Lab-on-a-Chip Biosensors for the Rapid Detection of Pathogens in Clinical and Field Samples

Abstract

In the United States and other developed countries, despite great efforts in time and funding for the prevention of foodborne and airborne diseases, there is still an unacceptable level of common pathogens spread via food, water, and air. To this end, lab-on-a-chip (LOC) technologies were developed for field-deployable assays and point of care diagnostics. These devices have potential applications in hospitals, agricultural farms, processing plants, and even on fields of battle. Two successful types of assays in the recent years towards point of care diagnostics are immunoassays and nucleic acid detection assays. In the Appendix A, we demonstrated a complete, field-deployable particle immunoassay encased within a microfluidic chip that detects small quantities of Salmonella Typhimurium in poultry fluid samples. Because the necessary reagents are pre-loaded and the test and negative control channels are fed by a single sample inlet, single pipetting of sample is possible. This assay demonstrated a 10 CFU/mL limit of detection, which is considerably lower than PCR and enzyme-linked immunosorbent assay (ELISA). Total assay time, including sample reading in an integrated handheld device, was 10 minutes, which was much lower than conventional methods. Because of the simplified protocol and assay time, this biosensor has potential in clinical and field diagnostic applications. In Appendix B, we fit the particle immunoassay to test for Influenza A H1N1/2009 virus and included aerosol sampling from a scaled-down mock classroom. To make the assay field deployable, we used an iPhone for signal detection. The detection limit of the assay was 1 pg/mL (10 pg/mL using the iPhone), which is well below the limit of detection for RT-PCR. This protocol demonstrated that immunoassays can be effective in the presence of interfering dust particles and that viruses can be collected from aerosol with minimal sample preparation. In Appendix C, we demonstrated that paper microfluidics, a newer vision of microfluidics, is a cheap and easy method to extract nucleic acid from S. Typhimurium in a variety of samples, including poultry packaging liquid, whole blood, and feces. Fluorescent detection with an iPhone allows for field and clinical testing. This protocol interfaces with rapid PCR and is a true diagnostic tool.