Nucleic acid sensor and fluid handling for detection of bacterial pathogens

An embedded controller with a keypad user interface was used to operate a nucleic acid sensor with fluid handling and real-time PCR capabilities. The sensor system consisted of pumps and valves for fluid transfer, a fluorometer composed of a light emitting diode, photodiode, and signal conditioning circuitry, a thermoelectric module for heating and cooling the reaction chamber, and power switching circuitry. The amplification and dissociation results of the SYBR Green real-time PCR test were downloaded to a PC for evaluation.Extracted Salmonella DNA in autoclaved water was automatically mixed with real-time PCR reagents and loaded into a glass reaction chamber. Alternating positive and negative control reactions were run, and the Salmonella sample carrying line was automatically cleaned with a combination of reagents following each reaction. Evaluation of amplification, dissociation, and agarose gel electrophoresis data indicated that DNA carry-over contamination and inhibition of PCR by the cleaning reagents were not significant problems, and therefore it was possible to reuse the same sample carrying line between runs.