The regulating effect of trace elements Si, Zn and Sr on mineralization of gelatin-hydroxyapatite electrospun fiber

Stereolithography of ceramic scaffolds for bone tissue regeneration: Influence of hydroxyapatite/silica ratio on mechanical properties

In this paper, the results obtained in the development of ceramic resin feedstock for stereolithography are shown. Hydroxyapatite and silica are used as source of ceramic. Hydroxyapatite is extracted from bovine bone, which enhances bioactivity of ceramic scaffold. The influence of hydroxyapatite amount in polymer-based slurry on the viscosity and printability of feedstock is explored. Hydroxyapatite and silica containing scaffolds are successfully obtained by stereolithography. Influence of hydroxyapatite/silica ratio on the bioactivity, biodegradability and mechanical properties of the scaffolds is also studied. It was observed that higher concentrations of hydroxyapatite led to improved mechanical strength of the scuffolds but increased viscosity of the slurry, affecting printability. Cell viability assays and cell visualization experiments indicated that the scaffolds not cause significant cell toxicity.

Gelatin-mediated gallium-doped SrHA composite coatings with sequential antimicrobial and osteogenic functions for infected bone defect repair

In this study, gallium- and gelatin-modified strontium-doped hydroxyapatite (SrHA-Gel-Ga) bilayer coatings were prepared on titanium substrates by electrodeposition and spin-coating techniques. The results showed that gallium and gelatin were uniformly doped into the SrHA coatings, which exhibited good hydrophilicity and bioactivity. Furthermore, SrHA-Gel-Ga demonstrated good antimicrobial properties against E. coli and S. aureus, especially S. aureus. The co-doping of Sr and gelatin in the coatings was effective in mitigating the cytotoxicity of Ga. SrHA-Gel-Ga was better able to promote the adhesion, proliferation and early differentiation of MC3T3-E1 cells. This study provides a new strategy for the development of anti-infective bone repair coatings.

A Novel Porous Butyryl Chitin-Animal Derived Hydroxyapatite Composite Scaffold for Cranial Bone Defect Repair

Bone defects, a common orthopedic problem in clinical practice, are a serious threat to human health. As alternative materials to autologous bone grafts, synthetic cell-free functionalized scaffolds have been the focus of recent research in designing scaffolds for bone tissue engineering. Butyryl chitin (BC) is a derivative of chitin (CT) with improved solubility. It has good biocompatibility, but few studies have investigated its use in bone repair. In this study, BC was successfully synthesized with a degree of substitution of 2.1. BC films were prepared using the cast film method and showed strong tensile strength (47.8 ± 4.54 N) and hydrophobicity (86.4 ± 2.46°), which was favorable for mineral deposition. An in vitro cytological assay confirmed the excellent cell attachment and cytocompatibility of the BC film; meanwhile, in vivo degradation indicated the good biocompatibility of BC. Hydroxyapatite (HA), extracted from bovine cancellous bone, had good cytocompatibility and osteogenic induction activity for the mouse osteoblast cell line MC3T3-E1. With the aim of combining the advantages of BC and HA, a BC-HA composite scaffold, with a good pore structure and mechanical strength, was prepared by physical mixing. Administered into skull defects of rats, the scaffolds showed perfect bone-binding performance and effective structural support, and significantly promoted the regeneration of new bone. These results prove that the BC-HA porous scaffold is a successful bone tissue engineering scaffold and has strong potential to be further developed as a substitute for bone transplantation.

Advances in osseointegration of biomimetic mineralized collagen and inorganic metal elements of natural bone for bone repair

At this stage, bone defects caused by trauma, infection, tumor, or congenital diseases are generally filled with autologous bone or allogeneic bone transplantation, but this treatment method has limited sources, potential disease transmission and other problems. Ideal bone-graft materials remain continuously explored, and bone defect reconstruction remains a significant challenge. Mineralized collagen prepared by bionic mineralization combining organic polymer collagen with inorganic mineral calcium phosphate can effectively imitate the composition and hierarchical structure of natural bone and has good application value in bone repair materials. Magnesium, strontium, zinc and other inorganic components not only can activate relevant signaling pathways to induce differentiation of osteogenic precursor cells but also stimulate other core biological processes of bone tissue growth and play an important role in natural bone growth, and bone repair and reconstruction. This study reviewed the advances in hydroxyapatite/collagen composite scaffolds and osseointegration with natural bone inorganic components, such as magnesium, strontium and zinc.

Fabrication of strontium carbonate-based composite bioceramics as potential bone regenerative biomaterials

Strontium carbonate (SrC) bioceramics are proposed as potential biomaterials to efficaciously repair the bone defects. However, the development of SrC bioceramics is restricted by their intrinsic low mechanical strength. In this study, SrC-based composite bioceramics (SrC-SrP) were fabricated by incorporating strontium-containing phosphate glass (SrP). The results indicated that aside from the main crystalline phase SrC, new compounds were generated in the SrC-SrP bioceramics. Incorporating 10 wt% SrP promoted densification, thus dramatically improving compressive strength of SrC-SrP bioceramics. The SrC-SrP bioceramics facilitated apatite precipitation on their surface, and sustainedly released strontium, phosphorus and sodium ions. Compared with the well-known β-tricalcium phosphate bioceramics, the SrC-SrP bioceramics with certain amounts of SrP enhanced proliferation, alkaline phosphatase activity and osteogenesis-related gene expressions of mouse bone mesenchymal stem cells. The SrC-SrP bioceramics with appropriate constituent can serve as novel bone regenerative biomaterials.

Extraction of natural hydroxyapatite for biomedical applications—A review

Hydroxyapatite has recently played a crucial role in the sustainable development of biomedical applications. Publications related to hydroxyapatite as filler for biopolymers have exhibited an increasing trend due to the expanding research output. Based on the latest publications, the authors reviewed the research trends regarding hydroxyapatite use in biomedical applications. Analysis of the Scopus database using the keywords ‘hydroxyapatite” and “biomedical applications” determined that 1,714 papers were produced between 2012 and 2021. The number of publications related to these keywords more than doubled between 2012 (99) and 2021 (247). The hydrothermal method, solid-state reactions, the sol-gel process, emulsion, micro-emulsion, and mostly chemical precipitation were used to produce synthetic hydroxyapatite. Meanwhile, calcination, alkaline hydrolysis, precipitation, hydrothermal, and a combination of these techniques were used in producing natural hydroxyapatite. Studies in the current literature reveal that shell-based animal sources have been frequently used as hydroxyapatite resources during investigations concerning biomedical applications, while calcination was the extraction method most often applied. Essential trace elements of fish bone, oyster shell, and eggshell were also found in hydroxyapatite powder. Abalone mussel shell and eggshell showed Ca/P ratios closer to the stoichiometric ratio due to the use of effective extraction methods such as manipulating aging time or stirring process parameters. This review should greatly assist by offering scientific insights to support all the recommended future research works, not only that associated with biomedical applications.

Optimizing the bio-degradability and biocompatibility of a biogenic collagen membrane through cross-linking and zinc-doped hydroxyapatite

Biogenic collagen membranes have been widely used as soft tissue barriers in guided bone regeneration (GBR) and guided tissue regeneration (GTR). Nevertheless, their clinical performance remains unsatisfactory because of their low mechanical strength and fast degradation rate in vivo. Although cross-linking with chemical agents is effective and reliable for prolonging the degradation time of collagen membranes, some adverse effects including potential cytotoxicity and undesirable tissue integration have been observed during this process. As a fundamental nutritional trace element, zinc plays an active role in promoting the growth of cells and regulating the degradation of the collagen matrix. Herein, a biogenic collagen membrane was cross-linked with glutaraldehyde-alendronate to prolong its degradation time. The physiochemical and biological properties were enhanced by the incorporation of zinc-doped nanohydroxyapatite (nZnHA), with the native structure of collagen preserved. Specifically, the cross-linking combined with the incorporation of 1% and 2% nZnHA seemed to endow the membrane with the most appropriate biocompatibility and tissue integration capability among the cross-linked membranes, as well as offering a degradation period of six weeks in a rat subcutaneous model. Thus, improving the clinical performance of biogenic collagen membranes by cross-linking together with the incorporation of nZnHA is a promising strategy for the improvement of biogenic collagen membranes. STATEMENT OF SIGNIFICANCE: The significance of this research includes.

3D Printed Strontium and Zinc Doped Hydroxyapatite Loaded PEEK for Craniomaxillofacial Implants

In this study, Strontium (Sr) and Zinc (Zn) doped-HA nanoparticles were synthesized and incorporated into polyetheretherketone (PEEK) up to 30 wt.% and processed by a novel approach i.e., fused deposition modelling (FDM) 3D printing for the production of patient specific cranial implants with improved bioactivity and the required mechanical performance. Filaments were produced via extrusion and subsequently 3D-printed using FDM. To further improve the bioactivity of the 3D-printed parts, the samples were dip-coated in polyethylene glycole-DOPA (PEG-DOPA) solution. The printing quality was influenced by filler loading, but was not significantly influenced by the nature of doped-HA. Hence, the printing conditions were optimized for each sample. Micro-CT and Scanning Electron Microscopy (SEM) showed a uniform distribution of bioceramic particles in PEEK. Although agglomeration of particles increased with increase in filler loadings. Differential Scanning Calorimetry (DSC) showed that the melting point and crystallinity of PEEK increased with an increase in doped-HA loading from 343 °C to 355 °C and 27.7% to 34.6%, respectively. Apatite formation was confirmed on the 3D-printed samples after immersion in simulated body fluid (SBF) for 7, 14 and 28 days via SEM, X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The tensile strength and impact strength decreased from 75 MPa to 51 MPa and 14 kJ/m2 to 4 kJ/m2, respectively, while Young’s modulus increased with increasing doped-HA content from. However, the tensile strengths of composites remained in the range of human cortical bone i.e., ≥50 MPa. In addition, there was a slight increase in mechanical strength after 28 days immersion which was attributed to apatite formation. Water contact angle showed that the hydrophilicity of the samples improved after coating the 3D-printed samples with PEG-DOPA. Hence, based on the results, the 3D-printed PEEK nanocomposites with 20 wt.% doped-HA is selected as the best candidate for the 3D-printing of craniomaxillofacial implants.