Measuring the interaction forces between protein inclusion bodies and an air bubble using an atomic force microscope

Area of Science:

• Biophysics
• Biotechnology
• Surface Science

Background:

• Protein inclusion bodies are aggregates often found in recombinant protein production.
• Understanding their surface interactions is crucial for downstream processing, like separation.
• Flotation is a potential method for recovering these inclusion bodies.

Purpose of the Study:

• To quantify interaction forces between protein inclusion bodies and an air bubble.
• To investigate the influence of pH and ionic strength on these forces.
• To assess the applicability of Atomic Force Microscopy (AFM) for designing separation processes.

Main Methods:

• Utilized Atomic Force Microscopy (AFM) to measure forces.
• Attached protein inclusion bodies to the AFM tip via covalent bonds.
• Performed measurements in varying buffer concentrations and pH levels.

Main Results:

• Measured interaction forces ranged from 9.7 nN to 25.3 nN.
• Hydrophobic forces were found to be more significant than electrostatic double layer forces.
• The effect of pH on inclusion bodies was more pronounced than on air bubbles.
• Ionic strength's effect was complex and not fully explained by DLVO theory.

Conclusions:

• Fundamental data on protein inclusion body-air bubble interactions were obtained.
• AFM is a valuable tool for understanding and designing bioprocess separations.
• Findings facilitate the rational design of flotation recovery systems for inclusion bodies.