Effects of zinc on human skeletal alkaline phosphatase activity in vitro

Zinc- and Fluoride-Releasing Bioactive Glass as a Novel Bone Substitute

Bioglass 45S5, a silica-based glass, has pioneered a new field of biomaterials. Bioglass 45S5 promotes mineralization through calcium ion release and is widely used in the dental field, including toothpaste formulations. However, the use of Bioglass 45S5 for bone grafting is limited owing to the induction of inflammation, as well as reduced degradation and ion release. Phosphate-based glasses exhibit higher solubility and ion release than silica-based glass. Given that these glasses can be synthesized at low temperatures (approximately 1,000°C), they can easily be doped with various metal oxides to confer therapeutic properties. Herein, we fabricated zinc- and fluoride-doped phosphate-based glass (multicomponent phosphate [MP] bioactive glass) and further doped aluminum oxide into the MP glass (4% Al-MP glass) to overcome the striking solubility of phosphate-based glass. Increased amounts of zinc and fluoride ions were detected in water containing the MP glass. Doping of aluminum oxide into the MP glass suppressed the striking dissolution in water, with 4% Al-MP glass exhibiting the highest stability in water. Compared with Bioglass 45S5, 4% Al-MP glass in water had a notably reduced particle size, supporting the abundant ion release of 4% Al-MP glass. Compared with Bioglass 45S5, 4% Al-MP glass enhanced the osteogenesis of mouse bone marrow-derived mesenchymal stem cells. Mouse macrophages cultured with 4% Al-MP glass displayed enhanced induction of anti-inflammatory M2 macrophages and reduced proinflammatory M1 macrophages, indicating M2 polarization. Upon implanting 4% Al-MP glass or Bioglass 45S5 in a mouse calvarial defect, 4% Al-MP glass promoted significant bone regeneration when compared with Bioglass 45S5. Hence, we successfully fabricated zinc- and fluoride-releasing bioactive glasses with improved osteogenic and anti-inflammatory properties, which could serve as a promising biomaterial for bone regeneration.

GelMA-based bioactive hydrogel scaffolds with multiple bone defect repair functions: therapeutic strategies and recent advances

Currently, the clinical treatment of critical bone defects attributed to various causes remains a great challenge, and repairing these defects with synthetic bone substitutes is the most common strategy. In general, tissue engineering materials that mimic the structural, mechanical and biological properties of natural bone have been extensively applied to fill bone defects and promote in situ bone regeneration. Hydrogels with extracellular matrix (ECM)-like properties are common tissue engineering materials, among which methacrylate-based gelatin (GelMA) hydrogels are widely used because of their tunable mechanical properties, excellent photocrosslinking capability and good biocompatibility. Owing to their lack of osteogenic activity, however, GelMA hydrogels are combined with other types of materials with osteogenic activities to improve the osteogenic capability of the current composites. There are three main aspects to consider when enhancing the bone regenerative performance of composite materials: osteoconductivity, vascularization and osteoinduction. Bioceramics, bioglass, biomimetic scaffolds, inorganic ions, bionic periosteum, growth factors and two-dimensional (2D) nanomaterials have been applied in various combinations to achieve enhanced osteogenic and bone regeneration activities. Three-dimensional (3D)-bioprinted scaffolds are a popular research topic in bone tissue engineering (BTE), and printed and customized scaffolds are suitable for restoring large irregular bone defects due to their shape and structural tunability, enhanced mechanical properties, and good biocompatibility. Herein, the recent progress in research on GelMA-based composite hydrogel scaffolds as multifunctional platforms for restoring critical bone defects in plastic or orthopedic clinics is systematically reviewed and summarized. These strategies pave the way for the design of biomimetic bone substitutes for effective bone reconstruction with good biosafety. This review provides novel insights into the development and current trends of research on GelMA-based hydrogels as effective bone tissue engineering (BTE) scaffolds for correcting bone defects, and these contents are summarized and emphasized from various perspectives (osteoconductivity, vascularization, osteoinduction and 3D-bioprinting). In addition, advantages and deficiencies of GelMA-based bone substitutes used for bone regeneration are put forward, and corresponding improvement measures are presented prior to their clinical application in near future (created with BioRender.com).

Bioactive ZnO-assisted 1393 glass scaffold promotes osteogenic differentiation: Some studies

We developed ZnO-assisted 1393 bioactive glass-based scaffold with suitable mechanical properties through foam replica technique and observed to be suitable for bone tissue engineering application. However, the developed scaffolds' ability to facilitate cellular infiltration and integration was further assessed through in vivo studies in suitable animal model. Herein, the pure 1393 bioactive glass (BG) and ZnO-assisted 1393 bioactive glass- (ZnBGs; 1, 2, 4 mol% ZnO substitution for SiO₂ in pure BG is named as Z1BG, Z2BG, Z3BG, respectively) based scaffolds were prepared through sol-gel route, followed by foam replica techniques and characterized by a series of in vitro and some in vivo tests. Different cell lines like normal mouse embryonic cells (NIH/3T3), mouse bone marrow stromal cells (mBMSc), peripheral blood mononuclear cells, that is, lymphocytes and monocytes (PBMC) and U2OS (carcinogenic human osteosarcoma cells) were used in determination and comparative analysis of the biological compatibility of the BG and ZnBGs. Also, the alkaline phosphatase (ALP) activity, and osteogenic gene expression by primer-specific osteopontin (OPN), osteocalcin (OCN), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were performed to study osteogenic differentiability of the stromal cells in different BGs. Moreover, radiological and histopathological tests were performed in bone defect model of Wister rats to evaluate the in vivo bone regeneration and healing. Interestingly, these studies demonstrate augmented biological compatibility, and superior osteogenic differentiation in ZnBGs, in particular Z3BG than the pure BG in most cases.

Zinc in microscopic calcifications isolated from thyroid fine needle aspiration may serve as a biomarker of thyroid nodule malignancy: A promising proof-of-concept

Thyroid nodules (TNs) are common neck ultrasonography (US) findings, yet only 5-10% of these nodules harbor thyroid cancer (TC). When US characteristics are consistent with an intermediate or high suspicion for TN malignancy, fine needle aspiration for cytology (FNAC) is indicated. The main limitation of FNAC is that cytological results can be indeterminate in up to 30% of cases, necessitating reevaluation through repeated FNAC, expensive molecular testing, or diagnostic thyroid lobe resection. As such, there is a need for further refinement of current diagnostic algorithms for TNs without subjecting patients to additional invasive procedures. As calcifications detected during thyroid US are considered a high-risk feature for malignancy, we used the material remaining following routine thyroid FNAC to isolate microscopic calcifications (MCs). We then characterized the elemental composition, morphology, and crystal phases of these MCs, ultimately revealing differences between the MCs from benign and malignant TNs. Specifically, thyroid MCs were identified as calcium phosphate crystals containing varying levels of magnesium, sodium, iron, and zinc. MCs obtained from malignant TNs, mainly papillary thyroid carcinoma, were composed of sub-micrometer spherical particles, whereas MCs from benign TNs consisted of faceted particles. While samples from most patients with a final diagnosis of malignant TNs (50% of them with indeterminate cytology) harbored zinc-containing MCs, zinc was largely absent in MCs from benign TNs (23% with indeterminate or non-diagnostic cytology). Together, these data suggest that the presence of zinc in MCs isolated from samples collected during routine FNAC may potentially offer value as a biomarker of TN malignancy. STATEMENT OF SIGNIFICANCE: As up to 40% of patients assessed for thyroid malignancy do not receive a definite diagnosis following thyroid nodule (TN) fine needle aspiration (FNA), there is a pressing need to improve the accuracy of current diagnostic algorithms. Chemical analyses of microscopic calcifications (MCs) may serve as a diagnostic target. We developed a straightforward protocol to chemically characterize MCs from excess material collected from TNs during routine FNA and found that these MCs differed between benign and malignant TNs. Specifically, zinc in TN-derived MCs may indicate a higher nodule malignancy risk, thus increasing the diagnostic accuracy of the FNA procedure, reducing the need for recurrent biopsies and diagnostic surgical procedures, and decreasing the costs, uncertainty, and stress faced by affected patients.

Recent Trends in Hydroxyapatite Supplementation for Osteoregenerative Purposes

Bone regeneration has gained attention in the biomedical field, which has led to the development of materials and synthesis methods meant to improve osseointegration and cellular bone activity. The properties of hydroxyapatite, a type of calcium phosphate, have been researched to determine its advantages for bone tissue engineering, particularly its biocompatibility and ability to interact with bone cells. Recently, the advantages of utilizing nanomolecules of hydroxyapatite, combined with various substances, in order to enhance and combine their characteristics, have been reported in the literature. This review will outline the cellular and molecular roles of hydroxypatite, its interactions with bone cells, and its nano-combinations with various ions and natural products and their effects on bone growth, development, and bone repair.

Dietary Zinc Glycine Supplementation Improves Tibia Quality of Meat Ducks by Modulating the Intestinal Barrier and Bone Resorption

Leg problems characterized by gait abnormity and bone structure destruction are associated with a high risk of fractures and continuous pain in poultry. Zinc (Zn) acts a pivotal part in normal bone homeostasis and has proven to be highly effective in alleviating leg problems. Therefore, the effects of graded concentration of Zn on bone quality were evaluated in this study. A total of 512 1-d-old male ducks were fed 4 basal diets added 30 mg/kg Zn, 60 mg/kg Zn, 90 mg/kg Zn, and 120 mg/kg Zn as Zn glycine for 35 d. Tibia Zn content, ash percentage, and breaking strength linearly increased with dietary elevated Zn level (P < 0.05). Broken-line analysis revealed that the recommended level of Zn from Zn glycine was 55.13 mg/kg and 64.48 mg/kg based on tibia ash and strength, respectively. To further confirm the role of dietary Zn glycine addition on bone characteristics, data from birds fed either 60 mg/kg Zn as Zn sulfate (ZnSO₄), 30 mg/kg Zn, or 60 mg/kg Zn in the form of Zn glycine indicated that birds given 60 mg/kg Zn from Zn glycine diet exhibited higher tibia ash, strength, and trabecular volume compared to those fed the 30 mg/kg Zn diet (P < 0.05). Dietary 60 mg/kg Zn as Zn glycine addition decreased intestinal permeability, upregulated the mRNA expression of tight junction protein, and increased the abundance of Lactobacillus and Bifidobacterium, which was companied by declined the level of inflammatory cytokines in both the ileum and bone marrow. Regarding bone turnover, the diet with 60 mg/kg Zn from Zn glycine induced osteoprotegerin expression and thus decreased osteoclast number and serum bone resorption biomarker levels including serum tartrate-resistant acid phosphatase activity and C-terminal cross-linked telopeptide of type I collagen level when compared to 30 mg/kg Zn diet (P < 0.05). Except for the upregulation in runt-related transcription factor 2 transcription, the experimental treatments did not apparently change the bone formation biomarker contents in serum. Additionally, Zn glycine displayed a more efficient absorption rate, evidenced by higher serum Zn level, and thus had potentially greater a protective role in the intestine barrier and tibia mass as compared to ZnSO₄. Collectively, the dietary supplementation of 60 mg/kg in the form of Zn glycine could suppress bone resorption mediated by osteoclast and consequently improve tibial quality of meat ducks, in which enhanced intestinal integrity and optimized gut microbiota might be involved.

Drug Molecular Immobilization and Photofunctionalization of Calcium Phosphates for Exploring Theranostic Functions

Theranostics (bifunction of therapeutics and diagnostics) has attracted increasing attention due to its efficiency that can reduce the physical and financial burden on patients. One of the promising materials for theranostics is calcium phosphate (CP) and it is biocompatible and can be functionalized not only with drug molecules but also with rare earth ions to show photoluminescence that is necessary for the diagnostic purpose. Such the CP-based hybrids are formed in vivo by interacting between functional groups of organic molecules and inorganic ions. It is of great importance to elucidate the interaction of CP with the photofunctional species and the drug molecules to clarify the relationship between the existing state and function. Well-designed photofunctional CPs will contribute to biomedical fields as highly-functional ormultifunctional theranostic materials at the nanoscales. In this review, we describe the hybridization between CPs and heterogeneous species, mainly focusing on europium(III) ion and methylene blue molecule as the representative photofunctional species for theranostics applications.

Protective effect of zinc supplementation on tricalcium phosphate particles-induced inflammatory osteolysis in mice

Zinc (Zn), an essential trace element, can stimulate bone formation and inhibit osteoclastic bone resorption, which controls the growth and maintenance of bone. However, the effect of Zn supplementation on tricalcium phosphate (TCP) wear particles-induced osteolysis remains unknown. Here, we doped Zn into TCP particles (ZnTCP), and explore the protective effects of Zn on TCP particles-induced osteolysis in vivo. TCP particles and ZnTCP particles were embedded under the periosteum around the middle suture of the mouse calvaria. After 2 weeks, blood, the periosteal tissue, and the calvaria were collected to determine serum levels of Zn and osteocalcin, pro-inflammatory cytokines, bone biochemical markers, osteoclastogenesis and bone resorption area, and to explain its mechanism. Data revealed that Zn significantly prevented TCP particles-induced osteoclastogenesis and bone loss, and increased bone turnover. The Zn supplement remarkably suppressed the release of pro-inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Immunoblotting demonstrated that Zn alleviated expression levels of ER stress-related proteins such as glucose-regulated protein 78 (GRP78), PKR-like ER kinase (PERK), phospho-PERK (p-PERK), eukaryotic initiation factor 2α (eIF2α), phospho-eIF2α (p-eIF2α), activating transcription factor 4 (ATF4), inositol-requiring enzyme 1α (IRE1-α) and transcription factor X-box binding protein spliced (XBP1s), leading to decreasing the ratios of p-PERK/PERK and p-eIF2α/eIF2α. Taken together, Zn supplementation strongly prevents TCP particles-induced periprosthetic osteolysis via inhibition of the ER stress pathway, and it may be a novel therapeutic approach for the treatment of aseptic prosthesis loosening.

Development of orthophosphosilicate glass/poly(lactic acid) composite anisotropic scaffolds for simultaneous reconstruction of bone quality and quantity

Reconstruction of organ-specific architecture is necessary to recover the original organ function. The anisotropic structure of bone tissue is strongly related to the collagen fibril alignment and bone apatite crystal direction. Bone regeneration indicates following two main process; first, restoration of bone mineral density (BMD; bone quantity), and second, restoring bone apatite c-axis orientation (bone quality). In addition to BMD, bone quality is the most important factor among bone mechanical properties. Recovery of the original bone function requires development of novel scaffolds with simultaneous reconstruction of bone quality and quantity. Herein, novel orthophosphosilicate glass (PSG)/poly(lactic acid) composite anisotropic scaffolds were developed to control cell alignment and enhance bone formation, which are important for the simultaneous reconstruction of bone quality and quantity. The strategy to control cell alignment and bone formation involved designing anisotropic scaffolds in combination with the release of therapeutic ions by PSGs. The morphology of fibrous scaffolds containing PSGs was quantitatively designed using electrospinning. This successfully modulated cell alignment and subsequent bone apatite c-axis orientation along the fiber-oriented direction. The released silicate and Mg2+ ions from PSGs in scaffolds improved cell adhesion, proliferation, and calcification. To best of our knowledge, this is the first report demonstrating that the anisotropic scaffolds containing bioactive glasses regenerate bone tissues with simultaneous reconstruction of bone quality and quantity via stimulating osteoblasts by inorganic ions and designing morphology of scaffolds.

Vitamin B9 derivatives as carriers of bioactive cations for musculoskeletal regeneration applications: Synthesis, characterization and biological evaluation

The development of new drugs for musculoskeletal regeneration purposes has attracted much attention in the last decades. In this work, we present three novel vitamin B9 (folic acid)-derivatives bearing divalent cations (ZnFO, MgFO and MnFO), providing their synthesis mechanism and physicochemical characterization. In addition, a strong emphasis has been placed on evaluating their biological properties (along with our previously reported SrFO) using human mesenchymal stem cells (hMSC). In all the cases, pure folate derivatives (MFOs) with a bidentate coordination mode between the metal and the folate anion, and a 1:1 stoichiometry, were obtained in high yields. A non-cytotoxic dose of all the MFOs (50 μg/mL) was demonstrated to modulate by their own the mRNA profiles towards osteogenic-like or fibrocartilaginous-like phenotypes in basal conditions. Moreover, ZnFO increased the alkaline phosphatase activity in basal conditions, while both ZnFO and MnFO increased the matrix mineralization degree in osteoinductive conditions. Thus, we have demonstrated the bioactivity of these novel compounds and the suitability to further studied them in vivo for musculoskeletal regeneration applications.

Zn- or Cu-containing CaP-Based Coatings Formed by Micro-Arc Oxidation on Titanium and Ti-40Nb Alloy: Part II-Wettability and Biological Performance

This work describes the wettability and biological performance of Zn- and Cu-containing CaP-based coatings prepared by micro-arc oxidation on pure titanium (Ti) and novel Ti-40Nb alloy. Good hydrophilic properties of all the coatings were demonstrated by the low contact angles with liquids, not exceeding 45°. An increase in the applied voltage led to an increase of the coating roughness and porosity, thereby reducing the contact angles to 6° with water and to 17° with glycerol. The free surface energy of 75 ± 3 mJ/m² for all the coatings were determined. Polar component was calculated as the main component of surface energy, caused by the presence of strong polar PO₄³⁻ and OH⁻ bonds. In vitro studies showed that low Cu and Zn amounts (~0.4 at.%) in the coatings promoted high motility of human adipose-derived multipotent mesenchymal stromal cells (hAMMSC) on the implant/cell interface and subsequent cell ability to differentiate into osteoblasts. In vivo study demonstrated 100% ectopic bone formation only on the surface of the CaP coating on Ti. The Zn- and Cu-containing CaP coatings on both substrates and the CaP coating on the Ti-40Nb alloy slightly decreased the incidence of ectopic osteogenesis down to 67%. The MAO coatings showed antibacterial efficacy against Staphylococcus aureus and can be arranged as follows: Zn-CaP/Ti > Cu-CaP/TiNb, Zn-CaP/TiNb > Cu-CaP/Ti.

Biomimetic trace metals improve bone regenerative properties of calcium phosphate bioceramics

The bone regenerative capacity of synthetic calcium phosphates (CaPs) can be enhanced through the enrichment with selected metal trace ions. However, defining the optimal elemental composition required for bone formation is challenging due to many possible concentrations and combinations of these elements. We hypothesized that the ideal elemental composition exists in the inorganic phase of the bone extracellular matrix (ECM). To study our hypothesis, we first obtained natural hydroxyapatite through the calcination of bovine bone, which was then investigated its reactivity with acidic phosphates to produce CaP cements. Bioceramic scaffolds fabricated using these cements were assessed for their composition, properties, and in vivo regenerative performance and compared with controls. We found that natural hydroxyapatite could react with phosphoric acid to produce CaP cements with biomimetic trace metals. These cements present significantly superior in vivo bone regenerative performance compared with cements prepared using synthetic apatite. In summary, this study opens new avenues for further advancements in the field of CaP bone biomaterials by introducing a simple approach to develop biomimetic CaPs. This work also sheds light on the role of the inorganic phase of bone and its composition in defining the regenerative properties of natural bone xenografts.

Effect of zinc substitution in hydroxyapatite coating on osteoblast and osteoclast differentiation under osteoblast/osteoclast co-culture

Zinc is an essential trace element required for bone remodelling process, but its role in such process remains to be elucidated. In particular, inconsistent results have been reported on the effect of Zn on osteoclastic responses, and supplement of receptor activator of nuclear factor kappa-B ligand (RANKL) factors has been commonly adopted. Co-culture is a suitable approach to elucidating the role of Zn in bone remodelling process, by better imitating the cellular environment as the presence of osteoblasts plays critical role in modulating osteoclastic functions. In this study, zinc-substituted HA coatings have been deposited using a liquid precursor plasma spraying process at two different concentrations (1, 2 wt.%). The effect of zinc substitution on osteoblastic and osteoclastic differentiation has been studied in vitro. In particular, a cultivation regime was designed to first induce osteoblastic differentiation of rat bone marrow stromal cells (BMSCs) for 14 days, and then induce osteoclastic differentiation of osteoclast-like precursor RAW 264.7 cells through the aid of the osteoblasts formed for additional 14 days, in the absence of the external addition of RANKL. The results showed that Zn substitution moderately promoted the BMSC differentiation into the osteoblasts and reduced the osteoclastic activity in early time (1 day co-culture). However, promotion of the osteoclastic activity were observed at later stages, as indicated by the significantly enhanced expressions of trap5b and IL-1 (8- and 15-day co-culture) and moderate stimulation of the nucleus integration and formation of the multinucleated cells (14-day co-culture). Such stimulating effect of the osteoclastic activity was absent under mono-culture of RAW 264.7 cell, with simple RANKL supplementation. The results suggest that both the zinc and the presence of MSC/osteoblast play profound and highly interacted roles on osteoclast differentiation and activity, which is critical in modulating the bone remodelling process.

Disruption of Bone Zinc Metabolism during Postnatal Development of Rats after Early Life Exposure to Cadmium

This current study was conducted to investigate whether bone tissue impairment induced by early life exposure to cadmium (Cd) during postnatal development could result from disruption to zinc (Zn) metabolism. For this reason, the offspring from mothers receiving either tap water, Cd, Zn or Cd + Zn during gestation and lactation periods were euthanized at PND21 and PND70. At the end of the lactation period (PND21), our results showed that exposure to Cd increased Cd accumulation and Zn depletion in the femur. Furthermore, calcium (Ca) level was reduced. At the molecular level, Cd induced an increase of MT-1 expression and caused an upregulation of ZIP2 accompanied with a down-regulation of ZnT5. Runx2, ALP, colα-1 and Oc mRNA levels were also decreased. In plasma, IGF-1 and osteocalcin concentrations were decreased. Further, Cd altered femoral growth by generating changes in the growth plate. Consequently, the toxic effect of Cd persisted at adult age (PND70) by decreasing bone volume (%BV/TV), bone mineral density (BMD) and Ca content and by increasing trabecular separation (Tb.Sp) in the distal femur. Interestingly, Zn supply provided total or partial corrections of several toxic effects of Cd. These data suggest that the increases of Zn bioavailability as well as the reduction of Cd accumulation in the femur following the changes in ZIP2 and ZnT5 expression are part of the mechanism involved in Zn protection against Cd toxicity on bone tissue.

Zinc doping induced differences in the surface composition, surface morphology and osteogenesis performance of the calcium phosphate cement hydration products

In order to investigate the influence of Zn on the hydration reaction of calcium phosphate cement (CPC), the incompletely hydrated CPC tablets were kept soaking in varying zinc-containing tris-(hydroxymethyl)-aminomethane/hydrochloric acid (Zn-Tris-HCl) buffers. It was found that Zn could retard the CPC hydration, the inhibitory effect was in direct proportional to the Zn content in the Zn-Tris-HCl buffer, and overhigh concentration of Zn (≧800 μM) caused the CPC hydration products having different phase composition and surface morphology. Cell culture experimental results revealed the CPC tablets which were soaked in the Zn-Tris-HCl buffer containing relative low Zn content (≦320 μM) favored the mouse bone mesenchymal stem cells (mBMSCs) spreading. When Zn-doped CPC tablets released 10.91 to 27.15 μM of zinc ions into the cell culture medium, it greatly contributed to the improvement of the proliferation ability and the alkaline phosphatase (ALP) activity of the mBMSCs. In the same case, the expression of osteogenesis related genes such as collagen I and runt-related transcription factor 2 was remarkably up-regulated as well. However, the release of high concentration of Zn (128.58 μM) would significantly reduce the ALP activity of the mBMSCs. Therefore, Zn not only facilitates osteogenesis but also affects the CPC hydration behavior, and the CPC with suitable Zn dosage concentration has great potentials to be used for clinical bone repairing.

Effects of ZnO addition on thermal properties, degradation and biocompatibility of P45Mg24Ca16Na(15−x)Znx glasses

Four phosphate-based glass formulations in the system P45Mg24Ca16Na(15−x)Znx, referred to as P45Znx (x = 0, 5, 10 and 15 mol%), were prepared using a melt quenching process. The effect of ZnO addition on density, molar volume, thermal properties and degradation rates were studied. An increase in the glass transition, crystallisation, melting and liquidus temperatures were seen when replacing Na2O with ZnO. The molar volume of the bulk glasses was seen to decrease with increasing ZnO content. The dissolution rate of the zinc-free glass was 2.48 × 10−8 kg m−2 s−1 and addition of 5 mol% ZnO resulted in a reduction of the dissolution rate to 1.68 × 10−8 kg m−2 s−1. However, further addition of ZnO from 5 mol% to 15 mol% increased the dissolution rate of the glass system. The glasses were deliberately crystallised and XRD studies identified the Z n2P2O7 phase for glass code P45Zn5, and Zn(PO3)2 phase for P45Zn10 and P45Zn15 glasses. Cyto-compatibility studies were conducted using MG63 cells for 14 days. An overall increase in the metabolic activity and DNA concentration of cells was seen from day 1 to day 14 for all glass formulations investigated. However, increasing ZnO content from 0 to 15 mol% seemed to have a negative effect on the cellular activity. Interestingly, a remarkably higher ALP activity was seen at day 14 for glass codes P45Zn5 and P45Zn10 in comparison with the TCP control and the P45Zn0 glass.

Eggshell particle-reinforced hydrogels for bone tissue engineering: an orthogonal approach

Eggshell microparticle-reinforced hydrogels have been fabricated and characterized to obtain mechanically stable and biologically active scaffolds that can direct the differentiation of cells.

Comparing the Effects of Chitosan Scaffolds Containing Various Divalent Metal Phosphates on Osteogenic Differentiation of Stem Cells from Human Exfoliated Deciduous Teeth

Inducing the differentiation of stem cells from human exfoliated deciduous teeth (SHEDs) proceeds with low efficiency, which greatly limits clinical applications. Divalent metal elements play an important role in osteoinductivity for bone remodeling because they can simulate bone formation and decrease bone resorption. The purpose of this study was to investigate the effect of some divalent metal phosphates on osteogenic differentiation from human exfoliated deciduous teeth. These divalent metal ions can be gradually released from the scaffold into the culture medium and continually induce osteoblastic differentiation. Experimental results revealed that SHEDs cultured in chitosan scaffolds containing divalent metal phosphates had notably increased osteoblastic differentiation compared with cells cultured without divalent metal phosphates. This effect was due to the high activity of alkaline phosphatase, as well as the bone-related gene expression of collagen type I, Runx2, osteopontin, osteocalcin, VEGF, and Ang-1, shown through RT-PCR and bone-related protein immunocytochemistry stains. A calcium-content assay further revealed significant enhancement of deposited minerals on the scaffolds after 21 days of culture, particularly for magnesium phosphate and zinc phosphate. Thus, divalent metals, except for barium phosphate, effectively promoted SHED cell differentiation and osteoblastic cell maturation. This study demonstrated that the divalent metal elements magnesium, strontium, and zinc could effectively induce SHED osteoblastic differentiation for use in tissue engineering and bone repair.

Environment-Friendly Synthesis of Trace Element Zn, Sr, and F Codoping Hydroxyapatite with Non-cytotoxicity and Improved Osteoblast Proliferation and Differentiation

Hydroxyapatite (HAp, Ca₁₀[PO₄]₆[OH]₂) doped with numerous trace elements possesses sensational biochemical effects in natural bones. To study the biochemical function of Zn, Sr, and F elements, a series of neoteric HAp biomaterials with Zn, Sr, and F concentrations close to natural bones are firstly synthesized by one-pot hydrothermal method. These materials are characterized through powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). All the synthesized materials are HAp phase. The morphology of these materials is nanorods. The phenomenon that L929 cells can live even at 400 μg/mL powder concentration indicates that these materials are non-cytotoxic. The active effects of samples on proliferation and differentiation of osteoblast cells (MC3T3-E1) are certified by MTT and alkaline phosphatase (ALP) activity assays. The adhesion and proliferation of osteoblast measurement manifest that amounts of MC3T3-E1 advances about 1.86 times for ZnSrF/HAp compared with undoped HAp. This achievement may inspire us on the artificial design of new-style bionic bone grafts using trace bioactive elements and also suggest its latent applications in orthopedic surgery and bone osseointegration.

Bone grafts and biomaterials substitutes for bone defect repair: A review

Bone grafts have been predominated used to treat bone defects, delayed union or non-union, and spinal fusion in orthopaedic clinically for a period of time, despite the emergency of synthetic bone graft substitutes. Nevertheless, the integration of allogeneic grafts and synthetic substitutes with host bone was found jeopardized in long-term follow-up studies. Hence, the enhancement of osteointegration of these grafts and substitutes with host bone is considerably important. To address this problem, addition of various growth factors, such as bone morphogenetic proteins (BMPs), parathyroid hormone (PTH) and platelet rich plasma (PRP), into structural allografts and synthetic substitutes have been considered. Although clinical applications of these factors have exhibited good bone formation, their further application was limited due to high cost and potential adverse side effects. Alternatively, bioinorganic ions such as magnesium, strontium and zinc are considered as alternative of osteogenic biological factors. Hence, this paper aims to review the currently available bone grafts and bone substitutes as well as the biological and bio-inorganic factors for the treatments of bone defect.

Magnesium and zinc borate enhance osteoblastic differentiation of stem cells from human exfoliated deciduous teeth in vitro

Various biocompatible and biodegradable scaffolds blended with biochemical signal molecules with adequate osteoinductive and osteoconductive properties have attracted significant interest in hard tissue engineering regeneration. We evaluated the distinct effects of magnesium borate, zinc borate, and boric acid blended into chitosan scaffold for osteogenic differentiation of stem cells from exfoliated deciduous teeth. Stem cells from exfoliated deciduous teeth cells are a potential source of functional osteoblasts for applications in bone tissue engineering, but the efficiency of osteoblastic differentiation is low, thereby significantly limiting their clinical applications. Divalent metal borates have potential function in bone remodeling because they can simulate bone formation and decrease bone resorption. These magnesium, zinc, and B ions can gradually be released into the culture medium from the scaffold and induce advanced osteoblastic differentiation from stem cells from exfoliated deciduous teeth. Stem cells from exfoliated deciduous teeth with magnesium borate or zinc borate as inducer demonstrated more osteoblastic differentiation after 21 days of culture. Differentiated cells exhibited activity of alkaline phosphatase, bone-related gene expression of collagen type I, runt-related transcription factor 2, osteopontin, osteocalcin, vascular endothelial growth factor, and angiopoietin-1, as noted via real-time polymerase chain reaction analysis, as well as significant deposits of calcium minerals. Divalent mental magnesium and zinc and nonmetal boron can be an effective inducer of osteogenesis for stem cells from exfoliated deciduous teeth. This experiment might provide useful inducers for osteoblastic differentiation of stem cells from exfoliated deciduous teeth for tissue engineering and bone repair.

Involvement of Zn Depletion in Cd-Induced Toxicity on Prenatal Bone Formation in Rat

This study explored the potential toxicity of Cd on the Zn bone depletion in prenatal bone formation. Female rats received either tap water, Cd, Zn, or Cd + Zn in their drinking water during gestation, and some markers of bone formation were studied in their fetuses removed at the 20th day of pregnancy (GD20). Cd exposure induced maternal hypozincemia and Zn depletion in the femur of the fetuses. A striking inhibition of bone formation in fetuses, expressed by decreases in femur length, width, and area, by the shortening of diaphysis, and by a decrease in length and area of distal and proximal proliferative zones, was observed in fetuses from Cd-exposed mothers. At the molecular level, Cd caused upregulation of MT-1 and ZIP2 genes and significantly depressed the expression of the ZnT5, colα1, osteocalcin, and ALP genes in the femur. Interestingly, Zn treatment ameliorated the Cd-induced maternal hypozincemia and femoral changes and partially restored the normal histomorphometry of the femur. These results suggest that the observed toxic effects of Cd are, at least in part, mediated by the disruption of maternal Zn metabolism during pregnancy leading to Zn depletion and thus to perturbation of prenatal bone formation.

Electro-chemical deposition of nano hydroxyapatite-zinc coating on titanium metal substrate

BACKGROUND

Titanium is an inert metal that does not induce osteogenesis and has no antibacterial properties; it is proposed that hydroxyapatite coating can enhance its bioactivity, while zinc can contribute to antibacterial properties and improve osseointegration.

AIMS

A nano-sized hydroxyapatite-zinc coating was deposited on commercially pure titanium using an electro-chemical process, in order to increase its surface roughness and enhance adhesion properties.

METHODS

The hydroxyapatite-zinc coating was attained using an electro-chemical deposition in a solution composed of a naturally derived calcium carbonate, di-ammonium hydrogen phosphate, with a pure zinc metal as the anode and titanium as the cathode. The applied voltage was -2.5 for 2 h at a temperature of 85 °C. The resultant coating was characterized for its surface morphology and chemical composition using a scanning electron microscope (SEM), energy dispersive x-ray spectroscope (EDS), and Fourier transform infrared (FT-IR) spectrometer. The coated specimens were also evaluated for their surface roughness and adhesion quality.

RESULTS

Hydroxyapatite-zinc coating had shown rosette-shaped, homogenous structure with nano-size distribution, as confirmed by SEM analysis. FT-IR and EDS proved that coatings are composed of hydroxyapatite (HA) and zinc. The surface roughness assessment revealed that the coating procedure had significantly increased average roughness (Ra) than the control, while the adhesive tape test demonstrated a high-quality adhesive coat with no laceration on tape removal.

CONCLUSIONS

The developed in vitro electro-chemical method can be employed for the deposition of an even thickness of nano HA-Zn adhered coatings on titanium substrate and increases its surface roughness significantly.

Structural Characterization and Antifungal Studies of Zinc-Doped Hydroxyapatite Coatings

The present study is focused on the synthesis, characterization and antifungal evaluation of zinc-doped hydroxyapatite (Zn:HAp) coatings. The Zn:HAp coatings were deposited on a pure Si (Zn:HAp_Si) and Ti (Zn:HAp_Ti) substrate by a sol-gel dip coating method using a zinc-doped hydroxyapatite nanogel. The nature of the crystal phase was determined by X-ray diffraction (XRD). The crystalline phase of the prepared Zn:HAp composite was assigned to hexagonal hydroxyapatite in the P63/m space group. The colloidal properties of the resulting Zn:HAp (xZn = 0.1) nanogel were analyzed by Dynamic Light Scattering (DLS) and zeta potential. Scanning Electron Microscopy (SEM) was used to investigate the morphology of the zinc-doped hydroxyapatite (Zn:HAp) nanogel composite and Zn:HAp coatings. The elements Ca, P, O and Zn were found in the Zn:HAp composite. According to the EDX results, the degree of Zn substitution in the structure of Zn:HAp composite was 1.67 wt%. Moreover, the antifungal activity of Zn:HAp_Si and Zn:HAp_Ti against Candida albicans (C. albicans) was evaluated. A decrease in the number of surviving cells was not observed under dark conditions, whereas under daylight and UV light illumination a major decrease in the number of surviving cells was observed.

Promotive Effect of Zinc Ions on the Vitality, Migration, and Osteogenic Differentiation of Human Dental Pulp Cells

Zinc is an essential trace element for proper cellular function and bone formation. However, its exact role in the osteogenic differentiation of human dental pulp cells (hDPCs) has not been fully clarified before. Here, we speculated that zinc may be effective to regulate their growth and osteogenic differentiation properties. To test this hypothesis, different concentrations (1 × 10^-5, 4 × 10^-5, and 8 × 10^-5 M) of zinc ions (Zn²⁺) were added to the basic growth culture medium and osteogenic inductive medium. Cell viability and migration were measured by cell counting kit-8 (CCK-8) and transwell migration assay in the basic growth culture medium, respectively. The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the gene expression levels of selective osteogenic differentiation markers and zinc transporters. Alkaline phosphatase (ALP) activity analysis and alizarin red S staining were used to investigate the mineralization of hDPCs. Exposure of hDPCs to Zn²⁺ stimulated their viability and migration capacity in a dose- and time-dependent manner. RT-qPCR assay revealed elevated expression levels of osteogenic differentiation-related genes and zinc transporters genes in various degrees. ALP activity was also increased with elevated Zn²⁺ concentrations and extended culture periods, but enhanced matrix nodules formation were observed only in 4 × 10^-5 and 8 × 10^-5 M Zn²⁺ groups. These findings suggest that specific concentrations of Zn²⁺ could potentiate the vitality, migration, and osteogenic differentiation of hDPCs. We may combine optimum zinc element into pulp capping materials to improve their biological performance.

Synchrotron radiation micro X-ray fluorescence spectroscopy of thin structures in bone samples: comparison of confocal and color X-ray camera setups

In the quest for finding the ideal synchrotron-radiation-induced imaging method for the investigation of trace element distributions in human bone samples, experiments were performed using both a scanning confocal synchrotron radiation micro X-ray fluorescence (SR-µXRF) (FLUO beamline at ANKA) setup and a full-field color X-ray camera (BAMline at BESSY-II) setup. As zinc is a trace element of special interest in bone, the setups were optimized for its detection. The setups were compared with respect to count rate, required measurement time and spatial resolution. It was demonstrated that the ideal method depends on the element of interest. Although for Ca (a major constituent of the bone with a low energy of 3.69 keV for its Kα XRF line) the color X-ray camera provided a higher resolution in the plane, for Zn (a trace element in bone) only the confocal SR-µXRF setup was able to sufficiently image the distribution.

Increased zinc accumulation in mineralized osteosarcoma tissue measured by confocal synchrotron radiation micro X-ray fluorescence analysis

Abnormal tissue levels of certain trace elements such as zinc (Zn) were reported in various types of cancer. Little is known about the role of Zn in osteosarcoma. Using confocal synchrotron radiation micro X-ray fluorescence analysis, we characterized the spatial distribution of Zn in high-grade sclerosing osteosarcoma of nine patients (four women/five men; seven knee/one humerus/one femur) following chemotherapy and wide surgical resection. Levels were compared with adjacent normal tissue. Quantitative backscattered electron imaging as well as histological examinations was also performed. On average, the ratio of medians of Zn count rates (normalized to calcium) in mineralized tumor tissue was about six times higher than in normal tissue. There was no difference in Zn levels between tumor fraction areas with a low fraction and a high fraction of mineralized tissue, which were clearly depicted using quantitative backscattered electron imaging. Moreover, we found no correlation between the Zn values and the type of tumor regression according to the Salzer-Kuntschik grading. The underlying mechanism of Zn accumulation remains unclear. Given the emerging data on the role of trace elements in other types of cancer, our novel results warrant further studies on the role of trace elements in bone cancer. Copyright © 2016 The Authors. X-Ray Spectrometry published by John Wiley & Sons Ltd.

ZnO quantum dots modified bioactive glass nanoparticles with pH-sensitive release of Zn ions, fluorescence, antibacterial and osteogenic properties

Zinc (Zn)-containing materials have osteogenic and antibacterial activities while bioactive glass nanoparticles (BGN) show bone-bonding ability, as well as osteoconductive and osteoinductive properties. Zn-containing BGN are therefore considered to be promising materials for various biomedical applications, particularly in bone regeneration. In this study, we report a convenient method to prepare Zn-containing BGN by coating ZnO quantum dots (QDs) on BGN via electrostatic interactions. The synthesized ZnO-BGN nanocomposite particles are spherical and highly dispersed, and exhibit a unique fluorescence behavior under UV excitation, emitting three wavelengths in the violet, blue and green range. ZnO-BGN showed apatite-forming ability upon immersion in simulated body fluid, but their apatite formation was delayed compared to BGN. Interestingly, ZnO-BGN showed a rapid release of Zn ions at pH 4 but a far slower release at pH 7.4. ZnO-BGN also exhibited antibacterial effects on both Gram-positive and Gram-negative bacteria at the concentrations of 1, 0.1, and 0.01 mg mL^-1. Higher concentrations could lead to stronger antibacterial effects. The LDH and live/dead assays indicated that ZnO-BGN had no significant cytotoxicity towards human mesenchymal stem cells (hMSC) at concentration of 0.1 and 0.01 mg mL^-1, but ZnO-BGN inhibited the relative proliferation of hMSC compared to BGN and the control according to the MTT assay. Notably ZnO-BGN improved the osteogenic differentiation of hMSC as indicated by the determination of the alkaline phosphatase activity. In conclusion, coating quantum dots on BGN is a promising strategy to produce Zn-containing BGN. The synthesized ZnO-BGN are potential materials for bone regeneration, considering their apatite-forming ability, unique ion-release behavior, effective antibacterial activity, non-cytotoxicity, and osteogenic potential.

Facile microwave-assisted synthesis of Te-doped hydroxyapatite nanorods and nanosheets and their characterizations for bone cement applications

In this work, the authors have fabricated the nanorods and nanosheets of pure and Te-doped HAp with different Te concentrations (0.04, 0.08, 0.16, 0.24wt%) by microwave-assisted technique at low temperature. The crystallite size, degree of crystallinity and lattice parameters are calculated. FE-SEM study confirms that the fabricated nanostructures are nanorods of diameter about 10nm in undoped and at low concentration of Te doping. However, at and higher concentration, it becomes nanosheets of about 5nm thickness. X-ray diffraction, FT-IR and FT-Raman studies shows that the prepared products are of HAp and Te has been successfully incorporated. From EDX the Ca/P molar ratio of the pure HAp is about 1.740, while this ratio for 0.04, 0.08, 0.16, 0.24 wt% Te doped is about 1.53, 1.678, 1.724, 1.792, respectively. Crystallite size was found to be increased with Te doping from 15nm to 62nm. The value of dielectric constant is found to be enhanced at higher concentrations of Te. The values of linear absorption coefficient were also determined and show that the prepared material with Te doping is more absorbable than pure and will be highly applicable in radiation detection applications. Furthermore, the antimicrobial potential of pure and Te doped HAp was examined against some Gram- negative and positive bacteria and fungi by agar disk diffusion method. The results demonstrated that the antimicrobial activity of Te doped HAp is stronger than that of pure HAp where it exhibited the highest activity against Bacillus subtilis>Candida albicans>Shigella dysenteriae.

Pathophysiology of hypophosphatasia and the potential role of asfotase alfa

Hypophosphatasia (HPP) is an inherited systemic bone disease that is characterized by bone hypomineralization. HPP is classified into six forms according to the age of onset and severity as perinatal (lethal), perinatal benign, infantile, childhood, adult, and odontohypophosphatasia. The causative gene of the disease is the ALPL gene that encodes tissue-nonspecific alkaline phosphatase (TNAP). TNAP is expressed ubiquitously, and its physiological role is apparent in bone mineralization. A defect in bone mineralization can manifest in several ways, including rickets or osteomalacia in HPP patients. Patients with severe forms suffer from respiratory failure because of hypoplastic chest, which is the main cause of death. They sometimes present with seizures due to a defect in vitamin B₆ metabolism resulting from the lack of alkaline phosphatase activity in neuronal cells, which is also lethal. Patients with a mild form of the disease exhibit rickets or osteomalacia and a functional defect of exercise. Odontohypophosphatasia shows only dental manifestations. To date, 302 mutations in the ALPL gene have been reported, mainly single-nucleotide substitutions, and the relationships between phenotype and genotype have been partially elucidated. An established treatment for HPP was not available until the recent development of enzyme replacement therapy. The first successful enzyme replacement therapy in model mice using a modified human TNAP protein (asfotase alfa) was reported in 2008, and subsequently success in patients with severe form of the disease was reported in 2012. In 2015, asfotase alfa was approved in Japan in July, followed by in the EU and Canada in August, and then by the US Food and Drug Administration in the USA in October. It is expected that therapy with asfotase alfa will drastically change treatments and prognosis of HPP.

Different response of osteoblastic cells to Mg(2+), Zn(2+) and Sr(2+) doped calcium silicate coatings

Mg(2+), Zn(2+) and Sr(2+) substitution for Ca(2+) in plasma sprayed calcium silicate (Ca-Si) coatings have been reported to impede their degradation in physiological environment and, more importantly, to improve their biological performance. The reason for the improved biological performance is still elusive and, especially, the contribution of the dopant ions is lack of obvious and direct evidence. In this study, we aim to identify the effect of Mg(2+), Zn(2+) and Sr(2+) incorporation on the osteogenic ability of Ca-Si based coatings (Ca2MgSi2O7, Ca2ZnSi2O7 and Sr-CaSiO3) by minimizing the influence of Ca and Si ions release and surface physical properties. Similar surface morphology, crystallinity and roughness were achieved for all samples by optimizing the spray parameters. As expected, Ca and Si ions release from all the coatings showed the comparable concentration with immersing time. The response of MC3T3-E1 cells onto Mg(2+), Zn(2+) and Sr(2+) doped Ca-Si coatings were studied in terms of osteoblastic adhesion, proliferation, differentiation and mineralization. The results showed that the level of cell adhesion and proliferation increased the most on the surface of Mg-modified coating. Gene expressions of early markers of osteoblast differentiation (COL-I and ALP mRNA) were obviously improved on Zn-modified coating. Gene expressions of later markers for osteoblast differentiation (OPN and OC mRNA) and mineralized nodules formation were obviously accelerated on the surface of Sr-modified coating. Since Mg(2+), Zn(2+) and Sr(2+) play a regulatory role in different stages of osteogenesis, it may be possible to utilize this in the development of new coating materials for orthopedic application.

A comparative study of zinc, magnesium, strontium-incorporated hydroxyapatite-coated titanium implants for osseointegration of osteopenic rats

Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for the implants in cementless arthroplasty. However, its effect is not sufficient for osteoporotic bone. Zinc (Zn), magnesium (Mg), and strontium (Sr) present a beneficial effect on bone growth, and positively affect bone regeneration. The aim of this study was to confirm the different effects of the fixation strength of Zn, Mg, Sr-substituted hydroxyapatite-coated (Zn-HA-coated, Mg-HA-coated, Sr-HA-coated) titanium implants via electrochemical deposition in the osteoporotic condition. Female Sprague-Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group HA; group Zn-HA; group Mg-HA and group Sr-HA. Afterwards, all rats from groups HA, Zn-HA, Mg-HA and Sr-HA received implants with hydroxyapatite containing 0%, 10% Zn ions, 10% Mg ions, and 10% Sr ions. Implants were inserted bilaterally in all animals until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. All treatment groups increased new bone formation around the surface of titanium rods and push-out force; group Sr-HA showed the strongest effects on new bone formation and biomechanical strength. Additionally, there are significant differences in bone formation and push-out force was observed between groups Zn-HA and Mg-HA. This finding suggests that Zn, Mg, Sr-substituted hydroxyapatite coatings can improve implant osseointegration, and the 10% Sr coating exhibited the best properties for implant osseointegration among the tested coatings in osteoporosis rats.

TiO2 nanotube composite layers as delivery system for ZnO and Ag nanoparticles - an unexpected overdose effect decreasing their antibacterial efficacy

Enhancement of biocompatibility and antibacterial properties of implant materials is potentially beneficial for their practical value. Therefore, the use of metallic and metallic oxide nanoparticles as antimicrobial coatings components which induce minimized antibacterial resistance receives currently particular attention. In this work, TiO2 nanotubes layers loaded with ZnO and Ag nanoparticles were designed for biomedical coatings and delivery systems and evaluated for antimicrobial activity. TiO2 nanotubes themselves exhibited considerable and diameter-dependent antibacterial activity against planktonic Staphylococcus epidermidis cells but favored bacterial adhesion. Loading of nanotubes with moderate amount of ZnO nanoparticles significantly diminished S. epidermidis cell adhesion and viability just after 1.5h contact with modified surfaces. However, an increase of loaded ZnO amount unexpectedly altered the structure of nanoparticle-nanolayer, caused partial closure of nanotube interior and significantly reduced ZnO solubility and antibacterial efficacy. Co-deposition of Ag nanoparticles enhanced the antibacterial properties of synthesized coatings. However, the increase of ZnO quantity on Ag nanoparticles co-deposited surfaces favored the adhesion of bacterial cells. Thus, ZnO/Ag/TiO2 nanotube composite layers may be promising delivery systems for combating post-operative infections in hard tissue replacement procedures. However, the amount of loaded antibacterial agents must be carefully balanced to avoid the overdose and reduced efficacy.

Preparation and in vitro cell-biological performance of sodium alginate/nano-zinc silicate co-modified calcium silicate bioceramics

We have prepared a (Zn, Na)-containing layer on the surface of calcium silicate bioceramics, which are spin-coated with sodium alginate and nano-zinc silicate.

Bioresorbable zinc hydroxyapatite guided bone regeneration membrane for bone regeneration

OBJECTIVES

The aim of this study was to investigate the bone regenerative properties of a heat treated cross-linked GBR membrane with zinc hydroxyapatite powders in the rat calvarial defect model over a 6-week period.

MATERIAL AND METHODS

In vitro physio-chemical characterization involved X-ray diffraction analysis, surface topology by scanning electron microscopy, and zinc release studies in physiological buffers. Bilateral rat calvarial defects were used to compare the Zn-HAp membranes against the commercially available collagen membranes and the unfilled defect group through radiological and histological evaluation.

RESULTS

The synthesized Zn-MEM (100 μm thick) showed no zinc ions released in the phosphate buffer solution (PBS) buffer, but zinc was observed under acidic conditions. At 6 weeks, both the micro-CT and histological analyses revealed that the Zn-MEM group yielded significantly greater bone formation with 80 ± 2% of bone filled, as compared with 60 ± 5% in the collagen membrane and 40 ± 2% in the unfilled control group.

CONCLUSION

This study demonstrated the use of heat treatment as an alternative method to cross-linking the Zn-MEM to be applied as a GBR membrane. Its synthesis and production are relatively simple to fabricate, and the membrane had rough surface features on one side, which might be beneficial for cellular activities. In a rat calvarial defect model, it was shown that new bone formation was accelerated in comparison with the collagen membrane and the unfilled defect groups. These results would suggest that Zn-MEM has the potential for further development in dental applications.

The zinc sensing receptor, ZnR/GPR39, controls proliferation and differentiation of colonocytes and thereby tight junction formation in the colon

The intestinal epithelium is a renewable tissue that requires precise balance between proliferation and differentiation, an essential process for the formation of a tightly sealed barrier. Zinc deficiency impairs the integrity of the intestinal epithelial barrier and is associated with ulcerative and diarrheal pathologies, but the mechanisms underlying the role of Zn²⁺ are not well understood. Here, we determined a role of the colonocytic Zn²⁺ sensing receptor, ZnR/GPR39, in mediating Zn²⁺-dependent signaling and regulating the proliferation and differentiation of colonocytes. Silencing of ZnR/GPR39 expression attenuated Zn²⁺-dependent activation of ERK1/2 and AKT as well as downstream activation of mTOR/p70S6K, pathways that are linked with proliferation. Consistently, ZnR/GPR39 silencing inhibited HT29 and Caco-2 colonocyte proliferation, while not inducing caspase-3 cleavage. Remarkably, in differentiating HT29 colonocytes, silencing of ZnR/GPR39 expression inhibited alkaline phosphatase activity, a marker of differentiation. Furthermore, Caco-2 colonocytes showed elevated expression of ZnR/GPR39 during differentiation, whereas silencing of ZnR/GPR39 decreased monolayer transepithelial electrical resistance, suggesting compromised barrier formation. Indeed, silencing of ZnR/GPR39 or chelation of Zn²⁺ by the cell impermeable chelator CaEDTA was followed by impaired expression of the junctional proteins, that is, occludin, zonula-1 (ZO-1) and E-cadherin. Importantly, colon tissues of GPR39 knockout mice also showed a decrease in expression levels of ZO-1 and occludin compared with wildtype mice. Altogether, our results indicate that ZnR/GPR39 has a dual role in promoting proliferation of colonocytes and in controlling their differentiation. The latter is followed by ZnR/GPR39-dependent expression of tight junctional proteins, thereby leading to formation of a sealed intestinal epithelial barrier. Thus, ZnR/GPR39 may be a therapeutic target for promoting epithelial function and tight junction barrier integrity during ulcerative colon diseases.

In vitro antibacterial capacity and cytocompatibility of SiO2-CaO-P2O5 meso-macroporous glass scaffolds enriched with ZnO

Zn²⁺ ions exhibit osteogenic, angiogenic and antimicrobial properties. For this reason, they are often added in small amounts to bioceramics being investigated for bone tissue engineering. In this paper, the cytocompatibility and antibacterial properties of 80% SiO₂-15% CaO-5% P₂O₅ (mol%) mesoporous bioactive glass (MBG) scaffolds substituted with 4.0% and 7.0% of ZnO were studied and compared with the Zn-free scaffold. Cell proliferation, morphology, differentiation and cytotoxic effects of Zn²⁺ ions released from the samples were examined by culturing human osteoblast-like cells (HOS) osteoblasts both in the presence of sample extracts and on the scaffold surface. The bacterial inhibition capacity of the scaffolds was explored by using Gram-positive Stapylococcus aureus bacteria, responsible for numerous infections in orthopedic surgery, to simulate a severe infection. Our results show that the Zn-MBG scaffolds possess a hierarchical meso-macropore structure suitable for osteoblast growth. Furthermore, the amount of Zn²⁺ released from the scaffold with 4.0% ZnO was found to be more favorable for HOS cell development than that released from the scaffold including 7.0% ZnO. Zn²⁺ released to the medium from both scaffolds exhibited antibacterial properties against S. aureus. Thus, the cytocompatibility and the antibacterial ability exhibited by the MBG scaffold containing 4.0% ZnO make it a suitable candidate for bone regeneration applications.

The effect of adjuvant zinc therapy on recovery from pneumonia in hospitalized children: a double-blind randomized controlled trial

Objectives. Pneumonia is one of the common mortality causes in young children. Some studies have shown beneficial effect of zinc supplements on treatment of pneumonia. The present study aimed to investigate the effects of short courses of zinc administration on recovery from this disease in hospitalized children. Methods. In a parallel Double-Blind Randomized Controlled Trial at Ayatollah Golpaygani Hospital in Qom, 120 children aged 3-60 months with pneumonia were randomly assigned 1 : 1 to receive zinc or placebo (5 mL every 12 hours) along with the common antibiotic treatments until discharge. Primary outcome was recovery from pneumonia which included the incidence and resolving clinical symptoms and duration of hospitalization. Results. The difference between two groups in all clinical symptoms at admittance and the variables affecting the disease such as age and sex were not statistically significant (P < 0.05) at baseline. Compared to the placebo group, the treatment group showed a statistically significant decrease in duration of clinical symptoms (P = 0.044) and hospitalization (P = 0.004). Conclusions. Supplemental administration of zinc can expedite the healing process and results in faster resolution of clinical symptoms in children with pneumonia. In general, zinc administration, along with common antibiotic treatments, is recommended in this group of children. It can also reduce the drug resistance caused by multiple antibiotic therapies. This trial is approved by Medical Ethic Committee of Islamic Azad University in Iran (ID Number: 8579622-Q). This study is also registered in AEARCTR (The American Economic Association's Registry for Randomized Controlled Trials). This trial is registered with RCT ID: AEARCTR-0000187.

The Effect of Exogenous Zinc Concentration on the Responsiveness of MC3T3-E1 Pre-Osteoblasts to Surface Microtopography: Part II (Differentiation)

Osseointegration of bone implants is a vital part of the recovery process. Numerous studies have shown that micropatterned geometries can promote cell-substrate associations and strengthen the bond between tissue and the implanted material. As demonstrated previously, exogenous zinc levels can influence the responsiveness of pre-osteoblasts to micropatterns and modify their migratory behavior. In this study, we sought to determine the effect of exogenous zinc on differentiation of osteoblasts cultured on micropatterned vs. planar substrates. Levels of activated metalloproteinase-2 (MMP-2) and transforming growth factor-beta 1 (TGF-β1), as well as early stage differentiation marker alkaline phosphatase, were altered with the addition of zinc. These results suggest that exogenous zinc concentration and micropatterning may interdependently modulate osteoblast differentiation.

Effects of zinc-substituted nano-hydroxyapatite coatings on bone integration with implant surfaces

OBJECTIVE

The purpose of this study was to investigate the effects of a zinc-substituted nano-hydroxyapatite (Zn-HA) coating, applied by an electrochemical process, on implant osseointegraton in a rabbit model.

METHODS

A Zn-HA coating or an HA coating was deposited using an electrochemical process. Surface morphology was examined using field-emission scanning electron microscopy. The crystal structure and chemical composition of the coatings were examined using an X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). A total of 78 implants were inserted into femurs and tibias of rabbits. After two, four, and eight weeks, femurs and tibias were retrieved and prepared for histomorphometric evaluation and removal torque (RTQ) tests.

RESULTS

Rod-like HA crystals appeared on both implant surfaces. The dimensions of the Zn-HA crystals seemed to be smaller than those of HA. XRD patterns showed that the peaks of both coatings matched well with standard HA patterns. FTIR spectra showed that both coatings consisted of HA crystals. The Zn-HA coating significantly improved the bone area within all threads after four and eight weeks (P<0.05), the bone to implant contact (BIC) at four weeks (P<0.05), and RTQ values after four and eight weeks (P<0.05).

CONCLUSIONS

The study showed that an electrochemically deposited Zn-HA coating has potential for improving bone integration with an implant surface.

Bone regeneration of rat tibial defect by zinc-tricalcium phosphate (Zn-TCP) synthesized from porous Foraminifera carbonate macrospheres

Foraminifera carbonate exoskeleton was hydrothermally converted to biocompatible and biodegradable zinc-tricalcium phosphate (Zn-TCP) as an alternative biomimetic material for bone fracture repair. Zn-TCP samples implanted in a rat tibial defect model for eight weeks were compared with unfilled defect and beta-tricalcium phosphate showing accelerated bone regeneration compared with the control groups, with statistically significant bone mineral density and bone mineral content growth. CT images of the defect showed restoration of cancellous bone in Zn-TCP and only minimal growth in control group. Histological slices reveal bone in-growth within the pores and porous chamber of the material detailing good bone-material integration with the presence of blood vessels. These results exhibit the future potential of biomimetic Zn-TCP as bone grafts for bone fracture repair.

The Effect of Exogenous Zinc Concentration on the Responsiveness of MC3T3-E1 Pre-Osteoblasts to Surface Microtopography: Part I (Migration)

Initial cell-surface interactions are guided by the material properties of substrate topography. To examine if these interactions are also modulated by the presence of zinc, we seeded murine pre-osteoblasts (MC3T3-E1, subclone 4) on micropatterned polydimethylsiloxane (PDMS) containing wide (20 µm width, 30 µm pitch, 2 µm height) or narrow (2 µm width, 10 µm pitch, 2 µm height) ridges, with flat PDMS and tissue culture polystyrene (TC) as controls. Zinc concentration was adjusted to mimic deficient (0.23 µM), serum-level (3.6 µM), and zinc-rich (50 µM) conditions. Significant differences were observed in regard to cell morphology, motility, and contact guidance. We found that cells exhibited distinct anisotropic migration on the wide PDMS patterns under either zinc-deprived (0.23 µM) or serum-level zinc conditions (3.6 µM). However, this effect was absent in a zinc-rich environment (50 µM). These results suggest that the contact guidance of pre-osteoblasts may be partly influenced by trace metals in the microenvironment of the extracellular matrix.

Effect of zinc oxide nanoparticles on the function of MC3T3-E1 osteoblastic cells

Zinc oxide nanoparticles (ZnO NPs) can be ingested directly when used in food, food packaging, drug delivery, and cosmetics. This study evaluated the cellular effects of ZnO NPs (50 and 100 nm diameter particle sizes) on the function of osteoblastic MC3T3-E1 cells. ZnO NPs showed cytotoxicity at concentrations of above 50 μg/ml, and there was no significant effect of the size on the cytotoxicity of ZnO NPs. Within the testing concentrations of 0.01~1 μg/ml, which did not cause a marked drop in cell viability, ZnO NPs (0.1 μg/ml) caused a significant elevation of alkaline phosphatase activity, collagen synthesis, mineralization, and osteocalcin content in the cells (P < 0.05). Moreover, pretreatment with ZnO NPs (0.01~1 μg/ml) significantly reduced antimycin A-induced cell damage by preventing mitochondrial membrane potential dissipation, complex IV inactivation, and ATP loss. Measurement of reactive oxygen species (ROS) indicated decrease in ROS level upon exposure to ZnO nanoparticles (0.01 μg/ml). Hence, our study indicated that ZnO nanoparticles can have protective effects on osteoblasts at low concentrations where there are little or no observable cytotoxic effects.

Bone formation controlled by biologically relevant inorganic ions: role and controlled delivery from phosphate-based glasses

The role of metal ions in the body and particularly in the formation, regulation and maintenance of bone is only just starting to be unravelled. The role of some ions, such as zinc, is more clearly understood due to its central importance in proteins. However, a whole spectrum of other ions is known to affect bone formation but the exact mechanism is unclear as the effects can be complex, multifactorial and also subtle. Furthermore, a significant number of studies utilise single doses in cell culture medium, whereas the continual, sustained release of an ion may initiate and mediate a completely different response. We have reviewed the role of the most significant ions that are known to play a role in bone formation, namely calcium, zinc, strontium, magnesium, boron, titanium and also phosphate anions as well as copper and its role in angiogenesis, an important process interlinked with osteogenesis. This review will also examine how delivery systems may offer an alternative way of providing sustained release of these ions which may effect and potentiate a more appropriate and rapid tissue response.

Vitamin C and zinc intakes are related to bone macroarchitectural structure and strength in prepubescent girls

The extent to which nutrient intake may influence bone structure and strength during maximal rates of skeletal growth remains uncertain. We examined the relationship of dietary intake of micronutrients and bone macroarchitectural structure in young girls. This cross-sectional analysis included baseline data from 363 fourth- and sixth-grade girls enrolled in the Jump-In study. Nutrient intake was assessed using the Harvard Youth/Adolescent Food Frequency Questionnaire. Volumetric BMD (vBMD), bone geometry, and strength were measured by peripheral quantitative computed tomography. Correlations and regression modeling assessed relations between usual nutrient intake and bone parameters. In fourth-grade girls, metaphyseal and diaphyseal area and circumferences as well as diaphyseal strength were associated with vitamin C intake (r = 0.15-0.19, p < 0.05). Zinc intake was correlated with diaphyseal vBMD (r = 0.15-0.16, p < 0.05). Using multiple linear regression to adjust for important covariates, we observed significant independent associations for vitamin C and zinc with bone parameters. For every milligram per day of vitamin C intake trabecular area increased by 11 %, cortical strength improved by 14 %, and periosteal and endosteal circumferences increased by 5 and 8.6 %, respectively. For every milligram per day of zinc intake, cortical vBMD increased by <1 %. No significant associations were observed in sixth-grade girls. Results of this study suggests that vitamin C and zinc intake are positively associated with objective measures of bone geometry, size, and strength in fourth-grade girls. This indicates that potential differences in micronutrient and bone associations at various age-associated stages of bone maturation may be indicative of competing hormonal influences.

Biological responses of human bone marrow mesenchymal stem cells to Sr-M-Si (M = Zn, Mg) silicate bioceramics

Strontium (Sr), Zinc (Zn), magnesium (Mg), and silicon (Si) are reported to be essential trace elements for the growth and mineralization of bone. We speculated that the combination of these bioactive elements in bioceramics may be effective to regulate the osteogenic property of bone-forming cells. In this study, two Sr-containing silicate bioceramics, Sr(2)ZnSi(2)O(7) (SZS) and Sr(2)MgSi(2)O(7) (SMS), were prepared. The biological response of human bone marrow mesenchymal stem cells (BMSCs) to the two bioceramics (in the forms of powders and dense ceramic bulks) was systematically studied. In powder form, the effect of powder extracts on the viability and alkaline phosphatase (ALP) activity of BMSCs was investigated. In ceramic disc form, both direct and indirect coculture of BMSCs with ceramic discs were used to investigate their biological response, including attachment, proliferation, ALP activity, and bone-related genes expression. Beta-tricalcium phosphate (β-TCP) and akermanite (Ca(2)MgSi(2)O(7), CMS) were used as control materials. The results showed that the Sr, Zn, and Si (or Sr, Mg, and Si)-containing ionic products from SZS and SMS powders enhanced ALP activity of BMSCs, compared to those from β-TCP. Both SZS and SMS ceramic discs supported the growth of BMSCs, and most importantly, significantly enhanced the ALP activity and bone-related genes expression of BMSCs as compared to β-TCP. The results suggest that the specific combination of bioactive ions (Sr, Zn, Si, e.g.) in bioceramics is a viable way to improve the biological performance of biomaterials, and the form of materials and surface properties were nonnegligible factors to influence cell response.

Zinc upregulates the expression of osteoprotegerin in mouse osteoblasts MC3T3-E1 through PKC/MAPK pathways

Zinc is an essential element for bone formation; however, its role in osteoblast has not been well understood. In the present study, we hypothesized that zinc could increase osteogenetic function by stimulating osteoblast proliferation and osteoprotegerin (OPG) activity. To test this hypothesis, osteoblastic MC3T3-E1 cells were cultured and treated with various concentrations of zinc (0, 10, 30, 50, 70, 110, 130, and 150 μM) for 24 and 48 h. 3-[4,5-dimethylthiazol-2-y]-2,5-diphenyltetrazolium bromide assay showed that cell proliferation was significantly stimulated with 50 μM zinc treatment. Furthermore, under the same treatment condition, OPG expression was significantly increased as evidenced by the results of RT-PCR and ELISA. However, the zinc-induced OPG expression was significantly attenuated when MC3T3-E1 cells were co-treated with either protein kinase C (PKC) inhibitor, GF109203X, or the Inhibitor of mitogen-activated extracellular signal-regulated kinase 1 (MEK1), PD98059. Moreover, OPG expression was further increased when MC3T3-E1 cells were treated with PMA (the activator of protein of kinase C) in the presence of zinc. These results suggested that zinc would increase osteogenic function by stimulating PKC and MAPK signaling pathways.