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Discovery & Development Drug Delivery

Elimination by Illumination

Are we on the cusp of a grim future in which pan-drug resistant superbugs roam freely, unfazed by antibiotics? With some bacteria having already become resistant to all drugs, some researchers are warning against a coming antibiotic apocalypse... But in the hopes of holding off the dystopia, scientists from the University of Colorado Boulder have used “light-activated nanotherapy” to kill multi-drug resistant bacteria (1). 

“During our previous studies, my colleague and I were designing nanoparticles to generate tuneable redox species,” says Anushree Chatterjee, Assistant Professor of chemical and biological engineering at Colorado Boulder. “When working on diagnosing disease cells, we realized that drug resistant strains were susceptible to certain redox potentials/species, which led us to design nanoscale semiconductor nanoparticles – or quantum dots – as therapeutics with specificity for bacterial infections, while leaving the mammalian host intact.” 

Small quantum dots deliver their therapeutic effect by freely diffusing inside bacteria when added in very small concentrations. When the dots are activated with light, they produce redox species that disturb redox homeostasis of the bacteria. “We show that nanomolar concentrations and a weak light source is enough to kill 92 percent of superbugs that are resistant to all clinical antibiotics tested in our lab,” says Chatterjee. “Of course, simply increasing the concentration and/or light intensity kills more bacteria, and we have also demonstrated these effects.”

Chatterjee hopes the new technique has the potential to open doors for a number of different nanomedicines, and to intensify efforts towards novel therapeutics for superbugs. “Besides therapy, we have also shown that these redox species can easily be tailored to have no effect on light illumination, using similar size, charge and light absorption in another nanoparticle, or show photoproliferative effect in another nanoparticle,” says Chatterjee. “These photoproliferative particles can hopefully be used in bioreactors, biofuels and other biotechnological applications that can benefit from improved bacterial growth.”

The researchers are currently conducting pre-clinical trials with in-vivo studies in animal models. Chatterjee adds, “As a next step, we hope to be able to secure funding from federal agencies or private donors to pursue this therapy further, and conduct clinical studies and trials to tests the true efficacy and promise of novel light-activated therapy.”

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  1. C. Courtney et al. “Photoexcited quantum dots for killing multidrug-resistant bacteria,” Nature Materials (2016).
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