Thanks to its unique antibody KD determination platform, ProteoGenix is THE reference in antibody affinity measurement. Measuring interactions with cells, bacteria, proteins in native conformation or performing high throughput KD determination is now made possible thanks to our 3 technologies! Send us your requirements and our PhD account managers will outline the best solution to meet your accuracy/price/timeline expectations.

SPR / GE Biacore X100 – T200 – 8K SPRi / Horiba XelPlex Octet / ForteBio Octet Red
Application “Gold standard” High throughput KD determination Antibody-antigen interaction Biomolecular interaction analysis High throughput KD determination Antibody-cell interaction analysis Biomolecular interaction analysis High throughput KD determination Biomolecular interaction analysis
Technology Surface plasmon resonance (SPR) Surface plasmon resonance imaging (SPRi) Interferometry
Measurement principle Refractive index change Refractive index change Wavelength shift
Label free Yes Yes Yes
Crude sample analysis (cells, bacteria…) No Yes Yes
Possibility to coat proteins (other than antibodies) while maintaining native conformation No Yes Yes
Imaging No Yes Yes
Multiplexing ++ ++++ ++
Limit of detection +++ +++ +
Technology complexity + +++ ++
Cost/antibody + +++ ++
Lead time 2/3 weeks 2/3 weeks 2/3 weeks

Doubts about the most relevant antibody KD determination technique for your study?

Send your requirements to our PhD account manager.

Case study 1: antibody KD determination between an anti-protein X antibody and X protein expressed at the surface of 293T cells by SPRi technology (Horiba XelPlex)

Aim Of The Study

We were asked by a customer to measure the anti-protein X antibody binding affinity against a transmembrane protein X expressed at the surface of 293T cells. Expressing and presenting the protein directly in the cell allowed us to present the extracellular epitope while maintaining its native conformation.

Measurements were performed using Surface Plasmon Resonance Imaging technology (Horiba XelPlex).

Biochip Functionalization

The biochip was modified using a classical amine coupling strategy. Briefly, a –COOH terminated surface was activated using EDC/NHS leading to a reactive sulfo-NHS ester. This intermediate is known to react with primary amine to form a stable amide linkage.
2 anti-X antibody deposition methods were further tested in order to determine the optimal spotting approach (details provided in the PDF file).

Study Of The Antibody-cell Interaction Specificity

X protein cells specific binding was tested by comparing the kinetic curves obtained by injecting X protein cells and control cells (293T cells transfected by an empty plasmide) over an anti-protein X antibody modified biochip.

SPRi antibody cell interaction measurement example

Comparison of X protein cell and control cell injections on the anti-protein X antibody modified biochip led to clear differences in the kinetic curves whatever the conditions of immobilization.

Therefore, the data obtained demonstrates specific binding of X protein cells to anti-protein X antibody.

Kinetic And Thermodynamic Analysis Of The Antibody-cell Interaction

Kinetic curves were obtained by injecting X protein cells over the anti-X protein antibody modified surface at different concentrations. The deposition method that was chosen is the one that gave best results in the aforementioned study.

Thermodynamic and kinetic antibody cell affinity analysis
Kinetic an thermodynamic parameters Kinetic an thermodynamic parameters Kinetic an thermodynamic parameters
ka(M-1.s-1) kd (s-1) KD (M)
Anti-X protein / X protein cells 1.00.1010 2.46.10-4 2.46.10-14


Specific binding of X protein cells to the anti-X protein antibody was demonstrated by SPRi.
SPRi signals allowed the measurement of a low apparent KD which can be interpreted as high affinity antibody-cell interaction. This binding affinity is mainly governed by a high association rate (ka). The multiplexing configuration of SPRi allowed immobilizing the anti-X protein antibody on a same biochip with the two different immobilization methods and at four different concentrations for each immobilization method. During this experiment, 8 different experimental conditions were tested and 282 different sensorgrams were generated in a single biochip.

Click on the button below to get the complete report “Binding study between an anti-X protein antibody and the X protein expressed at the surface of 293T cells by Surface Plasmon Resonance imaging (SPRi) technology”

Case study 2: antibody KD study via Biacore analysis

Aim Of The Study

We were requested by a customer to measure the KD of an antibody/antigen interaction via Biacore. The project dealt with the affinity ranking of 5 different antibodies against a same antigen.

Experimental Setup

Antigen was immobilized on the dextran coated biochip surface via classical maleimide chemistry leading to stable covalent thioether bonding. Solutions containing the antibodies at various concentrations were then flown over the antigen. Measurement of the SPR signal at different antibody concentrations allowed the determination of the kinetics parameters (on-rate ka, off-rate kd) and thermodynamic parameters (KD).

Antibody Affinity Measurement

Antigen Antibody interaction measurement
Antibody ka (1/Ms) kd (1/s) KD (M)
A 4.30×104 2.24×10-4 5.21×10-9
B 1.26×105 9.08×10-4 7.23×10-9
C 6.71×105 3.85×10-4 5.73×10-10
D 6.71×105 4.03×10-4 1.59×10-9
E 6.71×105 7.97×10-4 3.72×10-9

Antibody affinity ranking can be deduced directly from the antibody KD value as the lower the KD value the higher the affinity of the antibody.

Antibody KD ranking: C<D<E<A<B
Antibody affinity ranking: C>D>E>A>B


Biacore analysis led to the conclusion that all 5 antibodies tested demonstrate high affinity against the antigen with C being the best for various reasons:

  • Lower KD indicative of a strong interaction,
  • Favorable kinetic parameters (fast association rate and low dissociation rate).

Click on the button below to get the complete report “Determination of KD of antibody/antigen interaction via Surface Plasmon Resonance (SPR) technology (Biacore X100)”