Biocompatibility of bioabsorbable Mg-Ca alloys with rare earth elements addition.

The objectives were to investigate the mechanical strength and biocompatibility of Mg2Ca2Gd and Mg1Ca2Nd (wt%) alloys developed for biomedical application as implantable bioabsorbable devices. Samples were implanted in New-Zealand rabbits tibia for 3, 6 and 8 weeks and compatibility analysis involved whole blood test, biochemistry, histopathology, histology, and radiographs. Refinement in grains were observed in Mg2Ca2Gd alloy; and Mg5Gd, Mg41Nd5, α-Mg and Mg2Ca phases were identified. Polarization curves revealed easier oxidation of Mg2Ca2Gd alloy, smaller values of corrosion rate and a higher polarization resistance of Mg1Ca2Nd. Adequate compatibility of both alloys was identified with pre-osteoblast stem cells. Red and white cells stayed compatible with reference ranges. Enzymes from liver and kidneys stayed at regular values and samples from kidneys and liver tissues presented similar organization to control animals. Histological displays from implantation sites disclosed well-structured tissues with evidences of bone cells activities compatible with the new bone tissues observed. Radiographs from tibias did not revealed relevant gas pockets. Mg2Ca2Gd alloy demonstrated faster degradation. Adequate biocompatibility was observed in Mg-Ca alloys with RE addition, being potential candidates for development of metallic implantable bioabsorbable devices.