Magnetic nanoplatforms for in situ modification of macromolecules: synthesis, characterization and photoinactivating power of cationic nanoiman-porphyrin conjugates

SCANONE, ANA CORAL; GSPONER, NATALIA SOLEDAD; ALVAREZ, MARIA GABRIELA; HEREDIA, DANIEL ALEJANDRO; DURANTINI, ANDRÉS M.; DURANTINI, EDGARDO NÉSTOR

ACS Applied Bio Materials

ACS Paragon Plus Environment

Año: 2020

2576-6422

Nanoplatform concept was developed to synthesized accessible photoactive magnetic nanoparticles (MNPs) of Fe3O4 coated with silica. This approach was based on the covalent binding of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPPF20) to aminopropyl-grafted MNPs by nucleophilic aromatic substitution reaction (SNAr) to obtain conjugate MNP-P1. After in situ modification, the remaining pentafluorophenyl groups of TPPF20 attached to MNPs were substituted by dimethylaminoethoxy groups to form MNP-P2. The basic amine group of these conjugates can be protonated in aqueous media. In addition, MNP-P1 and MNP-P2 were intrinsically charged to produce cationic conjugates MNP+ -P1 and MNP+ -P2+ by methylation. All of them were easily purified by magnetic decantation in high yields. The average size of the MNPs was ~15 nm and the main difference between these conjugates was the greater coating with positive charges of MNP+ - P2+ , as showed by the zeta potential values. Absorption spectra exhibited the Soret and Q bands characteristic of TPPF20 linked to MNPs. Furthermore, these conjugates showed red fluorescence emission of porphyrin with quantum yields of 0.011-0.036. The photodynamic effect sensitized by the conjugates indicated the efficient formation of singlet molecular oxygen in different media, reaching quantum yields values of 0.17-0.34 in N,N-dimethylformamide. The photodynamic activity of the conjugates was evaluated to inactivate the Gram-positive bacteria Staphylococcus aureus, the Gram-negative bacteria Escherichia coli and the yeast Candida albicans. The modified cationic MNP+ -P2+ was the most effective conjugate for photodynamic inactivation (PDI) of microorganisms. Binding of this conjugate to bacteria and photoinactivation capability was checked by means of fluorescence microscopy. Also, sustainable use by recycling was determined after three PDI treatments. Therefore, this methodology is a suitable scaffold for the in situ modification of conjugates and in particular, MNP+ -P2+ represents a useful photodynamic active material to eradicate microorganisms.