Uridine-capped silver nanoparticles: biocompatible antibacterial agents with real time monitoring using ^99mTc-SPECT

The rising prevalence of multidrug-resistant bacteria underscores the urgent need to develop novel antibacterial agents. This work reports the synthesis, comprehensive characterization, antibacterial efficacy, radiolabeling efficiency and bacterial infection gamma imaging of uridine functionalized silver nanoparticles (DAU_SH-Ag_NPs). The silver nanoparticles were synthesized using a chemical reduction method and functionalized with thiol-modified uridine. Spectroscopic analysis confirmed successful surface functionalization and the presence of stable spherical nanoparticles with a hydrodynamic diameter of 51.5 ± 14.7 nm and a zeta potential of -29.3 ± 10.2 mV. DAU_SH-Ag_NPs exhibited potent antibacterial activity, demonstrating low minimum inhibitory concentration (MIC) against both Staphylococcus aureus (MIC = 0.56 mg mL^-1) and Escherichia coli (MIC = 2.06 mg mL^-1). Importantly, the nanoconjugate also exhibited low haemocytotoxicity and low cytotoxicity in mammalian fibroblast cells, confirming a favorable safety profile for systemic application. Furthermore, DAU_SH-Ag_NPs achieved a high radiolabeling efficiency of 95% with 99m-Technetium (^99mTc). Preliminary blood kinetics and biodistribution studies confirmed its potential as an imaging agent, and the gamma imaging also confirmed the presence of a radioactivity signal localized at the site of bacterial infection. These dual-function evaluations confirm that DAU_SH-Ag_NPs effectively serves as a promising biocompatible theranostic modality for concurrent diagnosis and treatment of challenging bacterial infections.