White paper 3 | Version 1 | Kim Stevens, Kris Ver Donck, Filip Delport
Based on original publication: Lu et al. (2017) Analytical Chemistry 89, 3664-3671. (1)
Fiber-optic surface plasmon resonance (FO-SPR) is a powerful tool that harnesses the power of SPR in an easy-to-use fiber-optic sensor. In this application note, we demonstrate the potential of FOx BIOSYSTEMS’ FO-SPR instrument to detect proteins or antibodies in crude biological samples such as whole blood and dried blood spots. As an example system, we demonstrate the quantification of a therapeutic monoclonal antibody, infliximab (IFX), in whole blood, dried blood spots, serum and plasma.
A 10-minute FO-SPR bioassay has been developed that is capable of detecting IFX in 10 to 100-fold diluted whole blood, serum and plasma down to a limit of detection of 0.75 ng/ml. The detection limit falls well below the predicted ranges of typical IFX concentrations in patient blood and serum of 0.23−4.5 μg/ml and 0.5 – 10 µg/ml, respectively. For other targets, a lower detection limit may be reached but, for this example, the assay design did not require additional sensitivity.
To confirm this detection range, plasma, and serum from five IFX-treated IBD patients were tested with both the 10-minute FO-SPR assay and ELISA, showing excellent agreement between the two methods (Pearson correlations and intraclass correlation coefficients (ICC) greater than 0.99 in all cases). Furthermore, the bioassay developed here demonstrated that extraction from dried blood spots was 99% efficient, indicating that FO-SPR was not affected by the blood drying process.
Therefore, we have shown that, in just 10 minutes, a FO-SPR sandwich-style bioassay can provide accurate analysis of therapeutically relevant protein and antibody concentrations in crude samples with minimal processing, thus showing great potential as an R&D tool.