Effects of Individual Amino Acids on the Blood Circulation of Biosynthetic Protein Nanocages: Toward Guidance on Surface Engineering.

Abstract

Protein nanocages (PNCs) hold great promise for developing multifunctional nanomedicines. Long blood circulation is a key requirement of PNCs for most in vivo application scenarios. In addition to the classical PEGylation strategy, short peptides with a specific sequence screened via phage display are also very effective in prolonging the blood half-life (t1/2 ) of PNCs. However, there is a lack of knowledge on how individual amino acids affect the circulation of PNCs. Here the effects of the 20 proteinogenic amino acids in the form of an X3 or X5 tag (X represents an amino acid) are explored on the pharmacokinetics of PNCs, which lead to the formation of a heatmap illustrating the extent of t1/2 prolongation by each proteinogenic amino acid. Significantly, oligo-lysine and oligo-arginine can effectively prolong the t1/2 of strongly negatively charged PNCs through charge neutralization, while oligo-cysteine can also do so, but via a different mechanism, mediating the covalent binding of PNCs with plasma albumin as a stealth material. These findings are extendible and offer guidance for surface-engineering biosynthetic PNCs and other nanoparticles.