Enhanced Stability of Calcium Sulfate Scaffolds with 45S5 Bioglass for Bone Repair

Design and Manufacture of Bone Cements Based on Calcium Sulfate Hemihydrate and Mg, Sr-Doped Bioactive Glass

In the present study, a novel composite bone cement based on calcium sulfate hemihydrate (CSH) and Mg, Sr-containing bioactive glass (BG) as solid phase, and solution of chitosan as liquid phase were developed. The phase composition, morphology, setting time, injectability, viscosity, and cellular responses of the composites with various contents of BG (0, 10, 20, and 30 wt.%) were investigated. The pure calcium sulfate cement was set at approximately 180 min, whereas the setting time was drastically decreased to 6 min by replacing 30 wt.% glass powder for CSH in the cement solid phase. BG changed the microscopic morphology of the set cement and decreased the size and compaction of the precipitated gypsum phase. Replacing the CSH phase with BG increased injection force of the produced cement; however, all the cements were injected at a nearly constant force, lower than 20 N. The viscosity measurements in oscillatory mode determined the shear-thinning behavior of the pastes. Although the viscosity of the pastes increased with increasing BG content, it was influenced by the frequency extent. Pure calcium sulfate cement exhibited some transient cytotoxicity on human-derived bone mesenchymal stem cells and it was compensated by introducing BG phase. Moreover, BG improved the cell proliferation and mineralization of extracellular matrix as shown by calcein measurements. The results indicate the injectable composite cement comprising 70 wt.% CSH and 30 wt.% Mg, Sr-doped BG has better setting, mechanical and cellular behaviors and hence, is a potential candidate for bone repair, however more animal and human clinical evaluations are essential.

Effect of Platelet-Rich Plasma Addition on the Chemical Properties and Biological Activity of Calcium Sulfate Hemihydrate Bone Cement

Currently, platelet-rich plasma (PRP) is an attractive additive for bone repair materials. PRP could enhance the osteoconductive and osteoinductive of bone cement, as well as modulate the degradation rate of calcium sulfate hemihydrate (CSH). The focus of this study was to investigate the effect of different PRP ratios (P1: 20 vol%, P2: 40 vol%, and P3: 60 vol%) on the chemical properties and biological activity of bone cement. The injectability and compressive strength of the experimental group were significantly higher than those of the control. On the other hand, the addition of PRP decreased the crystal size of CSH and prolonged the degradation time. More importantly, the cell proliferation of L929 and MC3T3-E1 cells was promoted. Furthermore, qRT-PCR, alizarin red staining, and western blot analyses showed that the expressions of osteocalcin (OCN) and Runt-related transcription factor 2 (Runx2) genes and β-catenin protein were up-regulated, and mineralization of extracellular matrix was enhanced. Overall, this study provided insight into how to improve the biological activity of bone cement through PRP incorporation.

Heterogeneous distribution of shell matrix proteins in the pearl oyster prismatic layer

Shell formation in molluscan bivalves is regulated by organic matrices composed of biological macromolecules, but how these macromolecules assemble in vitro remains elusive. Prismatic layer in the pearl oyster Pinctada fucata consists of polygonal prisms enveloped by thick organic matrices. In this study, we found that the organic matrices were heterogeneously distributed, with highly acidic fractions (EDTA-soluble and EDTA-insoluble) embedded inside the prism columns, while basic EDTA-insoluble faction as inter-column framework enveloping the prisms. The intra-column matrix was enriched in aspartic acid whereas the inter-column matrix was enriched in glycine, tyrosine and phenylalanine. Moreover, the intra-column matrix contained sulfo group further contributing to its acidic property. Proteomics data showed that the intra-column proteins mainly consisted of acidic proteins, while some typical matrix proteins were absent. The absent matrix proteins such as shematrin family and KRMP family were highly basic and contained aromatic amino acids, suggesting that electric charge and hydrophobic effect might play a role in the matrix heterogeneity. Interestingly, chitin metabolism related proteins were abundant in the inter-column matrix, which may be involved in reconstructing the prism organic matrix. Overall, our study suggests that each single prism grew in an enclosed organic envelope and the organic matrix undergoes rearrangement, thus leading to the peculiar growth of the prismatic layer.

High toughness resorbable brushite-gypsum fiber-reinforced cements

The ideal bone substitute material should be mechanically strong, biocompatible with a resorption rate matching the rate of new bone formation. Brushite (dicalcium phosphate dihydrate) cement is a promising bone substitute material but with limited resorbability and mechanical properties. To improve the resorbability and mechanical performance of brushite cements, we incorporated gypsum (calcium sulfate dihydrate) and diazonium-treated polyglactin fibers which are well-known for their biocompatibility and bioresorbability. Here we show that by combining brushite and gypsum, we were able to fabricate biocompatible composite cements with high fracture toughness (0.47 MPa·m^1/2) and a resorption rate that matched the rate of new bone formation. Adding functionalized polyglactin fibers to this composite cement further improved the fracture toughness up to 1.00 MPa·m^1/2. XPS and SEM revealed that the improvement in fracture toughness is due to the strong interfacial bonding between the functionalized fibers and the cement matrix. This study shows that adding gypsum and functionalized polyglactin fibers to brushite cements results in composite biomaterials that combine high fracture toughness, resorbability, and biocompatibility, and have great potential for bone regeneration.

Repair of alveolar cleft bone defects by bone collagen particles combined with human umbilical cord mesenchymal stem cells in rabbit

Background

Alveolar cleft is a type of cleft lip and palate that seriously affects the physical and mental health of patients. In this study, a model of the alveolar cleft phenotype was established in rabbits to evaluate the effect of bone collagen particles combined with human umbilical cord mesenchymal stem cells (HUC-MSCs) on the repair of alveolar cleft bone defects.

Methods

A model of alveolar clefts in rabbits was established by removing the incisors on the left side of the upper jaw bone collagen particles combined with HUC-MSCs that were then implanted in the defect area. Blood biochemical analysis was performed 3 months after surgery. Skull tissues were harvested for gross observation, and micro-focus computerised tomography (micro-CT) analysis. Tissues were harvested for histological and immunohistochemical staining. The experiments were repeated 6 months after surgery.

Results

Bone collagen particles and HUC-MSCs showed good biocompatibility. Bone collagen particles combined with HUC-MSCs were markedly better at inducing bone repair and regeneration than bone collagen particles alone.

Conclusions

Combining HUC-MSCs with bone collagen particles provides a simple, rapid and suitable method to fill a bone defect site and treat of alveolar cleft bone defects.

Manipulation of the degradation behavior of calcium sulfate by the addition of bioglass

A bioactive calcium sulfate/glass composite was prepared using a sintering technique, and Ca–P–Si glass particles were prepared by spray pyrolysis. The glass exhibited bioactivity in terms of its ability to form apatite in a simulated body fluid. The glass was transformed into two crystallized phases, i.e., calcium phosphate and calcium silicate, respectively, during the heating stage. The presence of the crystallized phases retarded the densification of calcium sulfate. A high sintering temperature of 1200 °C was needed to prepare the composite. The increased addition of glass enhanced the strength and decreases the degradation rate of calcium sulfate. The new composite is not only degradable but also bioactive.

Calcium sulfate bone cements with nanoscaled silk fibroin as inducer

Both nanostructures and conformations of different protein/polysaccharide additives have critical influence on the performance of calcium sulfate (CS) bone cements. Silk fibroin (SF) as matrix and additives has been introduced to develop bone scaffolds and cements. Here, β-sheet-rich SF nanofibers (SFF) was used to tune the solidification of CS, achieving better mechanical and biological properties. The ratio of SFF was adjusted to further optimize CS functions. Compared to that regulated with natural silk fibers (NSF) and SF solutions (SFS), the SFF-induced CS showed smaller size and more filament structures. Better mechanical properties were achieved, suggesting the superiority of the SFF as the solidifying solution to combine with α-calcium sulfate hemihydrate (α-CSH) at the same liquid/solid (L/S) ratio. Scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, setting time, porosity, mechanical performance test, degradation performance test, and water resistance test were used to demonstrate the properties of this bone repair cement. Cell culture experiments in vitro was used to evaluate the biocompatibility of this composited material. In conclusion, the results demonstrated that nanofibers was a better form of SF in the modification of CSH cement. And the research conducted in this article on improving the mechanical and biological properties of CSH would supported the reference for later clinical experiments. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2611-2619, 2019.

Functionalization of Calcium Sulfate/Bioglass Scaffolds with Zinc Oxide Whisker

There are urgent demands for satisfactory antibacterial activity and mechanical properties of bone scaffolds. In this study, zinc oxide whisker (ZnOw) was introduced into calcium sulfate/bioglass scaffolds. Antimicrobial behavior was analyzed using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results showed that the scaffolds presented a strong antibacterial activity after introducing ZnOw, due to the antibacterial factors released from the degradation of ZnO. Moreover, ZnOw was also found to have a distinct reinforcing effect on mechanical properties. This was ascribed to whisker pull-out, crack bridging, crack deflection, crack branching and other toughening mechanisms. In addition, the cell culture experiments showed that the scaffolds with ZnOw had a good biocompatibility.