Get extra-fast, ultra-sensitive results using gold nanoparticle sandwich assays on our fiber-optic surface plasmon resonance biosensor.

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.

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.