Separation of Peptides and Interaction with Forward Osmosis Biomimetic Membranes: A Solution Diffusion Model

Abstract

Recently, a membrane based technique, forward osmosis (FO), has gained interest with respect to the separation and purification of biomolecules. Forward osmosis relies on concentration gradients to draw water across the membrane and is as such a gentle technique compared to the traditional pressure driven membrane processes. The challenge within FO is to operate at a high water flux while maintaining a high rejection and low reverse flux of salt that may otherwise interfere with the biomolecules. By adding water-transporting aquaporin protein channels to the membrane matrix to create biomimetic membranes, selective transport of water is possible. These kinds of membranes could as such be ideal for separation of biomolecules.In this study, a biomimetic forward osmosis membrane was tested for the separation of two peptides (416.48 Da and 691.71 Da). The membrane was found to exhibit high, but not complete, rejection rates of both peptides (>98%). It is interesting that even relatively large molecules are able to pass the otherwise dense active layer of the forward osmosis membrane. Therefore, to further understand the transport mechanisms underlying the filtration process, a custom made cell was constructed and used to model the process with filtration models. It was found that the filtration process could be modeled using the solution diffusion approach, with the diffusion coefficient being related to the radius of gyration of the peptides.