In-situ ultra-sensitive infrared absorption spectroscopy of biomolecule interactions in real time with plasmonic nanoantennas

TLDR

Infrared absorption spectroscopy provides detailed, label‑free molecular structural information, but its sensitivity is limited by strong water absorption, hindering kinetic studies in native aqueous environments. The study introduces a plasmonic chip that enables real‑time, high‑sensitivity monitoring of protein and nanoparticle interactions in aqueous media. The method uses plasmonic nanoantennas to enhance infrared absorption and a non‑classical internal reflection scheme, allowing chip‑based monitoring of biological samples in water. The platform expands infrared spectroscopy to new biological interactions and offers a unique chip‑based technology for real‑time monitoring.

Abstract

Infrared absorption spectroscopy is a powerful biochemical analysis tool as it extracts detailed molecular structural information in a label-free fashion. Its molecular specificity renders the technique sensitive to the subtle conformational changes exhibited by proteins in response to a variety of stimuli. Yet, sensitivity limitations and the extremely strong absorption bands of liquid water severely limit infrared spectroscopy in performing kinetic measurements in biomolecules’ native, aqueous environments. Here we demonstrate a plasmonic chip-based technology that overcomes these challenges, enabling the in-situ monitoring of protein and nanoparticle interactions at high sensitivity in real time, even allowing the observation of minute volumes of water displacement during binding events. Our approach leverages the plasmonic enhancement of absorption bands in conjunction with a non-classical form of internal reflection. These features not only expand the reach of infrared spectroscopy to a new class of biological interactions but also additionally enable a unique chip-based technology. Infrared absorption spectroscopy provides important information about molecules, but is hampered by the absorption of water. Adato and Altug exploit the plasmonic enhancement from nanoantennas to overcome this, enabling chip-based monitoring of biological samples in aqueous environments.