Multianalyte Biosensor with Chips for Human and Environmental Monitoring

The closed environments of space travel offer enhanced opportunities for transmission of pathogens and toxins. Ideally, food, water, air, and people need to be monitored in order to assure the continued health of the traveler. Rapid diagnostic systems are required, in particular, in cases of human illness to identify both the infection and the source. We propose to build a handheld, low-power biosensor capable of analyzing samples from virtually any aqueous medium for a customized array of targets. The sample will be exposed to a sensing chip with an array of specific (antibody) and semi-selective binding molecules capable of recognizing multiple targets. The sample is followed by a fluorescent reagent capable of binding to any captured target. The identity of the target is determined by the location of the fluorescence on the chip. In the first year, the biosensor itself will be miniaturized, while the second year will focus on the design of chips that can be mass produced and include both a waveguide coated with the capture array and the reservoir of fluorescent reagent. In the third year, chips will be adapted specifically for monitoring: (1) food and water, (2) air and surface samples collected using a small cyclone or swipe, respectively, and (3) human fluids such as nasal swabs and blood. Targets will include bacteria, viruses, toxins and metabolic indicators.
The first two years of this project focus primarily on device development issues related to miniaturization. To this end, we have concentrated to date on 3 issues: improving the microfluidics cube, developing a better way of attaching the flow channels to the waveguide, and screening alternative imaging systems which would be smaller and less expensive than the peltier-cooled CCD. The plastic microfluidic cube was reconfigured to provide separate delivery channels for liquids from the 6 sample reservoirs and 6 reagent reservoirs to the sensing surface. These separate delivery ports eliminated premixing of the samples and fluorescent reagents. The attachment of the plastic flow channels to the glass waveguide has been an ongoing problem as most adhesives generally leak after long-term exposure to water. We are building a specially configured flow channel component with PDMS laminated on the polycarbonate walls between the flow channels for better seals to the glass waveguide. Finally, we have screened a CMOS camera and a photodiode array for S/N in the array biosensor. Neither is capable of providing the stable background and consequent S/N that is achieved using the peltier-cooled CCD.
A handheld, fully automated biosensor that is relatively immune from interferents in complex samples can be used to diagnose human diseases in clinical samples, detect pollutants in groundwater, test for pathogens and toxins in food, and monitor industrial processes. Assays for the detection of biological warfare agents have already been demonstrated using the laboratory prototype.