A fast and reproducible ELISA laser platform

Optofluidic bio-lasers are currently of high interest for sensitive, intra-cavity, biochemical analysis. In comparison with conventional methods such as fluorescence and colorimetric detection, lasers provide us with a method for amplifying small concentration differences in the gain medium, thus achieving high sensitivity. Our previous research has demonstrated that sandwich IL-6 ELISA performed in capillary-based optofluidic laser cavity was able to achieve ultrahigh detection sensitivity (LOD between 1-10 fg/ml) with a small sample volume ( 20 μL). However, such approach has several limitations such as low repeatability and long assay time ( 8 hours in total, 7 hours for laser measurements). Here, we developed a novel on-chip ELISA laser platform by directly fabricating micro-wells on dielectric mirrors for immunosorbent reactions. Polystyrene microbeads of 30 μm in diameter were placed in the wells to optically enhance the resonance cavity during laser measurement, thus significantly improving reliability, shortening assay time ( 1.5 hours, 30 minutes for laser measurements) while maintaining the attractive features such as small sample volume and very high sensitivity (LOD 0.1 pg/mL for IL-6). This work pushes the ELISA laser one step closer to solving problems in realworld biochemical analysis.