Preparation And Application Of Chitosan-based Derivatives Modified By Cinnamic Acid

Chitosan（CS）is a natural linear polycation compound with good biocompatibility.However,due to the existence of strong hydrogen bonds,CS has poor water solubility.In addition,CS itself has limited antibacterial and emulsifying activities,which further limits the application of CS.The molecular structure of CS contains many–NH₂ and–OH groups,which can be used as the active sites of chemical modification reactions.By introducing new functional groups,the solubility and functional activity of CS can be improved,and a variety of CS-based derivatives can be generated,which is one of the current research hotspots.Cinnamic acid（CA）is an unsaturated aromatic carboxylic acid.It has good antimildew,anticorrosion,and antibacterial effects.It is safe.However,CA is insoluble in water,which limits its application in water systems.In this paper,two new CA modified CS-based derivatives were successfully prepared,which were HPCS-CA and HTCC-CA derivatives.The characterization,properties,and applications of the derivatives were explored.The contents are as follows:1.Firstly,hydroxypropyl CS（HPCS）was prepared by hydroxypropyl modification of CS,with a degree of substitution（DS）of 112.99%.Then,HPCS was chemically reacted with CA.By changing the molar ratios of HPCS and CA,three HPCS-CA1–3 derivatives were designed and synthesized,with the DS of CA of 23.00%,74.86%,and 93.14%,respectively.The structure of the products was represented by UV-visible（UV-vis）absorption spectroscopy,Fourier transform infrared（FT-IR）spectroscopy,and nuclear magnetic resonance（NMR）spectroscopy.The above results exhibited that the target products HPCS-CA1–3 derivatives were successfully synthesized.Using Escherichia coli（E.coli）and Staphylococcus aureus（S.aureus）as the target bacteria,the results indicated that the antibacterial and antibiofilm activities of HPCS-CA derivatives were significantly better than those of CS and HPCS under the experimental conditions.The results of the cytotoxicity test showed that HPCS and HPCS-CA derivatives had good biocompatibility in vitro.2.In addition to hydroxypropyl,quaternary ammonium salting is also a simple chemical modification method to improve the water solubility of CS.Firstly,HTCC was prepared with a DS of 18.36%.Then,HTCC was chemically reacted with CA,and three HTCC-CA1–3derivatives with different CA binding rates were designed and synthesized by changing the molar ratios of HTCC and CA.The binding rates of CA were 15.45%,17.65%,and 22.39%,respectively.The molecular structure of the obtained products was identified by UV-vis,FT-IR,and ¹H NMR.The results indicated that HTCC-CA1–3 derivatives were successfully synthesized.The water solubility of HTCC-CA derivatives was better than that of CS and CA.Using E.coli as the target bacteria,the results exhibited that HTCC-CA derivatives had good flocculation and antibacterial effects.One of the possible mechanisms for the dual properties was electrostatic adsorption between the positively charged derivatives and the negatively charged E.coli,and the introduction of CA and the quaternary ammonium groups significantly enhanced the antibacterial activity of the derivatives.In addition,cytotoxicity test results showed that HTCC and HTCC-CA derivatives had good biocompatibility in vitro.HTCC-CA derivatives are CS-based derivatives with dual properties of flocculation and antibacterial,which can be used in water treatment and other fields.3.Using CS,HPCS,and HPCS-CA as raw materials and sodium tripolyphosphate（TPP）as the crosslinking agent,the nanoparticles were obtained by the ionic crosslinking method,namely CS Ps,HPCS Ps,and HPCS-CA Ps.Zeta potential and size measurements were performed.Morphology was observed.The results showed that the size distributions of the three particles were narrow,the surfaces were all positively charged,and the shapes were nearly spherical.The results of the cytotoxicity test showed that the biosafety of the synthesized particles was good in vitro.These three particles stabilized Pickering emulsions were prepared using soybean oil as an oil phase.Confocal laser scanning microscopy（CLSM）showed that the emulsions were oil-in-water（O/W）type.The stability of the emulsion prepared by HPCS-CA Ps was better than that of CS Ps.In addition,HPCS-CA Ps stabilized Pickering emulsion was used as the carrier to encapsulate curcumin,which improved the stability of curcumin.In conclusion,HPCS-CA and HTCC-CA derivatives which were prepared successfully by hydrophilic modification of CS and combination of CA to CS molecular structure,have excellent antibacterial and other functional properties.This research paper provides a strategy for the development of various CS-based derivatives and helps to broaden the application range of CS.