Robust and Reliable Fabrication of Gelatin Films Containing Micropatterned Opal Structures via Evaporative Deposition and Thermal Gelation

Advances in the application of natural/synthetic hybrid hydrogels in tissue engineering and delivery systems: A comprehensive review

Hydrogels are widely used in biomedicine because of their excellent biocompatibility, physicochemical properties, three-dimensional cross-linked polymer networks capable of absorbing and retaining a large amount of water, and various excellent properties that can be endowed to hydrogels through modification and material integration. This review focuses on the polymer compositions and applications of natural/synthetic hybrid hydrogels. Firstly, the physical and chemical crosslinking mechanisms of hybrid hydrogels with different natural/synthetic polymer combinations were discussed in depth. In addition, polymers for the preparation of natural/synthetic hybrid hydrogels and their advantages and disadvantages are widely introduced, focusing on polysaccharides, proteins, natural aromatic polymers and common synthetic polymers. Finally, this review will focus on the applications of natural/synthetic hybrid hydrogels in tissue engineering and delivery systems. Such as bone tissue engineering, nerve tissue engineering and drug delivery.

Mineralization, degradation and osteogenic property of polylactide multicomponent porous composites for bone repair: In vitro and in vivo study

Gelatin and hydroxyapatite were assembled into polylactide porous matrix to prepare multicomponent porous composites for bone repair (PLA-gH). PLA-gH possessed a superior ability of mineralization. During simulated body fluids (SBF), the spherical Ca-P depositions on surface of PLA-gH became bulk as Ca/P decreased, while they locally turned into the rod with different variation in Ca/P during SBF containing bovine serum albumin (SBF-BSA), indicating that the mineralization of PLA-gH could be regulated by BSA. Meanwhile, PLA-gH possessed good degradation behaviour, especially in SBF-BSA, the degradation of PLA porous matrix was higher than that in SBF after 14-day immersion, whose crystallinity (Xc) decreased to a slightly lower level. Gelatin and hydroxyapatite endowed PLA-gH with good osteogenic property, characterized by obvious osteogenic differentiation and bone regeneration. In terms of predicting the cytocompatibility, osteogenic differentiation and new bone mineralization of PLA-gH by in vitro methods, applying SBF-BSA may be more reliable than SBF.

Rapid Fabrication of Large-Grain Opal Films and Photonic Crystal Hydrogel Sensors by a Filter Paper-Enhanced Evaporation Chip

Developing a rapid fabrication method for crack-free opal films is a significant challenge with broad applications. We developed a microfluidic platform known as the "filter paper-enhanced evaporation microfluidic chip" (FPEE-chip) for the fabrication of photonic crystal and inverse opal hydrogel (IOPH) films. The chip featured a thin channel formed by bonding double-sided adhesive poly(ethylene terephthalate) with a polymethyl methacrylate cover and a glass substrate. This channel was then filled with nanosphere colloids. The water was guided to evaporate rapidly at the surface of the filter paper, allowing the nanospheres to self-assemble and accumulate within the channel under capillary forces. Experimental results confirmed that the self-assembly method based on the FPEE-chip was a rapid platform for producing high-quality opal, with centimeter-sized opal films achievable in less than an hour. Furthermore, the filter paper altered the stress release mechanism of the opal films during drying, resulting in fewer cracks. This platform was proven capable of producing large-grain, crack-free opal films of up to 30 mm2 in size. We also fabricated crack-free IOPH pH sensors that exhibited color and size responsiveness to pH changes. The coefficient of variation of the gray color distribution for crack-free IOPH ranged from 0.03 to 0.07, which was lower than that of cracked IOPH (ranging from 0.07 to 0.14). Additionally, the grayscale peak value in 1 mm2 of the crack-free IOPH was more than twice that of the cracked IOPH at the same pH. The FPEE-chip demonstrated potential as a candidate for developing vision sensors.

Recent advances in biopolymer-based hydrogels and their potential biomedical applications

Hydrogels are three-dimensional networks of polymer chains containing large amounts of water in their structure. Hydrogels have received significant attention in biomedical applications owing to their attractive physicochemical properties, including flexibility, softness, biodegradability, and biocompatibility. Different natural and synthetic polymers have been intensely explored in developing hydrogels for the desired applications. Biopolymers-based hydrogels have advantages over synthetic polymers regarding improved cellular activity and weak immune response. These properties can be further improved by grafting with other polymers or adding nanomaterials, and they structurally mimic the living tissue environments, which opens their broad applicability. The hydrogels can be physically or chemically cross-linked depending on the structure. The use of different biopolymers-based hydrogels in biomedical applications has been reviewed and discussed earlier. However, no report is still available to comprehensively introduce the synthesis, advantages, disadvantages, and biomedical applications of biopolymers-based hydrogels from the material point of view. Herein, we systematically overview different synthesis methods of hydrogels and provide a holistic approach to biopolymers-based hydrogels for biomedical applications, especially in bone regeneration, wound healing, drug delivery, bioimaging, and therapy. The current challenges and prospects of biopolymers-based hydrogels are highlighted rationally, giving an insight into the progress of these hydrogels and their practical applications.