Assembly of amphiphilic poly[2‐(methacryloyloxy)ethyl phosphorylcholine] with cholesteryl moieties as terminal groups

Abstract

AbstractPoly[2‐(methacryloyloxy)ethyl phosphorylcholine]s (PMPCs) with one pendant cholesteryl moiety at the polymer end (PMPC‐Chol‐I and PMPC‐Chol‐II) and two pendant cholesteryl moieties at both polymer ends as terminal groups (PMPC‐2Chol‐I and PMPC‐2Chol‐II) were prepared by the radical polymerization of 2‐(methacryloyloxy)ethyl phosphorylcholine initiated with 4,4′‐azobis[(3‐cholesteryl)‐4‐cyanopentanoate] in the presence of 2‐mercaptoethanol or thiocholesterol as chain‐transfer reagents, respectively. The self‐organization of PMPC‐Chol and PMPC‐2Chol was analyzed with fluorescence and 1H NMR measurements. The critical micelle concentrations of PMPC‐Chol‐I with a degree of polymerization (Pn) of 91 and of PMPC‐2Chol‐I with a Pn value of 165 were 250 and 27 mg L−1, respectively. The blood compatibility of PMPC‐2Chol was evaluated from the Michaelis constant (Km) for the enzymatic reaction of thrombin and a synthetic substrate, S‐2238, in the presence of PMPC‐2Chol. Km was 0.07, 0.05, and 0.56 for PMPC‐2Chol‐I with Pn = 165, PMPC‐2Chol‐II with Pn = 38, and PMPC (an intrinsic viscosity of 0.54 dL g−1) initiated with 2,2′‐azobisisobutyronnitrile in the absence of chain transfer agent, respectively. A mixture of PMPC‐2Chol‐II and cholesterol as a drug model formed a lamellar type of complex with an interplanar spacing of d = 35.2 Å. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1992–2000, 2003