Highly fluorescent, photostable, and biocompatible silicon theranostic nanoprobes against Staphylococcus aureus infections

Human health is severely threatened by bacterial infections, which fuel urgent demand for the development of novel theranostic agents that are suitable for diagnosing and combating bacterial infections. To meet this goal, we synthesized a new kind of theranostic probes, made of vancomycin (Van)-modified fluorescent silicon nanoparticles (SiNPs-Van). The new probes feature good selectivity for Gram-positive bacterial infections, favorable fluorescence, strong resistance to photobleaching (e.g., 12% loss of fluorescence intensity during 40 min continuous laser excitation in the presence of Staphylococcus aureus (S. aureus)), and good biocompatibility (e.g., cell viability > 95% during 24 h treatment). Because of these benefits, the probes were effective at prolonged (i.e., 8-day) fluorescence tracking of S. aureus infections in vivo, thus providing a visible and accurate way to evaluate treatment efficacy. Moreover, the resultant SiNPs-Van with a minimum inhibitory concentration (MIC) of ca. 0.5 μg/mL exhibited high antibacterial efficiency of 92.5%, superior to that (76.5%) of free Van with higher MIC of ca. 1 μg/mL.