Binding affinities/avidities of antibody-antigen interactions: quantification and scale-up implications

Area of Science:

• Biophysical chemistry
• Cell biology
• Biotechnology

Background:

• Bioaffinity interactions are vital for separation and detection technologies.
• Cell labeling with antibody-magnetic nanoparticle conjugates exhibits saturation kinetics.
• Existing methods lack precise quantification of cell-surface antibody binding parameters.

Purpose of the Study:

• To develop a model for determining apparent dissociation constant and antibody-binding capacity (ABC) of cells.
• To incorporate multi-valence interactions and flow cytometry/cell tracking velocimetry (CTV) data.
• To evaluate the model's scalability for clinical applications.

Main Methods:

• Developed a model based on antibody-antigen interactions, considering multi-valence.
• Integrated flow cytometry (FCM) and cell tracking velocimetry (CTV) measurements.
• Tested the model on peripheral blood lymphocytes (PBLs) labeled with anti-CD3 antibodies conjugated to nanoparticles.

Main Results:

• The model achieved reasonable agreement with experimental data for PBLs.
• Steric hindrance effects on nanoparticle binding were consistent with magnetophoretic mobility measurements.
• A scale-up model successfully predicted conjugate requirements for large cell numbers (10^10).

Conclusions:

• The developed model accurately quantifies cell-surface antibody binding parameters.
• The findings support the use of bioaffinity interactions for cell analysis and large-scale cell processing.
• This approach has potential applications in clinical settings, such as T-cell depletions.