Preparation and characterization of drug delivery carriers for local administration of sodium alendronate

Osteoporosis is often treated with the use of sodium alendronate - a drug that inhibits osteoclast-mediated bone resorption and regulates rate of bone turnover. However the disadvantage of oral administration of sodium alendronate is poor drug absorption from the gastrointestinal track and severe adverse effects. Therefore we propose local sustained drug delivery systems based on poly(lactide-co-glycolide) (PLGA) micro- and nanocarriers, which can be administered directly by simple injections to the required place in the body. In this study we encapsulated sodium alendronate into PLGA micro- and nanospheres via a double-emulsification technique. Emulsion formation in different shear rate conditions was used to optimize the size of the carriers. The prepared microspheres were observed under an inverted optical microscope which confirmed their micrometric size. The nanospheres were analyzed by atomic force microscopy, which allowed visualization of their shape and measurement of their size. Moreover the hydrodynamic diameter of the nanospheres, polydispersity index as well as zeta potential were examined by dynamic light scattering. The experiments show that drug release does not depend on the size of the carriers. Analyzed carriers do not cause cytotoxicity upon contact with osteoblast like-cells.