Authors: D. Hill, S. Hearty, L. Basabe-Desmonts, R. Blue, C. McAtamney, R. O’Kennedy, B. MacCraith
Affilation: Dublin City University, Ireland
Pages: 237 - 240
Keywords: parabolic chip, optical sensor, cardiac biomarkers, mass producible, point of care, low limit of detection
A polymer paraboloid microchip is utilised for performing fluorescence detection in point-of-care devices, employing a mass producible and effective strategy. The chip consists of a single piece of moulded plastic containing nine parabolic elements, with planar upper surfaces. The chip is illuminated from below with collimated light which is then reflected from the edges of the paraboloid to the focal point on the upper plane. The light incident on the upper plane is supercritically reflected, so excitation of fluorophores on the plane occurs due to the evanescent wave, which extends only tens of nanometres above the surface, providing good surface discrimination. Light from the fluorophores is emitted preferentially into supercritical angles due to the nature of the dipoles oscillating on a planar dielectric interface. This is then collected again by the paraboloid edges reflecting light towards the detector. By counting the number of photons incident on the detector, a relationship between the analyte concentration and fluorescence can be found. Herein, we demonstrate a model assay developed to test the feasibility of using this technology to facilitate improved detection of clinically relevant biomarkers. A sandwich immunoassay based on the traditional ELISA format to the microchip platform for a detection of a specific cardiac biomarker was rapidly and efficiently transferred onto the paraboloid chips. An aldehyde-activated dextran surface coating was utilised to ensure an optimal capture antibody immobilisation. Reliable data was generated, quantifying the cardiac biomarker protein under physiological conditions. Low cost fabrication, dedicated optical interrogation instrumentation and antibody-compatible surface derivatisation, allied with the clear amenability for incorporation of a microfluidic sample delivery component, indicate that this device offers a very real alternative to traditional diagnostic assay platforms and has significant potential for application in a point-of-care setting.