Comparative Study on Photodynamic Activation of Ortho-Toluidine Blue and Methylene Blue Loaded Mesoporous Silica Nanoparticles Against Resistant Microorganisms | Bentham Science

摘要

Aims and background: The number of pathogenic microorganisms has been increasingover the years, and so as resistance of these microorganisms are developing against various antibiotics.Antimicrobial photodynamic therapy (aPDT), also called photodynamic inactivation, is emergingas a promising alternative to treatments based on conventional antibiotics. Recent patents on structuredsilver mesoporous silica nanoparticles having antimicrobial activity (WO2010/071831 A2), photosensitisermodified core-shell structure nanocomposites (CN 103536935(A)), and Chitosan-coatedmagnetic mesoporous silica nanoparticles (CN 104785214(A)) helped in selecting method of synthesisof MSN and photosensitizers.Materials and methods: MSN were synthesised by Sol-Gel method and amino functionalised (APTES).Methylene blue (MB) and ortho-toluidine blue (O-TB) were used as photosensitisers. Differentbatches were synthesised. The final product was characterised by using FTIR, BET, SEM, time resolvedfluorescence. The photosensitiser loaded MSN were illuminated by LED based lamp emittingred light at 620± 20nm for different time lengths viz 15 min and 30 mins. Fluorescence studies and antimicrobialassays were carried out as per 72 well plate method I.P, 2014 using, gram negative E. coli(ATCC no. 8739), S. aureus (ATCC no. 7447) and gram positive P. aeruginosa (ATCC no. 9027)pathogenic microorganisms.Results: MB and O-TB were successfully adsorbed on APTES functionalised MSN. Different exposuretime length of the photosensitisers to red light showed different zone of inhibition. MB and O-TBloaded MSN showed significant increase in zone of inhibition after irradiation as compared to MB andO-TB loaded on MSN without exposure to light.Conclusion: MB and O-TB adsorbed on APTES functionalized mesoporous silica nanoparticles werecapable of efficiently inactivating E. coli, P. aeruginosa, S. aureus bacteria upon exposure to red light(620± 20nm wavelength) at a much lower concentration. Mesoporous silica nanoparticles played animportant role in aPDT due to their high surface area and porous structure. Also, APTES functionalizationresulted in the pore expansion of MSN, thereby increasing the loading capacity of the photosensitizeron MSN. From the results obtained it can be concluded that O-TB loaded MSN showed higher activityagainst gram negative and positive microorganisms microorganism as compared to that of MB.