Photonic crystal enhanced fluorescence emission and blinking suppression for single quantum dot digital resolution biosensing

While nanoscale quantum emitters are effective tags for measuring biomolecular interactions, their utilities for applications that demand single-unit observations are limited by the requirements for large numerical aperture (NA) objectives, fluorescence intermittency, and poor photon collection efficiency resulted from omnidirectional emission. Here, we report a nearly 3000-fold signal enhancement achieved through multiplicative effects of enhanced excitation, highly directional extraction, quantum efficiency improvement, and blinking suppression through a photonic crystal (PC) surface. The approach achieves single quantum dot (QD) sensitivity with high signal-to-noise ratio, even when using a low-NA lens and an inexpensive optical setup. The blinking suppression capability of the PC improves the QDs on-time from 15% to 85% ameliorating signal intermittency. We developed an assay for cancer-associated miRNA biomarkers with single-molecule resolution, single-base mutation selectivity, and 10-attomolar detection limit. Additionally, we observed differential surface motion trajectories of QDs when their surface attachment stringency is altered by changing a single base in a cancer-specific miRNA sequence. Nanoscale emitters are useful for measuring biomolecular interactions, but are limited by weak signals. Here, the authors use a photonic crystal surface for 3000-fold signal enhancement, achieving single emitter sensitivity with extended on-time, and demonstrate its application in miRNA biomarker sensing.

Automated summary

The authors report a method for achieving nearly 3000-fold signal enhancement using a photonic crystal surface. By enhancing excitation, improving quantum efficiency, and suppressing blinking, the approach enables high signal-to-noise ratio and single emitter sensitivity. The study also demonstrates the application of this method in miRNA biomarker sensing.