Polyoxyethylene-coated nanospheres: effect of coating on zeta potential and phagocytosis

Polylactic acid (PLA) nanospheres coated with monomethoxypolyoxyethylene (M POE) were prepared from amphiphilic diblock copolymers (MPOE-PLA) by an emu lsion-evaporation procedure in the presence of sodium cholate as surfactant . Nanospheres with various concentrations of MPOE at their surface and vari ous MPOE molar masses were obtained by using blends of PLA with different M POE-PLA. The surface properties of these nanospheres were analysed, firstly by measuring the particle zeta potential and secondly by studying their ph agocytosis by monocytes. It was found that the increase in MPOE concentrati on and molar mass provoked a disappearance of the negative charge at the su rface together with a decrease in the extent of phagocytosis. It is conclud ed that the brush of MPOE at the particle surface masks the PLA carboxylate end-groups, lowers the PLA hydrophobic character and, above all, hampers t he approach of the proteins responsible for phagocytosis. (C) 1999 Society of Chemical Industry.