Lectin-coated PLGA microparticles: thermoresponsive release and in vitro evidence for enhanced cell interaction

PLGA-microparticles with 4.7 μm in diameter were prepared by the double emulsion technique and loaded with 1.7 μg fluorescein/mg PLGA mimicking a hydrophilic API. In an effort to further elucidate the release and bioadhesive characteristics of lectin-grafted formulations in vitro, the particles were coated with wheat germ agglutinin. The microparticles exhibited thermo-responsive release since no free fluorescein was detected at 4 °C or room temperature. At body temperature, however, more than 80% of the payload was released within 48 h. The adhesion of lectin-grafted particles to Caco-2 monolayers, which were applied as a model for the human intestinal epithelium, exceeded that of plain ones 1.5-fold as also observed by fluorescence microscopy. Furthermore, the amount of model drug bound and taken up into the cells was 5.8-fold higher after incubation for 4 h at 37 °C as compared to fluorescein in solution. According to fluorescence imaging a considerable amount of the total fluorescein payload was accumulated intracellularily after incubation for 5 h at 37 °C. These findings not only confirm the utility of bioadhesives of the second generation for improved absorption of low molecular weight hydrophilic compounds but also indicate storage stability of such suspensions at 4 °C and room temperature without any premature loss of API.