Fabrication of microfluidic reactors and mixing studies for luciferase detection

We report the detection of luciferase by implementing a bioluminescent assay in microfluidic reactors. The reactors were fabricated in poly(methyl methacrylate) by hot embossing using a mold master with the reactor layouts made by high-precision micromilling. The overall fabrication process was simple to implement and had a quick turnaround time with low cost. Two reactors, one with smooth channels (called reactor I) and the other with staggered herringbone mixers (called reactor II), were studied for the bioluminescent assay. The assay was implemented by introducing a sample and an assay solution into the reactors and then mixing took place to achieve the enzymatic reactions. We found that the mixing efficiency in reactor II was 17.8 times higher than reactor I. Theoretical analysis of the experimental results indicated that the required channel length of mixing was linearly proportional to the flow rate. A calibration curve for luciferase was obtained for both reactors. We found that the detection sensitivity of reactor II was 3 times higher than reactor I. The limit of detection in reactor II was determined to be 0.14 microg/mL luciferase. The device was further exploited to determine the concentration of luciferase samples obtained from in vitro protein expression.