Indomethacin-containing nanoparticles derived from amphiphilic polynorbornene: A model ROMP-based drug encapsulation system

A series of monodisperse amphiphilic diblock copolymers containing a high-density of covalently linked indomethacin as the hydrophobic block and pendant hexaethylene glycol monomethyl ether as the hydrophilic block have been synthesized from ring-opening metathesis polymerization (ROMP) using Cl-2(PCy3)(2)Ru = CHPh. Dynamic light scattering (DLS), transmission electron microscopy (TEM), and H-1 NMR spectroscopy have been used to investigate the directed-assembly of these polynorbornene-based copolymers into polymeric nanoparticles in aqueous media as a function of copolymer composition, concentration, and degree of polymerization. The block copolymers formed micelle-like aggregates in the aqueous phase with mean diameters ranging from 993 +/- 270 nm to 94 +/- 14 nm by TEM. In general, the aggregate size decreased as the overall copolymer length decreased. After incubation in an acidic environment (PH = 3) at 37 degreesC for 48 h, 20% of the indomethacin was released from the nanoparticles.