An 8-week feeding experiment was conducted to investigate and confront the putative functions of chitosan (CTS) and chitooligosaccharide (COS) in the growth and homoeostasis of distal intestine in juvenile turbots fed diets containing soyabean meal (SBM). Three isolipidic and isonitrogenous diets were formulated by supplemented basal diet (based on a 400 g/kg SBM) with 7·5 g/kg CTS or with 2·0 g/kg COS. Our results indicated that both CTS and COS supplementation could significantly improve (i) the growth performance and feed efficiency ratio; (ii) antioxidant activity driven by metabolic enzymes (i.e. catalase, glutathione reductase, glutathione peroxidase and superoxide dismutase); (iii) glutathione levels; (iv) acid phosphatase and lysozyme activity and (v) IgM content. As a result, these two particular prebiotics were able to significantly attenuate the histological alterations due to local inflammation as well as to decrease the transcriptional levels of proinflammatory cytokines (i.e. IL-1β, IL-8 and TNF-α) and major pathway effectors (i.e. activator protein-1 (AP-1), NF-кB, p38 mitogen-activated protein kinase, c-Jun N-terminal kinase and extracellular regulated kinase). High-throughput sequencing data indicated that dietary CTS and COS could significantly decrease the diversity of intestinal bacteria but elevate the relative abundances of Bacillus, Lactobacillus and Pseudomonas genera. Altogether, these findings suggest that CTS and COS can improve growth of turbot, enhance intestinal immune and anti-oxidant systems and promote the balance of intestinal microbiota. The protective effects, elicited by these two prebiotics, against SBM-induced inflammation could be attributed to their roles in alleviating the overexpression of inflammatory cytokines by possibly down-regulating NF-кB, AP-1 and/or mitogen-activated protein kinases pathways.

Chitosan is one of the most versatile biopolymers available with established properties such as antimicrobial, antitumor, anti-inflammatory, mucoadhesive, and more. It has been in biomedical research for long, but still the bench-to-bedside translation is hampered because of viscosity and solubility issues. The only commercial application of chitosan has been in hemostatic dressings. Chitosan oligosaccharide (COS), on the other hand, is highly promising in a similar research area where chitosan's limitations come into the way. COS is highly soluble in water, and its viscosity is very less than that of the parent chitosan. Although COS retains properties very similar to those of chitosan, there has been minuscule volume of research on this water-soluble chitosan. COS has been successfully used as a drug delivery vehicle in various research. COS has also shown to have osteogenic ability. It has been used as a coating on experimental orthopedic implants because of its antibacterial properties. As of now, COS is not a much-explored biopolymer, although it could be an important biopolymer for its capacity in biomedical research. This article reviews various properties and reports of COS relevant for biomedical applications.

Fabrication of simulated buccal mucosa could minimize sacrificing the animals (rabbits and pigs) to extract buccal mucosa for in vitro testing of buccal formulations. Novel artificial buccal mucosa was fabricated using eggshell membrane, extracted from poultry egg, and bovine submaxillary mucin. Chitosan oligosaccharide (COS)–based blended films were fabricated using solvent casting technique. Patches of equal dimensions were cut precisely from whole film. COS-based blended patches were analyzed for their physicochemical and mechanical properties. These patches, proposed to be used for buccal drug delivery, were tested for their mucoadhesion timing using the artificial mucosal membrane. The COS–PVA–blended patch displayed better mucoadhesion than chitosan oligosaccharide–alginate–blended film with the fabricated simulated buccal mucosa. Novel buccal mucosa mimetic–surface such as the one reported in this research article could prove to be a very useful tool in minimizing the use of excised animal buccal mucosa for mucoadhesion testing of buccal drug delivery formulations. Novel COS-blended films were fabricated as a proposed mucoadhesive buccal drug delivery vehicle.