Interfacial uploading of luminescent hexamolybdenum cluster units onto amino-decorated silica nanoparticles as new design of nanomaterial for cellular imaging and photodynamic therapy

The present work introduces a facile synthetic route to embed phosphorescent K-2[{Mo6I8}I-6] and (nBu(4)N)(2)[{Mo6I8}(CH3COO)(6)] clusters (C) onto silica-water interface of amino-decorated silica nanoparticles (SNs, 60 +/- 6 nm). The assembled C-SNs gain in the luminescence intensity, which remains stable within three months after their assembly. High uptake capacity of the clusters (8700 of K-2 ([{Mo6I8)I-6] and 6500 of (nBu(4)N)(2)[{Mo6I8}(CH3COO)(6)] per the each nanoparticle)derives from ionic self-assembly and coordination bonds between the cluster complexes and ionic (amino- and siloxy-) groups at the silica surface. The coordination via amino- or siloxy-groups restricts aquation and hydrolysis of the embedded clusters, in comparison with the parent K-2[{Mo6I8}I-6] and (nBu(4)N)(2)[{Mo6I8)(CH3COO)(6). High potential of the assembled nanoparticles in the ROS generation was revealed by EPR measurements facilitated by spin trapping. The high positive charge and convenient colloid stability of the assembled C-SNs hybrids are the prerequisite for their efficient cellular uptake, which is exemplified in the work by MCF-7 cell line. The measured dark and photoinduced cytotoxicity of the C-SNs hybrids reveals significant photodynamic therapy effect on the MCF-7 cancer cell line versus the normal cells. This effect is entirely due to the embedded clusters and is dependent on the chemical composition of the cluster. (C) 2018 Elsevier Inc. All rights reserved.