Low-cost Electrochemical Microfluidic Immunoarrays for Cancer Diagnostics

Rapid, accurate and sensitive detection of multiple biomarker proteins holds significant promise for early diagnosis of cancer and personalized therapy guidance. Here we describe a simple, low-cost, modular microfluidic system for on-line capture and detection of cancer protein biomarkers. The system features a small chamber for on-line protein capture from serum by magnetic beads labeled with many copies of analyte-specific antibodies and signal-transducing enzyme labels, positioned upstream of a detection chamber housing a nanostructured 8-electrode sensor array. Microfluidic chambers are made by templating polydimethylsiloxane (PDMS) channels on machined aluminum molds and mounting on hard flat poly(methyl methacrylate) (PMMA) plates equipped with inlet and outlet panels. The chambers are interfaced with a sample injector, syringe pump and switching valves to deliver sample and reagents. Gold immunoarrays fabricated by ink-jet printing ($0.2) or commercial screen printed carbon arrays ($6) are fitted into the microfluidic detection chamber to achieve high sensitivity. Ultralow detection limit in the low fM range was achieved for multiplexed detection of four oral cancer biomarker proteins from as little as 5 uL sample within 30 minutes. The incorporation of electrochemical immunoassays for protein biomarkers in a microfluidic platform thus provides a rapid, sensitive and effective tool for cancer diagnostics.