ALTERED ENZYMATIC ACTIVITY OF LYSOZYMES BOUND TO VARIOUSLY SULFATED CHITOSANS

The purpose of this research is to investigate the effects of the variously sulfated chitosans on lysozyme activity and structure. It was shown that the specific enzymatic activity of lysozyme remained almost similar to the native protein after being bound to 6-O-sulfated chitosan （6S-chitosan） and 3,6-O-sulfated chitosan （3,6S-chitosan）, but decreased greatly after being bound to 2-N-6-O-sulfated chitosan （2,6S-chitosan）. Meanwhile, among these sulfated chitosans, 2,6S-chitosan induced the greatest conformational change in lysozyme as indicated by the fluorescence spectra. These findings demonstrated that when sulfated chitosans of different structures bind to lysozyme, lysozyme undergoes conformational change of different magnitudes, which results in corresponding levels of lysozyme activity. Further study on the interaction of sulfated chitosans with lysozyme by surface plasmon resonance （SPR） suggested that their affinities might be determined by their molecular structures.

Preparation of Carboxymethyl Sulfochitosans with Differentially Substituted Regions

Five kinds of carboxymethyl sulfochitosans with different regions such as N-carboxymethyl-O-sulfochitosan, O-carboxymethyl-N-sulfochitosan, O-carboxymethyl chitosan sulfate, N-carboxymethyl chitosan-6-sulfate, and N,O-carboxymethyl -N,O-sulfochitosan were prepared respectively by using differential carboxymethylation and sulfation methods, and their IR spectrum and 13C-NMR spectrum were measured.

Effects of Sulfate Chitosan Derivatives on Nonalcoholic Fatty Liver Disease

Sulfate chitosan derivatives have good solubility and therapeutic effect on the cell model of NAFLD. The aim of this study was to examine the therapeutic effect of sulfate chitosan derivatives on NAFLD. The male Wistar rats were orally fed high fat emulsion and received sulfate chitosan derivatives for 5 weeks to determine the pre-treatment effect of sulfate chitosan derivatives on NAFLD. To evaluate the therapeutic effect of sulfate chitosan derivatives on NAFLD, the rats were orally fed with high concentration emulsion for 5 weeks, followed by sulfate chitosan derivatives for 3 weeks. Histological analysis and biomedical assays showed that sulfate chitosan derivatives can dramatically prevent the development of hepatic steatosis in hepatocyte cells. In animal studies, pre-treatment and treatment with sulfate chitosan derivatives significantly protected against hepatic steatohepatitis induced by high fat diet according to histological analysis. Furthermore, increased TC, ALT, MDA, and LEP in NAFLD were significantly ameliorated by pre-treatment and treatment with sulfate chitosan derivatives. Furthermore, increased TG, AST, and TNF-α in NAFLD were significantly ameliorated by treatment with sulfate chitosan derivatives. Sulfate chitosan derivatives have good pre-treatment and therapeutic effect on NAFLD.

2-N,6-O sulfated chitosan evokes periosteal stem cells for bone regeneration

Musculoskeletal injuries and bone defects represent a significant clinical challenge,necessitating innovative approaches for effective bone tissue regeneration.In this study,we investigated the potential of harnessing periosteal stem cells(PSCs)and glycosaminoglycan(GAG)-mimicking materials for in situ bone regeneration.Our findings demonstrated that the introduction of 2-N,6-O sulfated chitosan(26SCS),a GAG-like polysaccharide,enriched PSCs and promoted robust osteogenesis at the defect area.Mechanistically,26SCS amplifies the biological effect of endogenous platelet-derived growth factor-BB(PDGF-BB)through enhancing the interaction between PDGF-BB and its receptor PDGFRβabundantly expressed on PSCs,resulting in strengthened PSC proliferation and osteogenic differentiation.As a result,26SCS effectively improved bone defect repair,even in an osteoporotic mouse model with lowered PDGF-BB level and diminished regenerative potential.Our findings suggested the significant potential of GAG-like biomaterials in regulating PSC behavior,which holds great promise for addressing osteoporotic bone defect repair in future applications.

Preparation of enzymatically cross-linked sulfated chitosan hydrogel and its potential application in thick tissue engineering

For the requirement of preliminary vascularization, the scaffolds for thick tissue engineering should have not only good cell affinity, but also anticoagulant ability. In this paper, enzymatically cross-linked hydrogel scaffolds based on sulfated chitosan （SCTS） were prepared. Firstly, sulfated chitosan-hydroxyphenylpionic acid （SCTS-HPA） conjugate was synthesized, and the structure of SCTS-HPA was identified by FITR and ~H NMR. And then the enzymatically cross-linked hydrogels were pre- pared in presence of horseradish peroxidase （HRP） and hydrogen peroxide （H202）. The gelation time, mechanical property, morphology and cytotoxicity to human umbilical vein endothelial cells （HUVECs） of the hydrogel were evaluated in vitro, the tissue compatibility of SCTS-HPA scaffold was studied in vivo. The results showed that the gelation time, mechanical property, morphology of the dehydrated hydrogel could be controlled by the the concentration of HRP and H202. The cytotoxicity test showed that the hydrogel extracts have no cytotoxicity to HUVECs. The in vivo assay indicated that SCTS-HPA scaffold have good tissue compatibility with no thrombus formation. All these results indicated that the SCTS-HPA scaffold could be used as a thick tissue engineering scaffold.

Amphiphilic cytokine traps remodel marrow adipose tissue for hematopoietic microenvironment amelioration

Hematopoietic stem cell transplantation(HSCT)is extensively employed in the treatment of hematological malignancies but is markedly constrained by the paucity of hematopoietic stem/progenitor cells(HSPCs).Recent studies have found that marrow adipose tissue(MAT)acts on hematopoiesis through complicated mechanisms.Therefore,the osteo-organoids fabricated in vivo using biomaterials loaded with recombinant human bone morphogenetic protein 2(rhBMP-2)have been used as models of MAT for our research.To obtain sufficient amounts of therapeutic HSPCs and healthy MAT,we have developed amphiphilic chitosan(AC)-gelatin as carriers of rhBMP-2 to the regulate type conversion of adipose tissue and trap hematopoietic growth factors.Unlike medicine interventions or cell therapies,the traps based on AC not only attenuate the occupancy of adipocytes within the hematopoietic microenvironment while preserving stem cell factor concentrations,but also improve marrow metabolism by promoting MAT browning.In conclusion,this approach increases the proportion of HSPCs in osteo-organoids,and optimizes the composition and metabolic status of MAT.These findings furnish an experimental basis for regulating hematopoiesis in vivo through materials that promote the development of autologous HSPCs.Additionally,this approach presents a theoretical model of rapid adipogenesis for the study of adipose-related pathologies and potential pharmacological targets.