Identification of bacterial strains is critical for the theranostics of bacterial infections and the development of antibiotics. Many organic fluorescent probes have been developed to overcome the limitations of conventional detection methods. These probes can detect bacteria with “off-on” fluorescence change, which enables the real-time imaging and quantitative analysis of bacteria in vitro and in vivo. In this review, we outline recent advances in the development of fluorescence-based dyes capable of detecting bacteria. Detection strategies are described, including specific interactions with bacterial cell wall components, bacterial and intracellular enzyme reactions, and peptidoglycan synthesis reactions. These include theranostic probes that allow simultaneous bacterial detection and photodynamic antimicrobial effects. Some examples of other miscellaneous detections in bacteria have also been described. In addition, this review demonstrates the validation of these fluorescent probes using a variety of biological models such as gram-negative and -positive bacteria, antibiotic-resistant bacteria, infected cancer cells, tumor-bearing, and infected mice. Prospects for future research are outlined by presenting the importance of effective in vitro and in vivo detection of bacteria and development of antimicrobial agents.
Aromatic nitro compounds are reduced
to their corresponding amino
derivatives by nitroreductases (NTR), while identification and characterization
of the corresponding enzymes in mammalian systems are yet unrevealed.
However, mammalian NTR activity has been considered as a favorable
target in development of theranostic agents for cancer and hypoxia
of solid tumors. Currently, small molecule-based fluorescent probes
have emerged as a valuable assay tool for NTR activity. However, there
has been a limit to comparing NTR activity between different cells,
since most probes have relied on fluorescence changes that are affected
by not only enzymatic activity but also nonenzymatic factors. Here,
we developed a self-calibrating bipartite fluorescent probe, consisting
of NTR-sensitive nitronaphthalimide and nonsensitive coumarin moieties.
Thereby, it was possible to compare the relative NTR activity by monitoring
fluorescence ratios in noncancerous and some cancerous cells and to
demonstrate for certain that the elevated NTR activity is associated
with cancer cells and hypoxia states.
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