Preparation And Properties Of Quaternary Ammonium Cationic Antibacterial Gelatin Film

In the fields of food packaging,cosmetics,medical and health,natural biomacromolecule materials with good biocompatibility and biodegradability are more and more favored by researchers.Gelatin is hydrolyzed from collagen in animal's skin and bone connective tissue,and its main component is amino acid.It has certain nutritional components,and has good film forming properties.It has the advantages of forming gel under low temperature,and has good biocompatibility without toxicity.However,its application is limited by its poor mechanical properties and easy to be corroded by pathogens.In order to make up for the shortcomings of gelatin in the application process,in this paper,gelatin was modified with quaternary ammonium epoxide(QAS)as antibacterial agent,tannic acid(TA)and transglutaminase(TG)as crosslinking agents.The advantages and disadvantages of casting film and electrospinning film were compared.The specific research results mainly include the following four aspects:1,The primary amino group is the main reactive group in gelatin,so the quantitative analysis of primary amino group is of great significance.In this study,a method was designed to detect the content of primary amine in gelatin.Both the fluorescent amine and its hydrolysate have no fluorescence,but the derivative produced by its reaction with primary amine has fluorescence,and the maximum emission wavelength can be received near 503 nm at the excitation wavelength of 380 nm.Based on this principle,the content of primary amino group in gelatin was determined with three different amino acids as standard substance.The influence of different reaction conditions on the measurement results was discussed.The results showed that the optimum reaction p H was 10.0,the optimum reaction time was10.0,and the optimum reaction molar ratio of fluorescein to primary amine in amino acid was 3:1.The method was convenient and had good accuracy.It was suitable for the measurement under laboratory conditions.The content of primary amine in gelatin determined by this method has a good reference value and has a broad application prospect.2,In order to synthesize cationic antibacterial gelatin,a pure cationic antibacterial agent epoxy quaternary ammonium salt(QAS)was synthesized.Then,cationic gelatin with different cationic degree was obtained by controlling the molar ratio ofQAS epoxy group to gelatin primary amino group.The results of FTIR and XRD showed that the cationic groups were successfully grafted into gelatin.DSC test showed that the thermal properties of gelatin were not affected by QAS modification.The antibacterial test showed that the antibacterial property of gelatin was related to the cationic degree of gelatin.The antibacterial property of gelatin film was the best when the molar ratio of epoxy group to primary amine group was 2:1.3,Tannic acid(TA)is a kind of natural organic phenolic acid,which is non-toxic and has a wide range of sources.It is easy to cross-linked with the main chain or side chain of protein,so it is used as crosslinking agent.In order to improve the mechanical,thermal and hydrophobic properties of gelatin,the effect of TA concentration on the crosslinking effect of cationic antibacterial gelatin film was investigated.The FTIR results showed that the amino group of gelatin reacted with epoxy group of quaternary ammonium salt,the cationic group was grafted onto gelatin successfully,and the amino group of gelatin was crosslinked with hydroxyl group of TA.Through the derivatization reaction of fluorescent amine and primary amine group,the change of primary amino group content before and after the reaction was tested,and the cationic degree and crosslinking degree of gelatin were determined.The experimental data showed that the cationic degree of gelatin was40.89%,and the crosslinking degree increased with the increase of tannic acid content.When the ratio of tannic acid content to cationic gelatin was 8%,the cross-linking degree was increased the maximum crosslinking degree was 19.26%,and the crosslinking degree did not increase with the increase of tannic acid content,indicating that the crosslinking reached saturation.The effect of crosslinking degree on the physicochemical properties of gelatin film was studied by SEM,mechanical properties test,DSC,TGA and XRD.The results showed that the modified gelatin film formed a dense cross-linked structure,and its thermal stability and mechanical properties increased with the increase of crosslinking degree.The results of in vitro antibacterial and cytotoxicity tests showed that the antibacterial rates of cross-linked cationic membrane against E.coli and S.aureus were 95.83% and 100%,respectively.The relative growth rate(RGR)of He La cells cultured in the extract of cross-linked cationic gelatin membrane was more than 85%,indicating that the modified gelatin membrane had good antibacterial activity and biocompatibility.4.Transglutaminase(TG)is a kind of biological protease,which can catalyze the covalent crosslinking between polypeptide chains.It is nontoxic and has goodcrosslinking effect.Electrospinning technology is a relatively mature film-making process.Electrospinning fiber membrane has a large specific surface area,good air permeability,water resistance and mechanical properties,which is widely used in the field of medical and health food packaging.Cationic gelatin was crosslinked with different concentrations of transglutaminase(TG),and the films were prepared by electrospinning and casting methods.By comparing the physical and chemical properties of the two films,it was found that the spun films had a more compact fiber structure and a larger specific surface area,and the water vapor permeability(WVP),water resistance,thermal properties and antibacterial properties were better than those of casting.The results show that the electrospun film has greater application potential in food packaging,medicine and other fields.