b)].99) In this system, ferrocenewas co-immobilized with glucose oxidase on the gateelectrode, serving as an electron mediator to enhance theefficiency of electron transfer between the gold electrode andglucose oxidase. The BBL exhibited high performance andstability in aqueous electrolyte solutions. Stability testsconfirmed consistent performance under multiple cyclesand continuous stress, demonstrating the long-term stabilityand reliability of the sensor. Overall, the n-type polymersemiconductor-based OECT glucose sensor exhibited pro-mising performance, stability and flexibility, highlighting itsstrong potential for practical glucose sensing applications.2.1.2. Lactate sensor. Lactate is one of the key meta-bolic products in the anaerobic phase of glycolysis and animportant biomarker in clinical diagnosis and sportsmedicine.100,101) Although blood lactate levels have tradi-tionally been used for measurement, a positive correlationhas been observed between blood and sweat lactateconcentrations.102,103) This makes sweat lactate measure-ment a noninvasive method for quantitatively detectinglactate. Since lactate oxidase is selective for lactate, it canbe detected by immobilizing it on the gate electrode orchannel of an OECT. Pappa et al. reported a lactate sensorbased on an electron-deficient naphthalene diimide (NDI)copolymer [Fig. 3(a)],104) in which the enzyme was im-mobilized through interactions with the ethylene glycol sidechains. This provides good electrochemical contact with theredox-active copolymer, allowing electrons generated duringthe enzymatic reaction to be transferred to the polymerbackbone and change its conduction properties. This devicecan detect metabolites, such as lactate, with high sensitivityand low power consumption. In particular, the polar sidechains of the conducting polymer facilitate interaction withthe enzyme, enabling direct electrical detection without theneed for an intermediate. In another example, compositeconductive nanofiber materials were used to fabricate fiber-like OECTs, making them more suitable for wearabledevices.105)Meanwhile, Sasaki and Minami, in their mini-review,described a lactate detection method based on extended-gate transistors, which enables sensing without direct im-mersion of the active channel.106) In this system, lactateoxidase was immobilized on the extended gate electrode, anda solution-processable π-conjugated polymer, poly{2,5-bis040106-3© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEW(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene} (PBTTT), wasused as the channel material (Fig. 3(b)). During the OFEToperation, the gate voltage was applied via a referenceelectrode (Ag/AgCl). Both the extended gate electrode andthe reference electrode were immersed in the analyte solution(e.g. body fluid), and the potential difference was measured atthe interface between the sensing electrode and the analytesolution. The addition of lactate to the solution triggered anenzymatic reaction that induced electron transfer, therebychanging the surface potential of the sensing gate electrodeand resulting in variations in the drain current and thresholdvoltage.2.2. Sensor for biopolymer2.2.1. DNA/RNA sensor. DNA and RNA are essentialmacromolecules of the human body. They serve as thefoundational basis for storing, transcribing, expressing andregulating genetic information, and play crucial roles in alllife-sustaining processes. These two molecules were detectedusing single-stranded DNA (ssDNA) as a sensing element.When ssDNA binds complementarily to target ssDNA,double-stranded DNA is formed, causing change in thegate potential and channel current. Li, Chen, Wang and co-workers developed an ultrasensitive, label-free DNA detec-tion method using a solution-gated graphene transistorfunctionalized with carbon quantum dots [Fig. 4(a)].107)The carbon quantum dots were immobilized on the gateelectrode surface via mercaptoacetic acid containing a thiolgroup, and ssDNA probes were attached through strong π–πinteractions. Upon hybridization with complementaryssDNA, double-stranded DNA is formed and subsequentlydetaches from the carbon quantum dot surface, resulting in aDirac voltage shift and a corresponding channel current. Themethod achieved a low detection limit of 1 aM, enablingdiscrimination of single-base mismatches.Zhang, Yang, Li and co-workers also reported on asolution-gated graphene transistor biosensor for the ultra-sensitive and rapid quantitative detection of microRNA-21(miRNA-21), an early-stage prostate cancer biomarker[Fig. 4(b)].108) A ssDNA probe designed to specificallybind the miRNA-21 molecular target was immobilized ona gold gate, where it effectively hybridized with the target,inducing a voltage shift. Because miRNA-21 molecules areelectronegative due to their phosphate backbone, hybridiza-tion with the ssDNA probe corresponds to an offset voltageapplied at the gate electrode. The device also exhibited a lowdetection limit of 1 aM and single-base mismatches wereclearly distinguishable.2.2.2. Protein sensor. Proteins are among the keymacromolecules of life, and measuring protein concentrationis essential for medical diagnosis, biological therapy andprevention of related diseases. The detection of proteinsusing OECT-based biosensors typically relies on antigen–antibody interactions, in which either antibodies or antigensare immobilized on the gate or channel of an OECT asbiorecognition molecules. Yan et al. immobilized the spikeprotein (antigen) of severe acute respiratory syndromecoronavirus 2 (SARS-CoV-2) on the gate surface, enablingthe detection of SARS-CoV-2 immunoglobulin G (IgG)Fig. 2. Examples of glucose sensor: (a) OECT-based glucose sensor using the conducting polymer PEDOT:PSS with the gate electrode functionalizedwith platinum nanoparticles and glucose oxidase enzyme. Reprinted with permission from Ref. 98 Copyright 2020 Wiley-VCH; (b) OECT glucosesensor based on poly(benzimidazobenzophenanthroline) (BBL) as the n-type polymeric semiconductor channel material with immobilizing glucoseoxidase and ferrocene on the gate electrode. Reprinted with permission from Ref. 99. Copyright 2024 Elsevier.040106-4© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWthrough antigen–antibody interactions [Fig. 5(a)].109)Because proteins composed of zwitterionic amino acidscarry net charges depending on pH, changes in the localionic concentration and distribution near the gate modulatethe electrical characteristics of OECT, thereby enablingdetection. By optimizing the ion concentration and pH ofthe test solution, they achieved a detection range from 10 fMto 100 nM (covering the SARS-CoV-2 IgG concentrationrange in human serum) and enabling specific detectionwithin minutes.The detection of human epidermal growth factor receptor2 (HER2), an important prognostic biomarker for breastcancer, has also been reported. Yang et al. fabricated anHER2 sensor by using PEDOT:PSS as a conductive polymerand immobilizing an anti-HER2 antibody on the gateelectrode.111) This protein sensor was capable of detectingHER2 at concentrations as low as 10−14 g ml−1, which isseveral orders of magnitude lower than the detection limitsof previously reported electrochemical methods.Furthermore, the device could reliably distinguish betweenbreast cancer cells and normal cells over a wide range ofconcentrations.Wang et al. developed a sensor for the detection ofsurvivin protein, a human gene product found in cancer cells[Fig. 5(b)].110) In this sensor, the gate electrode was firstfunctionalized with mercaptoacetic acid, followed by im-mobilization of anti-survivin antibodies. The authors fabri-cated an ultrathin, micropatterned MXene/PEDOT:PSS-based OECT biosensor, which enabled the detection ofsurvivin protein at concentrations as low as 10 pg ml−1 inthe OECT electrolyte. A comparison with a commerciallyavailable enzyme-linked immunosorbent assay kit showedgood linearity in detection response.Although these represent only a small subset of thepotential applications, organic semiconductors have beenshown to enable the detection of biomolecules spanning awide range of molecular sizes. These findings highlighttheir considerable potential to contribute to the develop-ment of next-generation biosensing devices. To furtheradvance this field, it is essential to establish more sophis-ticated nanoarchitectonics designs of device materialsand structures. The following sections will discuss thenanoarchitectonics of organic semiconductors in termsof material fabrication, structural control and dopingcontrol.3. Nanoarchitectonics for bio-relevant organicsemiconductor devicesIn the previous section, we presented several examples ofbiosensors to illustrate how devices based on organicpolymer semiconductors and conducting polymers caninteract with biological systems. These examples stronglyindicate that such devices could play a crucial role in variousbioprocesses. However, realizing more rational device de-signs will require multifaceted structural control and theintegration of multiple fabrication processes. Because thesetechnologies fundamentally rely on constructing materialsand devices from the nanoscale, the concept ofFig. 3. Examples of lactate sensor: (a) OECT lactate sensor using an electron-deficient naphthalene diimide (NDI) copolymer, allowing electronsgenerated during the enzymatic reaction (lactate oxidase) to be transferred to the polymer backbone and change its conduction properties. Reprinted withpermission from Ref. 104. Copyright 2018 AAAS; (b) lactate sensor using a solution-processable π-conjugated polymer material (poly{2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene} (PBTTT) as organic semiconductor layer, where addition of lactic acid to the aqueous solution induced anenzymatic reaction resulting in electron transfer causing a change in the surface potential of the sensing gate electrode. Reproduced under terms of theCC-BY license Ref. 106. 2025 Springer-Nature.040106-5© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWnanoarchitectonics has become increasingly important. In thefollowing sections, we will discuss the nanoarchitectonics oforganic semiconductor devices for bioprocesses applicationsfrom several perspectives.Controlling electron transfer, electronic states and electrondensity is a crucial aspect in the fabrication of advancedelectronic materials and devices. Certain biomaterials arecapable of precisely regulating the movement of electronsand protons under ambient conditions, suggesting theirpotential utility in the design and fabrication of next-generation electronic systems. A representative example isthe plating reaction, in which electrons are transferred amongsugars, reducing agents, and metal ions to form metallic thinfilms. In this review, we discuss strategies for fabricating andcontrolling advanced nanomaterials, thin films, and devicesthrough the use of biomolecules.3.1. Materials nanoarchitectonicsHere, we summarize recent advances in the synthesisand assembly of conducting polymers and organicsemiconductors that have been integrated into biopro-cesses. In particular, the former allows in vivo synthesis,which greatly facilitates their coupling with biologicalsystems.3.1.1. Bio-conjugated nanoarchitectonics. Amongvarious approaches to developing bioelectronic materials,polymeric semiconductors offer distinct advantages overtheir small-molecule counterparts, as they can be readilyprocessed into uniform thin films through techniques suchas spin coating. However, oxidative polymerization—com-monly employed for the synthesis of polymeric semicon-ductors and conducting polymers—often requires heavy-metal catalysts, which can limit their applicability due tometal-induced biotoxicity. In contrast, enzymatic oxidativepolymerization provides superior biocompatibility andenables highly selective and controllable polymer growthowing to the intrinsic reaction specificity of enzymes. Forexample, the peroxidase-mediated oxidation and polymer-ization of monomers containing 2,5-bis(2,3-dihydrothienoFig. 4. Examples of DNA sensor: (a) an ultrasensitive, label-free DNA detection method using a solution-gated graphene transistor functionalized withcarbon quantum dots, in which, upon hybridization with complementary ssDNA, double-stranded DNA is formed and subsequently detaches from thecarbon quantum dot surface, resulting in a Dirac voltage shift and a corresponding channel current. Reprinted with permission from Ref. 107. Copyright2022 American Chemical Society; (b) a solution-gated graphene transistor biosensor for the ultrasensitive and rapid quantitative detection of microRNA-21 (miRNA-21), an early-stage prostate cancer biomarker. Reproduced under terms of the CC-BY license Ref. 108. 2023 Wiley-VCH.040106-6© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEW[3,4-b][1,4]dioxin-5-yl)thiophene (ETE) have been re-ported as a nanoarchitectonics-based strategy for devel-oping in vivo device materials, as illustrated below.Building upon this concept, Strakosas, Berggren and co-workers reported a method to induce enzymatic polymeriza-tion using endogenous metabolites, enabling the formation offlexible and highly conductive organic polymer gels directlywithin target tissues [Fig. 6].112) They developed a complexprecursor system that contains an oxidase producing hy-drogen peroxide in vivo, a peroxidase catalyzing oxidativepolymerization, a water-soluble conjugated monomer, across-linked polyelectrolyte, and a surfactant. This hybridsystem successfully induced polymerization and subsequentgelation in vivo in living organisms such as zebrafish andleeches, resulting the direct formation of flexible, conductiveelectrodes compatible with neutral tissue. Unlikeconventional solid electrodes, this approach integrates bio-compatibility with dynamic adaptability, making it highlypromising for the development of implantable electronicdevices and neural stimulation technologies. Importantly, itenables the creation of organic electronic gels without rigidsubstrate materials, which are inherently incompatible withbiological tissues. The technology offers biocompatibilityand dynamic adaptability not achievable with conventionalsolid electrodes, highlighting its potential for implantablebioelectronics and neurostimulation. Moreover, it representsa nanoarchitectonics approach for establishing a seamlessinterface between biological environments and electronicmaterials.Similarly, expanding the concept of enzymatic in vivopolymerization to the plant kingdom, Stavrinidou et al.demonstrated that a conjugated oligomer called ETE‑S canFig. 5. Examples of protein sensor: (a) OECT-based biosensors upon antigen–antibody interactions, in which immobilization of the spike protein(antigen) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the gate surface enables the detection of SARS-CoV-2 immunoglobulinG (IgG) through antigen–antibody interactions. Reproduced under terms of the CC-BY license Ref. 109. 2021 AAAS; (b) a sensor for the detection ofsurvivin protein, a human gene product found in cancer cells, which enabled the detection of survivin protein at concentrations as low as 10 pg ml−1 inthe OECT electrolyte. Reprinted with permission from Ref. 110. Copyright 2021 Springer-Nature.040106-7© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWundergo in vivo polymerization into conductive polymerswithin plant vascular tissues through peroxidase‑ and hy-drogen peroxide‑mediated catalytic reactions.113) This ap-proach exploits intrinsic biological metabolic build conduc-tive structures in vivo, representing a nanoarchitectonicsstrategy for bridging living systems with electronic function-ality. In future, the precise design of molecular backbonesand side-chain structures may open new possibilities forcontrolling specific polymerization pathways within livingorganisms.Extending this idea further to the cellular and geneticlevel, a single-enzyme-mediated polymerization can alsobe designed using chemically modified monomers whosepolymerization is induced by enzymes expressed in specificcell types. This approach enables the chemical assembly offunctional materials within living cells, tissues, and organ-isms by targeting specific genes and exploiting their geneticinformation. Liu et al. integrated genetic engineering withpolymer chemistry to directly utilize complex cellulararchitectures for the in vivo synthesis of bioelectronicmaterials (Fig. 7).114) By inducing material synthesis ingenetically targeted cells, the polymerization proceeds withhigh precision and selectivity at the cellular level, allowingthe localized generation of functional materials withinbiological environments. Using this strategy, artificialenzymes expressed in specific neurons enabled thein vivo formation of conductive polymers within the neuraltissue of freely moving animals. In addition, by designinggenetically or anatomically targeted monomers and enzy-matic catalysts, and by tuning biochemical parameters suchas pH, light, and redox potential, it becomes possible toselectively trigger reactions within cells. This nanoarchi-tectonics concept provides a generalizable platform thatextends beyond oxidative polymerization, offering apromising route for constructing cell‑specific functionalstructures through controlled chemical synthesis.These examples demonstrate the in vivo construction ofconductive polymers aiming to integrate biological systemsand electronic devices at the materials level. Such intracel-lular nanoarchitectonics is expected to provide an effectiveapproach for developing direct bio-monitoring devices.3.1.2. Interfacial nanoarchitectonics. The above de-scribes innovative processes, such as the in vivo creationof conductive polymers, in great detail. However, nanoarch-itectonics processes can also be developed by building onexisting knowledge to induce innovative improvements tocommonly used techniques. For instance, useful devicesstructures can be realized, such as highly oriented thin filmsof polymer semiconductors. Relevant recent examples areshown below.As mentioned above, polymeric semiconductors canreadily be fabricated into thin films using methods such asspin coating. However, due to their strong intermolecularinteractions, they tend to aggregate easily, and high-tem-perature dissolution and processing are therefore oftenrequired. Furthermore, technologies for controlling theirmain-chain orientation are still under development. Incontrast, many biomolecules exhibit self-organizing beha-vior at room temperature at hydrophilic/hydrophobic inter-faces. For instance, molecular mobility is higher at air–liquidinterfaces than in the solid state because molecules areconfined to two-dimensional space, which facilitates orienta-tional control. We have reported a low-energy main-chainorientation technique that exploits air–liquid and hydro-philic/hydrophobic interfaces, which are commonly encoun-tered in the fabrication of biomimetic membranes.Ito et al. demonstrated that uniaxial orientation along thepolymer main-chain direction can be achieved using theFig. 6. A method to induce enzymatic polymerization using endogenous metabolites, enabling the formation of flexible and highly conductive organicpolymer gels directly within target tissues. Reprinted with permission from Ref. 112. Copyright 2023 AAAS.040106-8© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWLangmuir–Blodgett (LB) technique on a heated liquid sur-face (Fig. 8).115,116) This approach creates thermodynami-cally favorable conditions at the air–water interface, al-lowing nanoscale molecular aggregates to be manipulatedwith micrometer- to millimeter-scale dynamics. Althoughaqueous subphases are typically used, they are limited inboth usable temperature and compatible coating materials. Inthis study the aqueous subphase was replaced with ethyleneglycol, enabling the fabrication of ultrathin films at tempera-tures up to 100 °C. Ethylene glycol remains in a viscousliquid state over a wide temperature range, which allowedLB films of PBTTT, a benchmark semi-crystalline polymersemiconductor, at 100 °C. The resulting PBTTT LB filmsexhibited uniaxial backbone alignment and anisotropiccharge transport, yielding FETs with a turn-on voltage of0 V, a on/off ratio exceeding 106, and negligible hysteresis.These characteristics indicate that external factors such asresidual solvent, carrier trapping, and film inhomogeneityhave minimal impact. The high-temperature LB method thusenables precise control of polymer backbone orientation andcan be extended to a wide range of coating materials,including those that aggregate in water at room temperature,by selecting appropriate non‑aqueous subphases such asionic liquids and diols.More recently, Fujioka et al. reported a room‑temperatureprocess that aligns polymer main chain along the flow ofhydrophilic viscous liquid (Fig. 9).117) This approach mimicsthe interfacial self‑organization of biomolecules and offers apromising route for precise structure control of electronicfunctional materials using low-energy processes. Threepolymeric semiconductorsーPBTTT, (poly(4,4′-bis(2-buty-loctoxycarbonyl-[2,2′-bithiophene]-5,5-diyl)-alt-(2,2′-bithio-phene-5,5′-diyl)), (PDCBT), and poly(3,3′′-didodecyl-2,2″:5′,2′′:5′′,2′′′-quaterthiophene-5,5′′′-diyl) (PQT)—weretested by dispensing their solutions onto glycerol circulatingin a circular flow within a container, forming thin films at theair–liquid interface. To fabricate the films, a glass cylinderfilled with glycerol was rotated at 20 rpm within a circularcontainer. A droplet of PDCBT solution in a chloroform/1‑chloronaphthalene mixture (the high‑boiling solvent addedto slow evaporation) was deposited onto the flowing glycerolsurface along the cylinder’s rotation path. After solventevaporation (~5 min), ring‑shaped films with uniaxiallyaligned main chains were obtained around the cylinder,suppressing convection effects during drying.Polarized optical microscope and UV–vis spectroscopyconfirmed the macroscopic anisotropy and uniaxial main‑chainorientation of the PDCBT films. FET measurements revealedFig. 7. Genetically targeted chemical assembly of functional materials in cells; (a) enzyme-catalyzed functional polymerization in brain (top) andreaction of Apex2-mediated polymerization from precursor reagents containing aniline monomer-dimer mixture (bottom). Reprinted with permissionfrom Ref. 114. Copyright 2020 AAAS.040106-9© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWFig. 8. Fabrication of uniaxial orientation along the polymer main-chain direction using the Langmuir–Blodgett (LB) technique on a heated liquidsurface, allowing nanoscale molecular aggregates to be manipulated with micrometer- to millimeter-scale dynamics. Reprinted with permission fromRef. 115. Copyright 2020 American Chemical Society and Ref. 116. Copyright 2022 American Chemical Society.Fig. 9. A room‑temperature process that aligns polymer main chain along the flow of hydrophilic viscous liquid, where three polymericsemiconductors were tested by dispensing their solutions onto glycerol circulating in a circular flow within a container, forming thin films at the air–liquid interface.040106-10© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWsignificantly enhanced carrier transport along the flow direc-tion, with hole mobility in the channel‑parallel configurationreaching 4× that of spin‑coated films. Notably, the mobilitystable even after 34 d of air storage in the dark. This circularflow alignment method provides a simple, scalable approach tocontrol molecular orientation during solution processing,where convection often disrupts alignment. By optimizingflow path designs, the technique can be scaled up, enabling theproduction of highly aligned polymeric semiconductor thinfilms for a wide range of applications.These interfacial nanoarchitectonics techniques effectivelycontrol the orientation of polymeric semiconductor mole-cules, which tend to aggregate within thin films. In parti-cular, highly oriented organic semiconductor thin filmsenable the fabrication of anisotropic devices. Many biopro-cesses exhibit asymmetric, vectorial properties, such asunidirectional electron transport.118,119) Interfacial nanoarch-itectonics—such as the LB method described aboveーpro-vides a powerful methodology for fabricating organicsemiconductor thin films that are compatible with suchbiosystems and coupled to bioprocesses.3.2. Doping nanoarchitectonicsDoping is an essential process that enables the functionaloperation of organic semiconductors. The incorporation ofdopants into the structure of organic semiconductors can beviewed as a form of molecular-level nanoarchitectonics,since it involves precise control over molecular interactionsand charge transfer. Recently, bioprocesses have beenproposed as an innovative route for doping, allowing theprocedure to occur in aqueous environments under ambientconditions. To clarify the significance and underlyingmechanism of this approach, we will first describeconventional doping methods, followed by the discussionof bioprocess-based doping in a later section.3.2.1. Doping nanoarchitectonics, general. Doping oforganic semiconductors is an essential fabrication technique,as it modulates the charge carrier density within thesemiconductor and reduces contact resistance at metal-semiconductor interfaces. This technique is therefore widelyapplied in devices such as solar cells, thermoelectricmaterials, transistors, and organic light-emitting diodes(OLEDs). Representative examples are shown below.In recent years, molecular doping has been reported tosignificantly enhance the operational characteristics of or-ganic solar cells. Nugraha, Anthopoulos and co-workersachieved performance enhancement in state-of-the-art OPVsby converting the dicationic species diquat into its neutralform and employing it as an n-type dopant [Fig. 10(a)].120)EPR measurements confirmed the formation of free electronsin the PM6:Y6:PC71BM ternary blend. The PCE of ternarybulk heterojunction cells incorporating diquat increased from16.7% to 17.4%. These improvements are attributed toincreased absorption coefficients, balanced ambipolar trans-port, extended carrier lifetimes, and suppressed bimolecularrecombination. These findings highlight diquat as a promisingn-type dopant for realizing highly efficient stable OSCs.n-type doping of single-walled carbon nanotubes(SWCNTs) has also been reported. Because SWCNTs typi-cally exhibit p-type semiconductor behavior when exposed toair or oxygen, they are widely used as anodes in perovskitesolar cells (PSCs). Matsuo et al. proposed a simple molecularn-type doping strategy using organophosphorus compounds toenable SWCNTs to function as cathodes in inverted (p-i-n)PSCs (glass/ITO/PEDOT:PSS/MAPbI3/n-doped SWCNTs:Fig. 10. (a) Performance enhancement in state-of-the-art OPVs by converting the dicationic species diquat into its neutral form and employing it as ann-type dopant. Reprinted with permission from Ref. 120. Copyright 2025 American Chemical Society; (b) molecular n-type doping strategy usingorganophosphorus compounds to enable SWCNTs to function as cathodes in inverted (p-i-n) PSCs. Reprinted with permission from Ref. 121. Copyright2025 Royal Society of Chemistry.040106-11© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWPCBM) [Fig. 10(b)].121) Among the compounds tested, theaddition of 1,2-bis(diphenylphosphino)ethane (DPPE) to theSWCNT electrode increased the device efficiency from 5.1%to 8.03%. The improved stability was attributed to thehydrophobicity of the dopant, which also acted as a moisturescavenger, mitigating perovskite degradation. Overall, thesefindings indicate a promising avenue for the flexible andpractical implementation of SWCNTs as next-generationphotovoltaic electrodes.In thermoelectric materials, p-type doping examples havebeen demonstrated. Conducting polymer thin films, whichinherently possess structural disorder, exhibit complex elec-tronic, transport, and thermoelectric characteristics. Owing tothis disorder, the Seebeck coefficient and electrical conduc-tivity do not exhibit a clear maximum in thermoelectric powerfactor upon doping, in contrast to conventional inorganicsystems. However, Tanaka, Ito, Takenobu and co-workersdemonstrated that a semiconducting thiophene-based polymer(PBTTT) exhibits a distinct maximum in thermoelectricpower factor when subjected to wide-range carrier dopingvia an electrolyte gating technique using the ionic liquid N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluor-omethanesulfonyl)imide ([DEME][TFSI]).122) Figure 11(a)shows a schematic diagram of the experimental setup enablingsimultaneous measurement of the Seebeck coefficient andelectrical conductivity during carrier doping, together with aphotograph of the PBTTT thin-film transistor structure. Thepower facter maximum appeared near the insulator-to-metaltransition, as confirmed by the temperature dependence ofconductivity and magnetoresistance measurements. In themetallic regime, charge transport was found to follow theconventional Mott relation, indicating that structural disorderwas effectively suppressed. These findings provide importantphysical insights into doping nanoarchitectonics for perfor-mance tuning of conducting polymers toward high-efficiencypolymer-based thermoelectric devices for future energy har-vesting applications.To further optimize doping methods and develop betterdopants, it is essential to understand the effect of dopantcounterions on the charge transport and thermoelectricproperties of semiconducting SWCNT networks. Zaumseilet al. used ion-exchange doping to systematically vary thesize of the counterions in polymer-sorted, small- and large-diameters semiconducting SWCNT thin films, using AuCl3as the initial p-type dopant [Fig. 11(b)].123) They investigatedthe impact of ion size on conductivity, the Seebeck coeffi-cient, and the power factor. Larger anions were found tosignificantly increase electrical conductivity, and this effectwas more pronounced in small-diameter nanotubes than inlarge-diameter nanotubes. Meanwhile, the position of thepower-factor-versus-conductivity peak remained unchanged.Semiconducting SWCNT networks thus provide an idealFig. 11. (a) A schematic diagram of the experimental setup enabling simultaneous measurement of the Seebeck coefficient and electrical conductivityduring carrier doping, together with a photograph of the PBTTT thin-film transistor structure. Reprinted with permission from Ref. 122. Copyright 2020AAAS; (b) ion-exchange doping to systematically vary the size of the counterions in polymer-sorted, small- and large-diameters semiconductingSWCNT thin films, using AuCl3 as the initial p-type dopant. Reprinted with permission from Ref. 123. Copyright 2024 Wiley-VCH.040106-12© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWmodel system for investigating how different dopant counter-ions affect charge transport and thermoelectric properties indisordered percolating semiconductors such as conjugatedpolymers. These insights are expected to guide the develop-ment of dopants and doping strategies for improving thermo-electric materials.We next discuss an example of contact resistance reduc-tion between metals and OSCs. Schottky barriers at metal–OSC interfaces often cause non-ideal transfer characteristicsin the low drain-voltage regime of OFETs. Kang, Lee, andco-workers reduced the contact resistance in PBTTT-basedbottom-gate OFETs by selectively evaporating 2,3,5,6-tetra-fluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) nearthe contacts, enabling its solid-state diffusion (Fig. 12).124)UPS measurements confirmed successful p-type doping,with the Fermi-highest occupied molecular orbital(HOMO) offset decreasing from 0.87 eV to 0.26 eV. Post-doping optimization suppressed surface dopant diffusionwhile maintaining high conductivity near electrodes, nearlydoubling transistor current at comparable gate voltages. Thismolecular injection doping approach effectively addressescontact resistance issues and enables low-power organicelectronics.As a final example, we consider doping in OLEDs. Theapplication of doping in high-performance OLEDs is limitedby the challenge of p-type molecular doping of organicmaterials with high ionization energies. Reineke et al.demonstrated that hexacyanotrimethylenecyclopropane(CN6-CP), which has an electron affinity 0.6 eV higherthan that of F4-TCNQ, can be used as a p-type dopantwhen mixed with the hole-injection material 4,4′-cyclohex-ylidenebis[N,N-bis(4-methylphenyl)benzenamine](TAPC).125) To investigate the dopant’s function in devices,they fabricated green OLEDs with structure shown inFig. 13. Using CN6-CP-doped TAPC, a low driving voltageof 2.92 V at a practical luminance of 1000 cd m−2 and3.18 V at a current density of 10 mA cm−2 was achieved.These results demonstrate that dopant has great potential forfuture applications in organic optoelectronic devices, in-cluding both monochrome and white OLEDs.Given the many potential applications of doped organicsemiconductors, it would be highly desirable to performdoping under ambient conditions, such as in air or aqueoussolution.3.2.2. Proton-coupled electron transfer (PCET) drivennanoarchitectonics for aqueous doping. Among thedoping methods for organic semiconductors, chemicaldoping via redox reactions relies on electron transferbetween the semiconductor and dopant molecules.Conventional solution-based chemical doping requires inertatmospheres and organic solvents to prevent unwanted sidereactions with oxygen and water, hindering scalability. Sincecertain devices require chemical doping for optimal perfor-mance, doping method under ambient conditions are essen-tial for large-scale fabrication. Recently, Ishii, Yamashitaand co-workers achieved such doping through pH-controlledpreventing unwanted redox reactions with water/oxygen.126)This approach harnesses PCET—a bio-inspired mechanism—for precise doping control (Fig. 14). Below, we detailPCET principles, mechanisms, applications, and prospects.PCET represents a core mechanism in biological energyconversion and enzymatic reactions, involving the concertedor sequential transfer of protons and electrons. In biologicalsystems—operating under ambient aqueous conditions—PCET plays a critical role in photosynthesis, cellularrespiration, enzymatic catalysis, and ATP synthesis. ByFig. 12. Reduction of contact resistance in PBTTT-based bottom-gate OFETs by selectively evaporating 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodi-methane (F4-TCNQ) near the contacts, enabling its solid-state diffusion, where post-doping optimization suppressed surface dopant diffusion whilemaintaining high conductivity near electrodes, nearly doubling transistor current at comparable gate voltages. Reprinted with permission from Ref. 124.Copyright 2019 Wiley-VCH.040106-13© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWintegrating PCET into organic semiconductor chemistry, air-and aqueous-compatible chemical doping becomes feasible.A key advantage of PCET lies in its Nernstian response,enabling precise control of redox potentials via protonactivity—a parameter adjustable over more than 10 ordersof magnitude. In this paper’s system, they utilize the two-electron, two-proton PCET reactions of the benzoquinone/hydroquinone (BQ/HQ) redox couple to control p-typedoping efficiency in aqueous solution. Indeed, decreasingsolution pH systematically increases electrical conductivity,confirming effective doping.The assumed mechanism of this doping process isproposed as follows. Hole injection into the organic semi-conductor proceeds via the pH-dependent PCET reaction ofBQ/HQ. Dopant anions then intercalate into the organicsemiconductor thin film, compensating the injected holes.These processes occur either sequentially or concertedly,enabling anion species Y− doping into PBTTT films withoutcompromising crystallinity. The synergistic interplay be-tween PCET and anion intercalation allows optimization ofdoping efficiency, stability, and electronic properties throughrational dopant anion selection. Notably, conductivity mea-surements demonstrate highly efficient p-type doping onlywhen both BQ and dopant salts are present. PBTTT filmsachieved conductivities as high as ~180 S cm−1 whencombined with LiNFSI. Using large, non-nucleophilic anionsfurther enhances air-stability of the p-doped films.Doping with PCET has also been successfully applied toother systems. Rodríguez-Martínez et al. demonstrated thatPCET using BQ as the oxidant and lithium bis(trifluoro-methylsulfonyl)imide (Li-TFSI) as the counterion is highlysuitable for p-type doping of polymer-sorted semiconductingSWCNT networks (Fig. 15).127) The doping level can beprecisely tuned by pH, enabling optimization to the powerfactor peak position. For narrow-bandgap SWCNTs, PCETdoping achieves thermoelectric power factors equivalent toconventional methods. Moreover, PCET-doped SWNTsexhibit superior long-term stability, maintaining electricalconductivity for at least 5 d in air—significantly outper-forming three other methods, including AuCl3-based ion-exchange doping. These results confirm PCET as a keytechnique for p-type doping of flexible, high-performancesemiconducting SWNT networks in thermoelectric applica-tions.This PCET-based chemical doping method offers unpre-cedented controllability, stability, scalability, and versatilityacross diverse structures through simple solution processing.It unlocks diverse possibilities for advanced organic semi-conductor devices. The demonstrated PCET route willaccelerate manufacturing of high-performance, reliable de-vices, including sensors and bioelectronics. Compared toconventional vacuum- or inert-atmosphere-based methods inorganic solvents, this doping nanoarchitectonics approachexhibits superior scalability, stability, and tunability. As aroom-temperature semiconductor process and platform forbiomolecular electronics, it holds immense potential fornext-generation flexible electronics and beyond.3.2.3. Bio-pathway nanoarchitectonics for sugarredox driven doping. For n-type chemical doping, theHOMO of the reductant must be shallower than thesemiconductor’s lowest unoccupied molecular orbital(~−4.0 eV versus vacuum).128) However, shallow-HOMOreductants are readily deactivated by dissolved oxygen (O2:−5.26 eV versus vacuum),129) making n-type doping morechallenging than p-type. While strong, moderately stable n-type doping has been achieved in gloveboxes using dimerdopants,130) catalytic reactions,131) and ion-exchangemethods,132,133) ambient n-type doping remains unreported.Recently, Ohashi, Yamashita and co-workers achieved n-type doping of organic semiconductors using a biochemicalpathway (Fig. 16).134) This study employs a reductant withsufficient reducing power and stability in air, paired withredox mediators to efficiently extract electrons. Redoxreactions mediated by such mediators are ubiquitous inbiology. Bio-mimetic strategies thus enables redox potentialcontrol while suppressing oxygen-induced degradation.A polymer thin film of PNDI(2HD)T—comprisingnaphthalene-1,4:5,8-bis(dicarboximide) (NDI) with branchedalkyl chains and thiophene units—employed as the organicsemiconductor. This polymer semiconductor thin film wasthen immersed in an aqueous doping solution containingfructose, flavin mononucleotide (FMN) and bulky molecularFig. 13. Investigation on the dopant’s function in devices using green OLEDs. Reprinted with permission from Ref. 125. Copyright 2019 AmericanChemical Society.040106-14© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWcations. During this process, electrons were transferredfrom the fructose to the FMN, and then from the FMN tothe organic semiconductor thin film. These electrons werecompensated for by introducing bulky molecular cationsinto the thin film, which were selected to improve thestability and transport properties of the carriers. Thisprocess increased the conductivity of the thin film fromless than 10−9 S cm−1 to 4× 10−4 S cm−1, confirmingsuccessful n-type doping. While fructose provides environ-mental stability through slow redox kinetics, its reducingcapability is limited. Using an FMN redox mediatoraccelerated the redox reaction rate and achieves n-typedoping. The doped organic semiconductor thin filmsexhibited conductivities exceeding 10−3 S cm−1 at roomtemperature, as well as long lifetimes in air. Owing to thethermal stability of the material, facile thin-film encapsula-tion realized a lifetime of 25 h at 100 °C in air, which isremarkable considering the shallow IP of around 3.8 eV forthe doped PNDI(2HD)T.Solution processing of organic semiconductors enablesconvenient fabrication of doped thin films, paving the wayfor printed electronics. This study demonstrates that n-typedoping—previously confined to glovebox conditions—cannow be achieved under ambient conditions using aqueoussolutions. These results suggest that room-temperature p-and n-type doping will enable advanced organic devices forthermoelectric generators, and stable low-work-functionelectron transport layers. Moreover, the observed biomole-cule-semiconductor electron transfer opens up new avenuesfor energy storage, transfer, and conversion.This system represents a breakthrough by achieving n-typedoping of organic semiconductors under ambient aqueousconditions. It is equally groundbreaking by incorporatingbiologically ubiquitous processes, such as sugar redoxFig. 14. Doping of organic semiconductor films through proton-coupled electron transfer (PCET) in which the two-electron, two-proton PCETreactions of the benzoquinone/hydroquinone (BQ/HQ) redox couple to control p-type doping efficiency in aqueous solution.Fig. 15. PCET-based doping of polymer-sorted semiconducting SWCNT networks using BQ as the oxidant and lithium bis(trifluoromethylsulfonyl)imide (Li-TFSI) as the counterion. Reproduced under terms of the CC-BY license Ref. 127. 2025 Wiley-VCH.040106-15© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWreactions and coenzyme mediators. Continued progresscould enable seamless integration of any bioprocess intoorganic semiconductor devices.3.3. Natural molecules for electrode work functionengineering and device stabilizationBiomolecules have also been explored as functional compo-nents for improving the stability and environmental compat-ibility of organic semiconductor devices. For example,Akaike et al. reported that the adsorption of caffeic acid, apolar phenylpropanoid biosynthesized by plants, universallyincreases the work function of metal electrodes.135) Theformation of a dipole layer arising from the orientedadsorption of caffeic acid molecules leads to a work functionincrease of up to 0.7 eV, enabling effective tuning of the holeinjection barrier in organic electronic devices. As a result,monolayer devices incorporating a caffeic acid interlayerexhibited hole injection currents that were 101–102 largerunder forward bias. These results highlight the potential ofnaturally occurring molecules as interfacial modifiers forcontrolling the electronic properties of organic semicon-ductor devices.Biomolecules can also play an important role in stabilizingair-sensitive organic semiconductors. The development ofn-type organic semiconductors has long been hindered bytheir susceptibility to degradation by oxygen and water. Li,Hu and co-workers demonstrated that vitamin C can actas an effective stabilizing agent for n-type organicsemiconductors.136) Vitamin C functions as a reactiveoxygen species scavenger through a cascade process invol-ving sacrificial oxidation and triplet quenching, therebysuppressing oxidative damage and reducing electron trap-ping. When applied to OFETs, this strategy significantlyimproved both device performance and operational stability(Fig. 17). Such bio-inspired stabilization strategies mayprovide a general route for improving the stability of awide range of organic electronic materials, including con-ducting polymers, light-emitting materials, and other emer-ging semiconductors.These examples demonstrate that naturally derived mole-cules can serve not only as environmentally benign compo-nents but also as functional elements for controlling elec-tronic processes in organic devices. The incorporation ofbiomolecules into organic semiconductor systems may there-fore contribute to the development of sustainable andbiocompatible electronic technologies.4. Future perspectivesDrawing on the concept of nanoarchitectonics—the con-struction of functional systems from atoms and molecules—this review highlights recent advances in integrating organicsemiconductors with bioprocesses. Although research in thisarea remains relatively young, the examples discussed heredemonstrate the considerable potential of organic semicon-ductors to interact with biomolecular systems and to serve asplatforms for bio-integrated electronic devices.Biosensors represent a particularly important intersectionbetween organic semiconductor devices and biologicalprocesses. Organic semiconductors have been shown todetect a wide range of biomolecules, from small biomole-cules to large biomacromolecules, illustrating their versati-lity as sensing platforms. In addition, strategies such as theformation of conducting polymers within living organismsprovide a promising route toward direct integration ofbiological systems with electronic functionality. Interfacialnanoarchitectonics, including improved LB approaches andcontrolled molecular alignment in thin films, offers powerfultools for constructing well-defined organic semiconductorstructures compatible with biological environments.Doping remains a central process for enabling the func-tionality of organic semiconductors. However, conventionalchemical doping often requires inert atmospheres andorganic solvents, limiting practical scalability. Bio-inspiredapproaches offer attractive alternatives. Processes such asPCET, which are ubiquitous in biological energy conversionsystems, may enable efficient p-type doping under ambientor aqueous conditions. Similarly, bio-based strategies for n-type doping, including sugar which is stable reducing agentsin air and redox mediation, demonstrate how biologicalconcepts can expand the operational environment of organicsemiconductors.The combination of organic semiconductors with biopro-cesses opens new opportunities for applications ranging frombiosensing to wearable and implantable electronics. Owingto their mechanical flexibility, light weight, andFig. 16. A biochemical pathway of n-type doping of organic semiconductors using flavin mononucleotide (FMN), where electrons are transferredfrom the fructose to the FMN, then from the FMN to the organic semiconductor thin film, and electrons were compensated for by introducing bulkymolecular cations into the thin film.040106-16© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWbiocompatibility, organic semiconductor devices are wellsuited for seamless integration with biological interfaces. Inthe context of an increasingly connected IoT society, suchdevices could function as low-cost, flexible sensors capableof continuous physiological monitoring in healthcare anddaily life.Ultimately, the precise control over nanoscale structureswill be essential for realizing the full potential of thesesystems. Highly controlled molecular structures not onlygive rise to biological functions but also suppress theformation of trap states, which pose a critical challenge tothe practical implementation of organic semiconductordevices. In this context, nanoarchitectonics provides apowerful framework for the design and application of next-generation organic semiconductor biointerfaces. Continuedexploration at the intersection of materials science, electro-nics, and biology is expected to drive the development ofadvanced organic semiconductor biodevices with significanttechnological and societal impact.If we further consider key real-world implementationchallenges in practical usages, more fundamental mattersbecomes crucial. It is essential to focus on improvingfundamental performance tailored to practical applications,such as long-term and operational stability, resistance tovarious environments—including underwater conditions—and cost-effectiveness that allows for single-use disposal.For example, steady researches are underway on topics suchas the selection of organic semiconductors and dopants withappropriate film constructions to achieve long-termstability137) and operational stability.138) Furthermore, bydeveloping devices that operate at the single-molecule-layerlevel, the amount of material used can be drastically reduced,thereby alleviating cost concerns. In short, while pursuingcutting-edge research is important, thoroughly investigatingfundamental aspects such as stability may be the majorchallenge that paves the way for realistic applications.AcknowledgmentsThis work was supported in part by JSPS KAKENHI grants(Nos. JP23H05459, JP25H00898) and JST FOREST(JPMJFR236R).1) G. Povie, Y. Segawa, T. Nishihara, Y. Miyauchi, and K. Itami, Science356, 172 (2017).2) M. Sugiyama, M. Akiyama, Y. Yonezawa, K. Komaguchi, M. Higashi,K. Nozaki, and T. Okazoe, Science 377, 756 (2022).3) T. Mita, Bull. Chem. Soc. Jpn. 98, uoaf028 (2025).4) H. Oguri, Bull. Chem. Soc. Jpn. 98, uoaf036 (2025).5) T. Nakamura et al., Nat. Commun. 11, 3008 (2020).6) X.-L. Pei, P. Zhao, H. Ube, Z. Lei, M. Ehara, and M. Shionoya, Nat.Commun. 15, 5024 (2024).7) S. Yasumura and K. Shimizu, Bull. Chem. Soc. Jpn. 98, uoaf080(2025).8) M. Han, T. Nagaura, J. Kim, S. M. Alshehri, T. Ahamad, Y. Bando,A. Alowasheeir, Y. Asakura, and Y. Yamauchi, Bull. Chem. Soc. 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Graduatedfrom the Department of Pure and AppliedChemistry, Faculty of Science and Technology,Tokyo University of Science in 2023.Completed the Master’s program in Departmentof Pure and Applied Chemistry at the GraduateSchool of Science and Technology, TokyoUniversity of Science, in 2025. Currently pur-suing a Ph.D. at the same graduate school,conducting research on doping methods for n-type organic semiconductors.Linawati Sutrisno received her Ph.D. degree in2022 from University of Tsukuba. She began herresearch career as a postdoctoral researcher at theNational Institute for Materials Science (NIMS) in2022. After her postdoctoral work at NIMS, shecontinued her research as a JSPS Research Fellowand currently works as an independent researchfellow at International Center for YoungScientists (ICYS). Her research interests includein vitro imaging technologies aimed at developingstrategies for cancer treatment and tissue regen-eration, as well as the development of 3D porousscaffolds for bone, adipose, and skin tissue regeneration.Yu Yamashita received his Ph.D. in Sciencefrom the University of Tokyo in 2019. He iscurrently a senior researcher at the NationalInstitute for Materials Science (NIMS), Japan, andan associate professor at the University of Tokyo.His research focuses on chemical doping ofmolecular semiconductors, carrier transport me-chanisms, and structure–property relationships inorganic molecular thin films, as well as theirapplications in electronic devices such as diodes,transistors, and electrochemical transistors.Katsuhiko Ariga received his Ph.D. from theTokyo Institute of Technology in 1990.Following research positions at Tokyo Instituteof Technology, University of Texas at Austin,JST Supermolecule Project, Nara Institute ofScience and Technology, and JST NanospaceProject, he joined National Institute forMaterials Science (NIMS) in 2004. He iscurrently the leader of the Supermolecule Groupand a senior scientist with special missions atResearch Center for MaterialsNanoarchitectonics (MANA) at NIMS. He isalso a professor at University of Tokyo. His primary research interests lie inexciting and innovative topics in supramolecular chemistry, interfacialscience, thin film technology, and nanoarchitectonics.040106-19© 2026 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 19, 040106 (2026) APEX REVIEWhttps://doi.org/10.1126/sciadv.abg8387https://doi.org/10.1007/s00604-021-04947-2https://doi.org/10.1007/s00604-021-04947-2https://doi.org/10.1002/adma.201703787https://doi.org/10.1002/adma.201703787https://doi.org/10.1126/science.adc9998https://doi.org/10.1039/D0TB00212Ghttps://doi.org/10.1126/science.aay4866https://doi.org/10.1021/acsami.0c18349https://doi.org/10.1021/acs.langmuir.1c02596https://doi.org/10.1021/acsami.4c20510https://doi.org/10.1021/acsami.4c20510https://doi.org/10.1038/355796a0https://doi.org/10.1038/nature03661https://doi.org/10.1021/acsenergylett.0c01949https://doi.org/10.1039/D5TA06786Chttps://doi.org/10.1039/D5TA06786Chttps://doi.org/10.1126/sciadv.aay8065https://doi.org/10.1002/adma.202404554https://doi.org/10.1002/adma.202404554https://doi.org/10.1002/adma.201806697https://doi.org/10.1021/acsami.8b21865https://doi.org/10.1021/acsami.8b21865https://doi.org/10.1038/s41586-023-06504-8https://doi.org/10.1038/s41586-023-06504-8https://doi.org/10.1002/aelm.202400817https://doi.org/10.1002/aelm.202400817https://doi.org/10.1002/adma.201001402https://doi.org/10.1016/S0379-6779(97)80097-5https://doi.org/10.1021/acs.accounts.1c00612https://doi.org/10.1021/acs.accounts.1c00612https://doi.org/10.1038/s41586-021-03942-0https://doi.org/10.1038/s43246-024-00507-2https://doi.org/10.1038/s41467-024-49208-xhttps://doi.org/10.1002/smll.202509278https://doi.org/10.1002/smll.202509278https://doi.org/10.1002/admi.202201800https://doi.org/10.1002/admi.202201800https://doi.org/10.1038/s41563-024-01933-whttps://doi.org/10.1039/D4TC01406Ehttps://doi.org/10.1039/D4TC01406Ehttps://doi.org/10.1038/s44431-025-00014-5https://doi.org/10.1038/s44431-025-00014-5 1. Introduction 2. Usage examples of organic semiconductor device for biology: biosensor 2.1. Biosensor for small molecular gest 2.1.1. Glucose sensor 2.1.2. Lactate sensor 2.2. Sensor for biopolymer 2.2.1. DNA/RNA sensor 2.2.2. Protein sensor 3. Nanoarchitectonics for bio-relevant organic semiconductor devices 3.1. Materials nanoarchitectonics 3.1.1. Bio-conjugated nanoarchitectonics 3.1.2. Interfacial nanoarchitectonics 3.2. Doping nanoarchitectonics 3.2.1. Doping nanoarchitectonics, general 3.2.2. Proton-coupled electron transfer (PCET) driven nanoarchitectonics for aqueous doping 3.2.3. Bio-pathway nanoarchitectonics for sugar redox driven doping 3.3. Natural molecules for electrode work function engineering and device stabilization 4. Future perspectives Acknowledgments