The detection of microorganisms in biological fluid or in food is a time-consuming process. Some of the common methods used to detect pathogens include bacterial or viral culturing, PCR techniques and ELISA, but culturing of pathogens is long been favored in many cases due to simplicity, cost-effectiveness and the fact that it results in a visible end-product. However, culturing method is extremely inefficient as it often takes multiple days or weeks for results to be produced. PCR and ELISA are less time consuming, but they still require hours if not days to complete. They are quite complex, requiring sample preparation, use of expensive enzymes, and access to top-of-the-line lab equipment. To address the shortcomings of these detection techniques and design a more approachable and practical diagnostic platform, researchers are designing more robust, timely and sensitive detection techniques such as nanotechnology based sensors.
Bacterial infection in biological fluids such as sputum and blood or food contamination can be detected by coating a strip with nanoparticles such as gold nanoparticles, magnetic nanoparticles and others. The gold nanoparticles will be electro statistically bound to a deactivated enzyme (that can be activated by the bacterial components). When bacteria is present in the sample, the interaction of the bacteria with the nanoparticle freed the enzyme will reactivate it. This reactivation will be coupled with an enzyme-amplified colorimetric reading that will allow for visual detection of contaminants. Not only bacteria, but also the level of enzymes and growth factors can be detected using this technology.
Aptamer-based sensors have been developed to detect a diverse set of targets includes adenosine triphosphate (ATP), cocaine, Hg2+, thrombin, vascular endothelial growth factor (VEGF) and IgE. The strip will be coated with gold nanoparticles and specific aptamers will be bound to these nanoparticles. The sensor design is based on electrochemical techniques where redox-active aptamers are immobilized on to a conducting support to probe the features of electronic transfer. The aptamer upon binding to its target, folds in to a well defined three-dimensional structure, either shielding or prompting the electron transfer between the redox-active units and the electrode substrate. If in a sample, a specific biological molecule is present it will bind to the aptamer which in turn bound to the nanoparticle. These interactions can be converted to an electric signal which can be detected by specially designed sensors. The future of this technology depends on the adaptation rate of these detection modalities to a test strip or chip-styled platform.
– Arpitha Shetty,