Nanoscale platform for control, interrogation and optimization of molecular sensing interfaces, toward application to nanomedicine

Sensitive transduction of bio-molecular binding events on chip carries profound implications to the outcome of a range of in vitro sensors. This includes biosensors that address research as well as diagnostic questions of clinical relevance, e.g., profiling of biomarkers, protein expression, drug and toxicity screening, drug-efficacy monitoring, among others. Nanostructured biosensors in general, and plasmonic biosensors in specific constitute a promising advance in this direction owing to their ability to cater to better sensitivity, response times, and miniaturization, in addition to imparting smart, intelligent capabilities to interfaces. Plasmonic biosensors take advantage of electromagnetic (EM) near-field enhancements at nanoscale geometries such as curvatures or gaps of the order of only a few nanometers, in order to transduce molecular binding events with high sensitivity. The geometric length scales involved, typically overlap with the size of small proteins. For a successful outcome and rational design of plasmonic sensors, it is crucial to attain a control over fabrication down to molecular resolutions. Such control should enable an orthogonal access to the different geometric attributes (e.g., size, separation, curvatures, topography) and uniformly so, across macroscopic areas (of at least a few square millimeters). This is necessary to ensure that the influence of the geometric variables on the optical or biomolecular response is adequately mapped. The uniformity across macroscopic lengthscales will enable correlating the macroscopic response with what happens at the nanoscale, and further enabling the use of analytical tools with macroscopic foot prints (e.g., XPS, IR, SPR). In this direction, the talk would present approaches to fabrication of gold nanoarrays of different types, their optical and spectroscopic investigations correlated with their geometries in application to surface-enhanced Raman spectroscopy based molecular sensing. The fabrication schemes exploit combination of molecular and colloidal self-assembly, delivering nanoarrays with feature separations down to sub-10nm regime, systematic and orthogonal control over different geometric variables, exhibiting low standard deviations (< 10%) across full-wafer level. These approaches enable a promising nanoscale platform to efficient investigations and rational optimization of plasmonic biointerfaces.