Engineering Quantum Dots and Photonic Metamaterials for Ultrasensitive and Multiplexed Digital Resolution Biomolecule Detection

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This project will develop highly sensitive approaches for detecting many disease-related molecules, called “biomarkers,” in blood at the same time. These biomarkers will be detected by binding to light-emitting nanoparticles, called Quantum Dots (QDs), that serve as a bright tag. By designing QDs to be easily distinguished from each other, the research team envisions the capability to detect as many as 45 different biomarkers in a single blood droplet. Biomarker detection will be performed on engineered surfaces called “photonic crystals” (PCs) that are able to amplify the QD brightness by several thousand-fold, allowing QDs to be counted individually. The PCs also serve to direct the QD light output in specific directions that are measured to tell the difference between each type of QD. In addition, new approaches will be developed that can rapidly convert each biomarker molecule into many QDs on the PC surface. By combining PCs and QDs, the sensor can be simple, fast, and inexpensive, enabling biomarker tests to be performed in places like clinics and hospitals. The Team will develop a broadly accessible short course entitled “What’s in Your Blood? Genomics Testing and You,” to be offered through the Osher Lifelong Learning Institute. Aspects of the course will be adapted for public-facing programs offered through the Woese Institute for Genomic Biology and an interactive display at “World of Genomics” events that are offered annually at large science museums.Ultrasensitive, ultraselective, and highly multiplexed detection of biomolecules within complex media is a central component of disease diagnostics, life science research, and environmental monitoring. New “digital resolution” biomolecular detection methods are leading toward unprecedented detection limits, but are hindered by complex procedures, thermal cycling, and stringent sample preparation. Recent advances in the capability for photonic metamaterial surfaces to substantially amplify the collected photon output from semiconductor quantum dots are making assays with digital molecule precision compatible with small, low cost instruments. Applying QD tags with photonic crystal fluorescence amplification makes it possible to digitally count target molecules and to perform multiplexing through the ability to distinguish QD emission wavelengths by their outcoupled emission pattern. As a result, single-step, room temperature, enzyme-free assays for microRNA with attomolar-level detection limits and 6 log(10) orders of dynamic range can be achieved, with the potential to extend even further. In this project, the Cunningham and Smith labs will design and synthesize novel QD tags that incorporate engineered multispectral brightness, encodable emission saturation, and encodable PC enhancement factor. The QDs will specifically couple with photonic metamaterial surfaces to enhance their excitation, to modulate their lifetime, and to extract their emission to differentiate up to 45 distinct QD labels for molecular multiplexing. Finally, the team will introduce a new paradigm for biomolecule detection in which each target molecule can generate multiple downstream digital-resolution QD detection events to achieve ultrasensitive detection limits with simple and rapid methods.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.