Ultrahigh sensitivity made simple: nanoplasmonic label-free biosensing with an extremelylow limit-of-detection for bacterial and cancer diagnostics

Abstract

We present a simple and robust scheme for biosensing with an ultralow limit-of-detection down to several pg cm−2 (or severaltens of attomoles cm−2) based on optical label-free biodetection with localized surface plasmon resonances. Thescheme utilizes cost-effective optical components and comprises a white light source, aproperly functionalized sensor surface enclosed in a simple fluidics chip, and aspectral analyzer. The sensor surface is produced by a bottom-up nanofabricationtechnique with hole mask colloidal lithography. Despite its simplicity, the methodis able to reliably detect protein–protein binding events at low picomolar andfemtomolar concentrations, which is exemplified by the label-free detection of theextracellular adherence protein (EAP) found on the outer surface of the bacteriumStaphylococcus aureus and of prostate-specific antigen (PSA), which is believedto be a prostate cancer marker. These experiments pave the way towards anultra-sensitive yet compact biodetection platform for point-of-care diagnostics applications.