Osteogenic activity and antibacterial ability on titanium surfaces modified with magnesium-doped titanium dioxide coating

Hydrogel Coatings of Implants for Pathological Bone Repair

Hydrogels are well-suited for biomedical applications due to their numerous advantages, such as excellent bioactivity, versatile physical and chemical properties, and effective drug delivery capabilities. Recently, hydrogel coatings have developed to functionalize bone implants which are biologically inert and cannot withstand the complex bone tissue repair microenvironment. These coatings have shown promise in addressing unique and pressing medical needs. This review begins with the major functionalized performance and interfacial bonding strategy of hydrogel coatings, with a focus on the novel external field response properties of the hydrogel. Recent advances in the fabrication strategies of hydrogel coatings and their use in the treatment of pathologic bone regeneration are highlighted. Finally, challenges and emerging trends in the evolution and application of physiological environment-responsive and external electric field-responsive hydrogel coatings for bone implants are discussed.

Biointerfaces with ultrathin patterns for directional control of cell migration

In the context of wound healing and tissue regeneration, precise control of cell migration direction is deemed crucial. To address this challenge, polydimethylsiloxane (PDMS) platforms with patterned 10 nm thick TiOx in arrowhead shape were designed and fabricated. Remarkably, without tall sidewall constraints, MC3T3-E1 cells seeded on these platforms were constrained to migrate along the tips of the arrowheads, as the cells were guided by the asymmetrical arrowhead tips which provided large contact areas. To the best of our knowledge, this is the first study demonstrating the use of thin TiOx arrowhead pattern in combination with a cell-repellent PDMS surface to provide guided cell migration unidirectionally without tall sidewall constraints. Additionally, high-resolution fluorescence imaging revealed that the asymmetrical distribution of focal adhesions, triggered by the patterned TiOx arrowheads with arm lengths of 10, 20, and 35 μm, promoted cell adhesion and protrusion along the arrowhead tip direction, resulting in unidirectional cell migration. These findings have important implications for the design of biointerfaces with ultrathin patterns to precisely control cell migration. Furthermore, microelectrodes were integrated with the patterned TiOx arrowheads to enable dynamic monitoring of cell migration using impedance measurement. This microfluidic device integrated with thin layer of guiding pattern and microelectrodes allows simultaneous control of directional cell migration and characterization of the cell movement of individual MC3T3-E1 cells, offering great potential for the development of biosensors for single-cell monitoring.

Preparation of a novel antibacterial magnesium carbonate coating on a titanium surface and its in vitro biocompatibility

Magnesium-based coatings have attracted great attention in surface modification of titanium implants due to their superior angiogenic and osteogenic properties. However, their biological effects as a carbonate-based constituent remain unrevealed. In this study, magnesium carbonate coatings were prepared on titanium surfaces under hydrothermal conditions and subsequently treated with hydrogen peroxide. Also, their antibacterial activity and in vitro cell biocompatibility were evaluated. The obtained coatings consisted of nanoparticles without cracks and exhibited excellent adhesion to the substrate. X-ray diffraction (XRD) results indicated pure magnesium carbonate coatings formed on the Ti surface after hydrothermal treatment. After hydrogen peroxide treatment, the phase composition of the coatings had no obvious change. Compared to the untreated coatings, the hydrogen peroxide-treated coatings showed increased surface roughness and hydrophilicity. Co-culture with Staphylococcus aureus (S. aureus) demonstrated that the obtained coatings had good antibacterial activity. In vitro cell culture results showed that the hydrogen peroxide-treated coatings enhanced the viability, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). These findings suggest that this MgCO3-based coating exhibits excellent antibacterial performance and osteogenic potential. Based on the above, this study provides a simple method for preparing titanium implants with dual antibacterial and osteogenic capabilities, holding great promise in clinical applications.

Self-Healing Micro Arc Oxidation and Dicalcium Phosphate Dihydrate Double-Passivated Coating on Magnesium Membrane for Enhanced Bone Integration Repair

Magnesium is a revolutionary biomaterial for orthopedic implants, owing to its eminent mechanical properties and biocompatibility. However, its uncontrolled degradation rate remains a severe challenge for its potential applications. In this study, we developed a self-healing micro arc oxidation (MAO) and dicalcium phosphate dihydrate (DCPD) double-passivated coating on a magnesium membrane (Mg-MAO/DCPD) and investigated its potential for bone-defect healing. The Mg-MAO/DCPD membrane possessed a feasible self-repairing ability and good cytocompatibility. In vitro degradation experiments showed that the Mg contents on the coating surface were 0.3, 3.8, 4.1, 6.1, and 7.9% when the degradation times were 0, 1, 2, 3, and 4 weeks, respectively, exhibiting available corrosion resistance. The slow and sustained release of Mg2+ during the degradation process activated extracellular matrix proteins for bone regeneration, accelerating osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). The extract solutions of Mg-MAO/DCPD considerably promoted the activation of the Wnt and PI3K/AKT signaling pathways. Furthermore, the evaluation of the rat skull defect model manifested the outstanding bone-healing efficiency of the Mg-MAO/DCPD membrane. Taken together, the Mg-MAO/DCPD membrane demonstrates an optimized degradation rate and excellent bioactivity and is believed to have great application prospects in bone tissue engineering.

Surface modification of titanium implants with Mg-containing coatings to promote osseointegration

Titanium (Ti) and Ti alloys are commonly used in dental implants, which have good biocompatibility, mechanical strength, processability, and corrosion resistance. However, the surface inertia of Ti implants leads to delayed integration of Ti and new bone, as well as problems such as aseptic loosening and inadequate osseointegration. Magnesium (Mg) ions can promote bone regeneration, and many studies have used Mg-containing materials to modify the Ti implant surface. This systematic review summarizes the methods, effects, and clinical applications of surface modification of Ti implants with Mg-containing coatings. Database collection was completed on Janury 1, 2023, and a total of 29 relevant studies were ultimately included. Mg can be compounded with different materials and coated to the surface of Ti implants using different methods. In vitro and in vivo experiments have shown that Mg-containing coatings promote cell adhesion and osteogenic differentiation. On the one hand, the surface roughness of implants increases with the addition of Mg-containing coatings, which is thought to have an impact on the osseointegration of the implant. On the other hand, Mg ions promote cell attachment through binding interactions between the integrin family and FAK-related signaling pathways. And Mg ions could induce osseointegration by activating PI3K, Notch, ERK/c-Fos, BMP-4-related signaling pathways and TRPM7 protein channels. Overall, Mg-based coatings show great potential for the surface modification of Ti implants to promote osseointegration. STATEMENT OF SIGNIFICANCE: The inertia surface of titanium (Ti) implants leads to delayed osseointegration. Magnesium (Mg) ions, known for promoting bone regeneration, have been extensively studied to modify the surface of Ti implants. However, no consensus has been reached on the appropriate processing methods, surface roughness and effective concentration of Mg-containing coatings for osseointegration. This systematic review focus on the surface modification of Ti implants with Mg-containing compounds, highlighting the effects of Mg-containing coatings on the surface properties of Ti implants and its associated mechanisms. Besides, we also provide an outlook on future directions to promote the clinical application of Mg-modified implants.

Boosting Titanium Surfaces with Positive Charges: Newly Developed Cationic Coating Combines Anticorrosive and Bactericidal Properties for Implant Application

Along with poor implant-bone integration, peri-implant diseases are the major causes of implant failure. Although such diseases are primarily triggered by biofilm accumulation, a complex inflammatory process in response to corrosive-related metallic ions/debris has also been recognized as a risk factor. In this regard, by boosting the titanium (Ti) surface with silane-based positive charges, cationic coatings have gained increasing attention due to their ability to kill pathogens and may be favorable for corrosion resistance. Nevertheless, the development of a cationic coating that combines such properties in addition to having a favorable topography for implant osseointegration is lacking. Because introducing hydroxyl (-OH) groups to Ti is essential to increase chemical bonds with silane, Ti pretreatment is of utmost importance to achieve such polarization. In this study, plasma electrolytic oxidation (PEO) was investigated as a new route to pretreat Ti with OH groups while providing favorable properties for implant application compared with traditional hydrothermal treatment (HT). To produce bactericidal and corrosion-resistant cationic coatings, after pretreatment with PEO or HT (Step 1), surface silanization was subsequently performed via immersion-based functionalization with 3-aminopropyltriethoxysilane (APTES) (Step 2). In the end, five groups were assessed: untreated Ti (Ti), HT, PEO, HT+APTES, and PEO+APTES. PEO created a porous surface with increased roughness and better mechanical and tribological properties compared with HT and Ti. The introduction of -OH groups by HT and PEO was confirmed by Fourier transform infrared spectroscopy and the increase in wettability producing superhydrophilic surfaces. After silanization, the surfaces were polarized to hydrophobic ones, and an increase in the amine functional group was observed by X-ray photoelectron spectroscopy, demonstrating a considerable amount of positive ions. Such protonation may explain the enhanced corrosion resistance and dead bacteria (Streptococcus aureus and Escherichia coli) found for PEO+APTES. All groups presented noncytotoxic properties with similar blood plasma protein adsorption capacity vs the Ti control. Our findings provide new insights into developing next-generation cationic coatings by suggesting that a tailorable porous and oxide coating produced by PEO has promise in designing enhanced cationic surfaces targeting biomedical and dental implant applications.

Surface Modification of Titanium Implants by Metal Ions and Nanoparticles for Biomedical Application

Implant surface modification can improve osseointegration and reduce peri-implant inflammation. Implant surfaces are modified with metals because of their excellent mechanical properties and significant functions. Metal surface modification is divided into metal ions and nanoparticle surface modification. These two methods function by adding a finishing metal to the surface of the implant, and both play a role in promoting osteogenic, angiogenic, and antibacterial properties. Based on this, the nanostructural surface changes confer stronger antibacterial and cellular affinity to the implant surface. The current paper reviews the forms, mechanisms, and applications of nanoparticles and metal ion modifications to provide a foundation for the surface modification of implants.

Implantable biomedical materials for treatment of bone infection

The treatment of bone infections has always been difficult. The emergence of drug-resistant bacteria has led to a steady decline in the effectiveness of antibiotics. It is also especially important to fight bacterial infections while repairing bone defects and cleaning up dead bacteria to prevent biofilm formation. The development of biomedical materials has provided us with a research direction to address this issue. We aimed to review the current literature, and have summarized multifunctional antimicrobial materials that have long-lasting antimicrobial capabilities that promote angiogenesis, bone production, or "killing and releasing." This review provides a comprehensive summary of the use of biomedical materials in the treatment of bone infections and a reference thereof, as well as encouragement to perform further research in this field.

Advances in Research on Titanium and Titanium Alloys with Antibacterial Functionality for Medical Use—A Review

Materials based on titanium and its alloys are widely used in the medical and dental fields because of their excellent physical properties such as hardness, ductility and elastic modulus, etc. However, because commonly used titanium alloy internal plants do not have antibacterial properties, when these implants are implanted into the human body, there is a certain risk of infection. Such infections are extremely painful for the patient and problematic for the attending physician. In the past, infections of implants were usually treated with systemic antibiotics in combination with thorough debridement or implant replacement. However, these are passive treatments and typically cause huge physical and economic burdens on the patient. Therefore, attempts towards the development of implants with antibacterial functionality have been increasing, with the combination of titanium alloys with antibiotics, antibacterialmetals, and antibacterial peptides being the main research direction. Therefore, this paper will discuss the latest research progress in the preparation of titanium alloys with antibacterial strategies such as combining antibiotics or antimicrobial peptides, adding antimicrobial metals, and the antibacterial properties and biocompatibility of proposed systems are summarised and discussed herein. This review should serve as a reference for further research on antibacterial titanium alloy implants.

The race for the optimal antimicrobial surface: perspectives and challenges related to plasma electrolytic oxidation coating for titanium-based implants

Plasma electrolytic oxidation (PEO) is a low-cost, structurally reliable, and environmentally friendly surface modification method for orthopedic and dental implants. This technique is successful for the formation of porous, corrosion-resistant, and bioactive coatings, besides introducing antimicrobial compounds easily. Given the increase in implant-related infections, antimicrobial PEO-treated surfaces have been widely proposed to surmount this public health concern. This review comprehensively discusses antimicrobial implant surfaces currently produced by PEO in terms of their in vitro and in vivo microbiological and biological properties. We present a critical [part I] and evidence-based [part II] review about the plethora of antimicrobial PEO-treated surfaces. The mechanism of microbial accumulation on implanted devices and the principles of PEO technology to ensure antimicrobial functionalization by one- or multi-step processes are outlined. Our systematic literature search showed that particular focus has been placed on the metallic and semi-metallic elements incorporated into PEO surfaces to facilitate antimicrobial properties, which are often dose-dependent, without leading to cytotoxicity in vitro. Meanwhile, there are concerns over the biocompatibility of PEO and its long-term antimicrobial effects in animal models. We clearly highlight the importance of using clinically relevant infection models and in vivo long-term assessments to guarantee the rational design of antimicrobial PEO-treated surfaces to identify the 'finish line' in the race for antimicrobial implant surfaces.

Promotion of bone formation and antibacterial properties of titanium coated with porous Si/Ag-doped titanium dioxide

Implant materials are mainly used to repair and replace defects in human hard tissue (bones and teeth). Titanium (Ti) and Ti alloys are widely used as implant materials because of their good mechanical properties and biocompatibilities, but they do not have the ability to induce new bone formation and have no antibacterial properties. Through surface modification, Ti and its alloys have certain osteogenic and antibacterial properties such that Ti implants can meet clinical needs and ensure integration between Ti implants and bone tissue, and this is currently an active research area. In this study, bioactive Si and Ag were introduced onto a Ti surface by plasma oxidation. The surface morphology, structure, elemental composition and valence, surface roughness, hydrophilicity and other physical and chemical properties of the coating were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), a profiler and a contact angle meter (CA). Adhesion and extensions of osteoblasts on the surface of the material were observed by scanning electron microscopy, and mineralization of osteoblasts on the surface of the material were observed by alizarin red staining. The antibacterial properties of the material were tested by culturing Staphylococcus aureus on the surface of the material. The osteogenic properties of Ti implants with porous Si/Ag TiO₂ (TCP-SA) coatings were evaluated with in vivo experiments in rats. The results showed that Si and Ag were successfully introduced onto the Ti surface by plasma oxidation, and doping with Si and Ag did not change the surface morphology of the coating. The osteoblasts showed good adhesion and extension on the surfaces of Si/Ag coated samples, and the porous Si/Ag TiO₂ coating promoted cell proliferation and mineralization. The bacterial experiments showed that the porous TiO₂ coatings containing Si/Ag had certain antibacterial properties. The animal experiments showed that Si/Ag-coated Ti implants promoted integration between the implants and the surrounding bone. It was concluded that the porous Si/Ag TiO₂ coating on the Ti surface had good osteogenic and antibacterial properties and provides an optimal strategy for improving the osteogenic and antibacterial properties of Ti implants.

Betulinic acid promotes the osteogenic differentiation of human periodontal ligament stem cells by upregulating EGR1

Periodontitis is one of the most common chronic inflammations of the oral cavity, which eventually leads to tooth loss. Betulinic acid (BetA) is an organic acid that has anti-inflammatory effects and is derived from fruits and plants, but its effect on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) is still unclear. This study aimed to explore the effect of BetA on the osteogenic differentiation of hPDLSCs and its mechanism. Our results revealed that BetA not only promoted the viability of hPDLSCs but also induced their osteogenic differentiation in a dose-dependent manner. In addition, RNA sequencing was used to screen the differentially expressed genes (DEGs) after hPDLSCs were treated with BetA, and 127 upregulated and 138 downregulated genes were identified. Gene Ontology enrichment analysis showed that DEGs were mainly involved in the response to lithium ions and the positive regulation of macrophage-derived foam cell differentiation. The Kyoto Encyclopedia of Genes and Genomes analysis results revealed that DEGs were enriched in the nuclear factor-κB and interleukin-17 signaling pathways. More importantly, we confirmed that early growth response gene 1 (EGR1), one of the three DEGs involved in bone formation, significantly promoted the expression of osteogenic markers and the mineralization of hPDLSCs. Knockdown of EGR1 obviously limited the effect of BetA on the osteogenic differentiation of hPDLSCs. In conclusion, BetA promoted the osteogenic differentiation of hPDLSCs through upregulating EGR1, and BetA might be a promising candidate in the clinical application of periodontal tissue regeneration.

Osteoblast Response to Copper-Doped Microporous Coatings on Titanium for Improved Bone Integration

Due to their excellent mechanical properties and good biocompatibility, titanium alloys have become a popular research topic in the field of medical metal implants. However, the surface of the titanium alloy does not exhibit biological activity, which may cause poor integration between the interface of the titanium implant and the interface of the bone tissue and subsequently may cause the implant to fall off. Therefore, surface biological inertness is one of the problems that titanium alloys must overcome to become an ideal orthopedic implant material. Surface modification can improve the biological properties of titanium, thereby enhancing its osseointegration effect. Copper is an essential trace element for the human body, can promote bone formation and plays an important role in maintaining the physiological structure and function of bone and bone growth and development. In this study, a microporous copper-titanium dioxide coating was prepared on the surface of titanium by microarc oxidation. Based on the evaluation of its surface characteristics, the adhesion, proliferation and differentiation of MC3T3-E1 cells were observed. A titanium rod was implanted into the rabbit femoral condyle, and the integration of the coating and bone tissue was evaluated. Our research results show that the microporous copper-titanium dioxide coating has a nearly three-dimensional porous structure, and copper is incorporated into the coating without changing the structure of the coating. In vitro experiments found that the coating can promote the adhesion, proliferation and differentiation of MC3T3-E1 cells. In vivo experiments further confirmed that the titanium copper-titanium dioxide microporous coating can promote the osseointegration of titanium implants. In conclusion, copper-titanium dioxide microporous coatings can be prepared by microarc oxidation, which can improve the biological activity and biocompatibility of titanium, promote new bone formation and demonstrate good osteoinductive properties. Therefore, the use of this coating in orthopedics has potential clinical application.

Mg/Cu-doped TiO2 nanotube array: A novel dual-function system with self-antibacterial activity and excellent cell compatibility

Many studies were conducted to change the surface morphology and chemical composition of Ti implants for the improvement of antibacterial ability and osseointegration between medical Ti and surrounding bone tissue. In this study, we successfully prepared a novel dual-function coating on pure Ti surface, i.e. Cu and Mg-co-doped TiO₂ nanotube (TN) coating, by combining anodisation and hydrothermal treatment (HT), which could act as a delivery platform for the sustained release of Cu and Mg ions. Results showed that the amounts of Cu and Mg were about 5.43 wt%-6.55 wt% and 0.69 wt%-0.73 wt%, respectively. In addition, the surface morphology of Cu and Mg-co-doped TN (CuMTN) coatings transformed into nanoneedles after HT for 1 h. Compared with TN, CuMTN had no change in roughness and remarkable improved hydrophilicity. Antibacterial tests revealed that CuMTN had an antibacterial rate of more than 93% against Escherichia coli and Staphylococcus aureus, thereby showing excellent antibacterial properties. In addition, CuMTN could induce the formation of apatite well after being immersed in simulated body fluid, showing good biological activity. Preosteoblasts (MC3T3-E1) cultured on CuMTN-coated Ti demonstrated better proliferation and osteogenic differentiation than pristine and as-anodised specimens. To the best of our best knowledge, this study had successfully attempted to combine anodisation and HT, introduce Cu/Mg elements and functionalise Ti-based implant surfaces with enhanced hydrophilicity, osteogenesis and antimicrobial properties that can meet clinical needs for the first time.

Impact of exogenous metal ions on peri-implant bone metabolism: a review

The development of effective methods to promote the osseointegration of dental implants by surface modification is an area of intense research in dental materials science. Exogenous metal ions present in the implant and surface modifications are closely related to the bone metabolism around the implant. In the complex oral microenvironment, the release of metal ions caused by continuous corrosion of dental implants has an unfavorable impact on the surrounding tissue, and then affects osseointegration, leading to bad results such as loosening and falling off in the late stage of the implant. Besides, these ions can even be distributed in distant tissues and organs. Currently, surface modification techniques are being developed that involve different processing technologies including the introduction of exogenous metal ions with different properties onto the surface of implants to improve performance. However, most metal elements have some level of biological toxicity and can only be used within a safe concentration range to exert the optimum biological effects on recipients. In this paper, we review the adverse effects of metal ions on osseointegration and highlight the emerging applications for metal elements in improving the performance of dental implants.

Gradient nanostructured titanium stimulates cell responses in vitro and enhances osseointegration in vivo

Background

Though titanium (Ti) is widely used as dental materials in the clinic, effective methods to treat Ti for higher surface biological activity still lack. Through Surface mechanical attrition treatment (SMAT) technology we could endow Ti with gradient nanostructured surface (GNS Ti). To investigate the biocompatibility of GNS Ti for its further application in dental implant field, we study the effects of GNS Ti on cell responses in vitro and osseointegration of the implant with surrounding bone tissues in vivo.

Methods

In this study, GNS Ti was fabricated by SMAT. In vitro experiment, we co-cultured GNS Ti with bone mesenchymal stem cells (BMSCs), surface characterization was detected by transmission electron microscope (TEM). Adhesion, proliferation and differentiation of BMSCs were evaluated by scanning electron microscope (SEM), MTT, flow cytometry (FCM), alkaline phosphatase (ALP) and osteocalcin (OCN) tests. In vivo experiment, the GNS Ti was implanted into the rabbit mandible. Osteogenesis and osseointegration were evaluated by Micro CT, toluidine blue staining, and immunohistochemical staining at 4, 8, and 12 weeks postoperatively.

Results

Both results showed that compared with the coarse grained (CG) Ti, the GNS Ti stimulated the adhesion, proliferation, and differentiation of BMSCs and improved osteogenesis and osseointegration.

Conclusions

This study indicates that gradient nanostructured Ti is a promising material for dental implant application.

Dental Implants Loaded With Bioactive Agents Promote Osseointegration in Osteoporosis: A Review

Implant-supported dentures are widely used in patients with defect or loss of dentition because these have higher chewing efficiency and do not damage the adjacent teeth compared with fixed or removable denture. An implant-supported denture carries the risk of failure in some systemic diseases, including osteoporosis, because of a non-ideal local microenvironment. Clinically common physical and chemical modifications are used to change the roughness of the implant surface to promote osseointegration, but they have limitations in promoting osteoinduction and inhibiting bone resorption. Recently, many researchers have focused on the study of bioactive modification of implants and have achieved promising results. Herein we have summarized the progress in bioactive modification strategy to promote osseointegration by regulating the local osteoporotic microenvironment.

[Research progress on antibacterial properties of porous medical implant materials]

OBJECTIVE

The antibacterial properties of porous medical implant materials were reviewed to provide guidance for further improvement of new medical implant materials.

METHODS

The literature related to the antibacterial properties of porous medical implant materials in recent years was consulted, and the classification, characteristics and applications, and antibacterial methods of porous medical implant materials were reviewed.

RESULTS

Porous medical implant materials can be classified according to surface pore size, preparation process, degree of degradation in vivo, and material source. It is widely used in the medical field due to its good biocompatibility and biomechanical properties. Nevertheless, the antibacterial properties of porous medical implant materials themselves are not obvious, and their antibacterial properties need to be improved through structural modification, overall modification, and coating modification.

CONCLUSION

At present, coating modification as the mainstream modification method for improving the antibacterial properties of porous medical materials is still a research hotspot. The introduction of new antibacterial substances provides a new perspective for the development of new coated porous medical implant materials, so that the porous medical implant materials have a more reliable antibacterial effect while taking into account biocompatibility.

Metallic Antibacterial Surface Treatments of Dental and Orthopedic Materials

The oral cavity harbors complex microbial communities, which leads to biomaterial-associated infections (BAI) during dental and orthopedic treatments. Conventional antibiotic treatments have met great challenges recently due to the increasing emergency of drug-resistant bacteria. To tackle this clinical issue, antibacterial surface treatments, containing surface modification and coatings, of dental and orthopedic materials have become an area of intensive interest now. Among various antibacterial agents used in surface treatments, metallic agents possess unique properties, mainly including broad-spectrum antibacterial properties, low potential to develop bacterial resistance, relative biocompatibility, and chemical stability. Therefore, this review mainly focuses on underlying antibacterial applications and the mechanisms of metallic agents in dentistry and orthopedics. An overview of the present review indicates that much work remains to be done to deepen the understanding of antibacterial mechanisms and potential side-effects of metallic agents.

Osteoconductive and Osteoinductive Surface Modifications of Biomaterials for Bone Regeneration: A Concise Review

The main aim of bone tissue engineering is to fabricate highly biocompatible, osteoconductive and/or osteoinductive biomaterials for tissue regeneration. Bone implants should support bone growth at the implantation site via promotion of osteoblast adhesion, proliferation, and formation of bone extracellular matrix. Moreover, a very desired feature of biomaterials for clinical applications is their osteoinductivity, which means the ability of the material to induce osteogenic differentiation of mesenchymal stem cells toward bone-building cells (osteoblasts). Nevertheless, the development of completely biocompatible biomaterials with appropriate physicochemical and mechanical properties poses a great challenge for the researchers. Thus, the current trend in the engineering of biomaterials focuses on the surface modifications to improve biological properties of bone implants. This review presents the most recent findings concerning surface modifications of biomaterials to improve their osteoconductivity and osteoinductivity. The article describes two types of surface modifications: (1) Additive and (2) subtractive, indicating biological effects of the resultant surfaces in vitro and/or in vivo. The review article summarizes known additive modifications, such as plasma treatment, magnetron sputtering, and preparation of inorganic, organic, and composite coatings on the implants. It also presents some common subtractive processes applied for surface modifications of the biomaterials (i.e., acid etching, sand blasting, grit blasting, sand-blasted large-grit acid etched (SLA), anodizing, and laser methods). In summary, the article is an excellent compendium on the surface modifications and development of advanced osteoconductive and/or osteoinductive coatings on biomaterials for bone regeneration.

The role of magnesium in biomaterials related infections

Magnesium is currently increasing interest in the field of biomaterials. An extensive bibliography on this material in the last two decades arises from its potential for the development of biodegradable implants. In addition, many researches, motivated by this progress, have analyzed the performance of magnesium in both in vitro and in vivo assays with gram-positive and gram-negative bacteria in a very broad range of conditions. This review explores the extensive literature in recent years on magnesium in biomaterials-related infections, and discusses the mechanisms of the Mg action on bacteria, as well as the competition of Mg²⁺ and/or synergy with other divalent cations in this subject.