  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.
