Prostate cancer is the most common cause of cancer-related death in men in the US and throughout the world.  Current practices for detection and staging of prostate cancer often fall short in terms of sensitivity, specificity and inability to distinguish between aggressive and indolent forms of prostate cancer.  These limitations lead to unnecessary treatments that adversely affect the patients’ quality of life with minimal or no gain.  Measurement of small panels of molecular signature biomarkers in serum holds tremendous potential for cancer diagnostics and personalized therapy. Here we describe a simple, low-cost, modular microfluidic system for on-line capture and detection of prostate cancer protein biomarkers. The protein panel includes PSA, CD-14, ERG, GOLM-1, PEDF-1, IGF-1, VEGF-D and IGFBP-3, many of which are thought to be specific for aggressive prostate cancer. 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. Gold immunoarrays fabricated by ink-jet printing ($0.2) or commercial screen printed carbon arrays ($5) 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 the cancer biomarker proteins from as little as 5 uL. Measurements of this panel of selected biomarkers will be tested with prostate cancer patient samples in future to assess its diagnostic capability.