Potential-Controlled Adsorption, Separation, and Detection of Redox Species in Nanofluidic Devices

Laser transparent multiplexed SERS microneedles for in situ and real-time detection of inflammation

It is a significant challenge to perform painless invasive detection of inflammation progression in relation to the evolution of pH, redox potential, and reactive oxygen species (ROS) levels in an in situ and real-time manner. In this work, polydopamine-modified, silver nanoparticle-decorated poly (methyl methacrylate) microneedles (AgNPs@PDA@MNs) have been developed as a multiplexed surface enhanced Raman scattering (SERS) diagnostic platform. Using rhodamine 6G as the Raman signal molecule, the AgNPs@PDA@MNs demonstrated a significant enhancement with reasonable linearity in the range of 10^-3-10^-9 mol/L and the limit of detection is 1.0 × 10^-10 mol/L 4-mercaptobenzoic acid, anthraquinone-2-carboxylic acid and para-aminothiophenol were covalently anchored on AgNPs@PDA@MNs SERS substrate. I₁₁₄₃/I₁₁₈₃, I₁₆₀₆/I₁₆₆₇ and I₁₁₄₃/I₁₀₇₇ were used as assay standards for pH, redox potential and ROS level detection, respectively. The SERS multiplexed transparent microneedles (SERS mtMNs) linearly responded to pH in the range of 4.0-8.0, redox potential in the range of 417.0-599.8 mV, and ROS levels in the range of 0-480 ng/mL, demonstrating a significant ability to detect complex inflammation in vivo, in situ and in real-time.

Electrochemiluminescence reaction pathways in nanofluidic devices

Nanofluidic electrochemical devices confine the volume of chemical reactions to femtoliters. When employed for light generation by electrochemiluminescence (ECL), nanofluidic confinement yields enhanced intensity and robust luminescence. Here, we investigate different ECL pathways, namely coreactant and annihilation ECL in a single nanochannel and compare light emission profiles. By high-resolution imaging of electrode areas, we show that different reaction schemes produce very different emission profiles in the unique confined geometry of a nanochannel. The confrontation of experimental results with finite element simulation gives further insight into the exact reaction ECL pathways. We find that emission strongly depends on depletion, geometric exclusion, and recycling of reactants in the nanofluidic device.