The Formation of Vesicles through the Modification of Tyrosine-Derived ABA Tri-Block Copolymer Membranes

Amphiphilic ABA triblock copolymers are studied as a promising biomimetic substitute for lipids that form vesicles, a nano-scale morphology that is used as a carrier for drug delivery. The hydrodynamics of the tyrosine-derived PEG-b-oligo(desaminotyrosyl tyrosine octyl ester-suberate)-b-PEG (PEG-oligo(DTO-SA)-PEG) was investigated using dissipative particle dynamics (DPD) simulation techniques. This technique is a coarse-grained (CG) molecular dynamics-based approach that uses soft repulsive interactions between beads that represent clusters of atoms or molecules. Computational results have shown that this polymer membrane forms a disk-shaped micelle only. Therefore, by inserting polymers that are folded 180 degrees throughout the membrane, we have modified the polymer membrane so that other morphologies are formed, namely vesicles. Varying chain lengths of both hydrophobic and hydrophilic segments have been shown to demonstrate different morphologies of this ABA triblock copolymer. For chain length combinations that form vesicles, the radius of the vesicle and the angle distribution of the polymers were computationally calculated and graphed based on the trajectory files from the simulations. These results show a strong linear relationship between the chain lengths and vesicle size. We also propose potential experimental applications of these results, which could demonstrate that these simulations can be observed in a laboratory setting.