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The sustained overuse of antibiotics has caused the development of antibiotic-resistant pathogens, or the so-called “superbugs,” which can lead to acute, dangerous infections that should be diagnosed and treated at an early stage.
But antibiotic sensitivity assays employed to identify this resistance depend on cell culture that can take many days to complete. Scientists have now addressed this drawback by developing an innovative self-driven DNA nanosensor with the ability to quickly detect methicillin-resistant Staphylococcus aureus, a deadly superbug, with high specificity and sensitivity.
The field of medicine has been completely transformed by antibiotics with their ability to treat more common microbial diseases at present. But the unchecked use of antibiotics has resulted in the key issue of antibiotic resistance across the world.
With people continuously exploiting antibiotics, occasionally at doses much higher than what is required, disease-causing bacteria are quickly developing defense plans to circumvent them. Such drug-resistant bacteria, also called “superbugs,” cause severe infections that are hard to treat and can ultimately be lethal.
A specifically lethal group of superbugs called Methicillin-resistant Staphylococcus aureus (MRSA) has developed resistance to the antibiotic methicillin and is a significant cause of hospital-acquired infections. Early and precise diagnosis is vital for effective treatment.
But antibiotic sensitivity tests, which are the gold standard for evaluating bacterial response to several drugs, are extremely lengthy processes and can take up to a few days to yield outcomes. Alternative methods that use biosensors and enzymes have exhibited some potential, but they rely on external driving forces (such as magnetic or electrical energy), which increases the element of uncertainty.
Scientists from Japan and Taiwan who were looking for a simpler and more dependable detection tool have currently designed a highly sensitive culture-free and self-driving DNA nanosensor that can precisely detect lethal superbugs such as MRSA.
The nanosensor is based mainly on Brownian motion, a term describing the self-driven random and irregular movement of microparticles. Dr Hiroaki Sakamoto, co-author of the study and an Associate Professor at the University of Fukui, Japan, was thrilled by the results published in the journal Biosensors and Bioelectronics.
Three steps are involved in the making of such sensors. Initially, the team made brief sequences of DNA, known as oligonucleotide probes, which could identify two different target sequences in the DNA of MRSA.
Among the probes, one was fixed with fluorescent bead to be utilized for precise visual quantification of particle movement. They attached heavy gold nanoparticles to the other probe to reduce the diffusivity or the nanobead’s rate of movement.
When the probes were integrated with MRSA DNA, the scientists noticed that both were “sandwiched” between the DNA, which made their detection simple and quick. Moreover, the team verified the sensor’s specificity from its incompetence to attach to other DNA from other bacteria like Escherichia coli.
The innovative biosensor design developed by the researchers not only avoids the need for laborious and time-consuming cell culture but also makes the sensor configuration simple without the need for any complicated fabrication, external energy sources, and resources.
Furthermore, the nanosensor considerably reduces the detection time to just 10 seconds. In addition, it has a low limit of detection and could detect minuscule concentrations of up to 10 pM, thereby enabling precise and rapid diagnosis of contagious pathogens from very limited samples. Moreover, it can be tailored for the detection of other pathogens besides MRSA by altering the target DNA binding sequence.
In order to coexist with the threat of infectious pathogens, rapid and simple testing detection technology that can enable timely diagnosis and treatment is essential. Even if a new pathogen emerges, the social disruption that may occur due to the outbreak can be minimized as much as possible in future using DNA detection sensors.
Hiroaki Sakamoto, Study Co-Author and Associate Professor, University of Fukui
Sakamoto thus explained the significant long-term applications of their study. In fact, the innovative DNA sensor is an economical and quick detection device that can reinforce the fight against antibiotic resistance.
Wang, J.-C., et al. (2020) Culture-free detection of methicillin-resistant Staphylococcus aureus by using self-driving diffusometric DNA nanosensors. Biosensors and Bioelectronics. doi.org/10.1016/j.bios.2019.111817.