Development of a Protein Enrichment and Detection Microfluidic Platform Based on Ion Concentration Polarization (ICP) and Electrochemical Impedance Spectroscopy (EIS) Techniques

In this letter, a protein enrichment microfluidic platform with an integrated bioelectrochemical sensing system has been proposed and demonstrated for the first time, enabling protein preconcentration and detection. The proposed chip was composed of an electrochemical biosensor integrated into a preconcentrator with a dual-gate structure. The bioelectrochemical sensor had three electrodes, including working, counter, and reference electrodes. The working and counter electrodes were made of gold, while the reference electrode was made of Ag/AgCl. The preconcentrator was designed with three microchannels, with a main channel electrically connected to two subchannels through Nafion ion-selective membranes. The chip was fabricated using photolithography and soft lithography techniques. Ag and AgCl layers were deposited on the gold electrode to form the reference electrode. The Nafion membrane was created using the microflow patterning technique. Then, the gold electrode surface was modified to attach anti-albumin antibodies (anti-bovine serum albumin-anti-BSA) and form the biosensor. Bovine serum albumin-fluorescein isothiocyanate conjugate was specifically bound to anti-BSA through the protein preconcentration process at the biosensor area. The experimental results show that bovine serum albumin (BSA) proteins were concentrated successfully after applying potentials to the ends of the microchannels. The protein concentration increased 25 times after 80 s. The change in the electrochemical impedance spectroscopy (EIS) signal demonstrates the specific binding between BSA and anti-BSA on the electrode surface. In addition, the results also show the significant effectiveness of the protein preconcentration process for improving the binding ability and electrical signal amplification of the bioelectrochemical sensor. With the obtained results, a lab-on-a-chip system can be developed to quantify protein concentration and diagnose some cancer diseases.