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A pioneering method is reported for creating thermoresponsive biofunctional hydrogel microstructures using maskless multiphoton lithography. Departing from conventional multiphoton‐triggered polymerization‐based techniques, this approach relies on simultaneous photocrosslinking and attachment of already pre‐synthesized polymer chains onto solid substrates. The method allows improving control over polymer network characteristics and enables facile integration of additional functionalities through postmodification with biomolecules at specific sites. Exploring two distinct benzophenone‐ and anthraquinone‐based photocrosslinkers incorporated into specially designed poly(N‐isopropyl acrylamide)‐based co‐ and terpolymers, the photocrosslinking efficacy is scrutinized with the use of a custom femtosecond near‐infrared laser lithographer. Comprehensive characterization via surface plasmon resonance imaging, atomic force microscopy, and optical fluorescence microscopy reveals swelling behavior and demonstrates postmodification feasibility. Notably, within a specific range of multiphoton photocrosslinking parameters, the surface‐attached microstructures exhibit a quasiperiodic topography akin to wrinkle‐pattern formation. Leveraging the capabilities of established multiphoton lithographer systems that offer fast pattern writing with high resolution, this approach holds great promise for the versatile fabrication of multifunctional 3D micro‐ and nanostructures. Such tailored responsive biofunctional materials with spatial control over composition, swelling behavior, and postmodification are particularly attractive in the areas of bioanalytical and biomedical technologies. [ABSTRACT FROM AUTHOR]

We present the control of liquid flow through arrayed micron-sized pores in a macroporous silicon membrane. The pores are coated with about 150 nm polymer N-isopropylacrylamide (pNIPAAm) hydrogel brushes and 200 nm polypyrrole layer, which works as photothermal actuator. The size of pore openings is controlled by utilizing the swelling and de-swelling behavior of temperature-sensitive pNIPAAm brushes, and the temperature on pNIPAAm brushes is changed by 815 nm near infra-red (NIR) illumination to polypyrrole photothermal element layer. The dimension change of the pore openings is investigated by observing the transmitted light and fluorescence signal intensity through the pores in the membrane while changing the ambient temperature. It has shown that the intensity of transmitted light can be controlled by adjusting the ambient temperature across the low critical solution temperature (LCST) of the hydrogel brushes. The localized control of liquid flow through the pores is demonstrated by the diffusion of fluorescein dye from the bottom of the membrane to the surface of the membrane using pulsed NIR light illumination. Fast dynamic response of fluorescein dye diffusion upon the illumination of NIR light suggests that the presented photothermal actuation approach could be applied to diverse biomedical applications such as a localized drug release system. [ABSTRACT FROM AUTHOR]

Intelligent or smart polymer materials are those which are either "active" or responsive to a variety of environmental stimuli, such as changes in pH, temperature, ionic strength or electric field, or the presence of a specific chemical substrate. A thermally sensitive polymer, poly(N-isopropylacrylamide) (PNIPAAm), has been of great interest because aqueous solutions of PNIPAAm undergo fast, reversible switching of hydrophilicity/hydrophobicity around 32 °C at their lower critical solution temperature (LCST) of about 29–38 °C (different with variations in their structure). PNIPAAm chains show an expanded conformation in water below the LCST because of strong hydration and change to the compact forms above the LCST by sudden dehydration; this is the reversible switching effect of hydrophilic to hydrophobic. These switchable materials may have wide applications in functional textiles, controllable drug release and special fibers. Electrospinning is a simple, convenient, and versatile technique for generating fibers with diameters that range from several micrometers to tens of nanometers. Herein, we report an electrospinning method to prepare nano PNIPAAm fiber and their thermal response was characterized. Based on the results, the diameters of the PNIPAAm nanofibers within the respective system were around 200 nm and beads-less; they were successfully prepared by an electrospinning method in all cases and the reversible switching with LCST (32 °C) feature was observed clearly in the fibers. [ABSTRACT FROM AUTHOR]

PNIPAAm‐grafted thermoresponsive hollow nano‐holed polymeric‐shell (HHPS) particles were fabricated from surface‐modified colloidal silica (CS) with poly(ethylene glycol) methyl ether‐3‐(triethoxysilyl)propyl isocyanate (PEGME‐IPTES) and 3‐(trimethoxysilyl) propyl methacrylate (MPS) as templates. The polymeric shells were then synthesized through a "grafting‐through" approach via surface‐initiated polymerization of N‐isopropyl acrylamide (PNIPAAm) using potassium persulfate (KPS) as an initiator, followed by the etching of CS with hydrofluoric acid to remove the CS core templates. CS nanoparticles and PEGME‐IPTES were presynthesized using tetraethoxysilane (TEOS) and distilled water in methanol with ammonia solution as a catalyst by the sol–gel method and using 3‐(triethoxysilyl) propyl isocyanate (IPTES) with poly(ethylene glycol) methyl ether (PEGME) in the presence of dibutyltin dilaurate. The chemical structures of bare and modified CS, PNIPAAm, PNIPAAm‐CS, and HHPS particles were characterized by FT‐IR and NMR spectroscopies. SEM and TEM images confirmed that the resulting HHPS particles had a significant number of interconnected nanoholes. To evaluate the LCST behaviors of HHPS particles, the transition of transmittance and the changes in particle diameter according to the temperature change were measured through UV‐vis spectroscopy, DLS, and microscopy. [ABSTRACT FROM AUTHOR]

Multi-arm block copolymers with stimuli-responsive behavior are a potential candidate in the field of nanoscience and nanotechnology due to their unique design, specific property-regulating ability and appealing applications. Here, tri-arm star diblock copolymers, poly(2-hydroxyethylacrylamide)-block-poly(N-isopropylacrylamide), P(HEAAm–b–NIPAAm) consisting of PHEAAm and PNIPAAm as inner and outer blocks were synthesized via two-step ATRP. The synthesized polymers were characterized using ATR-IR, 1H-NMR and GPC techniques. It is revealed that introducing a higher number repeating units (300) of HEAAm into copolymers could facilitate the formation of micelles in the cross-linked points and the occurrence of phase transition at higher temperatures. DLS measurements prove that tri-arm block copolymer with the lower number repeating units (50) of HEAAm core could not prevent random aggregation, whereas longer PHEAAm300 core produces ca. 200 nm aggregate steadily at the adjoining knot at above LCST. Lowering of UV–Vis absorbance at 40 °C proved the entrapment of Rhodamin B into PNIPAAm300 aggregates. Atomic force microscopy image of P(HEAAm300–b–NIPAAm21) shows a loop (network structure) with the terminal PNIPAAm consistent aggregate size ca. 237 ± 42 nm. (A) Schematic chemical structure of tri-arm poly(HEAAm-b-NIPAAm) diblock copolymer, (B) AFM image of nanoparticles formation, (C) nanoparticles distribution in aqueous solution at 34 °C (LCST) and at 50 °C, and (D) aggregation and expansion mechanism [ABSTRACT FROM AUTHOR]

In this study, thermo and pH-sensitive multifunctional poly (N-isopropylacrylamide-co- N,N'-methylenebisacrylamide, Poly(NIPAAm-co-MBA) - (N-4-amino-2-methylene-4-oxobutanoic acid, IAM) named as (PNM@IAM) core-shell microgels are synthesized by inverse microemulsion polymerization technique using two monomers, N-isopropylacrylamide (NIPAAm) and N-4-amino-2-methylene-4-oxobutanoic acid (IAM). The formation of the microgels are confirmed by 1H nuclear magnetic resonance (1H NMR) and attenuated total reflection fourier transform infrared (ATR-FTIR) spectra. The light transmittance study shows that the microgels prepared at different concentrations and pHs exhibit different physical properties. The phase transition temperature is increased with the addition of IAM. Dynamic light scattering (DLS) analysis reveals that the swelling of the microgels at basic environment is due to the deprotonation of the weak acid groups in IAM. The metal ion chelating test shows that the core-shell PNM@IAM could effectively absorb metal ions in highly basic environment. The absorption and release of heavy metal ions from aqueous solution could be controlled by adjusting the pH of the reaction environment. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide) PNIPAAm hydrogels were modified with a new azobenzene-containing co-monomer. In this work, light responsiveness as an additional functionality, is conceptualized to induce two phase transitions in the same material, which can be controlled by light. For a hydrogel with merely 2.5 mol% of this co-monomer, the lower critical solution transition temperature (LCST) was lowered by 12 °C (to 20 °C) compared to PNIPAAm (LCST at 32 °C), as analyzed by differential scanning calorimetry (DSC). The untreated unimodal endotherm split into a bimodal peak upon irradiation with UV-light, giving a second onset due to the switched (Z) isomer-rich regions, LCST*H2.5%-(Z) = 26 °C. On irradiation with 450 nm, leading to the reverse (Z) to (E) isomerization, the endotherm was also reversible. Thus, a photo-switchable hydrogel whose LCST and structure are tunable with the hydrophobicity-hydrophilicity of the (E) and (Z) isomeric state of azobenzene was obtained. The influence of the increase in the mol% of azoacrylate on the LCST was evaluated via DSC, in combination with NMR studies, UV-vis spectroscopy and control experiments with linear polymers. The large light-driven modulation of the LCST adds bistability in thermoresponsive hydrogels, which may open diverse applications in the field of soft robotics actuators. [ABSTRACT FROM AUTHOR]

Polymer based protein engineering provides an attractive strategy to endow novel properties to protein and overcome the inherent limitations of both counterparts. The exquisite control of site and density of attached polymers on the proteins is crucial for the bioactivities and properties of the protein-polymer bioconjugates, but is still a challenge. Collagen is the major structural protein in extracellular matrix of animals. Based on the advancements of polymer-based protein engineering, collagen bioconjugates has been widely fabricated and applied as biomaterials. However, the site-specific synthesis of well-defined collagen-polymer bioconjugates is still not achieved. Herein, a versatile strategy for the specific modification of N-terminal α-amino groups in collagen was developed. Firstly, all reactive amino groups of tropocollagen (collagen with telopeptides) were protected by succinic anhydride. Then, the telopeptides were digested to give the active N-terminal α-amino groups, which were subsequently attached with poly(N-isopropylacrylamide) (PNIPAAm) via "grafting from" method based on the atom transfer radical polymerization (ATRP). The site-specific N-terminal PNIPAAm modified succinylated collagen was prepared and its structure, thermal responsive behaviour, and properties was explored. [ABSTRACT FROM AUTHOR]

Colorectal cancer is the fourth most common cancer worldwide and the third most frequently diagnosed form of cancer associated with high mortality rates. Recently, targeted drug delivery systems have been under increasing attention owing to advantages such as high therapeutic effectiveness with a significant depletion in adverse events. In this report, we describe the biocompatible and thermoresponsive FA-conjugated PHEA-b-PNIPAAm copolymers as nanocarriers for the delivery of 5-FU. The block copolymers were obtained using RAFT (Reversible Addition–Fragmentation chain Transfer) polymerization and were characterized by methods such as SEC (Size Exclusion Chromatography), NMR (Nuclear Magnetic Resonance), UV–Vis (Ultraviolet–Visible), FT-IR (Fourier Transform Infrared) spectroscopy, and TGA (Thermogravimetric Analysis). Nanoparticles were formed from polymers with and without the drug-5-fluorouracil, which was confirmed using DLS (Dynamic Light Scattering), zeta potential measurements, and TEM (Transmission Electron Microscopy) imaging. The cloud points of the polymers were found to be close to the temperature of the human body. Eventually, polymeric carriers were tested as drug delivery systems for the safety, compatibility, and targeting of colorectal cancer cells (CRC). The biological evaluation indicated high compatibility with the representative host cells. Furthermore, it showed that proposed nanosystems might have therapeutic potential as mitigators for 5-FU-induced monocytopenia, cardiotoxicity, and other chemotherapy-associated disorders. Moreover, results show increased cytotoxicity against cancer cells compared to the drug, including a line with a drug resistance phenotype. Additionally, the ability of synthesized carriers to induce apoptosis and necrosis in treated CRC cells has been confirmed. Undoubtedly, the presented aspects of colorectal cancer therapy promise future solutions to overcome the conventional limitations of current treatment regimens for this type of cancer and to improve the quality of life of the patients. [ABSTRACT FROM AUTHOR]

Inspired by pufferfish, we developed an intelligent solar-driven "switch" photothermal hydrogel system PEG-PNIPAAm/Fe 3 O 4 hydrogel (PPFH). This design concept provides the possibility for promoting the widespread implementation of hydrogels-based solar evaporators in practical purification systems in the future, alleviating water shortages issues. [Display omitted] • This study developed an intelligent solar-driven hydrogel system PEG-PNIPAAm/Fe 3 O 4 hydrogel (PPFH). • The PPFH realizes superior efficient water uptake, high-density fog storage, and ultra-fast clean water release. • The porous network structure provides a continuous transporting path for water uptake-water release. • This study provides novel insights for the hydrogels-based solar evaporators in practical purification systems. Water shortage is becoming a huge challenge to mankind. Inspired by pufferfish, we developed an intelligent solar-driven "switch" hydrogel system PEG-PNIPAAm/Fe 3 O 4 hydrogel (PPFH). This hydrogel system is characterized by a uniform porous network structure formed by the integration of hydrophilic PEG, temperature-responsive PNIPAAm polymer and Fe 3 O 4 photothermal nanoparticles. The three-dimensional porous structure provides a higher surface area, offering more adsorption sites for water molecules. The interaction between PPFH and water primarily relies on the hydrogen bonding between the amide groups in PNIPAAm and water molecules, which enhances the hydration of the hydrogel network for rapidly water harvesting. However, when exposed to sunlight, the presence of Fe 3 O 4 nanoparticles causes the ambient temperature to rise rapidly above the LCST, the hydrogen bonding between molecules gradually weakens, while the hydrophobic interactions among the hydrophobic groups in PNIPAAm become stronger, causing the polymer chains to contract and water releasing. The fog capture performance of PPFH can reach up to 3.2 g g−1 , and under the irradiation of a sunlight (1 kW m−2), the captured water can be released within 8 min, and the water release efficiency reaches 94 %. This design concept provides the possibility for promoting the widespread implementation of hydrogels-based solar evaporators in practical purification systems in the future, alleviating water shortages issues. [ABSTRACT FROM AUTHOR]

Thermoresponsive polymers, with special emphasis on poly(N-isopropylacrylamide) (PNIPAAM) have been the focus of several investigations due to its potential applications in many fields of physical and polymer chemistry. PNIPAAM has a "lower critical solution temperature" at 32°C. The LCST can be finely tuned by copolymerization with hydrophobic or hydrophilic comonomers, and with a change of physical chemical parameters, such as ionic strength of the solution. We investigated the effect of polymer concentration on the LCST in two different solution environment, in pure water and in 50 mM NaCl solution with small-angle X-ray scattering (SAXS) of relatively low molecular mass polymers. We showed that the radius of gyration of the pNIPAAM chains increases with the addition of NaCl to the system due to the low level of specific adsorption of chloride ions on the polymer, whilst increasing the temperature causes a shrinkage of the polymer chains. Furthermore, by increasing the temperature the attractive interaction between the individual polymer chains is enhanced which turns into aggregation at the LCST. [ABSTRACT FROM AUTHOR]

Hydrogels are polymer networks swollen in water and, therefore, suitable for biomedical applications. For this purpose, hydrogels have to mimic the functionality and mechanics of natural tissues. In drug delivery, for example, the diffusion is crucial and can be controlled through targeted variation of the network mesh-size. In tissue engineering, on the other side, the mechanics plays a fundamental role and can be strengthened through the use of two interpenetrated polymer networks, realizing a double network, or with two dynamic motifs anchored in one common network, realizing a dual dynamic network (DDN). However, current knowledge encompasses mainly nonlinear rheological characterization of these networks. We intend to fill this gap and provide a systematic linear rheological study. To realize this strategy, we combine two supramolecular motifs in a common network, thereby realizing a comblike DDN with the ability to change the building blocks on demand. In our DDN, a tetra-poly(ethylene) glycol (pEG) (the first building block) is functionalized on each arm with two dynamic motifs: terpyridine capable of undergoing metal-complexation with different divalent metal ions, and a thermo-responsive unit consisting of poly(N-isopropylacrylamide) (pNIPAAm) (the second building block) that is capable of undergoing temperature-dependent nano-phase-separation. In particular, we change the molar mass of the tetra-pEG-terpyridine and the pNIPAAm grafted chains. In addition, we investigate two different metal ions that form complexes with the terpyridine. With this platform, we tune the elastic properties on demand, and we systematically study the structure–property relationships with oscillatory shear rheology in the linear regime. [ABSTRACT FROM AUTHOR]

We have analyzed the temperature-sensitive kinetic release of dye from a temperature-sensitive porous polymer film in which poly(N-isopropylacrylamide) (PNIPAAm) was functionalized. For the temperature-sensitive kinetic release, rhodamine 6G (RhG) was used as a substitute for a drug molecule. The releasing experiment was done by using a flow UV–Vis spectrophotometer. To support the temperature-sensitive kinetic release of RhG, temperature-dependent morphology of the porous film was studied by the scanning electron microscopy (SEM) and was compared to the temperature below and above the lower critical solution temperature (LCST) (~ 32.5 °C) of the PNIPAAm. The SEM images showed a higher rugged surface morphology of the porous PNIPAAm film with the increase in temperature above the LCST. An exponential increase in the RhG release was observed at 32–34 ºC, which is higher than the LCST of PNIPAAm. This means that the change of the pore surface from the coil to the globule state supports the temperature-sensitive release by the de-swelling of PNIPAAm in addition to the release by diffusion. The RhG release over time at different temperatures was also theoretically analyzed using the Korsmeyer–Peppas kinetic model. [ABSTRACT FROM AUTHOR]

The burst release of drugs limited the development of the thermo‐responsive hydrogels based on poly N‐isopropylacrylamide (NIPAAm) for application in drug delivery systems. To overcome this problem, the drug sulfadimethoxine (SDMO) was conjugated via amide bond to the PNIPAAm hydrogel instead of loaded into the system. Therefore, SDMO was modified using maleic anhydride to get N‐maleyl sulfadimethoxine (NMSDMO) and then utilized that to synthesize the sulfadimethoxine‐conjugated PNIPAAm hydrogel (P[NIPAAm‐co‐NMSDMO]). The resultant monomer was then grafted into the hydrogel network at different weight percentage through radical polymerization. The NMSDMO monomer and the P[NIPAAm‐co‐NMSDMO] hydrogels were fully investigated. The in vitro drug released displayed sustained release in pH 5 and 7.4 for 24 h. Hydrolysis of the amide bond causes the release rate and total amount of drug to be greatest at pH 5, as compared to pH 7.4. As a result, the P[NIPAAm‐co‐NMSDMO] hydrogel was an effective sustained drug delivery system. [ABSTRACT FROM AUTHOR]

In this study, polycaprolactone (PCL) macrobeads were prepared by an oil‐in‐water (o/w) emulsion solvent evaporation method with poly(vinyl alcohol) (PVA) as an emulsifier and conjugated to poly(N‐isopropylacrylamide) (PNIPAAm) to be used as cell carriers with noninvasive cell detachment properties (thermo‐response). Following previous studies with PCL‐PNIPAAm carriers, our objectives were to confirm the successful conjugation on homemade macrobeads and to show the advantages of homemade production over commercial beads to control morphological, biological, and fluidization properties. The effects of PCL concentration on the droplet formation and of flow rate and PVA concentration on the size of the beads were demonstrated. The size of the beads, all spherical, ranged from 0.5 to 3.7 mm with four bead categories based on production parameters. The morphology and size of the beads were observed by scanning electron microscopy to show surface roughness enhancing cell attachment and proliferation compared to commercial beads. The functionalization steps with PNIPAAm were then characterized and confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersion spectroscopy. PNIPAAm‐grafted macrobeads allowed mesenchymal stem cells (MSCs) to spread and grow for up to 21 days. By reducing the temperature to 25°C, the MSCs were successfully detached from the PCL‐PNIPAAm beads as observed with fluorescence microscopy. Furthermore, we validated the scalability potential of both macrobeads production and conjugation with PCL, to produce easily kilograms of thermo‐responsive macrocarriers in a lab environment. This could help moving such approaches towards clinically and industrially relevant processes were cell expansion is needed at very large scale. [ABSTRACT FROM AUTHOR]

Chitosan-based hydrogels possess numerous advantages, such as biocompatibility and non-toxicity, and it is considered a proper material to be used in biomedical and pharmaceutical applications. Vaginal administration of progesterone represents a viable alternative for maintaining pregnancy and reducing the risk of miscarriage and in supporting the corpus luteum during fertilization cycles. This study aimed to develop new formulations for vaginal administration of progesterone (PGT). A previously synthesized responsive chitosan-grafted-poly (N-isopropylacrylamide) (CS-g-PNIPAAm) was formulated in various compositions with polyvinyl alcohol (PVA) as external crosslinking agent to obtain pH- and temperature-dependent hydrogels; the hydrogels had the capacity to withstand shear forces encountered in the vagina due to its mechanism of swelling once in contact with vaginal fluids. Three different hydrogels based on grafted chitosan were analyzed via Fourier-transform infrared spectroscopy (FTIR), swelling tests, in vitro drug release, and bioadhesion properties by TA.XTplus texture analysis. A higher amount of PVA decreased the swelling and the bioadhesion capacities of the hydrogel. All hydrogels showed sensitivity to temperature and pH in terms of swelling and in vitro delivery characteristics. By loading progesterone, the studied hydrogels seemed to possess even higher sensitivity than drug–free matrices. The release profile of the active substance and the bioadhesion characteristics recommended the CS-g-PNIPAAm/PVA 80/20 +PGT (P1) hydrogel as a proper constituent for the vaginal formulation for progesterone administration. [ABSTRACT FROM AUTHOR]

Currently, the cells, which are urgently required for large-scale application in biomedical-related fields, harvested by traditional trypsin digestion are usually subject to repeated digestion, leading to a reduction of cell activity. In this study, poly (N-isopropylacrylamide) (PNIPAAm) was grafted onto the lignocellulose hollow fiber membranes (HFMs) with cerium ammonium nitrate (CAN) as the initiator to prepare thermosensitive HFMs, which was combined with a rotation system of culture (RSOC) to achieve dynamic culture and non-destructive harvesting of cells from the HFMs. The results of ATR-FTIR, elemental analysis, and SEM confirmed the successful preparation of PNIPAAm-grafted-HFMs, which also showed good biocompatibility to apply for cell culture carriers. In cooling detachment, the HFMs-0.01 group could completely detach the cells within 1 h with a cell separation efficiency of more than 90%. The laminin (LN) and fibronectin (FN) harvested by cooling detachment of P8 generation PC12 cells reached 0.0531 ± 0.0032 and 2.5045 ± 0.0001 pg/cell, respectively, which were significantly higher than that by trypsin digestion. In addition, the cells on the thermosensitive HFMs proliferated fastest in RSOC at 30 rpm with higher glucose consumption and lactate metabolism than in static conditions. Moreover, the cells that had dynamic detachment at 20 rpm had the highest cell density and activity. Therefore, the thermosensitive HFMs could be applied as cell culture carriers in RSOC for cell culturing at 30 rpm and harvesting at 20 rpm, which would provide considerable potential for large-scale cell culture in vitro., (© 2024 Wiley‐VCH GmbH.)

[Display omitted] • Ti 3 C 2 endows high thermal conductivity for CNF-C/Ti 3 C 2 /MMTex-PNI. • Switchable oleophilic ability is achieved over the CNF-C/Ti 3 C 2 /MMTex-PNI by temperature control. • The absorbed oil by CNF-C/Ti 3 C 2 /MMTex-PNI can be released within 10 min at 25 °C. • MMTex inhibits the oxidation of Ti 3 C 2 and enhances the mechanical properties of aerogel. Oil absorbed by aerogels was an effective method for achieving efficient oil–water separation. However, absorbent regeneration and recovery of oil were key issues that limited the practical application of aerogels. In this work, carboxylated cellulose nanofibers/Ti 3 C 2 /exfoliated montmorillonite/poly(N-isopropylacrylamide) (CNF-C/Ti 3 C 2 /MMTex-PNI) with switchable wettability was exploited through coordinately introduced exfoliated montmorillonite (MMTex), Ti 3 C 2 -MXene and thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) into carboxylated cellulose nanofibers (CNF-C) by a facile one-step hydrothermal and in-situ co-precipitation process. CNF-C/Ti 3 C 2 /MMTex-PNI was capable of reversible transformation between hydrophobic/oleophilic and hydrophilic/oleophobic, when the environmental temperature was above or below the lower critical solution temperature (LCST: 32 °C) of PNIPAAm. CNF-C/Ti 3 C 2 /MMTex-PNI could absorb oil within 5 s (54–98 g⋅g−1) under 45 °C and desorb oil within 10 min (recovery efficiency exceeds 78 %) at 25 °C. Moreover, the addition of MMTex inhibited the oxidation of Ti 3 C 2 , and Ti 3 C 2 /MMTex synergistically enhanced the mechanical properties (complete recovery under 60 % strain) and thermal stability of CNF-C/Ti 3 C 2 /MMTex/PNI. After 20 cycles, the absorption and desorption capacities of CNF-C/Ti 3 C 2 /MMTex/PNI for oils all decreased by 15 %. Moreover, the synthesis and fast-thermoresponsive mechanism for CNF-C/Ti 3 C 2 /MMTex/PNI were proposed. In conclusion, this work provides a new reference for the synthesis and recycling of smart aerogels for oil–water separation. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide) (PNIPAAm) hydrogel as a temperature-responsive polymer was prepared through controlled process using reversible addition fragmentation chain transfer (RAFT) polymerization. The hydrogel was then amino modified using a biocompatible polyamine i.e. spermine and next the antitumor cisplatin drug was conjugated to the modified hydrogel via pH-sensitive spermine linkage. This system had a pH dependency and temperature sensitivity at lower critical solution temperature (LCST). Cisplatin potentially is liberated from the carrier in the acidic environment. However, the release of cisplatin from this polymeric system is increased considerably around the transition temperature of the polymer. The drug release manner of the prepared hydrogel was determined at two pH values (5.5 and 7.4) and three temperatures (37, 40 and 42 °C) at different time intervals. The in vitro toxicity assessment was conducted on MCF-7 cell line which showed the system efficiency in killing breast cancer cells. [ABSTRACT FROM AUTHOR]

Polymer microgels, including those based on interpenetrating networks (IPNs), are currently vastly studied, and their practical applications are a matter of thriving research. In this work, we show the perspective for the use of polyelectrolyte IPN microgels either as scavengers or carriers of antiseptic substances. Here, we report that poly-N-isopropylacrylamide/polyacrylic acid IPN microgels can efficiently absorb the common bactericidal and virucidal compound benzalkonium chloride. The particles can form a stable aqueous colloidal suspension or be used as building blocks for soft free-standing films. Both materials showed antiseptic efficacy on the examples of Bacillus subtilis and S. aureus, which was approximately equal to the commercial antibiotic. Such polymer biocides can be used as liquid disinfectants, stable surface coatings, or parts of biomedical devices and can enhance the versatility of the possible practical applications of polymer microgels. [ABSTRACT FROM AUTHOR]

In the field of bioengineering, depending on the required application, the attachment of various biological entities to the biomaterial is either favored or needs to be prevented. Therefore, different surfaces modification strategies were developed in combination with the characteristics of the materials. The present contribution reports on the use of the specific surface property of a thermoresponsive polymer poly(N-isopropylacrylamide) pNIPAAM obtained by spin coating in combination with plasma treatment for tuning cell behavior on treated polymeric surfaces. Topographical information for the plasma-treated pNIPAAM coatings obtained by Atomic Force Microscopy (AFM) measurements evidenced a more compact surface for Ar treatment due to combined etching and redeposition, while for oxygen, a clear increase of pores diameter is noticed. The chemical surface composition as determined by X-ray Photoelectron Spectroscopy showed the specific modifications induced by plasma treatment, namely strong oxidation for oxygen plasma treatment illustrated by eight times increase of O-C=O contribution and respectively an increase of C-N/O=C-N bonds in the case of ammonia plasma treatment. Structural information provided by FTIR spectroscopy reveals a significant increase of the carboxylic group upon argon and mostly oxygen plasma treatment and the increase in width and intensity of the amide-related groups for the ammonia plasma treatment. The biological investigations evidenced that L929 fibroblast cells viability is increased by 25% upon plasma treatment, while the cell attachment is up to 2.8 times higher for the oxygen plasma-treated surface compared to the initial spin-coated pNIPAAM. Moreover, the cell detachment process proved to be up to 2–3 times faster for the oxygen and argon plasma-treated surfaces and up to 1.5 times faster for the ammonia-treated surface. These results show the versatility of plasma treatment for inducing beneficial chemical modifications of pNIPAAM surfaces that allows the tuning of cellular response for improving the attachment-detachment process in view of tissue engineering. [ABSTRACT FROM AUTHOR]

A new type of thermo-responsive polymer film is fabricated by the immobilization of poly(N-isopropylacrylamide) (PNIPAAm) to the pore-selectively carboxyl group functionalized honeycomb-patterned porous polystyrene film. To check the smartness of the film to the temperature change, the thermo-responsive release of rhodamine B (RB) above the lower critical solution temperature (LCST) (~32.5 °C) of the PNIPAAm was studied together with the change in morphology of the pore surface by the scanning electron microscopy (SEM). The thermo-responsive release was monitored by the UV–vis absorbance at a fixed wavelength of λmax of RB ~553 nm. The absorbance of λmax in the equilibrium state significantly increased with the increase in temperature above the LCST of PNIPAAm. The result of the SEM image showed a higher rugged surface morphology with a temperature above the LCST which indicates that the change in the pore surface from the coil to globule state supports the thermo-responsive swell and de-swelling state of PNIPAAm. Temperature-dependent RB release kinetics was performed at 25–40 °C. The result showed pseudo-first-order kinetics by the Korsmeyer-Peppas model. The transport exponent (n) is higher than 1 as ~6.66 above the LCST region which is indicating the temperature responsive release by the change in PNIPAAm morphology. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide) PNIPAAm hydrogels were modified with a new azobenzene-containing co-monomer. In this work, light responsiveness as an additional functionality, is conceptualized to induce two phase transitions in the same material, which can be controlled by light. For a hydrogel with merely 2.5 mol% of this co-monomer, the lower critical solution transition temperature (LCST) was lowered by 12 °C (to 20 °C) compared to PNIPAAm (LCST at 32 °C), as analyzed by differential scanning calorimetry (DSC). The untreated unimodal endotherm split into a bimodal peak upon irradiation with UV-light, giving a second onset due to the switched (Z) isomer-rich regions, LCST*H2.5%-(Z) = 26 °C. On irradiation with 450 nm, leading to the reverse (Z) to (E) isomerization, the endotherm was also reversible. Thus, a photo-switchable hydrogel whose LCST and structure are tunable with the hydrophobicity-hydrophilicity of the (E) and (Z) isomeric state of azobenzene was obtained. The influence of the increase in the mol% of azoacrylate on the LCST was evaluated via DSC, in combination with NMR studies, UV-vis spectroscopy and control experiments with linear polymers. The large light-driven modulation of the LCST adds bistability in thermoresponsive hydrogels, which may open diverse applications in the field of soft robotics actuators.

Aim: Colorectal cancer is an extremely aggressive form of cancer that often leads to death. Lactoferrin shows potential for targeting and treating colorectal cancer; however, oral delivery faces hurdles hampering clinical applications. We engineered dual-responsive lactoferrin nanostructured microbeads to overcome delivery hurdles and enhance drug targeting., Methods: The hydrophobic drug mesalazine (MSZ) was coupled to lactoferrin to form amphiphilic conjugate nanoparticles, dispersed in water. The lipid-soluble polyphenolic drug resveratrol (RSV) was then encapsulated into the hydrophobic core of LF-MSZ nanoparticles. To impart thermoresponsive properties, the dual-payload NPs were coupled with a PNIPAAm shell; finally, to further endow the nanoparticles with gastrointestinal resistance and pH responsiveness, the nanoparticles were microencapsulated into ionically cross-linked pectin-alginate beads., Results: The nanoparticles showed enhanced internalization and cytotoxicity against HCT colon cancer cells via LF-receptor-mediated endocytosis. Thermal triggering and tuned release were conferred by the temperature-sensitive polymer. The coatings protected the drugs from degradation. Orally delivered microbeads significantly reduced tumor burden in a mouse colon cancer model, lowering carcinoembryonic antigen and elevating antioxidant enzymes. Apoptotic pathways were stimulated, indicated by heightened Bax/Bcl2 ratio and caspase-3/9 expression., Conclusion: Overall, we propose the innovative lactoferrin nanostructured microbeads as a paradigm shift in oral colorectal cancer therapeutics.

Hydrogels are polymer networks swollen in water that are characterized by soft mechanics and high permeability. This makes them good candidates for separation and membrane technologies. The diffusion is controlled by the mesh size of the network, and this can be made tunable through the introduction of thermoresponsive polymers. However, this is still a developing field. To contribute to this development, a dual dynamic network is formed composed of four‐arm polyethylene glycol precursors in which each arm is functionalized with both a terpyridine moiety capable of forming reversible metal–ligand complexes along with branches of poly(N‐isopropylacrylamide) (pNIPAAm), which can be switched between expanded and collapsed states and therewith offers a path for switching the microscopic gel‐network mesh size, along with the macroscopic gel elasticity. The dually sensitive hydrogel has the capability of doubling its elastic modulus when going above the lower critical solution temperature (LCST) of pNIPAAm. In addition, the diffusive permeability of the hydrogel is switched upon change of temperature, whereby diffusants are trapped above the LCST of pNIPAAm. Moreover, it is possible to disassemble and reform the gel upon change of pH. With that, the hydrogel has potential application as a switchable and reversible membrane. [ABSTRACT FROM AUTHOR]

In the field of stimuli-responsive polymer research, poly-N-isopropylacrylamide (PNIPAAm) has been widely studied, because this material has unique properties which respond to temperatures near to that of the human body, approximately 36 °C. In this study, a nano-patterned PNIPAAm hydrogel was prepared using UV-irradiation and soft lithography. Chemical changes in the C–C double bonds of the PNIPAAm hydrogel were confirmed by FT-IR analysis. The thermal properties of the hydrogel were analyzed by differential scanning calorimetry (DSC), which confirmed its low critical solution temperature (LCST). The highest gel content of approximately 46% was achieved at 120 min UV-irradiation. The nano-patterned morphology of the PNIPAAm hydrogel exhibited temperature-dependent reversible shape transformation. This study shows that the reversible shape transformation of the PNIPAAm hydrogel was due to swelling and shrinking. [ABSTRACT FROM AUTHOR]

Abstract This paper presents fabrication and actuation methods for a soft microrobot with a hybrid structure composed of soft microactuators and a rigid supporting body. This hybrid structure enables actuation of the microrobot with independent driving of multiple actuators to provide complex movement like that of living microorganisms. We use the temperature-responsive hydrogel poly(N-isopropylacrylamide) (PNIPAAm) as a soft microactuator. PNIPAAm swells with water at low temperature but shrinks at high temperature. This volume change thus allows PNIPAAm to be used as an actuator by controlling its temperature. We successfully fabricated the microrobot with its soft-rigid hybrid structure composed of PNIPAAm and rigid photoresist using a multilayered microfabrication process. In addition, we used a sacrificial layer process to release the fabricated microrobot from the substrate to allow it to move freely. To actuate the microrobot, we mixed PNIPAAm with graphene, which has a high photothermal conversion efficiency. The temperature of the soft actuator when mixed with graphene can be increased by irradiating it with light. Therefore, actuation of the microrobot is achieved by sequentially irradiating the microactuators with focused light. We present the fabrication, release and partial actuation of the microrobot to demonstrate the feasibility of the proposed microrobot with the soft-rigid hybrid structure in this paper.

In photodynamic therapy (PDT), the inherent physicochemical properties of a photosensitizer (PS) critically affect its biodistribution and therapeutic outcome as well as side effect. Here, we developed a PS-polymer conjugate displaying isothermal hydrophilic-to-hydrophobic phase transition in response to tumorous acidic pH. The polymer backbone was poly(N -isopropylacrylamide (NIPAAm)/2-aminoisoprpylacrylamide (AIPAAm)) (P(NIPAAm/AIPAAm)), which shows lower critical solution temperature (LCST) of 30 °C. The amine groups in its side chains were converted to hydrophilic acid-labile 2-propionic-3-methylmaleic (PMM) amides, forming poly(NIPAAm/AIPAAm-PMM). The conjugation of PMM moieties drastically increased the LCST of the polymer to 40 °C and displayed hydrophilic character to minimalize unspecific interaction of PS-P(NIPAAm/AIPAAm-PMM) in bloodstream, diminishing potential photosensitivity. The detachment of PMM at tumorous pH lowered the LCST to that of original P(NIPAAm/AIPAAm), permitting hydrophilic-to-hydrophobic transition at a physiological temperature (37 °C). This pH-responsive isothermal phase transition facilitated interaction with the cultured cancer cells, accomplishing 8.1 times-enhanced cellular uptake and strong phototoxicity in a tumorous pH-selective manner. Even in subcutaneous tumor models, our polymer conjugates exhibited efficient tumor accumulation and significantly augmented PDT effect without inducing unfavorable photochemical toxicity to the skin. This study offers a novel concept of PS delivery systems targeting tumorous pH by the use of isothermal phase transition. Unlabelled Image • pH-responsive isothermal phase transition potentiates photosensitizer delivery. • The polymer could target mild acidic extracellular pH in a tumor. • Hydrophilicity prevented unfavorable interaction with serum components. • Hydrophobicity facilitated cellular uptake and augmented therapeutic effect. [ABSTRACT FROM AUTHOR]

Targeted and controlled drug delivery employing “smart materials” is a widely investigated field, within which stimuli-responsive polymers, particularly those which are thermo-responsive, have received considerable attention. Thermo-responsive polymers have facilitated the formulation of in situ gel forming systems which undergo a sol-gel transition at physiological body temperature, and have revolutionized the fields of tissue engineering, cell encapsulation, and controlled, sustained delivery of both drugs and genes. However, the use of single thermo-responsive polymers in the creation of these systems has posed numerous problems in terms of physico-mechanical properties, such as poor mechanical strength, high critical gelation concentrations (CGC) resulting in increased production costs and solutions that are too viscous, toxicity, as well as gelation temperatures that are incompatible with physiological body temperatures. Hybridization of these thermo-responsive polymers with other polymers has therefore been employed, resulting in the creation of tailor-made drug delivery systems that have optimal gelation temperatures and concentrations, ideal viscosities and improved gel strengths. This article reviews various thermo-responsive polymers that have been employed in the formulation of thermo-gelling systems. Special attention has been given to the hybridization of each of these polymers, the resulting systems that have been created, and their biomedical applications.

This contribution describes the fabrication of super‐macroporous cryogels comprising an interpenetrating network of biodegradable dextran and temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAAm) segments. Cryogels were prepared from nonmodified dextran and N‐isopropylacrylamide (NIPAAm) via cryogenic treatment of their aqueous solutions and subsequent irradiation with Ultraviolet light. The weight ratio of the two precursors was varied in order to find out the proper conditions for producing cryogels of high gel fraction yield and favorable physico‐mechanical properties. Temperature‐responsive behavior and enhanced elastic modulus were established for cryogel materials containing ≥50 wt% PNIPAAm. Scanning electron microscopy study revealed an open‐porous structure of cryogels below and above the temperature of volume phase transition. Such morphology featured a very quick response of the material to temperature changes. The capability of dextran/PNIPAAm cryogels for instant release of water‐soluble substances was demonstrated as well. [ABSTRACT FROM AUTHOR]

This study demonstrates the fabrication of thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) thin films using the initiated PECVD (i-PECVD) method, in which the initiator tert-butyl peroxide was used together with the monomer NIPAAm. The deposition rates, wettability properties, and the low critical solution temperature (LCST) of i-PECVD deposited PNIPAAM were compared with those of classical continuous wave and pulsed PECVD techniques without TBPO. The effect of plasma power, plasma operation mode, substrate temperature and the presence of initiator on the deposition rate and wettability properties of PNIPAAm thin films were investigated. The results showed that it was possible to tune the deposition rate and wettability properties of PNIPAAm thin films by changing the PECVD parameters. The highest deposition rate (47.9 nm/min) and the largest contact angle difference (18.3°) depending on the temperature were obtained using the i-PECVD method. The LCST value of i-PECVD-PNIPAAm was able to be tuned between 31 and 34 °C. Such value was dependent on the presence and amount of the initiator. On the basis of these results, the i-PECVD method can be considered as the most proper approach for producing of PNIPAAm with desired properties. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide) (PNIPAAm) hydrogel with temperature-sensitive properties can be potentially applied in smart response area. However, poor mechanical and non-conductive characteristic have greatly restricted its widespread application. In this work, PNIPAAm composite hydrogels containing graphene aerogel (GA) and graphene oxide (GO) were prepared via vacuum-assisted backfilling and in-situ polymerization. After an introduction of 0.29 wt% GA and 0.09 wt% GO, the compressive strength and modulus of PNIPAAm hydrogel increase by 100% and 582%, respectively. Moreover, the ternary composite hydrogel has a good electric conductivity, reaching up to 0.52 S/m, due to the electro-conductive network of GA. Combining the good conductivity and itself temperature-sensitive property of PNIPAAm, a smart switch was assembled and could switch off automatically under a high voltage, which has potential applications in sensor area. [ABSTRACT FROM AUTHOR]

Thermo- and pH-responsive polyrotaxane (PR)-based triblock copolymers were synthesized by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide initiated with polypsudorotaxanes which were presynthesized from bromine end-capped poly(ethylene glycol)/poly(propylene glycol) with cyclodextrins in the presence of CuBr/HMDETA under near physiological conditions. The triblock copolymers were characterized by 1H NMR, FT-IR, GPC (gel permeation chromatography) analyses. Thermo- and pH-responsive behavior evaluated by UV–Vis spectroscopies, DLS (dynamic light scattering), and TEM (transmission electron microscopy) images showed that its lower critical solution temperature (LCST) was slightly increased with increasing pH values due to hydroxyl groups of cyclodextrin depending on pH values. [ABSTRACT FROM AUTHOR]

Novel biodegradable terpolymer poly (1,3‐trimethylene carbonate‐b‐(l‐lactide‐r‐glycolide)) grafted with poly(N‐isopropylacrylamide) (PTLG‐PNIPAAm) is prepared by plasma‐induced polymerization. The experimental results show that PNIPAAm segments of samples have a dramatic effect on surface layer structure and cell behavior of PTLG‐PNIPAAm. The thickness of PNIPAAm layer on PTLG surface increases rapidly from 50 nm to 1 µm with the molecular weight of samples increasing. Cell toxicity analysis indicates that PTLG‐PNIPAAm possesses good cytocompatibility to human adipose‐derived stem cells (hADSCs). For cell adhesion and detachment process on modified surface, the "hook and loop" process is proposed to understand the cell adhesion on modified surface with coiled conformation PNIPAAm segments at 37 °C, and then the cell sheet detached from surface spontaneously due to the conformation of PNIPAAm segments extends below its lower critical solution temperature. The research demonstrates that with increasing thickness of the PNIPAAm layer on PTLG surface, the hADSCs with well cell viability presents rapider thermal‐responsive detachment behavior. Therefore, the surface modification of biodegradable PTLG with stimuli‐sensitive functional PNIPAAm is an efficacious route for further application in stem cell culture and tissue engineering stent. [ABSTRACT FROM AUTHOR]

Temperature-responsive liquid chromatography (TRLC) offers an alternative for retention and selectivity optimisation in HPLC. This approach thereby exploits temperature gradients on stimuli-responsive stationary phases and forfeits the necessity for solvent gradients, allowing analyses to be performed using aqueous mobile phases. Consequently, it can be employed as a green alternative to reversed-phase separations. However, current production to obtain temperature-responsive columns inherently require dedicated column packing processes with polymer-modified particles. To facilitate the development of temperature-responsive phases, a flow-through modification procedure was developed allowing on-column modification of aminopropyl silica columns. Three columns were manufactured using this novel flow-through approach, which achieved identical column efficiencies compared to existing TRLC column. Demonstrating the possibility of bypassing the dedicated packing processes without losing efficiency. Additionally, it was observed that flow-through produced columns yielded higher retention at elevated temperatures despite their reduced carbon load. Further investigation of the carbon load revealed the presence of stationary phase gradients, whose influence was studied via novel developed retention experiments, which revealed a negligible change reduction in retention upon a change of polymer modification from 19.8% to 14.5%. However, further decrease from 14.5% to 12.3% resulted in a larger change. Interestingly, a further enhancement in apparent plate numbers was observed when operating the column under a reversed flow, yielding an increasing stationary phase gradient. This on-column modification procedure demonstrates the potential for modification of existing (commercial) packed columns to achieve temperature-responsive phases without loss of efficiency or retention. Thus, not only facilitating accessibility to temperature-responsive phases, but also aiding with development of further generations of temperature-responsive phases by removing the need for packing optimisation. Additionally, a novel experiment was set up to easily investigate the effect of inhomogeneous stationary phases retention. [Display omitted] • Novel on-column procedure for temperature-responsive stationary phases without loss of efficiency or retention. • Flow-through modification procedure removes the need for in-house packing setups. • Presence of stationary phase gradient capable to further improve column efficiency. • Flow-through modification allows for production of temperature-responsive columns from pre-packed columns. [ABSTRACT FROM AUTHOR]

Tooth formation during embryogenesis is controlled through a complex interplay between mechanical and chemical cues. We have previously shown that physical cell compaction of dental mesenchyme cells during mesenchymal condensation is responsible for triggering odontogenic differentiation during embryogenesis, and that expression of Collagen VI stabilizes this induction. In addition, we have shown that synthetic polymer scaffolds that artificially induce cell compaction can induce embryonic mandible mesenchymal cells to initiate tooth differentiation both in vitro and in vivo. As embryonic cells would be difficult to use for regenerative medicine applications, here we explored whether compressive scaffolds coated with Collagen VI can be used to induce adult bone marrow stromal cells (BMSCs) to undergo an odontogenic lineage switch. These studies revealed that when mouse BMSCs are compressed using these scaffolds they increase expression of critical markers of tooth differentiation in vitro, including the key transcription factors Pax9 and Msx1. Implantation under the kidney capsule of contracting scaffolds bearing these cells in mice also resulted in local mineralization, calcification and production of dentin-like tissue. These findings show that these chemically-primed compressive scaffolds can be used to induce adult BMSCs to undergo a lineage switch and begin to form dentin-like tissue, thus raising the possibility of using adult BMSCs for future tooth regeneration applications.

Abstract The most challenging task in the preparation of magnetic poly(N-isopropylacrylamide) (Fe3O4-PNIPAAm) nanocomposites for bio-applications is to maximise their reactivity and stability. Emulsion polymerisation, in situ precipitation and physical addition were used to produce Fe3O4-PNIPAAm-1, Fe3O4-PNIPAAm-2 and Fe3O4-PNIPAAm-3, respectively. Their properties were characterised using scanning electron microscopy (morphology), zeta-potential (surface charge), thermogravimetric analysis (stability), vibrating sample magnetometry (magnetisation) and dynamic light scattering. Moreover, we investigated the antibacterial effect of each nanocomposite against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Both Fe3O4-PNIPAAm-1 and Fe3O4-PNIPAAm-2 nanocomposites displayed high thermal stability, zeta potential and magnetisation values, suggesting stable colloidal systems. Overall, the presence of Fe3O4-PNIPAAm nanocomposites, even at lower concentrations, caused significant damage to both E. coli and S. aureus DNA and led to a decrease in cell viability. Fe3O4-PNIPAAm-1 displayed a stronger antimicrobial effect against both bacterial strains than Fe3O4-PNIPAAm-2 and Fe3O4-PNIPAAm-3. Staphylococcus aureus was more sensitive than E. coli to all three magnetic PNIPAAm nanocomposites.

Smart hydrogels comprising guar gum (GG) and poly(N-isopropylacrylamide) (PNIPAAm) cross-linked using a non-toxic cross-linker, tetraethyl orthosilicate, have been designed to explore the sustained release of an anticancer drug, 5-fluorouracil (5FU). Hydrogels containing preformed solid inclusion complexes (IC) of 5FU in β-cyclodextrin (β-CD) were designed to regulate the drug delivery. The formation of true 5FU/β-CD ICs was affirmed from different spectroscopic techniques. The DSC studies of the hydrogels revealed that the thermosensitivity of PNIPAAm is retained in the resultant hydrogels, also corroborated from the swelling measurements. The rate of 5FU release from the hydrogels containing the IC was significantly prolonged in comparison with those containing the free drug. Higher amounts of GG in the matrix led to slower release of drug. The preliminary kinetics of drug release indicated the collective influence of β-CD and GG content on the polymer relaxation process which was key in sustaining the drug delivery. Release studies in simulated gastric (SGF) and intestinal (SIF) fluids showed less than 10% of 5FU release during the initial 2 h in SGF and an increased release in SIF. Thus, the developed smart hydrogels can be utilized as potential candidates for sustained oral delivery of 5FU to the intestine. [ABSTRACT FROM AUTHOR]

A multiparameter fiber optic biosensor for continuous determination of cholesterol and glucose was developed. This sensor was based on poly(N-isopropylacrylamide) (PNIPAAm)-immobilized glucose oxidase (GOx) complex (PIGC) and immobilized cholesterol oxidase (COD). The immobilized COD catalysis to the oxidation of cholesterol and PIGC catalysis to the oxidation of glucose could be performed at different temperatures. Therefore, the sensor could detect cholesterol and glucose continuously by changing temperature. The optimal detection conditions for glucose were achieved with pH 6.5, 30 °C, and 10 mg GOx (in 100-mg carrier), and those for cholesterol were achieved with pH 7.5, 33 °C, and 25 mg COD (in 250-mg carrier). The sensor has the cholesterol detection range of 20–250 mg/dL and the glucose detection range of 50–700 mg/dL. This biosensor has outstanding repeatability and selectivity, and the detection results of the practical samples are satisfactory. [ABSTRACT FROM AUTHOR]

Due to the availability and timeliness of autologous cells, the in vitro cultivation and expansion of cells in large scale is very necessary before clinical treatments. However, traditional cell-harvesting methods including machinery scraper and enzymatic method would produce irreversible damage for treated cells. The appearance of intelligent temperature-responsive cell culture surfaces can solve the problem. Therefore this review focuses on the development of temperature-responsive surfaces based on poly(N-isopropylacrylamide) in recent years and the impact on cell adsorption and desorption processes. [ABSTRACT FROM AUTHOR]

In this study, varying amounts of NIPAAm and an ionic liquid (IL), namely 1-vinyl-3-isopropylimidazolium bromide ([ViPrIm]+[Br]−), have been used to synthesize hybrid hydrogels by radical emulsion polymerization. Amounts of 70/30%, 50/50%, 30/70%, 15/85% and 5/95% (wt/wt) of PIL/pNIPAAm were used to produce hybrid hydrogels as well as the parental hydrogels. The adhesive strength was investigated and evaluated for mechanical characterization. Thermal properties of resulting hydrogels have been investigated using differential scanning calorimetry (DSC) in a default heating temperature range (heating rate 10 K min−1). The presence of poly ionic liquids (PIL) in the polymer matrix leads to a moved LCST (lower critical solution temperature) to a higher temperature range for certain hybrid hydrogels PIL/pNIPAAm. While pNIPAAm exhibits an LCST at 33.9 ± 0.3°C, PIL/pNIPAAm 5/95% and PIL/pNIPAAm 15/85% were found to have LCSTs at 37.6 ± 0.9°C and 52 ± 2°C, respectively. This could be used for controlled drug release that goes along with increasing body temperature in response to an implantation caused infection.

In this article, we present a semi-interpenetrating network (IPN) hydrogel of reasonable size with improved swelling behavior. The semi-IPN is composed of N-isopropylacrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid. Porosity was generated chemically by a surfactant-based template method. The swelling behavior was measured after an abrupt change of the temperature to 25 °C or 40 °C or after an abrupt change of the salt concentration of the aqueous medium surrounding the hydrogel samples. A set of static swelling degrees was determined from swelling measurements in salt solutions of varying concentrations and at different temperatures. Introducing porosity to the semi-IPN decreases the swelling times for most measurements while the sensor and actuator characteristics of the hydrogel found in previous studies are preserved. Additionally, we propose theoretical assumptions and explanations regarding the differences in the swelling kinetics of the porous and the nonporous semi-IPN and deduce implications for sensor and actuator applications.

Novel polypseudorotaxanes (PPR) based on poly(N-isopropylacrylamide) (PNIPAAm) and acrylamide-γ-cyclodextrin (AγCD) are successfully synthesized. AγCD gives rise to sliding crosslinking systems and influences the thermoresponsive and swelling behavior of PNIPAAm hydrogels. Namely, their lower critical solution temperature (LCST) can be tuned up to 38°C, thus making the resulting materials of great interest in biomedical applications. Also, AγCD influences the thermal and mechanical properties of hydrogels, by affecting the Tg and E modulus values.

Abstract: Atom transfer radical polymerization (ATRP) is one of the most powerful methodologies for polymerization. Well‐controlled ATRP of N‐isopropylacrylamide (NIPAAm) could be obtained in organic‐water mixture solvent with conventional metal catalyst/ligand catalyst system. However, the mixture solvent is not suitable for copolymerization of NIPAAm with hydrophobic monomers. Moreover, further purification of metal was required for biomedical polymerization. Here, poly(N‐isopropylacrylamide) (PNIPAAm) is synthesized by visible light–induced metal‐free ATRP using a photoredox catalyst. PNIPAAm is obtained with high conversion and controlled molecular weight with low dispersity. Moreover, poly(N‐isopropylacrylamide)‐block‐poly(tert‐butyl methacrylate) (PNIPAAm‐b‐PMAA) block copolymer can be synthesized by such metal‐free ATRP. PNIPAAm‐b‐PMAA can be obtained by following hydrolysis. [ABSTRACT FROM AUTHOR]