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January 19, 2016

Combating Antibiotic Resistance Goes Quantum

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    New light activated quantum dot technology could be used to treat multi-drug resistant bacteria, such as Salmonella pictured above. [NIAID]

    To find solutions to tough, persistent problems it is common to use phrases like “think big” or “outside the box.” However in the fight against multidrug resistant superbugs, researchers are beginning to think small—very small.

    Now, scientists at the University of Colorado, Boulder have developed an adaptive light-activated nanotherapy that they believe will help stem the tide in the ever-escalating evolutionary battle with drug-resistant bacteria.

    Resistant superbugs such as Salmonella, E. coli, and Staphylococcus infect close to 2 million people and kill at least 23,000  in the United States each year. Due to the highly adaptive nature of these microbes, they can rapidly develop immunity to many antibiotic compounds—placing our entire defensive front in jeopardy.

    Yet, in the current study, CU-Boulder investigators describe their research into new light-activated therapeutic nanoparticles known as quantum dots. The dots, which are about 20,000 times smaller than a human hair and resemble the tiny semiconductors used in consumer electronics, successfully killed 92% of drug-resistant bacterial cells in lab-grown cultures.      

    "By shrinking these semiconductors down to the nanoscale, we're able to create highly specific interactions within the cellular environment that only target the infection," explained co-senior study author Prashant Nagpal, Ph.D., assistant professor in the department of chemical and biological engineering at CU-Boulder.

    The findings from this study were published recently in Nature Materials through an article entitled “Photoexcited quantum dots for killing multidrug-resistant bacteria.”

    Previous studies proved that nanoparticles made of gold or silver were effective at combating antibiotic-resistant infections but indiscriminately damaged the surrounding cells as well. However, quantum dots could be tailored to particular diseases thanks to their light-activated properties. The dots are inactive in darkness, but can be activated by exposing them to light, allowing researchers to modify the wavelength in order to alter and kill the infected cells. 

    "While we can always count on these superbugs to adapt and fight the therapy, we can quickly tailor these quantum dots to come up with a new therapy and, therefore, fight back faster in this evolutionary race," noted Dr. Nagpal.

    The CU Boulder researchers found that in vitro the quantum dots were highly effective at killing bacterial strains.

    “We observed that photoexcited quantum dots can kill a wide range of multidrug-resistant bacterial clinical isolates, including methicillin-resistant Staphylococcus aureus, carbapenem-resistant Escherichia coli, and extended-spectrum β-lactamase-producing Klebsiella pneumoniae and Salmonella typhimurium,” the authors wrote. “We also show that the quantum dots can be tailored to kill 92% of bacterial cells in a monoculture, and in a co-culture of E. coli and HEK 293T cells, while leaving the mammalian cells intact, or to increase bacterial proliferation.”

    The researchers are hopeful that the specificity and effectiveness of this innovation may help reduce or eliminate the potential side effects of other treatment methods, as well as provide a path forward for future development and clinical trials.

    "Antibiotics are not just a baseline treatment for bacterial infections, but HIV and cancer as well," remarked co-senior study author Anushree Chatterjee, Ph.D., assistant professor in the department of chemical and biological engineering at CU-Boulder. "Failure to develop effective treatments for drug-resistant strains is not an option, and that's what this technology moves closer to solving."

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