POTENTIAL MODELING OF ACRYLIC-ACID COPOLYMER NANOPARTICLES BY SMALL-ANGLE X-RAY-SCATTERING

Copolymer nanoparticles of acrylic acid, acrylic amide, acrylic butyl acrylate and methyl acrylate were characterised using a parameter rele vant for in vivo organ distribution: charge distribution. Usually the zeta potential is estimated with laser Doppler anemometry as an equiva lent for the particle charge. In our case, the potential distribution was investigated by small angle X-ray scattering. The nanoparticles sh ielded by counter-ions at high ionic strength (0.15 M NaCl solution) h ave short-range potentials. Different potential models were calculated : Percus-Yevick potential and Hypernetted Chain potential. The potenti als estimated by small angle X-ray scattering can be divided into attr active and repulsive parts. The attractive potential, indicated by a m inimum, is not significant compared with the repulsive potential and c an be ignored. Consequently the tendency to form Van der Waals cluster s is low. The solution shows a random order of hard spheres. Therefore , surface charges on the nanoparticles should hamper such carrier cell interaction only at short distances. In comparison with the potential estimation by laser Doppler anemometry (32.8 mV), results of the same order of magnitude were obtained using the small angle X-ray scatteri ng method. The advantage of this method is that it provides a potentia l curve, which allows better appraisal of clearance by the reticuloend othelial system. By interpreting the potential curves, a more detailed prediction of steric stability of particle systems is possible. (C) 1 998 Elsevier Science B.V. All rights reserved.