Pretreatment Of Gel Research Articles

Electrochemical investigation of high-performance silane sol–gel films containing clay nanoparticles

Silane sol–gel coatings are widely used as adhesion promoters between inorganic substrates, such as metals, and organic coatings. The aim of these pre-treatments is to enhance the corrosion protection performance of the organic coating improving the adhesion to the substrate and acting as a barrier against water and aggressive ions diffusion. It is a matter of fact that the silane sol–gel pre-treatments do not provide an active protection against corrosion processes except for the partial inhibition of the cathodic reaction. Inorganic pigments can improve the barrier properties of the silane sol–gel film, enhancing the resistance against corrosion. In this study, different amounts of montmorillonite nanoparticles were added to a water based silanes mixture in order to improve the barrier properties of the sol–gel coating. Hot dip galvanized steel was used as substrate. The sol–gel film consists of a combination of three different silanes, GPS, TEOS and MTES. The clay nanoparticles used in this study were mainly neat montmorillonite. The proper concentration of filler inside the sol–gel films was determined comparing the corrosion resistance of silane layers with different nanoparticles contents. Additionally, the effect of CeO 2 and Ce 2O 3 enriched montmorillonite particles. The EIS analysis and the polarization measurements demonstrated that the optimal amount of neat montmorillonite nanoparticles is about 1000 ppm. The same electrochemical techniques highlighted the limited effect of the cerium oxides grafted to the clay nanoparticles on the corrosion resistance of the silane sol–gel film. The TEM analysis proved the presence of a nano-crystalline structure inside the silane sol–gel film due to the formation of crystalline silica domains.

Impact of Matrix-Associated Soluble Factors on The Specificity of The Immunogenicity Assessment

Specificity and sensitivity are essential in assays for immunogenicity assessment of biotherapeutics. Nonspecific interactions from excess therapeutic or anti-therapeutic antibody, soluble ligands (e.g., target receptor), or serum proteins associated with autoimmune conditions (e.g., rheumatoid factor) in samples can impact the detection of a true anti-therapeutic response. Electrochemiluminescence-based bridging assay formats could eliminate the interference due to rheumatoid factor with no pretreatment with Melon Gel™ or aggregated IgG. The interference due to soluble factors was not platform specific for the four therapeutics evaluated in this study. Melon Gel pretreatment and avidin high-bind (Meso Scale Discovery) plates can effectively reduce interference due to rheumatoid factor in ELISA- and electrochemiluminescence-based assays, respectively. Excess levels of therapeutic and anti-therapeutic antibodies in bridging assays can impact assay specificity.

The Efficacy of Dihydrotestosterone Transdermal Gel Pretreatment in Primary Hypospadias Surgery: A Prospective, Controlled Randomized Study

PURPOSE Efficacy evaluation of transdermal dihydrotestosterone (DHT) treatment based on the results of hypospadias repair in children with primary hypospadias. MATERIAL AND METHODS Between September 2004 and April 2006, a randomized total of 75 children with primary hypospadias with a mean age of 33.4±3.7 months were evaluated. While 37 children (Group 1) were treated with a daily application of 2.5% DHT transdermal gel for 3 months, 38 children of group 2 did not receive DHT before operation. All children underwent hypospadias repair using tubularized incised plate urethroplasty. Postoperative complications of the children were analysed using the Mann-Whitney U test with respect to fistula, urethral strictures, meatal stenosis, glandular dehiscence and scar formation. RESULTS 4 patients (10.5%) of group 2 developed urethrocutaneous fistulae compared to group 1 in which only one fistula was found (2.7% p>0.05). While 3 patients (7.8%) in group 2 had glandular dehiscence, no patients in the DHT group had one (p<0.05). There were 2 cases with meatal stenosis in group 2 (5.2%), but no patient with meatal stenosis in group 1 (p>0.05). There were 16 cases (42.1%) with moderate to severe scar formation in group 2, whereas only two children (5.4%) had scar formation in the DHT group (p<0.05). There was a significant difference between the overall re-operation rates of group 2 (23.8%, 9 patients) and group 1 (2.7%, one patient) (p<0.05). CONCLUSIONS Pretreatment with DHT transdermal gel was found to be effective in decreasing the complications and improving the cosmetic results after hypospadias repair.

Electrochemical behaviour of ZrO 2 sol–gel pre-treatments on AA6060 aluminium alloy

ZrO 2 pre-treatments applied with the sol–gel technique are a possible replacement of chromium based pre-treatments on aluminium alloys. The thickness and homogeneity of the films deposited on AA6060 alloy are strongly related to the process parameters like preparation of the surface, number of dips and thermal treatment of the film. ZrO 2 films were prepared using the dip-coating technique in sol obtained from metal-organic precursors in an organic solvent (0.1 M Zr(OBu n ) 4 in anhydrous n-butanol with addition of acetic acid as complexing agent). Different layers were applied on AA6060 changing number of dips and thermal treatment (150 °C for 1 h or 250 °C for 4 min). The typical thickness of the deposited layers was in the range 70–180 nm depending on process parameters. The electrochemical behaviour of the pre-treated alloy in diluted Harrison solution (0.05 wt% NaCl + 0.35 wt% (NH 4) 2SO 4) was investigated by means of potentiodynamic polarization, open circuit potential measurements, and electrochemical impedance spectroscopy. In addition, the electrochemical behaviour of ZrO 2 sol–gel films was compared with that of chromatized AA6060 and fluotitanated/fluozirconated AA6060. In order to evaluate the adhesion properties of the films, ZrO 2 pre-treated AA6060, chromatized AA6060 and fluotitanated/fluozirconated AA6060 were painted with a polyester resin and subjected to thermal cycles in 0.05 wt% NaCl. Each thermal cycle consisted of heating the samples at 90 °C, permanence at 90 °C for 6 h, cooling at room temperature and permanence at room temperature for 18 h. Impedance measurements were performed at the end of each cycle. Potentiodynamic polarization curves and impedance spectra indicate that ZrO 2 pre-treatments have similar barrier properties to those of chromatized AA6060. However, no self-healing ability is observed for ZrO 2 films. The barrier properties of ZrO 2 films are strongly dependent on process parameters. In particular, the number of dips determines the amount of defects in the film and its homogeneity. The electrochemical behaviour strongly improves increasing the number of dips in the deposition bath. Thermal aging cycles evidence good adhesion properties for ZrO 2 pre-treatments.

Phase transformation of LiNi 0.75Co 0.25O 2

In this article, the phase transformation of cathode material, LiNi 0.75Co 0.25O 2, prepared by sol–gel pretreatment and solid-phase formation, was studied in detail. The characteristic temperatures associated with the phase transformation of LiNi 0.75Co 0.25O 2 were selected. Accordingly, two series of experiments at different temperatures were performed in situ and ex situ by XRD and SEM to examine the structure and morphology of the material during the phase transformation. It was found that at the temperature below 600 °C a cubic structure was formed and the nickel metal in the material was presented as Ni 2+. A hexangular layer structure started to form when the temperature reached or became higher than 600 °C. The structure became better defined with the increase of temperature. The material was characteristic of R-3 m spatial structure at 725 °C.

Covalent immobilization of GL-7-ACA acylase on silica gel through silanization

GL-7-ACA acylase was covalently immobilized on silica gels modified with 3-aminopropyltriethoxysilane followed sequentially by treatment with glutaraldehyde. The overall immobilization procedure has several steps such as pretreatment of silica gel, modification of carrier surface by silanization, crosslinking by glutaraldehyde and coupling of GL-7-ACA acylase on the silica gel. In this study, each step in the immobilization procedure was optimized individually to improve the efficiency of the overall immobilization procedure of GL-7-ACA acylase. The optimal conditions of each step were determined as follows; pretreatment by 35% hydrogen peroxide, silanization by 10% 3-APTES at pH 9.0 for 120 min, crosslinking by using glutaraldehyde modified under alkaline (pH 8.5) solution at 60 °C for 20 min and coupling in 1.0 M phosphate buffer (pH 8.0). Especially, the adverse effect of glutaraldehyde, which was observed in this study, was reduced by modification of glutaraldehyde. Through the modification of glutaraldehyde, activity of immobilized GL-7-ACA acylase was increased up to about 60% compared to that obtained by using untreated glutaraldehyde. The immobilized GL-7-ACA acylase was tested for long-term stability and it was found that about 70% activity was retained after using it 20 times.

Aluminum Chloride Pretreatment of Elastin Inhibits Elastolysis by Matrix Metalloproteinases and Leads to Inhibition of Elastin-Oriented Calcification

Calcification of elastin occurs in many pathological cardiovascular diseases including atherosclerosis. We have previously shown that purified elastin when subdermally implanted in rats undergoes severe calcification and aluminum chloride (AlCl(3)) pretreatment of elastin inhibits calcification. In the present study we investigated whether matrix metalloproteinase (MMP) binding to elastin and elastin degradation is prevented by AlCl(3) pretreatment. Subdermal implantation of AlCl(3)-pretreated elastin showed significantly lower MMP-9 and MMP-2 activity surrounding the implant as compared to the control implants. AlCl(3) pretreatment also significantly inhibited elastin implant calcification at the seven-day implant period (AlCl(3)-pretreated 4.07 +/- 1.27, control 23.82 +/- 2.24 microg/mg; p<0.0001). Moreover, elastin gel zymography studies showed that gel pretreatment with AlCl(3) inhibited elastolysis by MMP-9. We also demonstrate significant suppression of MMP-2 activity in aortic wall segments of AlCl(3)-pretreated porcine bioprosthetic heart valve implants as compared to control valve implants in sheep mitral valve replacement studies. AlCl(3) pretreatment also significantly inhibited calcification of elastin in this model. Thus, we conclude that aluminum ion binding to elastin prevents MMP-mediated elastolysis and thus prevents elastin calcification.

The cryopreservation of shoot tips of Rosa multiflora

Shoot tips of in vitro grown plantlets of Rosa multiflora were cryopreserved using an encapsulation/dehydration procedure. The influence of sucrose and silica gel pretreatments on pre- and post-freeze shoot growth were examined. Shoot tips recovered from liquid nitrogen only grew after 24h pretreatment in medium containing 0.5 M sucrose, followed by 2 h drying with silica gel and rapid freezing.

Net economic benefit of a manufactured dinoprostone gel for pre-induction cervical ripening.

The purpose of this study was to estimate the net economic cost or benefit of pretreating women who have a medical indication for induction of labour, and an unprepared (unripe) cervix, with a manufactured dinoprostone (prostaglandin E 2) gel. Findings of a meta-analysis of the results of 3 large, randomised clinical trials were employed in the construction of a decision tree used in the economic analysis. For the intended target population, the primary clinical and economic outcomes of gel pretreatment were shortening of the treatment-to-delivery interval, an increase in the percentage of patients achieving labour and a decrease in the percentage of patients requiring delivery by caesarean section. Application of cost factors associated with these and other variables led to a finding of net savings associated with use of the dinoprostone gel pretreatment, compared with no gel pretreatment, of $US159 to $US214 (1993 prices) per treated patient, corresponding to the maximum and minimum duration of the pre-induction treatment period, respectively.

The role of gel chemistry in synthesis of aluminophosphate molecular sieves

The efficiency and product purity of aluminophosphate molecular sieves by the hydrothermal synthesis are affected by the gel chemistry of a reaction mixture. A suitable gel chemistry appears to be a prerequisite for hydrothermally crystallizing the molecular sieves from hydrous gel mixtures. Factors that determine the gel chemistry are the source of aluminum and phosphorus, mixing procedure, gross chemical composition of gel including the water content, and pretreatment of gel. With all these factors specified, the pH of the reaction mixture seems to reflect the gel evolution and crystallization of molecular sieves. Besides the structure-templating effect, organic bases play an important role in determining the gel chemistry. With the addition of organic bases, the pH of the reaction mixture rises to the desirable range of 3.5–6.0. From the properly prepared gel within this pH range, the formation of aluminum phosphate dense phases is eliminated while microporous aluminophosphate is formed as a metastable phase during the hydrothermal crystallization.

Gel permeation chromatography of water-soluble organic matter with deionized water as eluent—I. Examination of the method

The elution behaviour of water-soluble organic substances, from mor organic layers under Norway spruce, in deionized water gel permeation chromatography on Fractogel TSK is examined. Sample or gel pretreatments strongly influence the elution patterns. Various interaction mechanisms control fractionation to different degrees, when cation exchange sites on the gel are occupied by K, Ca or H. Retardation effects, previously attributed to cleavage of macromolecules at low pH, can be explained by alteration of gel properties. Size exclusion plays a minor role. Deionized water GPC provides separation primarily by differences in structural composition.

Influence of silica gel pretreatment and bonding technique on PAH selectivity of octadecyl bonded phases

The effect of silica gel pretreatment and of different bonding techniques, on the chromatographic properties of octadecyl bonded phases is described. The experiments show that a monomeric octadecyl bonded phase, prepared from silica gel that has not been treated before bonding, has a poor selectivity towards polycyclic aromatic hydrocarbons (PAHs) and shows high adsorption of basic components. Silica gel treatment before the bonding of the monofunctional silane does not give a substantial improvement. Polymeric phases on the other hand show a much better PAH selectivity and a lower adsorptivity towards basic components. Further improvement can be achieved with the polymeric modification if silica gel treatment is carried out before bonding.

Protection against alcohol-induced gastric mucosal injury by aluminum-containing compounds--sucralfate, antacids, and aluminum sulfate.

Previously, we demonstrated that both antacids and sucralfate can protect the gastric mucosa against alcohol injury. Since these compounds contain aluminum, we studied whether other aluminum compounds have cytoprotective properties as well. Fasted rats were pretreated intragastrically with A) 0.9% NaCl, B) sucralfate, C) aluminum-magnesium antacid gel, D) Al2(SO4)3, E) Al(OH)3, and 1 h later they received 2 ml 100% ethanol by gavage. The stomach was removed and assessed for injury 3 h after ethanol administration. Control (group A) rats had 39 +/- 3% gross mucosal injury, which was reduced to 5 +/- 1% with sucralfate, 7 +/- 1% with Al2(SO4)3, 12 +/- 2% with Al(OH)3, and 16 +/- 2% with aluminum-magnesium antacid gel pretreatment. Microscopic surface epithelial injury and submucosal edema were seen in all five groups, while deep mucosal necrosis was largely prevented by pretreatment in groups B to E. These findings indicate that aluminum in a wide variety of molecular forms can protect the gastric mucosa against alcohol injury.