Synthesized aminoglycoside-conjugated silica nanoparticles exhibit enhanced antimicrobial activity against clinical and resistant bacteria with minimal cytotoxicity.

Bacterial infections pose a major threat to human health, primarily because of the evolution of mutated strains that are resistant to antibiotic treatment. As a viable alternative, several nanoparticles have emerged as attractive antibacterial agents. Herein, we report the development of iron sulfide (FeS) nanoparticles that show dual-modality therapy: namely reactive oxygen species (ROS)-induced toxicity and red-laser induced photothermal therapy. The aqueous synthesized nanoparticles have been characterized based on their size, shape, crystallinity, and magnetic and optical properties. These nanoparticles showed sustained release of Fe2+ ions in an aqueous dispersion. They also have a high absorption cross-section in the visible and near infra-red regions and could be excited by a continuous wave diode laser of wavelength 635 nm leading to significant hyperthermia. Nanoparticle treatment, followed by light irradiation, led to significant cell death in two ghastly pathogenic bacterial strains. Stepwise enhancement of intrabacterial ROS levels, as a result of nanoparticle treatment followed by light activation, has been identified as the primary antibacterial mechanism.

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Iron oxide nanoparticles have unique magnetic properties and therefore readily respond to applied magnetic fields. Moreover, their surfaces can be used to attach active molecules via various covalent or noncovalent interactions. Thus, they can be used as drug carriers for magnetically controlled delivery to specific biological sites of interest. In the present study, we have synthesized aqueous dispersed samples of citric acid-capped iron oxide nanoparticles, and the anticancer drug doxorubicin was then linked with these superparamagnetic iron oxide nanoparticles via a simple noncovalent interaction. Our results show that the conjugated drug releases from the nanoparticles in a sustained manner. The cellular uptake of these nanoparticles was found to be substantial, although it can be further enhanced using magnetic guidance. These nanoparticles (drug free) were found to be nontoxic to cells; however, upon drug conjugation, drug-induced toxicity was observed, owing to the slow release of drug from the nanoparticles.