Estimating and leveraging protein diffusion on ion-exchange resin surfaces

Area of Science:

• Biochemistry
• Chemical Engineering
• Materials Science

Background:

• Protein mobility at interfaces impacts bioseparation and biosensor performance.
• Slow mass transfer in ion-exchange chromatography limits resin capacity utilization.
• Surface diffusion is often overlooked in small, tortuous pores.

Purpose of the Study:

• To demonstrate how accounting for protein surface diffusion can alleviate mass-transfer limitations.
• To investigate the factors influencing protein surface diffusivity.
• To develop an improved protein-loading strategy based on surface diffusion.

Main Methods:

• Confocal microscopy to characterize protein distribution at micrometer scales.
• Small-angle neutron scattering for nanometer-scale analysis.
• Modulation of binding affinity and ionic strength to control surface diffusivity.

Main Results:

• Protein surface diffusivity depends solely on binding affinity, independent of pH, ionic strength, or ligand density.
• Surface diffusion influences protein distribution within chromatographic resins.
• A gradient loading approach based on modulated binding affinity increased protein uptake efficiency by 43%.

Conclusions:

• Protein surface diffusion is crucial for efficient protein transport in ion-exchange chromatography.
• Exploiting surface diffusion can significantly enhance protein loading and resin capacity.
• This work provides a foundation for optimizing chromatographic processes through surface diffusion control.