Sensitive Bioassay with an Ultralarge Dynamic Range via Microlaser Ensemble Quenching

We present a bioassay platform that leverages the lasing threshold distribution in a microlaser ensemble (ME), consisting of hundreds of individual microlasers, to measure analyte concentrations in solution. An ME is formed by placing dye-doped microbeads in a micro Fabry–Perot cavity. The microbeads are surface-modified with biorecognition molecules to capture analytes, while the quenchers resulting from the presence of the analytes on the microbeads' surfaces increase the lasing thresholds of the microlasers. Since the number of analytes varies from one microbead (or microlaser) to another due to the randomness in binding processes, a distribution of the analytes (and hence the quenchers) in the ME is created, which in turn leads to a lasing threshold distribution in the ME. Experimentally, multiple pumping energy densities are used to probe the lasing threshold distribution. A theoretical model is used to map the lasing threshold distribution to the analyte distribution in the ME, and then to recover the analyte concentration in solution. Using streptavidin as a model system, our platform achieves a detection limit of 0.1 pg/mL and a dynamic range exceeding 5 orders of magnitude, showing that the ME quenching method can provide a low detection limit with a superior dynamic range.