Synthesis and chemical characterization of new silica polyethylene glycol hybrid nanocomposite materials for controlled drug delivery

Coating of Titanium Substrates with ZrO2 and ZrO2-SiO2 Composites by Sol-Gel Synthesis for Biomedical Applications: Structural Characterization, Mechanical and Corrosive Behavior

The use of metallic materials as implants presents some major drawbacks, such as their harmful effects on the living organism, especially those induced by corrosion. To overcome this problem, the implant surface of titanium implants can be improved using a coating of bioactive and biocompatible materials. The aim of this work is the synthesis of SiO2/ZrO2 composites with different percentages of zirconia matrix (20, 33 and 50 wt.%), by the sol-gel method to coat commercial Grade 4 titanium disks using a dip coater. Attenuated total reflectance Fourier transform infrared (ATR/FTIR) spectroscopy was used to evaluate the interactions between the inorganic matrices. Furthermore, the mechanical properties and corrosive behavior of the SiO2/ZrO2 coatings were evaluated as a function of the ZrO2 content. The bioactive properties of the substrate coated with different composites were evaluated using simulated body fluid (SBF). The antibacterial activity was tested against gram-negative and gram-positive Escherichia coli and Enterococcus faecalis, respectively, to assess the release of toxic products from the different composites and to evaluate the possibility of using them in the biomedical field.

Drug Release of Hybrid Materials Containing Fe(II)Citrate Synthesized by Sol-Gel Technique

The use of oral iron integration is commonly recommended for the treatment of iron deficiency, nevertheless the diagnosis and treatment of this disease could clearly be improved. The aim of this work was the synthesis of therapeutic systems, iron (II) based, by sol-gel method. In an SiO₂ matrix, we embedded different weight percentages of polyethylene glycol (PEG6, 12, 24 wt%) and ferrous citrate (Fe(II)C5, 10, 15 wt%) for drug delivery applications. Fourier Transform Infrared (FTIR) spectroscopy was used to study the interactions among different components in the hybrid materials. Release kinetics in a simulated body fluid (SBF) were investigated and the amount of Fe2+ released was detected by Ultraviolet⁻Visible spectroscopy (UV-VIS) after reaction with ortho-phenantroline. Furthermore, the biological characterization was carried out. The bioactivity of the synthesized hybrid materials was evaluated by the formation of a layer of hydroxyapatite on the surface of samples soaked in SBF using FTIR spectroscopy. Finally, also, the potential antibacterial properties of the different materials against two different bacteria, E. coli and P. aeruginosa, were investigated.

Novel Hydrogel-Advanced Modified Clay Nanocomposites as Possible Vehicles for Drug Delivery and Controlled Release

Present study refers to the synthesis of new advanced materials based on poly(methacrylic acid) (PMAA) with previously reported own advanced modified clays by edge covalent bonding. This will create the premises to obtain nanocomposite hydrogels with combined hydrophilic-hydrophobic behavior absolutely necessary for co-delivery of polar/nonpolar substances. For the synthesis, N,N'-methylenebisacrylamide was used as cross-linker and ammonium persulphate as initiator. As a consequence of the inclusion of clay into the polymer matrix and the intercalation of PMAA between the layers as well as the presence of hydrophobic interactions occurred between partners, the final hydrogel nanocomposites possessed greater swelling degrees, slower de-swelling process and enhanced mechanical properties depending on the clay type in comparison with pure hydrogel. In vitro MTS ([3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt]) colorimetric assay showed that direct exposure with PMMA-clay-based constructs did not affect cell viability and proliferation in time (24 and 48 h) on either normal or adenocarcinoma cell lines.

Investigation of bioactivity, biocompatibility and thermal behavior of sol-gel silica glass containing a high PEG percentage

SiO2/PEG organic-inorganic hybrid materials, which contain 60 or 70 weight percentage of PEG, were synthesized by the sol-gel technique. The materials were characterized and subjected to various tests to assess their application in the biomedical field. The evaluation of their morphology by scanning electron microscopy (SEM) confirms the homogeneity of the samples on the nanometer scale. Fourier transform infrared spectroscopy (FT-IR) indicated that the two components of the hybrids (SiO2 and PEG) are linked by hydrogen bonds. This feature makes them class I hybrids. Simultaneous thermogravimetry/differential thermal analysis (TG/DTA) was used to investigate their thermal behavior and to establish the best temperatures for their pre-treatment. The fundamental properties that a material must have to be used in the biomedical field are biocompatibility and bioactivity. The formation of a hydroxyapatite layer was observed on the hybrid surface by SEM/EDX and FTIR after soaking in simulated body fluid. This indicates that the materials are able to bond to bone tissue. Moreover, the biocompatibility of SiO2/PEG hybrids was assessed by performing WST-8 cytotoxicity tests on fibroblast cell NIH 3T3 after 24h of exposure. The cytotoxicity tests highlight that the cell viability is affected by the polymer percentage. The results showed that the synthesized materials were bioactive and biocompatible. Therefore, the results obtained are encouraging for the use of the obtained hybrids in dental or orthopedic applications.

Coatings of titanium substrates with xCaO · (1 - x)SiO2 sol-gel materials: characterization, bioactivity and biocompatibility evaluation

The objective of this study has been to develop low temperature sol-gel coatings to modify the surface of commercially pure titanium grade 4 (a material generally used in dental application) and to evaluate their bioactivity and biocompatibility on the substrate. Glasses of composition expressed by the following general formula xCaO · (1 - x)SiO2 (0.0<x<0.60) have been prepared by means of the sol-gel route starting from tetraethyl orthosilicate and calcium nitrate tetrahydrate. Those materials, still in the sol phase, have been used to coat titanium substrates by means of the dip-coating technique. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) allowed the materials to be characterized and a microstructural analysis of the coatings obtained was performed using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated titanium was immersed in simulated body fluid (SBF) for 21 days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. To investigate cell-material interactions, mouse embryonic fibroblast cells (3T3) were seeded onto the specimens and the cell viability was evaluated by a WST-8 assay.

Silica/quercetin sol-gel hybrids as antioxidant dental implant materials

The development of biomaterials with intrinsic antioxidant properties could represent a valuable strategy for preventing the onset of peri-implant diseases. In this context, quercetin, a naturally occurring flavonoid, has been entrapped at different weight percentages in a silica-based inorganic material by a sol-gel route. The establishment of hydrogen bond interactions between the flavonol and the solid matrix was ascertained by Fourier transform infrared spectroscopy. This technique also evidenced changes in the stretching frequencies of the quercetin dienonic moiety, suggesting that the formation of a secondary product occurs. Scanning electron microscopy was applied to detect the morphology of the synthesized materials. Their bioactivity was shown by the formation of a hydroxyapatite layer on sample surface soaked in a fluid that simulates the composition of human blood plasma. When the potential release of flavonol was determined by liquid chromatography coupled with ultraviolet and electrospray ionization tandem mass spectrometry techniques, the eluates displayed a retention time that was 0.5 min less than quercetin. Collision-activated dissociation mass spectrometry and untraviolet-visible spectroscopy were in accordance with the release of a quercetin derivative. The antiradical properties of the investigated systems were evaluated by DPPH and ABTS methods, whereas the 2,7-dichlorofluorescein diacetate assay highlighted their ability to inhibit the H₂O₂-induced intracellular production of reactive oxygen species in NIH-3T3 mouse fibroblast cells. Data obtained, along with data gathered from the MTT cytotoxicity test, revealed that the materials that entrapped the highest amount of quercetin showed notable antioxidant effectiveness.