Assessing Gene & Drug Encapsulation using Cryo-TEM
Many drugs have poor solubility or low absorption rates and are susceptible to degradation, chemical reactions, or rapid clearance when administered directly. Encapsulation within nanoparticles can enhance drug solubility and provides protection to the drug of interest, improving drug stability, absorption, bioavailability, and therapeutic efficacy. In addition, drug delivery vehicles can be designed to release the encapsulated drug in a controlled manner and selectively target specific cells, maintaining therapeutic levels and reducing toxicity.
Encapsulation assessment can be done on the following particles:
- Virus-like Particle (VLP), including AAV, capsids
- Liposomal drug encapsulation
- Lipid Nanoparticle (LNP) payload
In general, the manufacturing process and maintaining product shelf-life of therapeutics is not without challenges. Sub-optimal conditions, such as introduction of contaminants, shear stress, freeze-thaw, light exposure etc. can affect the product’s quality attributes and can not only result in formulations that contain impurities, particles that are misassembled, have lost their integrity, or show aggregation, it can also result in formulations that contain (too many) nanoparticles without payload. The number of empty delivery vehicles influences the concentration of the therapeutic agent delivered, and hence, its efficacy and safety. Therefore, characterizing the gene or drug encapsulation – or more adequately the drug loading fraction – of nanoparticles in a formulation is imperative.
Cryo-TEM offers significant advantages despite requiring specialized equipment and expertise. It enables for direct visualization of the presence and location of encapsulated payload within the delivery vehicle at a per-particle basis (complementing bulk-based measurements obtained using orthogonal techniques such as dynamic light scattering (DLS), spectroscopic methods, or fluorescence-based assays. Another huge advantage of cryo-TEM is that multiple quality attributes can be evaluated simultaneously; in addition to assessing gene or drug encapsulation, purity, aggregation, integrity, morphology, and size distribution can all be characterized using the same cryo-TEM image set. A few examples of assessing drug and gene encapsulation or loading fraction are described here.
- Virus-Like Particles (VLPs)
- Associated Adeno-Virus (AAV) Characterization
- Hepatitis B Virus (HBV ) Characterization
- Human Papillomavirus (HPV) Characterization
- Lentivirus Characterization