Protein detection by optical shift of a resonant microcavity

TLDR

We present an optical biosensor with unprecedented sensitivity for detecting unlabeled molecules. The device transduces protein binding via shifts in whispering‑gallery‑mode resonances of a dielectric microparticle coupled to an eroded optical fiber, detected as wavelength‑dependent dips in transmitted light. The sensor achieved high sensitivity, detecting bovine serum albumin adsorption and streptavidin–biotin binding.

Abstract

We present an optical biosensor with unprecedented sensitivity for detection of unlabeled molecules. Our device uses optical resonances in a dielectric microparticle (whispering gallery modes) as the physical transducing mechanism. The resonances are excited by evanescent coupling to an eroded optical fiber and detected as dips in the light intensity transmitted through the fiber at different wavelengths. Binding of proteins on the microparticle surface is measured from a shift in resonance wavelength. We demonstrate the sensitivity of our device by measuring adsorption of bovine serum albumin and we show its use as a biosensor by detecting streptavidin binding to biotin.