High-Throughput and Ultra-Sensitive Biosensing and Spectroscopy by Plasmonics

Abstract

Listen

Translate article

New healthcare initiatives including personalized medicine, global health, point-of-care and early disease diagnostics are demanding breakthrough developments in biosensing technologies. Unfortunately, current biosensors are time consuming, costly, bulky, require a relatively advanced infrastructure and trained laboratory professional, making them unsuitable for disease control and patient care in the field. To address these challenges Altug Lab is developing cutting edge optical biosensor and spectroscopy systems by exploiting plasmonics. In a recent work, Altug’s lab introduced a high-throughput and label-free protein microarray technology with nearly one million sensor elements that enable reliable and quantitative detection of bio-chemicals. By coupling wide-field plasmonic arrays with lens-free computational on-chip imaging they demonstrated handheld, lightweight and low-cost diagnostic tools suitable for point-of-care applications. The sensor is based on metallic nanohole arrays and exploits highly sensitive surface plasmons and associated extra-ordinary optical transmission phenomenon. Her lab showed that such optical sensors can detect live and intact viruses in biological media at medically relevant concentrations. Furthermore, by uniquely integrating nanofluidics and optics on sub-wavelength nanohole arrays, they innovated a way to overcome mass-transport problem severely limiting sensor performance at low-analyte concentrations. Altug’s lab also working on novel ultrasensitive infrared vibrational spectroscopy techniques. Infrared absorption spectroscopy is a powerful biochemical analysis tool that can fingerprint molecules in a label-free fashion. Its molecular specificity renders the technique to be sensitive to the subtle conformational changes exhibited by biochemical such as proteins. Yet, its low sensitivity and strong water absorption severely limit infrared spectroscopy to perform sensitive and real-time measurements of biomolecules and molecular interactions in aqueous/water environment. By engineering on-chip optical nano-antennas, her lab demonstrated for the first time that fundamental Beer-Lambert law can be overcome and the intrinsic signals of proteins can be enhanced by more than 10,000 times. Significantly using extreme field concentration at interfaces, they showed real-time and in-situ monitoring of biomolecular interactions from low quantities of molecules. The method, exploiting dramatically strong light-matter interactions enabled by sculptured nano-scale metallic particles, opens up new paradigms in ultra-sensitive vibrational spectroscopy.