Reduction of Irreversible Protein Adsorption on Solid Surfaces by ProteinEngineering for IncreasedStability*

Martin Karlsson, Johan Ekeroth, Hans Elwing, Uno Carlsson

The influence of protein stability on the adsorption and desorption behavior to surfaces with fundamentally different properties (negatively charged, positively charged, hydrophilic, and hydrophobic) was examined by surface plasmon resonance measurements. Three engineered variants of human carbonic anhydrase II were used that have unchanged surface properties but large differences in stability. The orientation and conformational state of the adsorbed protein could be elucidated by taking all of the following properties of the protein variants into account: stability, unfolding, adsorption, and desorption behavior. Regardless of the nature of the surface, there were correlation between (i) the protein stability and kinetics of adsorption, with an increased amplitude of the first kinetic phase of adsorption with increasing stability; (ii) the protein stability and the extent of maximally adsorbed protein to the actual surface, with an increased amount of adsorbed protein with increasing stability; (iii) the protein stability and the amount of protein desorbed upon washing with buffer, with an increased elutability of the adsorbed protein with increased stability. All of the above correlations could be explained by the rate of denaturation and the conformational state of the adsorbed protein. In conclusion, protein engineering for increased stability can be used as a strategy to decrease irreversible adsorption on surfaces at a liquid-solid interface.