Sol–gel synthesis and thermal behavior of bioactive ferrous citrate–silica hybrid materials

Imbalance of the iron level in the body causes several diseases. In particular, the low level of iron, during pregnancy, is responsible for the iron deficiency anemia, and even of neurodegenerative diseases. Although the treatment of iron deficiency anemia with oral iron supplements has been known, this problem still afflicts many people. The aim of this work was the development of a system able to release ferrous ions in a controlled manner. Controlled drug release for medical applications, indeed, appears to be a very interesting alternative to a systemic therapy because it is assurance of treatment continuity and drug stability and optimizes drug absorption. For this purpose, ferrous citrate (Fe(II)C) was synthesized by a redox reaction between iron powder and citric acid. Fourier transform infrared spectroscopy (FTIR), 1,10-phenanthroline and sodium thiocyanate colorimetric assays confirmed that only Fe(II)C was obtained by redox reaction. Afterward, obtained Fe(II)C was embedded within a SiO2 matrix in different mass percentage, by means of a sol–gel route. FTIR spectroscopy and simultaneous thermogravimetry/first-order derivative of thermogravimetry were used to confirm the Fe(II)C presence in the silica matrix and to investigate the thermal behavior of the sol–gel materials, respectively. The bioactivity test carried out by soaking the synthesized drug delivery systems in a simulated body fluid showed that the biological properties of the silica matrix are not modified by the presence of Fe(II)C

Hydration of triethylenetetramine based inhibitor film accelerates the chloride-induced corrosion in concrete: a molecular dynamics study

Abstract. Organic corrosion inhibitors can be used to prevent chloride-induced corrosion in reinforced concrete structures. In this theoretical study Molecular Mechanics (MM) and Molecular Dynamics (MD) simulations are performed in order to better understand the interaction mechanisms with the passive film present on steel [1], in particular considering γ-FeOOH surface as solid surface which can be subject to chloride-induced corrosion process and the dimethylethanolamine (TETA) film [2]. The MD simulations are a very useful tool because they describe at atomistic level both the solid surface and organic inhibitors molecules in presence of chloride ions [2] and water molecules [3]. Hydration of organic TETA inhibitor film in presence of chloride ions always accelerate the corrosion process, as experimentally well known. In this theoretical work water molecules in fact induce chloride ions to adsorb on γ-FeOOH surface more quickly and in greater numbers respect with to the same simulations study without water molecules. This kind of organic film cannot exhibit a good behavior to prevent the chloride-induced corrosion process not displaying the so important repulsion to chloride ions. The hydration accelerates the corrosion process. This theoretical work permit to compare these results with another organic inhibitors films studied in previous work [1] in order to prevent the corrosion. References [1] M.V. Diamanti, E. A. Pérez-Rosales, G. Raffaini, F. Ganazzoli, A. Brenna, M. Pedeferri, M. Ormellese, Corrosion Science, 100, 231-241 (2015). [2] G. Raffaini, M. Catauro, F. Ganazzoli, F. Bolzoni, M. Ormellese, Macromolecular Symposia, 395, Article Number: 2000231, pp. 1-3 (2021). [3] G. Raffaini, F. Ganazzoli, J. of Biomed. Mat. Res. PART A, 92A, 1382-1391 (2006)

FT-IR characterization of antimicrobial hybrid materials through sol-gel synthesis

Silica/polycaprolactone and titania/polycaprolactone hybrid organic/inorganic amorphous composites were prepared via a sol-gel method starting from a multi-element solution containing tetramethyl orthosilicate (TMOS) or titanium butoxide (TBT), polycaprolactone (PCL), water and methylethylketone (MEK). The molecular structure of the crosslinked network was based on the presence of the hydrogen bonds between organic/inorganic elements as confirmed by Fourier Transform Infra-Red (FT-IR) analysis. In particular, the structure of crosslinked network was realized by hydrogen bonds between the X-OH (X = Si or Ti) group (H donator) in the sol-gel intermediate species and ester groups (H-acceptors) in the repeating units of the polymer. The morphology of the hybrid materials; pore size distribution, elemental homogeneity and surface features, was studied by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and by atomic force microscopy (AFM). The bioactivity of the synthesized hybrid materials was confirmed by observing the formation of a layer of hydroxyapatite (HAP) on the surface of the samples soaked in a simulated body fluid. The antimicrobial behavior of synthetized hybrids was also assessed against Escherichia coli bacteria. In conclusion, the prepared hybrid materials are proposed for use as future bone implants

Kinetics of the Non-isothermal Degradation of POSS/EPDM Hybrids Composites

Polyhedral Oligomeric Silsesquioxane (POSS)/Ethylene-propylene-diene monomer (EPDM) composite, at 3% wt of POSS, is prepared by the evaporation of solvent (CHCl3) from polymer/filler system at room temperature and is investigated, by the means of thermogravimetric analysis (TGA), and the obtained TGA data are treated by the Kissinger method to get the apparent activation energy (Ea) of degradation. The results obtained for the composites, at different levels of irradiation, are discussed and compared with each other and with those obtained for pristine EPDM. A good improvement of the thermal stability, with respect to the neat polymer, is found showing the effect of the POSS molecules on the degradation rate. A classification among the samples at different levels of radiations is also drawn up, showing also in this case, the beneficial effect of the POSSs presence

A Molecular Dynamics Study of Noncovalent Interactions between Rubber and Fullerenes

The percolation and networking of filler particles is an important issue in the field of rubber reinforcement, and much effort is given to clarify the true nature of the reinforcement mechanism and the viscoelastic behavior. The concentration of nanofillers also in the presence of large amounts of carbon black is a parameter that can influence the macroscopic rubber behavior. In this paper, noncovalent interactions between C60 fullerenes with poly-1,4-cis-isoprene (PI) either as such or modified are studied through atomistic simulations based on molecular mechanics (MM) and molecular dynamics (MD) methods. At first, the conformational properties of a single chain and of 12 PI chains in a periodic simulation box are studied. Afterwards, the conformational properties of a single PI chain polymer terminated with a -COOH group, and then a bulk system formed by chains of unmodified and some PI modified chains are considered. Then, the systems formed by adding fullerenes to these two different bulk systems are studied. Relatively small interaction energy between rubber and fullerenes being well dispersed in the sample is found. The simulations showed a preferential tendency of fullerenes to display self-aggregation, in the presence of even a small fraction of modified polymer chains

Thermostabilized Shelf Life Study

The objective of this project is to determine the shelf life end-point of various food items by means of actual measurement or mathematical projection. The primary goal of the Advanced Food Technology Project in these long duration exploratory missions is to provide the crew with a palatable, nutritious and safe food system while minimizing volume, mass, and waste. The Mars missions could be as long as 2.5 years with the potential of the food being positioned prior to the crew arrival. Therefore, it is anticipated that foods that are used during the Mars missions will require a 5 year shelf life. Shelf life criteria are safety, nutrition, and acceptability. Any of these criteria can be the limiting factor in determining the food's shelf life. Due to the heat sterilization process used for the thermostabilized food items, safety will be preserved as long as the integrity of the package is maintained. Nutrition and acceptability will change over time. Since the food can be the sole source of nutrition to the crew, a significant loss in nutrition may determine when the shelf life endpoint has occurred. Shelf life can be defined when the food item is no longer acceptable. Acceptability can be defined in terms of appearance, flavor, texture, or aroma. Results from shelf life studies of the thermostabilized food items suggest that the shelf life of the foods range from 0 months to 8 years, depending on formulation

Physico-chemical properties of PEG-based inorganic hybrids

Organic-inorganic composites can be conveniently obtained by sol-gel recipes as class-I or class-II hybrids. They can find interesting applications in several fields, including drug delivery, scaffolding, bio-sensing, energetics, etc. In this paper we reconsider and reinvestigate our previous work in the field, by considering the sol-gel synthesis and physico-chemical characterization of class-I hybrids, and by trying to highlight some unifying elements that can be of help for the development of more efficient and precise synthesis methods. In particular, we will discuss systems based on poly(ethylene glycol) with SiO2 (1) and ZrO2 (2) as the ceramic phase. Emphasis will be put on the role played by solid-state NMR spectroscopy in unveiling the interactions at the base of hybrid formation. (1) Catauro, M., Bollino, F., Papale, F., Ferrara, C., Mustarelli, P., Silica-polyethylene glycol hybrids synthesized by sol-gel: Biocompatibility improvement of titanium implants by coating, Materials Science and Engineering C, 2015, 55, 5451. (2) Catauro, M., Bollino, F., Papale, F., Pacifico, S., Galasso, S., Ferrara, C., Mustarelli, P. Synthesis of zirconia/polyethylene glycol hybrid materials by sol-gel processing and connections between structure and release kinetic of indomethacin, Drug Delivery, 2014, 21, 595-604

Geopolymer/PEG Hybrid Materials Synthesis and Investigation of the Polymer Influence on Microstructure and Mechanical Behavior

Geopolymers are aluminosilicate inorganic polymers, obtained from the alkali activation of powders containing SiO2+Al2O3>80wt%, mainly proposed as environmentally friendly building materials. In this work, metakaolin-based geopolymers have been prepared and a water-soluble polymer, polyethylene glycol (PEG), has been added in different percentages to obtain organic-inorganic hybrid geopolymers. The influence of both the polymer amount and aging time on the structure and the mechanical behavior of the materials were investigated. FTIR spectroscopy allowed us to follow the evolution of the aluminosilicate framework during the geopolymerization process. This analysis revealed that PEG leads to a network which is rich in Al-O-Si bonds and forms H-bonds with the inorganic phase. SEM microscope showed that the two phases are interpenetrated on micrometric scales. Traction and bending tests have been carried out on appropriate samples to investigate the mechanical behavior of the obtained hybrids, showing that both PEG content and aging time affect the material behavior

A novel SiO2/Polyetherimide (PEI) Composite Synthesized by Sol-Gel Route: Characterization and Antibacterial Activity

Polyetherimide (PEI), an amorphous thermoplastic material, is a promising candidate for wide applications due to its high heat stability and its biocompatibility in human tissues. In the present paper, PEI (4 wt%) is added to SiO2 inorganic matrix in order to obtain a novel composite biomaterial through sol-gel route. Structural characterization by means of Fourier Transform Infrared Spectroscopy (FTIR) confirmed, through hydrogen bond interactions, the presence of both organic and inorganic components in the structure. Concerning the compatibility in the biological systems, a study of antibacterial properties is carried out, analyzing the effect of SiO2/PEI composite on Escherichia coli (gram-negative) and Enterococcus faecalis (gram-positive)

Physicochemical Properties of PEG-Based Inorganic Hybrids Obtained via Sol-Gel

Organic-inorganic composites can be conveniently obtained by sol-gel recipes. They can find interesting applications in several fields, including drug delivery, scaffolding, bio-sensing, energetics, etc. Herein, we reconsider and reinvestigate our previous work in the field, by considering the sol-gel synthesis and physicochemical characterization of class-I organic-inorganic hybrids, and by trying to highlight some unifying elements that can be of help for the development of more efficient and precise synthesis methods. Systems based on poly(ethylene glycol) with SiO2 and ZrO2 as the ceramic phase will be discussed. Emphasis will be put on the role played by solid-state NMR spectroscopy in unveiling the interactions at the base of hybrid formation