Rapid uniaxial actuation of layered bacterial cellulose/poly(N-isopropylacrylamide) composite hydrogel with high mechanical strength

Design and fabrication of hybrid triple-responsive κ-carrageenan-based nanospheres for controlled drug delivery

In the last two decades, the utilization of magnetic nanospheres in intelligent polymeric structures have received increased attention of researchers in numerous biomedical applications. Here, hybrid nanostructured triple-responsive magnetic nanospheres (κ-Car-g-P(AA/DMA)@Fe₃O₄) containing inorganic iron oxide core (Fe₃O₄) and organic graft copolymeric shell based on κ-carrageenan (κ-Car) and poly(acrylic acid/dimethylaminoethyl methacrylate) (P(AA/DMA)) were synthesized by microwave induced co-precipitation technique. The structure, size, surface morphology, magnetic property and stability of synthesized κ-Car-g-P(AA/DMA)@Fe₃O₄ magnetic nanospheres were characterized using FTIR, UV, XRD, TEM, Zeta-sizer, and VSM. κ-Car-g-P(AA/DMA)@Fe₃O₄ nanospheres were loaded with 5-Fluorouracil (5-FU) as an antineoplastic drug, and their 5-FU release behavior was explored in diverse graft yields, pH values, temperatures and in the existence of an alternating magnetic field. The κ-Car-g-P(AA/DMA)@Fe₃O₄ nanospheres demonstrated pH-, thermo-, and magnetic field-responsive 5-FU release with good biocompatibility and excellent anticancer activity. In addition, 5-FU release under 50 mT magnetic field reached to 100% within 4 h. This work exhibits that hybrid nanospheres have a triple stimuli-responsive influence, which is of principal importance for the future design and application of multi-functional responsive platforms to develop externally stimulated release of active agents and their healthcare capability.

Anisotropic Conductive Hydrogels with High Water Content

High water content is hard to be achieved in conductive hydrogels because a mass of conductive constituent is needed to form an internal conductive pathway. Here, we developed anisotropic electrically conductive hydrogels with high water content based on bacterial cellulose (BC). Polystyrene sulfonate (PSS) was grafted to the acryloyl chloride-modified BC to provide a template for the subsequent synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT). The BC-g-PSS/PEDOT hydrogels obtained were electrically conductive owing to the immobilization of PEDOT on the surface of cellulose nanofibers. The hydrogels exhibited an electrical conductivity of 0.24 S cm^-1. Further, they demonstrated suppleness in compression (compiled to external compression stress >2.8 MPa and recoverable), inherent high water content (∼95.0 wt %), and anisotropy (anisotropic index of 4.1 in conductivity) from BC. The incorporation of a thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel into the BC-g-PSS/PEDOT hydrogel demonstrated a uniaxial thermoresponsive actuation with resistance change. The expected size and resistance change were only observed in the direction vertical to the cellulose nanofiber layers. These hydrogels could accommodate further developments in novel tissue engineering scaffolds, implantable biosensors, and smart soft electronic devices.

New strategies for the construction of eggshell powder reinforced starch based fire hazard suppression biomaterials with tailorable thermal, mechanical and oxygen barrier properties

A novel eco-friendly approach is highlighted for synthesizing chicken eggshell powder (EP) modified starch-g-poly(N-isopropylacrylamide) (starch-g-PNIPAAm) bionanocomposites (BNCs) by emulsifier-free emulsion polymerisation and aiming to study the effect of EP on the properties of modified starch BNCs. Young's modulus and tensile strength of BNCs are found to be improved dramatically. The enhanced char forming ability of EP improves the thermal stability of BNCs at high temperature as investigated by thermogravimetric analyses carried out in inert atmosphere. The cone calorimeter test revealed that the 4% w/v EP-based BNC resulted suppression on fire hazards in terms of reduction in PHRR (decreased by 33.3%), PSPR (decreased by 75.3%) compared with those of the control starch-g-PNIPAAm and could be attributed to the insulating barrier effect of EP. In addition, the fire retardancy of the BNCs is investigated from limiting oxygen index (LOI) test. The surface morphology and the elemental content of the collected char residues of BNCs after fire retardant test is analysed by FESEM and EDX. Further the oxygen barrier property of BNC with 4% w/v EP is reduced by 73% compared to starch-g-PNIPAAm. The resulting nanostructure and molecular interactions in the BNCs are analysed by FTIR, XRD and TEM.

Regenerated Antheraea pernyi Silk Fibroin/Poly(N-isopropylacrylamide) Thermosensitive Composite Hydrogel with Improved Mechanical Strength

At present, Antheraea pernyi silk fibroin (ASF) has attracted research efforts to investigate it as a raw material for fabrication of biomedical devices because of its superior cytocompatibility. Nevertheless, native ASF is not easily processed into a hydrogel without any crosslinking agent, and a single hydrogel shows poor mechanical properties. In this paper, a series of ASF/poly (N-isopropylacrylamide) (PNIPAAm) composite hydrogels with different ASF contents were manufactured by a simple in situ polymerization method without any crosslinking agent. Meanwhile, the structures, morphologies and thermal properties of composite hydrogels were investigated by XRD, FTIR, SEM, DSC and TGA, respectively. The results indicate that the secondary structure of silk in the composite hydrogel can be controlled by changing the ASF content and the thermal stability of composite hydrogels is enhanced with an increase in crystalline structure. The composite hydrogels showed similar lower critical solution temperatures (LCST) at about 32 °C, which matched well with the LCST of PNIPAAm. Finally, the obtained thermosensitive composite hydrogels exhibited enhanced mechanical properties, which can be tuned by varying the content of ASF. This strategy to prepare an ASF-based responsive composite hydrogel with enhanced mechanical properties represents a valuable route for developing the fields of ASF, and, furthermore, their attractive applications can meet the needs of different biomaterial fields.