Enzyme-Free Plasmonic Biosensor for Direct Detection of Neurotransmitter Dopamine from Whole Blood.

Complex biological fluids without pretreatment, separation, or purification impose stringent limitations on the practical deployment of label-free plasmonic biosensors for advanced assays needed in point of care applications. In this work, we present an enzyme-free plasmonic neurotransmitter dopamine biosensor integrated with a microfluidic plasma separator. This integrated device allows the in-line separation of plasma directly from the bloodstream and channels it to the active detection area, where inorganic cerium oxide nanoparticles function as local selective dopamine binding sites through strong surface redox reaction. A thorough understanding and engineering of the nanoparticles is carried out to maximize its dopamine sensitivity and selectivity. We obtain detection of dopamine at 100 fM concentration in simulated body fluid and 1 nM directly from blood without any prior sample preparation. The detection selectivity is found to be at least five-times higher compared to the common interfering species. This demonstration shows the feasibility of the practical implementation of the proposed plasmonic system in detection of variety of biomarkers directly from the complex biological fluids.

A whole blood sample-to-answer polymer lab-on-a-chip with superhydrophilic surface toward point-of-care technology.

An innovative sample-to-answer (S-to-A) polymer lab-on-a-chip (LOC) with a blood plasma separator based on asymmetric capillary force has been proposed, developed, and completely characterized for point-of-care technology (POCT) applications. A spray layer-by-layer (LbL) nanoassembly coating has been applied for the superhydrophilic surface onto the cyclic olefin copolymer (COC). Then, the developed superwetting surfaces were designed and optimized for three device applications such as lateral transportation of whole blood in the device by capillary pumping, on-chip whole blood/plasma separation with an asymmetric capillary force, and detection using a capillary-driven lateral flow colorimetric assay. Integrating three primary components of the devices, the S-to-A polymer LOC platform has been effectively confirmed for the lateral flow colorimetric assay of bovine serum albumin (BSA) from unprocessed human whole blood without an external power resource.