No abstract

Calcium phosphate biomaterials such as calcium deficient apatite (CDA) have been contemplated as carrier for delivery of bisphosphonate in bone tissues. In the present work, we have investigated the in vitro biological properties of Zoledronate-loaded CDA. CDA was loaded with zoledronate according to a previously described coating process. 31P MAS NMR spectra demonstrated the effective loading of zoledronate onto CDA. Using 14C labeled zoledronate, we then demonstrated the in vitro release of zoledronate from CDA. In a first set of experiments, we confirmed that Zoledronate reduced the number of TRAP-, vitronectin receptor-, and F-actin ring-positive cells as well as the resorption activity of osteoclasts obtained from a total rabbit bone cell culture. Interestingly, Zoledronate-loaded CDA and its extractive solutions decreased the osteoclastic resorption. Finally, zoledronate-loaded CDA did not affect the viability and alkaline phosphatase activity of primary osteoblastic cells. These data demonstrate that CDA is effective for loading and release of zoledronate. The released zoledronate inhibited osteoclastic resorption without affecting osteoblasts. Our findings therefore suggest that such a drug delivery system would allow an increase in the efficiency of bisphosphonates by being locally available. Further experiments are now required to evaluate the in vivo antiresorptive activity of this concept.

though the reactable surface area of this Pt is large. This is probably because the methanol molecules have difficulty reaching the surfaces of the Pt particles inside the SWNHs; when Pt particles are deposited outside the SWNHs there is no obstacle to methanol decomposition on the Pt surfaces.In summary, we have found that Pt particles are preferentially deposited inside the nanospaces of SWNHs and located near the defects. Furthermore, they have an upper limit in their sizes and quantities. We have therefore presented a simple method for preparing size-controlled fine Pt particles. ExperimentalHoles were pierced through SWNH walls by treating the dispersed SWNH aggregates for 15 min in a 70 % nitric acid (HNO 3 ) solution at either 25 C or 130 C. The resultant materials were subsequently washed with pure water.The Pt-particle-forming method we used in this study was the conventional colloid-precursor method [11]. The Pt colloid precursor was prepared by adding NaHSO 3 to an H 2 PtCl 6 aqueous solution, then the HNO 3 -treated SWNHs were added. Pt/SWNH weight ratios were 1:4, 1:1, and 4:1. The Pt-containing colloids were adsorbed by the HNO 3 -treated SWNHs upon addition of H 2 O 2 at an appropriate pH. The samples were centrifuged with water to remove Na, S, and Cl ions, and dried. The Pt colloids adsorbed by the HNO 3 -treated SWNHs were reduced to Pt metal in a H 2 /Ar atmosphere at room temperature. We confirmed that the Pt particles formed after hydrogen reduction were crystallites by X-ray diffraction measurements. The Pt contents in the resultant Pt/SWNH composites were estimated to be 20, 50, and 80 wt.-% from thermogravimetric analysis, indicating that almost all the platinum was adsorbed on the SWNHs.