Microfluidic Systems for Biomarker Analysis and Cancer Diagnosis
We first report on a magnetic surface coverage assay, in which ‘large’ (2.8 μm) magnetic beads have contact with ‘small’ (1.0 μm) immobilized magnetic beads via magnetic dipolar interaction to induce specific immunocomplex formation. This attractive magnetic force is carefully balanced with a viscous drag imposed by a microfluidic flow to remove non-specifically bound large magnetic beads. In this way, a fg mL-1 limit of detection was demonstrated for Tumor Necrosis Factor-alpha (TNF-alpha) in serum, by counting of the number of surface-bound large beads. Subsequently, we report a microfluidic tissue processor that permits accurate quantification of the expression of biomarkers on tissue sections, as enabled by the ultra-rapid and uniform fluidic exchange of the device. An important clinical biomarker for invasive breast cancer is the human epidermal growth factor receptor 2 (HER2). Using our device, we performed tests on invasive breast carcinoma cases expressing various levels of HER2 and demonstrated the clinical potential of microfluidics for accurate biomarker expression analysis.