The Study On Effect Of Calcium Phosphate Drug Delivery System

It has been wildy investigated using Calcium Phosphate Cements(CPCs) as Drug Delivery System. In particular, CPCs can be prepared without the high temperature process, which provide the possibility to use CPCs as delivery systems for some growth factors or some drugs in orthopaedic to improve the concrescence of bone fraction. It is well known that all CPCs are formed by a combination of one or more calcium phosphates, upon mixing with the liquid phase, usually water or an aqueous solution, then becomes the paste to set and harden in ambient or after being implanted. Up to date, there are more than 200 kinds of CPCs. Amounts studies demonstrated that the release of drugs from CPCs depended on different factors such as the microstructure, the drug solubility, the type of bond between the drug and the matrix which holds it, and the mechanism of degradation of the matrix. However, it is unclear that the mechanism of the drug load and release from various typies of calcium phosphate. In our group, CaP biomaterials, including in CaP powders and CPCs loading Chinese medicne, Salvia Miltiorrhiza Bunge (SMB), which is a well-known and inexpensive Chinese medicine herb under the traditional Chinese name Dan-shen, have been prepared and characterized recently. However, the release of SMB from various types of calcium phosphate is also unclear.In this study, three kinds of Ca/P powders, Hydroxyapatite(HA), Calcium Deficient Hydroxyapatite(CDHA) and Dicalcium phosphate (DCP) with Ca/P molar ratios 1.67, 1.50 and 1.00, were synthesized through the wet chemical method accompanying with SMB injection, respectively. All filtration cakes were dried at 65℃until their weights without change and milled to powders. As-received CaP powders with and without SMB were soaked in simulated body fluid ( SBF ) up to 360 h at 37℃with the solid to liquid ratio of 1 : 10. Meanwhile, the reaction products were characterized by X-ray diffraction analysis (XRD), Ultraviolet-Visible Spectrometry (UV-VIS), Thermal Analysis (TA), pH meter and Atomic Absorption Spectrum (AAS) to investigate the influence of factors on drug delivery.Based on the present results, it was concluded:1. The SMB could be added on the calcium phosphate through the wet chemical method accompanying with the SMB injection. The addition of the SMB to the calcium phosphate had no effect on their phase, especially the DCP. This was mainly due to the fast nucleation and growth rate of DCP resulting in larger size particles formed with the smaller specific surface area. The absorbability increased with the calcium phosphate molar rate increasing which led to the increasing content of the SMB contained in various CaP.2. The content of SMB in calcium phosphate drug delivery system would increase with the increase of the SMB injection dosage. The more content of SMB would promote the SMB releasing. In the initial 12 hours of the releasing, drug concentration was in disorder. Then it increased gradually and became stable. The releasing quantity of the SMB and the Ca²⁺ concentration increased with the SMB dosage increasing. The order was CaP/50>CaP/40>CaP/30. But the change of the pH value was contrasted with the Ca²⁺ result. This was mainly due to the pH value decreased with the quantity of the SMB increasing. The dosage of the SMB had more influence in the releasing of the HA than the DCP.3. The result of the releasing of the SMB showed that the releasing quantity of the SMB was increased with the calcium phosphate molar rate increasing. The SMB released from the CaP powders accompanying with the degradation of CaP. The order of the three calcium phosphates solution was DCP>CDHA>HA at the scope of pH value from 7.2 to 7.4. But the release of the SMB stimulated the dissolution of the CaP. So the Ca²⁺ concentration and the pH value had been affected by the release of the SMB. And the order of the Ca²⁺ concentration and the pH value of the three CaP/SMB was CDHA/SMB < HA/SMB