Alkyl chain grafted poly(l-lysine): Self-assembly and biomedical application as carriers

The synthesis and self-assembly of amphiphilic copolypeptides, poly(l-lysine)-graft-hexanoyl (PLH), and their evaluation as carriers/encapsulants for myoglobin (Mb) encapsulation have been investigated. The interplay between the hydrophobic interaction and the chain conformational changes upon hexanoyl substitution determined the self-assembly behavior of PLH, which further influenced the evolution of the assembled nanostructures. The experimental data revealed that vesicles with mean sizes between 100 and 500 nm were formed by these amphiphilic copolypeptides in acidic and neutral aqueous solution. The hexanoyl substitution can regulate the hydrophobic interaction, chain conformation of PLH, and subsequently the size of the assembled vesicles at different pH. Taking advantage of the self-assembly capability, the PLH was employed for protein encapsulation, i.e. myoglobin (Mb). The encapsulation efficiency was higher than 50% and the encapsulated protein was still capable of carrying oxygen, which demonstrated that the PLH vesicles are promising carriers or encapsulants. The Mb-loaded PLH particles were further crosslinked by genipin to form stable nanostructures with mean sizes between 180 and 280 nm. The as-prepared particles were found to be well suspended in solution for months. With versatility of this synthesis strategy, additional functionality can be incorporated on PLH, which can allow these amphiphilic copolypeptides to be useful as targeted drug carriers, biomimetic encapsulants, and functional nanobioreactors in the biomedical fields.