3D Printed MXene Aerogels with Truly 3D Macrostructure and Highly Engineered Microstructure for Enhanced Electrical and Electrochemical Performance.

Assembling 2D materials such as MXenes into functional 3D aerogels using 3D printing technologies gains attention due to simplicity of fabrication, customized geometry and physical properties, and improved performance. Also, the establishment of straightforward electrode fabrication methods with the aim to hinder the restack and/or aggregation of electrode materials, which limits the performance of the electrode, is of great significant. In this study, unidirectional freeze casting and inkjet-based 3D printing are combined to fabricate macroscopic porous aerogels with vertically aligned Ti3 C2 Tx sheets. The fabrication method is developed to easily control the aerogel microstructure and alignment of the MXene sheets. The aerogels show excellent electromechanical performance so that they can withstand almost 50% compression before recovering to the original shape and maintain their electrical conductivities during continuous compression cycles. To enhance the electrochemical performance, an inkjet-printed MXene current collector layer is added with horizontally aligned MXene sheets. This combines the superior electrical conductivity of the current collector layer with the improved ionic diffusion provided by the porous electrode. The cells fabricated with horizontal MXene sheets alignment as current collector with subsequent vertical MXene sheets alignment layers show the best electrochemical performance with thickness-independent capacitive behavior.

3D Printing of Additive-Free 2D Ti3C2Tx (MXene) Ink for Fabrication of Micro-Supercapacitors with Ultra-High Energy Densities.

Recent advances in the development of self-powered devices and miniaturized electronics have increased the demand for on-chip energy storage devices that can deliver high power and energy densities in a limited footprint area. Here, we report the fabrication of all-solid-state micro-supercapacitors (MSCs) through a three-dimensional (3D) printing of additive-free and water-based MXene ink. The fabricated MSCs benefit from the high electrical conductivity and excellent electrochemical properties of two-dimensional (2D) Ti3C2Tx MXene and a 3D interdigital electrode architecture to deliver high areal and volumetric energy densities. We demonstrate that a highly concentrated MXene ink shows desirable viscoelastic properties for extrusion printing at room temperature and therefore can be used for scalable fabrication of MSCs with various architectures and electrode thicknesses on a variety of substrates. The developed printing process can be readily used for the fabrication of flexible MSCs on polymer and paper substrates. The printed solid-state devices show exceptional electrochemical performance with very high areal capacitance of up to ∼1035 mF cm-2. Our study introduces Ti3C2Tx MXene as an excellent choice of electrode material for the fabrication of 3D MSCs and demonstrates 3D printing of MXene inks at room temperature.

Controlling the Dimensions of 2D MXenes for Ultrahigh-Rate Pseudocapacitive Energy Storage.

The capacitive properties of two-dimensional (2D) transition metal carbides/nitrides (MXenes) have been the focus of much research in recent years. MXenes store charge by the pseudocapacitance mechanism (fast surface redox reactions) but can deliver their stored charge at much higher rates compared to other pseudocapacitive materials. Herein, the dependence of the electrochemical properties of MXenes on their lateral dimensions is reported. We show that synthesizing MXenes with controlled dimensions enables the design and fabrication of electrodes with high electronic and ionic conductivities. At low scan rates, electrodes fabricated using a mixture of small and large flakes could deliver very high specific gravimetric and volumetric capacitances of about 435 F g-1 and 1513 F cm-3, respectively. At a very high scan rate of 10 V s-1, the performance of the electrodes remained capacitive, demonstrating their ultrahigh-rate energy storage capability. This work outlines an effective method for the design and fabrication of MXene electrodes with high energy and power densities.

Calcium silicate-based cements and functional impacts of various constituents.

Calcium silicate-based cements have superior sealing ability, bioactivity, and marginal adaptation, which make them suitable for different dental treatment applications. However, they exhibit some drawbacks such as long setting time and poor handling characteristics. To overcome these limitations calcium silicates are engineered with various constituents to improve specific characteristics of the base material, and are the focus of this review. An electronic search of the PubMed, MEDLINE, and EMBASE via OVID databases using appropriate terms and keywords related to the use, application, and properties of calcium silicate-based cements was conducted. Two independent reviewers obtained and analyzed the full texts of the selected articles. Although the effects of various constituents and additives to the base Portland cement-like materials have been investigated, there is no one particular ingredient that stands out as being most important. Applying nanotechnology and new synthesis methods for powders most positively affected the cement properties.

Functional role of inorganic trace elements in angiogenesis part III: (Ti, Li, Ce, As, Hg, Va, Nb and Pb).

Many essential elements exist in nature with significant influence on human health. Angiogenesis is vital in developmental, repair, and regenerative processes, and its aberrant regulation contributes to pathogenesis of many diseases including cancer. Thus, it is of great importance to explore the role of these elements in such a vital process. This is third in a series of reviews that serve as an overview of the role of inorganic elements in regulation of angiogenesis and vascular function. Here we will review the roles of titanium, lithium, cerium, arsenic, mercury, vanadium, niobium, and lead in these processes. The roles of other inorganic elements in angiogenesis were discussed in part I (N, Fe, Se, P, Au, and Ca) and part II (Cr, Si, Zn, Cu, and S) of these series. The methods of exposure, structure, mechanisms, and potential activities of these elements are briefly discussed. An electronic search was performed on the role of these elements in angiogenesis from January 2005 to April 2014. These elements can promote and/or inhibit angiogenesis through different mechanisms. The anti-angiogenic effect of titanium dioxide nanoparticles comes from the inhibition of angiogenic processes, and not from its toxicity. Lithium affects vasculogenesis but not angiogenesis. Nanoceria treatment inhibited tumor growth by inhibiting angiogenesis. Vanadium treatment inhibited cell proliferation and induced cytotoxic effects through interactions with DNA. The negative impact of mercury on endothelial cell migration and tube formation activities was dose and time dependent. Lead induced IL-8 production, which is known to promote tumor angiogenesis. Thus, understanding the impact of these elements on angiogenesis will help in development of new modalities to modulate angiogenesis under various conditions.

Repair of bone defect by nano-modified white mineral trioxide aggregates in rabbit: A histopathological study

BACKGROUND: Many researchers have tried to enhance materials functions in different aspects of science using nano-modification method, and in many cases the results have been encouraging. To evaluate the histopathological responses of the micro-/nano-size cement-type biomaterials derived from calcium silicate-based composition with addition of nano tricalcium aluminate (3CaO.Al2 O3 ) on bone healing response. MATERIAL AND METHODS: Ninety mature male rabbits were anesthetized and a bone defect was created in the right mandible. The rabbits were divided into three groups, which were in turn subdivided into five subgroups with six animals each based on the defect filled by: white mineral trioxide aggregate (WMTA), Nano-WMTA, WMTA without 3CaO.Al2 O3 , Nano-WMTA with 2% Nano-3CaO.Al2 O3 , and empty as control. Twenty, forty and sixty days postoperatively the animals were sacrificed and the right mandibles were removed for histopathological evaluations. Kruskal-Wallis test with post-hoc comparisons based on the LSMeans procedure was used for data analysis. RESULTS: All the experimental materials provoked a moderate to severe inflammatory reaction, which significantly differed from the control group (p< 0.05). Statistical analysis of bone formation and bone regeneration data showed significant differences between groups at 40- and 60- day intervals in all groups. Absence of 3CaO.Al2 O3 leads to more inflammation and foreign body reaction than other groups in all time intervals. CONCLUSIONS: Both powder nano-modification and addition of 2% Nano-3CaO.Al2 O3 to calcium silicate-based cement enhanced the favorable tissue response and osteogenesis properties of WMTA based materials

Repair of bone defect by nano-modified white mineral trioxide aggregates in rabbit: A histopathological study.

BACKGROUND: Many researchers have tried to enhance materials functions in different aspects of science using nano-modification method, and in many cases the results have been encouraging. To evaluate the histopathological responses of the micro-/nano-size cement-type biomaterials derived from calcium silicate-based composition with addition of nano tricalcium aluminate (3CaO.Al2O3) on bone healing response. MATERIAL AND METHODS: Ninety mature male rabbits were anesthetized and a bone defect was created in the right mandible. The rabbits were divided into three groups, which were in turn subdivided into five subgroups with six animals each based on the defect filled by: white mineral trioxide aggregate (WMTA), Nano-WMTA, WMTA without 3CaO.Al2O3, Nano-WMTA with 2% Nano-3CaO.Al2O3, and empty as control. Twenty, forty and sixty days postoperatively the animals were sacrificed and the right mandibles were removed for histopathological evaluations. Kruskal-Wallis test with post-hoc comparisons based on the LSMeans procedure was used for data analysis. RESULTS: All the experimental materials provoked a moderate to severe inflammatory reaction, which significantly differed from the control group (p< 0.05). Statistical analysis of bone formation and bone regeneration data showed significant differences between groups at 40- and 60- day intervals in all groups. Absence of 3CaO.Al2O3 leads to more inflammation and foreign body reaction than other groups in all time intervals. CONCLUSIONS: Both powder nano-modification and addition of 2% Nano-3CaO.Al2O3 to calcium silicate-based cement enhanced the favorable tissue response and osteogenesis properties of WMTA based materials.

Effect of mobile phone use on metal ion release from fixed orthodontic appliances.

INTRODUCTION: The aim of this study was to evaluate the effect of exposure to radiofrequency electromagnetic fields emitted by mobile phones on the level of nickel in saliva. METHODS: Fifty healthy patients with fixed orthodontic appliances were asked not to use their cell phones for a week, and their saliva samples were taken at the end of the week (control group). The patients recorded their time of mobile phone usage during the next week and returned for a second saliva collection (experimental group). Samples at both times were taken between 8:00 and 10:00 pm, and the nickel levels were measured. Two-tailed paired-samples t test, linear regression, independent t test, and 1-way analysis of variance were used for data analysis. RESULTS: The 2-tailed paired-samples t test showed significant differences between the levels of nickel in the control and experimental groups (t [49] = 9.967; P <0.001). The linear regression test showed a significant relationship between mobile phone usage time and the nickel release (F [1, 48] = 60.263; P <0.001; R(2) = 0.577). CONCLUSIONS: Mobile phone usage has a time-dependent influence on the concentration of nickel in the saliva of patients with orthodontic appliances.

Functional role of inorganic trace elements in angiogenesis--Part I: N, Fe, Se, P, Au, and Ca.

Many inorganic elements are recognized as being essential for the growth of all living organisms. Transfer of nutrients and waste material from cells and tissues in the biological systems are accomplished through a functional vasculature network. Maintenance of the vascular system is vital to the wellbeing of organisms, and its alterations contribute to pathogenesis of many diseases. This article is the first part of a review on the functional role of inorganic elements including nitrogen, iron, selenium, phosphorus, gold, and calcium in angiogenesis. The methods of exposure, structure, mechanisms, and potential activity of these elements are briefly summarized. An electronic search was performed on the role of these elements in angiogenesis from January 2005 to April 2014. The recent aspects of the relationship between different elements and their role in angiogenesis, and production of pro- and anti-angiogenic factors were assessed. Several studies emphasized the role of these elements on the different phases of angiogenesis process in vivo. These elements can either enhance or inhibit angiogenesis events. Nitrogen in combination with bisphosphonates has antiangiogenic effects, while nitric oxide promotes the production of angiogenic growth factors. Iron deficiency can stimulate angiogenesis, but its excess suppresses angiogenesis events. Gold nanoparticles and selenium agents have therapeutic effects due to their anti-angiogenic characteristics, while phosphorus and calcium ions are regarded as pro-angiogenic elements. Understanding how these elements impact angiogenesis may provide new strategies for treatment of many diseases with neovascular component.

Functional role of inorganic trace elements in angiogenesis-Part II: Cr, Si, Zn, Cu, and S.

Trace elements play critical roles in angiogenesis events. The effects of nitrogen, iron, selenium, phosphorus, gold, and calcium were discussed in part I. In part II, we evaluated the effect of chromium, silicon, zinc, copper, and sulfur on different aspects of angiogenesis, with critical roles in healing and regeneration processes, and undeniable roles in tumor growth and cancer therapy. This review is the second of series that serves as an overview of the role of inorganic elements in regulation of angiogenesis and vascular function. The methods of exposure, structure, mechanism, and potential activity of these trace elements are briefly discussed. An electronic search was performed on the role of these trace elements in angiogenesis from January 2005 to April 2014. The recent aspects of the relationship between five different trace elements and their role in regulation of angiogenesis, and homeostasis of pro- and anti-angiogenic factors were assessed. Many studies have investigated the effects and importance of these elements in angiogenesis events. Both stimulatory and inhibitory effects on angiogenesis are observed for the evaluated elements. Chromium can promote angiogenesis in pathological manners. Silicon as silica nanoparticles is anti-angiogenic, while in calcium silicate extracts and bioactive silicate glasses promote angiogenesis. Zinc is an anti-angiogenic agent acting on important genes and growth factors. Copper and sulfur compositions have pro-angiogenic functions by activating pro-angiogenic growth factors and promoting endothelial cells migration, growth, and tube formation. Thus, utilization of these elements may provide a unique opportunity to modulate angiogenesis under various setting.

Effect of particle size on calcium release and elevation of pH of endodontic cements.

BACKGROUND/AIM: Elevation of pH and calcium ion release are of great importance in antibacterial activity and the promotion of dental soft and hard tissue healing process. In this study, we evaluated the effect of particle size on the elevation of pH and the calcium ion release from calcium silicate-based dental cements. MATERIAL AND METHODS: Twelve plastic tubes were divided into three groups, filled with white mineral trioxide aggregate (WMTA), WMTA plus 1% methylcellulose, and nano-modified WMTA (nano-WMTA), and placed inside flasks containing 10 ml of distilled water. The pH values were measured using a pH sensor 3, 24, 72, and 168 h after setting of the cements. The calcium ion release was measured using an atomic absorption spectrophotometer with same sample preparation method. Data were subjected to two-way analysis of variance (anova) followed by post hoc Tukey tests with significance level of P < 0.05. RESULTS: Nano-WMTA showed significant pH elevation only after 24 h (P < 0.05) compared with WMTA, and after 3, 24, and 72 h compared with WMTA plus 1% methylcellulose (P < 0.05). Nano-WMTA showed significantly higher calcium ion release values compared to the other two groups (P < 0.05). CONCLUSIONS: Nano-modification of WMTA remarkably increased the calcium ion release at all time intervals postsetting, which can significantly influence the osteogenic properties of human dental pulp cells and as a consequence enhance mineralized matrix nodule formation to achieve desirable clinical outcomes. However, the increase in pH values mainly occurred during the short time postsetting. Addition of 1% methylcellulose imposed a delay in elevation of pH and calcium ion release by WMTA.

Radiopacifier particle size impacts the physical properties of tricalcium silicate-based cements.

INTRODUCTION: The aim of this study was to evaluate the impact of radiopaque additive, bismuth oxide, particle size on the physical properties, and radiopacity of tricalcium silicate-based cements. METHODS: Six types of tricalcium silicate cement (CSC) including CSC without bismuth oxide, CSC + 10% (wt%) regular bismuth oxide (particle size 10 µm), CSC + 20% regular bismuth oxide (simulating white mineral trioxide aggregate [WMTA]) as a control, CSC + 10% nano bismuth oxide (particle size 50-80 nm), CSC + 20% nano-size bismuth oxide, and nano WMTA (a nano modification of WMTA comprising nanoparticles in the range of 40-100 nm) were prepared. Twenty-four samples from each group were divided into 4 groups and subjected to push-out, surface microhardness, radiopacity, and compressive strength tests. Data were analyzed by 1-way analysis of variance with the post hoc Tukey test. RESULTS: The push-out and compressive strength of CSC without bismuth oxide and CSC with 10% and 20% nano bismuth oxide were significantly higher than CSC with 10% or 20% regular bismuth oxide (P < .05). The surface microhardness of CSC without bismuth oxide and CSC with 10% regular bismuth oxide had the lowest values (P < .05). The lowest radiopacity values were seen in CSC without bismuth oxide and CSC with 10% nano bismuth oxide (P < .05). Nano WMTA samples showed the highest values for all tested properties (P < .05) except for radiopacity. CONCLUSIONS: The addition of 20% nano bismuth oxide enhanced the physical properties of CSC without any significant changes in radiopacity. Regular particle-size bismuth oxide reduced the physical properties of CSC material for tested parameters.

Effect of endodontic cement on bone mineral density using serial dual-energy x-ray absorptiometry.

INTRODUCTION: Materials with new compositions were tested in order to develop dental materials with better properties. Calcium silicate-based cements, including white mineral trioxide aggregate (WMTA), may improve osteopromotion because of their composition. Nano-modified cements may help researchers produce ideal root-end filling materials. Serial dual-energy x-ray absorptiometry measurement was used to evaluate the effects of particle size and the addition of tricalcium aluminate (C3A) to a type of mineral trioxide aggregate-based cement on bone mineral density and the surrounding tissues in the mandible of rabbits. METHODS: Forty mature male rabbits (N = 40) were anesthetized, and a bone defect measuring 7 × 1 × 1 mm was created on the semimandible. The rabbits were divided into 2 groups, which were subdivided into 5 subgroups with 4 animals each based on the defect filled by the following: Nano-WMTA (patent application #13/211.880), WMTA (as standard), WMTA without C3A, Nano-WMTA + 2% Nano-C3A (Fujindonjnan Industrial Co, Ltd, Fujindonjnan Xiamen, China), and a control group. Twenty and forty days postoperatively, the animals were sacrificed, and the semimandibles were removed for DXA measurement. RESULTS: The Kruskal-Wallis test followed by the Mann-Whitney U test showed significant differences between the groups at a significance level of P < .05. P values calculated by the Kruskal-Wallis test were .002 for bone mineral density at both intervals and P20 day = .004 and P40 day = .005 for bone mineral content. CONCLUSIONS: This study showed that bone regeneration was enhanced by reducing the particle size (nano-modified) and C3A mixture. This may relate to the existence of an external supply of minerals and a larger surface area of nano-modified material, which may lead to faster release rate of Ca(2+), inducing bone formation. Adding Nano-C3A to Nano-WMTA may improve bone regeneration properties.