(441h) Versatile Cholesterol-Functionalized Block Copolymers in Aqueous Dispersions

Cholesterol plays an important role in many biological processes, namely regulating the mechanical and transport properties of biomembranes. Biotechnology research attempts to exploit the inherent benefits of cholesterol through its use, for example, in liposomes for drug delivery. The potential applicability of cholesterol can be further extended through its chemical incorporation into random and block copolymers. The controlled segregation of cholesteryl moieties into one or more portions (i.e. blocks) of a copolymer produces well-controlled nanostructures (micelles and polymersomes) through self-assembly. Here, we first present the self-assembly behavior for a set of novel cholesteryl block copolymers, poly[(ethylene glycol)-b-(cholesteryl 2-oxo-1,3,6-dioxazocane-6-carboxylate)] (PEG-b-P(8C-Chol)), which have relatively short P(8C-Chol) block lengths and therefore are directly dispersible in water. The results provide a relation between the number of cholesteryl groups per polymer chain (X_n,Chol) and the size and geometry of structures formed. Next, we combine the same PEG-b-P(8C-Chol) copolymers in a minority fraction (~5 mol%) with a common phospholipid in order to form surface-functionalized liposomes varying in insertion moieties per copolymer chain (via X_n,Chol). Again, the major implications relate the molecular structure to the self-assembly behavior. Both studies provide overarching design rules regarding cholesteryl-containing block copolymers and could have a major impact in the future synthesis of drug delivery devices and other naoncarriers that utilize cholesterol.