Functionalization of Chitosan Oligomers: From Aliphatic Epoxide to Cardanol-Grafted Oligomers for Oil-in-Water Emulsions

Emulsion stability of hydroxybutyl chitosan as emulsifier at low pH: Effects of the degree of substitutions of hydroxybutyl groups

Keeping the stability of emulsions at low pH is necessary for their successful applications in food and delivery systems. To achieve this goal, hydroxybutyl chitosan (HBC) with three degrees of substitution (DSs) was used as an emulsifier to investigate the effect of HBC structure on the emulsion stability. The DSs of HBC-5, HBC-10, and HBC-20 were 0.66, 1.51, and 2.19, respectively. The stability of oil-in-water emulsions against creaming/coalescence was positively correlated with the DS. As pH decreased to 2, HBC-20-stabilized emulsions were most stable without creaming or coalescence. After 30 days of storage, no changes in the droplet sizes of HBC-20-stabilized emulsions were observed, whereas the droplet sizes of HBC-5/10- stabilized emulsions significantly increased at low pH. The stability of HBC-20- stabilized emulsions at low pH was attributed to the higher surface activity and electrostatic repulsion. Our research revealed that the emulsion stability of HBC under low pH conditions can be controlled by the density of the hydroxybutyl groups in HBC. In vitro digestion further revealed the excellent stability of HBC-20-stabilized emulsions in simulated gastric fluid, which highlighted the enormous potential of HBC-20 to protect liposoluble drugs and nutrients from the extreme pH environment.

Chitosan-Based Biomaterials: Insights into Chemistry, Properties, Devices, and Their Biomedical Applications

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.

Recyclable, UV-shielding, and biodegradable chitosan-based cardanol glycidyl ether as excellent water and oil resistance as well as gas barrier coating for paper

Developing a feasible and low-cost approach to fabricate recyclable, UV-shielding, biodegradable as well as water- and oil-resistant coating for paper substance is still a challenge. Herein, novel full-biobased chitosan-derived cardanol glycidyl ether (CS-xCGE, x = 1/8, 1/4, 1/2, and 1) coatings with different contents of cardanol glycidyl ether (CGE) were developed for paper substance via the ethoxylation of cardanol and sequent addition with chitosan in a one-pot process. Benefiting from the hydrophobicity and ultraviolet resistance of CGE, the resultant CS-CGE (x = 1) coated paper exhibited not only remarkable oil resistance (kit rating value of 11/12), but also water resistance (Cobb 60 value of 5.78 g/m²), UV shielding and excellent recyclability. Compared with the uncoated paper, the mechanical properties of CS-CGE coated paper including tensile strength, folding strength, and resistance of water vapor permeability were improved 25 %, 63 %, and 73.4 %, respectively, which could be ascribed to the flexible long-alkyl chain in the structure of CS-CGE and the continuous and homogeneous CS-CGE derived film covered in paper substance. Most importantly, CS-CGE film is biodegradable when it is only buried in soil. This study affords a feasible and sustainable strategy for large-scale fabrication of full-biobased, recyclable, UV-shielding, water and oil resistant, as well as biodegradable coating for green paper-derived packaging.

CNSL, a Promising Building Blocks for Sustainable Molecular Design of Surfactants: A Critical Review

Surfactants are crystallizing a certain focus for consumer interest, and their market is still expected to grow by 4 to 5% each year. Most of the time these surfactants are of petroleum origin and are not often biodegradable. Cashew Nut Shell Liquid (CNSL) is a promising non-edible renewable resource, directly extracted from the shell of the cashew nut. The interesting structure of CNSL and its components (cardanol, anacardic acid and cardol) lead to the synthesis of biobased surfactants. Indeed, non-ionic, anionic, cationic and zwitterionic surfactants based on CNSL have been reported in the literature. Even now, CNSL is absent or barely mentioned in specialized review or chapters talking about synthetic biobased surfactants. Thus, this review focuses on CNSL as a building block for the synthesis of surfactants. In the first part, it describes and criticizes the synthesis of molecules and in the second part, it compares the efficiency and the properties (CMC, surface tension, kraft temperature, biodegradability) of the obtained products with each other and with commercial ones.

Advances in chitooligosaccharides chemical modifications

Chitooligosaccharides (COS) differ from chitosan by their molar mass: those of COS are defined to be lower than 20 kg mol^-1 . Their functionalization is widely described in the literature and leads to the introduction of new properties that broaden their application fields. Like chitosan, COS modification sites are mainly primary amine and hydroxyl groups. Among their chemical modification, one can find amidation or esterification, epoxy-amine/hydroxyl coupling, Schiff base formation, and Michael addition. When depolymerized through nitrous deamination, COS bear an aldehyde at the chain end that can open the way to other chemical reactions and lead to the synthesis of new interesting amphiphilic structures. This article details the recent developments in COS functionalization, primarily focusing on amine and hydroxyl groups and aldehyde-chain end reactions, as well as paying considerable attention to other types of modification. We also describe and compare the different functionalization protocols found in the literature while highlighting potential mistakes made in the chemical structures accompanied with suggestions. Such chemical modification can lead to new materials that are generally nontoxic, biobased, biodegradable, and usable in various applications.