Temperature-sensitive hydrogel prepared by graft polymerization of N-isopropylacrylamide onto macroradical Pluronic

Thermosensitive PNIPAM-Based Hydrogel Crosslinked by Composite Nanoparticles as Rapid Wound-Healing Dressings

Chronic wounds are prone to produce excessive reactive oxygen species (ROS), which are the main reason for multiple bacterial infections and ulcers at the wound. Therefore, regulating ROS is the key in the process of wound healing. Herein, a new type of thermosensitive hydrogels is developed to improve the scavenging efficiency of ROS and accelerate wound repair. Nano-CeO₂ was uniformly dispersed on the surface of mesoporous silica (MSN). The nanocomposite particles were physically crosslinked with poly(N-isopropylacrylamide) (PNIPAM) to form a MSN-CeO₂@PNIPAM thermoresponsive hydrogel (PMCTH). The stability, temperature sensitivity, rheological properties, biocompatibility, and wound healing ability of the PMCTH were evaluated in detail. The results showed that the hydrogel could not only maintain the stability of the system for a long time with low biological toxicity but also have a phase transition temperature close to the human body temperature. In addition, the PMCTH was directly applied onto the skin surface. The MSN-CeO₂ nanoparticles would be dispersed in the hydrogel to restrict ROS exacerbation effects and promoted the formation of blood vessels as well as surrounding tissues, accelerating the wound healing. More importantly, animal experiments showed that when the mass ratio of CeO₂ to MSN was 40%, the wound healing rate reached up to 78% on the 10th day, which was far higher than that of other experimental groups. This study provides a new strategy and experimental basis for the applications of functional hydrogels in wound repair.

Plant-inspired Pluronic-gallol micelles with low critical micelle concentration, high colloidal stability, and protein affinity

Polymeric micelles are the most common carriers used for hydrophobic drug delivery. However, they are vulnerable to physiological barriers, such as temperature changes and enzymatic degradation, and can be easily disassembled upon dilution below the critical micelle concentration (CMC) by body fluids after an intravenous injection. Here, we report that Pluronic® micelles with octyl gallate, which is a surfactant containing gallol moieties widely found in antioxidative plant polyphenols, have a low CMC, which improves their colloidal stability without the need for covalent crosslinking. Furthermore, the incorporated gallol moieties provide enzymatic degradation resistance to the micelles owing to their protein affinity, maintaining the hydrophobic cavity of unmodified Pluronic®. Thus, plant-inspired polymeric micelles with low CMC and bioavailability are promising multifunctional vehicles for drug delivery.

Thermoreversible and Self-Protective Sol-Gel Transition Electrolytes for All-Printed Transferable Microsupercapacitors as Safer Micro-Energy Storage Devices

The safety issue caused by thermal runaway poses a huge threat toward the lifespan and application of high-density electrochemical energy storage devices, especially in the field of micro-energy, such as microsupercapacitors (MSCs). The heat accumulation is difficult to be eliminated, considering the narrow space inside integrated electronic devices attached to the MSC group. Active thermal management is of paramount importance to ensure the normal operation of electronic devices. However, existing one-time thermal protection strategies cannot fully meet current requirements. Herein, we report a promising thermoreversible temperature-responsive electrolyte system, which can shut down the current flow before thermal runaway occurs, thanks to the sol-gel transition of Pluronic [poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide)]-based graft copolymer solution. As the temperature rises to 80 °C, the self-protective electrolyte will change from the sol state to gel state. Meanwhile, the internal resistance increases and ionic conductivity decreases gradually as a result of the gelation of the sol electrolyte. The capacity of the energy storage device using the self-protective electrolyte is reduced by about 95%, and the ionic conductivity remains at only 1% at 80 °C compared with the initial value at room temperature, and it can be restored after cooling down. During 20 heating/cooling cycles, the electrochemical performance is substantially stable, demonstrating a potential approach to achieve repeatability and self-protection for micro-energy storage devices according to temperature changes. In addition, we integrated the as-prepared self-protective electrolyte into MSCs via three-dimensional printing technology to design an all-printed transferable micro-energy storage device with the dynamic reversible self-protection behavior, and the thermo-switchable protection mechanism under series and parallel conditions were studied under appropriate temperature window (25-80 °C). The strategy disclosed herein is expected to provide new insights into the new-generation smart MSCs for their wide applications in diverse fields such as microelectronics and wearable devices.

Substituting gelatine with Pluronic F-127 matrix in 3D polymer gel dosimeters can improve nuclear magnetic resonance, thermal and optical properties

This work discusses the substitution of a gelatine physical gel matrix with a matrix made of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127) in five 3D radiotherapy polymer gel dosimeters: MAGAT, PAGAT, NIPAM, VIPAR^nd (VIP) and VIPAR^CT (VIC). The current research outcomes showed that not each polymer gel dosimeter could be manufactured with Pluronic F-127. Two of the polymer gel dosimeters (PAGAT and VIP) containing the Pluronic F-127 matrix allowed for some proper dose response for radiotherapy dosimetry (a response to a dose range of e.g. 0‒50 Gy). The new best performing Pluronic-based polymer gel dosimeters were characterised by improved nuclear magnetic resonance properties, when being compared to gels with gelatine matrix at the same monomer content. These are: (i) a ~33% higher dose sensitivity; (ii) a comparable or slightly higher linear and dynamic dose range and (iii) a lower (new VIP composition, VIP3) or equivocal (new PAGAT composition, PAGAT2-Pluronic) dose threshold. However, there might be optimised gelatine based polymer dosimeters demonstrating even better sensitivity. UV-vis spectrophotometry measurements revealed that Pluronic matrices ensure six-times lower (VIP3-Pluronic) and eight-times lower (PAGAT2-Pluronic) absorbance (at 400 nm) of non-irradiated gels compared to gelatine matrices, which makes the new polymer gel dosimeters optically improved in comparison to their corresponding gelatine-based compositions. The differences in absorption reduce for higher wavelengths. Differential scanning calorimetry measurements revealed the following temperature stability ranges for the gels: (i) VIP with gelatine matrix: 0 °C‒26 °C, (ii) VIP3 with Pluronic matrix: 13.8 °C-55.2 °C, (iii) PAGAT2 with gelatine matrix: 0 °C-80 °C and (iv) PAGAT2 with Pluronic matrix: 21.4 °C-55.2 °C. In conclusion, Pluronic F-127 is an attractive co-polymer to serve as a substitute for the gelatine matrix in some 3D polymer gel dosimeters.

Thermally-Induced Triple-Shape Hydrogels: Soft Materials Enabling Complex Movements

Shape-memory hydrogels enable directed movements of a specimen in response to temperature, whereby crystallizable switching segments incorporated as side chains resulted in constant degrees of swelling during the shape-memory cycle. Here we report about hydrogels exhibiting a thermally induced triple-shape effect that allows complex movements of soft materials with two almost independent shape changes. Potential applications for those soft triple-shape materials are two-step self-unfolding devices or temperature-sensitive hydrogel actuators, for example, smart valves for flow rate control in aqueous media. Series of hydrogels with two different hydrophobic crystallizable switching segments were prepared. The degrees of swelling of the triple-shape hydrogels were not affected for different shapes or temperatures, which avoided in this way interferences on the shape shifts. During the two-step programming procedure, two distinct shapes can be implemented as reflected by shape fixity ratios of generally >50%. Structural analysis of the switching domains during the triple-shape cycle by means of X-ray scattering indicates that longer side chains gain lower orientation after deformation and that shorter side chains orient perpendicular to the hydrophilic main chain. Furthermore, it is observed that increased orientation of the switching domains is not a key requirement for adequate shape fixity and recovery ratios of the triple-shape effect in hydrogels, thus longer side chains can be utilized as switching segments in other shape-memory hydrogels.

A glucosyl triblock copolymer: synthesis and its injectable thermo- and pH-responsive behaviours

A new glucosyl triblock PGNA copolymer was first synthesized and the aqueous PGNA copolymer solution exhibits good sol–gel phase transition behaviours. The formed hydrogels are sensitive to the temperature and pH.

Tunable and selective detection of cancer cells using a betainized zwitterionic polymer with BODIPY and graphene oxide

Novel fluorescence probes, reduced graphene oxide (rGO) containing zwitterionic fluorescent nanoparticles, for effective diagnosis of cancer cells.

Successful stabilization of functionalized hybrid graphene for high-performance antimicrobial activity

We have prepared an antimicrobial nanocomposite composed of reduced graphene oxide (rGO) using antimicrobial agents and catechol derivative conjugated to polyethylene glycol-grafted poly(dimethylaminoethyl methacrylate) (PEG-g-PDMA). Graphene oxide (GO) has been simultaneously reduced by 2-chloro-3',4'-dihydroxyacetophenone (CCDP) in Tris buffer at pH 8.5 following catechol chemistry. Both CCDP and antimicrobial agent 1-bromododecane (C12) were quaternized to PEG-g-PDMA (CCDP-C12)-q-(PEG-g-PDMA). This synthesized polymer functionalized rGO as an antimicrobial nanocomposite, rGO/(CCDP-C12)-q-(PEG-g-PDMA). To increase antimicrobial activity, silver nanoparticles (Ag NPs) were deposited onto the high surface area of rGO/(CCDP-C12)-q-(PEG-g-PDMA). The prepared antimicrobial nanocomposite shows significant stability in aqueous media due to the hydrophilic behaviour of PEG. X-ray photoelectron spectroscopy investigation clearly shows the quaternization of C-12 and deposition of Ag NPs onto rGO surfaces. Ag NP-deposited rGO/(CCDP-C12)-q-(PEG-g-PDMA) shows better antimicrobial activity both against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria at lower concentration compared to without applying Ag NPs. Investigation of the cytotoxicity demonstrates outstanding non-toxic properties of both the prepared nanocomposite as well as the synthesized polymer.