Preparation And Properties Of Carriers For Chlorin E6 Photosensitizer Based On Chitosan

Photodynamic antibacterial is a method that relies on active oxygen produced by photosensitizers for antibacterial.Most photosensitizers are insoluble in water and lack bacterial affinity,which limits their application in actual antibacterial applications.Therefore,it is necessary to develop a carrier that can enhance the water solubility and bacterial affinity of photosensitizers.In this article,the preparation and performance research of three Ce6photosensitizer carriers based on CS were carried out.The main research results are as follows:(1)CS was used as the carrier of Ce6 through the amide reaction,and the antibacterial effects to typical gram-negative and gram-positive bacteria were studied at different degree of substitution(DS).Three CS-Ce6 conjugates with different DS(6.44%～11.68%)were synthesized through changing the molar ratio of Ce6 to CS.The Ultraviolet-visible(UV-vis)absorption spectroscopy,Fourier transform infrared(FT-IR)spectroscopy,and Proton nuclear magnetic resonance(~1H NMR)spectroscopy showed that the CS-Ce6 conjugates were successfully synthesized;1,3-Diphenylisobenzofuran(DPBF)as a probe in the detection of reactive oxygen species(ROS)showed that products have a good ability to generate ROS;The antibacterial experiments showed that the minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of the products against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)were lower than CS and Ce6,which indicating the products had stronger antibacterial ability.The antibacterial effect of products could be enhanced by extending the laser irradiation time and higher DS;The products showed lower cytotoxicity than Ce6 in the cytotoxicity experiment.(2)The application of CS-Ce6 conjugates was limited by its poor water solubility,to obtain protuct with better water solubility,the CS was hydroxypropylated to obtain hydroxypropyl CS(HPC).HPC was used as the carrier of Ce6 through the amide reaction,and the antibacterial effects to typical gram-negative and gram-positive bacteria were studied at different binding amounts of Ce6.Three HPC-Ce6 conjugates with different binding amounts of Ce6(1.35%～2.82%)were synthesized through changing the mass ratio of Ce6 to HPC.The UV-vis absorption spectroscopy,FT-IR spectroscopy,and 1H NMR spectroscopy showed that the HPC-Ce6 conjugates were successfully synthesized;The detection experiment of ROS showed that products have a good ability to generate ROS;The antibacterial experiments showed that the MIC and MBC of the products against E.coli and S.aureus were lower than HPC and Ce6,which indicating the products had stronger antibacterial ability.The antibacterial effect of products could be enhanced by extending the laser irradiation time and higher binding amount of Ce6;The products showed lower cytotoxicity than Ce6 in the cytotoxicity experiment.(3)Besides the direct combination of carriers and Ce6,we also tried to prepare CS nanoparticles(CS NPs)by the ionic cross-linking between CS and sodium tripolyphosphate(TPP)and compared the chemical and physical products(CS-Ce6 NPs and CS/Ce6 NPs).The CS NPs,CS-Ce6 NPs and CS/Ce6 NPs all showed uniform distribution and good dispersion;The UV-vis absorption spectroscopy and FT-IR spectroscopy showed that the products were successfully synthesized;CS/Ce6 NPs showed faster rate of ROS generation than CS-Ce6 NPs under short irradiation time in the ROS detection experiment;The antibacterial experiments showed that CS-Ce6 NPs and CS/Ce6 NPs have stronger antibacterial ability than CS NPs,and CS/Ce6 NPs has a stronger antibacterial power to S.aureus than CS-Ce6 NPs.CS/Ce6 NPs showed better antibacterial effect than CS-Ce6 conjugates and HPC-Ce6 conjugates at the same binding amount of Ce6;The products showed no lower cytotoxicity in the cytotoxicity experiment.