Cytocompatibility and biocompatibility of nanostructured carbonated hydroxyapatite spheres for bone repair

Mônica Diuana Calasans-Maia,Bruno Raposo De Melo,Rodrigo Figueiredo De Brito Resende,Gutemberg Gomes Alves,José Mauro Granjeiro,Rafael Seabra Louro,Suelen Cristina Sartoretto,Adriana Terezinha Neves Novellino Alves

doi:10.1590/1678-775720150122

Abstract

ABSTRACTObjective The aim of this study was to investigate the in vitro and in vivo biological responses to nanostructured carbonated hydroxyapatite/calcium alginate (CHA) microspheres used for alveolar bone repair, compared to sintered hydroxyapatite (HA).Material and Methods The maxillary central incisors of 45 Wistar rats were extracted, and the dental sockets were filled with HA, CHA, and blood clot (control group) (n=5/period/group). After 7, 21 and 42 days, the samples of bone with the biomaterials were obtained for histological and histomorphometric analysis, and the plasma levels of RANKL and OPG were determined via immunoassay. Statistical analysis was performed by Two-Way ANOVA with post-hoc Tukey test at 95% level of significance.Results The CHA and HA microspheres were cytocompatible with both human and murine cells on an in vitro assay. Histological analysis showed the time-dependent increase of newly formed bone in control group characterized by an intense osteoblast activity. In HA and CHA groups, the presence of a slight granulation reaction around the spheres was observed after seven days, which was reduced by the 42nd day. A considerable amount of newly formed bone was observed surrounding the CHA spheres and the biomaterials particles at 42-day time point compared with HA. Histomorphometric analysis showed a significant increase of newly formed bone in CHA group compared with HA after 21 and 42 days from surgery, moreover, CHA showed almost 2-fold greater biosorption than HA at 42 days (two-way ANOVA, p<0.05) indicating greater biosorption. An increase in the RANKL/OPG ratio was observed in the CHA group on the 7th day.Conclusion CHA spheres were osteoconductive and presented earlier biosorption, inducing early increases in the levels of proteins involved in resorption.

Highlights

The application of procedures for bone regeneration is becoming a daily practice in orthopedic and maxillofacial surgery, motivated by the wide acceptance of dental implants as an option for oral rehabilitation
Several studies have demonstrated the potential for the use of autogenous bone grafts for bone regeneration due to the bone-forming cells potentially harbored in such grafts and their ability to release substances that induce bone formation as well as to serve as a scaffold for bone formation11,26
In vitro evaluation of biocompatibility The cytotoxicity assays, performed using murine pre-osteoblasts (MC3T3-E1), showed that both the carbonated hydroxyapatite/calcium alginate (CHA) and HA groups were cytocompatible, with more than 75% cell survival observed when compared to the experimental control group, as recommended by international standards (ISO 7405:2008)

Summary

Introduction

The application of procedures for bone regeneration is becoming a daily practice in orthopedic and maxillofacial surgery, motivated by the wide acceptance of dental implants as an option for oral rehabilitation. Difficulties in obtaining autogenous bone grafts and limitations, such as postoperative discomfort in patients, donor site morbidity, and the limited availability of graft materials, as well as ethical issues and the possibility of disease transmission from allogeneic or xenogeneic grafts, have motivated researchers to develop synthetic or alloplastic materials. Difficulties in obtaining autogenous bone grafts and limitations, such as postoperative discomfort in patients, donor site morbidity, and the limited availability of graft materials, as well as ethical issues and the possibility of disease transmission from allogeneic or xenogeneic grafts, have motivated researchers to develop synthetic or alloplastic materials1,16,17,22 In this context, calcium phosphates present interesting features related to bone-targeting applications such as excellent bioactivity, the ability to bond directly to bone, and osteoconductivity. Calcium phosphates can be resorbed, showing solubility rates that are dependent on their composition and microstructural features

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Discussion

Conclusion