Zinc-modified titanium surface enhances osteoblast differentiation of dental pulp stem cells in vitro

The Effect of Marginal Zn2+ Excess Released from Titanium Coating on Differentiation of Human Osteoblastic Cells

Composite coatings based on chitosan and zinc nanoparticles (ZnNPs) were successfully produced on Ti13Zr13Nb substrates by cathodic electrophoretic deposition (EPD). The unfavorable phenomenon of water electrolysis-induced nonuniformity was reduced by applying a low voltage (20 V) and a short deposition time (1 min). Surface analysis (roughness and hydrophilicity) reveals the potential of these coatings for enhancing cell attachment and bone-implant integration. However, there is a concern about adhesion and strength; therefore, incorporating ZnNPs shows promise for enhancing mechanical properties, suggesting opportunities for further optimization of the process. The aim of this work was to investigate whether Zn2+ released from coating yields overt cellular impairment. hFOB1.19 osteoblastic cells were used as a model in this study. A subtoxic, 0.125 mmol/L, Zn concentration did not cause significant negative changes in cultured osteoblastic cells, as there was no significant change in their viability and their mitochondrial metabolism. Moreover, the alkaline phosphatase and lactate dehydrogenase activities were aggravated. However, a high, over 0.175 mmol/L, Zn2+ concentration caused total cell death. This was caused by the inhibition of mitochondrial enzymes' activities. Our data indicate that composite coatings releasing Zn2+ may be used as the differentiating factor toward osteoblastic cells.

Highly Stable Amorphous (Pyro)phosphate Aggregates: Pyrophosphate as a Carrier for Bioactive Ions and Drugs in Bone Repair Applications

Pyrophosphate is widely used as an iron supplement because of its excellent complexation and hydrolysis ability; however, there are few reports on the use of pyrophosphate in active ionophores for bone repair. In this research, we proposed a simple and efficient ultrasonic method to prepare magnesium-calcium (pyro)phosphate aggregates (AMCPs). Due to strong hydration, AMCPs maintain a stable amorphous form even at high temperatures (400 °C). By changing the molar ratio of calcium and magnesium ions, the content of calcium and magnesium ions can be customized. AMCPs had surface negativity and complexing ability that realized the controlled release of ions (Ca2+, Mg2+, and P) and drugs (such as doxorubicin) over a long period. Pyrophosphate gave it an excellent bacteriostatic effect. Increasingly released Mg2+ exhibited improved bioactivity though the content of Ca2+ decreased. While Mg2+ content was regulated to 15 wt %, it performed significantly enhanced stimulation on the proliferation, attachment, and differentiation (ALP activity, calcium nodules, and the related gene expression of osteogenesis) of mouse embryo osteoblast precursor cells (MC3T3-E1). Furthermore, the high content of Mg2+ also effectively promoted the proliferation, attachment, and migration of human umbilical vein endothelial cells (HUVECs) and the expression of angiogenic genes. In conclusion, pyrophosphate was an excellent carrier for bioactive ions, and the AMCPs we prepared had a variety of active functions for multiscenario bone repair applications.

Osteoblast Attachment on Bioactive Glass Air Particle Abrasion-Induced Calcium Phosphate Coating

Air particle abrasion (APA) using bioactive glass (BG) effectively decontaminates titanium (Ti) surface biofilms and the retained glass particles on the abraded surfaces impart potent antibacterial properties against various clinically significant pathogens. The objective of this study was to investigate the effect of BG APA and simulated body fluid (SBF) immersion of sandblasted and acid-etched (SA) Ti surfaces on osteoblast cell viability. Another goal was to study the antibacterial effect against Streptococcus mutans. Square-shaped 10 mm diameter Ti substrates (n = 136) were SA by grit blasting with aluminum oxide particles, then acid-etching in an HCl-H2SO4 mixture. The SA substrates (n = 68) were used as non-coated controls (NC-SA). The test group (n = 68) was further subjected to APA using experimental zinc-containing BG (Zn4) and then mineralized in SBF for 14 d (Zn4-CaP). Surface roughness, contact angle, and surface free energy (SFE) were calculated on test and control surfaces. In addition, the topography and chemistry of substrate surfaces were also characterized. Osteoblastic cell viability and focal adhesion were also evaluated and compared to glass slides as an additional control. The antibacterial effect of Zn4-CaP was also assessed against S. mutans. After immersion in SBF, a mineralized zinc-containing Ca-P coating was formed on the SA substrates. The Zn4-CaP coating resulted in a significantly lower Ra surface roughness value (2.565 μm; p < 0.001), higher wettability (13.35°; p < 0.001), and higher total SFE (71.13; p < 0.001) compared to 3.695 μm, 77.19° and 40.43 for the NC-SA, respectively. APA using Zn4 can produce a zinc-containing calcium phosphate coating that demonstrates osteoblast cell viability and focal adhesion comparable to that on NC-SA or glass slides. Nevertheless, the coating had no antibacterial effect against S. mutans.

Metal Ion-Doped Hydroxyapatite-Based Materials for Bone Defect Restoration

Hydroxyapatite (HA)-based materials are widely used in the bone defect restoration field due to their stable physical properties, good biocompatibility, and bone induction potential. To further improve their performance with extra functions such as antibacterial activity, various kinds of metal ion-doped HA-based materials have been proposed and synthesized. This paper offered a comprehensive review of metal ion-doped HA-based materials for bone defect restoration based on the introduction of the physicochemical characteristics of HA followed by the synthesis methods, properties, and applications of different kinds of metal ion (Ag+, Zn2+, Mg2+, Sr2+, Sm3+, and Ce3+)-doped HA-based materials. In addition, the underlying challenges for bone defect restoration using these materials and potential solutions were discussed.

The changes and potential effects of zinc homeostasis in periodontitis microenvironment

Zinc is a very important and ubiquitous element, which is present in oral environment, daily diet, oral health products, dental restorative materials, and so on. However, there is a lack of attention to the role of both extracellular or intracellular zinc in the progression of periodontitis and periodontal regeneration. This review summarizes the characteristics of immunological microenvironment and host cells function in several key stages of periodontitis progression, and explores the regulatory effect of zinc during this process. We find multiple evidence indicate that zinc may be involved and play a key role in the stages of immune defense, inflammatory response and bone remodeling. Zinc supplementation in an appropriate dose range or regulation of zinc transport proteins can promote periodontal regeneration by either enhancing immune defense or up-regulating local cells proliferation and differentiation functions. Therefore, zinc homeostasis is essential in periodontal remodeling and regeneration. More attention is suggested to be focused on zinc homeostasis regulation and consider it as a potential strategy in the studies on periodontitis treatment, periodontal-guided tissue regeneration, implant material transformation, and so on.

The Role of Trace Elements and Minerals in Osteoporosis: A Review of Epidemiological and Laboratory Findings

The objective of the present study was to review recent epidemiological and clinical data on the association between selected minerals and trace elements and osteoporosis, as well as to discuss the molecular mechanisms underlying these associations. We have performed a search in the PubMed-Medline and Google Scholar databases using the MeSH terms "osteoporosis", "osteogenesis", "osteoblast", "osteoclast", and "osteocyte" in association with the names of particular trace elements and minerals through 21 March 2023. The data demonstrate that physiological and nutritional levels of trace elements and minerals promote osteogenic differentiation through the up-regulation of BMP-2 and Wnt/β-catenin signaling, as well as other pathways. miRNA and epigenetic effects were also involved in the regulation of the osteogenic effects of trace minerals. The antiresorptive effect of trace elements and minerals was associated with the inhibition of osteoclastogenesis. At the same time, the effect of trace elements and minerals on bone health appeared to be dose-dependent with low doses promoting an osteogenic effect, whereas high doses exerted opposite effects which promoted bone resorption and impaired bone formation. Concomitant with the results of the laboratory studies, several clinical trials and epidemiological studies demonstrated that supplementation with Zn, Mg, F, and Sr may improve bone quality, thus inducing antiosteoporotic effects.

Zinc (Zn) Doping by Hydrothermal and Alkaline Heat-Treatment Methods on Titania Nanotube Arrays for Enhanced Antibacterial Activity

Titanium (Ti) is a popular biomaterial for orthopedic implant applications due to its superior mechanical properties such as corrosion resistance and low modulus of elasticity. However, around 10% of these implants fail annually due to bacterial infection and poor osseointegration, resulting in severe pain and suffering for the patients. To improve their performance, nanoscale surface modification approaches and doping of trace elements on the surfaces can be utilized which may help in improving cell adhesion for better osseointegration while reducing bacterial infection. In this work, at first, titania (TiO₂) nanotube arrays (NT) were fabricated on commercially available pure Ti surfaces via anodization. Then zinc (Zn) doping was conducted following two distinct methods: hydrothermal and alkaline heat treatment. Scanning electron microscopic (SEM) images of the prepared surfaces revealed unique surface morphologies, while energy dispersive X-ray spectroscopy (EDS) revealed Zn distribution on the surfaces. Contact angle measurements indicated that NT surfaces were superhydrophilic. X-ray photoelectron spectroscopy (XPS) provided the relative amount of Zn on the surfaces and indicated that hydrothermally treated surfaces had more Zn compared to the alkaline heat-treated surfaces. X-ray crystallography (XRD) and nanoindentation techniques provided the crystal structure and mechanical properties of the surfaces. While testing with adipose-derived stem cells (ADSC), the surfaces showed no apparent cytotoxicity to the cells. Finally, bacteria adhesion and morphology were evaluated on the surfaces after 6 h and 24 h of incubation. From the results, it was confirmed that NT surfaces doped with Zn drastically reduced bacteria adhesion compared to the Ti control. Zn-doped NT surfaces thus offer a potential platform for orthopedic implant application.

Inflammation Responses to Bone Scaffolds under Mechanical Stimuli in Bone Regeneration

Physical stimuli play an important role in one tissue engineering. Mechanical stimuli, such as ultrasound with cyclic loading, are widely used to promote bone osteogenesis; however, the inflammatory response under physical stimuli has not been well studied. In this paper, the signaling pathways related to inflammatory responses in bone tissue engineering are evaluated, and the application of physical stimulation to promote osteogenesis and its related mechanisms are reviewed in detail; in particular, how physical stimulation alleviates inflammatory responses during transplantation when employing a bone scaffolding strategy is discussed. It is concluded that physical stimulation (e.g., ultrasound and cyclic stress) helps to promote osteogenesis while reducing the inflammatory response. In addition, apart from 2D cell culture, more consideration should be given to the mechanical stimuli applied to 3D scaffolds and the effects of different force moduli while evaluating inflammatory responses. This will facilitate the application of physiotherapy in bone tissue engineering.

Vapor-Induced Pore-Forming Atmospheric-Plasma-Sprayed Zinc-, Strontium-, and Magnesium-Doped Hydroxyapatite Coatings on Titanium Implants Enhance New Bone Formation-An In Vivo and In Vitro Investigation

OBJECTIVES

Titanium implants are regarded as a promising treatment modality for replacing missing teeth. Osteointegration and antibacterial properties are both desirable characteristics for titanium dental implants. The aim of this study was to create zinc (Zn)-, strontium (Sr)-, and magnesium (Mg)-multidoped hydroxyapatite (HAp) porous coatings, including HAp, Zn-doped HAp, and Zn-Sr-Mg-doped HAp, on titanium discs and implants using the vapor-induced pore-forming atmospheric plasma spraying (VIPF-APS) technique.

METHODS

The mRNA and protein levels of osteogenesis-associated genes such as collagen type I alpha 1 chain (COL1A1), decorin (DCN), osteoprotegerin (TNFRSF11B), and osteopontin (SPP1) were examined in human embryonic palatal mesenchymal cells. The antibacterial effects against periodontal bacteria, including Porphyromonas gingivalis and Prevotella nigrescens, were investigated. In addition, a rat animal model was used to evaluate new bone formation via histologic examination and micro-computed tomography (CT).

RESULTS

The ZnSrMg-HAp group was the most effective at inducing mRNA and protein expression of TNFRSF11B and SPP1 after 7 days of incubation, and TNFRSF11B and DCN after 11 days of incubation. In addition, both the ZnSrMg-HAp and Zn-HAp groups were effective against P. gingivalis and P. nigrescens. Furthermore, according to both in vitro studies and histologic findings, the ZnSrMg-HAp group exhibited the most prominent osteogenesis and concentrated bone growth along implant threads.

SIGNIFICANCE

A porous ZnSrMg-HAp coating using VIPF-APS could serve as a novel technique for coating titanium implant surfaces and preventing further bacterial infection.

Effects of Zinc Ions Released From Ti-NW-Zn Surface on Osteogenesis and Angiogenesis In Vitro and in an In Vivo Zebrafish Model

Zinc-modified titanium materials have been widely applied in oral implants. Among them, our previous studies have also successfully prepared a novel acid-etched microstructured titanium surface modified with zinc-containing nanowires (Ti-NW-Zn) and proved its excellent biocompatibility. It is well known that the functional regulation between angiogenesis and osteogenesis is of great importance for bone remodeling around implants. However, there are few reports concerning the biological safety of zinc ions released from materials and the appropriate concentration of released zinc ions which was more conducive to angiogenesis and bone regeneration. In this study, we investigated the effects of zinc ions released from Ti-NW-Zn surfaces on angiogenesis and osteogenesis using the zebrafish model and revealed the relationship between angiogenesis and osteogenesis via HUVECs and MC3T3-E1s in vitro. We found that the zinc ions released from Ti-NW-Zn surfaces, with a concentration lower than median lethal concentrations (LCs) of zebrafish, were biologically safe and promote osteogenesis and angiogenesis in vivo. Moreover, the proper concentration of zinc ions could induce the proliferation of HUVECs and osteogenic differentiation. The positive effects of the appropriate concentration of zinc ions on osteoblast behaviors might be regulated by activating the MAPK/ERK signaling pathway. These aspects may provide new sights into the mechanisms underlying zinc-modified titanium surfaces between osteogenesis and angiogenesis, to lay the foundation for further improving the materials, meanwhile, promoting the applications in dentistry.

Development of zinc oxide/hydroxyapatite/poly(D,L-lactic acid) fibrous scaffold for tissue engineering applications

Scaffolds based on polymeric fibers represent an engaging biomedical device due to their particular morphology and similarity with extracellular matrices. The biggest challenge to use fibrous materials in the biomedical field is related to their favorable platform for the adhesion of pathogenic microorganisms. Therefore, their optimum performance not only depends on their bioactive potential but also on their antimicrobial properties. The aim of this work was the design of antimicrobial (zinc oxide, ZnO) and bioactive (hydroxyapatite, Hap) fibrous materials using poly(D, L-lactic acid) (PDLLA) as the polymer fiber substrate. Fiber based composite scaffolds were developed using the Forcespinning® technique. For analysis purposes, the morphological, thermal, antimicrobial and biological properties of the fibrous hybrid system obtained at a concentration of 5 wt% of ZnO and 5 wt% of Hap were studied. The incorporation of the aforementioned nanoparticles (NPs) mixture in PDLLA led to an increase in viscosity and a pseudo-plastic tendency of the precursor solution, which caused an increase in fiber diameters and their dispersion of values. Small cavities and certain roughness were the main surface morphology observed on the fibers before and after NPs incorporation. The fiber thermal stability decreased due to the presence of the NPs. The antimicrobial properties of the hybrid fibrous scaffold presented a growth inhibition (GI) of 70 and 85% for E. coli and S. aureus strains, respectively. Concerning the osteoblast-cell compatibility, PDLLA and hybrid PDLLA scaffold showed low toxicity (cell viabilities above 80%), allowing cell growth inside its three-dimension structure and favorable cell morphology extended along the fibers. This behavior suggests a promising potential of this hybrid PDLLA scaffold for bone application.

Protein Immobilization on Heterogeneous (SiO2/ZnO) Hollow-Mesoporous Nanocapsules Prepared by Imprinting CPMV: Drug Delivery and Possibility of Immunological Applications

Herein, we report the protein immobilization and stability studies of heterogeneous hollow mesoporous nanocapsules (Hhmn) for drug and protein delivery. The final results of the diverse precursors such as TEOS, TMOS, APTES, and zinc acetate on the formation of the hollow-mesoporous architecture of nanocapsules have been assimilated in this work. Three types of Hhmn of various sizes were synthesized. Among the three Hhmn, sample I and II nanocapsules were synthesized in the presence of zinc acetate and were identified to be amorphous in nature. Sample III nanocapsules synthesized in the absence of zinc acetate were analogous to the other two synthesized samples. Physiochemical analysis showed the formation of zinc phosphate in the silica matrix for the samples when synthesized with zinc acetate. Specific surface area analysis revealed that sample III has a relatively higher specific surface area. Further, the drug/dye loading and release capacity for the nanocapsules were studied using doxorubicin (DOX) and imatinib mesylate (IM) as model anticancerous drugs and rhodamine 6G as a model dye. Among the synthesized nanocapsules, sample III was shown to have a higher loading capacity for DOX (∼128 μg). From the release kinetic studies of drug/dye, sample III nanocapsules demonstrate a controlled release pattern of DOX and IM. Additionally, protein adsorption and stability studies of samples I and II revealed that the BSA adsorption capacity increases with the increase in the initial concentration of BSA. Furthermore, analysis of the release profiles of BSA and OVA leads to the conclusion that the heterogeneous nanocapsules show a higher loading capacity and sustained release pattern toward OVA. These properties of the nanocapsules highlight their path to immunological applications.

Zinc Sulfate Stimulates Osteogenic Phenotypes in Periosteum-Derived Cells and Co-Cultures of Periosteum-Derived Cells and THP-1 Cells

Coupling between osteoblast-mediated bone formation and osteoclast-mediated bone resorption maintains both mechanical integrity and mineral homeostasis. Zinc is required for the formation, mineralization, growth, and maintenance of bones. We examined the effects of zinc sulfate on osteoblastic differentiation of human periosteum-derived cells (hPDCs) and osteoclastic differentiation of THP-1 cells. Zinc sulfate enhanced the osteoblastic differentiation of hPDCs; however, it did not affect the osteoclastic differentiation of THP-1 cells. The levels of extracellular signaling-related kinase (ERK) were strongly increased during osteoblastic differentiation in zinc sulfate-treated hPDCs, compared with other mitogen-activated protein kinases (MAPKs). Zinc sulfate also promoted osteogenesis in hPDCs and THP-1 cells co-cultured with the ratio of one osteoclast to one osteoblast, as indicated by alkaline phosphatase levels, mineralization, and cellular calcium contents. In addition, the receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG) ratio was decreased in the zinc sulfate-treated co-cultures. Our results suggest that zinc sulfate enhances osteogenesis directly by promoting osteoblastic differentiation and osteogenic activities in osteoblasts and indirectly by inhibiting osteoclastic bone resorption through a reduced RANKL/OPG ratio in co-cultured osteoblasts and osteoclasts.

Research status of biodegradable metals designed for oral and maxillofacial applications: A review

The oral and maxillofacial regions have complex anatomical structures and different tissue types, which have vital health and aesthetic functions. Biodegradable metals (BMs) is a promising bioactive materials to treat oral and maxillofacial diseases. This review summarizes the research status and future research directions of BMs for oral and maxillofacial applications. Mg-based BMs and Zn-based BMs for bone fracture fixation systems, and guided bone regeneration (GBR) membranes, are discussed in detail. Zn-based BMs with a moderate degradation rate and superior mechanical properties for GBR membranes show great potential for clinical translation. Fe-based BMs have a relatively low degradation rate and insoluble degradation products, which greatly limit their application and clinical translation. Furthermore, we proposed potential future research directions for BMs in the oral and maxillofacial regions, including 3D printed BM bone scaffolds, surface modification for BMs GBR membranes, and BMs containing hydrogels for cartilage regeneration, soft tissue regeneration, and nerve regeneration. Taken together, the progress made in the development of BMs in oral and maxillofacial regions has laid a foundation for further clinical translation.

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.

Accelerated Bone Regeneration by MOF Modified Multifunctional Membranes through Enhancement of Osteogenic and Angiogenic Performance

Owing to the insufficient guidance of new bone formation in orthopedic and craniomaxillofacial surgery, construction of a guided bone regeneration membrane to support vascularized bone regeneration remains a challenge. Herein, an electrospun asymmetric double-layer polycaprolactone/collagen (PCL/Col) membrane modified by metal-organic framework (MOF) crystals is developed. The optimization of the PCL/Col weight ratio (1:1 and 1:1.5) enables the composite membrane with a balanced tensile strength (only fell by 49.9% in wet conditions) and a controlled degradation rate (completely degraded at 12 weeks). The MOF crystals can provide a pH-responsive release of Zn²⁺ ions. In vitro experiments indicate that the barrier layer functions to prevent the infiltration of fibrous connective tissue. The MOF crystal layer functions to enhance osteogenesis and angiogenesis in vitro. Using a rat calvarial defect model, the MOF crystals exhibit a sign of osteoinductivity along with blood vessel formation after 8 weeks post-surgery. Strikingly, when assessed in a chick chorioallantoic membrane model, the MOF modified membrane demonstrates a significant angiogenic response, which can be envisaged as its outstanding merits over the commercially Col membrane. Therefore, the MOF crystals represent an exciting biomaterial option, with neovascularization capacity for bone tissue engineering and regenerative medicine.

Development of Multifunctional Materials Based on Poly(ether ether ketone) with Improved Biological Performances for Dental Applications

The main target for the future of materials in dentistry aims to develop dental implants that will have optimal integration with the surrounding tissues, while preventing or avoiding bacterial infections. In this project, poly(ether ether ketone) (PEEK), known for its suitable biocompa-tibility and mechanical properties for dental applications, was loaded with 1, 3, and 5 wt.% ZnO nanoparticles to provide antibacterial properties and improve interaction with cells. Sample cha-racterization by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) as well as mechanical properties showed the presence of the nanoparticles and their effect in PEEK matrices, preserving their relevant properties for dental applications. Al-though, the incorporation of ZnO nanoparticles did not improve the mechanical properties and a slight decrease in the thermal stability of the materials was observed. Hemocompatibility and osteoblasts-like cell viability tests showed improved biological performances when ZnO was present, demonstrating high potential for dental implant applications.

Nanoscale Zeolitic Imidazolate Framework-8 Activator of Canonical MAPK Signaling for Bone Repair

Zeolitic imidazolate framework-8 (ZIF-8) is an important type of metal organic framework and has found numerous applications in the biomedical field. Our previous studies have demonstrated that nano ZIF-8-based titanium implants could promote osseointegration; however, its osteogenic capacity and the related mechanisms in bone regeneration have not been fully clarified. Presented here is a nanoscale ZIF-8 that could drive rat bone mesenchymal stem cell (rBMSC) differentiation into osteoblasts both in vitro and in vivo, and interestingly, nano ZIF-8 exhibited a better osteogenic effect compared with ionic conditions of Zn at the same concentration of Zn2+. Moreover, the cellular uptake mechanisms of the nanoparticles were thoroughly clarified. Specifically, nano ZIF-8 could enter the rBMSC cytoplasm probably via caveolae-mediated endocytosis and macropinocytosis. The intracellular and extracellular Zn2+ released from nano ZIF-8 and the receptors involved in the endocytosis may play a role in inducing activation of key osteogenic pathways. Furthermore, through transcriptome sequencing, multiple osteogenic pathways were found to be upregulated, among which nano ZIF-8 primarily phosphorylated ERK, thus activating the canonical mitogen-activated protein kinase pathway and promoting the osteogenesis of rBMSCs. Taken together, this study helps to elucidate the mechanism by which nano ZIF-8 regulates osteogenesis and suggests it to be a potential biomaterial for constructing multifunctional composites in bone tissue engineering.

Biofunctional Elements Incorporated Nano/Microstructured Coatings on Titanium Implants with Enhanced Osteogenic and Antibacterial Performance

Bone fracture is prevalent among athletes and senior citizens and may require surgical insertion of bone implants. Titanium (Ti) and its alloys are widely used in orthopedics due to its high corrosion resistance, good biocompatibility, and modulus compatible with natural bone tissues. However, bone repair and regrowth are impeded by the insufficient intrinsic osteogenetic capability of Ti and Ti alloys and potential bacterial infection. The physicochemical properties of the materials and nano/microstructures on the implant surface are crucial for clinical success and loading with biofunctional elements such as Sr, Zn, Cu, Si, and Ag into nano/microstructured TiO2 coating has been demonstrated to enhance bone repair/regeneration and bacterial resistance of Ti implants. In this review, recent advances in biofunctional element-incorporated nano/microstructured coatings on Ti and Ti alloy implants are described and the prospects and limitations are discussed.

Stepwise 3D-spatio-temporal magnesium cationic niche: Nanocomposite scaffold mediated microenvironment for modulating intramembranous ossification

The fate of cells and subsequent bone regeneration is highly correlated with temporospatial coordination of chemical, biological, or physical cues within a local tissue microenvironment. Deeper understanding of how mammalian cells react to local tissue microenvironment is paramount important when designing next generation of biomaterials for tissue engineering. This study aims to investigate that the regulation of magnesium cationic (Mg²⁺) tissue microenvironment is able to convince early-stage bone regeneration and its mechanism undergoes intramembranous ossification. It was discovered that moderate Mg²⁺ content niche (~4.11 mM) led to superior bone regeneration, while Mg²⁺-free and strong Mg²⁺ content (~16.44 mM) discouraged cell adhesion, proliferation and osteogenic differentiation, thereby bone formation was rarely found. When magnesium ions diffused into free Mg zone from concentrated zone in late time point, new bone formation on free Mg zone became significant through intramembranous ossification. This study successfully demonstrates that magnesium cationic microenvironment serves as an effective biochemical cue and is able to modulate the process of bony tissue regeneration. The knowledge of how a Mg²⁺ cationic microenvironment intertwines with cells and subsequent bone formation gained from this study may provide a new insight to develop the next generation of tissue-repairing biomaterials.

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Regulation of Mg²⁺ concertation in tissue microenvironment can convince early-stage bone regeneration.

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Samples without and with strong Mg²⁺ microenvironments (16.44 mM) suppressed the osteogenic differentiation.

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When Mg²⁺ diffused into free Mg zone from concentrated zone over time, bone formation over free Mg zone becomes significant.

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Bone defect repair through intramembranous ossification was promoted by 3D-scaffold-created moderate Mg²⁺ microenvironment.

Biological responses to physicochemical properties of biomaterial surface

Biomedical scientists use chemistry-driven processes found in nature as an inspiration to design biomaterials as promising diagnostic tools, therapeutic solutions, or tissue substitutes. While substantial consideration is devoted to the design and validation of biomaterials, the nature of their interactions with the surrounding biological microenvironment is commonly neglected. This gap of knowledge could be owing to our poor understanding of biochemical signaling pathways, lack of reliable techniques for designing biomaterials with optimal physicochemical properties, and/or poor stability of biomaterial properties after implantation. The success of host responses to biomaterials, known as biocompatibility, depends on chemical principles as the root of both cell signaling pathways in the body and how the biomaterial surface is designed. Most of the current review papers have discussed chemical engineering and biological principles of designing biomaterials as separate topics, which has resulted in neglecting the main role of chemistry in this field. In this review, we discuss biocompatibility in the context of chemistry, what it is and how to assess it, while describing contributions from both biochemical cues and biomaterials as well as the means of harmonizing them. We address both biochemical signal-transduction pathways and engineering principles of designing a biomaterial with an emphasis on its surface physicochemistry. As we aim to show the role of chemistry in the crosstalk between the surface physicochemical properties and body responses, we concisely highlight the main biochemical signal-transduction pathways involved in the biocompatibility complex. Finally, we discuss the progress and challenges associated with the current strategies used for improving the chemical and physical interactions between cells and biomaterial surface.

Zinc as a Therapeutic Agent in Bone Regeneration

Zinc is an essential mineral that is required for normal skeletal growth and bone homeostasis. Furthermore, zinc appears to be able to promote bone regeneration. However, the cellular and molecular pathways through which zinc promotes bone growth, homeostasis, and regeneration are poorly understood. Zinc can positively affect chondrocyte and osteoblast functions, while inhibiting osteoclast activity, consistent with a beneficial role for zinc in bone homeostasis and regeneration. Based on the effects of zinc on skeletal cell populations and the role of zinc in skeletal growth, therapeutic approaches using zinc to improve bone regeneration are being developed. This review focuses on the role of zinc in bone growth, homeostasis, and regeneration while providing an overview of the existing studies that use zinc as a bone regeneration therapeutic.

Drug Delivery Systems Based on Titania Nanotubes and Active Agents for Enhanced Osseointegration of Bone Implants

TiO2 nanotubes (TNTs) are attractive nanostructures for localized drug delivery. Owing to their excellent biocompatibility and physicochemical properties, numerous functionalizations of TNTs have been attempted for their use as therapeutic agent delivery platforms. In this review, we discuss the current advances in the applications of TNT-based delivery systems with an emphasis on the various functionalizations of TNTs for enhancing osteogenesis at the bone-implant interface and for preventing implant-related infection. Innovation of therapies for enhancing osteogenesis still represents a critical challenge in regeneration of bone defects. The overall concept focuses on the use of osteoconductive materials in combination with the use of osteoinductive or osteopromotive factors. In this context, we highlight the strategies for improving the functionality of TNTs, using five classes of bioactive agents: growth factors (GFs), statins, plant derived molecules, inorganic therapeutic ions/nanoparticles (NPs) and antimicrobial compounds.

Zeolitic Imidazolate Framework-8 Encapsulating Risedronate Synergistically Enhances Osteogenic and Antiresorptive Properties for Bone Regeneration

Bisphosphonates (BPs) are routinely administered for the treatment of turnover bone diseases. To avoid the undesirable adverse effects of long-term usage of bisphosphonates and improve their bioavailability in the bone microenvironment, we initially encapsulated risedronate (RIS) molecules inside nanoscale zeolitic imidazolate framework-8 particles (nZIF-8) by a one-step synthesis method to generate RIS@ZIF-8 nanoparticles. RIS@ZIF-8 nanoparticles displayed high loading encapsulation efficiency (64.21 ± 2.48%), good biocompatibility, controlled drug release capacity, and dual effects for bone regeneration. This work explored the potential of RIS@ZIF-8 nanoparticles, which could not only enhance ATP production, induce extracellular matrix (ECM) mineralization, and upregulate the expression levels of osteogenic genes but also effectively inhibit the formation of multinucleated giant osteocasts and decrease the Rankl/Opg ratio. Overall, RIS@ZIF-8 nanoparticles could be a very promising approach to synergistically enhance osteogenic and antiresorptive properties for bone regeneration, which could be utilized for the local treatment of bone defects.

Heterogeneity and dynamics of active Kras-induced dysplastic lineages from mouse corpus stomach

Dysplasia is considered a key transition state between pre-cancer and cancer in gastric carcinogenesis. However, the cellular or phenotypic heterogeneity and mechanisms of dysplasia progression have not been elucidated. We have established metaplastic and dysplastic organoid lines, derived from Mist1-Kras(G12D) mouse stomach corpus and studied distinct cellular behaviors and characteristics of metaplastic and dysplastic organoids. We also examined functional roles for Kras activation in dysplasia progression using Selumetinib, a MEK inhibitor, which is a downstream mediator of Kras signaling. Here, we report that dysplastic organoids die or show altered cellular behaviors and diminished aggressive behavior in response to MEK inhibition. However, the organoids surviving after MEK inhibition maintain cellular heterogeneity. Two dysplastic stem cell (DSC) populations are also identified in dysplastic cells, which exhibited different clonogenic potentials. Therefore, Kras activation controls cellular dynamics and progression to dysplasia, and DSCs might contribute to cellular heterogeneity in dysplastic cell lineages.

Physicochemical and in-vitro biological analysis of bio-functionalized titanium samples in a protein-rich medium

The long-term survivability of the implants is strongly influenced by the osseointegration aspects of the metal-bone interface. In this study, biological materials such as fibrinogen and fibrin are used to functionalize titanium surfaces to enhance the ability of implants to interact with human tissues for accelerated osseointegration. The biofunctionalized samples that were assessed by White Light Microscope, Scanning Electron Microscope and Water Contact Angle for surface properties proved samples etched with HF/HNO₃ to be better than HCl/H₂SO₄ in terms of having optimum roughness and hydrophilicity for our further experiments. To further investigate the in vitro osseointegration of the biofunctionalized samples, Osteoblasts were cultured on the surfaces to assess cell proliferation, adhesion, gene expression as well as the mineralization process. Further bacterial adhesion (Enterococcus faecalis) and electrochemical evaluation of surface coating stability were carried out. Results of the study show that the biofunctionalized surfaces provided high cell proliferation, adherence, gene expression, and mineralization compared to other control surfaces hence proving them to have efficient and enhanced osseointegration. Also, bacterial adhesion studies show that there is no augmented growth of bacteria on the biofunctionalized samples in comparison to control surfaces. Electrochemical studies proved the existence of a stable protein layer on the bio functionalized surfaces. Such a method can reduce the time for osseointegration that can decrease risks in early failures of implants due to its enhanced hydrophilicity and cytocompatibility.

Investigating the effect of Copper Addition on SiO2-ZnO-CaO-SrO-P2O5 Glass Polyalkenoate Cements: Physical, Mechanical and Biological Behavior

The physical, mechanical, and biological behaviour of copper containing glass polyalkenotare cements were investigated, where copper (Cu2+) was incorporated into a SiO2-ZnO-CaO-SrO-P2O5 based glass system. Three GPCs were formulated for this study, a Control and two Cu-GPCs with 6 (Cu-1) and 12 (Cu-2) Mol.% of CuO substituted for the SiO2 in the glass. Rheological evaluation of GPCs determined that the addition of the Cu decreases the working and setting times in the cements. The mechanical properties of the cements were evaluated after 1 - 21 days incubation in DI water. The compressive strength of the cements were found to range between 21-36 MPa, with Cu-1 having the highest compressive strength. Biaxial flexural strength and Shear Bond Strength of the GPCs were found to increase with respect to time and were higher for the Cu-GPCs at 14 MPa and 2.1 MPa respectively. Bioactivity testing was conducted using Simulated Body Fluid (SBF) which revealed CaP precipitants on each of the GPCs surfaces. The effect o f Cu addition to the GPCs greatly enhanced the antibacterial inhibition zone (IZ) when tested in E.coli (3mm), S.aureus (24mm) and S.epidermidis (22mm). Cytocompatibility testing revealed more favorable MC3T3 osteoblast cell viability when compared to the Control GPC.

Current Trends in Fabrication of Biomaterials for Bone and Cartilage Regeneration: Materials Modifications and Biophysical Stimulations

The aim of engineering of biomaterials is to fabricate implantable biocompatible scaffold that would accelerate regeneration of the tissue and ideally protect the wound against biodevice-related infections, which may cause prolonged inflammation and biomaterial failure. To obtain antimicrobial and highly biocompatible scaffolds promoting cell adhesion and growth, materials scientists are still searching for novel modifications of biomaterials. This review presents current trends in the field of engineering of biomaterials concerning application of various modifications and biophysical stimulation of scaffolds to obtain implants allowing for fast regeneration process of bone and cartilage as well as providing long-lasting antimicrobial protection at the site of injury. The article describes metal ion and plasma modifications of biomaterials as well as post-surgery external stimulations of implants with ultrasound and magnetic field, providing accelerated regeneration process. Finally, the review summarizes recent findings concerning the use of piezoelectric biomaterials in regenerative medicine.

Bi-functional titanium-polydopamine-zinc coatings for infection inhibition and enhanced osseointegration

The ideal orthopedic implant coating is expected to both inhibit microbial infection and promote osseointegration. In this study, Zn ions were immobilized on a Ti substrate via a polydopamine (PDA) chemical surface modification to prepare Ti-PDA-Zn coatings. Scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscope (EDS), X-ray photoelectron spectroscopy (XPS), contact analysis system, and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used to analyze the morphology, composition, wettability, and zinc ions release of the coatings. The Ti-PDA-Zn coatings demonstrated excellent antibacterial activities in vitro against both Staphylococcus aureus and Escherichia coli. The coatings additionally displayed good biocompatibility, as confirmed by cytoskeletal observations and cell viability assays. Furthermore, the in vivo results confirmed the excellent antibacterial properties and improved osseointegration capability of the Ti-PDA-Zn coating in the presence of S. aureus. The present findings indicate that the Ti-PDA-Zn coatings prepared herein have potential application in orthopedic implantation.

The ideal orthopedic implant coating is expected to both inhibit microbial infection and promote osseointegration.

A review of nanostructured surfaces and materials for dental implants: surface coating, patterning and functionalization for improved performance

The emerging field of nanostructured implants has enormous scope in the areas of medical science and dental implants. Surface nanofeatures provide significant potential solutions to medical problems by the introduction of better biomaterials, improved implant design, and surface engineering techniques such as coating, patterning, functionalization and molecular grafting at the nanoscale. This review is of an interdisciplinary nature, addressing the history and development of dental implants and the emerging area of nanotechnology in dental implants. After a brief introduction to nanotechnology in dental implants and the main classes of dental implants, an overview of different types of nanomaterials (i.e. metals, metal oxides, ceramics, polymers and hydrides) used in dental implant together with their unique properties, the influence of elemental compositions, and surface morphologies and possible applications are presented from a chemical point of view. In the core of this review, the dental implant materials, physical and chemical fabrication techniques and the role of nanotechnology in achieving ideal dental implants have been discussed. Finally, the critical parameters in dental implant design and available data on the current dental implant surfaces that use nanotopography in clinical dentistry have been discussed.

Anti-inflammatory character of Phelligridin D modulates periodontal regeneration in lipopolysaccharide-induced human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Phelligridin D is a hispidin analogue from the mushroom Phellinus baumii that is widely used as a food source in East Asia. This study tested phelligridin D for the anti-inflammatory effect and mechanism in lipopolysaccharide (LPS)-induced human periodontal ligament cells (HPDLCs). The objective of this study was to clarify whether the anti-inflammatory function of phelligridin D affects periodontal regeneration for supporting the HPDLCs of teeth.

MATERIAL AND METHODS

Primary HPDLCs were isolated from healthy teeth and then cultured. The anti-inflammatory function, mechanism and differentiation molecules were verified with reactive oxygen species generation and western blot analysis in LPS-induced HPDLCs.

RESULTS

HPDLCs showed increased inflammatory molecules (intracellular adhesion molecule-1 and vascular cell adhesion molecule-1) and decreased osteogenic proteins (bone morphogenetic protein-7, Osterix and runt-related transcription factor 2) by LPS treatment. Phelligridin D decreased inflammatory molecules and increased osteogenic molecules via downregulation of the extracellular signal-regulated kinase and c-jun N-terminal kinases pathway among the mitogen-activated protein kinase, followed by blocking of nuclear factor kappa-B translocation from cytosol to nucleus. In addition, phelligridin D showed antioxidant properties by reducing reactive oxygen species activity. Finally, the anti-inflammatory and antioxidant function of phelligridin D promoted the periodontal differentiation of HPDLCs.

CONCLUSION

These results suggest that phelligridin D supports teeth on the alveolar bone against outside stress, and may be used as an anti-inflammatory compound for the prevention of periodontitis or periodontal regenerative related disease.

Icariin attenuates titanium particle-induced inhibition of osteogenic differentiation and matrix mineralization via miR-21-5p

Inhibition of bone regeneration by wear debris is the main cause of peri-prosthetic osteolysis. Here, we investigated the effect of icariin on cell proliferation, apoptosis, osteogenic differentiation and matrix mineralization of osteoblasts in an in vitro model of titanium (Ti) particle-induced osteolysis. In the present study, MC3T3-E1 cells were pretreated with 10^-8  M icariin for 4 h and then incubated with Ti particles (0.1 mg/mL). The results showed that Ti particles inhibited cell proliferation and promoted cell apoptosis of MC3T3-E1 cells, whereas icariin pretreatment blocked the effect of Ti particles. In addition, we found that icariin stimulation alone increased ALP activity, accelerated matrix mineralization and upregulated the levels of bone morphogenetic protein 2 (BMP2), Runt-related transcription factor 2 (Runx2), osteocalcin (OCN) and miR-21-5p; whereas, Ti particles alone exerted the opposite effects. Icariin partly reversed the effect of Ti particles on cell differentiation and mineralization. Twenty hours after transfection with antagomiR-21-5p or antagomiR-NC, the cells were pretreated with icariin for 4 h and then incubated with Ti particles. Further studies showed that partial knockdown of miR-21-5p abolished the promotion effect of icariin on osteoblast differentiation and matrix mineralization in Ti particle-stimulated MC3T3-E1 cells. In conclusion, miR-21-5p may be a potential pro-osteogenesis regulator and icariin may protect against Ti particle-induced inhibition of osteogenic differentiation and mineralization through upregulation of miR-21-5p.

Bio-inspired synthesis of a hierarchical self-assembled zinc phosphate nanostructure in the presence of cowpea mosaic virus: in vitro cell cycle, proliferation and prospects for tissue regeneration

Self-assembly is an important auto-organization process used in designing structural biomaterials which have the potential capability to heal tissues after traumatic injury. Although various materials having the ability to heal after injury are available, there is still a substantial need to develop new improved materials. To address this issue, we have developed hierarchical three-dimensional (3D) self-assembled zinc phosphate (Zn₃(PO₄)₂) in the presence of cowpea mosaic virus (CPMV). Zn₃(PO₄)₂ nanoparticles are self-assembled into nanosheets with a high degree of isotropy and then self-organized into a 3D structure that can enhance surface interactions with biological entities. The self-assembled structure is formed through the auto-organization of nanoparticles of size ∼50 nm under the influence of CPMV. The cellular response of self-assembled Zn₃(PO₄)₂ and cell-particle adhesion behavior have been investigated through in vitro studies using modeled osteoblast-like MG63 cells. Self-assembled Zn₃(PO₄)₂ resulted in proliferation of MG63 cells of up to 310% within 7 days of incubation. A 15% higher proliferation was obtained than with commercially available hydroxyapatite (HAp). Immunofluorescent analysis of MG63 cells after co-culturing with self-assembled Zn₃(PO₄)₂ confirmed the healthy cytoskeletal organization and dense proliferation of MG63 cells. Further, Zn₃(PO₄)₂ exhibited ∼28% cell-cycle progression in S phase, which is higher than obtained with commercially available HAp. Overall, these results demonstrate the multiple functions of hierarchical self-assembled Zn₃(PO₄)₂ in the regeneration of bone tissue without defects and increasing the formation of cellular networks, and suggest its use in bone tissue engineering.

Novel Strontium Doped Zinc Calcium Phosphate Conversion Coating on AZ31 Magnesium Alloy for Biomedical Applications

A simple chemical conversion coating was adopted to deposit zinc calcium phosphate (ZCP) coating and strontium doped ZCP (SZCP) coating on AZ31 magnesium alloy to induce biocompatibility and reduce the degradation rate. The surface morphology, chemical composition and functional groups of the coating were characterized by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), X-Ray Diffraction (XRD) studies and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy respectively. SZCP coating formed at 20 min deposition time produced crack free surface with a high degree of crystallinity with barrier property, which ultimately retards the dissolution of magnesium in Simulated Body Fluid (SBF). The corrosion resistance of AZ31 magnesium alloy was improved by SZCP coating as evident from hydrogen evolution test (HET). Cytotoxicity evaluation with L969 cells showed that Sr doped ZCP coatings showed less toxicity on resorbable magnesium alloys.

GATA4 regulates osteoblastic differentiation and bone remodeling via p38-mediated signaling

Osteoblasts play a major role in bone remodeling and are regulated by transcription factors. GATA4, a zinc finger transcription factor from the GATA family, has an unclear role in osteoblast differentiation. In this study, the role of GATA4 in osteoblast differentiation was studied both in vitro and in vivo by GATA4 knockdown. GATA4 expression increased during osteoblast differentiation. GATA4 knockdown in osteoblast precursor cells reduced alkaline phosphatase activity and decreased the formation of calcified nodule in an osteogenic-induced cell culture system. In vivo, micro-CT showed that local injection of lentivirus-delivered GATA4 shRNA caused reduced new bone formation during tooth movement. Histological analyses such as total collagen and Goldner's trichrome staining confirmed these results. In vivo immunohistochemical analysis showed reduced expression of osterix (OSX), osteopontin (OPN), and osteocalcin (OCN) in the shGATA4 group (P < 0.05). Consistently, both western blotting and quantitative reverse-transcription PCR proved that expression of osteogenesis-related genes, including OSX, OPN, and OCN, was significantly repressed in the shGATA4 group in vitro (P < 0.01). For further analysis of the pathways involved in this process, we examined the MAPK signaling pathway, and found knockdown of GATA4, downregulated p38 signaling pathways (P < 0.01). Collectively, these results imply GATA4 is a regulator of osteoblastic differentiation via the p38 signaling pathways.

Application of Stem Cells in Oral Disease Therapy: Progresses and Perspectives

Stem cells are undifferentiated and pluripotent cells that can differentiate into specialized cells with a more specific function. Stem cell therapies become preferred methods for the treatment of multiple diseases. Oral and maxillofacial defect is one kind of the diseases that could be most possibly cured by stem cell therapies. Here we discussed oral diseases, oral adult stem cells, iPS cells, and the progresses/challenges/perspectives of application of stem cells for oral disease treatment.

TiO2nanotubes enriched with calcium, phosphorous and zinc: promising bio-selective functional surfaces for osseointegrated titanium implants

TiO₂nanotubes enriched with Ca, P, and Zn by reverse polarization anodization, are promising bio-selective functional structures for osseointegrated titanium implants.