In vitro characterization of hydroxyapatite and cobalt ferrite nanoparticles compounds and their biocompatibility in vivo

Abstract

Bioactive materials in combination with antibiotics have been widely developed for the treatment of bone infection. Thus, this work aims to characterize six biomaterials formulated with different concentrations of hydroxyapatite and cobalt ferrite nanoparticles, in addition to the antibiotic ciprofloxacin, using X-ray diffraction (XRD), scanning electron microscopy (SEM), and the antibiotic diffusion test on agar. Furthermore, in vivo biocompatibility and the reabsorption process of these materials were analyzed. XRD showed that both hydroxyapatite and cobalt ferrite present high crystallinity. The photomicrographs obtained by SEM revealed that composites have a complex surface, evidenced by the irregular arrangement of the hydroxyapatite and cobalt ferrite granules, besides demonstrating the interaction between their components. The antibiotic-diffusion test showed that all biomaterials produced an inhibition halo in Staphylococcus aureus cultures. For the biocompatibility study, composites were surgically implanted in the dorsal region of rabbits. At 15, 30, 70, and 100 days, biopsies of the implanted regions were performed. The biomaterials were easily identified during histological analysis and no significant inflammatory process, nor histological signs of toxicity or rejection by the adjacent tissue were observed. We can conclude that the biomaterials analyzed are biocompatible, degradable, and effective in inhibiting the in vitro growth of Staphylococcus aureus. Graphical abstract.

Keywords: Biocompatibility; Biomaterial; Cobalt ferrite nanoparticles; Hydroxyapatite.

Graphical abstract

Fig. 1

X-ray diffraction (XRD) of the hybrid composites: (a) CoFe₂O₄@SiO₂:HAp (HC); (b) CoFe₂O₄@SiO₂:γ (Cγ); (c) CoFe₂O₄@SiO₂:Hap (70:30) (JCoFSγ₁); CoFe₂O₄@SiO₂:HAp (70:30) (HCoFSγ₁); CoFe₂O₄@SiO₂:HAp (50:50) (HCoFSγ₂) e CoFe₂O₄@SiO₂:HAp (30:70) (HCoFSγ₃)

Fig. 2

Photomicrographs of scanning electron microscopy of biomaterials. Bars: 20 µm. a HCoFSγ₁ (70:30) (b) HCoFSγ₂ (50:50); (c) HCoFSγ₃ (30:70); (d) JCoFSγ (70:30); (e) Cγ; and (f) HC (70:30). The arrows highlight the pores

Fig. 3

Petri dishes showing the halos formed in the agar-diffusion test. Bm1: HC; Bm2: HCoFSγ₂; Bm3: HCoFSγ₁; Bm4: HCoFSγ₃; Bm5: JCoFSγ₁; Bm6: Cγ; Cipro: ciprofloxacin disk

Fig. 4

Photomicrographs at 15 (a and b), 30 (c), and 70 (d, e, and f) days after implantation of biomaterials. (a) HCoγ₁; (b) HCoγ₂; (c) HCoγ₃; (d) Cγ; (e) and (f) HC. Asterisk: biomaterial; red arrow: hyperemia; arrowhead: fibrous capsule formation; circle: inflammatory infiltrate; square: bleeding; CT: conjunctive tissue. (a), (c), (d), and (f): 100x magnification; (b) and (e): 400x magnification. HE. Bars: 40 µm

Fig. 5

Photomicrographs at 15 (a), 30 (b), 70 (c), and 100 (d) days after implantation of the materials. (a), (b) and (c) HC; (d) Cγ. Asterisk: biomaterial; arrowhead: fibrous capsule; triangle: hemosiderin deposit; circle: inflammatory infiltrate; FT: organized fibrous tissue (collagen fibers). (a), (b), and (d):100x; (c): 400x. HE. Bars: 40 µm