Osteoclastic resorption of bones
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 developing effective therapeutic solutions
for those diseases. Here, we reported the development of a novel and
robust nanostructured calcium phosphate coating with unique functions
on the track-etched porous membrane by using an ammonia-induced mineralization
(AiM) technique. The calcium phosphate coating uniformly 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 the one hand, enhances coating
integration with a 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 were first demonstrated as a drug screening
device by using alendronate, a widely used drug for osteoporosis.
It was confirmed that the delivery of alendronate significantly decreased
both the number of monocyte-differentiated osteoclasts and coating
resorption. To demonstrate the application in studying bone metastasis,
we delivered a 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.