Ammonia-induced Calcium Phosphate Nanostructure: A Potential Assay for Studying Osteoporosis and Bone Metastasis

Osteoclastic resorption of bone plays a central role in both osteoporosis and bone metastasis. A reliable in vitro assay that simulates osteoclastic resorption in vivo would significantly speed up the process of devel-oping effective therapeutic solutions for those diseases. Here we reported the development of a novel and robust nano-structured calcium phosphate coating with unique functions on the track-etched porous mem-brane by using an ammonia-induced mineralization (AiM) technique. The calcium phosphate coating uni-formly covers one side of the PET membrane enabling testing for osteoclastic resorption. The track-etched pores in the PET membrane allow calcium phosphate mineral pins to grow inside, which, on one hand, enhances coating integration with membrane substrate, and on the other hand provides diffusion channels for delivering drugs from the lower chamber of a double-chamber cell culture system. The applications of the processed calcium phosphate coating was first demonstrated as a drug screening device by using alen-dronate, a widely used drug for osteoporosis. It was confirmed that the delivery of alendronate significant-ly decreased both the number of monocyte-differentiated osteoclasts and coating resorption. To demon-strate the application in studying bone metastasis, we delivered PC3 prostate cancer conditioned medium and confirmed that both the differentiation of monocytes into osteoclasts and the osteoclastic resorption of the calcium phosphate coating were significantly enhanced. This novel assay thus provides a new platform for studying osteoclastic activities and assessing drug efficacy in vitro.