Plasmonic flow-through biosensor using a polymeric substrate

Substrates for plasmonic sensors in a flow-through configuration are mostly fabricated by cost-intensive clean room processes, whereas high-volume diagnostic devices are typically made of polymers. This contrast could limit the application of this efficient flow regime in mass-produced devices. In order to become more compatible with polymer processing, a commercially available polycarbonate filter membrane has been evaluated as a substrate for plasmonic flow-through biosensing. The membrane has been sputtered with gold and its sensitivity to changes of bulk refractive index has been determined by transmission measurements using sodium chloride solutions. The sensitivity has been evaluated by determining the wavelength barycenter in a wavelength interval from 470 to 800 nm. The highest determined sensitivity to variations in bulk refractive index is 117 nm RIU−1 (refractive index units). This sensitivity is smaller than that of regular arrays of nanoholes. But the integrating character of the applied evaluation leads to an average standard deviation of 0.005 nm which results in a resolution of 4.1 ⋅ 10−5 RIU. This resolution is sufficient for the detection of protein adsorptions. The proof of principle has been shown with bovine serum albumin and a simplified immunoassay, which consists of the sequential addition of protein A, an IgG antibody and its corresponding antigen. The results show the applicability of this polymeric membrane for biosensing applications. These substrates could enable plasmonic sensing in a flow-through configuration in disposable diagnostic devices.