Bioassays on FO probe surface. The surface of the gold-coated fiber-optic probe has a carboxyl monolayer to which capture antibodies are covalently bound. Target antibodies bind the capture antibodies in a label-free configuration.

The FOx BIOSYSTEMS biosensor can accurately detect, quantify and measure the potency of your target of interest in a variety of sample matrices. Label-free nM to µM sensitivities in as little as one minute make our fiber-optic surface plasmon resonance (FO-SPR) biosensor a versatile development tool.
- Fast assay time (from 1 to 20 min)
- Clinically relevant sensitivity (0.97 – 80 ng/mL in 100x diluted sample)
- Results better than ELISA, in much less time
- Minimum sample preparation (serum, plasma and whole blood)
hIgG screening.
The protein A sensor probe allows for fast label free concentration screening of total hIgG in cell culture samples. With a fast assay time, down to 1 minute, and ng/ml to µg/ml sensitivity with a wide dynamic range with excellent reproducibility this is an ideal tool for rapid screening.

Excellent repeatability. Calibration curves obtained from plotting the SPR shift against a function of the concentration gave almost identical results when performed five weeks apart.
Case study:
Label-free quantification in bioproduction samples
Monitoring the production of antibodies is crucial for understanding and optimizing the process. In this study, production of the therapeutic monoclonal antibody, Trastuzumab (TRA), was used to investigate a new method to monitor production in real time.
ELISA is the most commonly used protein detection method, but this is a slow technique and is typically run in batches of samples collected over time, greatly increasing the time to result.
WHITE FOxTM from FOx BIOSYSTEMS offers a fast and convenient alternative to ELISA, giving comparable results within 10 minutes when using pre-functionalized probes. The dip-in protocol means that even individual samples can be analyzed straight after collection, directly in the sample medium, allowing for a rapid turnaround that facilitates near-real-time process optimization.
Relevant publications
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Detection of Breast Cancer-Specific Extracellular Vesicles with Fiber-Optic SPR Biosensor
February 15, 2023
New technology for the development of molecular markers
December 7, 2022
Innovative FO-SPR Label-free Strategy for Detecting Anti-RBD Antibodies in COVID-19 Patient Serum and Whole Blood
January 27, 2022
WHITE FOxTM technical specifications
April 8, 2021
FO-SPR biosensor calibrated with recombinant extracellular vesicles enables specific and sensitive detection directly in complex matrices
February 23, 2021
Probing the force-induced dissociation of aptamer-protein complexes
February 20, 2014
Affinity comparison of p3 and p8 peptide displaying bacteriophages using surface plasmon resonance
September 30, 2013
Selection of aptamers against Ara h 1 protein for FO-SPR biosensing of peanut allergens in food matrices
May 15, 2013
Fast and accurate peanut allergen detection with nanobead enhanced optical fiber SPR biosensor
February 15, 2011
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