Heterogeneous Hydrolytic Degradation of Poly(lactic-co-glycolic acid) Microspheres: Mathematical Modeling

BUSATTO, CARLOS; PESOA, J. I.; IGNACIO HEBLING; JULIO LUNA; DIANA ESTENOZ

Congreso; 10th World Congress of Chemical Engineering (WCCE); 2017

A mathematical model to predict the heterogeneous autocatalytic degradation of PLGA microspheres was developed on the basis of a kinetic mechanism that includes the hydrolysis of the different types of ester bonds by random chain scission. The model takes into account the autocatalytic effect of carboxylic groups and polymer composition on the degradation rate and it is based on mass balances for the different species considering the kinetic and mass transport phenomena involved. The model assumes that oligomers species with a chain length up to a critical chain length can be dissolved. Also, in order to quantify the mass transport, the variation of the diffusion coefficient with the weight-average molecular weight is taken into account. The model predicts the following evolutions along degradation: i) radial profile of average molecular weights and molecular weight distributions; ii) mass loss; iii) morphological structure of the particle. In order to validate the model, PLGA microparticles of different sizes were prepared and characterizated, and their degradation in PBS buffer was studied during 28 days. It is shown that polymer degradation becomes more pronounced with increasing microparticle dimension due to autocatalytic effects. The model can be used to study the effect of particle size and molecular weight of the polymer in order to design anappropriate polymeric particle system to achieve a desired degradation time