In vivo degradation and bone formation behaviors of hydroxyapatite-coated Mg alloys in rat femur

Research Progress in Medical Biomaterials for Bone Infections

Bone infection is a debilitating condition characterized by inflammation of the bone and its marrow. It poses significant challenges in clinical practice due to its recalcitrant nature and difficulty in eradicating the infecting microorganisms. Recent advancements in the field of medical biomaterials have shown hope in the treatment of bone infections. This article reviews the research progress of medical biomaterials for anti-osteomyelitis in recent years, focusing on the mechanism of action, unique advantages, and application backgrounds of various materials. At the same time, we pay attention to the need for materials used in the treatment of osteomyelitis to promote bone healing.

Spray-synthesized organic composite/hydroxyapatite coating on magnesium alloys with enhanced corrosion resistance

The development and production of anti-corrosive coatings are critical for medical implants, particularly those that utilize composite coatings made from both flexible organic materials and rigid inorganic materials, which exhibit advantageous mechanical properties and resistance to corrosion. In this work, an organic composite/hydroxyapatite (HA) coating on magnesium alloys is fabricated through a two-step process, which involves the application of a spray technique for the organic silica composite [polyethyleneimine (PEI)/silica sol (Si)], followed by a hydrothermal treatment to deposit hydroxyapatite. The dense and tight layer-by-layer assembly of the PEI/Si/HA coating on the Mg substrate exhibited a corrosion current density of 10-5.6 A/cm2, significantly lower than that of HA and the Mg substrate. After immersion for 13 days, the PEI/Si/HA coatings demonstrated a minimal amount of H2 generation and negligible fluctuations in pH within the solution. Meanwhile, the hydrothermal PEI/Si/HA coatings exhibited significantly weaker corrosion resistance than the PEI/Si/HA coatings synthesized using the spray method. Both electrochemical dynamic data and structural characteristics demonstrate the enhanced corrosion resistance of organic composite/hydroxyapatite coatings, in which polymer chains provided more volume as a buffer for H2 molecules. This organic composite/hydroxyapatite coating on magnesium alloys exhibited huge potential applications in orthopedics.

Effects of Copper Doping on Fluorohydroxyapatite Coating: Analysis of Microstructure, Biocompatibility, Corrosion Resistance, and Cell Adhesion Characteristics

In this research, Cu-doped fluorohydroxyapatite (Cu-FHAp) coatings containing varying levels of Cu in electrolyte as a dopant were synthesized by the ultrasonic-assisted pulse-reverse electrodeposition method on AZ31 alloy to improve the biocompatibility and corrosion resistance of the alloy for biomedical applications. Microstructural analysis revealed that the inclusion of the Cu dopant results in the formation of a more uniform coating. Energy dispersive spectroscopy analysis highlights a notable incorporation of copper within the fluorohydroxyapatite structure. The increase in Cu content significantly affected surface roughness and elevated hydrophobicity, leading to a contact angle of up to 136°. Electrochemical impedance spectroscopy analysis revealed that all samples containing copper exhibited favorable corrosion resistance, with the sample prepared using the electrolyte containing 0.036 g/L Cu(NO3)2 demonstrating the highest corrosion resistance. Cell adhesion evaluation yielded a satisfactory cell adhesion to the coated samples, indicating that the presence of the optimum value of Cu does not induce considerable cytotoxic effects.

In vitro and in vivo degradation, biocompatibility and bone repair performance of strontium-doped montmorillonite coating on Mg-Ca alloy

Poor bone growth remains a challenge for degradable bone implants. Montmorillonite and strontium were selected as the carrier and bone growth promoting elements to prepare strontium-doped montmorillonite coating on Mg-Ca alloy. The surface morphology and composition were characterized by SEM, EDS, XPS, FT-IR and XRD. The hydrogen evolution experiment and electrochemical test results showed that the Mg-Ca alloy coated with Sr-MMT coating possessed optimal corrosion resistance performance. Furthermore, in vitro studies on cell activity, ALP activity, and cell morphology confirmed that Sr-MMT coating had satisfactory biocompatibility, which can significantly avail the proliferation, differentiation, and adhesion of osteoblasts. Moreover, the results of the 90-day implantation experiment in rats indicated that, the preparation of Sr-MMT coating effectively advanced the biocompatibility and bone repair performance of Mg-Ca alloy. In addition, The Osteogenic ability of Sr-MMT coating may be due to the combined effect of the precipitation of Si4+ and Sr2+ in Sr-MMT coating and the dissolution of Mg2+ and Ca2+ during the degradation of Mg-Ca alloy. By using coating technology, this study provides a late-model strategy for biodegradable Mg alloys with good corrosion resistance, biocompatibility. This new material will bring more possibilities in bone repair.

Effect of Er:YAG Pulsed Laser-Deposited Hydroxyapatite Film on Titanium Implants on M2 Macrophage Polarization In Vitro and Osteogenesis In Vivo

In a previous study, we successfully coated hydroxyapatite (HAp) onto titanium (Ti) plates using the erbium-doped yttrium aluminum garnet pulsed-laser deposition (Er:YAG-PLD) method. In this study, we performed further experiments to validate the in vitro osteogenic properties, macrophage polarization, and in vivo osseointegration activity of HAp-coated Ti (HAp-Ti) plates and screws. Briefly, we coated a HAp film onto the surfaces of Ti plates and screws via Er:YAG-PLD. The surface morphological, elemental, and crystallographic analyses confirmed the successful surface coating. The macrophage polarization and osteogenic induction were evaluated in macrophages and rat bone marrow mesenchymal stem cells, and the in vivo osteogenic properties were studied. The results showed that needle-shaped nano-HAp promoted the early expression of osteogenic and immunogenic genes in the macrophages and induced excellent M2 polarization properties. The calcium deposition and osteocalcin production were significantly higher in the HAp-Ti than in the uncoated Ti. The implantation into rat femurs revealed that the HAp-coated materials had superior osteoinductive and osseointegration activities compared with the Ti, as assessed by microcomputed tomography and histology. Thus, HAp film on sandblasted Ti plates and screws via Er:YAG-PLD enhances hard-tissue differentiation, macrophage polarization, and new bone formation in tissues surrounding implants both in vitro and in vivo.

In-vivo bone remodeling potential of Sr-d-Ca-P /PLLA-HAp coated biodegradable ZK60 alloy bone plate

Magnesium and its alloys are widely applied biomaterials due to their biodegradability and biocompatibility. However, rapid degradation and hydrogen gas evolution hinder its applicability on a commercial scale. In this study, we developed an Mg alloy bone plate for bone remodeling and support after a fracture. We further coated the Mg alloy plate with Sr-D-Ca-P (Sr dopped Ca-P coating) and Sr-D-Ca-P/PLLA-HAp to evaluate and compare their biodegradability and biocompatibility in both in vitro and in vivo experiments. Chemical immersion and dip coating were employed for the formation of Sr-D-Ca-P and PLLA-HAp layers, respectively. In vitro evaluation depicted that both coatings delayed the degradation process and exhibited excellent biocompatibility. MC3T3-E1cells proliferation and osteogenic markers expression were also promoted. In vivo results showed that both Sr-D-Ca-P and Sr-D-Ca-P/PLLA-HAp coated bone plates had slower degradation rate as compared to Mg alloy. Remarkable bone remodeling was observed around the Sr-D-Ca-P/PLLA-HAp coated bone plate than bare Mg alloy and Sr-D-Ca-P coated bone plate. These results suggest that Sr-D-Ca-P/PLLA-HAp coated Mg alloy bone plate with lower degradation and enhanced biocompatibility can be applied as an orthopedic implant.

Comprehensive review of additively manufactured biodegradable magnesium implants for repairing bone defects from biomechanical and biodegradable perspectives

Bone defect repair is a complicated clinical problem, particularly when the defect is relatively large and the bone is unable to repair itself. Magnesium and its alloys have been introduced as versatile biomaterials to repair bone defects because of their excellent biocompatibility, osteoconductivity, bone-mimicking biomechanical features, and non-toxic and biodegradable properties. Therefore, magnesium alloys have become a popular research topic in the field of implants to treat critical bone defects. This review explores the popular Mg alloy research topics in the field of bone defects. Bibliometric analyses demonstrate that the degradation control and mechanical properties of Mg alloys are the main research focus for the treatment of bone defects. Furthermore, the additive manufacturing (AM) of Mg alloys is a promising approach for treating bone defects using implants with customized structures and functions. This work reviews the state of research on AM-Mg alloys and the current challenges in the field, mainly from the two aspects of controlling the degradation rate and the fabrication of excellent mechanical properties. First, the advantages, current progress, and challenges of the AM of Mg alloys for further application are discussed. The main mechanisms that lead to the rapid degradation of AM-Mg are then highlighted. Next, the typical methods and processing parameters of laser powder bed fusion fabrication on the degradation characteristics of Mg alloys are reviewed. The following section discusses how the above factors affect the mechanical properties of AM-Mg and the recent research progress. Finally, the current status of research on AM-Mg for bone defects is summarized, and some research directions for AM-Mg to drive the application of clinical orthopedic implants are suggested.

Influence of Surface Roughness on Biodegradability and Cytocompatibility of High-Purity Magnesium

High-purity magnesium (Mg) is a promising biodegradable metal for oral and maxillofacial implants. Appropriate surface roughness plays a critical role in the degradation behavior and the related cellular processes of biodegradable Mg-based metals. Nevertheless, the most optimized surface roughness has been questionable, especially for Mg-based oral and maxillofacial implants. Three representative scales of surface roughness were investigated in this study, including smooth (Sa < 0.5 µm), moderately rough (Sa between 1.0−2.0 µm), and rough (Sa > 2.0 µm). The results indicated that the degradation rate of the Mg specimen in the cell culture medium was significantly accelerated with increased surface roughness. Furthermore, an extract test revealed that Mg with different roughness did not induce an evident cytotoxic effect. Nonetheless, the smooth Mg surface had an adversely affected cell attachment. Therefore, the high-purity Mg with a moderately rough surface exhibited the most optimized balance between biodegradability and overall cytocompatibility.