Synthesis And Bioactivity Investigation Of A Series Of HAP Composites

When a patient requires an internal fixation device or an artificial joint, bacterial infection after implant placement introduces a significantly rising complication due to the presence of foreign materials inside the body interfering with the host's defense mechanism. Many studies have shown that delivering antibiotics to bone-implant interface is effective in reducing bacterial adhesion. Among these bacteria, Staphylococcus aureus is a common one in the myelopathy. Although the use of antibiotics has greatly reduced the incidence of infection diseases, it also led to the drug-resistant appearance of bacteria like Staphylococcus aureus (MRSA). In order to overcome the rapid development of this drug-resistance, some new reagents should be synthesized.8-hydroxyquinoline (8-HQ) is a well-known lipophilic metal chelator. Its copper chelate has been used as a fungicide in agriculture field and as the preserver for textiles, wood and paperIn recent years, some new applications of rare earth elements have been found in many areas because of their unique chemical and physical properties. For instance, they have been used as catalysts, glass ceramics, fertilizers, pesticides and so on. The reason to impel us testing this agent is that some lanthanides have been used for clinical treatment as antibacterial agents in wound excision after burn and there was no obvious toxicity in a wide range of concentrations of them.J.Z. Ni reported that the rare earth-organism complexes can provide much more effective antibacterial activities than rare earth. Therefore, in the present report three complexes of RE(AC)(HQ)2·H2O (RE = La, Gd or Y) were prepared, which show increased antibacterial activities.Though a high concentration of antibiotic at the bone-implant interface should be essential to prevent these bacterial infections, however the concentration of the drug will be low in the bone tissue where a successful blood supply is lack. So it is now recognized that conventional bone treatment using systemic antibiotics is expensive and prone to complications. One management method of utilizing the surgical implantation of antibiotic polymethylmethacrylate (PMMA) bone cements for local delivery of antibiotics makes it possible to reach high local drug levels while maintaining low systemic levels and shows effect on Myelopathy [3,17]. However, PMMA has potential damage to human immune system and need to be taken out with second operation, so PMMA is not very perfectHydroxyapatite(HAP) is a important inorganic component d in human bone and teeth,can form a direct chemical bond with surrounding bone tissue,In the same time, it can be degraded in vivo and supply the requirement of calcium for bone regeneration. therefore has been used extensively in orthopedics and bone regeneration. Nano particles tend to show some unique specialities, nano hydroxyapatite (nano-HAP), therefore has attracted much more attation in recent years.The objective of the present research is to synthesize a series of new components of nano-HAP with biological activities, characterizing their physical properties and researching their biological activities.1. First, the physical properties of these composites were characterized by means of scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD). Nano-composite of Hydroxyapatite/Lysozyme was synthesized by chemical wet method in size of 100 nm.It was characterized by nitrongen gas adsorption method,IR,SEM and UV-Visible technique and compared with the dipping-adsorbing composite.The composite by wet method has much more content and activity of Lysozyme than the composite by dipping-adsorbing method.These results suggust the composite by wet method as a controlled released carrier of Lysozyme.2. Secondly, the antibacterial activity of three nanoscale organic-inorganic hybrid composites of rare-earth complexes of 8-Hydroxyquinoline (8-HQ) with formulae RE(AC)(HQ)2·H2O (RE=La, Gd or Y) and hydroxyapatite (HAP) were studied. These nanoscale hybrid composites were directly prepared by the wet methods. While the physical properties of these composites were characterized by means of scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD), the antibacterial activities were tested by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods.The results showed, all three composites are less than 50-60nm in size and exhibit stronger bacteriostatic activities against bacteria of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Their antibacterial activities were then tested and all showed higher antibacterial activities against S. aureus than against E. coli. Among these three composites, at a high concentration (> 600μg/mL) all three composites did not show bacteriostatic activities;at a middle concentration (in the range of 169μg/mL to 600μg/mL) they showed obviously bacteriostatic activities;at a low concentration (in the range of 26μg/mL to 169μg/mL) they can almost kill all the bacteria. La-HQ/HAP and Gd-HQ/HAP show stronger antibacterial efficacy than Y-HQ/HAP with the antibacterial activity of La-HQ/HAP comparable to that of ampicillin/HAP. These newly synthesized composites will be promising materials in the treatment of diseases for the musculoskeletal system with their enhanced antibacterial activity and good biocompatibility.3. Nano-composite of RE/HAP was synthesized by two method:chemical wet method and hydrothermal synthesis. While the physical properties of these composites were characterized by means of scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD).The cytotoxic effects on Hela by RE/HAP were determined by the methods of methy1 thiazoly1 tetrazolium(MTT), the difference of cell cycle induced by RE/HAP were investigated by flow cytometry (FCM).The results of MTT showed that the inhibition of the pure HAP is very low and was by 5.67 % at a dose of 500 ug/mL. At the same dose, the inhibition of RE2a/HAP were obvious, for example the inhibition of Y2a/HAP,Gd2a/HAP,La2a/HAP were separately 80.31 %,55.43 % and 44.93 %。Comparing with HAP, the effects of RE2a/HAP on Hela cell cycle by flow cytometry the Hela cell numbers in G1 phase were increased obviously and the cell numbers in G1 phase were decreased . The sequence of the effect on Hela cell cycle is La_2a/HAP>Y_2a/HAP>Gd_2a/HAP.