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Insights into Editorial: Superbug and Quantum Dot

Insights into Editorial: Superbug and Quantum Dot

25 January 2016

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Does nanotechnology hold the key to stopping antibiotic-resistant bacteria and the deadly infections they cause? Scientists in Colorado think it just might.


Scientists have developed light-activated nanoparticles — each roughly 20,000 times smaller than the thickness of a single human hair and have shown in lab tests that these “quantum dots” are more than 90% effective at wiping out antibiotic-resistant germs like Salmonella, E. coli and Staphylococcus.

What are Quantum dots?

A quantum dot is a nanoparticle made of any semiconductor material such as silicon, cadmium selenide, cadmium sulfide, or indium arsenide. They are essentially small crystals of nanometer-size dimensions – they’re about 20,000 times smaller than the width of a human hair. They are each one million times smaller than a millimeter. They have distinctive electrical conduction properties that are determined by the incredibly small size and structure.

  • When these QDs are hit with a specific frequency of radiation, their changeable structure, tailored by scientists, means that they can be finely tuned to emit a specific frequency of radiation; changing the wavelength of the light source can achieve the same effect.
  • In the dark, the QDs remain inactive. When bombarded by visible light, they become energetically “excited.”

Why we need them?

Super-bacteria resistant to the latest antibiotics, the last line of medical defence against various infections, cancer and HIV, is on the rise. These superbugs use evolutionary abilities to overwhelm medical advances. And to contain these bugs has been a challenging task for the scientists across the world.

What led to their rise?

The rampant, indiscriminate administration of common antibiotics has allowed these bacteria the ability to shuffle their genes and defeat these drugs. Such bacteria include Salmonella, Staphylococcus and E. coli.

Why is this cause for concern?

Antibiotic-resistant bacteria, also known as superbugs, infect about two million people and kill at least 23,000 people in the US each year.

  • There is no comparative data for India, but the country is the world’s largest consumer of antibiotics and has emerged as a leading hotbed of untreatable bacterial infections, their threat doubling over five years.
  • These bugs have also the ability to evolve, adapt and fight back.

What the latest discovery is all about?

Scientists have developed a light-activated superbug-killing nanoparticle. This nanoparticle is 20,000 times smaller than the width of a human hair.

  • These particles killed nine of 10 drug-resistant bacterial cells grown in a laboratory culture and resistant to all known antibiotics.
  • The quantum dots were used in tiny concentrations, about a thousand times smaller than current drugs in a pill.
  • Scientists have told that the development of these quantum-dot nanoparticles required much interdisciplinary research, stretching into biology, chemistry and electronics.

How Quantum dots fight Superbugs?

When placed among bacteria in a solution, something interesting happens. Bacteria rely on “redox” reactions, those involving the addition or removal of oxygen (reduction and oxidation, respectively). And when several Quantum dots are “excited” nearby, they produce chemicals that are able to be reduced or oxidized by reactive compounds within the bacteria. This effectively interferes with their intercellular processes, disrupts their cell growth, and kills them. In a lab-grown culture, this method has been shown to kill 92% of a variety of drug-resistant bacterial cells, while leaving other cells alone.

Significance of the quantum dots:

  • As the superbugs evolve, adapt and fight back, the quantum dots can be tuned, or customised, with an atom added or subtracted to create a new material, property or therapy, while using data from related clinical trials or drugs.
  • Gold and silver nanoparticles—among other materials—have previously been used to attack superbug infections, with varying degrees of success. Their main drawback is the damage to surrounding cells. However, the newly discovered particles show different effects on bacteria. For instance, cadmium telluride nanoparticles have a therapeutic effect against drug-resistant bacteria; similar-sized copper indium sulfide particles help good bacteria grow.
  • Varying the wavelength of light, or size, composition and surface of the dots, allows selective killing of drug-resistant bacteria, without harming host human cells.

Way ahead:

If successful in further clinical trials, particles can be administered to patients with infections and it can cure the infection without potential effects (or side-effects) for healthy host cells.

Scientists have envisaged three modes of quantum-dot therapy and drug administration

  • First, for topical infections caused by wounds or cuts, where a sticky adhesive patch coated with nanoparticles will need to be illuminated with light to begin treatment.
  • Second, for systemic infections, which will need the drug to be injected or administered intravenously.
  • Third, as a disinfectant—for instance, on hospital surfaces or instruments—in a well-lit or specially lighted room.


But more research, including clinical trials, will be needed to develop quantum dot therapy and prove its safety and effectiveness in humans. The stage is now set for the government to intervene and provide some fund for clinical trials. However, the final and most challenging proving grounds that take any therapy from laboratory to market—and determine if the quantum dot could be the next big thing.