Force Discrimination for Enhanced Biosensor Specificity of Micro-Retroreflector Assays
J.D. Knoop, S.M. Kemper, T. Sherlock, E. Cacao, P. Ruchhoeft, R.C. Willson
University of Houston, US
Keywords: retroreflector, magnetic particles, Rickettsia conorii, biosensors, force discrimination
Abstract:In nearly all diagnostic/bioanalytical methods other than mass spectrometry, what is actually detected is a label of some sort, and the sensitivity and simplicity of detection of this label limits assay performance. Non-specific interactions between the label and assay surfaces can also hinder results and lead to false-positives. This work introduces magnetic particles as labels in assays based on microfabricated retroreflectors. The magnetic properties of the particles can also be used to discriminate against non-specific interactions. The detection surface is composed of arrays of microfabricated retroreflector tetrads. Retroreflectors return light directly to its source and are readily detectable with inexpensive optics. A detector tetrad is composed of four retroreflectors; one assay retroreflector decorated with antibodies is surrounded by three always-on reference reflectors without antibodies. The assay can easily detect the presence of a single particle bound to the surface. One or two Rickettsia conorii bacteria have been shown to hold down a 1.0 µm magnetic particle coated with rabbit polyclonal anti-Rickettsia antibodies, supporting the possibility of detecting a single target pathogen with this assay.