Study On Dopa-Containing Tissue Adhesives Inspired By Mussel Foot Proteins

Compare to the traditional mechanical fasteners,tissue adhesive is an attractive method for surgical repair.It is due to the excellent characteristics of tissue adhesive,e.g.alleviation of bleeding and damage for the surrounding tissue,reduction of surgery time.Moreover,tissue adhesive need not to be removed and can be used as the delivery to control drug release locally.However,due to low cohesive strength and risk of disease transmission the existing tissue adhesive cannot meet the clinical demand.Hence,it is necessary to develop a biocompatibility,low cost and safe tissue adhesive to meet the clinical demand for adherence of tissue to tissue or tissue to non-tissue surfaces.Mussel foot proteins are the most remarkable and powerful adhesives in nature.3,4-dihydroxyphenylalanine?DOPA?in Mfps is believed to be responsible for this adhesion in water.Inspired by the Mfps,the aim of this study is to incorporate DOPA into side chain of polymer to duplicate this adhesive characteristic of mussel and investigate the effect of contents of DOPA or dopamine methacrylamide?DMA?on the adhesion of mussel inspired adhesives in air and water.On this basis the main influence on the adhesion of mussel inspired adhesive was investigated.The biocompatibility of mussel inspired adhesive was investigated by in vitro cytotoxicity-test at the same time.In our research,a modified DOPA?DMA?was prepared firstly.The adhesive polymer poly-(dopamine methacrylamide-co-methoxyethyl acrylate?P?DMA-co-MEA??was synthesized to carry out the adhesion in wet environment by copolymerization of DMA and methoxyethyl acrylate?MEA?.The chemical structures of adhesive polymer were confirmed by Proton Nuclear Magnetic Resonance?¹H NMR?and Ultraviolet spectrometry?UV-vis?.The results indicated that the DOPA group was incorporated into the polymer and was not destroyed during synthesis.The adhesion of the P?DMA-co-MEA?in air and water was measured by lap shear tensile adhesive tests,the shear strength???of P?DMA-co-MEA?in air was 5.28 kPa and?in water was 13.01 kPa.Secondly,a series of adhesives,P?DMA-co-MEA?,were synthesized by copolymerized DMA and MEA with the content of the DMA from 2 to 10 mol.%.The molecular weight of the synthetic polymers were investigated by Gel Permeation Chromatography?GPC?and the chemical structures of them were confirmed by ¹H NMR.Adhesion strength of these polymers on a smooth glass surface was measured by lap shear tensile adhesive tests.The results of ¹H NMR showed that contents of DMA in all adhesives were near to the theory ratios of DMA in the starting reagents.Adhesives with more than 5 mol.%of DMA appeared adhesion,while adhesives with 2 mol.%and 3 mol.%of DMA showed almost no adhesion in air and water.Adhesive with 7 mol.%of DMA had the highest molecular weight and adhesion either in air or in water in all adhesives,??in air?=20.95±1.78 kPa and??in water?=19.60±1.82 kPa.The adhesion of the adhesive which containing 7 mol.%DMA was higher than the fibrin glue?FG?.Results of lap shear tensile adhesive tests indicated that adhesion of adhesive was synergistically influenced by the content of DMA,molecular weight and elastic modulus of adhesive.It was because that higher content of DMA would provide more DOPA,which led to the coordination bond between DOPA and metal ions.It was feasible to develop the mussel inspired adhesive through incorporating DMA into polymers,which would have potential application in the clinic.Thirdly,the relationship between oxidation of DOPA and adhesion in water was investigated.The chemical structures of adhesive and oxidized adhesive were confirmed by¹H NMR and UV-vis analysis.The results indicated that the adhesive cannot be oxidized in air but can be oxidized by NaIO4.Adhesion strength of adhesive and oxidized adhesive on smooth glass surfaces were measured by lap shear tensile adhesive tests.The adhesion surfaces of them were observed by the optical microscope?OM?and scanning electron microscope?SEM?.The result of the experiment showed that DOPA in adhesive could be oxidized by NaIO₄ solution but the shear strength of the adhesive was reduced by the oxidization of adhesive.This result demonstrated that oxidation of adhesive occurred in inappropriate time would reduce the adhesion of it.It is necessary to make the mussel inspired adhesive cross-link timely and appropriately.The results of OM and SEM showed that the failure mode of adhesive was rupture when the adhesive was cured in air and the failure mode of adhesive was stripping when the adhesive was cured in PBS or NaIO₄solution.Lastly,the biological properties of the tissue adhesive,its role and mechanism during the tissue repairing were evaluated by in vitro cells experiment.L929 cells were cultured with the extracts of P?DMA-co-MEA?,purified p?DMA-co-MEA?and DMA.Methyl thiazolyl tetrazolinm tests were performed to evaluate the cell proliferation,and the relative growth rate was calculated to evaluate the cytotoxicity of P?DMA-co-MEA?,purified P?DMA-co-MEA?and DMA.The result of the vitro cells experiment indicated that the p?DMA-co-MEA?and purified P?DMA-co-MEA?are with non-cell toxic and they are full compliance to GB/T16886 standards.For this reason the P?DMA-co-MEA?has good biological properties and met the basic conditions for tissue engineering materials.DMA was cytotoxic and cannot be directly used as tissue engineering materials.