Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

Starch-cinnamyl ethers are synthesized, shaped into thin films and characterized for their ability to undergo photo crosslinking.

Starch was plasticized with epoxidized soybean oil (ESO) modified by reaction with cinnamic acid (CA), and films were prepared using solvent casting from water/ethanol solutions. They exhibited good hydrophobicity, reduced water sensitivity, and showed the same transparency as glycerol-plasticized counterparts, but with less flexibility. Interestingly, modified ESO enhanced gelatinization and hindered retrogradation of the biopolymer. ESO was reacted with CA without the use of catalysts to obtain a β-hydroxyester; in order to optimize the synthesis process, different reaction conditions were explored, varying the stoichiometry and the heating cycles. Products were fully characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H and ¹³C nuclear magnetic resonance (NMR), and the different reactions following the opening of the oxirane ring were discussed. The properties of the novel starch-based films prepared with modified ESO highlight their use in food packaging, disposable devices, and agricultural mulching films.

High-performance liquid chromatography is a powerful tool for enantioseparation, based on chiral stationary phases as separation media. Cellulose-based chiral selectors are among the most successful ones used for the preparation of chiral separation materials, exploiting the inherent chirality of the homopolymer. Compared to initial coating-type chiral stationary phases solely deposited onto silica as the chromatographic support, covalently immobilized selectors exhibit a significantly broader scope of applicable eluents, but appropriate synthetic strategies are still scarce. In this work, we present the application of the Cu(I)-catalyzed Huisgen alkyne-azide click reaction as a means to covalently immobilize a cellulose 3,5-dichlorophenyl carbamate-type chiral selector to a silica-based chromatographic support. Cellulose was first functionalized with 3,5-dichlorophenyl carbamate groups (DS = 2.35) and 4-propargyloxy-3,5-dichlorophenyl carbamate groups (propargyl carbamate DS = 0.45, overall DS = 2.80), then clicked to 3-azidopropyl-functionalized silica gel as the chromatographic support affording a 9 wt.% covalently functionalized chiral stationary phase. The chiral selector was comprehensively characterized by means of ATR-FTIR and NMR spectroscopy, and elemental analysis. The degrees of substitution of both, overall functionalization and propargyl-anchor substitution, were estimated by NMR spectroscopy. Additionally, coating-type chiral stationary phases with 9 and 20 wt.% loadings were prepared. All chiral phases were tested with regard to their separation performance using a representative set of racemic analytes under usual normal-phase conditions. Solvent compatibility and thus the chemical robustness of the immobilized stationary phase was studied using higher shares of stronger, more polar solvents in the eluent, i.e., ethyl acetate, tetrahydrofuran and chloroform. The covalently linked selectors performed very favorably with regard to separation performance and stability. Graphical abstract