Ultrasensitive detection of a protein by optical trapping in a photonic‐plasmonic microcavity

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 1000 s of macromolecules. Simulations based on Mie theory agree well with the optical trapping concept at plasmonic hotspots locations. ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Hybrid optical-thermal devices and materials for light manipulation and radiative cooling

“…High spectral resolution is typically unattainable in purely plasmonic sub-wavelength structures due to high dissipative losses of metals. We have previously demonstrated that this limitation can be overcome by combining plasmonic and high-Q photonic elements into hybrid optoplasmonic sensor platforms [14][15][16][17][18][19] . Among the emergent properties of optoplasmonic structures is their ability to simultaneously achieve extreme spectral and spatial localization of light.…”

Taking detection to the limit with optical microcavities: Recent advances presented at the 560. WE Heraeus Seminar

“…The high quality allows for narrow linewidth lasing [89][90][91] and the birefringence allows for example for temperature stabilization techniques [92] and complex polarization behaviors [93]. The detection of biomolecules, such as adsorption of bovine serum albumin often serves as a first experiment to test the detection limits of a particular optical microcavity [34,94,95]. For biosensing, the microcavities are further modified with molecular receptors so that the microcavity transduces specific molecular interaction events into an optical signal.…”

“…3, have been introduced as means for boosting the frequency shifts in WGM biosensing [49,94,95,[98][99][100][101], bringing single molecule detection within reach. First demonstrations of enhanced signals have been shown for the unspecific adsorption experiments with bovine serum albumin protein BSA, achieving detection limits down to single proteins and femotomlar concentration levels [22,94,95,102,103]. Biosensing on the single molecule level was demonstrated by monitoring interactions with specific nucleic acid receptor oligomers, discriminating matching and mismatched strands from their markedly different interaction kinetics [7].…”

Ultra-high Q/V hybrid cavity for strong light-matter interaction

“…As a result, Q/V values up to 10 7 (λ/n) 3 21,22 have been predicted by simulations, with the best experimental results reaching values of 10 5 (λ/n) 3 . 23 It is also worth noting that hybrid cavities maintain the nanoscale plasmonic hotspot which is advantageously situated in the low index medium and which makes the device suitable for applications in biosensing and optical trapping, 24,25 while the lower loss compared to plasmonic cavities reduces thermal effects, e.g., the effect of Brownian motion counteracting optical trapping. 26 Here, we report on a 1D PhC nanobeam cavity vertically coupled to a bowtie nanoantenna.…”