A novel microfluidic chip-based fluorescent DNA biosensor, which utilized the electrophoretic driving mode and magnetic beads-based sandwich hybridization strategy, was developed for the sensitive and ultra-specific detection of single-base mismatch DNA in this study. In comparison with previous biosensors, the proposed DNA biosensor has much more robust resistibility to the complex matrix of real saliva and serum samples, shorter analysis time, and much higher discrimination ability for the detection of single-base mismatch. SNPs genotyping/detection in clinical diagnosis. By using the biosensor, we have successfully determined oral cancer-related DNA in saliva and serum samples without sample labeling and any preseparation or dilution with a detection limit of 5.6 x 10(-11) M, a RSD (n = 5) < 5% and a discrimination factor of 3.58-4.54 for one-base mismatch.