Effect of poly lactic-co-glycolic acid encapsulation on drug delivery kinetics from vancomycin-impregnated Ca-Mg silicate scaffolds

Abstract

The identification of drug delivery mechanisms is critical to design a device that offers a drug release kinetics within the therapeutic window. In this paper, the drug release kinetics of bioresorbable tissue engineering scaffolds coated/uncoated with biodegradable polymer layers is studied. Interconnectedly porous bredigite (MgCa7Si4O16) scaffolds were fabricated by a sacrificial urethane foam replica method, loaded with vancomycin hydrochloride (C66H75Cl2N9O24) and then encapsulated in poly lactic-co-glycolic acid (PLGA, LA/GA = 50:50) coatings of two different thicknesses. Field-emission scanning electron microscopy (FESEM) and Fourier-transform infrared spectroscopy (FTIR) were used to verify the macroporous morphology and chemical constituents of the devices. The release profiles of vancomycin from these systems into phosphate buffered saline (PBS) at 37 °C were also recorded by ultraviolet-visible (UV–vis) spectroscopy. To explore the dominant drug delivery mechanisms, the experimental data of the drug release was then fitted with several drug delivery mathematical models, including the Higuchi, Hixson-Crowell, Korsmeyer-Peppas, Peppas-Sahlin, Weibull, zero-order and first-order. Comparing the correlation coefficient of the regressions as a measure of goodness-of-fit, it was found that vancomycin release from the bare scaffold is subjected to a dissolution-controlled kinetics, whereas the PLGA-coated scaffolds mainly display a combination of diffusion- and dissolution-controlled mechanisms for the drug release. It can be accordingly concluded that the bredigite scaffolds are a versatile device for different local drug delivery strategies offering rapid, single-stage and dissolution-controlled release kinetics that can be easily modulated into a diffusion-controlled, biphasic and prolonged release through biopolymer coating.