Thermo-responsive polymers and their application as smart biomaterials

Role of thermal and reactive oxygen species-responsive synthetic hydrogels in localized cancer treatment (bibliometric analysis and review)

Cancer is a major pharmaceutical challenge that necessitates improved care.

Temperature-Dependent Nanogel for Pesticide Smart Delivery with Improved Foliar Dispersion and Bioactivity for Efficient Control of Multiple Pests

The use of nanomaterials and nanotechnology to construct a smart pesticide delivery system with target-oriented and controlled-release functions is important to increase the effective utilization rate and minimize environmental residue pollution. A temperature-dependent delivery system can modulate the release of pesticide with temperature to improve the efficacy and precision targeting. A series of poly(N-isopropylacrylamide) (PNIPAM)-based nanogels with high deformability and tunable structure were successfully constructed for smart pesticide delivery and effective pest control. A lambda-cyhalothrin (LC)-loaded Pickering emulsion (LC@TNPE) with a stable gel-like network structure was further formed by the temperature-dependent nanogel to encapsule the pesticide. The foliar wettability, photostability, and controlled-release property of LC@TNPE were effectively enhanced compared to the commercial formulation because of the encapsulation and stabilization of nanogel. The release rate of LC positively correlated with temperature changes and thereby adapted to the trend of pest population increase at higher temperature. The LC@TNPE displayed improved control efficacy on multiple target pests including Plutella xylostella, Aphis gossypii, and Pieris rapae compared with the commercial suspension concentrate and microcapsule suspension, and it showed marked efficacy to control Pieris rapae for an extended duration even at a 40% reduced dosage. Furthermore, the safety was evaluated systematically on cells in vitro and with a nontarget organism. Studies confirmed that the system was relatively safe for HepG2 cells and aquatic organism zebrafish. This research provides an insight into creating an efficient and environmentally friendly pesticide nanoformulation for sustainable agriculture production.

Thermoresponsive Block Copolymer Core-Shell Nanoparticles with Tunable Flow Behavior in Porous Media

With the purpose of investigating new polymeric materials as potential flow modifiers for their future application in enhanced oil recovery (EOR), a series of amphiphilic poly(di(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate) [P(DEGMA-co-OEGMA)]-based core-shell nanoparticles were prepared by aqueous reversible addition-fragmentation chain transfer-mediated polymerization-induced self-assembly. The developed nano-objects were shown to be thermoresponsive, demonstrating a reversible lower-critical solution temperature (LCST)-type phase transition with increasing solution temperature. Characterization of their thermoresponsive nature by variable-temperature UV-vis and dynamic light scattering analyses revealed that these particles reversibly aggregate when heated above their LCST and that the critical transition temperature could be accurately tuned by simply altering the molar ratio of core-forming monomers. Sandpack experiments were conducted to evaluate their pore-blocking performance at low flow rates in a porous medium heated at temperatures above their LCST. This analysis revealed that particles aggregated in the sandpack column and caused pore blockage with a significant reduction in the porous medium permeability. The developed aggregates and the increased pressure generated by the blockage were found to remain stable under the injection of brine and were observed to rapidly dissipate upon reducing the temperature below the LCST of each formulation. Further investigation by double-column sandpack analysis showed that the blockage was able to reform when re-heated and tracked the thermal front. Moreover, the rate of blockage formation was observed to be slower when the LCST of the injected particles was higher. Our investigation is expected to pave the way for the design of "smart" and versatile polymer technologies for EOR applications in future studies.

Albumin-loaded thermo/pH dual-responsive nanogels based on sodium alginate and poly (N-vinyl caprolactam)

During the past decades, many researchers have tried to encapsulate medicines in biopolymer nanogels as injectable medicines. In the present study, dual-responsive bovine serum albumin (BSA)-loaded nanogels prepared from sodium alginate grafted poly (N-vinyl caprolactam) (PNVCL) have been reported. First, PNVCL-g-sodium alginate (PNVCL-g-Alg) was synthesized through free radical polymerization, and then nanogels were obtained from ionic crosslinking of sodium alginate in the presence of BSA. FTIR spectra showed that PNVCL-g-Alg nanogels were successfully prepared. Turbidimetry and rheometry analyses demonstrated the cloud point temperature near the human body. Particle size was evaluated using FE-SEM and dynamic light scattering and it was found that the size of particles in dry and swollen state are about 30 and 280 nm, respectively. The effect of temperature and pH on BSA release was evaluated. By comparing the drug release behavior, we found that the release of the protein at the temperature above the cloud point is faster than that at the temperature below the cloud point. The pH sensitivity of BSA-loaded PNVCL-g-Alg was evaluated at pH 5.5 and 7.4 and showed that the drug release was faster at acidic pH than at neutral pH.

An injectable hyperthermic nanofiber mesh with switchable drug release to stimulate chemotherapy potency

We developed a smart nanofiber mesh (SNM) with anticancer abilities as well as injectability and fast recovery from irregular to non-compressible shapes. The mesh can be injected at the tumor site to modulate and control anticancer effects by loading the chemotherapeutic drug, paclitaxel (PTX), as well as magnetic nanoparticles (MNPs). The storage modulus of the mesh decreases when applied with a certain shear strain, and the mesh can pass through a 14-gauge needle. Moreover, the fibrous morphology is maintained even after injection. In heat-generation measurements, the mesh achieved an effective temperature of mild hyperthermia (41-43°C) within 5 min of exposure to alternating magnetic field (AMF) irradiation. An electrospinning method was employed to fabricate the mesh using a copolymer of N-isopropylacrylamide (NIPAAm) and N-hydroxyethyl acrylamide (HMAAm), whose phase transition temperature was adjusted to a mildly hyperthermic temperature range. Pplyvinyl alcohol (PVA) was also incorporated to add shear-thinning property to the interactions between polymer chains derived from hydrogen bonding, The "on-off" switchable release of PTX from the mesh was detected by the drug release test. Approximately 73% of loaded PTX was released from the mesh after eight cycles, whereas only a tiny amount of PTX was released during the cooling phase. Furthermore, hyperthermia combined with chemotherapy after exposure to an AMF showed significantly reduced cancer cell survival compared to the control group. Subsequent investigations have proven that a new injectable local hyperthermia chemotherapy platform could be developed for cancer treatment using this SNM.

Advances in Asymmetric Wettable Janus Materials for Oil–Water Separation

The frequent occurrence of crude oil spills and the indiscriminate discharge of oily wastewater have caused serious environmental pollution. The existing separation methods have some defects and are not suitable for complex oil–water emulsions. Therefore, the efficient separation of complex oil–water emulsions has been of great interest to researchers. Asymmetric wettable Janus materials, which can efficiently separate complex oil–water emulsions, have attracted widespread attention. This comprehensive review systematically summarizes the research progress of asymmetric wettable Janus materials for oil–water separation in the last decade, and introduces, in detail, the preparation methods of them. Specifically, the latest research results of two-dimensional Janus materials, three-dimensional Janus materials, smart responsive Janus materials, and environmentally friendly Janus materials for oil–water separation are elaborated. Finally, ongoing challenges and outlook for the future research of asymmetric wettable Janus materials are presented.

Hysteresis in the thermally induced phase transition of cellulose ethers

Functionalized cellulosics have shown promise as naturally derived thermoresponsive gelling agents. However, the dynamics of thermally induced phase transitions of these polymers at the lower critical solution temperature (LCST) are not fully understood. Here, with experiments and theoretical considerations, we address how molecular architecture dictates the mechanisms and dynamics of phase transitions for cellulose ethers. Above the LCST, we show that hydroxypropyl substituents favor the spontaneous formation of liquid droplets, whereas methyl substituents induce fibril formation through diffusive growth. In celluloses which contain both methyl and hydroxypropyl substituents, fibrillation initiates after liquid droplet formation, suppressing the fibril growth to a sub-diffusive rate. Unlike for liquid droplets, the dissolution of fibrils back into the solvated state occurs with significant thermal hysteresis. We tune this hysteresis by altering the content of substituted hydroxypropyl moieties. This work provides a systematic study to decouple competing mechanisms during the phase transition of multi-functionalized macromolecules.

Swelling of Thermo-Responsive Gels in Aqueous Solutions of Salts: A Predictive Model

The equilibrium degree of swelling of thermo-responsive (TR) gels is strongly affected by the presence of ions in an aqueous solution. This phenomenon plays an important role in (i) the synthesis of multi-stimuli-responsive gels for soft robotics, where extraordinary strength and toughness are reached by soaking of a gel in solutions of multivalent ions, and (ii) the preparation of hybrid gels with interpenetrating networks formed by covalently cross-linked synthetic chains and ionically cross-linked biopolymer chains. A model is developed for equilibrium swelling of a TR gel in aqueous solutions of salts at various temperatures T below and above the critical temperature at which collapse of the gel occurs. An advantage of the model is that it involves a a small (compared with conventional relations) number of material constants and allows the critical temperature to be determined explicitly. Its ability (i) to describe equilibrium swelling diagrams on poly(N-isopropylacrylamide) gels in aqueous solutions of mono- and multivalent salts and (ii) to predict the influence of volume fraction of salt on the critical temperature is confirmed by comparison of observations with results of numerical simulation.

Development and challenges of smart actuators based on water-responsive materials

Water-responsive (WR) materials, due to their controllable mechanical response to humidity without energy actuation, have attracted lots of attention to the development of smart actuators. WR material-based smart actuators can transform natural humidity to a required mechanical motion and have been widely used in various fields, such as soft robots, micro-generators, smart building materials, and textiles. In this paper, the development of smart actuators based on different WR materials has been reviewed systematically. First, the properties of different biological WR materials and the corresponding actuators are summarized, including plant materials, animal materials, and microorganism materials. Additionally, various synthetic WR materials and their related applications in smart actuators have also been introduced in detail, including hydrophilic polymers, graphene oxide, carbon nanotubes, and other synthetic materials. Finally, the challenges of the WR actuator are analyzed from the three perspectives of actuator design, control methods, and compatibility, and the potential solutions are also discussed. This paper may be useful for the development of not only soft actuators that are based on WR materials, but also smart materials applied to renewable energy.

Flexible customization of the self-assembling abilities of short elastin-like peptide Fn analogs by substituting N-terminal amino acids

Elastin-like peptides (ELPs) are thermoresponsive biopolymers inspired by the characteristic repetitive sequences of natural elastin. As ELPs exhibit temperature-dependent reversible self-assembly, they are expected to be biocompatible thermoresponsive materials for drug delivery carriers. One of the most widely studied ELPs in this field is the repetitive pentapeptide, (VPGXG)_n . We previously reported that phenylalanine-containing ELP (Fn) analogs, in which the former Val residue of the repetitive sequence (VPGVG)_n is replaced by Phe, show coacervation with a short chain length (n = 5). Owing to their short sequences, Fn analogs are easily modified in amino acid sequences via simple chemical synthesis, and are useful for investigating the relationship between peptide sequences and temperature responsiveness. In this study, we developed Fn analogs by replacing Phe residue(s) with other amino acids or introducing another amino acid at the N-terminus. The temperature responsiveness of the Fn analogs changed drastically with the substitution of a single Phe residue, suggesting that aromatic amino acids play an important role in their self-assembly. In addition, the self-assembling ability of Fn was enhanced by increasing the bulkiness of the N-terminal amino acids. Therefore, the N-terminal residue was considered to be important for hydrophobicity-induced intermolecular interactions between the peptides during coacervation.

Methylcellulose-Chitosan Smart Gels for Hairstyling

Methylcellulose and chitosan served as promising ingredients for a thermoresponsive hair styling gel after successful application in the medical industry. Both ingredients uphold the clean beauty standard without infringing on performance. By combining these two ingredients, a hair gel can be created that promises an extended hold of style once a heated external stimulus, such as a curling wand, is applied to the hair. Chitosan serves as the cationic biopolymer to adhere the gel to the hair, whereas the methylcellulose acts as the smart biopolymer to lock the desired hairstyle in place. Various ranges of chitosan and methylcellulose concentrations were explored for formulation optimization with rheology and curl drop testing. The rheology testing included a flow sweep test to understand the shear-thinning behavior of the sample as well as the effect of concentration on viscosity. Another rheology test completed was a temperature ramp test from room temperature (25 °C) to 60 °C to study the effect of heat on the various concentrations within the samples. A curl drop test was performed as well, over a 48-h period in which the different samples were applied to wet hair tresses, dried, curled, and hung vertically to see how the style held up over a long period of time with the influence of gravity.

Role of chemistry in bio-inspired liquid wettability

Chemistry and topography are the two distinct available tools for customizing different bio-inspired liquid wettability including superhydrophobicity, superamphiphobicity, underwater superoleophobicity, underwater superoleophilicity, and liquid infused slippery property. In nature, various living species possessing super and special liquid wettability inherently comprises of distinctly patterned surface topography decorated with low/high surface energy. Inspired from the topographically diverse natural species, the variation in surface topography has been the dominant approach for constructing bio-inspired antiwetting interfaces. However, recently, the modulation of chemistry has emerged as a facile route for the controlled tailoring of a wide range of bio-inspired liquid wettability. This review article aims to summarize the various reports published over the years that has elaborated the distinctive importance of both chemistry and topography in imparting and modulating various bio-inspired wettability. Moreover, this article outlines some obvious advantages of chemical modulation approach over topographical variation. For example, the strategic use of the chemical approach has allowed the facile, simultaneous, and independent tailoring of both liquid wettability and other relevant physical properties. We have also discussed the design of different antiwetting patterned and stimuli-responsive interfaces following the strategic and precise alteration of chemistry for various prospective applications.

Control of Stimuli Sensitivity in pH-Switchable LCST/UCST-Type Thermosensitive Dendrimers by Changing the Dendrimer Structure

Stimuli-sensitive materials, such as pH- and temperature-responsive polymers, are useful as smart materials. Phenylalanine (Phe)-modified polyamidoamine (PAMAM) dendrimers with succinic acid termini, PAMAM-Phe-Suc, have been reported as unique pH-switchable lower critical solution temperature (LCST)-/upper critical solution temperature (UCST)-type thermosensitive polymers. Regulating the phase transition behavior of dendrimers is important for their applications. This study investigated the relationship between the dendrimer structure and stimuli sensitivity. Phe-modified PAMAM dendrimers with cyclohexanedicarboxylate termini (PAMAM-Phe-CHex) and sulfonate termini (PAMAM-Phe-SO₃Na) were synthesized. The temperature-dependent transmittance of these aqueous dendrimer solutions was examined at various pH values. PAMAM-Phe-CHex with Phe at all termini (PAMAM-Phe64-CHex) demonstrated a broad UCST-like phase transition at pH 7.0 but lacked an LCST-type phase transition. PAMAM-Phe-CHex with ≤ 27 Phe residues showed both LCST- and UCST-like phase transitions at different pH values, but the phase transition was broad. PAMAM-Phe-SO₃Na showed both LCST- and UCST-type phase transitions at different pH values, and the transition temperature increased as the bound Phe number decreased. Thus, the phase transition behavior of PAMAM-Phe-SO₃Na dendrimers can be regulated by varying the Phe/PAMAM ratios.

Thermosensitive Hydrogels and Advances in Their Application in Disease Therapy

Thermosensitive hydrogels, having unique sol–gel transition properties, have recently received special research attention. These hydrogels exhibit a phase transition near body temperature. This feature is the key to their applications in human medicine. In addition, hydrogels can quickly gel at the application site with simple temperature stimulation and without additional organic solvents, cross-linking agents, or external equipment, and the loaded drugs can be retained locally to improve the local drug concentration and avoid unexpected toxicity or side effects caused by systemic administration. All of these features have led to thermosensitive hydrogels being some of the most promising and practical drug delivery systems. In this paper, we review thermosensitive hydrogel materials with biomedical application potential, including natural and synthetic materials. We describe their structural characteristics and gelation mechanism and briefly summarize the mechanism of drug release from thermosensitive hydrogels. Our focus in this review was to summarize the application of thermosensitive hydrogels in disease treatment, including the postoperative recurrence of tumors, the delivery of vaccines, the prevention of postoperative adhesions, the treatment of nervous system diseases via nasal brain targeting, wound healing, and osteoarthritis treatment.

Cutting-Edge Progress in Stimuli-Responsive Bioadhesives: From Synthesis to Clinical Applications

With the advent of "intelligent" materials, the design of smart bioadhesives responding to chemical, physical, or biological stimuli has been widely developed in biomedical applications to minimize the risk of wounds reopening, chronic pain, and inflammation. Intelligent bioadhesives are free-flowing liquid solutions passing through a phase shift in the physiological environment due to stimuli such as light, temperature, pH, and electric field. They possess great merits, such as ease to access and the ability to sustained release as well as the spatial transfer of a biomolecule with reduced side effects. Tissue engineering, wound healing, drug delivery, regenerative biomedicine, cancer therapy, and other fields have benefited from smart bioadhesives. Recently, many disciplinary attempts have been performed to promote the functionality of smart bioadhesives and discover innovative compositions. However, according to our knowledge, the development of multifunctional bioadhesives for various biomedical applications has not been adequately explored. This review aims to summarize the most recent cutting-edge strategies (years 2015-2021) developed for stimuli-sensitive bioadhesives responding to external stimuli. We first focus on five primary categories of stimuli-responsive bioadhesive systems (pH, thermal, light, electric field, and biomolecules), their properties, and limitations. Following the introduction of principal criteria for smart bioadhesives, their performances are discussed, and certain smart polymeric materials employed in their creation in 2015 are studied. Finally, advantages, disadvantages, and future directions regarding smart bioadhesives for biomedical applications are surveyed.

Temperature/pH-Responsive Carboxymethyl Cellulose/Poly (N-isopropyl acrylamide) Interpenetrating Polymer Network Aerogels for Drug Delivery Systems

Temperature/pH-responsive carboxymethyl cellulose/poly (N-isopropyl acrylamide) interpenetrating polymer network (IPN) aerogels (CMC/Ca²⁺/PNIPAM aerogels) were developed as a novel drug delivery system. The aerogel has a highly open network structure with a porosity of more than 90%, which provides convenient conditions for drug release. The morphology and structure of the CMC/Ca²⁺/PNIPAM aerogels were characterized via scanning electron microscopy (SEM), Micro-CT, X-ray photoelectron spectroscopy (XPS), pore size analysis, and cytotoxicity analysis. The analysis results demonstrate that the aerogel is non-toxic and has more active sites, temperatures, and pH response performances. The anticancer drug 5-fluorouracil (5-FU) was successfully loaded into aerogels through physical entrapment and hydrogen bonding. The drug loading and sustained-release model of aerogels are used to fit the drug loading and sustained-release curve, revealing the drug loading and sustained-release mechanism, and providing a theoretical basis for the efficient drug loading and sustained release.

Characterisation of Selected Materials in Medical Applications

Tissue engineering is an interdisciplinary field of science that has developed very intensively in recent years. The first part of this review describes materials with medical and dental applications from the following groups: metals, polymers, ceramics, and composites. Both positive and negative sides of their application are presented from the point of view of medical application and mechanical properties. A variety of techniques for the manufacture of biomedical components are presented in this review. The main focus of this work is on additive manufacturing and 3D printing, as these modern techniques have been evaluated to be the best methods for the manufacture of medical and dental devices. The second part presents devices for skull bone reconstruction. The materials from which they are made and the possibilities offered by 3D printing in this field are also described. The last part concerns dental transitional implants (scaffolds) for guided bone regeneration, focusing on polylactide-hydroxyapatite nanocomposite due to its unique properties. This section summarises the current knowledge of scaffolds, focusing on the material, mechanical and biological requirements, the effects of these devices on the human body, and their great potential for applications.

Thermoresponsive Ionic Liquid/Water Mixtures: From Nanostructuring to Phase Separation

The thermodynamics, structures, and applications of thermoresponsive systems, consisting primarily of water solutions of organic salts, are reviewed. The focus is on organic salts of low melting temperatures, belonging to the ionic liquid (IL) family. The thermo-responsiveness is represented by a temperature driven transition between a homogeneous liquid state and a biphasic state, comprising an IL-rich phase and a solvent-rich phase, divided by a relatively sharp interface. Demixing occurs either with decreasing temperatures, developing from an upper critical solution temperature (UCST), or, less often, with increasing temperatures, arising from a lower critical solution temperature (LCST). In the former case, the enthalpy and entropy of mixing are both positive, and enthalpy prevails at low T. In the latter case, the enthalpy and entropy of mixing are both negative, and entropy drives the demixing with increasing T. Experiments and computer simulations highlight the contiguity of these phase separations with the nanoscale inhomogeneity (nanostructuring), displayed by several ILs and IL solutions. Current applications in extraction, separation, and catalysis are briefly reviewed. Moreover, future applications in forward osmosis desalination, low-enthalpy thermal storage, and water harvesting from the atmosphere are discussed in more detail.

Development of a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel

Gelatin-based bioadhesives are suitable for the treatment of wounds due to their inherent biocompatibility, lack of immunogenicity, and potential for modification. However, common limitations with such adhesives include their adhesive strength and versatility. In the present study, a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel (DNGel) was engineered using facile dual-syringe methodology. An integrative crosslinking strategy utilized the complexation of catechol-Fe³⁺ and NIPAAm-methacryloyl. As anticipated, the DNGel exhibited multifunctional therapeutic properties, namely temperature-sensitivity, mechanical flexibility, good adhesive strength, injectability, self-healing capability, antibacterial activity, and the capability to enable hemostasis and wound healing. The bioinspired dynamic double-network was stabilized by a number of molecular interactions between components in the DNGel, providing multifunctional therapeutic performance. In addition, comprehensive in vitro and in vivo testing confirmed that the adhesive hydrogel exhibited effective antihemorrhagic properties and accelerated wound healing by the promotion of revascularization, representing considerable potential as a next-generation multifunctional smart adhesive patch.

Freeform printing of thermoresponsive poly(2-cyclopropyl-oxazoline) as cytocompatible and on-demand dissolving template of hollow channel networks in cell-laden hydrogels

Conventional additive-manufacturing technologies rely on the vertical stacking of layers, whereas each layer provides the structural integrity for the upcoming one. This inherently gives rise to limitations in freedom of design especially when structures containing large voids or truly 3D pathways for printed filaments are aspired. An especially interesting technique, which overcomes these layer limitations, is freeform printing, where thermoplastic materials are printed in 3D through controlling the temperature profile such that the polymer melt solidifies right when it exits the nozzle. In this study, we introduce freeform printing for thermoresponsive polymers at the example of poly(2-cyclopropyl-oxazoline) (PcycloPrOx). This material is especially interesting for biofabrication, as poly(oxazoline)s are known to provide excellent cytocompatibility. Furthermore, (PcycloPrOx) scaffolds provide adequate stability, so that the printed structures can be embedded in cell-laden hydrogels and sufficient time remains for the gel to form around the scaffold before dissolution via temperature reduction. This ensures accuracy and prevents channel collapse for the creation of cell-laden hydrogels with an embedded three-dimensionally interconnected channel network without the need of any additional processing step such as coating.

Mechanisms Affecting Physical Aging and Swelling by Blending an Amphiphilic Component

Polymer blending is a promising method to overcome stability obstacles induced by physical aging and swelling of implant scaffolds prepared from amorphous polymers in biomedical application, since it will not bring potential toxicity compared with chemical modification. However, the mechanism of polymer blending still remains unclearly explained in existing studies that fail to provide theoretical references in material R&D processes for stability improvement of the scaffold during ethylene oxide (EtO) sterilization, long-term storage, and clinical application. In this study, amphiphilic poly(ethylene glycol)-co-poly(lactic acid) (PELA) was blended with amorphous poly(lactic-co-glycolic acid) (PLGA) because of its good miscibility so as to adjust the glass transition temperature (Tg) and hydrophilicity of electrospun PLGA membranes. By characterizing the morphological stability and mechanical performance, the chain movement and the glass transition behavior of the polymer during the physical aging and swelling process were studied. This study revealed the modification mechanism of polymer blending at the molecular chain level, which will contribute to stability improvement and performance adjustment of implant scaffolds in biomedical application.

Metal ion scavenging activity of elastin-like peptide analogues containing a cadmium ion binding sequence

The development of simple and safe methods for recovering environmental pollutants, such as heavy metals, is needed for sustainable environmental management. Short elastin-like peptide (ELP) analogues conjugated with metal chelating agents are considered to be useful as metal sequestering agents as they are readily produced, environment friendly, and the metal binding domain can be selected based on any target metal of interest. Due to the temperature dependent self-assembly of ELP, the peptide-based sequestering agents can be transformed from the solution state into the particles that chelate metal ions, which can then be collected as precipitates. In this study, we developed a peptide-based sequestering agent, AADAAC-(FPGVG)₄, by introducing the metal-binding sequence AADAAC on the N-terminus of a short ELP, (FPGVG)₄. In turbidity measurements, AADAAC-(FPGVG)₄ revealed strong self-assembling ability in the presence of metal ions such as Cd²⁺ and Zn²⁺. The results from colorimetric analysis indicated that AADAAC-(FPGVG)₄ could capture Cd²⁺ and Zn²⁺. Furthermore, AADAAC-(FPGVG)₄ that bound to metal ions could be readily recycled by treatment with acidic solution without compromising its metal binding affinity. The present study indicates that the fusion of the metal-binding sequence and ELP is a useful and powerful strategy to develop cost-effective heavy metal scavenging agents with low environmental impacts.

Design of biointerfaces composed of soft materials using controlled radical polymerizations

Soft interface materials have an immense potential for the improvement of biointerfaces, which are the interface of biological and artificially designed materials. Controlling the chemical and physical structures of the interfaces at the nanometer level plays an important role in understanding the mechanism of the functioning and its applications. Controlled radical polymerization (CRP) techniques, including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization, have been developed in the field of precision polymer chemistry. It allows the formation of well-defined surfaces such as densely packed polymer brushes and self-assembled nanostructures of block copolymers. More recently, a novel technique to prepare polymers containing biomolecules, called biohybrids, has also been developed, which is a consequence of the advancement of CRP so as to proceed in an aqueous media with oxygen. This review article summarizes recent advances in CRP for the design of biointerfaces.

Thermogenetics: Applications come of age

Temperature is a ubiquitous physical cue that is non-invasive, penetrative and easy to apply. In the growing field of thermogenetics, through beneficial repurposing of natural thermosensing mechanisms, synthetic biology is bringing new opportunities to design and build robust temperature-sensitive (TS) sensors which forms a thermogenetic toolbox of well characterised biological parts. Recent advancements in technological platforms available have expedited the discovery of novel or de novo thermosensors which are increasingly deployed in many practical temperature-dependent biomedical, industrial and biosafety applications. In all, the review aims to convey both the exhilarating recent technological developments underlying the advancement of thermosensors and the exciting opportunities the nascent thermogenetic field holds for biomedical and biotechnology applications.

Synthesis and Study of Thermoresponsive Amphiphilic Copolymers via RAFT Polymerization

Synthesis and study of well-defined thermoresponsive amphiphilic copolymers with various compositions were reported. Kinetics of the reversible addition-fragmentation chain transfer (RAFT) (co)polymerization of styrene (St) and oligo(ethylene glycol) methyl ether methacrylate (PEO5MEMA) was studied by size exclusion chromatography (SEC) and 1H NMR spectroscopy, which allows calculating not only (co)polymerization parameters but also gives valuable information on RAFT (co)polymerization kinetics, process control, and chain propagation. Molecular weight Mn and dispersity Đ of the copolymers were determined by SEC with triple detection. The detailed investigation of styrene and PEO5MEMA (co)polymerization showed that both monomers prefer cross-polymerization due to their low reactivity ratios (r1 < 1, r2 < 1); therefore, the distribution of monomeric units across the copolymer chain of p(St-co-PEO5MEMA) with various compositions is almost ideally statistical or azeotropic. The thermoresponsive properties of p(St-co-PEO5MEMA) copolymers in aqueous solutions as a function of different hydrophilic/hydrophobic substituent ratios were evaluated by measuring the changes in hydrodynamic parameters under applied temperature using the dynamic light scattering method (DLS).

Nanocomposite electrospun fibers of poly(ε-caprolactone)/bioactive glass with shape memory properties

Electrospun fibers of shape memory triethoxysilane-terminated poly(epsilon-caprolactone) (PCL-TES) loaded with bioactive glasses (BG) are here presented. Unloaded PCL-TES, as well as PCL/BG nanocomposite fibers, are also considered for comparison. It is proposed that hydrolysis and condensation reactions take place between triethoxysilane groups of the polymer and the silanol groups at the BG particle surface, thus generating additional crosslinking points with respect to those present in the PCL-TES system. The as-spun PCL-TES/BG fibers display excellent shape memory properties, in terms of shape fixity and shape recovery ratios, without the need of a thermal crosslinking treatment. BG particles confer in vitro bioactivity to PCL-based nanocomposite fibers and favor the precipitation of hydroxycarbonate apatite on the fiber surface. Preliminary cytocompatibility tests demonstrate that the addition of BG particles to PCL-based polymer does not inhibit ST-2 cell viability. This novel approach of using bioactive glasses not only for their biological properties, but also for the enhancement of shape memory properties of PCL-based polymers, widens the versatility and suitability of the obtained composite fibers for a huge portfolio of biomedical applications.

Molecular bases for temperature sensitivity in supramolecular assemblies and their applications as thermoresponsive soft materials

Thermoresponsive supramolecular assemblies have been extensively explored in diverse formats, from injectable hydrogels to nanoscale carriers, for a variety of applications including drug delivery, tissue engineering and thermo-controlled catalysis. Understanding the molecular bases behind thermal sensitivity of materials is fundamentally important for the rational design of assemblies with optimal combination of properties and predictable tunability for specific applications. In this review, we summarize the recent advances in this area with a specific focus on the parameters and factors that influence thermoresponsive properties of soft materials. We summarize and analyze the effects of structures and architectures of molecules, hydrophilic and lipophilic balance, concentration, components and external additives upon the thermoresponsiveness of the corresponding molecular assemblies.

Silica-Based Stimuli-Responsive Systems for Antitumor Drug Delivery and Controlled Release

The administration of cytotoxic drugs in classical chemotherapy is frequently limited by water solubility, low plasmatic stability, and a myriad of secondary effects associated with their diffusion to healthy tissue. In this sense, novel pharmaceutical forms able to deliver selectively these drugs to the malign cells, and imposing a space-time precise control of their discharge, are needed. In the last two decades, silica nanoparticles have been proposed as safe vehicles for antitumor molecules due to their stability in physiological medium, high surface area and easy functionalization, and good biocompatibility. In this review, we focus on silica-based nanomedicines provided with specific mechanisms for intracellular drug release. According to silica nature (amorphous, mesostructured, and hybrids) nanocarriers responding to a variety of stimuli endogenously (e.g., pH, redox potential, and enzyme activity) or exogenously (e.g., magnetic field, light, temperature, and ultrasound) are proposed. Furthermore, the incorporation of targeting molecules (e.g., monoclonal antibodies) that interact with specific cell membrane receptors allows a selective delivery to cancer cells to be carried out. Eventually, we present some remarks on the most important formulations in the pipeline for clinical approval, and we discuss the most difficult tasks to tackle in the near future, in order to extend the use of these nanomedicines to real patients.

Multi-responsive γ-methylene-γ-butyrolactone/N-vinyl caprolactam copolymers involving pH-dependent reversible lactonization

Copolymerization of γ-methylene-γ-butyrolactone with N-vinyl caprolactam leads to a peculiar multi-responsive NVCL-based system involving a unique reversible pH-dependent ring opening/closure of the pendant lactones.