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Biodegradable Polymer Theranostic Fluorescent Nanoprobe for Direct Visualization and Quantitative Determination of Antimicrobial Activity
Version 2 2020-07-30, 14:40
Version 1 2020-06-30, 20:13
journal contribution
posted on 2020-07-30, 14:40 authored by Ruma Ghosh, Mehak Malhotra, Rupali Ravindra Madhuri Sathe, Manickam JayakannanWe report a biodegradable fluorescent theranostic nanoprobe design
strategy for simultaneous visualization and quantitative determination
of antibacterial activity for the treatment of bacterial infections.
Cationic-charged polycaprolactone (PCL) was tailor-made through ring-opening
polymerization methodology, and it was self-assembled into well-defined
tiny 5.0 ± 0.1 nm aqueous nanoparticles (NPs) having a zeta potential
of +45 mV. Excellent bactericidal activity at 10.0 ng/mL concentration
was accomplished in Gram-negative bacterium Escherichia
coli (E. coli) while
maintaining their nonhemolytic nature in mice red blood cells (RBC)
and their nontoxic trend in wild-type mouse embryonic fibroblast cells
with a selectivity index of >104. Electron microscopic
studies are evident of the E. coli membrane
disruption mechanism by the cationic NP with respect to their high
selectivity for antibacterial activity. Anionic biomarker 8-hydroxy-pyrene-1,3,6-trisulfonic
acid (HPTS) was loaded in the cationic PCL NP via electrostatic interaction
to yield a new fluorescent theranostic nanoprobe to accomplish both
therapeutics and diagnostics together in a single nanosystem. The
theranostic NP was readily degradable by a bacteria-secreted lipase
enzyme as well as by lysosomal esterase enzymes at the intracellular
compartments in <12 h and support their suitability for biomedical
application. In the absence of bactericidal activity, the theranostic
nanoprobe functions exclusively as a biomarker to exhibit strong green-fluorescent
signals in live E. coli. Once it became
active, the theranostic probe induces membrane disruption on E. coli, which enabled the costaining of nuclei by
red fluorescent propidium iodide. As a result, live and dead bacteria
could be visualized via green and orange signals (merging of red+green),
respectively, during the course of the antibacterial activity by the
theranostic probe. This has enabled the development of a new image-based
fluorescence assay to directly visualize and quantitatively estimate
the real-time antibacterial activity. Time-dependent bactericidal
activity was coupled with selective photoexcitation in a confocal
microscope to demonstrate the proof-of-concept of the working principle
of a theranostic probe in E. coli.
This new theranostic nanoprobe creates a new platform for the simultaneous
probing and treating of bacterial infections in a single nanodesign,
which is very useful for a long-term impact in healthcare applications.
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Keywords
ring-opening polymerization methodologytheranostic nanoprobe functionsExcellent bactericidal activityHPTSTime-dependent bactericidal activitytheranostic nanoprobe design strategytheranostic probecoli membrane disruption mechanismimage-based fluorescence assaybacteria-secreted lipase enzymelysosomal esterase enzymesBiodegradable Polymer TheranosticGram-negative bacterium Escherichia...cationic PCL NPRBCtheranostic nanoprobe
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