In vivo Evaluation of bone regeneration behavior of macroporous β-TCP/layered double hydroxide nanocomposite granule-shaped bone substitute
In vivo Evaluation of bone regeneration behavior of macroporous β-TCP/layered double hydroxide nanocomposite granule-shaped bone substitute
Neda Eskandari,1,*Seyedeh Sara Shafiei,2Mohammad Mehdi Dehghan,3
1. Department of Stem cell and Regenerative Medicine, Institute of Medical Biotechnology, National Institute of Genetic Engineering and Biotechnology, Tehran 14965/161, Iran 2. Department of Stem cell and Regenerative Medicine, Institute of Medical Biotechnology, National Institute of Genetic Engineering and Biotechnology, Tehran 14965/161, Iran 3. Department of Surgery and Radiology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
Introduction: Large bone defects in the trauma, tumor or congenital deformity represent a difficult problem in orthopedic surgery. Bone defects are often too large to be fixed by self-healing, so it can lead to the bone deformation. Many experiments have demonstrated that calcium phosphate ceramics can be easily fabricated and they have unique physical and chemical properties.
The suitable biomaterial alternatives for potential bone regeneration is β-tricalcium phosphate (β-TCP).
Porous β-TCP granules are clinically used in maxillofacial surgeries and implants fixation but its biomedical applications have been largely limited by their poor mechanical properties. One strategy to overcome this challenge is to design calcium phosphate-based nanocomposites. Several studies have demonstrated that the mechanical strength of CaP materials can be improved by using a suitable reinforcing phase such as biocompatible nanoparticles.
Layered Double Hydroxides (LDHs; with the formula Mg6Al2(OH)16CO3·4H2O), also called anionic nanoclays, are clay-like materials that show promising properties for a large number of applications. Recently, researchers have reported the use of LDH nanoparticles as reinforcing agents of polymeric matrices. The addition of LDH to CaPs may modify physicochemical, mechanical and biological properties of CaPs.
In our previous study, for the first time, we showed that the inclusion of LDH into β-TCP granules enhanced mechanical properties of β-TCP. The mechanical test proved that the inclusion of LDH nanoclay into β-TCP granules caused an increase in compressive modulus that make it suitable for load bearing areas of bone structure, thus reducing the risk of bone fractures that is an important issues commonly reported.
This study was based on in vivo assessment of bone regeneration capacity of synthesized porous β-TCP/LDH nanocomposite granules. The aim of this study was to explore the effects of β-TCP granules reinforced with LDH compared to pristine β-TCP granules, in terms of osteoconductivity and biodegradability.
Methods: For the in vivo investigation of the porous granules, we used a total of 18 male New Zealand white rabbits. Three non-critical defects were produced on the distal femur by a dental drill. Then, defects were filled with the two different types of granules (with/without LDH) and the bone defect without any treatment was used as the negative control and were left in situ for up to 3 months for evaluation of bone neoformation.
In this study, X-ray radiographic, micro-computed tomography and histological staining analysis were taken to evaluate the percentage of bone ingrowth and biodegradability of the porous granules.
Results: After 12 weeks of the implantation, the results indicated that in the empty defect, there was only 6.5% new bone formation, whereas in the defected filled with β-TCP granules, there was 33.3% new bone formation and 33.3% granule residues, Also, the defected filled with β-TCP/LDH granules showed the powerful capability of 40% bone regeneration and 46.6% granule residues in 3 months, Which implies that most of the porous β-TCP in bone defect areas was absorbed and bone regeneration increased critically in both of β-TCP granules during the study and also the amount of new bone formation in the bone defect filled with both of granules was almost six times higher than the empty defects.
Although no significant difference in bone formation for two different granules was observed, the higher biodegradability was detected in β-TCP granules in comparison to β-TCP/LDH granules. It can be concluded that the osteoconductity properties have been preserved and its biodegradation rate has been decreased by addition of LDH.
Conclusion: It can be deduced that the bone defects regenerated with the both of β-TCP granules become similar to the non-manipulated bone and the both of β-TCP granules were biodegradable, which is essential property for bone regeneration and the composite of β-TCP granules with LDH were effective in inducing the bone formation.
As the granule residues in β-TCP/LDH granules was higher than β-TCP granules, so the degradation rate was slower in this novel nanocomposite, we can consider it a good point that this nanocomposite could prevent osteoporosis by reducing osteoclasts reabsorption and brings the advantage of bone mechanical stability for load-bearing sites of the skeleton and reduces the risk of bone fracture. Therefore, it seems that the β-TCP/LDH nanocomposite granules has the potential to be a good candidate for orthopedic or reconstructive surgery.