Label-free impedance detection of cancer cells from whole blood on an integrated centrifugal microfluidic platform

Abstract

An electrochemical Lab-on-a-Disc (eLoaD) platform for the automated quantification of ovarian cancer cells (SKOV3) from whole blood is reported. This centrifugal microfluidic system combines complex sample handling, i.e., blood separation and cancer cell extraction from plasma, with specific capture and sensitive detection using label-free electrochemical impedance. Flow control is facilitated using rotationally actuated valving strategies including siphoning, capillary and centrifugo-pneumatic dissolvable-film (DF) valves. For the detection systems, the thiol-containing amino acid, l-Cysteine, was self-assembled onto smooth gold electrodes and functionalized with anti-EpCAM. By adjusting the concentration of buffer electrolyte, the thickness of the electrical double layer was extended so the interfacial electric field interacts with the bound cells. Significant impedance changes were recorded at 117.2Hz and 46.5Hz upon cell capture. Applying AC amplitude of 50mV at 117.2Hz and open circuit potential, a minimum of 214capturedcells/mm2 and 87% capture efficiency could be recorded. The eLoaD platform can perform five different assays in parallel with linear dynamic range between 16,400 and (2.6±0.0003)×106cancercells/mL of blood, i.e. covering nearly three orders of magnitude. Using the electrode area of 15.3mm2 and an SKOV3 cell radius of 5µm, the lower detection limit is equivalent to a fractional surface coverage of approximately 2%, thus making eLoaD a highly sensitive and efficient prognostic tool that can be developed for clinical settings where ease of handling and minimal sample preparation are paramount.