Impedance transduction for monitoring particle-based diagnostic reactions

IRUPE BRESSAN; EZEQUIEL STARECINCH; JUAN CERRUDO; ALBANO PEÑALVA; LEANDRO PERETTI; LUCIANO MARTINEZ RAU; PABLO SCHIERLOH; ESTEBAN ROSSI; MARTIN ZALAZAR; MATIAS MACHTEY

Buenos Aires

Congreso; III Brazil-Argentine Microfluidics Congress VI Congreso de Microfluídica Argentina; 2022

In the Latex Immunoagglutination Assay (LIA), an antigen-coated latexmicrospheres colloid agglutinates in the presence of specific antibodies. Themethod is a robust, rapid and inexpensive diagnostic tool for searching specificantibodies/antigen in screening studies. Detection can be done either visually(with the naked eye) or by instrumental methods. The first is the most adoptedway for its simplicity and portability. However, the results are subjective tothe analyst and inadequate for the quantification of the phenomenon. On theother hand, instrumental techniques allow objectivity, sensitivity and precision,although they involve laboratory equipment and expert analysts. In the presentwork, we design and manufacture an electrochemical transducer to evaluate theimpedance response of a commercial LIA kit placed on interdigitated coplanarelectrodes. These were built in PCB (FR4-Copper) and Nickel-Gold electroplated (Fig. 1). An alternating voltage of 10 mV within a 1 kHz to 5 MHzfrequency range was applied to the electrodes and the impedance was measuredby an adapted Analog Discovery 2 (Digilent) equipment. In addition, we studied the time-impedance evolution (module and phase) of positive and negativereactions on two different interdigitated designs. Reagent microdroplets weredeposited on the interdigitated electrodes in a final volume of 67 µl, and distributed over the detection area using a glass coverslip that was manually placedon top. The impedance readout method promises the development of a portableinstrumental -Point of Care- that brings objectivity, more sensitivity, reagentvolume reduction and automatic detection.