Analysis of Operating Conditions for Commercially Available Depth Filters

Open Access
- Author:
- Dyke, Kevin
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Andrew Zydney, Thesis Supervisor
Ali Borhan, Thesis Honors Advisor - Keywords:
- Depth Filtration
- Abstract:
- Depth filtration is used extensively for the purification of biological products. There are many commercially available depth filters that exploit differences in size and intermolecular interactions to achieve important separations. However, there is currently a lack of understanding of how these depth filters perform under a wide range of operating conditions. The objective of this thesis is to evaluate the performance of several commercial depth filters with the goal of understanding how these depth filters might be used more effectively to purify biological products made using Chinese hamster ovary (CHO) cells. Experiments were performed using a series of model proteins with the A1HC, D0SP, and X0SP depth filters manufactured by Millipore Sigma. Protein concentrations were evaluated using a spectrophotometer based on UV absorbance measurements or the Bradford assay. These studies showed that the solution pH and protein isoelectric point (pI) have little effect on the binding capacity of the A1HC filter, suggesting that this filter binds protein primarily through hydrophobic interactions, while increasing protein pI at acidic conditions significantly increases the binding capacity of the X0SP and D0SP filters, both of which appear to bind proteins primarily through electrostatic interactions. It was also found that flow rate does not impact the binding capacity of the A1HC, and that actual host cell proteins (HCP) from CHO cells can be effectively removed by these depth filters. These results provide important insights into the performance characteristics of these depth filters and how they can be used more effectively for depth filtration processes.