Customized Borosilicate Bioglass Scaffolds With Excellent Biodegradation and Osteogenesis for Mandible Reconstruction

[Research progress on biocomposites based on bioactive glass]

Bioactive glass (BG) has been widely used in the preparation of artificial bone scaffolds due to its excellent biological properties and non-cytotoxicity, which can promote bone and soft tissue regeneration. However, due to the brittleness, poor mechanical strength, easy agglomeration and uncontrollable structure of glass material, its application in various fields is limited. In this regard, most current researches mainly focus on mixing BG with organic or inorganic materials by freeze-drying method, sol-gel method, etc., to improve its mechanical properties and brittleness, so as to increase its clinical application and expand its application field. This review introduces the combination of BG with natural organic materials, metallic materials and non-metallic materials, and demonstrates the latest technology and future prospects of BG composite materials through the development of scaffolds, injectable fillers, membranes, hydrogels and coatings. The previous studies show that the addition of BG improves the mechanical properties, biological activity and regeneration potential of the composites, and broadens the application of BG in the field of bone tissue engineering. By reviewing the recent BG researches on bone regeneration, the research potential of new materials is demonstrated, in order to provide a reference for future related research.

A Review of the Application of Natural and Synthetic Scaffolds in Bone Regeneration

The management of bone defects is complicated by the presence of clinical conditions, such as critical-sized defects created by high-energy trauma, tumour resection, infection, and skeletal abnormalities, whereby the bone regeneration capacity is compromised. A bone scaffold is a three-dimensional structure matrix serving as a template to be implanted into the defects to promote vascularisation, growth factor recruitment, osteogenesis, osteoconduction, and mechanical support. This review aims to summarise the types and applications of natural and synthetic scaffolds currently adopted in bone tissue engineering. The merits and caveats of natural and synthetic scaffolds will be discussed. A naturally derived bone scaffold offers a microenvironment closer to in vivo conditions after decellularisation and demineralisation, exhibiting excellent bioactivity, biocompatibility, and osteogenic properties. Meanwhile, an artificially produced bone scaffold allows for scalability and consistency with minimal risk of disease transmission. The combination of different materials to form scaffolds, along with bone cell seeding, biochemical cue incorporation, and bioactive molecule functionalisation, can provide additional or improved scaffold properties, allowing for a faster bone repair rate in bone injuries. This is the direction for future research in the field of bone growth and repair.

Application of laser on enamel surface with three types of bioactive glasses-based resin infiltrants: An in vitro study

OBJECTIVE

The study aimed to evaluate and compare the surface micro-hardness, roughness, color, and morphology of enamel after Er,Cr:YSGG laser irradiation, followed by application of three types of bioactive glasses-based resin infiltrants, and the samples groups were challenged with the pH cycle.

METHODOLOGY

Experimental photoactivated resin infiltrants were synthesized using dimethacrylate resins, whereby three different types of bioactive glasses (BGs), i.e., 45S5, fluoridated-BG (F-BG), and borosilicate-BG (B-BG), were incorporated into the resin system. Initially, white spot lesions were created artificially on the toosth enamel surface, then irradiated with Er,Cr:YSGG laser. Then, the resin-only and BG-based resins were infiltrated on the enamel surface. All samples were pH challenged for 14 days, and the micro-hardness, surface roughness, surface morphology, and color stability (ΔE) analyses were conducted before and after the 14 days pH challenge.

RESULTS

After laser irradiation, the micro-hardness was significantly high with 45S5 group compared to resin-only (p = 0.021), F-BG (p = 0.042), and B-BG (p = 0.001) groups. After the pH challenge, the micro-hardness values for all groups were reduced significantly (p ≤ 0.05). The surface roughness was least with the resin-only group and showed a non-significant difference with F-BG (p = 0.34) and significant differences with both B-BG (p = 0.005), and 45S5 (p = 0.010) groups. After the pH cycle, the roughness of all groups was increased significantly (p ≤ 0.05), except B-BG group showed a non-significant difference (p = 0.528). The B-BG group showed significantly high ΔE between day 0 and baseline compared to resin-only (p = 0.0008), F-BG (p = 0.017), and 45S5 (p = 0.029), whereas between day 14 and baseline, the lowest ΔE value was observed for B-BG (14.2 ± 2.10) and maximum for the resin-only (20.57 ± 2.47) group. The SEM images showed pitting on the surface of all resin infiltrant groups after 14 days of pH challenge.

CONCLUSION

The morphological difference was observed after the laser irradiation on the enamel surface. The differences in micro-hardness, surface roughness, and color were observed after the application of experimental resin infiltrants and significant differences were observed after the pH challenge.

ZnO nanoparticle modified chitosan/borosilicate bioglass composite scaffold for inhibiting bacterial infection and promoting bone regeneration

The treatment of implant-associated bone infection remains a significant clinical challenge. However, bone scaffolds with antimicrobial activity and osteoinductive properties can prevent these infections and improve clinical outcomes. In this study, borosilicate bioglass and chitosan composite scaffolds were prepared, and then the surface was modified with nano-zinc oxide. In vitro and in vivo experiments showed that the chitosan/borosilicate bioglass scaffolds have good degradation and osteogenic properties, while the oxidized Zinc scaffolds have better antibacterial properties.

Research on the osteogenesis and biosafety of ECM–Loaded 3D–Printed Gel/SA/58sBG scaffolds

Employing scaffolds containing cell–derived extracellular matrix (ECM) as an alternative strategy for the regeneration of bone defects has shown prominent advantages. Here, gelatin (Gel), sodium alginate (SA) and 58s bioactive glass (58sBG) were incorporated into deionized water to form ink, which was further fabricated into composite scaffolds by the 3D printing technique. Then, rat aortic endothelial cells (RAOECs) or rat bone mesenchymal stem cells (RBMSCs) were seeded on the scaffolds. After decellularization, two kinds of ECM–loaded scaffolds (RAOECs–ECM scaffold and RBMSCs–ECM scaffold) were obtained. The morphological characteristics of the scaffolds were assessed meticulously by scanning electron microscopy (SEM). In addition, the effects of scaffolds on the proliferation, adhesion, and osteogenic and angiogenic differentiation of RBMSCs were evaluated by Calcein AM staining and reverse transcription polymerase chain reaction (RT–PCR). In vivo, full–thickness bone defects with a diameter of 5 mm were made in the mandibles of Sprague–Dawley (SD) rats to assess the bone regeneration ability and biosafety of the scaffolds at 4, 8 and 16 weeks. The osteogenic and angiogenic potential of the scaffolds were investigated by microcomputed tomography (Micro–CT) and histological analysis. The biosafety of the scaffolds was evaluated by blood biochemical indices and histological staining of the liver, kidney and cerebrum. The results showed that the ECM–loaded scaffolds were successfully prepared, exhibiting interconnected pores and a gel–like ECM distributed on their surfaces. Consistently, in vitro experiments demonstrated that the scaffolds displayed favourable cytocompatibility. In vitro osteogenic differentiation studies showed that scaffolds coated with ECM could significantly increase the expression of osteogenic and angiogenic genes. In addition, the results from mandibular defect repair in vivo revealed that the ECM–loaded scaffolds effectively promoted the healing of bone defects when compared to the pure scaffold. Overall, these findings demonstrate that both RAOECs–ECM scaffold and RBMSCs–ECM scaffold can greatly enhance bone formation with good biocompatibility and thus have potential for clinical application in bone regeneration.

In Vivo Application of Silica-Derived Inks for Bone Tissue Engineering: A 10-Year Systematic Review

As the need for efficient, sustainable, customizable, handy and affordable substitute materials for bone repair is critical, this systematic review aimed to assess the use and outcomes of silica-derived inks to promote in vivo bone regeneration. An algorithmic selection of articles was performed following the PRISMA guidelines and PICO method. After the initial selection, 51 articles were included. Silicon in ink formulations was mostly found to be in either the native material, but associated with a secondary role, or to be a crucial additive element used to dope an existing material. The inks and materials presented here were essentially extrusion-based 3D-printed (80%), and, overall, the most investigated animal model was the rabbit (65%) with a femoral defect (51%). Quality (ARRIVE 2.0) and risk of bias (SYRCLE) assessments outlined that although a large majority of ARRIVE items were “reported”, most risks of bias were left “unclear” due to a lack of precise information. Almost all studies, despite a broad range of strategies and formulations, reported their silica-derived material to improve bone regeneration. The rising number of publications over the past few years highlights Si as a leverage element for bone tissue engineering to closely consider in the future.

Development of a borosilicate bioactive glass scaffold incorporating calcitonin gene-related peptide for tissue engineering

Protein delivery and release from synthetic scaffold materials are major challenges within the field of bone tissue engineering. In this study, 13-93B1.5 borosilicate bioactive glass (BSG) base paste was 3D printed to produce BSG-based scaffolds with high porosity (59.85 ± 6.04%) and large pore sizes (350-400 μm) for functionalization with a sodium alginate (SA)/calcitonin gene-related peptide (CGRP) hydrogel mixture. SA/CGRP hydrogel was uniformly filled into the interconnected pores of 3D printed BSG constructs to produce BSG-SA/CGRP scaffolds which were subject to bioactivity and biocompatibility analysis. BSG scaffolds filled with SA hydrogel underwent dissolution in simulated body fluid (SBF), resulting in the precipitation of hydroxyapatite (HA) on the borosilicate glass evidenced by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Around 90% of CGRP was released from scaffolds after 7 days of immersion in SBF, reaching a final released concentration of 893.00 ± 63.30 ng/mL. Cellular adhesion, proliferation, and differentiation of human bone marrow mesenchymal stem cells (HBMSCs) cultured with BSG-SA/CGRP scaffolds revealed improved biocompatibility and osteogenic capabilities compared with BSG-SA scaffolds in the absence of CGRP. When subcutaneously implanted in rat models, BSG-SA/CGRP scaffolds induced low localized inflammation without causing bodily harm in vivo. Findings revealed that bioactive glass scaffolds incorporating CGRP met the scaffold requirements for bone regeneration and that the addition of CGRP promoted osteogenic differentiation where it may potentially be utilized for future regenerative applications.

Clinically relevant preclinical animal models for testing novel cranio-maxillofacial bone 3D-printed biomaterials

Bone tissue engineering is a rapidly developing field with potential for the regeneration of craniomaxillofacial (CMF) bones, with 3D printing being a suitable fabrication tool for patient‐specific implants. The CMF region includes a variety of different bones with distinct functions. The clinical implementation of tissue engineering concepts is currently poor, likely due to multiple reasons including the complexity of the CMF anatomy and biology, and the limited relevance of the currently used preclinical models. The ‘recapitulation of a human disease’ is a core requisite of preclinical animal models, but this aspect is often neglected, with a vast majority of studies failing to identify the specific clinical indication they are targeting and/or the rationale for choosing one animal model over another. Currently, there are no suitable guidelines that propose the most appropriate animal model to address a specific CMF pathology and no standards are established to test the efficacy of biomaterials or tissue engineered constructs in the CMF field. This review reports the current clinical scenario of CMF reconstruction, then discusses the numerous limitations of currently used preclinical animal models employed for validating 3D‐printed tissue engineered constructs and the need to reduce animal work that does not address a specific clinical question. We will highlight critical research aspects to consider, to pave a clinically driven path for the development of new tissue engineered materials for CMF reconstruction.

Modifying a 3D-Printed Ti6Al4V Implant with Polydopamine Coating to Improve BMSCs Growth, Osteogenic Differentiation, and In Situ Osseointegration In Vivo

Nowadays, 3D printing technology has been applied in dentistry to fabricate customized implants. However, the biological performance is unsatisfactory. Polydopamine (PDA) has been used to immobilize bioactive agents on implant surfaces to endow them with multiple properties, such as anti-infection and pro-osteogenesis, benefiting rapid osseointegration. Herein, we fabricated a PDA coating on a 3D-printed implant surface (3D-PDA) via the in situ polymerization method. Then the 3D-PDA implants' pro-osteogenesis capacity and the osseointegration performance were evaluated in comparison with the 3D group. The in vitro results revealed that the PDA coating modification increased the hydrophilicity of the implants, promoting the improvement of the adhesion, propagation, and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the 3D-PDA implant improved osteointegration performance in vivo. The present study suggested that PDA coating might be a feasible strategy to optimize 3D-printed implant surfaces, making a preliminary research basis for the subsequent work to immobilize bioactive factors on the 3D-printed implant surface.

Bioactive Glass—An Extensive Study of the Preparation and Coating Methods

Diseases or complications that are caused by bone tissue damage affect millions of patients every year. Orthopedic and dental implants have become important treatment options for replacing and repairing missing or damaged parts of bones and teeth. In order to use a material in the manufacture of implants, the material must meet several requirements, such as mechanical stability, elasticity, biocompatibility, hydrophilicity, corrosion resistance, and non-toxicity. In the 1970s, a biocompatible glassy material called bioactive glass was discovered. At a later time, several glass materials with similar properties were developed. This material has a big potential to be used in formulating medical devices, but its fragility is an important disadvantage. The use of bioactive glasses in the form of coatings on metal substrates allows the combination of the mechanical hardness of the metal and the biocompatibility of the bioactive glass. In this review, an extensive study of the literature was conducted regarding the preparation methods of bioactive glass and the different techniques of coating on various substrates, such as stainless steel, titanium, and their alloys. Furthermore, the main doping agents that can be used to impart special properties to the bioactive glass coatings are described.

Bioactive Glass Applications: A Literature Review of Human Clinical Trials

The use of bioactive glasses in dentistry, reconstructive surgery, and in the treatment of infections can be considered broadly beneficial based on the emerging literature about the potential bioactivity and biocompatibility of these materials, particularly with reference to Bioglass^® 45S5, BonAlive^® and 19-93B3 bioactive glasses. Several investigations have been performed (i) to obtain bioactive glasses in different forms, such as bulk materials, powders, composites, and porous scaffolds and (ii) to investigate their possible applications in the biomedical field. Although in vivo studies in animals provide us with an initial insight into the biological performance of these systems and represent an unavoidable phase to be performed before clinical trials, only clinical studies can demonstrate the behavior of these materials in the complex physiological human environment. This paper aims to carefully review the main published investigations dealing with clinical trials in order to better understand the performance of bioactive glasses, evaluate challenges, and provide an essential source of information for the tailoring of their design in future applications. Finally, the paper highlights the need for further research and for specific studies intended to assess the effect of some specific dissolution products from bioactive glasses, focusing on their osteogenic and angiogenic potential.