Sensitive Detection of Broad-Spectrum Bacteria with Small-Molecule Fluorescent Excimer Chemosensors

Abstract

Antibiotic resistance is a major problem for world health, triggered by the unnecessary usage of broad-spectrum antibiotics on purportedly infected patients. Current clinical standards require lengthy protocols for the detection of bacterial species in sterile physiological fluids. In this work, a class of small-molecule fluorescent chemosensors termed ProxyPhos was shown to be capable of rapid, sensitive, and facile detection of broad-spectrum bacteria. The sensors act via a turnon fluorescent excimer mechanism, where close-proximity binding of multiple sensor units amplifies a red shift emission signal. ProxyPhos sensors were able to detect down to 10 CFUs of model strains by flow cytometry assays and showed selectivity over mammalian cells in a bacterial coculture through fluorescence microscopy. The studies reveal that the zinc(II)-chelates cyclen and cyclam are novel and effective binding units for the detection of both Gram-negative and Gram-positive bacterial strains. Mode of action studies revealed that the chemosensors detect Gram-negative and Gram-positive strains with two distinct mechanisms. Preliminary studies applying ProxyPhos sensors to sterile physiological fluids (cerebrospinal fluid) in flow cytometry assays were successful. The results suggest that ProxyPhos sensors can be developed as a rapid, inexpensive, and robust tool for the "yes−no" detection of broad-spectrum bacteria in sterile fluids.

Rapid Bacterial Recognition over a Wide pH Range by Boronic Acid-Based Ditopic Dendrimer Probes for Gram-Positive Bacteria

“…The dpa group, which is a phosphate sensor, forms a complex with phosphate and metal ions such as Cu 2+ [ 22 ] or Zn 2+ [ 23 ]. One research group has recently reported that some bacterial components were detected by dpa sensors using flow cytometry analysis [ 24 ]. The electrostatic interaction between the cationic amine group and the negatively charged bacterial surface has also been studied [ 25 , 26 ].…”

Argentivorous Molecules with Chromophores in Side Arms: Silver Ion-Induced Turn On and Turn Off of Fluorescence

“…Excimer is defined as a dimer associated with an excited electronic state and dissociative in its ground electronic state. − Generally, the excimer band shows a red shift compared with a monomer because of the increasing electron affinity of the acceptor and decreasing the donor’s ionization potential. − Using the fluorescence properties of excimers, the fluorescent sensor molecules for heavy and transition metals have been extensively developed. − Among well-known fluorophores, anthracene, pyrene, and their derivatives have been investigated into many functions for sensing metal ions, pH, simple inorganic anions, and small organic molecules. − Pyrene is strong electron donor material, and pyrene excimer from several pyrene derivatives usually exhibits a similar emission color of sky-blue or cyan, resulting from almost the same excited-state geometry. − Since excellent monomer and excimer emission changes occur at remarkably different wavelengths on the basis of the distance between two anthracene or pyrene moieties, both fluorophores (anthracene and pyrene) acting as a fluorophore have been utilized effectively. − …”

Rapid measurement of waterborne bacterial viability based on difunctional gold nanoprobe

“…10,11 Fluorescent methods employ various organic dyes to differentiate living and dead bacterial cells. [12][13][14][15] Although rapid and easy to operate, these uorescent methods rely on costly uorescent dyes and require complex instruments such as laser scanning confocal microscopy 16 or ow cytometry, 17 which impede their widespread applications in resource-limited regions. Therefore, there is an urgent need to develop a rapid, simple, and low-cost method for measuring bacterial viability.…”