Natural collagen has good biocompatibility and ability to promote tissue regeneration; however, its low flexibility and easy degradation hinder its applications in wound repair.

Collagen has been widely applied to biomaterials. However, it must be chemically fixed before it can be used. The aim of this work is to study on the crosslinking effect of a naturally derived oxidized chitosan oligosaccharide (OCOS) on collagen type I. The physicochemical properties and biocompatibility of the crosslinked collagen (OCOS-Col) were evaluated. The FTIR spectroscopy showed that crosslinking via OCOS had no impact on the structural integrity of collagen. DSC and TG tests showed that the thermal stability of crosslinked collagen was improved significantly, while the crosslinking density test indicated that the amino groups of collagen could predominantly react with the available aldehyde groups of OCOS. The mechanical properties, hydrophilicity, and enzymatic degradation test showed that the crosslinked material had improved properties. However, the porosity test showed that the crosslinked material was more compact, which was consistent with the AFM observation that crosslinked collagen revealed a denser network structure. Cytotoxicity test showed that the crosslinked collagen was conducive to cell adhesion, growth, and proliferation. In conclusion, this work reveals that OCOS stabilized collagen as a crosslinker, preserved its triple helical structure, and reserved its good biocompatibility. OCOS was proven to be a safe and reliable crosslinker for collagen.

Antibacterial and physicochemical properties are generally considered important features of the porcine acellular dermal matrix (pADM). Oxidized 2-hydroxypropyltrimethyl ammonium chloride chitosan (OHTCC) was applied to crosslink with pADM at dosages of 1, 2, 4, 8, and 16%. The properties of the crosslinked pADM (OHTCC-pADM) were evaluated. DSC and TG analysis suggested that crosslinking could promote the thermal stability, the highest T d , and T max of OHTCC-pADM (8%) was 80 C and 325 C, which has been improved by 15 C and 13 C, respectively. While FTIR and AFM tests indicated that the structure integrity of collagen could still be maintained. SEM tests demonstrated the sustained three-dimensional architecture of OHTCC-pADM with appropriate porosity. Moreover, OHTCC-pADM exhibited improved ability to resist collagenase degradation, the degradation rate of 4%-, 8%-OHTCC-pADM was <50%. The tensile strength of OHTCC-pADM proved to be superior compared to pADM. Furthermore, 8%-OHTCC-pADM exhibited nearly 90% antibacterial activity against Escherichia coli, and Staphylococcus aureus. In addition, the results of the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazoliumbromide study showed that the cytocompatibility of OHTCC-pADM decreased with the increasing the amount of OHTCC, but all relative proliferation rates were above 80%. In conclusion, our study revealed that OHTCC stabilized and functionalized pADM while preserving good cytocompatibility.

In order to prepare a biocompatible tissue adhesive and sealant with high adhesion properties, dopamine (DA) was grafted onto sodium carboxymethyl cellulose (CMC) to obtain catechol-modified CMC-DA by carbodiimide chemistry method, and then CMC-DA hydrogels was prepared by self-cross-linking. The UV-Vis spectroscopy, FTIR and 1 H NMR results showed that dopamine was successfully introduced into CMC and the degree of substitution of dopamine in the CMC-DA hydrogels was 5%, 10.5% and 15%, respectively. SEM observation indicated that CMC-DA possessed porous structures. Cytotoxicity experiments showed that CMC-DA has good biocompatibility. The introduction of DA could further improve the biocompatibility of hydrogel. Bulk adhesion property of the hydrogels was studied by lap shear tests. Results showed that the adhesion strength of CMC was improved indeed after modified by dopamine.