Bacteria have been widely distributed in our living environment, and they also play an irreplaceable role. Some bacteria will pose a threat to human health. Therefore, it is very important to accurately monitor bacteria. At present, the technology based on molecular probe and fluorescence imaging has the characteristics of non-invasive, small damage, high specificity and sensitivity, which makes the bacterial imaging fluorescence probe widely used in bacterial detection.
Characteristics of Fluorescent Probes for Imaging Bacteria
The combination of the fluorophore and specific ligand of the fluorescent probes for imaging bacteria has high targeting ability, and a variety of fluorophores can ensure tunability and high signal-to-noise ratio. In addition, fluorescence imaging has higher sensitivity than radionuclide imaging. According to the type of fluorescent material, bacterial-responsive fluorescent probes mainly include inorganic fluorescent probes and organic fluorescent probes. Inorganic fluorescent probes, such as inorganic nanoparticles, quantum dots, and carbon-based nanoprobes, have been widely used in bioimaging due to their high photothermal stability, strong absorption, and remarkable electron mobility. Recently, fluorescent probes based on organic small-molecule fluorescent dyes are considered as one of the most effective fluorescent tools for detecting and imaging bacteria due to their high sensitivity, excellent biocompatibility and selectivity, simple operation, and easy modification of molecular structure. In addition, small organic molecules have low toxicity, and the probes in fluorescence imaging can be rapidly excreted in vivo.
Application of Fluorescent Probes for Imaging Bacteria
These fluorescent probes for imaging bacteria typically detect bacteria by targeting bacterial surfaces, cell walls, proteins, nucleic acids, and enzymes. For example, positively charged alegen and conjugated oligomers target bacterial surface forces through electrostatic and hydrophobic interactions. Fluorescent probes synthesized from boronic acid derivatives and commonly used antibiotics such as vancomycin and polymyxin can label carbohydrates and lipids in cell walls. The synthesis of PG, LPS, and lipid-essential monomers such as DAA, KOD, and UDP-MurNAc can serve as metabolic probes involved in cell wall metabolism. In addition, some carbohydrate-derived fluorescent molecules, such as trehalose probes, can be transported to specific bacteria via secreted proteins. Of course, the understanding of macromolecules within bacterial cells is significant. Some molecules that fluoresce from unnatural amino acids, chemoenzymes, and specific peptide ligands create ideal conditions for super-resolution imaging of proteins.