Photonic crystal enhanced excitation, directional extraction, and blinking suppression for single quantum dot digital resolution biosensing

While nanoscale quantum emitters are effective tags for measuring biomolecular interactions, their utility for applications that demand single-unit observations are limited by the requirements for large numerical aperture (NA) objectives, fluorescence intermittency (blinking) and poor photon collection efficiency resulted from omnidirectional emission. Here, we report a nearly 3,000-fold signal enhancement achieved through the 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 (~59), even with a low NA lens (NA = 0.5, 50X), and inexpensive optical setup without total internal reflection fluorescence (TIRF) or high gain electron-multiplying camera. The blinking suppression capability of the PC improves the QDs “on-time” from 15% to 85%, providing a novel method to ameliorate signal intermittency issues encountered during ultrasensitive measurements and fast motion tracking at the single particle level. As a representative molecular diagnostic application that requires ultrasensitive detection limits achieved through digital resolution counting of target biomarkers, we developed a QD-tagged “bridge” assay for cancer-associated miRNA biomarkers from a 45 ul sample volume with single-molecule resolution, single-base mutation selectivity, 10 aM (10^-17 Molar) detection limit, and linear dose-response over a 9-log concentration range with a single step, room temperature workflow. Additionally, we clearly observe differential surface motion trajectories of individual QDs when their surface attachment stringency is altered by changing a single base in the target miRNA sequence. Experimental characterization is supported by electromagnetic numerical simulations to show that the synergistic properties of the PC-QD system achieves its overall enhancement from the independent contributions of enhanced excitation, enhanced extraction (including both photon extraction rate improvement and quantum efficiency change via the Purcell effect) and enhanced collection efficiency. The approach presented here demonstrates a path toward digital resolution detection of a broad range of biomolecular analyte classes for ultrasensitive quantitative analysis that combines robust point-of-care instrumentation with simple assay protocols that do not require enzymatic amplification.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Xiong, Yanyu

Contributors dc:contributor

• Cunningham, Brian T

• Photonic Crystal
• Fluorescence Microscopy
• Quantum Dot
• Biosensor
• miRNA Assay

Statement dc:rights

• Copyright 2021 Yanyu Xiong

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/113352

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F113352