Maltose-Derivatized Fluorescence Turn-On Imaging Probe for Bacteria Detection

Area of Science:

• Chemical Biology
• Microbiology
• Biotechnology

Background:

• Rapid and selective bacterial detection is crucial for clinical diagnostics and food safety.
• Existing methods often require complex equipment or lengthy incubation periods.
• Fluorescence-based probes offer potential for sensitive and specific bacterial identification.

Purpose of the Study:

• To develop a novel fluorescence turn-on probe for the detection of specific bacterial species.
• To investigate the mechanism of probe uptake and activation in bacteria.
• To evaluate the probe's performance for detecting bacteria in various conditions, including spiked food samples.

Main Methods:

• Synthesis of a maltose-derivatized carbazole probe (Mal-Cz) with a perfluoroaryl azide group.
• Photoactivation of the probe via intramolecular C-H insertion reaction.
• Confocal fluorescence microscopy to confirm probe uptake by bacteria.
• Testing probe selectivity against a panel of Gram-positive and Gram-negative bacteria.
• Evaluating detection limits using a hand-held UV lamp and naked-eye observation.
• Assessing probe performance in spiked milk samples.
• Investigating the role of bacterial metabolic activity and maltose transport systems in probe uptake.

Main Results:

• Mal-Cz demonstrated a fluorescence turn-on mechanism upon photoactivation.
• The probe was successfully internalized by metabolically active *E. coli* and *Staphylococci*.
• Mal-Cz selectively detected *E. coli* and *S. epidermidis* in the presence of other bacteria like *P. aeruginosa* and *M. smegmatis*.
• Detection limit of 10^3 CFU/mL was achieved with a hand-held UV lamp and naked-eye observation.
• The probe successfully detected bacteria spiked in milk samples.
• Probe uptake was dependent on metabolically active bacteria and hijacked maltose uptake pathways, involving LamB, MBP, and MalFGK2 transporter in *E. coli*.

Conclusions:

• Mal-Cz is an effective fluorescence turn-on probe for the rapid, selective, and sensitive detection of *E. coli* and *S. epidermidis*.
• The probe's mechanism relies on bacterial metabolic activity and specific maltose transport systems.
• Its usability with a hand-held UV lamp and naked-eye detection makes it suitable for point-of-care or field applications.