Microchip Sensor Based On Reflectometric Interferencespectroscopy And Its Application In Bacterial Assay

At present, the diseases caused by microbial gradually become the common concern of health and environmental issues. In addition, the abuse of antibiotics leads to the emergence and spread of worldwide antibiotics resistance, and also increases the risk of bacterial infection patients. Therefore, the method for detection of rapid microbial and fast screening methods of antibiotics are urgently needed.(1) This study reported the fabrication of microfluidic pH sensor which was obtained by integration of pH sensitive hydrogel coated porous silicon with PDMS microfluidic channels. By utilizing the reflectometric interference spectroscopic measurements, real-time observing of the pH change in the micro-channel can be realized, in which the effective optical thickness (EOT) was selected as the optical signal for indicating the reversible swelling process of chitosan hydrogel stimulated by pH change. With this microfluidic pH sensor, we demonstrate that due to the outstanding diffusion and mass transfer rate in microfluidic channels, pH hydrogel displays faster and more sensitive response compared to macro-system. In addition, confinement of bacterial cells in nanoliter size channel allows rapid accumulation of metabolic products and eliminating the need for long time pre-incubation, thus reducing the whole detection time. Based on this technology, the whole bacterial growth curve can be obtained in less than2h, and consequently rapid AST can be realized. Compared with conventional methods, the AST data acquired from the bacterial growth curve can provide more detail information for studying the antimicrobial behavior of antibiotics during different stage. Furthermore, the new technology also provides a convenient method for rapid MIC determination of individual antibiotic or the combinations of antibiotics against human pathogen that will find application in clinical and point of-care medicine.(2) Method for label-free detection of bacteria on a micro-sensor chip was established. The microchip was composed by porous silicon and PDMS. This sensor chip was pre-modified by antibody which can specifically capture Escherichia coli(E.coli). Since the captured E.coli is much larger than the pore size of the porous silicon, it can effectively block the entrance of the optical probe (bovine serum albumin, BSA) into the porous silicon layer. The blockage effect was monitored by reflectometric interference spectroscopy. It was found that the optical signal AEOT decreased with the increase of bacterial concentration. This method shows rapid E.coli detection, and the detection range for103-107CFU/ml. The detection time is only20-30minutes. At the same time, the high selectivity of this sensor chip is demonstrated by compared with the pseudomonas fluorescens (P17) and spirillum (NOX) samples.