Gene therapies correct genetic disorders by replacing missing or defective genes through transplantation of a functional gene into patient cells. Adeno-associated virus (AAV) vectors (AAV cassettes or capsids) are commonly used as the delivery system for these therapies. With the development of gene therapy, there is now a mounting pressure to demonstrate potency, safety, and purity while keeping pace with high demand and tight timelines. There is no room for error. Empty or partially filled capsids are not just inefficiencies, they can trigger immune responses, reduce efficacy, and risk product rejection by regulators. The Eurofins BioPharma Product Testing network of laboratories delivers a comprehensive, GMP-compliant service for the characterisation of AAV capsid populations, ensuring your gene therapy meets regulatory expectations and performs as intended. 

Inconsistency in AAV preparations during manufacturing processes leads to product heterogeneity and negatively affects the gene delivery. Our testing support, ensures the potency, purity, and safety of your AAV-based gene therapy. With a wealth of experience and scientific expertise, our teams deploy a suite of state-of-the-art analytical methods including:

• AUC (Analytical UltraCentrifugation)
• TEM (Transmission Electron Microscopy)
• SEC-MALS (Size-Exclusion Chromatography with Multi-Angle Light Scattering)
• Mass Photometry

Each of these technologies offers distinct advantages for detecting and quantifying empty, full, and partially filled capsids. Our experts will recommend the most suitable option to meet your development stage, regulatory context, and therapeutic profile.

Mass Photometry, one of the most recent additions to our toolkit, is a revolutionary, label-free technique that can measure the precise mass of single AAV particles, making it ideal for rapid, accurate characterisation of capsid ratios without extensive sample preparation. And the good news is: in 2025, USP has released new standards for measuring AAV full and empty capsids using 6 different methods, including mass photometry.

Determining the ratio of empty/full capsids of the vector product is a critical quality requirement for the AAV production process. We understand the critical nature of these analyses. That’s why our services are performed under strict GMP conditions and backed by deep regulatory insight, as directed by FDA/EMA guidelines.