Chitosan: Structural modification, biological activity and application

Many by-products that are harmful to the environment and human health are generated during food processing. However, these wastes are often potential resources with high-added value. For example, crustacean waste contains large amounts of chitin. Chitin is one of the most abundant polysaccharides in natural macromolecules, and is a typical component of crustaceans, mollusks, insect exoskeleton and fungal cell walls. Chitosan is prepared by deacetylation of chitin and a copolymer of D-glucosamine and N-acetyl-D-glucosamine through β-(1 → 4)-glycosidic bonds. Chitosan has better solubility, biocompatibility and degradability compared with chitin. This review introduces the preparation, physicochemical properties, chemical and physical modification methods of chitosan, which could help us understand its biological activities and applications. According to the latest reports, the antibacterial activity, antioxidant, immune and antitumor activities of chitosan and its derivatives are summarized. Simultaneously, the various applications of chitosan and its derivatives are reviewed, including food, chemical, textile, medical and health, and functional materials. Finally, some insights into its future potential are provided, including novel modification methods, directional modification according to structure-activity relationship, activity and application development direction, etc.

An Integrated Redox Cycling for Electrochemical Enzymatic Signal Enhancement

Highly sensitive analytical methods for the detection of proteins are still an urgent demand in early medical diagnosis and the discovery of biomarkers with ultralow abundance. Here an integrated electrochemical-chemical-enzymatic redox cycling is designed for significant enhancement of electrochemical enzymatic signal in biorecognition. This strategy efficiently utilizes the high specificity of the outersphere to innersphere redox reaction to mediate the enzymatic redox cycling with the nonenzymatic redox cycling. The oxygenation activity of tyrosinase as a label of the biorecognition event ensures low background and generates outersphere-reaction-philic/innersphere-reaction-philic redox couples, which leads to 13 300× amplification of electrochemical signal. The mediation of nonenzymatic redox cycling in the integrated system produces a 14-fold improved ratio of signal to background. The practicality of the proposed approach with clinical samples demonstrates its potential in clinical diagnostic and therapeutic monitoring. This work opens a new avenue to design novel signal amplification strategies for ultrasensitive bioanalysis.

Tailored interfacial architecture of chitosan modified glassy carbon electrodes facilitating selective, nanomolar detection of dopamine

Chitosan was tailored directly on the electrode surface to detect DA selectively in nanomolar level at physiological pH.

A Bilayer Engineered Skin Substitute for Wound Repair in an Irradiation-Impeded Healing Model on Rat

Objective: An engineered skin substitute is produced to accelerate wound healing by increasing the mechanical strength of the skin wound via high production of collagen bundles. During the remodeling stage of wound healing, collagen deposition is the most important event. The collagen deposition process may be altered by nutritional deficiency, diabetes mellitus, microbial infection, or radiation exposure, leading to impaired healing. This study describes the fabrication of an engineered bilayer skin substitute and evaluates its effectiveness for the production of collagen bundles in an impaired healing model. Approach: Rats were exposed to 10 Gy of radiation. Two months postirradiation, the wounds were excised and treated with one of three skin replacement products: bilayer engineered skin substitutes, chitosan skin templates, or duoderm^©. The collagen deposition was analyzed by hematoxylin and eosin staining. Results: On day 21 postwound, the irradiated wounds displayed increased collagen bundle deposition after treatment using bilayer engineered skin substitutes (3.4±0.25) and chitosan skin templates (3.2±0.58) compared with duoderm (2.0±0.63). Innovation: We provide the first report on the fabrication of bilayer engineered skin substitutes using high density human dermal fibroblasts cocultured with HFSCs on chitosan skin templates. Conclusion: The high density of fibroblasts significantly increases the penetration of cells into chitosan skin templates, contributing to the fabrication of bilayer engineered skin substitute.

Microstructure, Mechanical, and Biological Properties of Porous Poly(vinylidene fluoride) Scaffolds Fabricated by Selective Laser Sintering

Porous poly(vinylidene fluoride) (PVDF) scaffolds were prepared by selective laser sintering. The effects of laser energy density, ranging from 0.66 to 2.16 J/mm2, on microstructure and mechanical properties were investigated. At low energy density levels, PVDF particles could fuse well and the structure becomes dense with the increase of the energy density. Smoke and defects (such as holes) were observed when the energy density increased above 1.56 J/mm2which indicated decomposition of the PVDF powder. The scaffolds appeared to be light yellow and there was a reduction in tensile strength. The fabricated scaffolds were immersed into simulated body fluid for different time to evaluate biostability. In addition, MG63 cells were seeded and cultured for different days on the scaffolds. The testing results showed that the cells grew and spread well, indicating that PVDF scaffolds had good biocompatibility.

Skin Tissue Surface Morphology and Quality of RNA and Protein Extracted from Fresh and Stabilized Human Cleft Lip and Palate Tissue

Cleft lip palate is a human congenital disorder worldwide and the study of this genetic disease requires molecular genetic analysis. This analysis required the use of nucleic acid and protein, thus good quality and quantity of its extraction is important. We are comparing RNA and protein extractions from tissue biopsy of cleft lip palate in both fresh and stabilized condition. Tissue morphology was also captured using Scanning Electron Microscopy (SEM) for any morphology differences. Tissue homogenization may destroy nucleic acid stability but not its morphology. Low RNA concentration from stabilized tissue was found. However, there was no crucial issue of protein extraction, degradation or concentration. Tissue morphology was slight different between normal and CL/P tissue.

Keloid pathogenesis via Drosophila similar to mothers against decapentaplegic (SMAD) signaling in a primary epithelial-mesenchymal in vitro model treated with biomedical-grade chitosan porous skin regenerating template

The effects of locally produced chitosan (CPSRT-NC-bicarbonate) in the intervention of keloid pathogenesis were investigated in vitro. A human keratinocyte-fibroblast co-culture model was established to investigate the protein levels of human collagen type-I, III and V in a western blotting analysis, the secreted transforming growth factor-β1 (TGF-β1) in an enzyme-linked immunosorbent assay (ELISA) and the mRNA levels of TGF-β1's intracellular signaling molecules (SMAD2, 3, 4 and 7) in a real-time PCR analysis. Keratinocyte-fibroblast co-cultures were maintained in DKSFM:DMEM:F12 (2:2:1) medium. Collagen type-I was found to be the dominant form in primary normal human dermal fibroblast (pNHDF) co-cultures, whereas collagen type-III was more abundant in primary keloid-derived human dermal fibroblast (pKHDF) co-cultures. Collagen type-V was present as a minor component in the skin. TGF-β1, SMAD2 and SMAD4 were expressed more in the pKHDF than the pNHDF co-cultures. Co-cultures with normal keratinocytes suppressed collagen type-III, SMAD2, SMAD4 and TGF-β1 expressions and CPSRT-NC-bicarbonate enhanced this effect. In conclusion, the CPSRT-NC-bicarbonate in association with normal-derived keratinocytes demonstrated an ability to reduce TGF-β1, SMAD2 and SMAD4 expressions in keloid-derived fibroblast cultures, which may be useful in keloid intervention.