(Keynote) Separation Detection of Cancer Cells and Metabolites Based on Disposable Electrodynamic Microfluidic Channel and Electrocatalytic Sensors
Authors: Shim Yoon-Bo 
Published: December 2024

Electrochemical approaches in bioengineering are attractive and practically expanded to related research areas. Of these, the electroanalytical methods are widely used for monitoring of a specific species in medical and biological samples. Hence, we have studied for the synthesis and characterization of catalytic electrode materials to selectively detect biological species, and an electrochemical separation method for multiple analytes in complex biological samples. Here, we present the biosensors and an electrodynamic microfluidic channel sensor for healthcare and medical purposes.
The biosensors for the detection of different lung cancer biomarkers, granzyme B (GzmB), interferon γ (IFN-γ) , and program-death ligand1 (PD-L1) were examined and compared their efficiency. The sensor probes were fabricated by covalently immobilizing corresponding aptamers or antibody on polyterthiophene bearing carboxyl (pTBA) or amino groups (pPATT) that were composited with electrocatalysts, as like pPATT/AuNP for GzmB, pTBA/MWCNT/AuNPs for IFN-γ , and rGO-pTBA for PDL1. To generate a signal for GzmB detection, a dual monomers-based bioconjugate (TBA/PATT) was prepared by self-assembling onto AuNPs followed by simultaneous attachment of both antibody and electron transfer mediator, revealing LOD of 62.95 fM. [1] Secondly, to detect IFN-γ, a bioconjugate was fabricated with antibody and ferrocene attached on bifunctionalized polymer (pTABA) self-assembled on AuNPs, resulting in LOD of 0.46 fM. Thirdly, the aptamer sensor was fabricated to capture a new electron mediator linked PD-L1 with LOD of 1.85 pM by impedometry and LOD of 0.20 pM by amperometry. The comparative study on immune checkpoint-related proteins concludes that PD-L1 is a more effective biomarker than granzyme B and interferon-gamma for lung cancer monitoring.
To separately detect multiple analytes in a complex sample, we developed a disposable screen-printed electrodynamic microfluidic channel (EDMC) device coupled with the sensors for circulating tumor cells and metabolites. We have also demonstrated different separation modes, which are the fluidic flow triggered by hydrodynamic force using an external pump, and by capillary action without a pump system. The EDMC with capillary force was initially used to analyze 12 metal ions (HMIs) [2]. The working electrode was modified with poly(diamino terthiophene) composited graphene oxide (pDATT/GO). The experimental variables were optimized according to the AC frequency and amplitude, sample flow rate, electrolytes, pH, temperature, and applied potential for detection. The detection limits of standard material were 0.04 (± 0.02), 0.29 (± 0.05), 0.07 (± 0.01), and 0.14 (± 0.06) ppb for copper, cadmium, mercury, and lead ions. The method reliability was evaluated with the parallel analysis using ICP–MS, where two results were coincident within 95% confidence level.
The separation detection of lactate and glucose in sweat was also performed using the EDMC based on time-resolved square wave voltammetry (trSWV). In this case, the applied potential was continuously scanned within a potential window around a redox peak until the multiple analytes are completely separated, then the time-dependent current variation converted to an elution chromatogram. To detect simultaneously glucose and lactate, the different Au alloys deposited electrochemically on the pTBA layer were examined for the catalytic activity to glucose and lactate oxidation. Of them, the AuCuCo/pTBA electrode shows the best sensing performance with the detection limit of 37.5 (± 4.8) µM and 6.12 (± 1.9) µM for lactate and glucose, respectively. The method reliability was evaluated through the analysis of real sweat and saliva samples from a healthy volunteer, and the result was consistent with that obtained with the high-performance liquid chromatography.
With an external syringe pump, cancer cells were separated and detected with the EDMC using both CA and trSWV. Here, the primary criterion for their separation using EDMC is electrodynamic force to differentiate cancer 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 with CTC surface and working electrode was modified with CNT/TBA/aptamer composite. In this case, the cancer cells captured by anticancer drug and corresponding aptamer were separated and detected employing both CA and trSWV at the channel end, which resulted in the coincident results between two methods. As a control experiment, i
n vitro cultured lung (A549), colon (Col205), and breast (MCF-7) cancer cells were also separated and detected, exhibiting separated peaks at the retention times of 328±52, 632±100, and 793±109 seconds.
References

H.A. Saputra, J. H. Chung, S. H. Yoon, K. D. Seo, D. S. Park, Y. B. Shim, Biosens. Bioelectron. 198, 113846 (2022).

M.M. Hossain, M. M. Karim, K. D. Seo, D. S. Park, Y. B. Shim, Anal. Chem. 95, 16701 (2023).