Exchange dynamics between amphiphilic block copolymers and lipidic membranes through hydrophobic pyrene probe transfer.

Vectorization has experienced significant development over the last few years and has been used to control the distribution of active ingredients to a target by their association with a vector. However, controlled drug delivery suffers from "burst release" as the drugs are released before the targeted site. Very few studies have examined the collective mechanisms of fission-fusion on micelles in the transport and expulsion of active ingredients. Endocytosis and exocytosis of cells are examples of fusion and fission in biological matter. Understanding these dynamics becomes crucial for the design and the control of new materials and new processes effective in controlled drug delivery. In this work, a study of the exchange dynamics between amphiphilic block copolymers and lipid membranes for vectorization of hydrophobic molecules using a fluorescence technique is presented. A highly hydrophobic alkylated pyrene, PyC 18 , is used as a fluorescent probe that can be exchanged between amphiphilic block copolymer micelles and liposomes via different mechanisms. It is demonstrated that the exchange dynamics evaluated for different liposome concentrations is a collective mechanism characterized by having two rate constants.