Research On The Development Of A Microbial Tnree-electrode Cell Dased Microfluidic Chip For Biosensing

Bioelectrochemical system based sensors have the disadvantages of long response time and being easily affected. This work combined microbial three-electrode cell (M3C) and microfluidic chip to develop a M3C based microfluidic chip for sensing to shorten the response time and improve the stability as well as reproducibility of output signal.Firstly, a M3C based microfluidic chip with a volume of 3 μL was developed. This chip successfully integrated microfluidic channel and M3C by exploiting laminar flow to separate the reference electrode from the working electrode. In the open circuit potential (OCP) test, the Ag/AgCl reference electrode potential stabilized at 0.275 V. Meantime, calibration of the reference electrode by [Fe(CN)6]3-/ [Fe(CN)6]4-showed similar result with OCP test.Then two model electrochemically active bacteria, Geobacter sulfurreducens and Shewanella oneidensis MR-lwere chosen to investigate the growth in this M3C based microfluidic chip. The results showed that S. oneidensis MR-1 couldn’t grow with gold electrode, thus G. sulfurreducens was chosen as the sensing element in this chip. According to electron transfer mechanism between G. sulfurreducens and gold electrode and the lifetime of Ag/AgCl reference electrode under different potentials, an optimum potential was determined. At the optimum potential, the chip was inoculated with G. sulfurreducens, the results showed the OCP change between unused and used Ag/AgCl reference electrode (30 days) was just 0.7%. These demonstrated this chip successfully integrated microfluidic channel and M3C with good stability during operation.After inoculating the microfluidic chip with G. sulfurreducens and operating under the optimum condition, a milliliter scale M3C was used as the control to investigate the current density, onset potential and midpoint potential. The results demonstrated that this M3C based microfluidic chip had similar performance with the control and other reported M3Cs. These demonstrated this chip exhibited similar function with milliliter scale M3C in microfluidic channel.Finally, this M3C based microfluidic chip was applied to bio-toxicant sensing. Electron acceptors and electron mediators were chosen to preliminary evaluation the sensing performance of this chip. The results showed that the response time was shorter than 10 minutes and the output signal had good stability. Later the toxicant response was studied in this chip. The result showed that 0.3-7 ppm Cu2+and 0.01-0.1% formaldehyde had inhibiting effect on G. sulfurreducens. Antibiotic (cefradine and erythrocin) didn’t have inhibiting effect on G. sulfurreducens. Furthermore, a liner relationship between input and output signals was obtained in certain scope.The M3C based microfluidic chip developed in this work will provide researchers in related areas a versatile platform for biosensor and EAB study.