Tissue engineering/regeneration is based on the hypothesis that healthy stem/progenitor cells either recruited or delivered to an injured site, can eventually regenerate lost or damaged tissue. Most of the researchers working in tissue engineering and regenerative technology attempt to create tissue replacements by culturing cells onto synthetic porous three-dimensional polymeric scaffolds, which is currently regarded as an ideal approach to enhance functional tissue regeneration by creating and maintaining channels that facilitate progenitor cell migration, proliferation and differentiation. The requirements that must be satisfied by such scaffolds include providing a space with the proper size, shape and porosity for tissue development and permitting cells from the surrounding tissue to migrate into the matrix. Recently, chitin scaffolds have been widely used in tissue engineering due to their non-toxic, biodegradable and biocompatible nature. The advantage of chitin as a tissue engineering biomaterial lies in that it can be easily processed into gel and scaffold forms for a variety of biomedical applications. Moreover, chitin has been shown to enhance some biological activities such as immunological, antibacterial, drug delivery and have been shown to promote better healing at a faster rate and exhibit greater compatibility with humans. This review provides an overview of the current status of tissue engineering/regenerative medicine research using chitin scaffolds for bone, cartilage and wound healing applications. We also outline the key challenges in this field and the most likely directions for future development and we hope that this review will be helpful to the researchers working in the field of tissue engineering and regenerative medicine.

Skin loss is one of the oldest and still not totally resolved problems in the medical field. Since spontaneous healing of the dermal defects would not occur, the regeneration of full thickness of skin requires skin substitutes. Tissue engineering constructs would provide a three dimensional matrix for the reconstruction of skin tissue and the repair of damage. The aim of the present work is to develop a chitin based scaffold, by blending it with poly(butylene succinate) (PBS), an aliphatic, biodegradable and biocompatible synthetic polymer with excellent mechanical properties. The presence of chondroitin sulfate nanoparticles (CSnp) in the scaffold would favor cell adhesion. A chitin/PBS/CSnp composite hydrogel scaffold was developed and characterized by SEM (Scanning Electron Microscope), FTIR (Fourier Transform Infrared Spectroscopy), and swelling ratio of scaffolds were analyzed. The scaffolds were evaluated for the suitability for skin tissue engineering application by cytotoxicity, cell attachment, and cell proliferation studies using human dermal fibroblasts (HDF). The cytotoxicity and cell proliferation studies using HDF confirm the suitability of the scaffold for skin regeneration. In short, these results show promising applicability of the developed chitin/PBS/CSnps ternary composite hydrogel scaffolds for skin tissue regeneration.

Herein, improving the antibacterial activity of a hydrogel system of sodium alginate (SA) and basic chitosan (CS) using sodium hydrogen carbonate by adding AgNPs was investigated. SA-coated AgNPs produced by ascorbic acid or microwave heating were evaluated for their antimicrobial activity. Unlike ascorbic acid, the microwave-assisted method produced uniform and stable SA-AgNPs with an optimal reaction time of 8 min. Transmission electron microscopy (TEM) confirmed the formation of SA-AgNPs with an average particle size of 9 ± 2 nm. Moreover, UV-vis spectroscopy confirmed the optimal conditions for SA-AgNP synthesis (0.5% SA, 50 mM AgNO₃, and pH 9 at 80 °C). Fourier transform infrared (FTIR) spectroscopy confirmed that the –COO⁻ group of SA electrostatically interacted with either the Ag⁺ or –NH₃⁺ of CS. Adding glucono-δ-lactone (GDL) to the mixture of SA-AgNPs/CS resulted in a low pH (below the pKa of CS). An SA-AgNPs/CS gel was formed successfully and retained its shape. This hydrogel exhibited 25 ± 2 mm and 21 ± 1 mm inhibition zones against E. coli and B. subtilis and showed low cytotoxicity. Additionally, the SA-AgNP/CS gel showed higher mechanical strength than SA/CS gels, possibly due to the higher crosslink density. In this work, a novel antibacterial hydrogel system was synthesized via 8 min of microwave heating.

Gelatin fibers have been prepared by dry spinning based on the sol-gel transition phenomena of aqueous gelatin solutions. This method is simple and environmentally friendly because only water is used for the spinning, thereby avoiding the use of any toxic organic solvents. A sol-state aqueous solution of gelatin at 50 °C was extruded into air through a thin nozzle at room temperature followed by high-speed stretching in air. As a result, a stretched and shiny gelatin fiber was produced. To improve the mechanical and water-resistant properties of the fibers, a crosslinking treatment by the addition of sugars, denacol, and glutaraldehyde vapor was used. Despite their smooth surfaces, the gelatin fibers exhibited a multi-porous phase on the inside, probably owing to the retention of water during the spinning process. The mean diameters of the obtained fibers with all crosslinking agents were approximately 50–60 μm. Furthermore, the mean tensile strength was increased by all crosslinking agents. In particular, the use of N-acetyl-d-glucosamine and glutaraldehyde as the crosslinkers resulted in a remarkable increase in tensile strength and water resistance. Moreover, their properties were further improved after heat treatment. These fibers also exhibited good water resistance and maintained their morphologies for more than 90 days.

Novel chitosan (CS)-coated poly(l-lactic acid) (PLA) fibers (CS–PLA) were prepared by reaction of an alkali and CS under heat treatment without a chemical binder. These treatments induced hydrolysis on the PLA surface, formation of ionic bonds between the carboxyl groups of the PLA surface and the amino groups of CS, and dehydration between the carboxyls and amines. The prepared fibers were characterized by scanning electron microscopy and mechanical strength tests. The presence of CS on the fiber surface was observed by the visual test of CS–PLA with amido black 10B and confirmed by the amine ratio obtained by X-ray photoelectron spectroscopy. The coating thickness of CS on the surface of the PLA fibers was approximately 28 nm, as determined from calculations based on the results of Kjeldahl nitrogen analysis and elemental analysis. The degradation properties of CS–PLA were also investigated. These properties were apparently enhanced by hydrophilicity resulting from the CS-coating treatment. Furthermore, braided ropes prepared using CS–PLA became tight with increasing number of core ropes. Results indicate that the objective tensile strength and flexibility of the braided rope could be controlled by adjusting the number of core fibers.