Abstract
Abstract Magnetic nanoparticles of Fe 3 O 4 (MNP) were synthesized by co-precipitating Fe 2+ and Fe 3+ ions in an ammonia solution. This MNP was coated with silica using sodium metasilicate to obtain silica-coated MNP (MNPSi). Grafting of aminopropyl groups on MNP or MNPSi was performed with (3-aminopropyl)trimethoxysilane to form MNPNH 2 or MNPSiNH 2 , respectively. 5,10,15,20-Tetrakis(4-carboxyphenyl)porphyrin (TCPP) was covalently bound onto the MNPNH 2 or MNPSiNH 2 via carbodiimide activation to obtain MNPNH-TPCC or MNPNH-TPCC, respectively. These MNP presented an average diameter of about 15 nm. UV–vis absorption spectra presented the characteristic Soret and Q bands of TCPP covalently linked to the nanoparticles. The MNP containing TCPP produced a high photodecomposition of 2,2-(anthracene-9,10-diyl)bis(methylmalonate), which was used to detect singlet molecular oxygen O 2 ( 1 Δ g ) production in water. Moreover, these nanoparticles sensitized the photooxidation of L-tryptophan in water, mainly mediated by a type II photoprocess. Photoinactivation of microorganisms was investigated in Staphylococcus aureus , Escherichia coli and Candida albicans . In vitro experiments showed that photosensitized inactivation induced by MNPSiNH-TCPP improved with an increase of irradiation times. After 30 min irradiation, a 2.5 log reduction was found for S. aureus and C. albicans . Also, the last conditions produced a decrease of 3 log in E. coli . Similar result was obtained MNPNH-TCPP. However, the main difference between these nanoparticles as photosensitizer was found after recycling experiments. While the photoinactivation mediated by MNPNH-TCPP rapidly decrease after one cycle, MNPSiNH-TCPP was still efficient after three cycles of inactivation. Therefore, MNPSiNH-TCPP is an interesting and versatile photodynamic active material to eradicate microorganisms.
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