Abstract

Techniques to observe and track single unlabelled biomolecules are crucial for many areas of nanobiotechnology; offering the possibility for lab-on-a-chip medical diagnostics operating at their ultimate detection limits, and to shed light on important nanoscale biological processes such as binding reactions, conformational changes, and motor molecule dynamics. Impressive progress has been made over the past few years to extend the sensitivity of such techniques, primarily via the evanescent field enhancement provided by optical microcavities [1, 2] or plasmonic resonators [3]. However, such approaches expose the biological system to greatly increased optical intensity levels, which can severely impact biological function, growth, structure and viability [4]. Here, we introduce an evanescent biosensing platform that operates at the fundamental precision limit introduced by quantisation of light. This allows a five order-of magnitude reduction in optical intensity whilst maintaining state-of-the-art sensitivity and enabling quantum noise limited tracking of single biomolecules as small as 3.5 nm.

© 2017 IEEE