Activating the Antibacterial Effect of 4,6-Diamino-2-pyrimidinethiol-Modified Gold Nanoparticles by Reducing their Sizes.

Adequately decorated gold nanoparticles (GNPs) have excellent antibiotic activities against multidrug-resistant (MDR) bacteria. Nanoparticles exhibiting Gram selective antibacterial actions are beneficial to precise therapy. Here, we present a strategy to tune the antibacterial spectrum of a small molecule (4,6-diamino-2-pyrimidinethiol, DAPT)-modified GNPs (DAPT-GNPs, DGNPs) by adjusting their sizes. Compared to large (ca. 14 nm diameter) DGNPs (lDGNPs) and medium-sized (3-4 nm diameter) DGNPs (mDGNPs), which have no antibacterial effect or only target Gram-negative (G-) bacteria, ultrasmall DGNPs (uDGNPs, <2 nm) have a broad antibacterial spectrum, especially showing an over 60-fold increase in antibacterial efficacy against Gram-positive (G+) bacteria. Moreover, the uDGNPs-functionalized scaffolds (agarose gel) can serve as general wound dressings for healing burnt infections. Our strategy is insightful for exploring properties of the nanomaterials and their applications.