Chitin dipentanoate as the new technologically usable biomaterial

An overview on acylation methods of α-chitin

This article overviews the acylation methods of α-chitin developed over the last four decades. The acylation of polysaccharides has been identified as a useful approach for conferring properties such as thermoplasticity. Owing to the poor solubility of α-chitin, its acylation using acid anhydrides and acyl chlorides has been traditionally investigated under heterogeneous conditions in strong acidic media. Although chitin chains depolymerize under acidic conditions, the resultant derivatives exhibit certain properties and functions. Solvents, such as LiCl/N,N-dimethyladcetamide, ionic liquids, and deep eutectic solvents, are suitable for α-chitin dissolution; therefore, acylation methods for α-chitin under homogeneous conditions have been developed using these solvents as reaction media. The functional materialization of the resultant derivatives was achieved by introducing appropriate substituents and controlling their ratios.

Synthesis of Mixed Chitin Esters via Acylation of Chitin in Deep Eutectic Solvents

The development of efficient derivatization methods of chitin, such as acylation, has been identified to confer new properties and functions to chitin. In this study, we investigate the synthesis of mixed chitin esters via the acylation of chitin in deep eutectic solvents (DESs) comprising 1-allyl-3-methylimidazolum chloride and 1,1,3,3-tetramethylguanidine based on a previous study that reported the development of efficient acylation of chitin in the DES to obtain single chitin esters. A stearoyl group was selected as the first substituent, which was combined with several bulky acyl and long oleoyl groups as the second substituents. After dissolution of chitin in the DES (2 wt%), the acylation reactions were conducted using stearoyl and the desired acyl chlorides for 1 h + 24 h at 100 °C in the resulting solutions. The IR and 1H NMR spectra of the isolated products confirmed the structures of mixed chitin esters with two different substituents. The substituent ratios in the derivatives, which were estimated via the 1H NMR analysis, were changed according to the feed ratios of two acyl chlorides.

Synthesis of mixed chitin esters with long fatty and bulky acyl substituents in ionic liquid

This study revealed that mixed chitin esters with long fatty and bulky acyl substituents were efficiently synthesized by acylation using acyl chlorides in the presence of pyridine and N,N-dimethyl-4-aminopyridine in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), at 100 °C for 24 h. A stearoyl group was selected as the first substituent, which was combined with different long fatty and bulky acyl groups as the second substituents. In addition to IR analysis of the products, which suggested progress of the acylation, ¹H NMR measurement was allowed for structural confirmation for high degrees of substitution (DSs) of the desired derivatives in CDCl₃/CF₃CO₂H solvents. Crystalline structures and thermal property of the products were evaluated by powder X-ray diffraction and differential scanning calorimetry measurements, respectively. All the products showed film formability by casting from solutions in chloroform or chloroform/trifluoroacetic acid solvents. The occurrence of halogen exchange between acyl chlorides and AMIMBr in the present system was speculated to produce highly reactive acyl bromides in situ, which efficiently reacted with hydroxy groups in chitin to obtain high DS products.

Influence of Porous Dressings Based on Butyric-Acetic Chitin Co-Polymer on Biological Processes In Vitro and In Vivo

In spite of intensively conducted research allowing for the development of more and more advanced wound dressing materials, there is still a need for dressings that stimulate not only reparative and regenerative processes, but also have a positive effect on infected and/or difficult-to-heal wounds. Porous dressing materials based on butyric-acetic chitin co-polyester containing 90% of butyryl and 10% of acetyl groups (BAC 90/10) can also be included in the group mentioned above. Two types of dressings were obtained by the salt leaching method, i.e. a porous sponge Medisorb R and Medisorb Ag with an antibacterial additive. The aim of the study was to evaluate biological effects of porous Medisorb R and Medisorb Ag dressings under in vitro and in vivo conditions. In an in vitro biodegradation test, no mass loss of Medisorb R dressing was observed within 14 days of incubation in physiological fluids at 37 °C. However, on the basis of the FTIR (Fourier Transform Infrared Spectroscopy) tests, surface degradation of Medisorb R dressing was observed. Additionally, the antibacterial activity of the porous Medisorb Ag dressing containing microsilver as an antibacterial additive was confirmed. The in vivo studies included inflammatory activity, skin irritation and sensitisation tests, as well an assessment of local effect after contact with subcutaneous tissue up to 6 months and skin wounds up to 21 days. In the in vivo tests, the dressings exhibited neither effects of skin irritation nor sensitisation. Under macroscopic examination, in full thickness defects of subcutaneous tissue and skin, the dressings caused wound healing with no inflammation, undergoing the most gradual biodegradation between weeks 4 and 8, and the observed differences were statistically significant. In the histological assessment, a weakened, limited inflammatory process associated with degradation of the material has been observed. The process of skin wound healing under Medisorb R dressing in the early period was accelerated compared to that observed in the control group with a gauze dressing.