Abstract
In this study, bifunctional organosilica nanoparticles bearing thiol and amine functionalities were synthesized, PEGylated, and subsequently functionalised with aromatic aldehydes via Schiff base formation. The nanoparticles were prepared by an Ouzo effect-based nanoprecipitation method using 3-mercaptopropyltrimethoxysilane and 3-aminopropyltrimethoxysilane as precursors. Comprehensive physicochemical characterisation was performed using dynamic light scattering, nanoparticle tracking analysis, transmission electron microscopy, ζ-potential measurements, Ellman's and 4-nitrobenzaldehyde assays, FTIR spectroscopy, and X-ray diffraction. PEGylation markedly improved colloidal stability, resulting in aggregation-free dispersions across a broad pH range. In vivo toxicological assessment using Schmidtea mediterranea planaria demonstrated good biocompatibility of all nanoparticle formulations, with no evidence of epithelial barrier disruption. Antimicrobial activity was evaluated in vitro against Staphylococcus aureus. Nanoparticles functionalised with aromatic aldehydes exhibited pronounced antibacterial activity, whereas PEGylated nanoparticles showed only weak effects and non-functionalised nanoparticles were inactive.