S. Panzavolta

Effect of Mg2+, Sr2+, and Mn2+ on the chemico-physical and in vitro biological properties of calcium phosphate biomimetic coatings

We previously developed a calcium phosphate (CaP) calcifying solution that allows to deposit a uniform layer of nanocrystalline apatite on metallic implants in a few hours. In this work we modified the composition of the CaP solution by addition of Sr(2+), Mg(2+), and Mn(2+), in order to improve the biological performance of the implants. The results of the investigation performed on the coatings, as well as on the powders precipitated in the absence of the substrates, indicate that both Sr(2+) and Mg(2+) reduce the extent of precipitation, although they are quantitatively incorporated into the nanocrystalline apatitic phase. The inhibitory effect on deposition is much more evident for Mn(2+), which completely hinders the precipitation of apatite and yields just a small amount of amorphous phosphate relatively rich in manganese content. Human osteoblast-like MG-63 cells cultured on the different materials show that the Mg(2+) and Sr(2+) apatitic coatings promote proliferation and expression of collagen type I, with respect to bare Ti and to the thin layer of amorphous phosphate obtained in the presence of Mn(2+). However, the relatively high content of Mn(2+) in the phosphate has a remarkable beneficial effect on osteocalcin production, which is even greater than that observed for Sr(2+).

Alendronate and Pamidronate calcium phosphate bone cements : Setting properties and in vitro response of osteoblast and osteoclast cells

We have investigated the effect of Alendronate and Pamidronate, two bisphosphonates widely employed for the treatment of pathologies related to bone loss, on the setting properties and in vitro bioactivity of a calcium phosphate bone cement. The cement composition includes alpha-tricalcium phosphate (alpha-TCP) (90 wt%), nanocrystalline hydroxyapatite (5 wt%) and CaHPO(4) x 2H(2)O (5 wt%). Disodium Alendronate and disodium Pamidronate were added to the liquid phase (bidistilled water) at two different concentrations: 0.4 and 1mM (AL0.4, AL1.0, PAM0.4, PAM1.0). Both the initial and the final setting times of the bisphosphonate-containing cements increase with respect to the control cement. X-ray diffraction analysis, mechanical tests, and SEM investigations were carried out on the cements after different times of soaking in physiological solution. The rate of transformation of alpha-TCP into calcium deficient hydroxyapatite, as well as the microstructure of the cements, is not affected by the presence of Alendronate and Pamidronate. At variance, the bisphosphonates provoke a modest worsening of the mechanical properties. MG63 osteoblasts grown on the cements show a normal morphology and biological tests demonstrate very good rate of proliferation and viability in every experimental time. In particular, both Alendronate and Pamidronate promote osteoblast proliferation and differentiation, whereas they inhibit osteoclastogenesis and osteoclast function.

In Vivo and In Vitro Response to a Gelatin/α-Tricalcium Phosphate Bone Cement

We recently developed a new biomimetic calcium phosphate bone cement enriched with gelatin (GEL-CP) which exhibits improved mechanical properties with respect to the control cement (C-CP) and a good response to osteoblast-like cells. In this work, we have extended the investigation to primary culture of osteoblasts derived from normal (N-OB) and osteopenic (O-OB) sheep bones cultured on samples of GEL-CP, and their behavior was compared to that of cells cultured on C-CP as control. Cell morphology, proliferation, and differentiation were evaluated at 3 and 7 days. Preliminary in vivo tests were carried out onto critical size defects in the radius diaphysis of rats.

A Fast Biomimetic Method for Nanocrystalline Hydroxyapatite Coatings

We employed a slightly supersaturated solution (Ca/P) with an ionic composition simpler than that of simulated body fluid (SBF) to obtain a fast biomimetic coating on Ti6Al4V substrates. The results of thin film X-ray diffraction, FTIR, SEM, TEM-ED investigations indicate that hydroxyapatite (HA) nanocrystals are laid down in a few hours on the susbstrates. The amount of deposition increases with the immersion time. Furthermore, the thin layer of HA deposited after 3 h soaking in Ca/P solution acts as a catalyst for the further deposition of apatite from SBF.