Mariana Prodana

A Molecular Pillar Approach To Grow Vertical Covalent Organic Framework Nanosheets on Graphene: Hybrid Materials for Energy Storage

Hybrid 2D-2D materials composed of perpendicularly oriented covalent organic frameworks (COFs) and graphene were prepared and tested for energy storage applications. Diboronic acid molecules covalently attached to graphene oxide (GO) were used as nucleation sites for directing vertical growth of COF-1 nanosheets (v-COF-GO). The hybrid material has a forest of COF-1 nanosheets with a thickness of 3 to 15 nm in edge-on orientation relative to GO. The reaction performed without molecular pillars resulted in uncontrollable growth of thick COF-1 platelets parallel to the surface of GO. The v-COF-GO was converted into a conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge-on orientation. It was demonstrated as a high-performance electrode material for supercapacitors. The molecular pillar approach can be used for preparation of many other 2D-2D materials with control of their relative orientation.

Microstructure, surface characterization and long-term stability of new quaternary Ti-Zr-Ta-Ag alloy for implant use

The novel Ti-20Zr-5Ta-2Ag alloy was characterised concerning its microstructure, morphology, mechanical properties, its passive film composition and thickness, its long-term electrochemical stability, corrosion resistance, ion release rate in Ringer solution of acid, neutral and alkaline pH values and antibacterial activity. The new alloy has a crystalline α microstructure (by XRD). Long-term XPS and SEM analyses show the thickening of the passive film and the deposition of hydroxyapatite in neutral and alkaline Ringer solution. The values of the electrochemical parameters confirm the over time stability of the new alloy passive film. All corrosion parameters have very favourable values in time which attest a high resistance to corrosion. Impedance spectra evinced a bi-layered passive film formed by the barrier, insulating layer and the porous layer. The monitoring of the open circuit potentials indicated the stability of the protective layers and their thickening in time. The new alloy releases (by ICP-MS measurements) very low quantities of Ti, Zr, Ag ions and no Ta ions. The new alloy exhibits a low antibacterial activity.

Biomimetic Hybrid Inorganic/Organic Coatings in the Increasing of the Integration Capacity of TiAlVZr Bioalloy

This paper will address key issues related to the synthesis, characterization and utilization of inorganic/organic hybrid coatings on TiAlVZr bioalloy to control adsorption at interface and the integration capacity of the implant. To enhance the integration capacity function of the biomaterial is necessary to control the composition and structure via the use of hybrid materials consisting of organic and inorganic biomimetic phases [1,2]. Such composite coatings mimic the structure of natural materials of tissues, in our case hydroxyapatite (HA) by association of bovine serum albumin (BSA) with calcium phosphates matrices. Calcium phosphate coating have been deposited on metal substrates by electrochemical method.

Fabrication and toxicity characterization of a hybrid material based on oxidized and aminated MWCNT loaded with carboplatin.

This study focused on the fabrication and toxicity characterization of a hybrid material-based on the multiple functionalizations of multiwalled carbon nanotubes (MWCNTs) with carboxyl or amino groups and the anti-tumor drug carboplatin (CP). The functionalization was evidenced by Fourier transformed infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC). The amount of platinum ions released in the simulated body fluid (SBF) was assessed by inductively coupled plasma mass spectrometry (ICP-MS). Cell viability, nanotubes cellular uptake, cell proliferation, superoxide anion production, SOD activity, intracellular glutathione and protein expression of several molecules involved in breast tumor cell survival and death were investigated after 24h exposure. Exposure to the aminated carbon nanotubes loaded with carboplatin resulted in a greater decrease of viability compared to oxidized carbon nanotubes loaded with the same drug, which was in an inversely proportional relationship with the production of superoxide anions in breast cancer cells. The inhibition of Hsp60, Hsp90, p53 and Mdm2 protein expression was induced as a consequence of the cytoprotection mechanism failure. Overexpression of Beclin1 and the reduction of Bcl2 expression were also observed, suggesting that functionalized MWCNT loaded with CP trigger cell death via autophagy in breast cancer cells.

BSA/HA Coating on Titanium Alloy for Direct Bond Formation

A biomimetic bovine serum albumin protein/hydroxyapatite coating was prepared by electrochemically co-precipitation on TiAlZr surface. Coating prepared in the presence and in absence of BSA were characterized by Scanning electron microscopy (SEM), Fourier Transformat Infrared microscopy (FTIR), and contact angle measurements. The calcium ion release content was determined using the inductively coupled plasma spectrophotometer (ICP-MS). The advantages of this chip and convenient electrochemical procedure of bioactivation is discussed over the commonly used procedures which prepared phosphate coatings modulate their properties without imitation of the mode in which hydroxyapatite bone crystals are formed in the body.

Hydrogen Chemical Configuration and Thermal Stability in Tungsten Disulfide Nanoparticles Exposed to Hydrogen Plasma

The chemical configuration and interaction mechanism of hydrogen adsorbed in inorganic nanoparticles of WS2 are investigated. Our recent approaches of using hydrogen activated by either microwave or radiofrequency plasma dramatically increased the efficiency of its adsorption on the nanoparticles surface. In the current work we make an emphasis on elucidation of the chemical configuration of the adsorbed hydrogen. This configuration is of primary importance as it affects its adsorption stability and possibility of release. To get insight on the chemical configuration, we combined the experimental analysis methods with theoretical modeling based on the density functional theory (DFT). Micro-Raman spectroscopy was used as a primary tool to elucidate chemical bonding of hydrogen and to distinguish between chemi- and physisorption. Hydrogen adsorbed in molecular form (H2) was clearly identified in all the plasma-hydrogenated WS2 nanoparticles samples. It was shown that the adsorbed hydrogen is generally stable under high vacuum conditions at room temperature, which implies its stability at the ambient atmosphere. A DFT model was developed to simulate the adsorption of hydrogen in the WS2 nanoparticles. This model considers various adsorption sites and identifies the preferential locations of the adsorbed hydrogen in several WS2 structures, demonstrating good concordance between theory and experiment and providing tools for optimizing of hydrogen exposure conditions and the type of substrate materials.

Evaluation of Heavy Metals of Temporary Teeth From Areas with Different Pollution Level

The aim of the paper is to evaluate the heavy metals of temporary teeth collected from areas with various environmental pollution. It is a new approach, trying to correlate the amount of heavy metals determined with inductively plasma mass spectroscopy (ICP-MS) in enamel and dentine with hydrophilic properties at interface and the type of teeth. The paper established specific correlation of the teeth type and the amount of heavy metals indicating ranges for girls and boys. Such ranges were proposed for teeth type and hydrophilic character as well.

Alkaline Phosphatase Immobilization on New Chitosan Membranes with Mg2+ for Biomedical Applications

In this paper, we present the fabrication and characterization of new chitosan-based membranes while using a new biotechnology for immobilizing alkaline phosphatase (ALP). This technology involved metal ions incorporation to develop new biopolymeric supports. The chemical structure and morphological characteristics of proposed membranes were evaluated by infrared spectroscopy (FT-IR) and the scanning electron microscopy technique (SEM). The inductively coupled plasma mass spectrometry (ICP-MS) evidenced the metal ion release in time. Moreover, the effect of Mg2+ on the enzymatic activity and the antibacterial investigations while using Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria, hemolysis, and biocompatibility behavior were studied. Immobilizing ALP into the chitosan membranes composition followed by the incorporation of Mg2+ led to polymeric supports with enhanced cellular viability when comparing to chitosan-based membranes without Mg2+. The results obtained evidenced promising performance in biomedical applications for the new biopolymeric supports that are based on chitosan, ALP, and metal ions.

Biomimetic calcium phosphate coating of CoCr alloys

CoCr aloys are most common material used as implantable material because of it reduced cost and good mechanical properties. This work presents our results of obtaining biomimetic calcium phosphate coating of CoCr and to characterize the properties of such coatings. The coating was prepared by immersing the CoCr substrates into the simulated body fluid (SBF) containing Ca ions in sealed plastic bottles, kept at room temperature for one, fourteen and twenty one days. Detailed characterization including chemical, structural and morphological characterization (SEM, EDS, X-ray diffraction) were perfomed. ICP/MS (inductively coupled plasma mass spectrometer) determinations sustain chemical results put in evidence by Fourier Transformed Infrared Spectroscopy (FTIR), the ions release being much smaller for phosphate coatings formed after longer immersion time in SBF. The hydrophilic/hydrophobic character of the coatings was put in evidence by contact angle measurements (CA).

The Hybridization of Multi-Walled Carbon Nanotubes with Various Drugs

Functionalized multiwalled carbon nanotubes (MWCNTs) by various groups (carboxyl or amino) can improve the properties of anti-tumoral drugs (cisplatin, docetaxel, zometa). Functionalization was evidenced by infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Platinum ions released in simulated body fluid (SBF) were measured by inductively coupled plasma ion spectrometry (ICP-MS).