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What size are cell and gene therapies?

Have you ever given much thought to the relative size of the biological materials you work with every day in the lab? It can be mind-boggling to think about how something as tiny as a viral particle can have a life-saving impact for a patient with a debilitating genetic disease when delivered en masse. 

But exactly how small of a package is all that life-changing power packed within?

Quick! Put the following biologics in order from smallest to largest–no Googling!

  • Transfection complexes
  • T cells
  • Lentivirus
  • AAV

Anyone get it right on the first try? Though it may not be surprising that the viruses are the smallest of the particles listed here, did you know how large transfection complexes can be (Table 1)?

There are many variables that influence the size of transfection complexes, including complex formation time, the solution the complex is formed in and of course, the transfection reagent. (Read this blog post for more details on the variables that affect transfection complex formation.)


Table 1. Approximate diameter of particles and cells in nanometers

T Cell 


Some transfection complexes are even visible to our human eyes through a microscope depending on their size. The next time you find yourself performing a transfection, try to scope them out and be amazed at all the power in that tiny particle!

Explore Related Info & Links

  • Learn about transfection reagents for cell and gene therapy here
  • FAQ – What is the difference between transfection and transduction?
  • FAQ – How can I increase my viral titers and improve the percentage of full AAVs?
  • What kind of virus was being studied when the word ‘transfection’ was first used (1964)? Answer here.

The TransMission
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