Silver is commonly
used in wound dressing, photography, health
care products, laboratories, pharmacy, biomedical devices, and several
industrial purposes. Silver (Ag+) ions are more toxic pollutants
widely scattered in the open environment by natural processes and
dispersed in soil, air, and water bodies. Ag+ binds with
metallothionein, macroglobulins, and albumins, which may lead to the
alteration of various enzymatic metabolic pathways. To analyze the
uptake and metabolism of silver ions in vitro as well as in cells,
a range of high-affinity fluorescence-based nanosensors has been constructed
using a periplasmic protein CusF, a part of the CusCFBA
efflux complex, which is involved in providing resistance against
copper and silver ions in Escherichia coli. This nanosensor was constructed by combining of two fluorescent
proteins (donor and acceptor) at the N- and C-terminus of the silver-binding
protein (CusF), respectively. SenSil (WT) with a
binding constant (K
d) of 5.171 μM
was more efficient than its mutant variants (H36D and F71W). This
nanosensor allows monitoring the level of silver ions in real time
in prokaryotes and eukaryotes without any disruption of cells or tissues.