A surface-engineered multifunctional TiO2 based nano-layer simultaneously elevates the corrosion resistance, osteoconductivity and antimicrobial property of a magnesium alloy

Recent Advancements in Bone Tissue Engineering: Integrating Smart Scaffold Technologies and Bio-Responsive Systems for Enhanced Regeneration

In exploring the challenges of bone repair and regeneration, this review evaluates the potential of bone tissue engineering (BTE) as a viable alternative to traditional methods, such as autografts and allografts. Key developments in biomaterials and scaffold fabrication techniques, such as additive manufacturing and cell and bioactive molecule-laden scaffolds, are discussed, along with the integration of bio-responsive scaffolds, which can respond to physical and chemical stimuli. These advancements collectively aim to mimic the natural microenvironment of bone, thereby enhancing osteogenesis and facilitating the formation of new tissue. Through a comprehensive combination of in vitro and in vivo studies, we scrutinize the biocompatibility, osteoinductivity, and osteoconductivity of these engineered scaffolds, as well as their interactions with critical cellular players in bone healing processes. Findings from scaffold fabrication techniques and bio-responsive scaffolds indicate that incorporating nanostructured materials and bioactive compounds is particularly effective in promoting the recruitment and differentiation of osteoprogenitor cells. The therapeutic potential of these advanced biomaterials in clinical settings is widely recognized and the paper advocates continued research into multi-responsive scaffold systems.

Attributes of Nanomaterials and Nanotopographies for Improved Bone Tissue Engineering and Regeneration

Bone tissue engineering (BTE) is a multidisciplinary area that can solve the limitation of conventional grafting methods by developing viable and biocompatible bone replacements. The three essential components of BTE, i.e., Scaffold material and Cells and Growth factors altogether, facilitate support and guide for bone formation, differentiation of the bone tissues, and enhancement in the cellular activities and bone regeneration. However, there is a scarcity of the appropriate materials that can match the mechanical property as well as functional similarity to native tissue, considering the bone as hard tissue. In such scenarios, nanotechnology can be leveraged upon to achieve the desired aspects of BTE, and that is the key point of this review article. This review article examines the significant areas of nanotechnology research that have an impact on regeneration of bone: (a) scaffold with nanomaterials helps to enhance physicochemical interactions, biocompatibility, mechanical stability, and attachment; (b) nanoparticle-based approaches for delivering bioactive chemicals, growth factors, and genetic material. The article begins with the introduction of components and healing mechanisms of bone and the factors associated with them. The focus of this article is on the various nanotopographies that are now being used in scaffold formation, by describing how they are made, and how these nanotopographies affect the immune system and potential underlying mechanisms. The advantages of 4D bioprinting in BTE by using nanoink have also been mentioned. Additionally, we have investigated the importance of an in silico approach for finding the interaction between drugs and their related receptors, which can help to formulate suitable systems for delivery. This review emphasizes the role of nanoscale approach and how it helps to increase the efficacy of parameters of scaffold as well as drug delivery system for tissue engineering and bone regeneration.

Composite Nanocoatings of Biomedical Magnesium Alloy Implants: Advantages, Mechanisms, and Design Strategies

The rapid degradation of magnesium (Mg) alloy implants erodes mechanical performance and interfacial bioactivity, thereby limiting their clinical utility. Surface modification is among the solutions to improve corrosion resistance and bioefficacy of Mg alloys. Novel composite coatings that incorporate nanostructures create new opportunities for their expanded use. Particle size dominance and impermeability may increase corrosion resistance and thereby prolong implant service time. Nanoparticles with specific biological effects may be released into the peri-implant microenvironment during the degradation of coatings to promote healing. Composite nanocoatings provide nanoscale surfaces to promote cell adhesion and proliferation. Nanoparticles may activate cellular signaling pathways, while those with porous or core-shell structures may carry antibacterial or immunomodulatory drugs. Composite nanocoatings may promote vascular reendothelialization and osteogenesis, attenuate inflammation, and inhibit bacterial growth, thus increasing their applicability in complex clinical microenvironments such as those of atherosclerosis and open fractures. This review combines the physicochemical properties and biological efficiency of Mg-based alloy biomedical implants to summarize the advantages of composite nanocoatings, analyzes their mechanisms of action, and proposes design and construction strategies, with the purpose of providing a reference for promoting the clinical application of Mg alloy implants and to further the design of nanocoatings.

Antifouling and antibacterial performance evaluation of polyethersulfone membranes modified with AZ63 alloy

Antibacterial membranes have attracted researchers' interest in recent years as a possible approach for dealing with biofouling on the membrane surface. This research aims to see if blending AZ63 Mg alloy into a polyethersulphone (PES) membrane can improve antifouling and separation properties. The composite membranes' pure water flux continued to increase from pristine PES to PES/AZ63 2.00 wt%. The results showed that PES/AZ63 2.00 wt% membrane supplied the highest permeate flux of E. coli. The steady-state fluxes of AZ63 composite membranes were 113.24, 104.38 and 44.79 L/m²h for PES/AZ63 2.00 wt%, 1.00 wt%, and 0.50 wt%, respectively. The enhanced biological activity of AZ63 was studied based on antioxidant activity, DNA cleavage, antimicrobial, anti-biofilm, bacterial viability inhibition and photodynamic antimicrobial therapy studies. The maximum DPPH scavenging activity was determined as 81.25% with AZ63. AZ63 indicated good chemical nuclease activity and also showed moderate antimicrobial activity against studied strains. The highest biofilm inhibition of AZ63 was 83.25% and 71.63% towards P. aeruginosa and S. aureus, respectively. The cell viability inhibition activity of AZ63 was found as 96.34% against E. coli. The photodynamic antimicrobial therapy results displayed that AZ63 demonstrated 100% bacterial inhibition when using E. coli.

An osteogenic magnesium alloy with improved corrosion resistance, antibacterial, and mechanical properties for orthopedic applications

The aim of this study was to develop a novel biodegradable magnesium (Mg) alloy for bone implant applications. We used scandium (Sc; 2 wt %) and strontium (Sr; 2 wt %) as alloying elements due to their high biocompatibility, antibacterial efficacy, osteogenesis, and protective effects against corrosion. In the present work, we also examined the effect of a heat treatment process on the properties of the Mg-Sc-Sr alloy. Alloys were manufactured using a metal casting process followed by heat treatment. The microstructure, corrosion, mechanical properties, antibacterial activity, and osteogenic activity of the alloy were assessed in vitro. The results showed that the incorporation of Sc and Sr elements controlled the corrosion, reduced the hydrogen generation, and enhanced mechanical properties. Furthermore, alloying with Sc and Sr demonstrated a significantly enhanced antibacterial activity and decreased biofilm formation compared to control Mg. Also, culturing Mg-Sc-Sr alloy with human bone marrow-derived mesenchymal stromal cells showed a high degree of biocompatibility (>90% live cells) and a significant increase in osteoblastic differentiation in vitro shown by Alizarin red staining and alkaline phosphatase activity. Based on these results, the Mg-Sc-Sr alloy heat-treated at 400°C displayed optimal mechanical properties, corrosion rate, antibacterial efficacy, and osteoinductivity. These characteristics make the Mg-Sc-Sr alloy a promising candidate for biodegradable orthopedic implants in the fixation of bone fractures such as bone plate-screws or intramedullary nails.

Biodegradable Mg-Sc-Sr Alloy Improves Osteogenesis and Angiogenesis to Accelerate Bone Defect Restoration

Magnesium (Mg) and its alloys are considered to be biodegradable metallic biomaterials for potential orthopedic implants. While the osteogenic properties of Mg alloys have been widely studied, few reports focused on developing a bifunctional Mg implant with osteogenic and angiogenic properties. Herein, a Mg-Sc-Sr alloy was developed, and this alloy's angiogenesis and osteogenesis effects were evaluated in vitro for the first time. X-ray Fluorescence (XRF), X-ray diffraction (XRD), and metallography images were used to evaluate the microstructure of the developed Mg-Sc-Sr alloy. Human umbilical vein/vascular endothelial cells (HUVECs) were used to evaluate the angiogenic character of the prepared Mg-Sc-Sr alloy. A mix of human bone-marrow-derived mesenchymal stromal cells (hBM-MSCs) and HUVEC cell cultures were used to assess the osteogenesis-stimulating effect of Mg-Sc-Sr alloy through alkaline phosphatase (ALP) and Von Kossa staining. Higher ALP activity and the number of calcified nodules (27% increase) were obtained for the Mg-Sc-Sr-treated groups compared to Mg-treated groups. In addition, higher VEGF expression (45.5% increase), tube length (80.8% increase), and number of meshes (37.9% increase) were observed. The Mg-Sc-Sr alloy showed significantly higher angiogenesis and osteogenic differentiation than pure Mg and the control group, suggesting such a composition as a promising candidate in bone implants.

A review on magnesium alloys for biomedical applications

Magnesium (Mg) and Mg alloys are considered as potential candidates for biomedical applications because of their high specific strength, low density, and elastic modulus, degradability, good biocompatibility and biomechanical compatibility. However, the rapid corrosion rate of Mg alloys results in premature loss of mechanical integrity, limiting their clinical application in load-bearing parts. Besides, the low strength of Mg alloys restricts their further application. Thus, it is essential to understand the characteristics and influencing factors of mechanical and corrosion behavior, as well as the methods to improve the mechanical performances and corrosion resistance of Mg alloys. This paper reviews the recent progress in elucidating the corrosion mechanism, optimizing the composition, and microstructure, enhancing the mechanical performances, and controlling the degradation rate of Mg alloys. In particular, the research progress of surface modification technology of Mg alloys is emphasized. Finally, the development direction of biomedical Mg alloys in the future is prospected.

Effects of Zinc, Magnesium, and Iron Ions on Bone Tissue Engineering

Large-sized bone defects are a great challenge in clinics and considerably impair the quality of patients' daily life. Tissue engineering strategies using cells, scaffolds, and bioactive molecules to regulate the microenvironment in bone regeneration is a promising approach. Zinc, magnesium, and iron ions are natural elements in bone tissue and participate in many physiological processes of bone metabolism and therefore have great potential for bone tissue engineering and regeneration. In this review, we performed a systematic analysis on the effects of zinc, magnesium, and iron ions in bone tissue engineering. We focus on the role of these ions in properties of scaffolds (mechanical strength, degradation, osteogenesis, antibacterial properties, etc.). We hope that our summary of the current research achievements and our notifications of potential strategies to improve the effects of zinc, magnesium, and iron ions in scaffolds for bone repair and regeneration will find new inspiration and breakthroughs to inspire future research.

Biodegradable Magnesium Biomaterials-Road to the Clinic

In recent decades, we have witnessed radical changes in the use of permanent biomaterials. The intrinsic ability of magnesium (Mg) and its alloys to degrade without releasing toxic degradation products has led to a vast range of applications in the biomedical field, including cardiovascular stents, musculoskeletal, and orthopedic applications. With the use of biodegradable Mg biomaterials, patients would not suffer second surgery and surgical pain anymore. Be that as it may, the main drawbacks of these biomaterials are the high corrosion rate and unexpected degradation in physiological environments. Since biodegradable Mg-based implants are expected to show controllable degradation and match the requirements of specific applications, various techniques, such as designing a magnesium alloy and modifying the surface characteristics, are employed to tailor the degradation rate. In this paper, some fundamentals and particular aspects of magnesium degradation in physiological environments are summarized, and approaches to control the degradation behavior of Mg-based biomaterials are presented.

Construction of a magnesium hydroxide/graphene oxide/hydroxyapatite composite coating on Mg–Ca–Zn–Ag alloy to inhibit bacterial infection and promote bone regeneration

The improved corrosion resistance, osteogenic activity, and antibacterial ability are the key factors for promoting the large-scale clinical application of magnesium (Mg)-based implants. In the present study, a novel nanocomposite coating composed of inner magnesium hydroxide, middle graphene oxide, and outer hydroxyapatite (Mg(OH)₂/GO/HA) is constructed on the surface of Mg-0.8Ca–5Zn-1.5Ag by a combined strategy of hydrothermal treatment, electrophoretic deposition, and electrochemical deposition. The results of material characterization and electrochemical corrosion test showed that all the three coatings have high bonding strength, hydrophilicity and corrosion resistance. In vitro studies show that Mg(OH)₂ indeed improves the antibacterial activity of the substrate. The next GO and GO/HA coating procedures both promote the osteogenic differentiation of MC3T3-E1 cells and show no harm to the antibacterial activity of Mg(OH)₂ coating, but the latter exhibits the best promoting effect. In vivo studies demonstrate that the Mg alloy with the composite coating not only ameliorates osteolysis induced by bacterial invasion but also promotes bone regeneration under both normal and infected conditions. The current study provides a promising surface modification strategy for developing multifunctional Mg-based implants with good corrosion resistance, antibacterial ability and osteogenic activity to enlarge their biomedical applications.

•

A Mg(OH)₂/GO/HA composite coating with high bonding strength was constructed on the surface of Mg–Ca–Zn–Ag alloy.

•

The outer HA layer with excellent osteogenic activity recovered the high corrosion resistance of inner Mg(OH)₂ layer.

•

The Mg(OH)₂/GO/HA composite coating promoted new bone regeneration significantly under both normal and infected conditions.

Biodegradable magnesium-based biomaterials: An overview of challenges and opportunities

As promising biodegradable materials with nontoxic degradation products, magnesium (Mg) and its alloys have received more and more attention in the biomedical field very recently. Having excellent biocompatibility and unique mechanical properties, magnesium-based alloys currently cover a broad range of applications in the biomedical field. The use of Mg-based biomedical devices eliminates the need for biomaterial removal surgery after the healing process and reduces adverse effects induced by the implantation of permanent biomaterials. However, the high corrosion rate of Mg-based implants leads to unexpected degradation, structural failure, hydrogen evolution, alkalization, and cytotoxicity. To overcome these limitations, alloying Mg with suitable alloying elements and surface treatment come highly recommended. In this area, open questions remain on the behavior of Mg-based biomaterials in the human body and the effects of different factors that have resulted in these challenges. In addition to that, many techniques are yet to be verified to turn these challenges into opportunities. Accordingly, this article aims to review major challenges and opportunities for Mg-based biomaterials to minimize the challenges for the development of novel biomaterials made of Mg and its alloys.

In vitro and in vivo antibacterial performance of Zr & O PIII magnesium alloys with high concentration of oxygen vacancies

The effects of dual Zr and O plasma immersion ion implantation (Zr & O PIII) on antibacterial properties of ZK60 Mg alloys are systematically investigated. The results show that a hydrophobic, smooth, and ZrO₂-containing graded film is formed. Electrochemical assessment shows that the corrosion rate of the plasma-treated Mg alloy decreases and the decreased degradation rate is attributed to the protection rendered by the surface oxide. In vitro and in vivo antibacterial tests reveal Zr & O PIII ZK60 presents higher antibacterial rate compared to Zr PIII ZK60 and untreated control. The hydrophobic and smooth surface suppresses bacterial adhesion. High concentration of oxygen vacancies in the surface films are determined by X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS) and electron paramagnetic resonance (EPR) and involved in the production of reactive oxygen species (ROS). The higher level of ROS expression inhibits biofilm formation by down-regulating the expression of icaADBC genes but up-regulating the expression of icaR gene. In addition, Zr & O PIII improves cell viability and initial cell adhesion confirming good cytocompatibility. Dual Zr & O PIII is a simple and practical means to expedite clinical acceptance of biodegradable magnesium alloys.

•

A ZrO₂-containing graded film with high concentration of oxygen vacancies was formed via PIII.

•

S. aureus adhesion was suppressed due to enhanced hydrophobicity and decreased roughness.

•

High concentration of oxygen vacancies lead to the upregulation of ROS expression.

•

ROS mediates biofilm-associated genes expression to inhibit biofilm formation in vitro and in vivo.

Regulation of extracellular bioactive cations in bone tissue microenvironment induces favorable osteoimmune conditions to accelerate in situ bone regeneration

The design of orthopedic biomaterials has gradually shifted from “immune-friendly” to “immunomodulatory,” in which the biomaterials are able to modulate the inflammatory response via macrophage polarization in a local immune microenvironment that favors osteogenesis and implant-to-bone osseointegration. Despite the well-known effects of bioactive metallic ions on osteogenesis, how extracellular metallic ions manipulate immune cells in bone tissue microenvironments toward osteogenesis and subsequent bone formation has rarely been studied. Herein, we investigate the osteoimmunomodulatory effect of an extracellular bioactive cation (Mg²⁺) in the bone tissue microenvironment using custom-made poly lactic-co-glycolic acid (PLGA)/MgO-alendronate microspheres that endow controllable release of magnesium ions. The results suggest that the Mg²⁺-controlled tissue microenvironment can effectively induce macrophage polarization from the M0 to M2 phenotype via the enhancement of anti-inflammatory (IL-10) and pro-osteogenic (BMP-2 and TGF-β1) cytokines production. It also generates a favorable osteoimmune microenvironment that facilitates the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. The in vivo results further verify that a large amount of bony tissue, with comparable bone mineral density and mechanical properties, has been generated at an early post-surgical stage in rat intramedullary bone defect models. This study demonstrates that the concept of in situ immunomodulated osteogenesis can be realized in a controlled magnesium tissue microenvironment.

•

Controlled release of Mg²⁺ was achieved by the microfluidic electrosprayed PLGA/MgO-alendronate microspheres.

•

PLGA/MgO-alendronate microspheres with satisfied osteoimmunomodulatory properties accelerated bone regeneration in vivo.

•

Extracellular Mg²⁺ induced macrophage switch to M2 phenotype with enhanced expressions of IL-10, BMP-2 and TGF-β1.

•

Osteoimmune microenvironment favourably upregulated the osteogenic expressions of BMSCs.

Tissue Engineering and Regenerative Medicine: Achievements, Future, and Sustainability in Asia

Exploring innovative solutions to improve the healthcare of the aging and diseased population continues to be a global challenge. Among a number of strategies toward this goal, tissue engineering and regenerative medicine (TERM) has gradually evolved into a promising approach to meet future needs of patients. TERM has recently received increasing attention in Asia, as evidenced by the markedly increased number of researchers, publications, clinical trials, and translational products. This review aims to give a brief overview of TERM development in Asia over the last decade by highlighting some of the important advances in this field and featuring major achievements of representative research groups. The development of novel biomaterials and enabling technologies, identification of new cell sources, and applications of TERM in various tissues are briefly introduced. Finally, the achievement of TERM in Asia, including important publications, representative discoveries, clinical trials, and examples of commercial products will be introduced. Discussion on current limitations and future directions in this hot topic will also be provided.