The Construction Of A Photothermal/photodynamic Multifunctional Nanosystem Of Composite Ag Nanoparticles And The Study Of Its Antibacterial Properties

In recent years,because of the antibiotic misuse and threats of the drug resistance,infection induced by bacteria is still one of the most ticklish clinical diseases in the world.As a result,researchers around the world have been seeking a new,safe,efficient and non-resistant antimicrobial method.Studies have shown that,compared to the traditional therapy,phototherapy systems including photothermal therapy(PTT)and photodynamic therapy(PDT)do not easily cause bacterial resistance.In view of this,a multi-functional nanocarriers(ZnPc/PDA@Ag NPs)combined with PTT/PDT and Ag nanoparticles was constructed by two methods which are reprecipitation-encapsulation and in-situ reduction.Among them,zinc titania(ZnPc)was used as a photosensitizer to produce singlet oxygen,polydopamine(PDA)was used as a photothermal agent to produce photothermal effect,and Ag nanoparticles were used as a direct antibacterial agent.Under the synergistic effect of PTT and PDT,the prepared nanocarriers was applied to Escherichia coli for antibacterial experiments,and the results showed that the combined therapy had better antibacterial effect.The main contents are as follows:1.GSDA,a photothermic dopamine derivative,was synthesized based on ring opening reaction of dopamine(DA)hydrochloride and epoxy siloxane.The characteristic functional group of GSDA was characterized by Fourier infrared spectroscopy.Multi-functional nanocarriers(ZnPc/PDA@Ag NPs)was prepared by loading ZnPc and GSDA onto poly(polylysine)-modified nanoparticles using reprecipitation-encapsulation method,and then growing Ag nanoparticles on the surface by in-situ reduction.The morphology,particle size and surface potential of the nanoparticles were characterized.The resultant ZnPc/PDA nanoparticles have a typical size of?152 nm with positive surface in aqueous solution.In addition,ZnPc/PDA@Ag NPs still have a positive surface,and the size of Ag NPs is about 10?20 nm.2.The photothermal and photodynamic properties of ZnPc/PDA@Ag multi-functional nanocarriers were characterized.Under the irradiation of 808 nm(1.0 W/cm2,10 min),the temperature of its aqueous solution rose rapidly by 21.9?,and the photothermal conversion efficiency reached 23.9%.Under the irradiation of 660 nm(15 mW/cm2,10 min),the fluorescence intensity of the singlet oxygen fluorescence probe SOSG increased linearly,indicating that multi-functional nanocarriers could effectively produce singlet oxygen.3.ZnPc/PDA@Ag NPs was applied to Escherichia coli,and we got a minimum antibacterial concentration of 12?g/mL.Subsequently,the antibacterial experiments of single-model and multi-mode were carried out by using NPs of 12?g/m.The results showed that the antibacterial effect of PTT or PDT combined with Ag NPs respectively were 84.4%?83.5%,and PTDT combined with Ag NPs had the best antibacterial effect,and the inhibition rate reached 96.5%.Finally,the biological compatibility of ZnPc/PDA@ Ag multi-functional nanocarriers was tested by MTT assay on living HUVEC,which shown that a dosage of<48?g/mL renders light growth inhibition of cells(the cell viability was higher than 80%).