Simultaneous SERS-based immunoassay of dual cardiac markers on pump-free hybrid microfluidic chip

We developed a new pump-free hybrid microfluidic chip for the simultaneous SERS-based immunoassay of creatine kinase MB isoenzyme (CK-MB) and cardiac troponin (cTnI) cardiac markers. As a main composition, the patterned SERS paper substrate was firstly fabricated by UV light curing method using water-based polyurethane acrylate resin to have the hydrophobic barriers of microchannel, and then in-situ synthesized AuNPs on hydrophilic paper microchannel. It took advantage of 3D fibre structure to provide the capillarity force and compact AuNPs deposition scaffold for sample flow and highly sensitive SERS detection. The paper substrate was attached to PDMS microchannel and enabled the aqueous samples to flow in PDMS microchannel, which driven by capillary force of paper materials. The proposed method successfully detected the concentrations of two cardiac markers ranging from 0.01 to 50 ng mL−1. These results reveal the simultaneous detection capability of SERS-based immunoassay on the pump-free hybrid microfluidic chip without heavy external pump. The integration of paper and PDMS microfluidic chip is portable, low-cost, and tremendously useful for the simultaneous detection of cardiac markers.