  Biosensors are an essential tool for medical diagnostics, environmental
monitoring and food safety. Typically, biosensors are designed to detect
specific analytes through functionalization with the appropriate capture
agents. However, the use of capture agents limits the number of analytes that
can be simultaneously detected and reduces the robustness of the biosensor. In
this work, we report a versatile, capture agent free biosensor platform based
on an array of porous silicon (PSi) thin films, which has the potential to
robustly detect a wide variety of analytes based on their physical and chemical
properties in the nanoscale porous media. The ability of this system to
reproducibly classify, quantify, and discriminate three proteins is
demonstrated to concentrations down to at least 0.02g/L (between 300nM and
450nM) by utilizing PSi array elements with a unique combination of pore size
and buffer pH, employing linear discriminant analysis for dimensionality
reduction, and using support vector machines as a classifier. This approach
represents a significant step towards a low cost, simple and robust biosensor
platform that is able to detect a vast range of biomolecules.
