Quantitative detection of biomarkers has become increasingly important for the diagnosis of diseases. Because of its distinct merits of high sensitivity and high specificity, enzyme-linked immunosorbent assay (ELISA) has been deemed the gold standard for biomarker analysis. However, the detection limit of current commercial ELISA products is on the level of several pg/mL, which cannot meet the requirement of many early-stage disease diagnosis applications. One of the promising solutions to improve ELISA is micro/nano-photonic technologies. In particular, high-quality whispering-gallery-mode (WGM) microcavities with very low loss are one of the leading candidates because of their unique ability to build up very strong in-cavity light for investigation of light-matter interactions, and thus have great potential in biochemical sensing and lab-on-a-chip applications.
A research team led by Prof. Aping Zhang and Prof. Hwa-Yaw Tam developed an optofluidic biochip with high-quality polymer WGM microlaser sensors for ultrasensitive detection of biomarkers with ELISA. An in-house optical 3D µ-printing technology is used to rapidly fabricate low-threshold WGM microlasers. The fabricated WGM microlaser sensors were then integrated together with optical fibres upon a microfluidic chip and then modified in situ with biomolecules for highly selective biomarker detection. It is demonstrated that such an optofluidic biochip enables on-chip optofluidic ELISA of the disease biomarker vascular endothelial growth factor at the extremely low concentration level of 17.8 fg/mL, which is over 2 orders of magnitude better than the ability of current commercial ELISA kits.
The work is published in the journal Lab on a Chip (IF: 6.77) and featured on the Front Cover.
