(381f) An Integrated Diagnostic Platform for Biomolecule Detection

Current techniques for detection of biomolecules including DNA, RNA and lipids are expensive and require trained personnel/extensive sample prep/bulky instrumentation, making it impractical for field applications. The development of low-cost, turn-key and portable detection platforms for  identification of biomolecules has attracted great attention to a wide variety of applications in food, water and medical safety. We report an integrated, low-cost, sample-to-answer, and selective biosensing platform for the detection of biomarkers. The integrated microfluidic biochip consists of a sample pretreatment unit to isolate biomolecules from cells/bacteria/virus in raw samples and a nanomembrane-based molecular sensing/pre-concentration unit to perform the biosensing. The sample pretreatment unit is fabricated based on gel electrophoresis where an agar gel is used to separate negatively-charged biomolecules from a target sample by applying a DC field. Downstream from the pretreatment unit, an ion-selective nanomembrane-based preconcentration unit is used to concentrate the isolated molecules at a specific position where the biosensing unit is placed. The concentration of biomolecules (up to 200X) is due to the depletion phenomenon developed at the cation-exchanged membrane interface and application of pressure driven flow in the opposite direction of the depletion front. The anion-exchange nanomembrane-based biosensing is based on a charge inversion phenomenon that occurs when charged RNA or other biomolecules hybridize with specific probes attached to the nanomembrane. We have shown extraction and detection of several pathogenic nucleic acids including: microRNA associated with oral cancer, brucellosis, E.coli and dengue virus. In addition to nucleic acid detection, we have also demonstrated the ability of the sensor to detect Lipopolysachharide molecules like endotoxin  by functionalizing the nanomembrane surface with an antibiotic polymyxin molecule that acts as the probe. We have demonstrated high selectivity (2 base mismatch), large dynamic range (3 decades) and low detection limit (1 fM). The versatility of the platform allows detection of other target biomolecules provided a probe of interest is available and specific.