Our Technology

Bullet Capsid Platform

Bullet Capsids are hollow, non-infectious nanoparticles made from proteins. The capsids are essentially spheres that are the same shape and size as a virus. Advantages include:

  • Modular, easy to customize. We have developed multiple methods for site-specific conjugation of proteins, oligonucleotides, and small molecules.

  • Novel products. Components in new product are covalently bound, with potential for composition of matter patent protection

  • Nanoparticle size advantages. The Bullet Capsid is <50 nanometers in size, ideal for biodistribution in tumor microenvironment

  • 3D structure advantage. The three-dimensional structure displays components on the surface of the Bullet Capsid in an ordered array, simultaneously stimulating multiple receptors and thereby generating a stronger response.

  • Bullet Capsids are manufactured using scalable bacterial protein production. Bullet Bio also has developed purification and release testing assays to ensure product quality.

    Bullet Capsid


    • Lu et al. (2015).  Assessing sequence plasticity of a virus-like nanoparticle by evolution toward a versatile scaffold for vaccines and drug delivery. PNAS 112: 12360-12365.
    • Cubas et al. (2009). Virus-like particle (VLP) Lymphatic Trafficking and Immune Response Generation after Immunization by Different Routes. J Immunother,. 32(2): 118–128.
    • Whitacre et al. (2009). Use of hepadnavirus core proteins as vaccine platforms. Expert Rev Vaccines, 8(11): 1565-73.
    • Patel, K.G. and J.R. Swartz (2011). Surface functionalization of virus-like particles by direct conjugation using azide-alkyne click chemistry. Bioconjug Chem, 22(3): p. 376-87. 
    Partnership Opportunities