Fluorescent AgNCs Formed on Bifunctional DNA Template for Potassium Ion Detection

In this study, we examined properties of silver nanoclusters, which are AgNCs stabilized by DNA oligonucleotide scaffold containing G-quadruplex-forming sequences: human telomeric (Tel22) or thrombin-binding aptamer (TBA). Thus, we obtained two fluorescent probes abbreviated as Tel22C12-AgNCs and TBAC12-AgNCs, which were characterized using absorption, circular dichroism and fluorescence spectroscopy. Both probes emit green and red fluorescence. The presence of silver nanoclusters did not destabilize the formed G-quadruplexes. The structural changes of probes upon binding K+ or Na+ ions cause quenching in their red emission. Green emission was slightly quenched only in the case of Tel22C12-AgNCs; on the contrary, for TBAC12-AgNC’s green emission, we observed an increasing fluorescence signal. Moreover, the Tel22C12-AgNCs system shows not only a higher binding preference for K+ over Na+, but it was able to monitor small changes in K+ concentrations in the buffer mimicking extracellular conditions (high content of Na+ ions). These results suggest that Tel22C12-AgNCs exhibit the potential to monitor transmembrane potassium transport.

Beyond homeostasis: potassium and pathogenesis during bacterial infections

Potassium is an essential mineral nutrient required by all living cells for normal physiological function. Maintaining intracellular potassium homeostasis during bacterial infection is therefore a requirement for the survival of both host and pathogen. However, pathogenic bacteria require potassium transport not only to fulfill nutritional and chemiosmotic requirements, but potassium has been shown to directly modulate virulence gene expression, antimicrobial resistance, and biofilm formation. Host cells also require potassium to maintain fundamental biological processes as such as renal function, muscle contraction, and neuronal transmission, however, potassium flux also contributes to critical immunological and antimicrobial processes such as cytokine production and inflammasome activation. Here we review the role and regulation of potassium transport and signaling during infection in both mammalian and bacterial cells and highlight the importance of potassium to the success and survival of each organism.