Preparation, characterization and cytotoxicity of methylmethacrylate copolymer nanoparticles with a permanent positive surface charge.

Methylmethacrylate copolymer nanoparticles containing different cationic comonomers such as N-trimethylammoniumethylmethacrylate (TMAEMC), N-dimethylammoniumethylmethacrylate (DMAEMC), N-trimethylammoniumpropylmethylacrylamide (MAPTAC) or the anionic comonomer sulfopropylmethacrylate (SPM), respectively, were prepared by free radical polymerization. Particle size was determined by photon correlation spectroscopy (PCS), transmission and scanning electron microscopy (TEM, SEM), and surface charge by microelectrophoresis. Pure poly(methylmethacrylate) nanoparticles served as control. Depending on the method, mean diameters of permanently positively-charged nanoparticles MMA-TMAEMC and MMA-MAPTAC were 243 or 207 nm (PCS), 161 or 201 nm (TEM), and 158 or 197 nm (SEM), respectively. Zeta potential examined in demineralized water or NaCl solution was +63.4 or +32.1 mV for MMA-TMAEMC nanoparticles and +49.2 or +32.0 mV for MMA-MAPTAC nanoparticles, respectively. Cytotoxicity of nanoparticles was determined by MTT assay in three different cell cultures including human foreskin fibroblasts (HFF) and two monkey kidney cell lines MA-104 and Vero. Cell viability profiles of TMAEMC and MAPTAC containing nanoparticles were different, showing IC(50) values for MMA-TMAEMC nanoparticles of 189.6+/-11.4 µg/ml (MA-104), 110.9+/-3.1 µg/ml (Vero) and 27.2+/-4.0 µg/ml (HFF). Cell viability at maximum concentration of 500 µg/ml MMA-MAPTAC nanoparticles was 98.3% (Vero), 85.7% (MA-104), or 94.0% (HFF), respectively.