Microfluidic synthesis of zoledronic acid loaded chitosan nanoparticles used for osteogenic differentiation of mesenchymal cells.

Zoledronic acid (ZA) is known as a potent bisphosphonate in osteogenic differentiation, but at high doses, it possesses toxic effects and causes decreased proliferation and differentiation of osteoblasts. Therefore, encapsulation of ZA into nanoparticles and control of its release is expected to promote differentiation of stem cells into osteoblasts. The present work aimed to develop a simple method for synthesis of monodisperse ZA-loaded chitosan (CS) nanoparticles. In this regard, we proposed a microfluidic synthesis of nanoparticles through the ionic cross-linking of CS in the presence of ZA without a crosslinker. The main advantages of these microfluidic generated nanoparticles were narrow size distribution and fine spherical shape. Conversely, the nanoparticles that were synthesized using a bulk mixing method had an irregular shape with a broad size distribution. Real-time PCR assay as well as alizarin red staining were used to evaluate the in-vitro osteogenic potential of the nanoparticles. The results indicated that the controlled release of ZA from the microfluidic system generated uniform nanoparticles, improving the osteogenic differentiation of mesenchymal stem cells. Additionally, this microfluidic device provided the well-controlled synthesis of novel nanoparticles with a modified CS macromolecular polymer for targeted drug delivery systems.