Label-Free Biosensing in Complex Media: A Referencing Approach

We present a novel approach to reference-compensated label-free affinity biosensing in complex media. Unlike conventional approaches that employ surfaces with different biological functionalities in the detection and reference channels to produce a reference-compensated sensor response, the new approach (referred as to single surface referencing (SSR)) uses a single functionalized surface split into the detection and reference channel to which complex sample (detection channel) and complex sample mixed with biomolecules binding to the analyte and thus inhibiting the binding of the analyte to the functionalized surface (reference channel) is introduced. This approach ensures that (i) only the detection channel captures the analyte and (ii) nonspecific binding incurred in the detection and reference channels are the same. We evaluate this approach in a model biosensing experiment, detection of a cancer biomarker carcinoembryonic antigen (CEA) in blood plasma using antibody against CEA and a surface plasmon resonance (SPR) biosensor. We detect CEA in three different blood plasma samples and demonstrate that this novel referencing approach provides more accurate results and lower biological variability than the conventional referencing.