Papers by Author: Renata Dias

Abstract: Osteoporosis is a ‘silent’ disease characterized by thinning cortical bone and disorganized trabecular architecture causing bone fragility leading to fracture. Osteoporosis results when the rate of bone resorption far exceeds the rate of bone formation. Current pharmaceutical interventions (estrogen therapy, bisphosphonate-based drugs) focus on inhibiting bone resorption. However, some of these therapies have serious side effects (e.g., cancer risk from estrogen therapy; osteonecrosis of the jaw and delayed fracture healing from bisphosphonate-based drugs). The long term objective of the study was to develop a novel material for potential osteoporosis therapy, prevention and fracture repair. This novel material MZF-CaP or synthetic bone mineral, SBM) incorporates Mg, Zn and F ions in a calcium phosphate matrix. Separately, magnesium (Mg), zinc (Zn) and fluoride (F) ions have been associated with biomineralization and osteoporosis therapy in human and in animals. MZF-CaP or SBM was prepared by a modified hydrolysis method previously described and characterized using x-ray diffraction, FT-IR spectroscopy, inductive coupled plasma and dissolution in acidic buffer. Separately, male and female Sprague-Dawley rats were randomly assigned to the following groups depending on the diet: GA: normal on basic diets; GB: on mineral deficient diets (md); GC: on md + Mg-CaP; GD: on md + Zn-CaP; GE: md+F-CaP; and GF: md+MZF-CaP. The rats were sacrificed after 3 months and the femur bones separated, cleaned of extraneous soft tissues and stored until needed for analyses. Femur bones were analyzed using microradiography (Faxitron), scanning electron microscopy (SEM) and microCT. Results: SEM, Faxitron and microCT analyses showed thinning of cortical bone and disorganized trabecular bone architecture for osteoporotic rats on mineral deficient diet (GB) and prevention of bone loss in rats receiving the supplemented diets (GC,GD,GE,GF). Conclusion: These results indicate that the novel material, MZF-CaP or SBM had a potential for osteoporosis therapy and prevention. Studies to demonstrate the use of SBM in reversing (recovering) bone loss are in progress.

Abstract: Our earlier studies showed that several ions inhibit the crystal growth of apatite and promote the formation of amorphous calcium phosphates (ACP). These ions include: magnesium (Mg), zinc (Zn), stannous (Sn), ferrous (Fe), carbonate (CO3), pyrophosphate (P2O7). The purpose of this study was to investigate the effect of combination of these ions (e.g., Mg & CO3, Mg & P2O7, Mg & Zn, etc) on the formation and stability of ACP. ACP compounds containing the different ions were prepared at 25 and 37oC according to the method we previously described. Chemical stability was investigated by suspending the different ACP preparations in solutions with or without inhibitory ions. Thermal stability was determined by sintering the ACP at different temperatures. Dissolution properties were determined in acidic buffer. The ACP before and after chemical or thermal treatment were analyzed using X-ray diffraction, infrared spectroscopy, and thermogravimetry. Results showed synergistic effects of inhibitory ions on the formation of ACP. ACP materials, regardless of their composition, remained amorphous even after heat treatment at 400oC. Transformation of ACP to other calcium phosphate phases depended on the pH and on the solution composition.