(Keynote) Biosensor and Bioreactor Performance of a Chemically Modified Electrodynamic Microfluidic Channel
Authors: Shim Yoon-Bo , Seo Kyeong-Deok 
Published: December 2020

Numerous biological sensing devices have been developed for medical and health care purposes, to date. However, many cases demand a simple, inexpensive, and efficient device, concurrently performing the reaction, separation, and detection. Hence, we have established the separation detection method of molecules and nanoparticles using a symmetrical AC electric field applied electrochemical microfluidic device fabricated with a screen printing technique (EMC). The separation principle was also evaluated with the lateral movement of targets perpendicularly against the channel walls under the AC field, which was analyzed by simulation using the mathematically derived equation from Newtonian fluid mechanics.[1] The device can be used for various reactions and detections of complex biological species in the channel. Here, some applications will be introduced; 1) separation detection of cancer cells, 2) simultaneous analysis of glycated hemoglobin family, and 3) aptamer generation, separation, and biosensor fabrication.

The circulating tumor cells (CTCs) are dare rare, and account for as low as one cell per 109 hematologic cells in the blood of metastatic cancer patients, and they are very similar in size as compared to some of the WBCs, hence, their separation is a tremendous challenge. To date, CellSearch® is the only FDA approved method for sorting CTCs from blood samples, where only cells of epithelial origin can be separated. Thus, a new robust method is demanded to separate and analyze the CTCs for the early-stage diagnosis of cancers. Here, the primary criterion for their separation is electrodynamic force to differentiate cells in size (or mass) and surface charge. To additionally enhance the performance, the channel wall inside was modified with a positively charged lipid to interact the cell surface. The separated cells in the channel were detected amperometrically at the channel end. Here, the electrochemically inactive cancer cells have been selectively detected in blood using electrochemically active drugs. The device was able to separate a single cell with 92.0 ± 0.5 % efficiency. 37 patient blood samples from different origins were separated and detected with the detection rate of 91%.[2]

Glycated hemoglobin (HbA1c) is clinically important, since its concentration is directly or indirectly linked with various diseases including diabetes, nephropathy, retinopathy, atherosclerosis, and other perivascular diseases. Hence, the simultaneous detection of hemoglobin (Hb) and glycated hemoglobin fractions (HbA1c, HbAld1+2, HbAle, HbAld3a, HbAla+b, HbA2, and HbAld3b) is crucial. They were separated and detected using the EMC with a catalytic redox mediators-modified sensor. The different types of redox mediators were evaluated to achieve the efficient detection. Under optimized conditions, linear dynamic ranges for Hb and HbA1c among their fractions were obtained between 1.0×10−9 to 3.5 x 10-6 M and 3.0×10−9 to 0.6 x 10-6 M with the detection limit of 8.1×10−10 ± 3.0×10−11and 9.2×10−10 ± 5×10−11 M, respectively.

In addition, we have demonstrated the device for the aptamer generation and isolation, where the generated them were applied for a model protein, PvLDH for malaria diagnosis. Here, the target protein bound on the EMC channel walls induced the specific binding of DNA library molecules. In case of 60 min inducing, the partitioning efficiency between target protein and the library was attained to be 1.67 x 107 with the background of 5.56 × 10-6, which was confirmed by the qPCR. The in situ method has successfully generated and separated five aptamers in different sequences by one round generation. The dissociation constants (Kd) of selected aptamers were determined employing both electrochemical impedance spectroscopy (EIS) and fluorescence method. The sensing performances of five aptamers were evaluated for the PvLDH detection after individual immobilization on the screen-printed array electrodes. The most sensitive one revealed the detection limit of 7.8 ± 0.4 fM. The reliability of the sensor was demonstrated by comparing with the other malaria sensors.

Conclusively, the screen-printed electrochemical microfluidic channel with low potential AC electric field has been successfully demonstrated for the simultaneous detection of complex biological samples. It is respected to be applied in various research fields, such as bioreactor and biosensor, chemical reactor and sensor, medical device, separation science, etc.

References

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N.G. Gurudatt, S.Chung, J.M. Kim, M.H. Kim, D.K.Jung, J.Y. Han, Y.B. Shim, Biosensors and Bioelectronics 146 (2019) 111746.

M.M. Hossain, J.M. Moon, N.G. Gurudatt, D.S. Park, C. S. Choi, Y.B. Shim, Biosensors and Bioelectronics 142 (2019) 111515.