Sterile Filtration Of Large Particle Therapeutics - New Insights Using A Live Attenuated Viral Vaccine And A Model Nanoparticle Suspension
Open Access
- Author:
- Taylor, Neil
- Graduate Program:
- Chemical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 15, 2022
- Committee Members:
- Andrew Zydney, Chair & Dissertation Advisor
William Hancock, Outside Unit & Field Member
Themis Matsoukas, Major Field Member
Stephanie Velegol, Major Field Member
Seong H. Kim, Professor in Charge/Director of Graduate Studies - Keywords:
- Sterile Filtration
Live Attenuated Viral Vaccine
Nanoparticles
Pore Size Distribution
Fouling
Prefiltration - Abstract:
- The rapid development of novel vaccines against new and emerging pathogens has become increasingly important due to pressures arising from a growing world population and global climate change. The recent COVID-19 pandemic has been a prime example of how the rapid development of a vaccine can change the course of a pandemic. One particular challenge with large particle vaccines like measles and influenza is the sterile filtration step since the particle size distribution can significantly overlap with the nominal pore size of sterile filters. The resulting decrease in capacity and yield causes a significant increase in the overall cost of manufacturing. The objective of this dissertation was to investigate the factors controlling the transmission and capacity of sterile filters when using a large particle live attenuated cytomegalovirus vaccine (100 - 450 nm in size). Initial experiments carried out by Merck & Co., Inc., Kenilworth, NJ, USA showed significant variability in both the transmission and capacity of different commercial sterile filters with the live-attenuated cytomegalovirus vaccine (LAV). There were no apparent correlations between sterile filter chemistry, morphology (asymmetric vs symmetric), or structure (with / without prefilter). The Sartobran P dual layer filter was able to achieve 80% LAV transmission with capacities >100 L/m2. A model suspension was developed using fluorescent polystyrene latex particles plus 0.01% Tween 20 to further investigate the factors controlling particle transmission and capacity. The behavior of the model suspension was in good agreement with the LAV, capturing the observed differences in transmission and capacity between filters as well as the effects of filtrate flux and feed concentration on the filtration performance. Porosimetry techniques were used to determine the detailed pore size distributions of the different sterile filters. A strong correlation was observed between the average pore size of the sterile filter determined by mercury intrusion porosimetry and the maximum particle transmission. Dual-layer sterile filters tended to outperform single layer filters due to removal of aggregates and larger particles by the prefilter, an effect that was quantified using nanoparticle tracking analysis. The sterile filter performance was also a function of electrostatic and hydrophobic interactions between the particles and membrane. The transmission increased with decreasing ionic strength due to the greater electrostatic repulsion. A new method was developed to determine the hydrophobicity of these large nanoparticles using a hydrophilic 5.0 um Durapore membrane as the stationary phase. The long-range hydrophobic interactions led to particle binding and a reduction in sterile filter performance. Detailed studies showed complete retention of Brevundimonas diminuta bacteria by the Sartobran P under all experimental conditions, demonstrating the robustness of these filters in meeting the stringent requirements for production of sterile vaccine products. Overall, this dissertation has provided fundamental insights into the factors controlling the transmission and capacity of sterile filters facilitating the design of new sterile filters and providing the groundwork on how large particle biotherapeutics can be processed by appropriately designed sterile filters.