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Scientists design a quicker, biosensor-based method to detect fatal fungal infection

Small as they are, microbes have a considerable presence in our lives—some help us, a few don't bother about our existence, and some others can cause fatal infections and diseases. One such type of microbe that is favoured by India’s tropical weather conditions are fungi, which cause many diseases.  Invasive Aspergillosis, the world’s most invasive fungal infection, is caused by the fungus Aspergillus fumigatus. The fungus infects the lungs and severely affects immunocompromised patients. However, early diagnosis can save many lives.

In a new study, researchers from CSIR – Centre for Cellular and Molecular Biology (CCMB), Indian Institute of Technology Guwahati and MNR Dental College & Hospital, Hyderabad have developed an electrochemical nanobiosensor that can efficiently diagnose invasive aspergillosis. The study was published in the International Journal of Biological Macromolecules and was supported by grants from the Department of Science and Technology (DST), Science and Engineering Research Board (SERB), Government of India.

Currently, diagnosis of aspergillosis involves microbial cultures and tests that are invasive, painful, labour-intensive and time-consuming, and can take up to three days for diagnosis. The biosensor, developed by the scientists of the current study, addresses these problems. “Our developed biosensor provides onsite and rapid detections (less than 20 minutes), allowing early-stage detection”, says Dr Pranjal Chandra of Indian Institute of Technology Guwahati, who is the lead scientist along with Dr. Ira Bhatnagar from CSIR-CCMB, Hyderabad.

The researchers used gold nanoparticles, a polysaccharide called chitosan, a gold electrode and a chemical called 1,6-Hexanedithiol (HDT) to assemble the biosensor.  It works by detecting ‘gliP’—a gene found exclusively in the Aspergillus species. The gene encodes an enzyme essential for the production of gliotoxin—a fungal toxin that harms the immune system of the host and allows the growth of the fungus in the body. Thus, detection of gliP is an indication of the presence of the gliotoxin producing Aspergillus and helps determine the specialized antifungal treatment required against the disease.

The researchers tested the new biosensor under different parameters—different gliP concentration, temperature, reaction time and the concentration of the toluidine blue dye used for detection. They found that the sensor could detect the gliP gene in a solution of various other substances, thus demonstrating its high sensitivity and accuracy. Also, since the materials used to make the biosensor do not readily degrade, the sensor can be used multiple times and can remain stable for about seven weeks. These properties make the sensor very cost-effective and affordable.

According to Dr Chandra, the sensor has the potential to be a “miniaturised hand-held device for onsite gliP detection”, indicating that the sensor can be implanted into a small device that can be used on patients in hospitals. Such a device could make detection of infection quicker and easier than the current process that involves waiting for test reports from labs. The researchers also claim that the biosensor can also be applied to detect other genes and genetic biomarkers of other diseases. As a next step, the researchers are trying to create a prototype of the hand-held device. “We anticipate the optimised system will be ready for the prototype stage very soon”,  shares Dr Chandra.

The biosensor developed by the researchers is quicker and cost-effective as compared to the existing methods, allowing early detection and affordability to patients. The researchers hope that they can soon have a market-ready product. “The establishment of any product is an utterly complex process which requires the participation of both academia and industry for mass production”, says Dr Chandra. Even though it may take a while, the new biosensor could help save many lives as seven in every 1000 patients in intensive care units in India develop fungal infections.