Bioactivity in SBF versus trace element effects: The isolated role of Mg2+ and Zn2+ in osteoblast behavior.

The bioactivity assay originally proposed by Kokubo is one of the most commonly used tests to indirectly evaluate the biocompatibility of bioactive glasses. However, extensive evidence has shown that trace elements present in biomaterials may stimulate cellular behavior in different ways even when no apatite formation is observed, i.e., in biomaterials with low or no bioactivity. To further elucidate this topic, we designed three different SiO2-rich bioglass compositions in which CaO was partially replaced by ZnO and MgO, two oxides known to affect bioactivity as well as osteoblastic behavior. The physicochemical changes induced by the presence of oxides and their effects on biological behavior, as well as the adhesion, proliferation and differentiation of human osteoblast-like osteosarcoma cells (MG-63), were followed by a bioactivity assay in simulated body fluid (SBF). The insertion of ZnO or MgO decreased the glass transition (Tg) and crystallization (Tc) temperatures as a function of the increase in nonbonding oxygens, which was directly reflected in the higher solubility. The release of Mg2+ ions from the MgO-containing samples inhibited the bioactivity in SBF, inducing high cell adhesion and proliferation and moderate ALP activity. The release of Zn2+ also inhibited the bioactivity in SBF but, in contrast to the release of Mg2+, induced low cell adhesion and proliferation and high ALP activity compared to the control.

The anti-inflammatory and antinociceptive activity of albumins from Crotalaria retusa seeds.

Seeds of Crotalaria retusa L. are used in popular medicine because of their pharmacological properties. The albumin fraction obtained from its seeds contains lectin, a protein known to have analgesic and anti-inflammatory properties. Thus, albumins extracted from C. retusa were investigated for their anti-inflammatory and antinociceptive effects. The intraperitoneal administration of different doses of albumins (5, 10 or 20mg/kg) significantly inhibited the mice paw edema induced by carrageenan (maximum inhibition rate of 80.9% at four hours, 20mg/kg), and this event was followed by diminishing paw myeloperoxidase measurements. Albumins (20mg/kg) also inhibited neutrophil migration into the peritoneal cavity induced by carrageenan. However, no effect was observed in the dextran-induced paw edema and abdominal contortions induced by acetic acid. Moreover, albumins (20mg/kg) significantly reduced the second (inflammatory) phase of the licking time induced by formalin. The detection of heammaglutinating activity against human erythrocytes in albumins evidences the presence of lectin in seeds of C. retusa. Our data showed that seeds of C. retusa had anti-inflammatory and antinociceptive properties and such activities are probably due to the inhibitory effect on neutrophil migration of lectin present in albumins.