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KU Leuven’s Biosensors group develops first label-free assay characterizing COVID-19 antibodies directly in patient blood, using FOx BIOSYSTEMS platform

By March 8, 2022No Comments

Press release

The White FOx FO-SPR instrument can rapidly analyze antibody kinetic profiles against SARS-CoV-2 spike proteins in serum and whole blood from COVID-19 patients.

Diepenbeek, Belgium, March 8th, 2022 – FOx BIOSYSTEMS, a company on the mission to revolutionize life science and pharmacological research with innovative real-time, analysis products and the Biosensors research group at KU Leuven, focused on developing innovative bio-molecular detection concepts and miniaturized analysis systems, announced a novel, label-free assay that can characterize the polyclonal antibody response against SARS-CoV-2 directly in patient blood[i].

Understanding patients’ immune status regarding previous SARS-CoV-2 exposure is crucial during the current COVID-19 pandemic. It has even been hypothesized that not just the level of antibodies, but also the binding kinetics profile, or binding rate, of these antibodies may play a role in disease severity [ii],[iii]. Many antibody detection methods, including enzyme-linked immunosorbent assay (i.e. ELISA), require sample processing and only provide the level or amount of antibody response but not information on the binding kinetics profile.

The Biosensors group showed that fiber-optic surface plasmon resonance (FO-SPR) is an effective method to differentiate COVID-positive from COVID-negative patient samples at least as well as ELISA, but also much faster (i.e. within 30 minutes) because it can be performed directly in undiluted patient blood. More importantly, in addition to determining the level of the antibody response, this novel, label-free method was also able to assess the binding kinetics of the polyclonal antibody response against the receptor binding domain (RBD) of SARS-CoV-2 spike protein, using the White FOx FO-SPR platform from FOx BIOSYSTEMS.

Dr. Dragana Spasic, Research Manager from the Biosensors group, who led this study, commented:

“The fact that our data not only determines the antibody levels in these patients, but also the corresponding binding kinetics, means that this test could be used to further study whether antibody binding kinetics play a role in COVID-19 severity. This would be a true breakthrough in our understanding of this disease.”

Filip Delport, CTO and co-founder of FOx BIOSYSTEMS said:

“We are excited about this demonstration of a relevant use of FO-SPR in real world applications. Notably, the sensitivity and kinetic information of this label-free bioassay, in combination with the ability to analyze unpurified blood samples directly, provides a much shorter time-to-result of only 30 min compared to 4 hours for conventional ELISA. The affinity of these antibodies to their target should provide insight into disease progression and severity, giving it great potential for fast analysis of COVID immune status and potentially other immune-related diseases.”

About the study:

This press release is based on the publicationi by Qu et al. “Innovative FO-SPR Label-free Strategy for Detecting Anti-RBD Antibodies in COVID-19 Patient Serum and Whole Blood.” The study was performed in a collaboration between the Biosensors group and PharmAbs from KU Leuven, University Hospital Leuven and AZ Groeninge Hospital, Kortrijk.


FOx BIOSYSTEMS is a dynamic Belgian company on a mission to revolutionize the life science and pharmacological research markets with innovative real-time, label-free analysis products. The basis of our success is a novel fiber-optic-based surface plasmon resonance (FO-SPR) biosensor which enables our users to generate high-quality, cost-effective biomolecular data fast, and over a wide range of applications. The White FOx is ready to take its place in your high-tech lab. For more information visit

About Biosensors group:

The Biosensors group is headed by Professor Jeroen Lammertyn within the MeBioS (Mechatronics, Biostatistics and Sensors) Division of the Biosystems Department at KU Leuven, Belgium. The fundamental research activities of the group focus on the development of novel biomolecular detection concepts and miniaturized analysis systems. The applications span a broad range of sectors including medical and food diagnostics. The Biosensors group closely follows the emerging field of biosensing and is active in the following domains: (1) cutting edge microfluidic technologies (e.g. droplet-based, digital and low cost point-of-care platforms) that are being investigated in collaboration with other groups both as life science research tools and for diagnostic applications; (2) advanced concepts for functionalization of various surfaces and development of smart surfaces with highly controlled numbers of bioreceptors (e.g. through utilization of DNA origami); (3) an innovative fiber optic-based surface plasmon resonance (FO-SPR) system as a fully automated platform for the implementation of immuno- and DNA-based bioassays, as well as real-time monitoring of various biomolecular interactions and (4) novel immuno- and DNA nanotechnology-based bioassay concepts for integration with in-house generated and commercially available platforms. For more information visit: Biosensors group – MeBioS (

Media contact


Thomas van Elzakker, CEO

T: +32 11 28 69 73


[i] Qu, J-H et al. Innovative FO-SPR Label-free Strategy for Detecting Anti-RBD Antibodies in COVID-19 Patient Serum and Whole Blood. ACS Sens. 2022, doi: 10.1021/acssensors.1c02215

[ii] Tang, J et al. Antibody Affinity Maturation and Plasma IgA Associate with Clinical Outcome in Hospitalized COVID-19 Patients. Nat. Commun. 2021, 12, 1221.

[iii] Ren, L et al. The Kinetics of Humoral Response and Its Relationship with the Disease Severity in COVID-19. Commun. Biol. 2020, 3, 780.