Pure PNIPAAm Research Articles

Reversibly Adhesive, Anti-Swelling, and Antibacterial Hydrogels for Tooth-Extraction Wound Healing.

Oral wound treatment faces challenges due to the complex oral environment, thus, sealing the wound quickly becomes necessary. Although some materials have achieved adhesion and sterilization, how to effectively solve the contradiction between strong adhesion and on-demand removal remains a challenge. Herein, a reversibly adhesive hydrogel is designed by free radical copolymerization of cationic monomer [2-(acryloyloxy) ethyl] trimethylammonium chloride (ATAC), hydrophobic monomer ethylene glycol phenyl ether acrylate (PEA) and N-isopropylacrylamide (NIPAAm). The cationic quaternary ammonium salts provide electrostatic interactions, the hydrophobic groups provide hydrophobic interactions, and the PNIPAAm chain segments provide hydrogen bonding, leading to strong adhesion. Therefore, the hydrogel obtains an adhesion strength of 18.67KPa to oral mucosa and can seal wounds fast within 10s. Furthermore, unlike pure PNIPAAm, the hydrogel has a lower critical solution temperature of 40.3°C due to the contribution of ATAC and PEA, enabling rapid removal with 40°C water after treatment. In addition, the hydrogel realizes excellent anti-swelling ratio (≈80%) and antibacterial efficiency (over 90%). Animal experiments prove that the hydrogel effectively reduces inflammation infiltration, promotes collagen deposition and vascular regeneration. Thus, hydrogel as a multi-functional dressing has great application prospects in oral wound management.

Fracture Toughness and Blocking Force of Temperature-Sensitive PolyNIPAAm and Alginate Hybrid Gels.

In the field of actuator materials, hydrogels that undergo large volume changes in response to external stimuli have been developed for a variety of promising applications. However, most conventional hydrogels are brittle and therefore rupture when they are stretched to moderate strains (~50%). Thus, gels to be used for actuators still require improved mechanical properties and actuation performance. In this study, we synthesized a tough and thermo-sensitive hydrogel with a large actuation force by forming interpenetrating networks between covalently crosslinked poly(N-isopropylacrylamide) and ionically crosslinked alginate. Poly(N-isopropylacrylamide) was used as a thermo-sensitive actuation material, and alginate was found to enhance the mechanical properties of the hydrogels. Due to the enhanced elastic modulus and energy dissipation in the hybrid gel, the toughness was increased by a factor of 60 over that of pure PNIPAAm gel. Further, based on the results showing that the hybrid gel exhibits an actuation force that is seven times higher than that of pure PNIPAAm gel, the hybrid gel is more applicable to real actuators.

Novel fluorescent hydrogel for the adsorption and detection of Fe (III)

A novel PNIPAAm-CD hydrogel with good adsorption property and stable fluorescence detection for Fe3+ was prepared by copolymerizing PCDs with NIPAAm monomers. As a fluorescence probe, carbon quantum dots (CDs) were modified by glycidyl methacrylate (GMA) to obtain PCDs, which had double bond and could react with N-isopropyl acrylamide to form hydrogel. The functionalization of the amine groups on the surface of the PCDs enables PNIPAAm-CD hydrogel also exhibits photoluminescence behavior. In addition, the PNIPAAm-CD hydrogels stably shows higher adsorption performance for Fe3+ than the pure PNIPAAm hydrogel. The honeycomb PNIPAAm-CD hydrogel had a good quenching response to metallic iron ions, and the detection limit was as low as 0.27 μM in the range of 1μM～1mM. The results of adsorption isotherms and adsorption kinetics showed that the adsorption procedure of metal ions conforms to the pseudo-second-order model and langmuir model, respectively. The effective detection and the high adsorption of PNIPAAm-CD hydrogel for Fe3+ make it an effective portable platform potential, which has the dual functions of visual detection and adsorption of Fe3+.

Preparation and characterisation of fire-resistant PNIPAAm/SA/AgNP thermosensitive network hydrogels and laminated cotton fabric used in firefighter protective clothing

The protective clothing of firefighters requires specialised fire-resistant materials to ensure their safety. In this work, a novel fire-resistant material was prepared by laminating an interpenetrating polymer network (IPN) hydrogel on cotton fabric. The hydrogel-fabric laminates can be used as a flame-retardant material to produce firefighter protective clothing. The IPN hydrogel layer comprised poly (N-isopropylacrylamide) (PNIPAAm), sodium alginate (SA) and silver nanoparticles (Ag NPs). The chemical structures, swelling ratio, thermal properties, microstructures and tensile properties of the synthesised IPN hydrogel were investigated using Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and tensile testing, respectively. Results revealed that the water content of IPN hydrogel was approximately 2186% at 20 °C, indicating excellent ability to absorb energy as water heats up and evaporate. FTIR results showed that the PNIPAAm and SA were only physical interpenetrated within the IPN hydrogel. Moreover, compared with pure PNIPAAm, IPN hydrogel displayed better elastic and breaking strength. Vertical burning findings indicated that the hydrogel-fabric laminates did not burn when exposed to flame for 12 s, whereas natural cotton fabric was burned out. Finally, the fire-resistant hydrogel displayed excellent antibacterial activity against Staphylococcus aureus and Escherichia coli through the introduction of Ag NPs, and the antibacterial activity for both microorganisms exceeded 96%. Overall, this study provided an easy approach to producing a fire-resistant material by laminating a hydrogel and a fabric that may save lives.

Two-dimensional thermoresponsive sub-microporous substrate for accelerated cell tissue growth and facile detachment

Thermoresponsive sub-microporous films having a lower critical solution temperature (LCST), promptly obtained by using the breath figure method, were applied to tissue engineering. These sub-microporous films, sized 100–400 nm, were prepared by blending poly(N-isopropylacrylamide) (PNIPAAm) with polystyrene (PS), in addition to applying the dynamic breath figure (BF) method. The thermoresponsive blends were prepared with polyethylene terephthalate (PET) substrate by using a spin coater; the pore size was modulated according to the spin speed. The sub-microporous films, either with pure PNIPAAm or with different PNIPAAm contents were applied as substrates in order to obtain cell growth (Vero cells); moreover, the effect of PNIPAAm use was evaluated. The PNIPAAm sub-microporous films made the cellular viability to be 9-13-fold higher than the control sample commonly used in cell culture. In addition, the thermoresponsive PNIPAAm properties were even noticed at a low PNIPAAm content in the porous films. Such polymer system was successfully applied to detach the Vero cell tissue using temperature variation.

Cell attachment/detachment behavior on poly(N-isopropylacrylamide)-based microgel films: the effect of microgel structure and swelling ratio

Microgels are cross-linked soft particles with a three-dimensional network structure that are swollen in a good solvent. Poly(N-isopropylacrylamide) (pNIPAAm)-based microgels have attracted great attentions for their temperature responsive property, particularly in recent years, pNIPAAm-based microgel films were utilized as a new kind of thermoresponsive surface to tune cell attachment/detachment behavior via temperature stimuli. However, some results are not consistent, for example, different polymerization conditions may bring out different results even for pure pNIPAAm microgel. This work aims to find out which factor plays the critical role for successful cell detachment on the pNIPAAm-based microgel films. The results unraveled that the structure and swelling ratio of the microgel rather than the film thickness plays a key role on the successful cells detachment, unlike linear pNIPAAm films in which the cells’ attach/detach property is only determined by the film thickness. For poly(N-isopropylacrylamide–styrene) microgel film, NIH3T3 cells could only detach when the microgel has a uniform structure and the volume dilatation of the microgel (20/38 °C) is larger than 4.

Rhodamine-loaded surface modified mesoporous silica particles embedded into a thermoresponsive composite hydrogel for prolonged release

In this manuscript, the synthesis and release capability of a composite system is presented. The composite consists of a surface polymerized mesoporous silica loaded with rhodamine B (RhB) embedded into a crosslinked thermoresponsive polymer. The mesoporous silica was synthesized using a hydrothermal procedure followed by surface functionalization and polymerization with PNiPAAm to obtain a thermoresponsive gated system. Further, the silica particles were loaded with rhodamine B and incorporated into a PNiPAAm hydrogel, yielding a composite system with drug delivery capabilities. Confocal fluorescence microscopy was used to confirm the mesoporous silica was effectively loaded with RhB and distributed within the hydrogel. Rhodamine release assays were carried out under equilibrium and non-equilibrium conditions for the polymerized silica, the pure PNiPAAM hydrogel and the PNiPAAm composites, and the materials were characterized at temperatures above and below the lower critical system temperature (LCST) of PNiPAAm. Three kinetic models were used to study the release performance: the power law, diffusion and relaxation, and Gallagher-Corrigan model. Fitting results of the experimental rhodamine-releasing data to the models strongly suggest the existence of a double diffusion barrier in which the composite prevents the burst release. The combination of the drug releasing properties of mesoporous silica and the stimuli responsiveness of poly(N-isopropylacrylamide) (PNiPAAm) in a single composite resulted in an interesting drug delivery system useful for applications where a prolonged temperature controlled release may be required.

Thermo-and pH-sensitive hydrogel membranes composed of poly(N-isopropylacrylamide)-hyaluronan for biomedical applications: Influence of hyaluronan incorporation on the membrane properties

Interpenetrating hydrogel membranes consisting of pH-sensitive hyaluronan (HA) and thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAM) were synthesized using redox polymerization, followed by N,N-methylenebisacrylamide (BIS) and epichlorohydrin (EPI) were added as chemical crosslinkers. The interaction between membrane compositions has been characterized by FTIR spectroscopy and discussed intensively. The result indicates that HA incorporation in membranes increase the gel fraction, swelling uptake, and the flexibility/elasticity of crosslinked membranes, however it reduced oppositely the mechanical elongation of membranes. PNIPAAm-HA hydrogels responded to both temperature and pH changes and the stimuli-responsiveness was reversible. However, in vitro bioevaluation results revealed that the released ampicillin during the burst release time was sharply influenced and increased with increasing HA contents in membranes; afterwards it became sustainable. Whereas, high HA contents in hydrogels unexpectedly impacted negatively on the cells viability, owing to the viscosity of cell culture media changed. A big resistance was observed against microbial growth of Staphylococcus aureus, Salmonella typhi, and Candida albicans in case of pure PNIPAAm hydrogel membranes without HA or ampicillin. However, HA incorporation or the loaded ampicillin in membranes showed unexpected easily microbial growth. The fast release performance with dual pH-thermo-sensitive hydrogels were suggested as promising materials for quick drug carrier in the biomedical field.

Effect of Sodium Alginate on the Properties of Thermosensitive Hydrogels

Sodium alginate (SA) was combined with poly(N‐isopropylacrylamide) (PNIPAAm) to prepare thermosensitive hydrogels through semi‐interpenetrating polymer network (semi‐IPN) and fully interpenetrating polymer network (full‐IPN). The thermosensitive, swelling, mechanical, and thermal properties of pure PNIPAAm, SA/PNIPAAm semi‐IPN, and Ca‐alginate/PNIPAAm full‐IPN hydrogels were investigated. The formation of semi‐IPN and full‐IPN significantly improved the hydrogels’ swelling capability and mechanical properties without altering their thermosensitivity. 5‐Fluorouracil (5‐Fu) was selected as a model drug to study the release behaviors of the hydrogels. It was found that in vitro controlled drug release from semi‐IPN hydrogels showed an initial release burst, followed by a slower and sustained release, before reaching equilibrium. Full‐IPN hydrogels showed slow and sustained release during the whole process. Temperature and pH were found to affect the rate of drug release. Ca‐alginate/PNIPAAm full‐IPN hydrogels have potential application as drug delivery matrices in controlled drug release.

Supermolecules of poly(N-isopropylacrylamide) complexating Herring sperm DNA with bio-multiple hydrogen bonding

In this study we used the poly(N-isopropylacrylamide) (PNIPAAm) as a medium to blend with an organic DNA, herring sperm DNA (HSD), to generate PNIPAAm-HSD supramolecular complexes. Bio-multiple hydrogen bonding (BMHB) between PNIPAAm and HSD was investigated that changed the temperature responsiveness of PNIPAAm relatively to the HSD concentrations. With blending the HSD into PNIPAAm matrix, the phase separation in solution is completely opposite from that of neat PNIPAAm. Surface property in static water contact angle (SWCA) is also opposite from that of pure PNIPAAm upon increasing HSD content over 60%. In addition, we found that the PNIPAAm and HSD self-assembled a specific triangle-like structure at a PNIPAAm-to-HSD weight ratio of 1:4 at 25°C; while the triangle-like structure disappeared with increasing temperature to 45°C. Furthermore, both PNIPAAm and HSD could be regarded as insulator, but it transformed into a semiconductive matter after blending with the HSD. Incorporation of organic DNA with hydrogel could significantly change their properties, which might facilitate their use as novel materials in bioelectronics.

Synthesis and characterization of thermosensitive hydrogel with improved mechanical properties

Abstract

Thermo-responsive cell culture carriers based on poly(vinyl methyl ether)—the effect of biomolecular ligands to balance cell adhesion and stimulated detachment

Two established material systems for thermally stimulated detachment of adherent cells were combined in a cross-linked polymer blend to merge favorable properties. Through this approach poly(N-isopropylacrylamide) (PNiPAAm) with its superior switching characteristic was paired with a poly(vinyl methyl ether)-based composition that allows adjusting physico-chemical and biomolecular properties in a wide range. Beyond pure PNiPAAm, the proposed thermo-responsive coating provides thickness, stiffness and swelling behavior, as well as an apposite density of reactive sites for biomolecular functionalization, as effective tuning parameters to meet specific requirements of a particular cell type regarding initial adhesion and ease of detachment. To illustrate the strength of this approach, the novel cell culture carrier was applied to generate transplantable sheets of human corneal endothelial cells (HCEC). Sheets were grown, detached, and transferred onto planar targets. Cell morphology, viability and functionality were analyzed by immunocytochemistry and determination of transepithelial electrical resistance (TEER) before and after sheet detachment and transfer. HCEC layers showed regular morphology with appropriate TEER. Cells were positive for function-associated marker proteins ZO-1, Na+/K+-ATPase, and paxillin, and extracellular matrix proteins fibronectin, laminin and collagen type IV before and after transfer. Sheet detachment and transfer did not impair cell viability. Subsequently, a potential application in ophthalmology was demonstrated by transplantation onto de-endothelialized porcine corneas in vitro. The novel thermo-responsive cell culture carrier facilitates the generation and transfer of functional HCEC sheets. This paves the way to generate tissue engineered human corneal endothelium as an alternative transplant source for endothelial keratoplasty.

Thermo- and pH-sensitive interpenetrating poly(N-isopropylacrylamide)/carboxymethyl pullulan network for drug delivery

Interpenetrating polymer networks (IPN) consisting of pH-sensitive carboxymethyl pullulan (CMP) and thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) were synthesized through a two-step procedure by chemical cross-linking of NIPAAm in the presence of CMP, followed by additional reticulation of the polysaccharide. The hydrogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and swelling measurements. Swelling properties of the hydrogels were studied at equilibrium, by investigating pH- and temperature-dependence, dynamic swelling ratio and pulsatile swelling-deswelling kinetics. It was found that IPN hydrogels responded to both temperature and pH changes and such stimuli-responsiveness was reversible. At pH 1.2 and temperature values lower than VPTT, the swelling ratios of IPN hydrogels are smaller than that of pure PNIPAAm because most of the carboxylic groups are protonated forming hydrogen bonds with other carboxylic or amide groups of PNIPAAm. Conversely, in phosphate buffer solutions at pH 7.4, the swelling ratios of IPN hydrogels are higher than that of pure PNIPAAm. In this case, the carboxylic groups of CMP are ionized; therefore, the hydrogen bonds are broken and the electrostatic repulsions lead to a more expanded network. The loading and release profiles of a model drug namely, diphenhydramine (DPH), were also evaluated. The results showed that the release rate of DPH was higher at pH 10 buffer solution than at pH 7.4 and 1.2, at 37 °C. In pseudo physiological conditions, DPH was quickly released from the hydrogel at 20 °C, and showed a sustained release profile at 37 °C.

Highly-Branched Poly(N-isopropylacrylamide) as a Component in Poly(dopamine) Films

Mixed one-step poly(dopamine) (PDA)/highly branched poly(N-isopropylacrylamide) (pNiPAAm) coatings have been assembled and characterized by X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, atomic force microscopy, and quartz crystal microbalance with dissipation monitoring (QCM-D) depending on the deposition temperature below and above the lower critical solution temperature (LCST) of the pNiPAAm. Mixed films were confirmed. The protein adsorption at 24 °C was found to be reduced with increasing amount of pNiPAAm in the mixed coatings, while there was no difference observed for proteins deposition at 39 °C. Further, the ability of these mixed coatings in comparison to the pure PDA and pNiPAAm films to serve as capping layer for surface-immobilized zwitterionic or positively charged liposomes has been assessed by QCM-D. The adhesion of hepatocytes, macrophages, and myoblast to these liposomes-containing hybrid coatings and the uptake of fluorescent lipids from the surface by the adhering cells depending on the capping layers were compared. The latter aspect was found to be dependent on the used capping layer and the type of liposome as carrier for the fluorescent lipid, with the highest uptake found for positive liposomes and pure pNiPAAm as capping layer. Taken together, the assembled hybrid coatings have the potential to be used as functional coatings toward surface-mediated drug delivery.

Properties and drug release profile of poly(N-isopropylacrylamide) microgels functionalized with maleic anhydride and alginate

This study highlights the advantages of functionalized poly(N-isopropylacrylamide) (PNIPAAm) microgels over pure PNIPAAm microgels in terms of polymer network properties and drug release profiles. PNIPAAm network was modified by addition of maleic anhydride (MA) as a comonomer and by formation of interpenetrating polymer network in the presence of alginate. The functionalized thermosensitive microgels in the size range from 20 to 80 μm and with better performance in comparison with pure PNIPAAm microgels were prepared by inverse suspension polymerization. The impact of MA and alginate on the PNIPAAm microgel structure was evaluated through analysis of microgel size, size distribution, volume phase transition temperature (VPTT), equilibrium swelling ratio as well as morphology of the system. It was shown that the controlled modification of PNIPAAm network could result in microgels of considerably improved swelling capacity with unchanged thermosensitivity and maintained open pore morphology. In addition, drug release behavior of microgels could be markedly altered. Release of procaine hydrochloride from the selected microgels was studied using Franz diffusion cell at temperatures below and above VPTT of the microgels. Temperature-controlled drug release pattern was dependent on the type of functionalization of PNIPAAm network. According to drug loading properties and drug release mechanism, PNIPAAm/MA copolymer microgels demonstrated the optimal performances.

Thermally Responsive Amphiphilic Conetworks and Gels Based on Poly(N-isopropylacrylamide) and Polyisobutylene

Novel amphiphilic conetworks (APCN) consisting of thermoresponsive poly(N-isoproplyacrylamide) (PNiPAAm) cross-linked by hydrophobic methacrylate-telechelic polyisobutylene (MA-PIB-MA) were successfully synthesized in a broad composition range. The resulting PNiPAAm-l-PIB conetworks (“l” stands for “linked by”) were obtained by radical copolymerization of NiPAAm with MA-PIB-MA in tetrahydrofuran, a cosolvent for all the components. Low amounts of extractables substantiated efficient network formation. The composition dependent two glass transition temperatures (Tg) by DSC analysis indicate microphase separation of the cross-linked components without mixed phases. It was found that the PNiPAAm-l-PIB conetworks are uniformly swellable in both water and n-hexane; i.e., these new materials behave either as hydrogels or as hydrophobic gels in aqueous or nonpolar media, respectively. The uniform swelling in both polar and nonpolar solutes indicates cocontinuous (bicontinuous) phase morphology. The equilibrium swelling degrees (R) depend on composition, that is, the higher the PIB content, the lower the R in water and the higher in n-hexane. The PNiPAAm phase keeps its thermoresponsive behavior in the conetworks as shown by significant decrease of the swelling degree in water between 20 and 35 °C. The lower critical solubility temperature (LCST) values determined by DSC are found to decrease from 34.1 °C (for the pure PNiPAAm homopolymer) to the range of 25–28 °C in the conetworks, and the extent of the LCST decrease is proportional with the PIB content. Deswelling-swelling, i.e., heating–cooling, cycle indicates insignificant hysteresis in these new thermoresponsive materials. This indicates that PNiPAAm-l-PIB conetworks with predetermined and thermoresponsive swelling behavior can be designed and utilized in several advanced applications on the basis of results obtained in the course of this study.

Self-Assembly Process of Soft Ferritin-PNIPAAm Conjugate Bionanoparticles at Polar–Apolar Interfaces

We describe an in-depth investigation on the dynamics and assembly behavior at polar-apolar interfaces of ferritin-PNIPAAm conjugates (poly-N-isopropylacrylamide). The stabilization of oil-water interfaces by the modified ferritin was investigated by dynamic surface tension measurements and compared to the individual components of the bionanoparticle conjugate, namely, unmodified ferritin and pure PNIMAAm of similar molecular weight. It was found that the modified ferritin, even at a low particle concentration, rapidly reduces the interfacial tension. The difference in interfacial stabilization was also shown by cryo-scanning electron microscopy and scanning force microscopy, which displayed very different morphologies at the polar-apolar interface for the unmodified ferritin, pure PNIPAAm, and the ferritin-PNIPAAm conjugate, respectively. The self-assembly of the ferritin-PNIPAAm was further analyzed by cryo-transmission electron microscopy and fluorescence microscopy, for which a fluorescently labeled polymer was used. Both techniques revealed details on the assembly of the protein-polymer conjugate at the oil-water interface.

Engineering a sharp physiological transition state for poly(n‐isopropylacrylamide) through structural control

AbstractPoly(N‐isopropylacrylamide) (pNIPAAm), a well‐studied, biologically inert polymer that undergoes a sharp aqueous thermal transition at 32 °C, has been a subject of widespread interest for possible biological applications. A major hindrance to its successful application is due to the difficulty of maintaining a sharp transition when the polymer is modified for a physiological transition temperature, especially in isotonic solutions. Current copolymer blends raise the transition temperature but also make the transition significantly broader. We have combined the use of reversible addition‐fragmentation chain transfer (RAFT) polymerization with tacticity control to synthesize well‐defined pNIPAAm that demonstrates sharp transitions under physiological conditions. By selecting a RAFT agent with appropriate end groups, controlling molecular weight, and increasing the racemo diad content, we were able to increase the thermal transition temperature of pure pNIPAAm to a sharp transition at 37.6 °C under isotonic conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Development and characterization of thermosensitive hydrogels based on poly(N‐isopropylacrylamide) and calcium alginate

AbstractThis work refers to the synthesis and characterization of thermosensitive hydrogels based on interpenetrating polymer networks (IPNs) of poly(N‐isopropylacrylamide) (PNIPAAm) and calcium alginate in the form of films. The influence of the crosslinking degree of PNIPAAm and alginate content on thermal, swelling, mechanical, and morphological properties of hydrogels is investigated in detail. Characterization of pure PNIPAAm hydrogels and IPN hydrogels was performed by FTIR, DSC, DMA, and SEM. In addition, the studies of equilibrium swelling behavior as well as swelling, deswelling, and reswelling kinetics are performed. The results obtained imply the benefits of synthesizing IPNs based on PNIPAAm and calcium alginate over pure PNIPAAm hydrogels. The presence of calcium alginate contributes to the improvement of mechanical properties, the deswelling rate of hydrogels, and the network porosity, without altering the thermosensitivity of PNIPAAm significantly. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Thermoresponsive Nanocomposite Hydrogels: Transparency, Rapid Deswelling and Cell Release

Thermal modulation reversibly switches poly(N-isopropylacrylamide) (PNIPAAm) hydrogels between a water-swollen and a deswollen state which is useful for a variety of biomedical applications. The utility and efficiency of PNIPAAm hydrogels requires tailoring their rate of deswelling/reswelling, mechanical properties and/or optical clarity. In the current work, we prepared novel thermoresponsive nanocomposite hydrogels comprised of a PNIPAAm hydrogel matrix and polysiloxane colloidal nanoparticles (~54 nm ave. diameter) via in situ photopolymerization of aqueous solutions of NIPAAm monomer, N,N'-methylenebisacrylamide (BIS, crosslinker), photoinitiator and 0.5-4.0 wt% polysiloxane nanoparticles (wt% solids of nanoparticles with respect to NIPAAm weight) at ~7 °C. At these nanoparticle concentrations, the nanocomposite hydrogels were more optically transparent versus those prepared with analogous larger nanoparticles (~219 nm ave. diameter). The volume phase transition temperature (VPTT) of the nanocomposite hydrogels was conveniently unaltered versus that of the pure PNIPAAm hydrogel. Incorporation of nanoparticles caused enhancement in modulus as well as the extent and rate of deswelling. When cooled from 37 °C to 25 °C, mouse smooth muscle precursor cells (10T1/2) were effectively detached from nanocomposite hydrogel surfaces due to hydrogel swelling.