We report a simple and economical colorimetric bacterial sensing strategy with catalytic amplification using dopamine-capped iron oxide (Dop-Fe3O4) nanoparticles. These nanoparticles catalyse the oxidation of a chromogenic substrate in the presence of H2O2 into a green colored product. The catalytic activity of the nanoparticles is inhibited in the presence of bacteria, providing naked eye detection of bacteria at 104 cfu/mL and by spectrophotometric detection down to 102 cfu/mL.
Bacterial
multidrug resistance (MDR) is a serious healthcare issue
caused by the long-term subtherapeutic clinical treatment of infectious
diseases. Nanoscale engineering of metal nanoparticles has great potential
to address this issue by tuning the nano–bio interface to target
bacteria. Herein, we report the use of branched polyethylenimine-functionalized
silver nanoclusters (bPEI–Ag NCs) to selectively kill MDR pathogenic
bacteria by combining the antimicrobial activity of silver with the
selective toxicity of bPEI toward bacteria. The minimum inhibitory
concentration of bPEI–Ag NCs was determined against 12 uropathogenic
MDR strains and found to be 10- to 15-fold lower than that of PEI
and 2- to 3-fold lower than that of AgNO3 alone. Cell viability
and hemolysis assays demonstrated the biocompatibility of bPEI–Ag
NCs with human fibroblasts and red blood cells, with selective toxicity
against MDR bacteria.
Copper nanoclusters (Cu NCs) are generally formed by several to dozens of atoms. Because of wide range of raw materials and cheap prices, Cu NCs have attracted scientists’ special attention. However, Cu NCs tend to undergo oxidation easily. Thus, there is a dire need to develop a synthetic protocol for preparing fluorescent Cu NCs with high QY and better stability. Herein, we report a one-step method for preparing stable blue-green fluorescent copper nanoclusters using glutathione (GSH) as both a reducing agent and a stabilizing agent. High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrospray ionization mass spectrometer (ESI-MS) were used to characterize the resulting Cu NCs. The as-prepared Cu NCs@GSH possess an ultrasmall size (2.3 ± 0.4 nm), blue-green fluorescence with decent quantum yield (6.2%) and good stability. MTT results clearly suggest that the Cu NCs@GSH are biocompatible. After incubated with EB-labeled HEK293T cells, the Cu NCs mainly accumulated in nuclei of the cells, suggesting that the as-prepared Cu NCs could potentially be used as the fluorescent probe for applications in cellular imaging.
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