Utilization of surface energetics approach to Understand protein interaction to ceramic hydroxyapatite
Correspondence to: Dr Marcelo Fernández-Lahore, Downstream BioProcessing Laboratory, Jacobs University, Campus Ring 1, D-28759 Bremen, Germany. E-mail: email@example.com
A surface thermodynamics approach can be utilized to understand protein interaction during adsorption chromatography. Ceramic hydroxyapatite has been widely used in the purification of biomolecules during downstream bio-processing. Protein interaction with this adsorbent is a complicated process.
In this work, interaction between model proteins and an adsorbent (ceramic hydroxyapatite Type I) was studied via extended DLVO (Derjaguin, Landau, Verwey and Overbeek) theory. The surface energy parameters of proteins and adsorbent were determined from experimental contact angle and zeta potential values. In ceramic hydroxyapatite chromatography, protein adsorption takes place under mixed mode conditions i.e. cationic exchange and calcium chelation. The sample is loaded in low salt and eluted at increasing phosphate gradient. The XDLVO approach calculated the free energy of interaction as a function of distance, between the interacting surfaces under de-binding conditions. The calculated interaction energy of the model proteins with CHT were correlated with the actual elution behavior. This revealed that all the proteins show minimum binding energies, i.e. |0.005| ± 0.002 kT under the observed conditions. These energy values are considered to be a cutoff between retaining and non-retaining conditions. Higher energy values will explain binding and lower energies will explain elution (binding > |0.005| kT > elution).
Knowledge generated from these studies will assist understanding of adsorption of proteins to the process supports which could facilitate better bioprocess design and optimization. © 2013 Society of Chemical Industry