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[Nanami Fujisawa](https://orcid.org/0000-0002-8894-1790), [Mitsuhiro Ebara](https://orcid.org/0000-0002-7906-0350), James J. Lai

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[Magnetic Induction Heating Enables On-Demand Drug Release via Diels–Alder Polymeric Nanocarriers](https://mdr.nims.go.jp/datasets/153c0595-eb66-4dba-84f2-9de63b066429)

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Magnetic Induction Heating Enables On-Demand Drug Release via Diels–Alder Polymeric NanocarriersMagnetic Induction Heating Enables On-Demand Drug Release viaDiels−Alder Polymeric NanocarriersNanami Fujisawa, Mitsuhiro Ebara,* and James J. Lai*Cite This: Biomacromolecules 2025, 26, 7265−7274 Read OnlineACCESS Metrics & More Article Recommendations *sı Supporting InformationABSTRACT: As a stimulus-responsive drug release system, wedeveloped Diels−Alder (DA) induction-activated magnetic nanoparticles(DiMaN). Functionalization of polymer-coated magnetic nanoparticles(mNPs) with drugs via thermoreversible DA coupling enabled releasethrough retro-Diels−Alder (rDA) cleavage upon heating. The (pDMAm-co-pFMA)-b-pAAc polymer supported mNP formation and drug binding.DA coupling with maleimide-functionalized drugs was verified by 1HNMR, showing distinct exo (3.23 ppm) and endo (3.48 ppm) signalsafter 72 h at 37 °C. Approximately 70% release was observed within 15min at 80 °C, while the complex maintained stability at 40 °C. Thesuperparamagnetic mNPs generated localized heating under analternating current magnetic field (192 kHz, 480 A), raising the solution temperature by 6 °C within 5 min. The biotin-maleimidecomplex demonstrated higher release by rDA from furan-containing mNPs (approximately 150 μM) compared to the control group(approximately 103 μM). These results highlight DiMaN as a promising platform for magnetic-controlled, on-demand drug release.1. INTRODUCTIONInfusion pumps are widely used for the controlled subcuta-neous or intravenous administration of drugs, particularly ininsulin and opioid treatments.1 These devices enable preciseand programmable drug delivery, allowing for home-basedtherapy and long-term medication management.2,3 The U.S.Food and Drug Administration (FDA) has issued alertsregarding the risks of over- or underdosing, drug leakage, andsystem malfunctions associated with infusion pumps.4 Toensure patient safety, accurate programming, precise dosagecontrol, and proper user training have been emphasized ascritical factors in the effective use of these devices.5,6 Anothermajor limitation of infusion pumps is their reliance oncontinuous drug exposure, which may not always align withthe body’s natural biological rhythms or optimal drug efficacywindows.7 In some cases, treatments benefit from precisespatiotemporal control over drug activation, such as aligningdrug release with the circadian cycle or responding to specificphysiological conditions.8Given these challenges, there is a need to develop safer,more reliable, and externally controllable drug delivery systemsthat minimize user error while maintaining precise therapeuticcontrol.9 One promising approach is the use of externallytriggered, on-demand drug release platforms, which allow forlocalized drug activation in response to external stimuli such astemperature, light, or magnetic fields.Ideally, an on-demand drug delivery system would notrequire constant external intervention but instead utilize animplantable material capable of externally triggered, preciselycontrolled drug release.10 Spatial control of drug therapyrequires active selection of the treatment site, which can beachieved with locally implanted systems.11 Additionally, an on-demand drug release mechanism would allow precise temporalcontrol over drug administration at any given time.5 Severaltemperature-responsive drug release systems have beeninvestigated, including those based on temperature-sensitivepolymers (e.g., poly(N-isopropylacrylamide), pNIPAAm),12hydrogen bonding (e.g., DNA),13 and disulfide bonding.14However, physical phase transitions alone may not providesufficient accuracy, as drugs may still be released at lowertemperatures.15 Drug release systems that respond to pHchanges have also been developed, often designed to takeadvantage of the tumor microenvironment.16 While suchapproaches can be effective, they are not ideal for conditionslike epilepsy, diabetes, or cancers requiring synchronizationwith circadian rhythms.17,18 Among potential control mecha-nisms, temperature stands out as a promising trigger because itremains stable at approximately 37 °C in the human body.Consequently, if temperature changes can be externallyinduced, drug release could be controlled with high precision.For example, gold nanoparticles and near-infrared (NIR) lighthave been used as heat sources to trigger drug release;13Received: March 5, 2025Revised: October 14, 2025Accepted: October 15, 2025Published: October 23, 2025Articlepubs.acs.org/Biomac© 2025 The Authors. Published byAmerican Chemical Society7265https://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−7274This article is licensed under CC-BY 4.0Downloaded via NATL INST FOR MATLS SCIENCE (NIMS) on November 19, 2025 at 05:43:09 (UTC).See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.https://pubs.acs.org/action/doSearch?field1=Contrib&text1="Nanami+Fujisawa"&field2=AllField&text2=&publication=&accessType=allContent&Earliest=&ref=pdfhttps://pubs.acs.org/action/doSearch?field1=Contrib&text1="Mitsuhiro+Ebara"&field2=AllField&text2=&publication=&accessType=allContent&Earliest=&ref=pdfhttps://pubs.acs.org/action/doSearch?field1=Contrib&text1="James+J.+Lai"&field2=AllField&text2=&publication=&accessType=allContent&Earliest=&ref=pdfhttps://pubs.acs.org/action/showCitFormats?doi=10.1021/acs.biomac.5c00321&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?goto=articleMetrics&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?goto=recommendations&?ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?goto=supporting-info&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=tgr1&ref=pdfhttps://pubs.acs.org/toc/bomaf6/26/11?ref=pdfhttps://pubs.acs.org/toc/bomaf6/26/11?ref=pdfhttps://pubs.acs.org/toc/bomaf6/26/11?ref=pdfhttps://pubs.acs.org/toc/bomaf6/26/11?ref=pdfpubs.acs.org/Biomac?ref=pdfhttps://pubs.acs.org?ref=pdfhttps://pubs.acs.org?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-ashttps://pubs.acs.org/Biomac?ref=pdfhttps://pubs.acs.org/Biomac?ref=pdfhttps://acsopenscience.org/researchers/open-access/https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/however, these approaches face limitations when targetingdeep tissues due to the poor penetration of external stimuli.In this study, we hypothesize that DiMaN (Diels−Alderinduction-activated magnetic nanoparticles), magnetic nano-particles (mNPs) decorated with polymers containing furangroups, can serve as a temperature-responsive on-demand drugrelease system when exposed to an AC magnetic field (Scheme1). DiMaN incorporates drug molecules with maleimidederivatives by conjugating to the polymer’s furan groups viathe Diels−Alder (DA) reaction, allowing for stable attach-ment.19 Upon exposure to an AC magnetic field, the magneticcore of the nanoparticles would generate localized heat,20triggering retro-Diels−Alder (rDA) cleavage to release theconjugated drug molecules.21 To test this hypothesis, wesynthesized a diblock copolymer, poly(dimethylacrylamide-co-furfuryl methacrylate)-block-poly(acrylic acid), (pDMAm-co-pFMA)-b-pAAc, which serves as a template for mNP synthesis.The pAAc block coordinates iron cations via carboxylatecomplexation, facilitating the formation of iron oxide particlecores,22 while the pDMAm-co-pFMA block maintains theresulting particles’ colloidal stability. Beyond nanoparticlecharacterization, their inductive heating behavior was con-firmed under an AC magnetic field. The model drug moleculeswith a maleimide derivative were conjugated to the particle byreacting with the furan group of the pDMAm-co-pFMA blockvia DA reaction. Then, the conjugated drug molecules werereleased by cleaving the thermoreversible covalent bond via theheat-induced rDA reaction using the iron oxide mNPs as a heatsource. DiMaN can potentially provide a novel, externallycontrolled drug delivery system, combining magnetothermalactivation and temperature-responsive polymer chemistry foron-demand control of drug release and highly selective andprecise therapeutic applications.2. MATERIALS AND METHODS2.1. Materials. Azobis(isobutyronitrile) (AIBN), deuterium oxide(99.8%, for nuclear magnetic resonance (NMR)), lithium chloride(LiCl), and dimethylformamide (DMF) were purchased fromFUJIFILM Wako Pure Chemical Corporation (Osaka, Japan). Acrylicacid (AAc), N,N-dimethylacrylamide (DMAm), NHS-PEG2-malei-mide (NHS-PEG2-MAL, >98.0%), and 4-cyano-4-[[(dodecyl thio)-carbonothioyl]thio]pentanoic acid (CTA) were purchased fromTokyo Chemical Industry Co., Ltd. (Tokyo, Japan). Ultrapuredistilled Milli-Q water (Merck, Darmstadt, Germany) was used inthis study. Furfuryl methacrylate (FMA), iron(II) chloride tetrahy-drate, iron(III) chloride hexahydrate, and ammonia solution (28% inwater) and biotin-PEG3-MAL were purchased from Sigma-Aldrich(MO, USA). The monomethyl ether hydroquinone inhibitors�thatis, FMA, AAc, and DMF�were removed by passing them through analumina oxide column before use.2.2. Block Copolymer Synthesis. For the homopolymer ofpDMAm150 (without the furan group), 4.00 g (40.351 mmol) ofDMAm was added; for the copolymer with the furan group ofp(DMAm145-co-FMA5), 3.781 g (38.146 mmol) of DMAm and0.2186 g (1.315 mmol) of FMA were added in each 20 mL samplebin. Moreover, 0.1086 g (0.269 mmol) of CTA reagent (the degree ofpolymerization was 150), 0.0044 g (0.027 mmol) of AIBN (10 wt %versus CTA), and 6.0 mL (30 wt %) of DMF were added in each binand vortexed well. Each sample was sealed with a rubber cup (14/20joints, Precision Seal rubber septa, Sigma−Aldrich) and a parafilm.Each monomer solution was purged with N2 gas for 20 min. Thesamples were then polymerized at 70 °C for 4 h; the polymerizationwas stopped by opening the rubber cup. For polymer purification, thereaction solution was added with enough space in each 3.5k molecularweight cutoff (MWCO) dialysis membrane and dialyzed against 2.0 Lof methanol, after which the dialysis solvent was exchanged using 2.0L of distilled water, the distilled water being exchanged three times.After polymer purification by dialysis, the polymer solution was addedto each 120 mL sample bin, prefrozen using liquid N2, and thenlyophilized (FDL-2000, Tokyo Rikakikai Co., Ltd., Tokyo, Japan) for3 days to obtain a yellowish-white powder. The polymers obtained inthis study were then used as macro-CTAs (mCTA) in the blockcopolymers. Next, 1H NMR spectroscopy at 400 MHz (JEOL Ltd.,Tokyo, Japan) was used to confirm the polymer structures bydissolving the polymer in D2O at a concentration of 10.0 mg mL−1.The molecular weight was determined using gel permeationchromatography (GPC; Nexera 40, Shimadzu Corporation, Kyoto,Japan). The mobile phase was 10 wt % LiCl in DMF at 40 °C, and theelution peaks were detected using an RI detector (Shodex RI-501,Resonac Corporation, Tokyo, Japan). Finally, the Mn, Mw, andpolydispersity index (PDI) were calculated using poly(methylmethacrylate) (PMMA) standards.2.3. Synthesis of Block Copolymer p(DMAm-co-FMA)-b-pAAc. For polymerization with acrylic acid (AAc), pDMAm150-b-pAAc20, and p(DMAm145-co-FMA5)-co-pAAc20, 2.00 g (0.118 mmol)of each mCTA (pDMAm150 and p(DMAm145-co-FMA5)) was addedto the 20 mL samples. A total of 0.17 g (2.360 mmol) of AAc (degreeof polymerization = 20), 1.93 mg (0.012 mmol) of AIBN (10 wt %versus mCTA), and 17.36 mL of DMF (10 wt % versus the totalreactant mass) were added to each bin and vortexed thoroughly. Eachsample was sealed using a rubber cup and parafilm. Each monomersolution was purged with N2 gas for 20 min. The samples were thenpolymerized at 70 °C for 4 h; the polymerization was stopped byopening the rubber cup. To purify the polymers, sufficient space wasadded to the reaction solution in each 3.5 kDa MWCO dialysismembrane and dialyzed against 2.0 L of methanol, after which thedialysis solvent was exchanged using 2.0 L of distilled water, thedistilled water being exchanged three times. After dialysis, the purifiedpolymer solution was added to each 120 mL sample bin, prefrozenusing liquid N2, and then lyophilized for 3 days to obtain a yellowish-white powder.2.4. Synthesis of Magnetic Nanoparticles. For the synthesis ofmNPs using the polymer as a template, synthesized block copolymers1.25, 2.5, 5, 10, and 20 times the amount of iron(II) chlorideScheme 1. Schematic Diagram to Illustrate the Formation of Polymer-Templated mNPsaaMNPs decorated with (pDMAm-co-pFMA) can introduce drug molecules by the DA reaction. When an AC magnetic field is applied to theDiMaN, the drug molecules are released by exotherm of the mNPs, triggering the rDA reaction.Biomacromolecules pubs.acs.org/Biomac Articlehttps://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−72747266https://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=sch1&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=sch1&ref=pdfpubs.acs.org/Biomac?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-astetrahydrate (FeCl2·4H2O):iron(III) chloride hexahydrate (FeCl3·6H2O) (these being in a 1:2 ratio) were added to the blockcopolymer carboxylic acid. Specifically, FeCl2·4H2O and FeCl3·6H2Owere dissolved in Milli-Q water in advance at concentrations of0.1856 and 0.3712 M, respectively. The block copolymerspDMAm150-co-pAAc20 and p(DMAm145-co-FMA5)-b-pAAc20 werealso dissolved in Milli-Q water at concentrations of 50.0 mg mL−1each. The aqueous iron chloride solutions, aqueous polymer solutions,and Milli-Q water used for the mNP synthesis were purged using N2gas. Then, 50.0 μL of the polymer solution was added to each 1.5 mLEppendorf tube and mixed well. An iron chloride solution was addedto each volume, as shown in the table (Figure S1) and incubated for30 min. After incubation, 10 μL of the ammonia solution (28% inwater) was added and mixed well before being incubated for 30 minagain. The color of the solution changed from transparent to lightbrown. After 30 min at 25 °C, the solution was filtered with a 0.22 μmpoly(vinylidene difluoride) (PVDF) syringe filter. The mNPs in thefiltrate were purified via size exclusion chromatography (SEC)performed with SEC beads (Sepharose CL-4B, Cytiva, Tokyo,Japan) by gravity chromatography with Econo-Pac chromatographycolumns (Bio-Rad Laboratories, Inc., CA, US). Each 0.5 mL of elutedmNP fraction was collected using a 1.5 mL Eppendorf tube andmeasured each fraction component at 310 (CTA) and 500 (mNPs)nm by a NanoDrop Onec (Thermo Fisher Scientific, Inc., MA, US).Similarly, fourier-transform infrared spectroscopy (FT-IR; IRAffinity-1s, Shimadzu Corporation, Kyoto, Japan) was used to evaluate thecomposition of polymers and mNPs. Dry polymer powders and drymNPswere evaluated by attenuated total reflection FT-IR (ATR-FT-IR) method. To estimate the amount of polymer contained in mNPs,mg of eachmNPs (Fe:COOH ratio of 1.25:1, 2.5:1, 5:1, 10:1 and20:1) sample wa scaled, then change in mass was measured bydifferential thermal analysis-thermogravimetry (TG-DTA; TG-DTA6200, Seiko Instruments Inc., Chiba, Japan) when the temper-ature was increased from 25 °C to 550 °C with the increase rate at 10°C min-1. The weight reduction rate was calculated with the pre-measurement weight set as 100%. Hydrodynamic diameter measure-ments were performed using an ELSZ-2000 instrument (OtsukaElectronics Co., Ltd., Osaka, Japan). A high-power semiconductorlaser was used as the incident beam. After the concentration of mNPs(Fe:COOH ratio of 20:1) was adjusted to a level in the measurablerange with Milli-Q water, at each layer number, filtered by a 0.45 μmpore size, 13 mm-diameter polytetrafluoroethylene syringe filters(Membrane Solutions, LLC, WA, USA) then added the solution indisposable cuvettes. These samples were used for the particle sizemeasurements at 25 °C. The zeta potential was measured using astandard cell unit (Otsuka Electronics Co., Ltd., Osaka, Japan).Additionally, TEM images of the particles were taken to obtain theirappearance. For sample preparation, a sufficiently diluted particledispersion solution was prepared to obtain an image with well-dispersed particles. Two microliters of the particle dispersion solutionwere dispensed onto the carbon support film of the TEM grid (HRC-C10 STEM Cu100P, Okenshoji Co., Ltd., Tokyo, Japan) and thewater was dried. To prevent particle agglomeration due to rapid waterevaporation, the grid was left overnight in a refrigerator with a dampKimwipe to allow the water to evaporate slowly, yielding a samplesuitable for TEM imaging. TEM observation was performed by TalosF200X G2 (Thermo Fisher Scientific Inc., MA, US). TEM imageswere acquired at an accelerating voltage of 80 kV. For elementalmapping, scanning transmission electron microscopy (STEM) imageswere acquired with energy dispersive X-ray spectroscopy (EDS) bySuper-X.2.5. Heat Generation Behavior. The heating profiles of thefreeze-dried mNPs were investigated by applying an AC magneticfield. Polymer-coated mNPs were collected by lyophilization. Thesample was placed in the middle of a copper coil and exposed to anAC magnetic field at 192 kHz and 480 A using a HOSHOT2instrument (Alonics Co., Ltd., Tokyo, Japan). The heating profileswere obtained by capturing photographs using a forward-looking IRcamera (CPA-E6, Teledyne FLIR LLC., OR, USA).2.6. Magnetization Curve. The M−H curve under a DCmagnetic field of the mNP in a 0.544 mg/mL water suspension wasmeasured using the physical property measurement system (PPMS)(Quantum Design Inc., CA, US) at room temperature. The mNPsuspension was added to a glass tube and placed in the machine.2.7. Diels−Alder Polymer Reaction. The model drug�that is,NHS-PEG2-MAL (161.0 mg)�was dissolved in 11.5 mL of D2O.The p(DMAm145-co-FMA5) (100.0 mg) was then placed in thesample bin. The NHS-PEG2-MAL solution (1.0 mL) was added tothe polymer-containing sample bin and allowed to react understirring. The reacted sample solution (0.7 mL) was collected atvarious time points and analyzed using 1H NMR spectroscopy. Theprogress of the DA reaction was plotted as a function of reaction timewith respect to the newly formed proton-derived peaks correspondingto the Kendo (3.48 ppm) and Kexo (3.24 ppm) products of the DAreaction, which appeared after the reaction.2.8. Retro-Diels−Alder Reaction from the Polymer. For therDA reaction, the DA reaction solution (0.7 mL) was added to anNMR tube. The 1H NMR spectroscopy measurements wereperformed at different temperatures (40, 60, and 80 °C) at eachtime point (every 10 min for a total of 30 min). The progress of therDA reaction was plotted as the percentage of NHS-PEG2-MALremaining in the polymer from the Kendo (3.48 ppm) and Kexo (3.24ppm) products, which were used as references for the DA reaction, foreach reaction temperature and time. The plot begins with theintroduction ratio of NHS-PEG2-MAL to the polymer, which wasapproximately 60%.2.9. Biotin Conjugates and Releases upon the AC MagneticField on Magnetic Nanoparticles. The polymers pDMAm-b-pAAcand p(DMAm-co-FMA)-b-pAAc (2.5 mg) and the MNPs coated withpDMAm-b-pAAc and p(DMAm-co-FMA)-b-pAAc (polymer amountto be 2.5 mg) were predissolved in Milli-Q water, and 4.16 mg (6.96μM) of biotin-PEG3-MAL was dissolved in each solution and thenincubated for 4 days at 37 °C. To remove excess biotin-PEG3-MAL,Milli-Q water was added and concentrated using a 30 kDa Amiconultracentrifugal filter (3,500 rpm, 20 min). This washing process wasperformed in triplicate. The purified mNP solution was placed in a 1.5mL Eppendorf tube under an AC magnetic field (192 kHz, 480 A) byusing a HOSHOT2 instrument for 30 min to allow the release ofbiotin-PEG3-MAL. The released biotin-PEG3-MAL was collectedusing an Amicon ultracentrifugal filter (3,500 rpm, 20 min). Next, 20μL of the biotin-PEG3-MAL released sample was added to the well ofa 96-well plate, and 180 μL of the HABA/avidin assay mixture(AnaSpec, Inc., CA, US) was added to the same well. The sample wasmixed well by shaking it on a plate shaker at 100−200 rpm for 5 min,and the absorbance was read at 500 nm using a plate reader (Infinite200 PRO, Tecan Group Ltd., Ma ̈nnedorf, Switzerland). Themicroplate data could be calculated as follows:=A A A500 500,negative control 500,released biotin sample or positive control(1)=××MAbiotin concentration( )(34,500 0.5)dilution factor500 nmÄÇÅÅÅÅÅÅÅÅÅÅÉÖÑÑÑÑÑÑÑÑÑÑ(2)= =( 34,500 M , light path 0.5 cm)HABA/avidin1 (3)3. RESULTS AND DISCUSSION3.1. Polymer Synthesis. To template the mNP synthesisand facilitate drug incorporation via the DA reaction, this workdeveloped a diblock copolymer, p(DMAm-co-FMA)-b-pAAc.The pAAc block coordinates iron cations via carboxylatecomplexation, facilitating the formation of iron oxide particlecores.22 To improve the particles’ colloidal stability, furfurylmethacrylate (furan monomer) was copolymerized withdimethylacrylamide,23 p(DMAm-co-FMA). Additionally, thep(DMAm-co-FMA) block also provides furan groups to drugBiomacromolecules pubs.acs.org/Biomac Articlehttps://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−72747267https://pubs.acs.org/doi/suppl/10.1021/acs.biomac.5c00321/suppl_file/bm5c00321_si_001.pdfpubs.acs.org/Biomac?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-asmolecule conjugation via the DA reaction. The polymersynthesis is illustrated in Scheme 2. The p(DMAm-co-FMA)was first prepared via reversible addition−fragmentation chain-transfer (RAFT) polymerization of FMA and DMAm in thepresence of the chain-transfer agent (CTA) and a radicalinitiator. In addition to a homo-pDMAm (control), polymerswith the DMAm/FMA ratios as 150:0, 145:5, and 140:10 weresynthesized. 1H NMR spectroscopy was used to confirm thesuccessful polymerization (Figure S1). For p(DMAm145-co-FMA5), a number-average molecular weight (Mn) of 18,600Da was determined by GPC (DMF with 10 wt % LiCl) thatcorresponds to ∼174 monomeric units with a polydispersityindex (PDI) around 1.4 (Table S1). The resultant p(DMAm-co-FMA) block was utilized as the macro CTA (mCTA) forthe extension with AAc. The GPC and 1H NMR results werenot able to confirm the chain extension because of thepolyelectrolyte nature of pAA; its charged carboxyl groupsstrongly interact with the stationary phase of the column.24The molecular weight of (pDMAm145-co-FMA5)-b-pAAc7 wasalso analyzed using GPC (Figure S2) with DMF containing 10wt % LiCl as the mobile phase and PMMA standards forcalibration. The chromatogram showed two peaks: the peak at21 min corresponded to Mn ≈ 46 kDa with PDI = 1.1, whilethe peak at 25 min corresponded to Mn ≈ 6.5 kDa with PDI =1.3. We suspect that the first peak represents the blockcopolymer, whereas the second corresponds to the macroCTA, suggesting inefficient chain extension potentially due topartial macro CTA inactivation. However, the theoretical Mnfor the block copolymer is 18 kDa, which is significantly lowerthan the observed 46 kDa. Therefore, an accurate determi-nation of the polymer molecular weight by GPC was notpossible in this case. In 1H NMR spectroscopy, the proton ofthe carboxylic acid (−COOH) cannot be quantified because itexchanges with the deuterated solvent to form −COOD andthe peak may be lost.25 Therefore, titration with a sodiumhydroxide aqueous solution was utilized to analyze theincorporated carboxylates (pAAc) quantitatively (Figure S3).The average carboxyl groups per polymer chain were estimatedto be seven units.3.2. Synthesis of Magnetic Nanoparticles. Particlesynthesis followed the methodology described in our previousstudy by modifying the polymer design.22,26,30 The blockcopolymer was utilized in the in situ coprecipitation of ironoxide mNPs (Scheme 1). The particles were synthesized bykeeping the polymer concentration in the solution constant at10 mg/mL (5.5 μM acrylic acid) and varying the Fe/COOHratio from 1.25:1 to 20:1 (6.9−111.3 μM) (Table S2). Afterthe addition of NH4OH for inducing iron oxide formation, allreactions resulted in stable colloids except the reactions with a20:1 Fe/COOH ratio, which resulted in precipitatesimmediately. The colloidal stable mNPs were purified viasize exclusion chromatography (SEC) for further character-izations, including Fourier transform infrared spectroscopy(FT-IR), thermogravimetric-differential thermal analysis (TG-Scheme 2. Synthesis Scheme for Polymer Template Particle Synthesis: Copolymerization of Furfuryl Methacrylate (FMA)Containing the Reaction Site of the Diels−Alder Reaction and N,N-Dimethylacrylamide (DMAm), a Water-Soluble Monomer,in RAFT Polymerization, Followed by the Introduction of Acrylic Acid as a p(DMAm-co-FMA) Macro CTAaaThe block copolymer, p(DMAm-co-FMA)-b-pAAc, was synthesized by introducing acrylic acid as a macro CTA.Figure 1. (a) ATR-FT-IR of p(DMAm-co-FMA)-b-pAAc (red) and polymer-decorated mNPs (blue), (b) TG-DTA of polymer-decorated mNPs invarious Fe:COOH ratios, and (c) hydrodynamic radius of the synthesized mNPs in the ratio of 20:1.Biomacromolecules pubs.acs.org/Biomac Articlehttps://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−72747268https://pubs.acs.org/doi/suppl/10.1021/acs.biomac.5c00321/suppl_file/bm5c00321_si_001.pdfhttps://pubs.acs.org/doi/suppl/10.1021/acs.biomac.5c00321/suppl_file/bm5c00321_si_001.pdfhttps://pubs.acs.org/doi/suppl/10.1021/acs.biomac.5c00321/suppl_file/bm5c00321_si_001.pdfhttps://pubs.acs.org/doi/suppl/10.1021/acs.biomac.5c00321/suppl_file/bm5c00321_si_001.pdfhttps://pubs.acs.org/doi/suppl/10.1021/acs.biomac.5c00321/suppl_file/bm5c00321_si_001.pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=sch2&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=sch2&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig1&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig1&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig1&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig1&ref=pdfpubs.acs.org/Biomac?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-asDTA), dynamic light scattering (DLS), and scanning trans-mission electron microscopy (STEM) with energy-dispersiveX-ray spectroscopy (EDS) mapping.FTIR spectroscopy was performed to confirm the chemicalcomposition of the synthesized polymer and the mNPs. TheFTIR spectrum of the polymer exhibited characteristicabsorption bands corresponding to its functional groups. Abroad peak observed around 3,200−3,600 cm−1 was attributedto the O−H stretching vibration, indicative of carboxylfunctional groups. In Figure 1a, the presence of strongabsorption bands at 1,615 and 1,730 cm−1 confirmed theamide stretching (O�C−N) of pDMAm and carbonyl (C�O) stretching of pAAc. The presence of peaks at 1,055 and1,500 cm−1 are assigned to C−O−C and C�C stretchingbands in the furan ring.27 The mNP spectrum was very similarto the polymer spectrum; however, the absorption band ofcarbonyl stretching was significantly reduced because thecarboxyl groups are embedded in the particle core.The thermal analysis (Figure 1b), TG-DTA, was conductedto evaluate the thermal stability and composition of thepolymer-coated mNPs. The thermogram exhibited a fewdistinct weight loss regions corresponding to different thermalevents. The initial weight loss of approximately 5−20%observed below 150 °C was attributed to the removal ofadsorbed moisture from the particle surface. This indicates thepresence of physically bound water within the polymer coating.A significant weight loss of approximately 50% occurredbetween 200 and 500 °C, corresponding to the thermaldecomposition of the polymer shell. The major degradationstep suggests the breakdown of the polymer backbone,including the cleavage of organic functional groups. Beyond500 °C, the weight stabilized, indicating that the remaining15−40% of the sample was composed of thermally stable ironoxide, confirming the presence of the mNP core. These resultsdemonstrate the successful coating of the mNPs with apolymer layer and provide insight into their composition.DLS was performed to determine the hydrodynamic sizedistribution of the mNPs. The measurements revealed anaverage hydrodynamic radius of 55 nm (95% CI: 43−81 nm),Figure 1c. The particles also demonstrated good stability. Theywere stored at 4 °C for ≥4 months and remained colloidalstable prior to the conjugation and release experiments withoutobservable degradation. In addition, our previous work showedthat nanoparticles synthesized using polymeric templatesremain stable for more than 2 months while maintainingtheir particle size, transition temperature, and thermorespon-sive magnetic separation behavior.25Transmission electron microscopy (TEM) images of thesynthesized mNPs revealed a core−shell structure (Figure 2a(inset)), with darker contrast areas corresponding to the ironoxide core and a lighter contrast layer representing the polymercoating.33 To further analyze the size distribution of theparticle iron oxide cores, TEM images were used to construct ahistogram. The analysis determined an average core size of 7.7nm (95% CI: 7.0−8.4 nm), Figure 2b. Selected-area electrondiffraction analysis (Figure 2c) was performed via TEM toexamine the crystalline structure of the synthesized iron oxidenanoparticles. The diffraction pattern exhibited distinct ring-like diffraction features, indicative of a polycrystalline nature.28The observed diffraction rings corresponded to the character-istic lattice planes of magnetite (Fe3O4) or maghemite (γ-Fe2O3), with prominent reflections indexed to the (311) and(400) lattice planes.29EDS analysis was performed to determine the elementalcomposition of the synthesized nanoparticles, focusing on C,N, O, and Fe (Figure 2d). The EDS mapping from STEMrevealed a strong overlap of Fe and O, confirming the presenceof the iron oxide core. Additionally, N signal was observed,indicating the presence of the polymer coating. Thecolocalization of Fe, O, and N supports the successfulencapsulation of the mNPs with the polymer, further validatingthe core−shell structure.Several synthesis methods have been developed for mNPs,including sol−gel,30 coprecipitation,31 thermal decomposi-tion,9,32 microemulsion,33 and microwave-assisted techni-ques.34 In this study, we employed a coprecipitationmethod2,35 in aqueous conditions at room temperature. ThepAAc block served as a templating agent,22 enabling ironcation coordination via carboxylate complexation, followed byoxidation to form Fe3O4 nanoparticles. To achieve effectiveinductive heating under an AC magnetic field, Fe3O4 waspreferred over γ-Fe2O3 because of some reasons.36 Thesynthesis involved FeCl2·4H2O and FeCl3·6H2O as precursors,following the reaction:+ + ++ +Fe 2Fe 8OH Fe O 4H O2 33 4 2 (4)Iida et al. demonstrated that Fe3O4 particle size can becontrolled by adjusting the Fe2+/Fe3+ ratio during coprecipi-tation.37 The iron oxide core size of 7−9 nm observed in thisstudy aligns with previously reported values. The ability tocontrol particle size can potentially be utilized for tuningmagnetothermal properties, which will be discussed in thesection on heat generation behavior.The core−shell structure of the synthesized polymer-coatedmNPs was confirmed through multiple characterizationtechniques, including FT-IR, TGA, DLS, TEM, and EDS.The polymer not only facilitated iron oxide nanoparticleFigure 2. (a) TEM image of the synthesized mNPs, (b) core sizehistogram of the synthesized mNPs measured via the TEM image, (c)electron diffraction, and (d) EDS mapping image by STEM (c). Bluedots indicate Fe, green dots indicate oxygen, orange dots indicatenitrogen, and red dots indicate carbon.Biomacromolecules pubs.acs.org/Biomac Articlehttps://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−72747269https://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig2&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig2&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig2&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig2&ref=pdfpubs.acs.org/Biomac?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-asformation but also provided colloidal stability and a functionalsurface for drug conjugation via the DA reaction.3.3. Magnetization Curve and Heat GenerationBehavior. The superparamagnetic properties of the synthe-sized nanoparticles were characterized using vibrating samplemagnetometry (VSM) at room temperature over a ±1 T fieldrange (Figure 3a). The saturation magnetization (Ms) at anapplied field of 1 T was measured to be 0.15 emu/g, and themagnetization (H−M) curve exhibited negligible hysteresis,confirming the superparamagnetic nature of the nano-particles,38 which is essential for effective magnetic field-responsive heating and reversible dispersion in solutions.39To evaluate the magnetic induction heating capability,nanoparticle solutions (10.0 mg/mL) were subjected to analternating current (AC) magnetic field at 192 kHz and 480 A.The solution temperature was monitored in real time using aninfrared (IR) imaging system (Figure 3b). As shown in Figure3c, particles synthesized with Fe:COOH ratios of 5:1, 10:1,and 20:1 increased the solution temperature by 0, 1.5, and 6.2°C, respectively, after 300 s of AC magnetic field application.This trend clearly demonstrates that higher Fe:COOH ratiosresult in greater heating efficiency, supporting the conclusionthat magnetic heating performance is directly correlated withiron content.Magnetic heating efficiency was directly correlated with theFe:COOH ratio, as higher iron content resulted in greater heatgeneration, likely due to an increased magnetic momentdensity. A previous study demonstrated that the Ms (emu/g)of iron oxide nanoparticles increases with higher ironcontent.40 Consistent with this, we anticipate that nano-particles synthesized with higher Fe:COOH ratios possesshigher Ms values. Heating under an AC magnetic field isdirectly related to magnetic losses associated with thealignment and relaxation of magnetic moments; therefore,nanoparticles with higher Ms dissipate more heat. Thisexplains the observed increase in heating efficiency with higheriron content.The heat generation characteristics induced by analternating magnetic field in the magnetic nanoparticlessynthesized in this study are thought to involve both Neélrelaxation and Brownian relaxation for the following reasons.The observed heating behavior follows Neél relaxationmechanisms, as expected for nanoparticles of this size (7.7nm core diameter).20,40 In this process, the magnetic momentFigure 3. (a) M−H curve of mNPs in a 0.544 mg/mL water suspension at 298 K. Measured using the physical property measurement system; (b)IR images of particle solution at 21.7 and 27.9 °C with an applied AC magnetic field; (c) heat generation behavior of the synthesized mNPs.Figure 4. (a) Scheme of Diels−Alder reaction between the polymer and NHS-PEG2-MAL, (b) spectra of reaction progress of Diels−Alder reactionby 1H NMR (400 MHz), and (c) HABA assay result of biotin-PEG3-MAL and polymer conjugation. The furan-containing polymers (blue)resulted in ∼40% conjugation, and the polymers without furan (red) led to <10% nonspecific binding (*p < 0.005).Biomacromolecules pubs.acs.org/Biomac Articlehttps://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−72747270https://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig3&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig3&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig3&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig3&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig4&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig4&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig4&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig4&ref=pdfpubs.acs.org/Biomac?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-aswithin the crystal structure rotates in response to the externalfield, generating heat without significant physical movement ofthe nanoparticles. In contrast, Brownian relaxation, where heatis generated through physical rotation of particles due to fluidfriction, is typically dominant in larger nanoparticles.3,41 Thesize of mNPs plays a critical role in determining their magneticproperties and heating behavior. Bulk Fe3O4 exhibitsferromagnetic properties, but when reduced to a nanoscalediameter below 15 nm, particles transition to superparamag-netic behavior,7,38 which exhibits zero coercivity allowing themagnetic moments to rapidly align and relax in response to anapplied AC magnetic field. This property is particularlyadvantageous for biomedical applications, as it ensures noresidual magnetization once the external field is removed,thereby preventing nanoparticle aggregation in vivo. However,since Brownian motion was also observed in DLS for thisparticle, it was suggested that Brownian relaxation, not justNeél relaxation, may be involved in the heat generation ofmagnetic nanoparticles.The results demonstrate that magnetic induction heatingefficiency is correlated with iron oxide content, where higherFe/COOH ratios result in greater heat generation. It isimportant to consider that temperature measurements in thisstudy were obtained using an IR camera, which records thebulk solution temperature rather than the localized temper-ature at the particle surface. Since heat dissipation occursrapidly in aqueous environments, nanoparticles with a Fe/COOH ratio of 5:1, showing no significant heating effect inbulk measurements, may still experience significant localizedheating at the particle surface. The ability to generate localizedheating under an AC magnetic field presents a promisingapproach for remotely triggering drug release at targeted sites.Additionally, the ability to control iron content in polymer-templated nanoparticle synthesis provides a major advantagefor tuning magnetic heating behavior. By modulating nano-particle composition, heat generation can be optimized forintended applications, while minimizing off-target heatingeffects.3.4. Conjugation via the DA Reaction and Release viathe rDA Reaction. Other than templating the mNP synthesis,the block copolymer was designed to facilitate drug moleculeconjugation via the DA reaction by incorporating furanfunctional groups via the p(DMAm-co-FMA) block.4,42 Theinitial evaluation utilized N-hydroxysuccinimide-PEG2-malei-mide (NHS-PEG2-MAL) as a model molecule because themaleimide group can react with the polymer’s furan moieties toform a covalent linkage (Figure 4a). 1H NMR spectroscopywas used to monitor the formation of the exo (Kexo) and endo(Kendo) DA adducts, which represent two possible stereo-isomeric products of the DA reaction between furan andmaleimide.5,43 The characteristic signals at 3.23 (Kexo) and 3.48(Kendo) ppm clearly indicate the formation of the cycloadduct(Figure 4b). These peaks correspond to protons associatedwith the new carbon−carbon bonds formed during the DAcyclization of furan and maleimide. The appearance of twodistinct chemical shifts reflects the presence of both Kendo andKexo stereoisomers. While the overlap limits visual clarity, theobserved shifts are consistent with previously reported DAconjugation chemistry and support successful conjugation.43To demonstrate the Diels−Alder conjugation and retro-Diels−Alder release, maleimide-PEG2-biotin was utilized as themodel drug molecule. Specifically, polymers containing furangroups were incubated with the biotin solution at twobiotin:furan ratios, 1:1 and 1:0.5. After conjugation, free(unconjugated) biotin was removed by membrane filtration(Amicon, 10 kDa MWCO), and the filtrate biotin concen-tration was measured to estimate the amount of biotinconjugated to the polymer. Compared to the starting biotinsolution, a substantial reduction in filtrate biotin confirmed DAconjugation, with furan-containing polymers conjugating∼40% of biotin, while polymers lacking furan groups showed<10% nonspecific binding under identical conditions (Figure4c). These results confirm the successful conjugation of NHS-PEG2-MAL to the polymer via the DA reaction.To assess whether heat-induced rDA cleavage couldeffectively trigger drug release (Figure 5a), NHS-PEG2-MAL-functionalized polymers were incubated at 40, 60, and80 °C, with 1H NMR spectra collected every 5 min to monitorbond dissociation kinetics (Figure 5b). Specifically, theintegrations of chemical shifts at 3.23 ppm (Kexo) and 3.48ppm (Kendo) were used to quantify the extent of NHS-PEG2-MAL release over time. The rDA reaction progression wasplotted as the percentage of NHS-PEG2-MAL remaining in thepolymer based on the initial Kexo and Kendo reference signals.At 80 °C, the release was highly efficient, with approximately70% of NHS-PEG2-MAL released within 15 min. At 60 °C, amoderate release, ∼30%, was observed over 30 min, indicatinga temperature-dependent release profile. At 40 °C (near bodytemperature), no significant bond dissociation was detected,suggesting that the conjugated drug remained stable underphysiological conditions.The successful conjugation of NHS-PEG2-MAL to thepolymer via the DA reaction and its subsequent temperature-responsive release via the rDA reaction demonstrate thefeasibility. The stability of the drug−polymer conjugate atphysiological temperatures suggests that unintended prematurerelease is unlikely, which is critical for maintaining therapeuticefficacy and minimizing undesirable systemic exposure. TheFigure 5. (a) Scheme of retro-Diels−Alder reaction; (b) conversion rate of retro-Diels−Alder reaction at each temperature, calculated from 1HNMR measurement.Biomacromolecules pubs.acs.org/Biomac Articlehttps://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−72747271https://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig5&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig5&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig5&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig5&ref=pdfpubs.acs.org/Biomac?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-asability to trigger drug release only when needed offers adistinct advantage over conventional sustained-release systems,which may lack the ability to respond dynamically to changingtreatment needs.While the conjugation of a model maleimide-functionalizeddrug (biotin-PEG3-MAL) to the polymer and its subsequentthermally triggered release have been successfully demon-strated, the next step is to integrate magnetic induction heatingwith drug release studies. By combining magnetic field-drivenheat generation with drug conjugation and release, we aim toestablish the feasibility of remotely triggered, localized drugdelivery. Biotin-PEG3-MAL was conjugated to both thepolymers and the magnetic nanoparticles through the furanfunctional groups via the DA reaction. Biotin release wasquantified using the HABA assay (Figure 6). Polymers withand without furan groups served as controls to confirm releasevia the rDA reaction. Upon heating at 90 °C for 30 min, theaverage released biotin was nearly 0 μM for polymers withoutfuran and ∼80 μM for polymers containing furan. Under thesame heating conditions, particle conjugates released ∼103 μM(without furan) and ∼157 μM (with furan) biotin. When anAC magnetic field (192 kHz/480 A/min) was applied, theparticle conjugates released ∼103 μM (without furan) and∼150 μM (with furan) biotin. Thus, both direct heating andmagnetic induction heating triggered significantly higherbiotin-PEG3-MAL release from furan-containing polymersand particles (by ∼50−80 μM), confirming rDA release.Notably, higher levels of biotin detected in the furan-freeparticles suggest some degree of nonspecific binding. None-theless, the consistent increase in release for furan-containingsystems under both direct heating and AC magnetic fieldexposure demonstrates that induction heating effectivelytriggered the rDA reaction and subsequent drug release.The observed induction heating, 28 °C (Figure 3c), did notreach 80 °C for the rDA release. However, our results confirmbiotin released via induction heating. This indicates thatlocalized heating within the particles was achieved while thebulk temperature remained low. Dong and Zink measured coreheating within nanoparticles by analyzing the temperature-dependent intensity ratio of emission bands in theupconversion luminescence spectrum of a fluorescent materi-al.44 This was achieved using heat induced by super-paramagnetic nanocrystals supported on mesoporous silicaparticles. They found that while high temperatures wereinduced locally within the nanoparticles, the bulk temperatureremained relatively low. Therefore, even when the bulktemperature is low, the core of the magnetic nanoparticles isexpected to be sufficiently high to control thermoresponsiblereaction.This work establishes the feasibility of DiMaN as a platformfor on-demand, magnetically triggered drug release, and severaldirections will further strengthen its biomedical potential.Future studies will focus on directly correlating inductiveheating efficiency with drug release kinetics, optimizingnanoparticle surface temperatures to improve rDA activation,and systematically assessing in vivo stability and biocompat-ibility. While biocompatibility testing was not performed here,prior studies have shown that magnetic nanoparticles coatedwith polymers such as poly(dimethylacrylamide) exhibitminimal or no acute toxicity.29,30 The synthesized diblockcopolymer enabled nanoparticle formation and drug con-jugation via the DA reaction, while the iron oxide corefacilitated magnetothermal heating under an AC magneticfield. Using biotin-PEG3-MAL as a model drug provided aconvenient proof-of-concept system because the maleimidegroup allowed efficient conjugation and release, while thebiotin moiety served as a quantifiable marker; moreover, biotinis a biologically relevant small molecule (vitamin B7). Movingforward, extending this strategy to maleimide-functionalizedtherapeutics such as doxorubicin will greatly increasebiomedical relevance, allowing in vitro and in vivo studies oftherapeutic efficacy and biological response. Although rDAcleavage was observed at ∼80 °C in vitro, which may raiseconcerns about tissue safety, magnetic induction heating ishighly localized at the nanoparticle interface. Supporting this,Attaluri et al. demonstrated that while implanted nanoparticlesreached ∼80 °C under an alternating magnetic field, tissuetemperatures returned to near-physiological levels within 2 mmof the heated site.45 These findings suggest that localizedheating sufficient to trigger rDA release can be achievedwithout widespread tissue damage. With these refinements,DiMaN offers a promising path toward externally controlled,site-specific, and precise drug delivery for applications inoncology and beyond.4. CONCLUSIONSThis study demonstrates the successful development ofDiMaN, polymer-coated magnetic nanoparticles, as a promis-ing platform for on-demand drug release via magneticinduction heating-triggered retro-Diels−Alder reactions. Thesystem enabled efficient conjugation of maleimide-function-alized drugs, thermally responsive release with retro-Diels−Alder cleavage at elevated temperatures (≥80 °C) whilemaintaining stability under physiological conditions (37 °C),and confirmation of magnetic induction heating capabilities.Together, these results establish the fundamental chemistryand heating properties of the platform. Looking forward, futurework will integrate magnetic field-driven heating with directdrug release, optimize release kinetics, and evaluate biologicalperformance, enabling precise site-specific treatment whileminimizing systemic drug exposure and off-target effects.Expanding the approach to include a broader range ofconjugated therapeutics, such as chemotherapeutics andbiologics, will further demonstrate the system’s versatility forprecision medicine applications. With continued refinement,this mNP-based delivery strategy holds strong potential toFigure 6. Biotin release profile for polymers with direct heating(blue), particles with direct heating (red), and particles with inductionheating (green).Biomacromolecules pubs.acs.org/Biomac Articlehttps://doi.org/10.1021/acs.biomac.5c00321Biomacromolecules 2025, 26, 7265−72747272https://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig6&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig6&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig6&ref=pdfhttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321?fig=fig6&ref=pdfpubs.acs.org/Biomac?ref=pdfhttps://doi.org/10.1021/acs.biomac.5c00321?urlappend=%3Fref%3DPDF&jav=VoR&rel=cite-asachieve externally controlled, on-demand drug release, pavingthe way for highly selective and personalized therapeuticinterventions in oncology and beyond.■ ASSOCIATED CONTENTData Availability StatementThe original contributions presented in the study are includedin the article/Supporting Information. Further inquiries can bedirected at the corresponding author.*sı Supporting InformationThe Supporting Information is available free of charge athttps://pubs.acs.org/doi/10.1021/acs.biomac.5c00321.1H NMR for synthesized polymers, polymer synthesisconditions and GPC analysis, GPC chromatogram ofp(DMAm-co-FMA)-b-pAAc, pH titration results, andiron salt-to-polymer ratios for magnetic nanoparticlesynthesis (PDF)■ AUTHOR INFORMATIONCorresponding AuthorsMitsuhiro Ebara − Research Center for Macromolecules andBiomaterials, National Institute for Materials Science,Tsukuba 305-0044, Japan; Graduate School of Pure andApplied Sciences, University of Tsukuba, Tsukuba 305-8577,Japan; orcid.org/0000-0002-7906-0350;Email: EBARA.Mitsuhiro@nims.go.jpJames J. Lai − Department of Materials Science andEngineering, National Taiwan University of Science andTechnology, Taipei 10607, Taiwan; Department ofBioengineering, University of Washington, Seattle,Washington 98195, United States; orcid.org/0000-0003-3437-7810; Email: jameslai@mail.ntust.edu.twAuthorNanami Fujisawa − Research Center for Macromolecules andBiomaterials, National Institute for Materials Science,Tsukuba 305-0044, Japan; Graduate School of Pure andApplied Sciences, University of Tsukuba, Tsukuba 305-8577,JapanComplete contact information is available at:https://pubs.acs.org/10.1021/acs.biomac.5c00321Author ContributionsN.F. and J.J.L. designed the research. N.F. and J.J.L. performedthe research. N.F., M.E., and J.J.L. analyzed the data. N.F.,M.E., and J.J.L. designed the figures and wrote the text. N.F.,M.E., and J.J.L. analyzed and discussed the data. All authorshave read and agreed to the published version of themanuscript.FundingThis study was supported by NIAID/NIH AI163282, JSPSKAKENHI Grant-in-Aid for JSPS Fellows (22KJ0434), Grant-in-Aid for Transformative Research Areas (A) (20H05877),and “Advanced Research Infrastructure for Materials andNanotechnology in Japan (ARIM)” of the Ministry ofEducation, Culture, Sports, Science and Technology(MEXT), proposal number JPMXP1224NM5127.NotesThe authors declare no competing financial interest.■ ACKNOWLEDGMENTSThe authors thank Dr. Hiroaki Mamiya (National Institute forMaterials Science, Japan) for assisting with M−H curvemeasurement of mNPs via the physical property measurementsystem (PPMS) (Quantum Design, CA, US).■ REFERENCES(1) Andre, T.; Louvet, C.; Maindrault-Goebel, F.; Couteau, C.;Mabro, M.; Lotz, J. P.; Gilles-Amar, V.; Krulik, M.; Carola, E.; Izrael,V.; de Gramont, A. 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