A zepto mole DNA micro sensor

Using molecular beacons (MB) as highly sensitive and selective nucleic acid probes, we eliminate two of the major but cumbersome steps, probe immobilization and washing, of gene-based biosensors. By integrating sidewall mirrors with microchannels, we can increase the signal-to-noise ratio of the optical detection. The detection specificity is achieved using a MB based DNA hybridization technique. Molecular beacons become fluorescent only upon hybridization with target DNA/RNA molecules as the quencher is separated from the fluorophore. We can hence eliminate washing and immobilization steps and establish the inchannel detection technique. This technique reduces the detection volume to 36 pL. Microchannels coated with metal films with high reflectance are used to increase the signal level in the Laser Induced Fluorescence (LIF) system. By using the side-mirror channel with inchannel sensing technique, the detection limit is 0.07 zmol which is at least 3 orders of magnitude lower than many other DNA detection schemes.