Viscosity–temperature behavior of chitin solutions using lithium chloride/DMA as solvent

A review on chitin dissolution as preparation for electrospinning application

Electrospinning has been acknowledged as an efficient technique for the fabrication of continuous nanofibers from polymeric based materials such as polyvinyl alcohol (PVA), cellulose acetate (CA), chitin nanocrystals and others. These nanofibers exhibit chemical and mechanical stability, high porosity, functionality, high surface area and one-dimensional orientation which make it extremely beneficial in industrial application. In recent years, research on chitin - a biopolymer derived from crustacean and fungal cell wall - had gained interest due to its unique structural arrangement, excellent physical and chemical properties, in which make it biodegradable, non-toxic and biocompatible. Chitin has been widely utilized in various applications such as wound dressings, drug delivery, tissue engineering, membranes, food packaging and others. However, chitin is insoluble in most solvents due to its highly crystalline structure. An appropriate solvent system is required for dissolving chitin to maximize its application and produce a fine and smooth electrospun nanofiber. This review focuses on the preparation of chitin polymer solution through dissolution process using different types of solvent system for electrospinning process. The effect of processing parameters also discussed by highlighting some representative examples. Finally, the perspectives are presented regarding the current application of electrospun chitin nanofibers in selected fields.

Preparation of nanochitin using deep eutectic solvents

Chitin is an abundant and renewable non-wood biopolymer. Nanochitin is formed by the assembly of chitin molecules, which has the advantages of large tensile strength, high specific surface area, and biodegradability, so it has been widely used. However, the traditional methods of preparing nanochitin have many drawbacks. As the new generation of green solvents, deep eutectic solvents (DESs) have been successfully applied in the fields of chitin dissolution, extraction, and nanochitin preparation. In this review, the relevant knowledge of chitin, nanochitin, and DESs was first introduced. Then, the application status of DESs in the fields of chitin was summarized, with a focus on the preparation of nanochitin using DESs. In conclusion, this review provided a comprehensive analysis of the published literature and proposed insights and development trends in the field of preparation of nanochitin using DESs, aiming to provide guidance and assistance for future researchers.

Chitosan-based drug delivery systems for skin atopic dermatitis: recent advancements and patent trends

Atopic dermatitis (AD) is a complex, relapsing inflammatory skin disease with a considerable social and economic burden globally. AD is primarily characterized by its chronic pattern and it can have important modifications in the quality of life of the patients and caretakers. One of the fastest-growing topics in translational medicine today is the exploration of new or repurposed functional biomaterials into drug delivery therapeutic applications. This area has gained a considerable amount of research which produced many innovative drug delivery systems for inflammatory skin diseases like AD. Chitosan, a polysaccharide, has attracted attention as a functional biopolymer for diverse applications, especially in pharmaceutics and medicine, and has been considered a promising candidate for AD treatment due to its antimicrobial, antioxidative, and inflammatory response modulation properties. The current pharmacological treatment for AD involves prescribing topical corticosteroid and calcineurin inhibitors. However, the adverse reactions associated with the long-term usage of these drugs such as itching, burning, or stinging sensation are also well documented. Innovative formulation strategies, including the use of micro- and nanoparticulate systems, biopolymer hydrogel composites, nanofibers, and textile fabrication are being extensively researched with an aim to produce a safe and effective delivery system for AD treatment with minimal side effects. This review outlines the recent development of various chitosan-based drug delivery systems for the treatment of AD published in the past 10 years (2012-2022). These chitosan-based delivery systems include hydrogels, films, micro-, and nanoparticulate systems as well as chitosan textile. The global patent trends on chitosan-based formulations for the AD are also discussed.

Fabrication of chitin monoliths with controllable morphology by thermally induced phase separation of chemically modified chitin

As a natural polymer, chitin has excellent biological properties such as biodegradability and immunological, antibacterial, and wound-healing activities and has numerous applications in cosmetics, drug delivery, and pharmaceuticals. Organic polymer monoliths have also drawn significant attention, owing to their high permeability, large surface area, and high mechanical strength. They are usually applied to separation, ion exchange, catalysis, and chromatography. We have previously prepared cellulose monoliths using biopolymers; however, because chitin possesses amide groups on its side chain, it is superior to cellulose for further chemical modification and applications. However, the utilization of chitin is restricted by its insolubility in water and common organic solvents. In this study, for the first time, a monolith was prepared by chemical modification of chitin using a thermally induced phase separation (TIPS) method. First, we prepared dibutyrylchitin (DBC) as a starting polymer that is soluble in organic solvents. To prepare the monolith, DBC was dissolved completely in dimethyl sulfoxide (DMSO) while heating, and deionized water was added to the solution. It was then cooled at 20 °C to form a monolith via phase separation. The porous morphology of the DBC monolith was altered by regulating the DBC concentration, DMSO/H₂O ratio, and aging temperature. The DBC monolith was converted to a chitin monolith by the alkaline hydrolysis of butyryl ester. The successful hydrolysis of butyryl ester was confirmed by the disappearance of the peak at 1735 cm^-1 in the FT-IR spectra, which is related to the ester moiety of DBC. The chitin monolith has the potential to be utilized under water flow for catalysis, metal capture from wastewater, dye sorption, and drug delivery systems.

Chitin Hydrogels Prepared at Various Lithium Chloride/N,N-Dimethylacetamide Solutions by Water Vapor-Induced Phase Inversion

Chitin was chemically extracted from crab shells and then dissolved in N,N-dimethylacetamide (DMAc) solvent with lithium chloride (LiCl) at 3, 5, 7, and 10%. The concentrated chitin-DMAc/LiCl solutions were used for the preparation of chitin hydrogels by water vapor-induced phase inversion at 20°C. The coagulation process was investigated while altering the concentration of LiCl in the DMAc solution. The shear viscosity of the chitin solution increased with higher LiCl amounts and decreased when the concentration of LiCl was reduced by adding water to the chitin solution, implying high LiCl concentration delayed the coagulation of chitin solution in the presence of water. The viscoelasticity of the chitin solutions indicated the gel formation intensification was dependent on the dose of LiCl and chitin in the DMAc solution. After the chitin solution was coagulated, the resultant hydrogels had water contents of 387–461% and the tensile strength varied from 285 to 400 kPa when the concentration of LiCl in the hydrogel was adjusted to 3% and 7%, respectively. As for viscoelasticity, the complex modulus of the chitin hydrogels indicated that the increment of the LiCl concentration up to 7% formed the tight hydrogels. Atomic force microscopic (AFM) image revealed the formation of the entanglement network and larger domains of the aggregated chitin segments. However, the hydrogel prepared at 10% LiCl in DMAc solution exhibited weak mechanical properties due to the loose hydrogel networking caused by the strong aggregation of the chitin segments.

Protein and Polysaccharide-Based Fiber Materials Generated from Ionic Liquids: A Review

Natural biomacromolecules such as structural proteins and polysaccharides are composed of the basic building blocks of life: amino acids and carbohydrates. Understanding their molecular structure, self-assembly and interaction in solvents such as ionic liquids (ILs) is critical for unleashing a flora of new materials, revolutionizing the way we fabricate multi-structural and multi-functional systems with tunable physicochemical properties. Ionic liquids are superior to organic solvents because they do not produce unwanted by-products and are considered green substitutes because of their reusability. In addition, they will significantly improve the miscibility of biopolymers with other materials while maintaining the mechanical properties of the biopolymer in the final product. Understanding and controlling the physicochemical properties of biopolymers in ionic liquids matrices will be crucial for progress leading to the ability to fabricate robust multi-level structural 1D fiber materials. It will also help to predict the relationship between fiber conformation and protein secondary structures or carbohydrate crystallinity, thus creating potential applications for cell growth signaling, ionic conductivity, liquid diffusion and thermal conductivity, and several applications in biomedicine and environmental science. This will also enable the regeneration of biopolymer composite fiber materials with useful functionalities and customizable options critical for additive manufacturing. The specific capabilities of these fiber materials have been shown to vary based on their fabrication methods including electrospinning and post-treatments. This review serves to provide basic knowledge of these commonly utilized protein and polysaccharide biopolymers and their fiber fabrication methods from various ionic liquids, as well as the effect of post-treatments on these fiber materials and their applications in biomedical and pharmaceutical research, wound healing, environmental filters and sustainable and green chemistry research.

High strength nanostructured films based on well-preserved β-chitin nanofibrils

Chitin nanofibrils (ChNF) are interesting high-value constituents for nanomaterials due to the enormous amount of waste from the seafood industry. So far, the reported ChNFs are substantially modified and chemically degraded (shortened) during extraction from the organisms. Here, highly individualized and long native-state β-chitin nanofibrils from Illex argentinus squid pens are prepared. A mild treatment was developed to preserve the molar mass, aspect ratio, degree of acetylation and crystallite structure. The fibrils show a uniform diameter of 2-7 nm, very high aspect ratio (up to 750), high degree of acetylation (DA = 99%), and high molar mass (843 500 dalton). The powder X-ray diffraction analysis showed the preserved crystallite structure after protein removal. These "high quality" ChNFs were used to prepare nanostructured films via vacuum filtration from stable hydrocolloids. The effects of well-preserved "native" fibrils on morphology, and film properties (mechanical and optical), were studied and compared with earlier results based on coarser and shorter, chemically degraded chitin fibrils.

Production of chitin and bioactive materials from Black tiger shrimp (Penaeus monodon) shell waste by the treatment of bacterial protease cocktail

The main objective of this study was to obtain chitin in pure form from a new crustacean waste material for industrial applications. Black tiger shrimp shell wastes are a rich source of protein and valuable bioactive carbohydrate polymers such as chitin. After removal of carotenoid, Black tiger shrimp shell wastes (BTSHWs) were treated with chemicals and protease enzyme to extract chitin. Box–Behnken response surface methodology was applied to optimize the deproteinization process to obtain chitin. At optimal pH (8.82), temperature (50.05 °C), agitation speed (100.98 rpm), enzyme substrate ratio of 1:8 (wv⁻¹) and 72 h of incubation with Paenibacillus woosongensis TKB2 crude protease cocktail, 80 % deproteinization was found along with 77.28 % recovery of chitin. The valuable oligopeptides were determined by MALDI-TOF analysis and analysis of adequate amount of free amino acids in protein hydrolysate from BTSHW, indicating a high nutritional value used for food, feed or as a nitrogen source in growth medium for microorganisms. The chitin obtained was compared with the commercial chitin using scanning electron microscopy, Fourier transform infrared spectrometer, X-ray diffraction and ¹³C CP/MAS-NMR. Chitin obtained from crude protease treatment showed comparable physicochemical and structural properties to those of the commercial chitin. The carotenoid obtained after treatment can be used for medicinal purpose.

Chemistry and applications of polysaccharide solutions in strong electrolytes/dipolar aprotic solvents: an overview

Biopolymers and their derivatives are being actively investigated as substitutes for petroleum-based polymers. This has generated an intense interest in investigating new solvents, in particular for cellulose, chitin/chitosan, and starch. This overview focuses on recent advances in the dissolution and derivatization of these polysaccharides in solutions of strong electrolytes in dipolar aprotic solvents. A brief description of the molecular structures of these biopolymers is given, with emphases on the properties that are relevant to derivatization, namely crystallinity and accessibility. The mechanism of cellulose dissolution is then discussed, followed by a description of the strategies employed for the synthesis of cellulose derivatives (carboxylic acid esters, and ethers) under homogeneous reaction conditions. The same sequence of presentation has been followed for chitin/chitosan and starch. Future perspectives for this subject are summarized, in particular with regard to compliance with the principles of green chemistry.