Study On The Preparation And Biocompatibility Of Mussel-inspired Surface Modified Carbon Nanotube With Gelatin

Objective:The agglomeration,high hydrophobicity and cytotoxic effect at high concentration are the key factors affecting the application of carbon nanotube（CNT）in biomedicine.Surface modification of carbon nanotube with hydrophilic and biocompatible molecules is an effective method to achieve good dispersion of carbon nanotubes and reduce their toxicity.Herein,The characterization and in vitro cytotoxicity of the modified carbon nanotube were carried out to provide experimental data for improving the application of carbon nanotube in oral biomedicine.Methods:The dopamine self-polymerized in basic buffer solution,when CNT met poly（dopamine）（PDA）and formed PDA coated CNT hybrid（CNT@PDA）.The PDA layers contained reactive groups and reacted with gelatin molecules via Michael addition reaction and gelatin-modified CNT（CNT@PDA@Gel）was formed.The elements of different samples were measured with X-ray photoelectron spectrometer（XPS）.The weight loss of various samples were analyzed on a thermo-gravimetric analyzer（TGA）by heating the sample from 30°C to 600°C at10°C/min under N₂atmosphere.The morphology of CNT,CNT@PDA and CNT@PDA@Gel were observed on a field emission scanning electron microscope（SEM）.The biocompatibility of different samples was assessed via acridine orange/ethidium bromide（AO/EB）staining and MTT method.Results:When PDA coated on the surface of CNT,except for the C1s and O1s,a new peak of N1s appeared at 400.00 e V,and the N atom percentage was 2.08%,demonstrating that PDA was successfully connected on the surface of CNT.The gelatin molecules contains a lot of C,N and O atoms,and thus when gelatin was anchored on the surface of CNT@PDA@Gel,the XPS spectra of CNT@PDA@Gel would show signals of C1s,N1s and O1s.Compared with XPS spectra of CNT@PDA,the results of CNT@PDA@Gel showed much more N element content（7.86%）.All the curves clearly verified the changes of surface content and demonstrated that the surface of CNT was successful coated by PDA,and then gelatin was well grafted on the surface of CNT.The weight loss of CNT,CNT@PDA and CNT@Gel was measured via TGA,it could be seen that no weight loss happens below 500°C,demonstrating that CNT possessing good thermal stability.When it was heated at 550°C,the weight loss of CNT@PDA was about 12%more than that of CNT,and this value was mainly due to the decomposition of PDA layers.When gelatin was grafted on the surface of CNT@PDA,the organic content increased and thus the weight loss of CNT@PDA@Gel was much higher than that of CNT@PDA.The difference between CNT@PDA@Gel and CNT@PDA was about 13%,mainly deriving from the decomposition of gelatin.The CNT nanotubes entangled together,and it was difficult to disperse them.When PDA coated on the surface of CNT,the nanotubes could dispersed well,while the aggregation of CNT was greatly hindered.When gelatin was grafted to the surface of CNT,the CNT@PDA@Gel could be hydrophilic and dispersed well.The result directly verified that the surface modification of CNT with gelatin could greatly tune its surface properties,improving its dispersion state and showing great potential to enhance its application as nanofillers.The biocompatibility of different samples was assessed via acridineorange/ethidium bromide（AO/EB）staining and MTT method.The tests showed the quantitative results of cell biocompatibility.The CNT showed a good biocompati-bility with 91.5%cell activity of L929 cells at 5μg/m L concentration,when the concentration increased to 10μg/m L,the cell viability was about 90.6%,when the sample concentration increased to 20 and 40μg/m L,the CNT showed evident cytotoxicity,and the cell viability dropped a lot.On the contrary,the samples of CNT@PDA and CNT@PDA@Gel showed higher cell viability than CNT,demonstrating that the surface modification method could increase the biocompatibility of CNT.Conclusion:In this study,gelatin modified CNT（CNT@PDA@Gel）was prepared via the chemical reaction between gelatin and the poly（dopamine）coated CNT.The CNT@PDA@Gel could disperse well in water,demonstrating that it was effective to realize the dispersion of CNT via gelatin modification.Furthermore,the gelatin modified CNT showed much better biocompatibility than CNT,which may improve its biomedical applications.The surface modification method in this work is very simple and can be easily carried out,which may be expanded to graft other molecules on the surface of CNT,and thus it is much helpful to broad the application of CNT.