FOx BIOSYSTEMS sandwich assays applications icon

The unique fiber-optic design of the FOx BIOSYSTEMS probe allows the implementation of sandwich-style bioassays using gold nanoparticles. This instantly amplifies the surface plasmon resonance signal without the lengthy enzymatic reaction incubations of an ELISA, providing increased detection sensitivity and speed.

Amplifying the signal in this way allows fast, physiologically relevant detection. Therefore, the FOx BIOSYSTEMS technology can detect physiologically active levels of biotherapeutics quickly and accurately, allowing for rapid dose adjustment in preclinical and clinical research and testing.

Case study: FO-SPR sandwich assay

Infliximab (IFX) is a monoclonal antibody used for the treatment of inflammatory bowel disease. Optimizing the therapeutic outcome requires concentration measurements which are currently obtained using the slow ELISA or less sensitive lateral flow-based immunotherapy techniques.

Tests using the FO-SPR probes and an IFX-specific capture antibody showed that surface plasmon resonance alone was unable to detect concentrations lower than 1 μg/ml. Using the same technology with SPR signal amplification via gold nanoparticles conjugated to detection antibody, a limit of detection (LOD) of 2.2 ng/ml was obtained in 100-fold diluted serum.

Sandwich bioassays on FO probe surface. The FOx BIOSYSTEMS instrument is capable of running standard bioassays that provide real-time, label-free data or gold nanoparticle sandwich assays to boost the sensitivity and speed of the surface plasmon resonance signal.

Multiplexed sandwich bioassays on FO probe surface. Using sequential incubation of gold nanoparticle tagged antibodies, FO-SPR can accurately quantify two targets with co-immobilized bioreceptors.

Case study: Multiplexed FO-SPR sandwich assay

Multiplexing bioassays reduces the required sample volume, time, and cost of analysis.  It also allows to accurately determine ratios of target concentration. To achieve this, we developed a novel surface chemistry to allow the stable, oriented co-immobilization of autoimmune antibodies.

Activating the FO-SPR probe with a Cobalt (III) stabilized nitrilotriacetic acid (NTA) chemistry allowed the accuratel quantification of the two targets in both buffer and plasma with a gold nanoparticle (AuNP) signal amplification sandwich assay. The LoD for two mutants of ADAMTS13 in 200-fold diluted plasma were 3.38 and 2.31 ng/ml respectively.

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