Effects of Salivary Mg on Head and Neck Carcinoma via TRPM7.

Magnesium (Mg) has been known to play vital roles in regulating growth and various metabolic processes. In recent years, the association between Mg and tumorigenesis has raised more and more attention. However, the effects of Mg on the progression of head and neck carcinoma (HNC), as well as the mechanism behind it, remain undefined. In this study, the roles of Mg in tumorigenic activities were tested in CAL27 and FaDu cells as well as in a xenograft tumor model in nude mice. We demonstrated that a moderate increase in extracellular Mg contributed to the proliferation, migration, and invasion of 2 HNC cell lines, while the addition of Mg in drinking water promoted the growth of xenograft tumors in mice without altering their serum Mg levels. Moreover, TRPM7, a major Mg transporter, was shown to be essential for the tumorigenic activities of HNC and the Mg-induced promotive effects on HNC cells and was further shown to be associated with the activation of AKT/mTOR (mammalian target of rapamycin) signaling. In a preliminary clinical study, we determined the Mg ion concentrations in the stimulated saliva from 72 patients with nasopharynx carcinoma and 12 healthy individuals. Our data revealed that the salivary Mg levels of subjects with nasopharynx carcinoma were significantly higher than those of the healthy controls. This is correlated with our finding showing TRPM7 to be overexpressed in tumor tissues harvested from 9 patients with HNC. Therefore, we can conclude that salivary Mg level, within a certain range, could act as a risk factor for the progression of HNC, which involves the activation of AKT/mTOR signaling pathways through the TRPM7 channel. The control of salivary Mg level and the intervention of TRPM7 should not be ignored during the study of HNC.

Construction of poly(lactic-co-glycolic acid)/ZnO nanorods/Ag nanoparticles hybrid coating on Ti implants for enhanced antibacterial activity and biocompatibility.

Poly(lactic-co-glycolic acid)/Ag/ZnO nanorods coating were successfully prepared on the surface of Ti metallic implants using a hydrothermal method and subsequent spin-coating of mixtures of poly(lactic-co-glycolic acid) and silver nanoparticles. The poly(lactic-co-glycolic acid)/Ag/ZnO nanorods coating exhibited excellent antibacterial efficacy of over 96% against both Staphylococcus aureus and Escherichia coli when the initial content of Ag nanoparticles was over 3wt%. In addition, the release of both silver and zinc could last for over a hundred days due to the enwrapping of poly(lactic-co-glycolic acid). Proliferation of mouse calvarial cells exhibited minimal cytotoxicity on the poly(lactic-co-glycolic acid)/Ag/ZnO coating with an initial content of Ag nanoparticles of 1wt% and 3wt%, while it inhibited cell proliferation once this value was increased to 6wt%. The results revealed that this poly(lactic-co-glycolic acid)/Ag/ZnO composite could provide a long-lasting antibacterial approach and good cytocompatibility, thus exhibiting considerable potential for biomedical application in orthopedic and dental implants with excellent self-antibacterial activity and good biocompatibility.

The controlled drug release by pH-sensitive molecularly imprinted nanospheres for enhanced antibacterial activity.

In this study, we prepared pH-sensitive hybrid nanospheres through the implementation of a facile molecularly imprinted polymer (MIP) technique combined with a UV-initiated precipitation polymerization method using vancomycin (VA) for the templates. During the course of this investigation, both 2-hydroxyethyl methacrylate (HEMA) and 2-(diethylamino) ethyl methacrylate (DEAEMA) were utilized as the functional monomers, while ethylene glycol dimethacrylate (EGDMA) was used as a cross-linker. The obtained MIP nanospheres exhibited well-controlled particle size, with a drug loading capacity of about 17%, much higher than that of the non-imprinted polymer (NIP) nanospheres (5%). In addition, the VA loading quantity was closely correlated with the dosage of the cross-linking agent, and the MIP nanospheres exhibited a slower and more controlled VA release rate than the NIP nanospheres. Moreover, these MIP nanospheres were sensitive to pH values, and consequently showed an increasing release rate of VA as the pH level was decreased. The VA-loaded MIP nanospheres showed the higher antibacterial ratio of over 92% against Staphylococcus aureus (S. aureus) while the NIP nanospheres were friendly to S. aureus. These MIP nanospheres can be promising for targeting drug delivery system to achieve specific therapies such as preventing bacterial infections and killing cancer cells without damaging health cells and tissues.

Construction of N-halamine labeled silica/zinc oxide hybrid nanoparticles for enhancing antibacterial ability of Ti implants.

The traditional antibiotic treatment for bacterial infections often induces antibiotic resistance in bacteria. In this work, we developed hybrid nanoparticles (NPs) with a self-antibacterial ability on Ti implants using monodispersed polystyrene-acrylic acid (PSA) nanoparticles as colloidal templates followed by the electrostatic adsorption of zinc oxide (ZnO) and the subsequent deposition of silica (SiO2) membrane on the outside. These synthesized PSA-ZnO-SiO2 NPs were pretreated by 5,5-dimethylhydantoin (DMH) before chlorination in a diluted NaClO solution. These nanoparticles (PSA-ZnO-SiO2-DMH) were subsequently labeled by N-halamines and then immobilized on the surface of titanium plates through hydrogen bonding. Field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the modified surface. Antibacterial tests disclosed that the PSA-ZnO-SiO2-DMH-Cl NPs modified surface exhibited excellent antibacterial activity against both Pseudomonas aeruginosa (P.au), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In vitro cell culture results revealed that PSA-ZnO-SiO2-DMH-Cl had no obvious cytotoxicity for an MC3T3-E1 preosteoblast. This novel surface system provides a promising self-antibacterial bioplatform for metallic implants without using antibiotics.

Metal Ion Coordination Polymer-Capped pH-Triggered Drug Release System on Titania Nanotubes for Enhancing Self-antibacterial Capability of Ti Implants.

The current work reports a novel hybrid system with a highly efficient, bioresponsive, and controlled release of antibacterial activity via the metal ion coordination polymer on titania nanotubes (TNTs). These hybrid systems exhibited a self-defense behavior that is triggered by the change of the ambient environment acidity due to bacterial infection with Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli). The antibacterial agents, including antibiotics and nanosilver particles, can be loaded into TNTs and then sealed with coordination polymers (CPs) through the attachment of metallic ions such as Zn2+ or Ag+. The zinc and silver ions work as intermediate coordination bonds, and they are sensitive to the change in H+. Because of the strong bonding of CPs, the amount of released antimicrobial agents is maintained at a nonsignificant level when pH is maintained at 7.4. However, the coordination bond of the capped CPs was triggered to open and release antibacterial agents from TNTs once the environment becomes acidic. The release rate gradually increased as the pH value further decreased. Subsequently, the antibacterial efficiency of the hybrid system is accelerated as the local microenvironment becomes more acidic during bacterial infection. In addition, the metal ions that are used for intermediate bond bridging are also favorable for specific biological functions. For example, Zn2+ can promote the proliferation of osteoblastic cells, while Ag+ can further enhance the antibacterial capability. In conclusion, this smart surface coating system not only demonstrates excellent self-antibacterial properties and biocompatibility but also formulates a controllable delivery system for the long-lasting treatment of biomaterial-related bacterial infections.

Construction of poly (vinyl alcohol)/poly (lactide-glycolide acid)/vancomycin nanoparticles on titanium for enhancing the surface self-antibacterial activity and cytocompatibility.

Comparing with traditional drug dosage form, controlled release systems offer more effective and favorable route to deliver drugs in optimum dose to specific sites with long term release duration. In this work, an effective drug delivery system composed of poly (vinyl alcohol) (PVA)/poly (lactide-glycolide acid) (PLGA) nanoparticles (NPs) with encapsulated vancomycin (Van), is constructed on the surface of biomedical titanium. The PVA/PLGA/Van NPs synthesized via double emulsion route are grafted onto the surface of titanium plates modified by alkaline-heat treatment and subsequent aminopropyltriethoxysilane (APTES) deposition. In vitro tests disclose that NPs can release a small amount of drugs continuously due to the slow swelling or hydrolysis of polymer chain segments as the immersion time increases. As the pH value reduces, the ester bonds rupture with releasing more drugs, which is why this drug delivery system exhibits the highest antibacterial efficiency at the lowest pH value of 4.5 in this work. Cell culture results reveal that this smart surface system on titanium facilitates the cell attachment and proliferation on implants. Hence, this pH controlled drug delivery system can be successfully applied as a bio-platform for improving both the osteoblasts adhesion and antibacterial activity of metallic implants.

Dopamine Modified Organic-Inorganic Hybrid Coating for Antimicrobial and Osteogenesis.

A hybrid coating composed of hydroxyapatite (HA), Ag nanoparticles (NPs), and chitosan (CS) was successfully prepared on a Ti substrate by a layer-by-layer assembly process. A polydopamine-assisted (PDA-assisted) coating showed a good bond with HA. Ag NPs were uniformly distributed into the hybrid coating through a solution method and ultraviolet light reduction. A CS nanofilm was deposited via spin-coating to control the release of Ag+ from the hybrid coating. The results disclosed that the 3-layer CS coating could efficiently control the release of Ag+ from the hybrid coating via the Fickian diffusion mechanism and that the PDA/HA/Ag/CS-1 coating exhibited antibacterial ratios of 63.0% and 51.8% against E. coli and S. aureus, respectively. Furthermore, the normal structure of E. coli was obviously destroyed by two types of Ag doped coatings. The cell viability assay showed that CS effectively reduced the cytotoxicity of the hybrid coating after a 7 day incubation. The hybrid coating presented high ALP activities at days 3 and 14. The results reveal that hybrid coatings can endow Ti implants with good antibacterial capability as well as cell viability and osteogenic activity.

Design of magnesium alloys with controllable degradation for biomedical implants: From bulk to surface.

The combination of high strength, light weight, and natural biodegradability renders magnesium (Mg)-based alloys promising in orthopedic implants and cardiovascular stents. Being metallic materials, Mg and Mg alloys made for scaffolds provide the necessary mechanical support for tissue healing and cell growth in the early stage, while natural degradation and reabsorption by surrounding tissues in the later stage make an unnecessarily follow-up removal surgery. However, uncontrolled degradation may collapse the scaffolds resulting in premature implant failure, and there has been much research in controlling the degradation rates of Mg alloys. This paper reviews recent progress in the design of novel Mg alloys, surface modification and corrosion mechanisms under different conditions, and describes the effects of the structure, composition, and surface conditions on the degradation behavior in vitro and in vivo. STATEMENT OF SIGNIFICANCE: Owing to their unique mechanical properties, biodegradability, biocompatibility, Mg based biomaterials are becoming the most promising substitutes for tissue regeneration for impaired bone, vascular and other tissues because these scaffolds can provide not only ideal space for the growth and differentiation of seeded cells but also enough strength before the formation of normal tissues. The most important is that these scaffolds can be fully degraded after tissue regeneration, which can satisfy the increasing demand for better biomedical devices and functional tissue engineering biomaterials in the world. However, the rapid degradation rate of these scaffolds restricts the wide application in clinic. This paper reviews recent progress on how to control the degrdation rate based on the relevant corrosion mechanisms through the design of porous structure, phase structure, grains, and amorphous structure as well as surface modification, which will be beneficial to the better understanding and functional design of Mg-based scaffolds for wide clinical applications in tissue reconstruction in near futures.

Antibacterial Activity of Silver Doped Titanate Nanowires on Ti Implants.

A nanostructured film composed of one-dimensional titanate nanowires (TNWs) was employed as a carrier of Ag nanoparticles and chitosan (CS) to improve the surface antibacterial activity and biocompatibility of titanium implants. A TNWs film was produced on a Ti substrate by an alkali hydrothermal reaction and subsequently doped by Ag nanoparticles through an ultraviolet light chemical reduction. The CS nanofilm was deposited on the Ag nanoparticles through a spin-assisted layer by layer assembly method. The results disclosed that Ag nanoparticles were successfully carried by TNWs and homogeneously distributed on the entire surface. Moreover, a CS nanofilm was also successfully deposited on the Ag nanoparticles. Antibacterial tests showed that the samples modified with a higher initial concentration of AgNO3 solution exhibited better antibacterial activity, and that a CS nanofilm could further improve the antibacterial activity of the TNWs. Cell viability and ALP tests revealed that the release of Ag(+) was detrimental for the growth, proliferation, and differentiation of MC3T3, and that CS could lower the negative effects of Ag gradually as the incubation time increased.

The modulation of stem cell behaviors by functionalized nanoceramic coatings on Ti-based implants.

Nanoceramic coating on the surface of Ti-based metallic implants is a clinical potential option in orthopedic surgery. Stem cells have been found to have osteogenic capabilities. It is necessary to study the influences of functionalized nanoceramic coatings on the differentiation and proliferation of stem cells in vitro or in vivo. In this paper, we summarized the recent advance on the modulation of stem cells behaviors through controlling the properties of nanoceramic coatings, including surface chemistry, surface roughness and microporosity. In addition, mechanotransduction pathways have also been discussed to reveal the interaction mechanisms between the stem cells and ceramic coatings on Ti-based metals. In the final part, the osteoinduction and osteoconduction of ceramic coating have been also presented when it was used as carrier of BMPs in new bone formation.

Polymeric nanoarchitectures on Ti-based implants for antibacterial applications.

Because of the excellent mechanical properties and good biocompatibility, titanium-based metals are widely used in hard tissue repair, especially load-bearing orthopedic applications. However, bacterial infection and complication during and after surgery often causes failure of the metallic implants. To endow titanium-based implants with antibacterial properties, surface modification is one of the effective strategies. Possessing the unique organic structure composed of molecular and functional groups resembling those of natural organisms, functionalized polymeric nanoarchitectures enhance not only the antibacterial performance but also other biological functions that are difficult to accomplish on many conventional bioinert metallic implants. In this review, recent advance in functionalized polymeric nanoarchitectures and the associated antimicrobial mechanisms are reviewed.

A diamond nanocone array for improved osteoblastic differentiation.

Efficient delivery of biomolecules to cells is of great importance in biology and medicine. To achieve this, we designed a novel type of densely packed diamond nanocone array to conveniently transport molecules to the cytoplasm of a great number of cells. The nanocone array was fabricated by depositing a thin layer of diamond film on a silicon substrate followed by bias-assisted reactive ion etching. The height of the diamond nanocones varied from 200 nm to 1 µm with tip radii of approximately 10 nm. Our fluorescein and propidium iodide staining results clearly demonstrated that dramatically enhanced delivery of fluorescein into cells was realized without leading to noticeable cell death with the aid of nanocone treatment. As a test case of the drug delivery application of the device, MC-3T3 cells in differentiation medium were applied to the nanocone array for enhanced intracellular delivery of the medium. This was confirmed by the fact that nanocone treated cells experienced much higher differentiation ability at an early stage in comparison with untreated cells. Overall, the results indicate that the diamond nanocone array provides a very simple but yet very effective approach to achieve delivery of molecules to a large number of cells.

Fabrication of micropillar substrates using replicas of alpha-particle irradiated and chemically etched PADC films.

We proposed a simple method to fabricate micropillar substrates. Polyallyldiglycol carbonate (PADC) films were irradiated by alpha particles and then chemically etched to form a cast with micron-scale spherical pores. A polydimethylsiloxane (PDMS) replica of this PADC film gave a micropillar substrate with micron-scale spherical pillars. HeLa cells cultured on such a micropillar substrate had significantly larger percentage of cells entering S-phase, attached cell numbers and cell spreading areas.

Hydrogen release from titanium hydride in foaming of orthopedic NiTi scaffolds.

Titanium hydride powders are utilized to enhance the foaming process in the formation of orthopedic NiTi scaffolds during capsule-free hot isostatic pressing. In order to study the formation mechanism, the thermal behavior of titanium hydride and hydrogen release during the heating process are systematically investigated in air and argon and under vacuum by X-ray diffraction (XRD), thermal analysis, including thermogravimetric analysis and differential scanning calorimetry, energy dispersive X-ray spectroscopy, and transmission electron microscopy. Our experiments reveal that hydrogen is continuously released from titanium hydride as the temperature is gradually increased from 300 to 700 °C. Hydrogen is released in two transitions: TiH1.924→TiH1.5/TiH1.7 between 300 °C and 400 °C and TiH1.5/TiH1.7→α-Ti between 400 °C and 600 °C. In the lower temperature range between 300 °C and 550 °C the rate of hydrogen release is slow, but the decomposition rate increases sharply above 550 °C. The XRD patterns obtained in air and under vacuum indicate that the surface oxide layer can deter hydrogen release. The pressure change is monitored in real time and the amount of hydrogen released is affected by the processing temperature and holding time. Holding processes at 425 °C, 480 °C, 500 °C, 550 °C, and 600 °C are found to significantly improve the porous structure in the NiTi scaffolds due to the stepwise release of hydrogen. NiTi scaffolds foamed by stepwise release of hydrogen are conducive to the attachment and proliferation of osteoblasts and the resulting pore size also favor in-growth of cells.

Biochemical characterization of the cell-biomaterial interface by quantitative proteomics.

Surface topography and texture of cell culture substrata can affect the differentiation and growth of adherent cells. The biochemical basis of the transduction of the physical and mechanical signals to cellular responses is not well understood. The lack of a systematic characterization of cell-biomaterial interaction is the major bottleneck. This study demonstrated the use of a novel subcellular fractionation method combined with quantitative MS-based proteomics to enable the robust and high-throughput analysis of proteins at the adherence interface of Madin-Darby canine kidney cells. This method revealed the enrichment of extracellular matrix proteins and membrane and stress fibers proteins at the adherence surface, whereas it shows depletion of extracellular matrix belonging to the cytoplasmic, nucleus, and lateral and apical membranes. The asymmetric distribution of proteins between apical and adherence sides was also profiled. Apart from classical proteins with clear involvement in cell-material interactions, proteins previously not known to be involved in cell attachment were also discovered.

Nano-scale surface morphology, wettability and osteoblast adhesion on nitrogen plasma-implanted NiTi shape memory alloy.

Plasma immersion ion implantation (PIII) is an effective method to increase the corrosion resistance and inhibit nickel release from orthopedic NiTi shape memory alloy. Nitrogen was plasma-implanted into NiTi using different pulsing frequencies to investigate the effects on the nano-scale surface morphology, structure, wettability, as well as biocompatibility. X-ray photoelectron spectroscopy (XPS) results show that the implantation depth of nitrogen increases with higher pulsing frequencies. Atomic force microscopy (AFM) discloses that the nano-scale surface roughness increases and surface features are changed from islands to spiky cones with higher pulsing frequencies. This variation in the nano surface structures leads to different surface free energy (SFE) monitored by contact angle measurements. The adhesion, spreading, and proliferation of osteoblasts on the implanted NiTi surface are assessed by cell culture tests. Our results indicate that the nano-scale surface morphology that is altered by the implantation frequencies impacts the surface free energy and wettability of the NiTi surfaces, and in turn affects the osteoblast adhesion behavior.

Microstructure, nickel suppression and mechanical characteristics of electropolished and photoelectrocatalytically oxidized biomedical nickel titanium shape memory alloy.

A new surface modification protocol encompassing an electropolishing pretreatment (EP) and subsequent photoelectrocatalytic oxidation (PEO) has been developed to improve the surface properties of biomedical nickel titanium (NiTi) shape memory alloy (SMA). Electropolishing is a good way to improve the resistance to localized breakdown of NiTi SMA whereas PEO offers the synergistic effects of advanced oxidation and electrochemical oxidation. Our results indicate that PEO leads to the formation of a sturdy titania film on the EP NiTi substrate. There is an Ni-free zone near the top surface and a graded interface between the titania layer and NiTi substrate, which bodes well for both biocompatibility and mechanical stability. In addition, Ni ion release from the NiTi substrate is suppressed, as confirmed by the 10-week immersion test. The modulus and hardness of the modified NiTi surface increase with larger indentation depths, finally reaching plateau values of about 69 and 3.1GPa, respectively, which are slightly higher than those of the NiTi substrate but much lower than those of a dense amorphous titania film. In comparison, after undergoing only EP, the mechanical properties of NiTi exhibit an inverse change with depth. The deformation mechanism is proposed and discussed. Our results indicate that surface modification by dual EP and PEO can notably suppress Ni ion release and improve the biocompatibility of NiTi SMA while the surface mechanical properties are not compromised, making the treated materials suitable for hard tissue replacements.

XPS and biocompatibility studies of titania film on anodized NiTi shape memory alloy.

A dense titania film is fabricated in situ on NiTi shape memory alloy (SMA) by anodic oxidation in a Na(2)SO(4) electrolyte. The microstructure of the titania film and its influence on the biocompatibility of NiTi SMA are investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), hemolysis analysis, and platelet adhesion test. The results indicate that the titania film has a Ni-free zone near the surface and can effectively block the release of harmful Ni ions from the NiTi substrate in simulated body fluids. Moreover, the wettability, hemolysis resistance, and thromboresistance of the NiTi sample are improved by this anodic oxidation method.

Microstructural characteristics and biocompatibility of a Type-B carbonated hydroxyapatite coating deposited on NiTi shape memory alloy.

Microstructural characteristics and biocompatibility of a Type-B carbonated hydroxyapatite (HA) coating prepared on NiTi SMA by biomimetic deposition were characterized using XRD, SEM, XPS, FTIR and in vitro studies including hemolysis test, MTT cytotoxicity test and fibroblasts cytocompatibility test. It is found CO(3)(2-) groups were present as substitution of PO(4)(3-) anions in HA crystal lattice due to Type-B carbonate. The growth of Type-B carbonated HA coating in SBF containing HCO(3)(-) ions is stable during all periods of biomimetic deposition. The carbonated HA coating has better blood compatibility than the chemically-polished NiTi SMA. There was a good cell adhesion to this HA coating surface and cell proliferation in the vicinity of the coating was better than that for the chemically-polished NiTi SMA. Thus biomimetic deposition of this carbonated HA coating is a promising way to improve the biocompatibility of NiTi SMA for implant applications.

A biomimetic hierarchical scaffold: natural growth of nanotitanates on three-dimensional microporous Ti-based metals.

Nanophase materials are promising alternative implant materials in tissue engineering. Here we report for the first time the large-scale direct growth of nanostructured bioactive titanates on three-dimensional (3D) microporous Ti-based metal (NiTi and Ti) scaffolds via a facile low temperature hydrothermal treatment. The nanostructured titanates show characteristics of 1D nanobelts/nanowires on a nanoskeleton layer. Besides resembling cancelous bone structure on the micro/macroscale, the 1D nanostructured titanate on the exposed surface is similar to the lowest level of hierarchical organization of collagen and hydroxyapatite. The resulting surface displays superhydrophilicity and favors deposition of hydroxyapatite and accelerates cell attachment and proliferation. The remarkable simplicity of this process makes it widely accessible as an enabling technique for applications from engineering materials treatment including energy-absorption materials and pollution-treatment materials to biotechnology.