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Read our app note “Looking for a faster way to monitor biotherapeutics yield from cell culture?”


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.

hIgG concentration example curve on protein A probes. Triplicate data points shown, with CVs well below 5%.

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 a therapeutic monoclonal antibody 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

Found 14 Results
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White paper: WP7 Versatile and fast IgG screening with the Protein A sensor probe

White paper 7 | Version 2 | Kris Ver Donck, Filip Delport, Laura Marin, Emma Buchet, Kim Stevens  SUMMARY FOx BIOSYSTEMS’ fiber-optic surface plasmon resonance technology (FO-SPR) is a robust...


March 20, 2023

Detection of Breast Cancer-Specific Extracellular Vesicles with Fiber-Optic SPR Biosensor

Yildizhan et al. (2023) International Journal of Molecular Sciences DOI: 10.3390/ijms24043764 Extracellular vesicles (EVs) have attracted great attention as potential biomarkers for cancer diagnostics. Although several technologies have been developed…


February 15, 2023

New technology for the development of molecular markers

Georg Johnen, Thomas Brüning, IPA (Institut für Prävention und Arbeitsmedizin der Deutschen Gesetzlichen Unfallversicherung) The detection of specific proteins is the focus of many methods for the diagnosis of occupational…


December 7, 2022

White paper: WP6 Using FO-SPR to select for nanobodies in phage display

White paper 6 | Version 2 | Kris Ver Donck, Dagmara Minczakiewicz, Filip Delport, Kim Stevens Based on original publication: Knez et al. (2013) Analytical Chemistry 85, 10075 - 10082...


April 29, 2022

Innovative FO-SPR Label-free Strategy for Detecting Anti-RBD Antibodies in COVID-19 Patient Serum and Whole Blood

Qu et al. (2022) ACS Sensors DOI: 10.1021/acssensors.1c02215 The ongoing COVID-19 pandemic has emphasized the urgent need for rapid, accurate, and large-scale diagnostic tools. Next to this, the significance of…


January 27, 2022

White paper: WP4 Label-free quantification in bioproduction samples

White paper 4 | Version 4 | Kris Ver Donck², Dagmara Minczakiewicz², Kim Stevens², Gert Struys¹, Thomas Geuens¹, Koen Dierckx¹, Filip Delport² ¹simAbs NV, ²FOx BIOSYSTEMS ABSTRACT This white paper...


October 1, 2021

WHITE FOxTM technical specifications

You can find the technical specifications of the White FOxTM here: DOWNLOAD


April 8, 2021

White paper: WP1 carboxyl probe immobilization for label-free protein quantification

White paper 1 | Filip Delport, Dagmara Minczakiewicz, Kris Ver Donck ABSTRACT This white paper describes a general strategy for optimizing immobilization on the FO-SPR probes and provides some reference...


March 31, 2021

FO-SPR biosensor calibrated with recombinant extracellular vesicles enables specific and sensitive detection directly in complex matrices

Yilidzhan et al. (2021) J. Extracell. Vesicles 10   Extracellular vesicles (EVs) have drawn huge attention for diagnosing myriad of diseases, including cancer. However, the EV detection and analyses procedures…


February 23, 2021

Probing the force-induced dissociation of aptamer-protein complexes

Perez-Ruiz et al. (2014) Anal. Chem. 86, 3084−3091   Aptamers are emerging as powerful synthetic bioreceptors for fundamental research, diagnostics, and therapeutics. For further advances, it is important to gain…


February 20, 2014

Affinity comparison of p3 and p8 peptide displaying bacteriophages using surface plasmon resonance

Knez et al. (2013) Anal. Chem. 85, 10075−10082   Ever increasing demands in sensitivity and specificity of biosensors have recently established a trend toward the use of multivalent bioreceptors. This…


September 30, 2013

Selection of aptamers against Ara h 1 protein for FO-SPR biosensing of peanut allergens in food matrices

Tran et al. (2013) Biosensors and Bioelectronics 43, 245–251    The rising prevalence to food allergies in the past two decades, together with the fact that the only existing therapy…


May 15, 2013

Fast and accurate peanut allergen detection with nanobead enhanced optical fiber SPR biosensor

Pollet et al. (2011) Talanta 83, 1436–1441   This paper is the first report of a fiber optic SPR biosensor with nanobead signal enhancement. We evaluated the system with a…


February 15, 2011

Fiber optic SPR biosensing of DNA hybridization and DNA–protein interactions

Pollet et al. (2009) Biosensors and Bioelectronics 25, 864–869   In this paper we present a fiber optic surface plasmon resonance (SPR) sensor as a reusable, cost-effective and label free biosensor for measuring DNA hybridization and DNA–protein…


December 15, 2009

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For Research Use Only. Not for use in diagnostic procedures.