Bacterial imaging and photodynamic inactivation using zinc(ii)-dipicolylamine BODIPY conjugates

Abstract

Targeted imaging and antimicrobial photodynamic inactivation (PDI) are emerging methods for detecting and eradicating pathogenic microorganisms. This study describes two structurally related optical probes that are conjugates of a zinc(II)-dipicolylamine targeting unit and a BODIPY chromophore. One probe is a microbial targeted fluorescent imaging agent, mSeek, and the other is an oxygen photosensitizing analogue, mDestroy. The conjugates exhibited high fluorescence quantum yield and singlet oxygen production, respectively. Fluorescence imaging and detection studies examined four bacterial strains: E. coli, S. aureus, K. pneumonia, and B. thuringiensis vegetative cells and purified spores. The fluorescent probe, mSeek, is not phototoxic and enabled detection of all tested bacteria at concentrations of ~100 CFU/mL for B. thuringiensis spores, ~1000 CFU/mL for S. aureus and ~10,000 CFU/mL for E. coli. The photosensitizer analogue, mDestroy, inactivated 99–99.99% of bacterial samples and selectively killed bacterial cells in the presence of mammalian cells. However, mDestroy was ineffective against B. thuringiensis spores. Together, the results demonstrate a new two-probe strategy to optimize PDI of bacterial infection/contamination.

Nanoparticle targeting of Gram-positive and Gram-negative bacteria for magnetic-based separations of bacterial pathogens

“…Targeting ligands include vancomycin which targets peptidoglycans found on Grampositive bacteria, polymyxin which targets lipopolysaccharides found on Gram-negative bacteria, or zinc(II)-bis(dipicolylamine) (ZnDPA) which targets phosphatidylserine found on the surface of both Gram-positive and Gram-negative bacteria (Choi et al 2013;Hanshaw and Smith 2005;Kell et al 2008;Wong et al 2015). Importantly, these ligand targets are not found on the surface of healthy mammalian cells, which allows for specific binding and imaging of bacteria with minimal background signals when using these targeting ligands in vivo (Rice et al 2015;van Oosten et al 2013). Recent novel uses of targeted NPs include the binding and magnetic separation of bacteria from solution to treat bacterial sepsis, by passing NPs through custom-made microfluidic devices (Lee et al 2014).…”

Zinc(II)-Dipicolylamine Coordination Complexes as Targeting and Chemotherapeutic Agents for Leishmania major

“…S2 and S3 in the supplemental material). The cytosolic distribution contrasts with that seen in planktonic bacteria, where mSeek localizes primarily in the bacterial envelope with no internalization (33). In vitro toxicity assays with eight different ZnDPA complexes revealed strong to moderate antileishmanial activity with minimal mammalian cell cytotoxicity ( Fig.…”

“…The targeted fluorescent ZnDPA probe mSeek, nontargeted fluorescent Control Dye, and all ZnDPA complexes tested were synthesized as previously reported (22,33). Microscopy slides and coverslips were purchased from Thermo Scientific.…”

“…Fluorescent ZnDPA probes are effective imaging agents for dead and dying mammalian cells (which expose anionic phosphatidylserine) in a range of cell culture systems and small animal models of disease (19)(20)(21)(22)(23)(24)(25)(26). ZnDPA probes also target the anionic surfaces of bacteria, and they have been used for imaging infection in animal models (27)(28)(29)(30)(31)(32)(33). Some ZnDPA complexes are known to have antibiotic activity due to their capacity to disrupt bacterial membranes (31).…”

Antiplasmodial activity of targeted zinc(II)-dipicolylamine complexes

“…ZnDPA targeting of iRBC was explored using the green fluorescent probe mSeek which was shown previously to stain bacteria and Leishmania parasites. [27, 30] Samples of red blood cells (10 4 cells per mL) infected with P. Falciparum W2 were treated with Hoechst nuclear stain which selectively localizes to iRBCs through binding parasite DNA. The same samples were co-treated with mSeek (5 μM) in HEPES buffer.…”