Treatment of tissue defects involves invasive processes such as implanting the tissue engineered scaffold to the defected area. Injectable scaffolds are increasingly being developed to achieve tissue regeneration in a less invasive manner. In this study, injectable chitosan cryogels in the form of microspheres were synthesized combining the water in oil emulsification method with the crosslinking of microspheres during cryogelation. The effects of polymer ratio, crosslinker concentration, cryogelation temperature, and stirring speed on the resulting cryogels’ chemistry, pore morphology, microsphere size, swelling ratio, degree of crosslinking, and degradation rate were examined for a possible noninvasive tissue engineering application. Microspheres with optimized properties were developed with an average pore and particle size of 5.50 ± 0.63 and 220.11 ± 25.58 µm at a chitosan ratio of 1%, glutaraldehyde concentration of 3%, reaction temperature of −16°C, and stirring rate of 1,000 rpm. GRAPHICAL ABSTRACT

The process of electrospinning is over a century old, yet novel material and method achievements, and later the addition of nanomaterials in polymeric solutions, have spurred a significant increase in research innovations with several unique applications. Significant improvements have been achieved in the development of electrospun nanofibrous matrices, which include tailoring compositions of polymers with active agents, surface functionalization with nanoparticles, and encapsulation of functional materials within the nanofibers. Recently, sequentially combining fabrication of nanofibers with 3D printing was reported by our group and the synergistic process offers fiber membrane functionalities having the mechanical strength offered by 3D printed scaffolds. Recent developments in electrospun nanofibers are enumerated here with special emphasis on biomedical technologies, chemical and biological sensing, and energy harvesting aspects in the context of e-textile and tactile sensing. Energy harvesting offers significant advantages in many applications, such as biomedical technologies and critical infrastructure protection by using the concept of finite state machines and edge computing. Many other uses of devices using electrospun nanofibers, either as standalone or conjoined with 3D printed materials, are envisaged. The focus of this review is to highlight selected novel applications in biomedical technologies, chem.-bio sensing, and broadly in energy harvesting for use in internet of things (IoT) devices. The article concludes with a brief projection of the future direction of electrospun nanofibers, limitations, and how synergetic combination of the two processes will open pathways for future discoveries.

Chitosan/gelatine-based materials have been widely used as biocompatible scaffolds in the tissue engineering field. Chitosan suppresses the inflammatory activities of macrophages whereas gelatine induces inflammatory cytokine production by these cells. Cryogel form of the scaffolds created an effect that was mostly dominated by chitosan activity. Since independent of chitosan to gelatine ratio, the cryogels eliminated the inflammatory cytokine production by the activated macrophages. This will enable suppression of inflammatory reactions by macrophages during implant procedure while enabling a nest of the matrix for the macrophages to reside. Determining the immunomodulatory effect of these materials during the decay is crucial to assess their biocompatibility and safety. Our results suggest that when the chitosan ratio was higher than that of gelatine the materials had anti-inflammatory activity in their powder forms based on TNFα production levels by LPS activated macrophages, whereas higher gelatine to chitosan ratio eliminated this effect. To our knowledge, this is the first study to assess the powder vs. gel forms of the chitosan/gelatine-based materials for their immunomodulatory potentials as well as how the ratio of chitosan to gelatine might affect these materials immunomodulatory effects on the activated macrophages.

Herein, we synthesized poly(vinyl alcohol) (PVA) decorated chitosan grafted poly(NIPAM-co-AAc) hydrogels through free-radical copolymerization. Increased PVA concentration revealed enhancement of temperature and pH sensitivity of the hydrogel by changing the porous structure and surface properties. Further, in vitro drug delivery studies carried out with a model dye revealed a six-fold increased release of the content at pH 7.4 with respect to pH 4.4. This new combination of three component hydrogels could be effectively used as an alternative material in the development of stimuli triggered drug delivery systems that are stable at tissues and organs with a low pH environment.