Here, we report the developed cyclo olefin polymer (COP) microfluidic chip on a fabricated rotating heater stage that utilizes centrifugation-assisted thermal cycle in a ring-structured microchannel for polymerase chain reaction (PCR). The PCR solution could be driven by thermal convection and continuously exchanged high/low temperatures in a ring structured microchannel without the use of typical syringe pump. More importantly, the flow rate was controlled by the relative gravitational acceleration only. The platform enables amplification within 10 min at 5G and has a detection limit of 70.5 pg/channel DNA concentration (β-actin, 295 bp). The current rotating system is capable of testing four different samples in parallel. The microfluidic chip can be preloaded with the PCR premix solution for on-site utility, and, with all of the features integrated to the system, the test can be conducted without the need for specialized laboratory and trained laboratory staff. In addition, this innovative chemical reaction technique has the potential to be utilized in other micromixing applications.

In this study, we report label-free detection of alpha-fetoprotein (AFP), which has been used as a biomarker for hepatocellular carcinoma, by a microfluidic reflectometric interference spectroscopy (RIfS) system adopting a simple halogen light source and an inexpensive silicon-based sensor chip. Introduction of carboxy groups on a silicon nitride sensor chip to immobilize anti-AFP monoclonal antibody (anti-AFP) was carried out simply by immersion in aqueous solution containing triethoxysilylpropylmaleamic acid bearing a carboxy group and a silanol group. The RIfS system with the anti-AFP-immobilized sensor chip was found to give a reversible response through 100 on/off cycles using a regeneration buffer with high reproducibility (coefficient of variation (CV) = 5.7%). The limit of detection (LOD) of AFP was 100 ng mL(-1), and the measurement range spanned 3 orders of magnitude. Furthermore, the sensor chip showed no cross-reactivity with human serum albumin, Immunoglobulin G, transferrin, or fibrinogen at 100 μg mL(-1) without the use of blocking reagents such as bovine serum albumin. Consequently, the proposed RIfS system is a potentially effective tool for biomarker detection and in vitro diagnostics.