Interferometric multilayered nanomaterials for imaging unlabeled biorecognition events

Abstract

Abstract There is an intense scientific activity on nanomaterials for biosensing, supported by their great potential to conceive powerful applications in chemistry, biology, and medicine. In addition to meet the required analytical parameters, the social impact of these advances is also highly influenced by cost, simplicity, and portability aspects, which are critical in label-free systems. This paper addresses the design, development, and experimental assessment of multilayered nanomaterials to transduce unlabeled biorecognition assays as both constructive and destructive interferences, by means of simple and effective imaging setups. The materials rely on superposed nanometric films of metals (gold and Ag-In-Sb-Te alloy) and a dielectric (zinc sulphide) deposited on a polymeric substrate. They are tailored to display maximal (constructive and destructive) interferences for immunoassays performed on their surface, and then fabricated by sputtering and characterized by focused ion beam scanning electron microscopy. Herein we also address the development of a simple optical setup that exploits standard DVD laser units to scan by imaging the reflected interferometric response of microarrayed immunoassays. The bioanalytical performance of the approach is experimentally assessed using a representative model immunoassay (BSA/anti-BSA) and a competitive immunoassay to quantify a low molecular weight drug (sulfasalazine), reaching detection limits of 460 and 11 ng mL−1 of unlabeled targets, respectively. This study also explores two alternative one-shot interferometric imaging approaches that provide insights into simpler and faster strategies for label-free biosensing.