Separation of virus-like particles and nano-emulsions for vaccine development by Capillary Zone Electrophoresis

Introduction

• Vaccine formulations increasingly incorporate virus-like particles (VLPs) along with nano-emulsion adjuvants to boost immune responses. However, analytically characterising these mixtures is very difficult because both components are heterogeneous nano-species of similar sizes but with distinctly different physicochemical properties.

• Traditional separation methods like Size Exclusion Chromatography (SEC) and Field-Flow Fractionation (FFF) often fail to differentiate VLPs from adjuvant emulsions due to overlapping size ranges. Likewise, light scattering techniques become unreliable in mixed systems where surfactants obscure particle surface characteristics.

• This innovative study shows that Capillary Zone Electrophoresis (CZE) – which separates based on charge-to-size ratio rather than size alone – can concurrently quantify Human Papillomavirus VLPs and squalene nano-emulsion adjuvants within a single run, requiring only simple dilution.

• The method demonstrated ICH Q2-compliant performance with 87-109% accuracy and ≤20% precision, also measuring buffer excipients like chloride and histidine. This creates a versatile platform suitable for various vaccine-adjuvant combinations and nanoparticle-based pharmaceutical systems.

Key Learning Outcomes

• Understand the advantages of charge-to-size ratio separation mechanisms over size-based methods when analysing complex vaccine formulations with multiple nano-species that have overlapping physical dimensions but different electrokinetic properties.

• Explore systematic strategies for developing CZE methods suitable for challenging nanoparticle systems, including selecting capillary coatings like PDADMAC, optimising background electrolytes for pH and ionic strength, and using buffer additives such as polyethylene oxide to prevent non-specific adsorption and particle aggregation.

• Acquire practical insights into overcoming common CE issues with biological nanoparticles, such as reducing silanol group interactions, minimising peak tailing through surface modifications, and ensuring particle stability during separation.

• Recognise how a single CZE method can enable multi-analyte characterisation across vastly different molecular scales – simultaneously measuring nanoparticles (VLPs and emulsions), polymers (surfactants), small molecules, and ions – providing a comprehensive approach to formulation analysis in pharmaceutical development.

About

Dr. Adam T. Sutton is a Senior Scientist in Analytical Research and Development at Merck Research Labs, where he specialises in developing advanced analytical characterisation methods for vaccine products. Holding a Ph.D. in Analytical Chemistry from the University of South Australia, he has extensive expertise in separation science and method development to tackle the complex analytical challenges of next-generation vaccine modalities. His research emphasizes innovative approaches for characterising difficult formulations, especially those combining multiple nano-scale components like virus-like particles and adjuvant systems. At Merck, Dr. Sutton’s work supports vaccine development by establishing robust, ICH-compliant analytical methods that facilitate thorough quality assessment of new formulations. His work demonstrates how modern electrophoretic techniques can overcome traditional nanoparticle analysis limitations, offering practical tools for multi-component analysis. His collaborative style and dedication to creating transferable, user-friendly methods help speed up vaccine development while maintaining high-quality standards across the pharmaceutical industry.