Rheological characteristics and diffusion processes in mixed cellulose hydrogel matrices

A rheological Maxwell model was used for studying theoretically the kinetics of water penetration and molsidomine release from mixed hydroxypropylmethyl cellulose/carboxymethylcellulose-Na (HPMC/NaCMC) hydrogel matrices in 0.1 mol.dm-3 HCl and pH 6.8 phosphate buffer. Using the modeling, the characteristic mean relaxation time, zero-relaxation time and secondary plateau moduli were calculated and their values were related to the kinetic constants of water penetration and drug release. For the elastic cellulose gels, a statistically significant relationship between the rheological parameters and the kinetic constants was observed. The enhanced elasticity and quick relaxation of the neutralized NaCMC and HPMC/NaCMC matrices resulted in a higher degree of hydration, a faster penetration front movement and increased drug release rate. In the case of the plastic ionized gels, the looser structure, the low viscosity and the quick relaxation determined the considerable degree of swelling, the faster gel surface dissolution and the observed erosion-controlled release mechanism. The results demonstrated that the rheological and relaxation analysis of the swollen gel matrices could be used for forecasting drug release processes.