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Determination of Full and Empty Adeno-Associated Virus Capsid Ratio by Capillary Isoelectric Focusing (CAT#: STEM-ET-0354-ZJF)

Introduction

Adeno-associated virus (AAV) is one of the most promising gene transfer vector types featuring long-term gene expression and low toxicity. The lack of pathogenicity and the availability of many serotypes augmented the applicability of AAV virions in gene therapy applications. The recombinant AAV capsid includes the therapeutic protein-coding transgene as well as a promoter to initiate translation and a poly A sequence portion for stabilization. Current AAV manufacturing technologies, however, cannot guarantee the generation of only full capsids, i.e., including the entire required genome. Partially filled and empty capsids are also part of the product, decreasing in this way the efficacy and safety upon clinical translation. Therefore, rapid, accurate and QC friendly analysis of the full and empty capsid ratio is of high importance during AAV vector manufacturing and release testing. This service provides an automated capillary isoelectric focusing technique applicable in the biopharmaceutical industry for fast and efficient determination of the full and empty capsid ratio.




Principle

Isoelectric focusing (IEF) is a method of electrophoresis that separates proteins according to their isoelectric point. It performs in a particular pH gradient, in which proteins are separated by differences in their isoelectric points. The isoelectric point (pI) is the pH at which the net charge of the protein is zero. Protein is positively charged when its pI is above the solution's pH, so it migrates towards the cathode. Conversely, protein is negatively charged when its pI is below the solution's pH, so it migrates towards the anode. Protein has no net charge at its pl and stops migrating. Based on this principle, proteins can be separated into sharp bands with each protein positioned at a point in the pH gradient corresponding to its pI.

Applications

Adeno Associated Virus, Full/empty capsid, Molecular medicine, Biopharmaceutics

Procedure

1. Preparation: Prepare the gel containing the sample. Mix the solution and add it to a glass tube to form a gel. Prepare the fixing solution, dyeing solution and decolorization solution.
2. Electrophoresis: Add the appropriate acidic solution in the positive electrophoresis tank, and the appropriate alkaline solution in the negative electrophoresis tank. Switch on the electrophoresis apparatus and set the voltage and current. Perform pre-electrophoresis for a period of time to form a pH gradient in the gel. Then set the electrophoresis apparatus to a higher voltage and perform electrophoresis for a period of time.
3. Determination: Different protein components focus on the corresponding pI. Fix, stain and decolorize the gel. Finally, dry it for storage.

Materials

• Isoelectric focusing apparatus
• Sample solution
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