Evaluation of Two Highly Porous Microcrystalline Biphasic Calcium Phosphate-Based Bone Grafts for Bone Regeneration: An Experimental Study in Rabbits

A biphasic bone grafting biomaterial based on a mixture of calcium phosphates and beta-tricalcium phosphate (β-TCP) phases with high nanoporosity was synthesized. The synthesis route was based on calcium phosphate composition and the incorporation of glycolic acid as a pore former, giving a material composed of 97% β-TCP and 3% calcium orthophosphates (CaPO4). An in vitro study of the purity, microstructure, crystalline domain, and pores size for the material obtained was performed by SEM analysis as well as full structural characterization. The region of interest related to the surface was determined by the specific surface area measured with the BET method. In vivo evaluation of bone response was performed by implanting the new low-cost biphasic manufacturing material synthesized in this work, which was compared with a biphasic material of similar chemical and microstructural composition existing in the commercial market and with higher cost called Synergy Odontit® β-TCP. The materials were implanted separately into 5 mm diameter defects in the tibias of New Zealand White rabbits at 30, 60, and 90 days. The results obtained showed that the host tissue well accepted the new biphasic material;the presence of new bone formation was observed. A more complete resorption was observed for the new microcrystalline biphasic material compared to for a commercial β-TCP material.

Degradation of 3D-printed magnesium phosphate ceramics in vitro and a prognosis on their bone regeneration potential

Regenerative bone implants promote new bone formation and ideally degrade simultaneously to osteogenesis.Although clinically established calcium phosphate bone grafts provide excellent osseointegration and osteoconductive efficacy,they are limited in terms of bioresorption.Magnesium phosphate(MP)based ceramics are a promising alternative,because they are biocompatible,mechanically extremely stable,and degrade much faster than calcium phosphates under physiological conditions.Bioresorption of an implant material can include both chemical dissolution as well as cellular resorption.We investigated the bioresorption of 3D powder printed struvite and newberyite based MP ceramics in vitro by a direct human osteoclast culture approach.The osteoclast response and cellular resorption was evaluated by means of fluorescence and TRAP staining,determination of osteoclast activities(CA II and TRAP),SEM imaging as well as by quantification of the ion release during cell culture.Furthermore,the bioactivity of the materials was investigated via SBF immersion,whereas hydroxyapatite precipitates were analyzed by SEM and EDX measurements.This bioactive coating was resorbed by osteoclasts.In contrast,only chemical dissolution contributed to bioresorption of MP,while no cellular resorption of the materials was observed.Based on our results,we expect an increased bone regeneration effect of MP compared to calcium phosphate based bone grafts and complete chemical degradation within a maximum of 1.5-3.1 years.

Comparative evaluation of the physicochemical properties of nano-hydroxyapatite/collagen and natural bone ceramic/collagen scaffolds and their osteogenesis-promoting effect on MC3T3-E1 cells

The use of various types of calcium phosphate has been reported in the preparation of repairing materials for bone defects.However,the physicochemical and biological properties among them might be vastly different.In this study,we prepared two types of calcium phosphates,nano-hydroxyapatite(nHA)and natural bone ceramic(NBC),into 3D scaffolds by mixing with type I collagen(CoL),resulting in the nHA/CoL and NBC/CoL scaffolds.We then evaluated and compared the physicochemical and biological properties of these two calcium phosphates and their composite scaffold with CoL.Scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared spectroscopy(FTIR),X-ray diffraction spectroscopy(XRD)and compressive tests were used to,respectively,characterize the morphology,composition,distribution and the effect of nHA and NBC to collagen.Next,we examined the biological properties of the scaffolds using cytotoxicity testing,flow cytometry,immunofluorescence staining,biocompatibility testing,CCK-8 assays and RT-PCR.The results reflected that the Ca2t released from nHA and NBC could bind chemically with collagen and affect its physicochemical properties,including the infrared absorption spectrum and compression modulus,among others.Furthermore,the two kinds of scaffolds could promote the expression of osteo-relative genes,but showed different gene induction properties.In short,NBC/CoL could promote the expression of early osteogenic genes,while nHA/CoL could upregulate late osteogenic genes.Conclusively,these two composite scaffolds could provide MC3T3-E1 cells with a biomimetic surface for adhesion,proliferation and the formation of mineralized extracellular matrices.Moreover,nHA/CoL and NBC/CoL had different effects on the period and extent ofMC3T3-E1 cell mineralization.