Polyelectrolytes as Drug Carriers. Analysis by Dynamic Light Scattering of Reconstituted and Prepared Model Polymethacrylate-Drug Aqueous Dispersions

ABSTRACT

This article reports dynamic light scattering (DLS) data, and electrokinetic ζ-potentials of aqueous dispersions of two linear flexible polymethacrylic acid derivatives Eudragit® L100 (EuL) and S100 (EuS) loaded with two model drugs (D), lidocaine (Ld) and atenolol (At). Dispersions of EuL and EuS at 1,0 % neutralized with increasing percentages (50, 75 and 100 mole %) of each D exhibited a unimodal scattering distribution rendering diffusion coefficients (DC) in the interval of 4 to 9. 10^-9 cm²/s. All dispersions 50% neutralized exhibited quite similar DC. However, the effect of increasing neutralization followed a different pattern in each Eudragit® . All dispersions exhibited high negative ζ-potentials that were lower at 100% with respect to 50% loading. Both, DC and ζ-potentials, of redispersed lyophilized samples of (EuL-D) and (EuS-D) remained identical to those of in situ prepared while those of analog samples prepared by solvent evaporation exhibited some slight differences. The behavior of (EuL-D) and (EuS-D) systems examined here through DLS appears to be quite similar to that reported for polyelectrolytes neutralized with monovalent inorganic cations. Last, it has been shown that DLS provides valuable information about the reversibility from solid to dispersion states of these nanometric drug carrier systems.