Lipophilic Gel Research Articles

Preparation of Super-Flexible Silica Aerogel and Its Application in Oil-Water Separation.

Using silica as the precursor, and methyltrimethoxysilane and dimethyldimethoxysilane as the silicon sources, a super-flexible hydrophobic lipophilic gel solid was prepared via hydrolysis, drying, solvent replacement, and atmospheric-pressure drying. The characterization test showed that the sample had good flexibility, hydrophobicity, an amorphous structure, and a hydrophobic contact angle of 137°. Through the adsorption separation experiment, it was concluded that the adsorption separation rate of aerogel to oil substances is related to the viscosity of the oil substances. The hydrophobic and oleophilic properties of flexible silicon aerogel materials can be applied to many aspects, such as crude oil leakage and kitchen waste oil recovery, with broad future development prospects and great research significance.

가지형 가교제를 접목한 VOCs 흡수용 소수성 겔 특성 분석

가지형 가교제를 접목한 VOCs 흡수용 소수성 겔 특성 분석

A radical containing injectable in-situ-oleogel and emulgel for prolonged in-vivo oxygen measurements with CW EPR

Molecular oxygen, reactive oxygen species and free radicals derived from oxygen play important roles in a broad spectrum of physiological and pathological processes. The quantitative measurement of molecular oxygen in tissues by electron paramagnetic resonance (EPR) has great potential for understanding and diagnosing a number of diseases, and for developing and guiding therapies. This requires improvements in the free radical probe systems that sense and report molecular oxygen levels in vivo. We report on the encapsulation of existing free radical probes in lipophilic gel implants: an in-situ-oleogel and an emulgel, based only on well-known, safe excipients for the incorporation of lipophilic and hydrophilic radicals, respectively. The EPR signals of encapsulated radicals were not altered compared to dissolved radicals. The high solubility of oxygen in lipophilic solvents enhanced oxygen sensitivity. The gels extended the lifetime of the radicals in tissues from tens of minutes to many days, simplifying studies with extended series of measurements. The encapsulated radicals showed a good in vivo response to changes in oxygen supply and seem to circumvent concerns from toxicity of the radical probes. These gels simplify the development of new oxygen-sensitive free radical probes for EPR oximetry by making their in vivo stability, persistence and toxicity a function of the encapsulating gel and not a set of additional requirements for the free radical probe.

Where clinical chemistry meets medicinal chemistry. Systematic analysis of physico-chemical properties predicts stability of common used drugs in gel separator serum tubes

BackgroundAs LC–MS/MS techniques are becoming more accessible even outside of highly specialized clinical laboratories, pre-analytical issues such as drug stability during specimen storage should be critically evaluated before implementing therapeutic drug monitoring. Our study investigated the influence of physico-chemical properties of different drugs in regard to their interaction with gel separators used in commercial available collection tubes. MethodsDrug spiked blood samples were analyzed after storage in different commercial gel- and non-gel based serum tubes. LC–ESI–MS/MS based methods were used to determine drug concentration in serum samples. ResultsLipophilic compounds, defined by logP>3 and a compatibility factor>20 are prone to be efficiently and rapidly absorbed by lipophilic gel barriers inducing a significant in-vitro decrease of drug concentration over a short storage time. Our data show a relevant drop of concentration of posaconazole, sertraline and citalopram when stored in gel based tubes. Molecular descriptors such as logP, polar surface area and protein binding seem to be good predictive markers to identify gel interacting drugs. ConclusionFor ease of handling and minimization of blood drawing times, we assume that tubes containing separator gel can be used for therapeutic drug monitoring of high hydrophilic drugs. In contrast lipophilic compounds showing logP higher than 3 and/or CF>20 should be critically considered and validated by extensive stability studies.Abbreviations: logP, partition coefficient; PSA, polar surface area; TDM, therapeutic drug monitoring; ACN, acetonitrile; MeOH, methanol; IVD, in-vitro diagnostic; CF, compatibility factor

Novel approach for the determination of zirconium by solid-phase spectrophotometry

Solid-phase spectrophotometry was used to determine trace amounts of zirconium[IV] in water, soil, plant materials and ore samples. Zr[IV] was sorbed in a dextran-type lipophilic gel as a complex with 2-(2-benzothiazolylazo)-3-hydroxyphenol. The resin-phase absorbance at 569 and 800nm was measured directly, allowing determination of Zr in the range 0.25–3.7μgL−1, with a relative standard deviation of 1.06%. The influence of analytical parameters, including pH, the amounts of 2-(2-benzothiazolylazo)-3-hydroxyphenol and sample volume was investigated. Molar absorptivity was 1.08×105, 6.38×106, and 1.97×107Lmol−1cm−1 at 100, 500 and 1000mL, respectively. The limits of detection and quantification of the 500-mL sample method were 150 and 470ngL−1, respectively, with 40mg dextran-type lipophilic gel. For a 1000-mL sample, the limits of detection and quantification were 80 and 240ngL−1, respectively. Increasing the sample volume enhanced the sensitivity. No significant interference from other anions and cations was observed.

In Vitro Liberation of Indomethacin from Chitosan Gels Containing Microemulsion in Different Dissolution Mediums

The objective of this research is to outline the liberation of indomethacin from different chitosan gels containing O/W microemulsion. The influence of surfactant, sodium lauryl sulfate, in two concentrations (0.5% and 0.75%, w/w) was determined in dissolution medium on the release of indomethacin, which was used as poor water-soluble model drug. Chitosan gels were prepared in four different concentrations of chitosan-1%, 1.5%, 2%, and 3% (w/w). Microemulsion enhanced the liberation of the indomethacin from chitosan gels into all dissolution mediums. Adding the surfactant into phosphate-buffered saline decreased the amount of liberated indomethacin from microemulsion, gel mixture, but increased the drug liberation from pure chitosan gels. It was detected that with the increased concentration of chitosan in the samples, the amount of indomethacin liberated (p < 0.05) also increased. A conclusion was drawn that the liberation of indomethacin from chitosan gels was influenced by increased pH of the samples. The high viscosity induced a higher release of indomethacin from 3% (w/w) chitosan hydrogel at pH 5.8 as compared with 3% (w/w) chitosan hydrogel at pH 3.8. The highest percentage of released indomethacin was determined when a mixture of microemulsion gel with higher chitosan content was used.

Topical application of lipophilic anhydrous gel rich in vitamin E in the management of scars in patients surgically treated for neck cysts

Topical application of lipophilic anhydrous gel rich in vitamin E in the management of scars in patients surgically treated for neck cysts

The useful of topical application of lipophilic anhydrous gel rich in vitamin E

The useful of topical application of lipophilic anhydrous gel rich in vitamin E

Speciation of selenium in environmental samples by solid-phase spectrophotometry using 2,3-dichloro-6-(2,7-dihydroxy-naphthylazo)quinoxaline.

Solid-phase spectrophotometry was applied to determination of trace amounts of selenium (Se) in water, soil, plant materials, human hair, and a cosmetic preparation (lipstick). Se(IV) was sorbed in a dextran type lipophilic gel as a complex with 2,3-dichloro-6-(2,7-dihydroxy-naphthylazo)quinoxaline (DCDHNAQ), whereas Se(VI) was determined after boiling in HCI for 10 min to convert Se(VI) to Se(IV). Resin phase absorbances at 588 and 800 nm were measured directly, which allowed the determination of Se in the range of 0.2-3.3 microg/L with an RSD of 1.22%. The influences of analytical parameters including pH of the aqueous solution, amounts of DCDHNAQ, and sample volume were investigated. The molar absorptivities were found to be 1.09 x 10(6), 4.60 x 10(6), and 1.23 x 10(7) L/mol cm for 100, 500, and 1000 mL, respectively. The LOD and LOQ of the 500 mL sample method were 110 and 360 ng/L, respectively, when using 50 mg dextran type lipophilic gel. For a 1000 mL sample, the LOD and LOQ were 60 and 200 ng/L, respectively, using 50 mg of the exchanger. Increasing the sample volume enhanced the sensitivity. No considerable interferences were observed from other investigated anions and cations on the Se determination.

Compound Allergy to a Lipophilic Gel Containing Vitamin E Acetate and Cyclopentasiloxane

Overview | The leading peer-reviewed scientific journal in contact dermatitis, and the only journal in its field that publishes leading research in atopic, contact, occupational, environmental, and drug dermatitis.

The influence of excipients on physicochemical properties of Miglyol 812 – based oleogels

In this paper, we presented the technology of preparation, as well as quality evaluation methods of the lipophilic gel based on a medium chain triglyceride (MCT) – Miglyol 812. In so doing, glyceryl stearate and glyceryl dibehenate were used as the gelling agents. The compounded gels were analyzed in terms of organoleptic properties, microscopic analysis, and rheological properties (yield point, thixotropy, viscosity at shear rates 10, 100 and 1000 s-1). Following this, two model active substances: hydrocortisone (2%) as the lipophilic one, and oxytetracycline hydrochloride (0,5%) as the hydrophilic one, were incorporated into gels made of Miglyol 812 and 15% glyceryl stearate. After this, the influence of these active substances on the properties of gel was investigated. Moreover, a spectrophotometric method of content evaluation of these substances in a gel was established.

Effect of microemulsion on liberation of indomethacin from hydrophilic and lipophilic gel

Effect of microemulsion on liberation of indomethacin from hydrophilic and lipophilic gelThe paper is focused on liberation of indomethacin from gels and the influence of microemulsion's presence in the system. Liberation of drug was performed in vitro through a semipermeable membrane and drug quantity was determined spectrophotometrically. Our results pointed out that the influence of microemulsion system on drug liberation depends on the gel selection. The presence of o/w microemulsion in the lipophilic gel (aerosil in liquid paraffin) increased the released amount of the drug approximately 50%. The liberation profile of indomethacin is better when the hydrophilic gel (carbopol) was used. Drug was released in higher amounts from hydrophilic gel comparised to the commercial gel. The presence of microemulsion in carbopol gel did not have any significant influence.

Semisolid formulations containing dimethyl sulfoxide and α-tocopherol for the treatment of extravasation of antiblastic agents

The topical treatment with dimethyl sulfoxide (DMSO) and/or alpha-tocopherol (alpha-T) is widely used in order to prevent the local complications of extravasation of cytostatic drugs and protect patients against skin ulceration. Till now, DMSO and alpha-T have been mainly used in solution. The goal of this study was to formulate semisolid preparations for cutaneous application differing in the hydrophilic and lipophilic properties and containing DMSO and alpha-T in combination. With respect to solutions, the use of semisolid preparations containing DMSO and alpha-T could be advantageous in patients having extravasation as DMSO and alpha-T can remain in contact with the skin over an extended period of time. As a consequence, the action of the active principles can be limited specifically on the injured skin area, reducing the cutaneous irritative effects of DMSO. The following types of semisolid formulations containing 50% m/m DMSO and 2.5% m/m alpha-T were prepared: hydrophilic ointment, o/w emulsion, hydrophilic gel and lipophilic gel. The ex vivo skin permeation of DMSO and alpha-T was evaluated by using modified Franz's diffusion cells and human stratum corneum and epidermis (SCE) as a membrane. The permeated and retained amounts of DMSO and alpha-T were determined. The oleogel preparation, the hydrophilic gel and the o/w emulsion were uniform in colour and aspect, without any evidences of phase separation over the period of the study. Hydrophilic ointments were discarded as they showed phase separation after 12 h. All formulations had a different behaviour in terms of skin permeability. In particular, hydrogel and o/w emulsion showed the best control on the drug release considering the interactions of the vehicle components with the SCE and the drugs partition between the vehicle and the SCE. The DMSO permeated amount after 24 h was 4.1 mg/cm(2) for hydrogel and 2.5 mg/cm(2) for emulsion while the permeated amount of pure DMSO after 24 h was 47.5 mg/cm(2). Therefore, aiming to reduce side effects after the topical application of the antidotes DMSO and alpha-T, these results suggested that hydrogel and o/w emulsion could be considered the most promising formulations for further clinical evaluations in managing of extravasation of anthracyclines.

Colloidal microstructure of binary systems and model creams stabilized with an alkylpolyglucoside non-ionic emulsifier

The aim of this study was to examine the lyotropic potential of an alkylpolyglucoside mixed emulsifier (Cetearyl glucoside&Cetearyl alcohol), which belongs to the new generation of natural (sugar) surfactants, and to elaborate the potential stabilization mechanism and relation between the colloid microstructure and water distribution within the systems. Polarization and ordinary light as well as transmission electron microscopy, wide and small-angle X-ray diffraction, thermal analysis and rheological measurement were employed for the systems characterization. It was suggested that Cetearyl glucoside&Cetearyl alcohol stabilizes the o/w creams by synergistic effects of viscoelastic hydrophilic gel of lamellar type and lipophilic gel network built up from cetostearyl alcohol semi-hydrates as well as by lamellar liquid crystalline bilayers surrounding the oil droplets. The hydrophilic gel consists of mixed cetearyl glucoside/cetearyl alcohol crystalline bilayers entrapping the water interlamellarly by hydrogen bonding. It is also showed that oil addition into the chosen binary system influences the creams microstructure significantly, which particularly reflects onto the mode of water distribution within the creams and consequently their potential of skin hydration.

Determination of tocopherols, tocopherolquinones and tocopherolhydroquinones by gas chromatography–mass spectrometry and preseparation with lipophilic gel chromatography

Lipophilic gel chromatography using Sephadex LH-20 helps in separating α-, β-+γ-, and δ-tocopherol and also in separation of their oxidation products e.g. the tocopherolquinones or other oxidation products. This preseparation can help to overcome analytical problems due to the complexity of synthesis mixtures of tocopherol oxidation procedures as well as in separation of complex physiological matrices. Determination of the preseparated tocopherols, tocopherolquinones and tocopherolhydroquinones can then be achieved by means of GC–MS measurement of the free substances or their trimethylsilyl derivatives.

Biotransformation of cyclizine in greyhounds. 2: N 1 -dealkylation and identification of some neutral and phenolic metabolites in canine urine by gas chromatography-mass spectrometry

1. The in vivo enzymatic Phase I biotransformation of cyclizine (Marezine ®) in the racing greyhound has been shown to proceed via several different pathways. Aromatic and heterocyclic oxidation and the N 4 -demethylation of cyclizine lead to the formation of unconjugated and conjugated (Phase II) basic metabolites excreted in canine urine. 2. Enzymatic N 1 -dealkylation of cyclizine and its basic metabolites leads to the formation of the neutral and phenolic Phase I metabolites containing the diphenylmethane/methylene substructures. Further, Phase I metabolism of the neutral metabolites could also lead to the formation of several secondary phenolic products. These neutral and phenolic compounds are then excreted as unconjugated and Phase II conjugates in greyhound urine. 3. Following enzymatic deconjugation of selected post-Marezine administration urine samples from two greyhounds, the total aglycones were extracted and separated into neutral/acidic and basic fractions using copolymeric mixed-mode solid-phase extraction cartridges. 4. The neutral/acid isolates were further separated into neutral and phenolic fractions by column chromatography on a lipophilic strong anion-exchanger gel, triethylaminohydroxypropyl Sephadex LH-20 in OH - form. 5. The individual neutral and phenolic fractions obtained from the acid/neutral isolate were derivatized as trimethylsilyl ethers and analysed by positive-ion electron ionization gas chromatography-mass spectrometry (EI + -GC-MS). 6. Three compounds, diphenylmethane (M1), benzophenone (or diphenyl ketone, M2) and benzhydrol (M3), were identified in the neutral isolates by comparison of their EI + mass spectra with authentic standards. At least seven secondary compounds containing the functionalized diphenylmethylene substructure were detected in the phenolic isolates. As no authentic compounds are available, the structures of these putative metabolites (M4 → M10) were elucidated from an interpretation of the EI + -GC-mass spectra of their TMS derivatives.

Contraceptive efficacy and safety studies of a novel microemulsion-based lipophilic vaginal spermicide

Objective: To investigate the in vivo contraceptive potency and safety of a novel microemulsion-based lipophilic vaginal spermicide. Design: In vitro and in vivo spermicidal activity and safety of a submicron-particle-size, lipophilic gel–microemulsion (GM-4). Setting: Center for Advanced Preclinical Sciences at the Parker Hughes Institute. Patient(s): Nine male volunteer sperm donors. Intervention(s): Motile human sperm in semen and medium were exposed to eight GM-4 components or GM-4 formulation. Forty-eight ovulated NZW rabbits in subgroups of 16 with or without intravaginal administration of GM-4 or nonoxynol-9 gel (N-9; Gynol II) were artificially inseminated and allowed to complete pregnancy. Eleven rabbits were exposed to daily intravaginal application of GM-4 with and without N-9 for 10 consecutive days. Ten of 20 B 6C 3F 1 mice were given repetitive intravaginal application of GM-4 for 5 days/week over 13 consecutive weeks. Main Outcome Measure(s): The motility of human sperm treated with GM-4 components and GM-4. Term pregnancy in rabbits and histopathological grading of rabbit vaginal tissue for irritation. Evaluation of mice for survival, growth, hematologic parameters, blood-chemistry profiles, absolute and relative organ weights, and histopathology. Result(s): The individual components of GM-4 lacked spermicidal activity in human semen, whereas the GM-4 formulation containing all the eight pharmacological excipients exhibited potent spermicidal activity with rapid kinetics. GM-4 showed remarkable contraceptive activity in the rigorous rabbit model. None of the 16 (0%) rabbits given GM-4 intravaginally before artificial insemination became pregnant. By contrast, 15 of 16 (93.7%) control rabbits and 5 of 16 (31.2%) Gynol II-treated rabbits became pregnant and delivered newborns. Thus, GM-4 was a significantly more effective contraceptive than a commercially available N-9 gel [100% vs. 68.7% protection; P< 0.05, Fisher’s exact test]. Unlike the rabbits treated with N-9, none of the rabbits that were given GM-4 intravaginally for 10 consecutive days developed epithelial ulceration, edema, leukocyte influx, or vascular congestion characteristic of inflammation. Furthermore, repeated intravaginal application of GM-4 for up to 13 weeks in mice had no adverse effects on survival, growth, metabolism, or organ function. Conclusion: We conclude that the novel spermicidal GM-4 formulation is safe and significantly more effective than N-9 in preventing conception.

ANALYSIS OF POLYBROMINATED DIPHENYL ETHERS IN SWEDISH HUMAN MILK. A TIME-RELATED TREND STUDY, 1972-1997

A previously described method for analysis of organochlorine compounds in human milk was adopted for analysis of brominated diphenyl ethers ( BDEs) substituted with three to six bromine atom s. Analytes were extracted from hum an milk with the lipophilic gel Lipidex 5000. Further purifications were performed on partly deactivated aluminum oxide and silica gel columns, followed by gel permeation chromatography. The concentrations of BDEs were determined by gas chromatography/mass spectrometry (GC/MS). The average recoveries of 2,2',4-triBDE (BDE-17), 2,4,4'-triBDE (BDE28) , 2,2',4,4'-tetraBDE (BDE-47), 2,3',4,4'-tetraBDE (BDE-66), 2,2',3,4,4'-pentaBDE (BDE-8 5) , 2,2',4,4',5-p entaBDE (BDE-99), 2,2',4,4',6-pentaBDE (BDE-100) , 2,2',4,4',5,5'-hexaBDE (BDE-153), and 2,2',4,4',5,6'-hexaBDE (BDE-154) added to the samples before extraction ranged from 86% to 102% . Pooled samples of breast milk, collected at eight time periods between 1972 and 1997, were analyzed for PBDEs. BDE-47 was the most abundant PBDE congener in all samples. In total, eight PBDE congeners were identified in the milk. The sum of the concentrations of BDE congeners in human milk increased from 0.07 to 4.02 ng/g lipids during the 25-yr period studied.

Speciation of selenium (IV) in natural waters by solid phase spectrophotometry

A method for the speciation of selenium (IV) based on solid-phase spectrophotometry (SPS), has been developed. In acidic conditions selenium (IV) oxidizes potassium iodide and the I 3 − forms an ionic association with Rhodamine B (RB) which is fixed on a dextran type lipophilic gel. The gel phase absorbances at 590 and 800 nm are measured directly, and allows for the determination of selenium (IV) in the range of 0.7–18.0 μg l −1, with a relative standard deviation (RSD) of 2.8%. The method has been applied to the determination of Se(IV) in natural waters.

Preclinical studies on thiocarboxanilide UC-781 as a virucidal agent.

Thiocarboxanilide UC-781 is a highly potent and selective non-nucleoside reverse transcriptase inhibitor (NNRTI) of HIV-1, which also has virucidal properties. Recent studies have shown that UC-781 would seem an ideal candidate for application as a vaginal virucide. To investigate the antiviral potency and stability of UC-781 in a lipophilic gel formulation. UC-781 was formulated in replens gel at different concentrations and administered intravaginally to rabbits at 5% in replens gel for 10 days. UC-781 was also exposed to temperatures of 4, 37 and 50 degrees C, and to low pH (6.0, 4.3, 2.0 and 1.2). A number of microorganisms were exposed in culture to serial dilutions of UC-781. The drug was stable under low pH conditions and did not lose its antiviral potency upon 4 h exposure to pH 3.5 (the estimated vaginal pH). UC-781 can be easily formulated into a lipophilic gel (replens; up to 5%) and proved fully stable at 50 degrees C for 30 days. There was no effect on the growth of microorganisms (i.e., Candida and Lactobacillus strains) that are present in the vaginal flora. Neither systemic side-effects, nor local inflammation or damage of the vaginal mucosa or epithelium were observed in rabbits to which 5% UC-781 in replens gel had been administered. UC-781, formulated as 0.5, 0.2 and 0.05% replens gel, and UC-38, alpha-APA and zidovudine, formulated as 0.5 or 0.2% replens gel, were effective in protecting CEM cells in the very beginning against productive HIV-1 replication. This points to an efficient diffusion of the drugs from the lipophilic gel to the hydrophilic culture medium. However, subsequent subcultivations at a dilution rate of 1:10 every 3-4 days resulted in a rapid breakthrough of virus with all drugs except UC-781 in its 0.5 and 0.2% gel formulation. These cultures were fully protected against HIV-1 and remained completely cleared from virus for at least 10 subcultivations. The virus that emerged under 0.05% UC-781 remained highly sensitive to the NNRTI, including UC-781, in cell culture, suggesting a lack of resistance development under our experimental conditions.