Ultrasensitive Detection of a Protein by Optical Trapping in a Photonic-Plasmonic Microcavity

TL;DR

This paper introduces an ultra-sensitive protein detection method using optical trapping in a photonic-plasmonic microcavity, achieving femto-Molar sensitivity in real-time with minimal sample volumes.

Contribution

It proposes a novel mechanism combining optical trapping and plasmonic field enhancements for highly sensitive, real-time protein detection in microfluidic volumes.

Findings

Achieved femto-Molar sensitivity for protein detection.

Validated the trapping mechanism with Mie theory simulations.

Demonstrated real-time detection in microliter samples.

Abstract

Microcavity and whispering gallery mode (WGM) biosensors derive their sensitivity from monitoring frequency shifts induced by protein binding at sites of highly confined field intensities, where field strengths can be further amplified by excitation of plasmon resonances in nanoparticle layers. Here, we propose a mechanism based on optical trapping of a protein at the site of plasmonic field enhancements for achieving ultra sensitive detection in only microliter-scale sample volumes, and in real-time. We demonstrate femto-Molar sensitivity corresponding to a few 1000s of macromolecules. Simulations based on Mie theory agree well with the optical trapping concept at plasmonic 'hotspots' locations.