Nano-scale characterization of nano-hydroxyapatite incorporated chitosan particles for bone repair

Fabrication and properties of hydroxyapatite/chitosan composite scaffolds loaded with periostin for bone regeneration

This paper reports a facile fabrication method of hydroxyapatite/chitosan (HAp/CS) composite scaffold with 3D porous structure without using any chemical cross-linkers. The HAp particles had an urchin-like hollow microstructure and high surface area, which was uniformly dispersed into the pore walls of the HAp/CS scaffold. The addition of HAp can efficiently enhance the mechanical properties and bioactivity of the HAp/CS scaffold. Moreover, periostin was successfully loaded onto the HAp/CS scaffold. When applied to the repair of bone defect in a rat mandibular model, the HAp/CS scaffold loaded with periostin can enhance osteointegration and accelerate bone regeneration. Our research combines periostin with the HAp/CS composite material, which provides a novel strategy to improve bone regeneration and has great application prospect in bone repair fields.

Preparation and properties of nano silica-based bioactive glass/apatite/sodium alginate composite hydrogel

In this paper, given the lack of osteogenic activity of sodium alginate (SA) hydrogel and to simulate the composition of natural bone, ionic-crosslinking NBG/n-HA/SA hydrogel scaffolds were prepared by using nano bioactive glass (NBG) and nano hydroxyapatite (n-HA) with high bioactivity as composite calcium sources and reinforcement phases, and D-gluconic acid δ-lactone (GDL) as the coagulant. The results showed that the mixture of the precursor forming the network had good injectability and plasticity. When the dosage of GDL was 0.75 g, the gelling time of the composite hydrogel could be regulated within 4-8 min, and the hydrogel had high compressive strength (170-220 kPa), as well. When the mass ratio of calcium source to SA was 1:1, the crosslinking network was relatively uniform with a considerable number of large pores around 40 μm in the structure. In the immersion experiment in vitro, it was found that the composite hydrogel could promote the deposition of bone-like apatite on the material's surface. Meanwhile, the cell experiments in vitro verified that the NBG/n-HA/SA composite hydrogel had good cytocompatibility without cytotoxicity. Moreover, the composite hydrogel could enhance the activity of ALP of mouse bone marrow mesenchymal stem cells, and thus, it had good osteogenic activity.

Evaluation of the optimal dosage of BMP-9 through the comparison of bone regeneration induced by BMP-9 versus BMP-2 using an injectable microparticle embedded thermosensitive polymeric carrier in a rat cranial defect model

Bone morphogenetic proteins (BMPs) are well known as enhancers and facilitators of osteogenesis during bone regeneration. The use of recombinant BMP-2 (rhBMP-2) in bone defect healing has drawbacks, which has driven the scouting for alternatives, such as recombinant BMP-9 (rhBMP-9), to provide comparable new bone formation. However, the dosage of rhBMP-9 is quintessential for the facilitation of adequate bone defect healing. Therefore, this study has been designed to evaluate the optimal dosage of BMP-9 by comparing the bone defect healing induced by rhBMP-9 over rhBMP-2. The chitosan (CS) microparticles (MPs), coated with BMPs, were embedded in a thermoresponsive methylcellulose (MC) and calcium alginate (Alg) based injectable delivery system containing a dosage of either 0.5 μg or 1.5 μg of the respective rhBMP per bone defect. A 5 mm critical-sized cranial defect rat model has been used in this study, and bone tissues were harvested at eight weeks post-surgery. The standard tools for comparing the new bone regeneration included micro computerized tomography (micro-CT) and histological analysis. A novel perspective of analyzing the new bone quality and crystallinity was employed by using Raman spectroscopy, along with its elastic modulus quantified through Atomic Force Microscopy (AFM). Results showed that the rhBMP-9 administered at a dosage of 1.5 μg per bone defect, using this delivery system, can adequately facilitate the bone void filling with ample new bone mineralization and crystallinity as compared to rhBMP-2, thus approving the hypothesis for a viable rhBMP-2 alternative.

Nanomaterials for bone tissue regeneration: updates and future perspectives

Joint replacement and bone reconstructive surgeries are on the rise globally. Current strategies for implants and bone regeneration are associated with poor integration and healing resulting in repeated surgeries. A multidisciplinary approach involving basic biological sciences, tissue engineering, regenerative medicine and clinical research is required to overcome this problem. Considering the nanostructured nature of bone, expertise and resources available through recent advancements in nanobiotechnology enable researchers to design and fabricate devices and drug delivery systems at the nanoscale to be more compatible with the bone tissue environment. The focus of this review is to present the recent progress made in the rationale and design of nanomaterials for tissue engineering and drug delivery relevant to bone regeneration.

Thermoresponsive Injectable Microparticle-Gel Composites with Recombinant BMP-9 and VEGF Enhance Bone Formation in Rats

Bone morphogenetic protein-9 (BMP-9) has been shown to be the most osteogenic BMP. Most of these experiments, however, involve an adenovirus-transfection strategy. Here, we used the scaffold-based strategy to study the bone forming ability of recombinant BMP-9 combined with vascular endothelial growth factor (VEGF). A robust, injectable, multicomponent-releasing scaffold in the form of a composite gel was developed by combining chitosan microparticles (MPs) with thermosensitive gel (MPs-gel). The MPs acted as the carriers for BMP-9 and the gel was loaded with VEGF. The developed gel consisted of hydrophobic chains of methyl cellulose (MC) and the cross-linked structures of alginate (Alg) and calcium. Gelation was achieved at physiological temperature and thus facilitated the injection and localization of MPs enabling an increased efficacy of incorporated growth factors at the target site. A release profile of incorporated growth factors over a two-week period showed higher release of VEGF at each time point compared to that of BMP-9. Human mesenchymal stem cells (hMSCs) encapsulated within the MPs-gel maintained their viability. BMP-9 enhanced the proliferation of hMSCs along the surface of MPs. Furthermore, BMP-9 potently induced the osteogenic differentiation of encapsulated hMSCs elucidated by the increased alkaline phosphatase (ALP) activity and the higher expression of ALP, collagen 1, and osteocalcin genes. In addition, in vivo experiments demonstrated that MPs-gel with the combination of BMP-9-VEGF could significantly enhance both subcutaneous and cranial bone formation (p < 0.05). Taken together, the results here strongly suggest that BMP-9-VEGF incorporated MPs-gel holds promise as an injectable bone tissue engineering platform.

Comparative investigation of porous nano-hydroxyapaptite/chitosan, nano-zirconia/chitosan and novel nano-calcium zirconate/chitosan composite scaffolds for their potential applications in bone regeneration

Zirconium (Zr) based bioceramic nanoparticles, as the filler material to chitosan (CS), for the development of composite scaffolds are less studied compared to hydroxyapatite nanoparticles. This is predominantly due to the biological similarity of nano-hydroxyapatite (nHA; Ca10(PO4)6(OH)2) with bone inorganic component. In this study, we compared the physical and biological properties of CS composite scaffolds hybridized with nHA, nano-zirconia (nZrO; ZrO2), and nano-calcium zirconate (nCZ; CaZrO3). For the first time in this study, the properties of CS-nCZ composite scaffolds have been reported. The porous composite scaffolds were developed using the freeze-drying technique. The compressive strength and modulus were in the range of 50-55 KPa and 0.75-0.95 MPa for composite scaffolds, significantly higher (p < 0.05), compared to CS alone scaffolds (28 KPa and 0.25 MPa) and were comparable among CS-nHA, CS-nZrO, and CS-nCZ scaffolds. Peak force quantitative nanomechanical mapping (PFQNM) using an atomic force microscope (AFM) showed that the Young's modulus of composite material was higher compared to only CS (p < 0.001), and the values were similar among the composite materials. One of the major issues in the use of Zr based bioceramic materials in bone tissue regeneration applications is their lower osteoblasts response. This study has shown that CS-nCZ supported higher proliferation of pre-osteoblasts compared to CS-nZrO and the spreading was more similar to that observed in CS-nHA scaffolds. Taken together, results show that the physical and biological properties, studied here, of CS composite with Zr based bio-ceramic was comparable with CS-nHA composite scaffolds and hence show the prospective of CS-nCZ for future bone tissue engineering applications.