Proanthocyanin-Capped Biogenic TiO2 Nanoparticles with Enhanced Penetration, Antibacterial and ROS Mediated Inhibition of Bacteria Proliferation and Biofilm Formation: A Comparative Approach.

Biofunctionalized TiO2 nanoparticles with a size range of 18.42±1.3 nm were synthesized in a single-step approach employing Grape seed extract (GSE) proanthocyanin (PAC) polyphenols. The effect of PACs rich GSE corona was examined with respect to 1) the stability and dispersity of as-synthesized GSE-TiO2 -NPs, 2) their antiproliferative and antibiofilm efficacy, and 3) their propensity for internalization and reactive oxygen species (ROS) generation in urinary tract infections (UTIs) causing Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus saprophyticus strains. State-of-the-art techniques were used to validate GSE-TiO2 -NPs formation. Comparative Fourier transformed infrared (FTIR) spectral analysis demonstrated that PACs linked functional -OH groups likely play a central role in Ti4+ reduction and nucleation to GSE-TiO2 -NPs, while forming a thin, soft corona around nascent NPs to attribute significantly enhanced stability and dispersity. Transmission electron microscopic (TEM) and inductively coupled plasma mass-spectroscopy (ICP-MS) analyses confirmed there was significantly (p<0.05) enhanced intracellular uptake of GSE-TiO2 -NPs in both Gram-negative and -positive test uropathogens as compared to bare TiO2 -NPs. Correspondingly, compared to bare NPs, GSE-TiO2 -NPs induced intracellular ROS formation that corresponded well with dose-dependent inhibitory patterns of cell proliferation and biofilm formation in both the tested strains. Overall, this study demonstrates that -OH rich PACs of GSE corona on biogenic TiO2 -NPs maximized the functional stability, dispersity and propensity of penetration into planktonic cells and biofilm matrices. Such unique merits warrant the use of GSE-TiO2 -NPs as a novel, functionally stable and efficient antibacterial nano-formulation to combat the menace of UTIs in clinical settings.