Thermo-responsive gelatin-functionalized PCL film surfaces for improvement of cell adhesion and intelligent recovery of gene-transfected cells

Efficient local gene transfection on a tissue scaffold is dependent on good cell-adhesion characteristics. In this work, the thermo-responsive gelatin-functionalized polycaprolactone (PCL) films were proposed for improvement of cell adhesion and intelligent recovery of gene-transfected cells. Functional copolymer brushes (PCL-g-P(NIPAAm-co-MAAS)) were first prepared via surface-initiated ATRP of N-isopropylacrylamide (NIPAAm) and methacrylic acid sodium salt (MAAS) from the initiator-funcationalized PCL surfaces. The pendant carboxyl end-groups of the PCL-g-P(NIPAAm-co-MAAS) surface were subsequently coupled with gelatin via carbodiimide chemistry to produce the thermo-responsive gelatin-functionalized PCL surface. The thermo-responsive gelatin-functionalized PCL film surface can improve cell adhesion and proliferation above the LCST of P(NIPAAm) without destroying cell detachment properties at lower temperatures. The dense transfected cells can be recovered simply by lowering culture temperature. The thermo-responsive gelatin-functionalized PCL films are potentially useful as intelligent adhesion modifiers for directing cellular functions within tissue scaffolds.     

Adsorption of Binary Liquid Crystals onto Cellulose Membrane for Thermo-Responsive Drug Delivery

A thermo-responsive membrane was developed by adsorbing the binary liquid crystals (LC) onto the cellulose nitrate membrane. The binary LC mixture is consisted of 36% cholesteric oleyl carbonate (COC) and 64% cholesteryl nonanoate (CN). The physico-chemical and the thermo-responsive properties of this binary LC adsorbed-membrane were examined. The results indicate that the adsorption behavior of binary LC mixture on the cellulose membrane was quick and reached to the equilibrium about 10 min, and linearly correlated with the increase of LC concentration used. The hydrophilic membrane was hydrophobicized after adsorption of binary LC mixture. The focal conic fan textures of binary LC mixture were observed from the surface of cellulose membrane. Due to the obedience and reproducibility of the binary LC used, the binary LC mixture-adsorbed membrane continuously exhibited an on-off thermo-responsive sensitivity to control the drug penetration.     

Temperature-responsive stationary phase utilizing a polymer of proline derivative for hydrophobic interaction chromatography using an aqueous mobile phase

A new method of chromatography is proposed, utilizing a thermo-responsive polymer carrying an amino acid ester residue for the stationary phase of high-performance liquid chromatography (HPLC). We have been investigating the new concept of chromatography, a temperature-responsive chromatography, using temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm)-modified surface for HPLC with a constant aqueous media as the mobile phase. In this study, we designed and synthesized thermo-responsive poly(acryloyl-L-proline methyl ester) and its copolymer with N-isopropylacrylamide (NIPAAm). Homopolymers of acryloyl-L-proline methyl ester and copolymer were prepared by the reaction of radical telomerization. These polymers underwent a reversible phase transition from water-soluble forms into aggregates by changing the temperature, similar to PNIPAAm. The surface properties and functions of stationary phases modified with poly(acryloyl-L-proline methyl ester) were controlled by the external temperature. In the chromatographic system, we separated steroids and amino acids with a variety of hydrophobicities using a sole aqueous mobile phase. In contrast to a PNIPAAm-modified surface, a poly(acryloyl-L-proline methyl ester)-modified surface showed a greater affinity for hydrophobic amino acids.     

Novel calcium-alginate capsules with aqueous core and thermo-responsive membrane

Novel calcium-alginate (Ca-alginate) capsules with aqueous core and thermo-responsive membrane are successfully prepared by introducing a co-extrusion minifluidic approach, and the thermo-responsive gating characteristics of Ca-alginate capsule membranes embedded with poly(N-isopropylacrylamide) (PNIPAM) microspheres are investigated systematically. The experimental results show that the prepared Ca-alginate capsules are highly monodisperse, and the average diameter and membrane thickness of Ca-alginate capsules are about 2.96 mm and 0.11 mm respectively. The Ca-alginate capsule membranes exhibit desired thermo-responsive gating property. With increasing the content of PNIPAM microspheres embedded in the Ca-alginate capsule membranes, the thermo-responsive gating coefficient of the capsule membranes increases simply. When solute molecules diffuse through the capsule membrane, the thermo-responsive gating coefficient is significantly affected by the molecular weight of solute molecules.     

Preparation and characterization of dual stimuli-responsive microcapsules with a superparamagnetic porous membrane and thermo-responsive gates

A novel dual stimuli-responsive microcapsule with a superparamagnetic porous membrane and linear-grafted poly(N-isopropylacrylamide) (PNIPAM) gates in the membrane pores is successfully prepared and characterized. Oleic acid (OA)-modified Fe₃O₄ nanoparticles are embedded into the polyamide microcapsule membrane during interfacial polymerization process, and then plasma-induced grafting polymerization is used to graft PNIPAM into the pores of microcapsule membranes. The prepared microcapsule membranes exhibit time-independent superparamagnetic property with good magnetic-responsive ability, and satisfactory thermo-responsive controlled-release property due to the thermo-responsive swollen/shrunken property of PNIPAM gates grafted on the inner pore surface of the microcapsule membranes.     

Temperature dependent synthesis of micro- and meso-porous silica employing the thermo-responsive polymer of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) as structure-directing agent

Temperature dependent synthesis of micro- and meso-porous silica employing the thermo-responsive homopolymer poly(N-isopropylacrylamide) or the random copolymer poly(N-isopropylacrylamide-co-acrylic acid) as structure-directing agent (SDA) and Na₂SiO₃ as silica source is proposed. The thermo-responsive character of the SDA provides the advantages including (1) temperature dependent synthesis of microporous silica, hierarchically micro-mesoporous silica, and mesoporous silica just by changing the aging temperature below or above the low critical solution temperature of the thermo-responsive SDA, and (2) elimination of the thermo-responsive SDA from silica matrix by water extraction. The synthesis mechanism is discussed, and the effect of the aging temperature and the weight radio of SDA/Na₂SiO₃ on the synthesis of micro- and meso-porous silica are studied. Microporous silica, hierarchically micro-mesoporous silica and mesoporous silica with the surface area at 3.5−9.0 × 10² m²/g and the pore volume at 0.28−1.13 cm³/g and the average pore size ranging from 1.1 to 9.0 nm are synthesized. The strategy affords a new and environmentally benign way to fabricate porous silica materials, and is believed to bridge the gap between the synthesis of microporous and mesoporous silica materials.     

A method for an approximate determination of a polymer-rich-domain concentration in phase-separated poly(N-isopropylacrylamide) aqueous solution by means of confocal Raman microspectroscopy combined with optical tweezers

The paper demonstrates that a confocal Raman microspectroscope combined with optical tweezers is a promising technique to estimate polymer concentration in polymer-rich domain in phase-separated-aqueous polymer solution. The sample polymer is poly-(N-isopropylacrylamide) (PNIPAM) that is well-known as a representative thermo-responsive polymer. Optical tweezers can selectively trap the polymer-rich domain at the focal point in non-contact and non-intrusive modes. Such situation allows us to determine polymer concentration in the domain, which has been unclear due to a lack of appropriate analytical technique. It is applicable for a variety of other thermo-responsive polymers.     

Effect of core-shell micelle formation on the redox properties of phenothiazine-labeled poly(ethyl glycidy ether)-block-poly(ethylene oxide)

Redox properties of phenothiazine-labeled poly(ethyl glycidy ether)-block-poly(ethylene oxide) (PT-EGE_n-b-EO_m) are reversibly changed by core-shell micelle formation. In the temperature range higher than the critical micellization temperature (cmt), the anodic potential of PT group positively shifts and concomitantly its anodic current decrease, or levels off compared to those of the reference polymer PT-EO_m without the thermo-responsive EGE_n segment. The former alteration is caused by incorporation of hydrophobic PT groups into a core of the micelle and the latter by the decrease in the diffusion coefficient of PT groups due to formation of the core-shell micelles. The cmt value and the temperature-dependent alteration in the redox properties strongly depend on the polymer structure, especially the length of thermo-responsive EGE_n segment. The electrochemically determined hydrodynamic radii of the polymer aggregates seem to be overestimated, compared to the values reported for the aggregates of other thermo-responsive polymers with similar molecular weights, implying the presence of electrochemically inactive PT groups in the copolymers having longer thermo-responsive segments.     

基于多肽和温敏聚合物的光交联囊泡的制备及表征

It is an important challenge to balance the degradability and stability of polymer vesicles. We report a thermo-responsive vesicle based on poly[(N-isopropyl acrylamide-stat-7-(2-methacryloyloxyethoxy)-4-methylcoumarin)-b-(L-glutamic acid)] [P (NIPAM₄₅-stat-CMA₅)-b-PGA₄₂] diblock copolymer, which was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP). The membrane of the vesicle consists of thermo-responsive PNIPAM and photo-cross-linkable PCMA. The PGA chains in the vesicle coronas can colloidally stabilize the vesicles in water and can be postfunctionalized for further applications. Transmission electron microscopy and dynamic light scattering studies confirmed the formation of vesicles. Overall, we prepared a new functional thermo-responsive vesicle based on polypeptide copolymers that may be used as nanocarriers for the facile loading of a range of molecules in future.     

Thermo-responsive Hercosett/Poly(N-isopropylacrylamide) films: a new, fast, optically responsive coating

Poly(N-isopropylacrylamide) (PNIPAM) is a common thermo-responsive, water-soluble polymer, while Hercosett is a cationic resin commonly employed in the paper industry. In this paper, Hercosett? and poly(N-isopropylacrylamide) (PNIPAM) nanoparticles were used to prepare composite films that show thermo-responsive behavior and swelling–shrinking properties in water. First, size-controlled PNIPAM hydrogel nanoparticles were synthesized. These were then embedded within a matrix of the cationic resin Kymene 577H by film casting. The distribution of nanoparticles in the resin film was investigated. The thermo-responsive properties of the as-synthesized PNIPAM hydrogel nanoparticles and of the composite films were characterized together with the repeatability of the swelling–shrinking cycles. The presence of nanoparticles endowed the film with highly enhanced water retention (in comparison with resin-only films) and, most importantly, thermo-responsiveness. A very fast optical and morphological response was in fact observed. Due to the dual (optical and morphological) response, this new system is suitable for applications in optical or morphological actuation and gating.     

Temperature-responsive smart surfaces via rise-and-descent transition: Attachability,durability, and fast sweating

Smart surfaces containing thermo-responsive hydrogels have been investigated for several decades, but the development of mechanically durable and versatile surfaces that can undergo distinct property changes remains a challenging task. Herein, we prepare smart surfaces showing reversible changes in micro-scale roughness, which are attachable to various polymeric substrates. The hydrogel microphase located between silicone phases responsively rise and descend (volcanic-terrain-mimetic transition); as a result, the surface properties reversibly swing from those of the hydrophobic silicone-like ones to those of the wet hydrogel ones. The durability of these surfaces resembles that of silicone, while their fast water release characteristics allow the utilization of the studied materials in self-aligning and artificial sweating applications. The release of the drug molecules loaded into the hydrogel phase is controlled by varying the temperature and composite structure. Thus, the fabricated versatile surfaces utilizing the volume transition of thermo-responsive hydrogels can meet the requirements of various future applications.     

Surface forces and friction tuned by thermo-responsive polymer films

Thermo-responsive polymer films have enabled the development of various functional surfaces with switchable interfacial properties. Assessing the surface forces and friction on such films is of paramount importance. On the one hand, it allows us to extract a great deal of information on the interfacial properties of the films, e.g., adhesiveness and lubricity, and how they could be tuned using different stimuli. On the other hand, surface force measurements complement other thin-film analysis methods, e.g., ellipsometry, to better perceive the correlation between the molecular properties of the polymer chains and the interfacial properties of the film. On this basis, we will, herein, provide a concise review of some recent studies on surface forces and friction tuned by thermo-responsive polymer films. This outline comprises a summary of several research works addressing the effects of temperature, solvent composition, and salts on surface forces and friction. In the end, we briefly discuss a few select studies in which the regulation of surface forces by thermo-responsive polymers is examined with an emphasis on the potential applications.     

Preparation of thermo-responsive polymer brushes on hydrophilic polymeric beads by surface-initiated atom transfer radical polymerization for a highly resolutive separation of peptides

Poly(N-isopropylacrylamide-co-N-tert-butylacrylamide) [P(IPAAm-co-tBAAm)] brushes were prepared on poly(hydroxy methacrylate) (PHMA) [hydrolyzed poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)] beads having large pores by surface-initiated atom transfer radical polymerization (ATRP) and applied to the stationary phases of thermo-responsive chromatography. Optimized amount of copolymer brushes grafted PHMA beads were able to separate peptides and proteins with narrow peaks and a high resolution. The beads were found to have a specific surface area of 43.0 m²/g by nitrogen gas adsorption method. Copolymer brush of P(IPAAm-co-tBAAm) grafted PHMA beads improved the stationary phase of thermo-responsive chromatography for the all-aqueous separation of peptides and proteins.     

全亲水无规共聚物P(NIPAM-co-AA)的pH和温度双重刺激响应性水相自组装

从N-异丙基丙烯酰胺（NIPAM）和丙烯酸（AA）单体合成了一种全亲水无规共聚物P（NIPAM-co-AA）,实验发现该聚合物在水相中可以产生pH或温度双重刺激响应性自组装. 采用透射电子显微镜（TEM）观察了自组装体的形貌,采用动态光散射（DLS）和静态光散射（SLS）观察了其粒径及粒径分布. 测定了该聚合物水溶液的最低临界溶解温度（LCST）及其zeta 电位随pH的变化,通过分析NIPAM和AA两种链节的质子化状态随温度和pH变化的趋势,阐释了其在水相中产生双重响应性自组装的推动力;并结合傅里叶红外（FT-IR）光谱测定自组装体表面富集基团的结果,进一步阐释了不同环境下自组装体的微结构. 这类全亲水无规共聚物的合成方法简单,具有pH和温度双重响应性,其全水相中的刺激响应性自组装行为在药物释放等方面具有潜在的应用价值.     

全亲水无规共聚物P(NIPAM-co-AA)的pH和温度双重刺激响应性水相自组装

从N-异丙基丙烯酰胺(NIPAM)和丙烯酸(AA)单体合成了一种全亲水无规共聚物P(NIPAM-co-AA),实验发现该聚合物在水相中可以产生pH或温度双重刺激响应性自组装.采用透射电子显微镜(TEM)观察了自组装体的形貌,采用动态光散射(DLS)和静态光散射(SLS)观察了其粒径及粒径分布.测定了该聚合物水溶液的最低临界溶解温度(LCST)及其zeta电位随pH的变化,通过分析NIPAM和AA两种链节的质子化状态随温度和pH变化的趋势,阐释了其在水相中产生双重响应性自组装的推动力;并结合傅里叶红外(FT-IR)光谱测定自组装体表面富集基团的结果,进一步阐释了不同环境下自组装体的微结构.这类全亲水无规共聚物的合成方法简单,具有pH和温度双重响应性,其全水相中的刺激响应性自组装行为在药物释放等方面具有潜在的应用价值.     

pH和温度敏感型聚合物荧光探针的合成及应用

以萘酰亚胺(NI)、N-异丙基丙烯酰胺(NIPAM)和多面体齐聚倍半硅氧烷(POSS)为原料,通过可逆加成断裂自由基聚合(RAFT)方法,设计合成了具有p H响应和温度敏感的聚合物荧光探针Poly(POSS-NINIPAM)。通过核磁共振波谱仪(NMR)、荧光发射光谱仪和质谱仪(MS)等技术手段表征了Poly(POSS-NINIPAM)的p H和温度的响应性能。结果表明,在p H值5.8~8.0范围内,探针Poly(POSS-NI-NIPAM)的荧光强度变化明显,与p H值呈现良好的线性相关(λem=520 nm,p Ka=6.51),对p H和温度的响应均呈现出良好的循环检测性能,可用于检测活细胞He La的p H值变化。探针Poly(POSS-NI-NIPAM)在检测生物样本中p H/温度变化方面具有潜在的应用前景。     

Effect of core-shell micelle formation on the redox properties of phenothiazine-labeled poly(ethyl glycidy ether)-block-poly(ethylene oxide)

Redox properties of phenothiazine-labeled poly(ethyl glycidy ether)-block-poly(ethylene oxide) (PT-EGE_n-b-EO_m) are reversibly changed by core-shell micelle formation. In the temperature range higher than the critical micellization temperature (cmt), the anodic potential of PT group positively shifts and concomitantly its anodic current decrease, or levels off compared to those of the reference polymer PT-EO_m without the thermo-responsive EGE_n segment. The former alteration is caused by incorporation of hydrophobic PT groups into a core of the micelle and the latter by the decrease in the diffusion coefficient of PT groups due to formation of the core-shell micelles. The cmt value and the temperature-dependent alteration in the redox properties strongly depend on the polymer structure, especially the length of thermo-responsive EGE_n segment. The electrochemically determined hydrodynamic radii of the polymer aggregates seem to be overestimated, compared to the values reported for the aggregates of other thermo-responsive polymers with similar molecular weights, implying the presence of electrochemically inactive PT groups in the copolymers having longer thermo-responsive segments.     

Thermo-responsive polymers for thermal regulation in electrochemical energy devices

Thermo-responsive polymers have been widely explored because of their diverse structures and functions in response to temperature stimuli. Great attention has been attracted to exploring and designing such polymers composites, which offer tremendous opportunities to build up a systematic understanding of their structure–function relationships and pave the ways for their extensive applications in electronics, soft robotics, and electrochemical energy storage devices. Here, we review the most recent research of thermal regulation in electrochemical energy storage devices (e.g., batteries, supercapacitors) via thermo-responsive polymers. We summarize how battery components (i.e., electrolytes, separators, electrodes, or current collectors) can be coupled with thermo-responsive polymers based on different operation mechanisms, such as volume expansion, polymerization, phase reversion, and de-doping effects, to effectively prevent catastrophic thermal runaway. Different types of thermo-responsive polymers are evaluated to compare their key features and/or limitations. This review is concluded with perspectives of future design strategies towards more effective thermo-responsive polymers for battery thermal regulation.     

Aggregation behavior of pH- and thermo-responsive block copolymer protected gold nanoparticles

Two distinctive block copolymers protected gold nanoparticles (AuNPs) were prepared with poly(methylacrylic acid)-block-poly(N-isopropylacrylamide) (SH-PMAA₆₄-b-PNIPAM₃₅) and poly (N-isopropylacrylamide)-block-poly(methylacrylic acid) (SH-PNIPAM₄₀-b- PMAA₆₀) through strong gold-sulfur bonding. The hybrid NPs have a pH-responsive inner shell (or corona) and a thermo-responsive corona (or inner shell) due to different location relations of the PNIPAM and PMAA on the surface of AuNPs. Then, the aggregation behaviors, as well as the changes of optical properties, of two hybrid NPs were compared in response to both stimuli. The results showed the obvious inter-particle aggregation caused by the phase transition for hydrophobic coronal polymer. However, the particles of hydrophilic corona layer retained good dispersion and the pH-responsive or thermo-responsive characteristics of shell layer made relatively minor changes.     

Controlling dispersion and migration of particulate additives with block copolymers and Diels-Alder chemistry

Reversible Diels-Alder chemistry was exploited to develop thermo-responsive polymer films. Here, low molecular weight poly(styrene) (PS) and poly(ethylene glycol) (PEG) were prepared with furyl and maleimido chain ends, respectively. These polymers were then tethered together to form a thiol-terminated PEG-b-PS diblock copolymer ligand via a Diels-Alder linkage and were employed to randomly disperse 10 nm diameter Au nanoparticles within a matrix of PEG. Thermal treatment caused the Diels-Alder linkages between the polymer blocks to be severed, resulting in controllable surface functionalization due to phase separation. Migration of the Au nanoparticles to the surface of the films was characterized by Rutherford backscattering spectroscopy, small-angle X-ray scattering, contact angle measurements, and atomic force microscopy.