Preparation And Characterization Of Catechol-conjugated Chitosan Hydrogels For Tissue Adhesives

Medical adhesive is a kind of special functional adhesives in the field of biomedicine.It not only has the adhesive ability,but also has a variety of performance to meet the requirements of biomedical.Marine mussels are known to adhere various substrates under wet conditions with catechol-enriched adhesion proteins.Mussel-inspired tissue bioadhesives were prepared by conjugating with multiple catechol groups in the natural or synthetic polymer to achieve adhesion.In this paper,chitosan(CHI)is an attractive base material for medical and pharmaceutial applications due to its biocompatibility,biodegradability,nontoxicity,and stimulation of cellular activities.Two kinds of catechol-conjugated chitosan adhesives were successfully synthesized via EDC/NHS coupling reaction and sequential schiff base reduction reaction respectively with chitosan acting as the backbone.The structure and properties were evaluated.Main researches are listed as follows:(1)Two novel water-soluble hydrogels for tissue adhesives(CHI-C and CCS)were obtained by EDC / NHS coupling reaction and Schiff base-reduction reaction,respectively.The structures of the chitosan derivatives were characterized by FTIR,~1H-NMR and UV-Vis absorption spectra.The antibacterial properties of the two kinds of adhesives were tested by antibacterial experiments.The results showed that CHI-C with higher catechol content was synthesized via EDC/NHS coupling reaction when the feeding mole ratio of chitosan,3,4-dihydroxy phenylacetic acid,and EDC/NHS was 1:3:3.CCS with higher catechol content was synthesized via sequential schiff base reduction reaction when the feeding mole ratio of chitosan and 3,4-dihydroxy benzaldehyde was 1:4.E.coli were used as experimental microbes.The antibacterial experiment showed that the antimicrobial activities of the two kinds of chitosan derivatives demonstrated excellent antimicrobial effectiveness.The inhibitory rates of CHI-C and CCS were nearly 100%.(2)The preparation and characterization of CHI-C hydrogel adhesive and CCS hydrogel adhesive were studied.NaIO4 was used as the crosslinking agent.The gelation time showed that it gave rise to rapid solidification of hydrogels along with the increase of the catechol amount or NaIO4 content.The rheological test showed that the increase of the catechol content in the two systems was beneficial to the gel formation and mechanical property.Results of lap shear strength tests showed that when the CHI-C adhesive concentration was 3.15% and the mole ratio of CHI-C to IO4-was 3: 1,the adhesive strength was 40.42 KPa.When the CCS adhesive concentration was 2.07% and the mole ratio of CCS to IO4-was 3: 1,the adhesive strength was 15.68 KPa.The adhesive strength of CHI-C and CCS were much stronger than that of commercial fibrin glue.L929 fibroblast was used for in vitro biocompatibility tests.MTT test results suggested that the leachable content of crosslinked CHI-C adhesive did not induce cytotoxicity,and that of CCS adhesive did not induce significant cytotoxicity.(3)A new crosslinking agent chondroitin sulfate multiple aldehyde(CSMA)was prepared to improve the properties of the adhesive.Meanwhile,this CHI-C adhesive hydrogels were expected to be usefully exploited for much more properties.The crosslinking conditions were explored to prepare CHI-C/CSMA injectable and self-healing hydrogel adhesives with the tests of sol content,mechanical properties,injectability and self-healing properties,lap shear strength.The results of FT-IR analysis showed that CSMA crosslinker was successfully prepared.The sol content of hydrogel was reduced to 32.26% when the volume ratio of CHI-C and CMSA was 1: 2,which was significantly lower than that of pure CHI-C(64.17%).The compressive strength of CHI-C/CMSA hydrogel adhesive increased with the increase of the content of CMSA.The compressive strength of CHI-C / CSMA-1: 0.2 hydrogel adhesive was 52.84 Kpa.The compressive strength of CHI-C / CSMA-1: 2 hydrogel adhesive was 172.96 KPa,which has good mechanical properties.The injectable and self-healing tests of CHI-C / CMSA hydrogels showed good injectability,tensile strength and good self-healing properties.When the concentration of CHI-C was 2.12%,the mole ratio of CHI-C to IO4-was 2: 2,and the volume ratio of CHI-C and CMSA was 1: 2,the adhesive strength was 6.53 KPa.The adhesive strength of CHI-C/CSMA hydrogel adhesive can reach that of commercial fibrin glue.