Enhancement of Dissolution Behavior of Aceclofenac by Complexation with β-Cyclodextrin-Choline Dichloride Coprecipitate

The objective of the present investigation was to study the effect of presence of choline dichloride (CDC) in β-cyclodextrin (β-CD) on in vitro dissolution of aceclofenac (AF) from molecular inclusion complexes. The molecular inclusion complexes of AF with β-CD coprecipitated with CDC in 1:1 and 1:2 M ratio were prepared using kneading method. In vitro dissolution of pure drug, physical mixtures, and cyclodextrin inclusion complexes (AF-β-CD-CDC) were carried out. Molecular inclusion complexes of aceclofenac with coprecipitated β-CD showed considerable increase in the dissolution rate in comparison with physical mixture and pure drug in 0.1 N HCl, pH 1.2 and phosphate buffer, pH, 7.4. Inclusion complexes with 1:2 M ratio showed maximum dissolution rate in comparison to other ratios. FTIR spectroscopy and differential scanning calorimetry studies indicated no interaction between AF and β-CD-CDC in complexes in solid state. Dissolution enhancement was attributed to the formation of water soluble inclusion complexes with the precipitated form of β-CD. The in vitro release from all the formulations was best described by first order kinetics (R ² = 0.9354 and 0.9268 in 0.1 N HCl and phosphate buffer, respectively) followed by Higuchi release model (R ² = 0.9029 and 0.9578 in 0.1 N HCl and phosphate buffer, respectively). In conclusion, dissolution of aceclofenac can be enhanced by using the β-CD-CDC coprecipitate as a host molecule.     

Synthesis of pH-responsive mesoporous silica nanotubes for controlled release

A novel mesoporous silica tubes (MMT) which possessed pH-sensitive controlled release ability had been fabricated and synthesized by using carbon nanotubes (CNTs) as template. The sample replicated the morphologies of the CNTs successfully. The Brunauer–Emmett–Teller surface area of the materials can reach 1,017 m² g^?1 with the pore size of 3.8 nm. As a model drug, metformin HCl was applied to study the drug loading and control release ability of the materials. MMT possesses higher drug loading ratio (36 %) than that of MCM-41 (27.5 %). The release kinetics were studied in simulated gastric fluid (pH = 1.2) and in simulated proximal intestine fluid (pH = 7. 4), respectively. The result shows that the delivery systems exhibit well pH-sensitive control release ability and the as-synthesized materials have potential application in biomedical field.     

A new controlled release system of chlorhexidine and chlorhexidine:βcd inclusion compounds based on porous silica

The purpose of this study was to prepare and characterize a controlled release system based on porous silica loaded with chlorhexidine (Cx) and its inclusion compounds in β-cyclodextrin (βcd), and to evaluate its antimicrobial activity. Acetate chlorhexidine (CxA), gluconate chlorhexidine (CxG), βcd:chlorhexidine acetate 2:1 (βcd:CxA) and βcd:chlorhexidine gluconate 2:1 (βcd:CxG) were incorporated into porous silica. Drug loading was characterized by FTIR, powder X-ray diffraction, thermal analysis and BET, and was shown to be in an amorphous state and porous matrix. The kinetics release parameter of the drug was established, which showed that the Cx systems release profile followed zero order release until 400 h and Higuchi model release until 750 h, after the burst effect at the first 8 h. Chlorhexidine therapeutic range was reached near first hour for all systems. The chlorhexidine porous silica system was biologically active against Enterococcus faecalis and Candida albicans in vitro. The systems showed an efficient Cx controlled release modulated by the presence of the β-cyclodextrin and by the porous silica matrices, providing effective antimicrobial activity.     

Silica xerogels as a delivery system for the controlled release of different molecular weight heparins

In this work, we investigated a sol–gel derived silica matrix as a delivery system for the prolonged release of different molecular weight heparins, which allows the glycosaminoglicons to retain their whole biological activity. Several xerogels were obtained by embedding different molecular weight heparins into matrices prepared by using different amount of NH₄OH as a catalyst during gel formation. Gel synthesis parameters, drug release properties, and xerogels surface area were evaluated. Unfractionated, low and oligo-molecular weight heparins were embedded into xerogels and the effect of the molecular weight on the release kinetics and the retained biological activity has been investigated. The results show that the surface area of the matrix is a determinant parameter affecting drug release kinetics. This structural feature can be modified by varying the catalyst tetraethoxysilane molar ratio used during the matrix synthesis. In most cases release kinetics fitted the Higuchi diffusive model and a lower diffusion rate was observed from silica matrices characterized by a smaller surface area. In the case of matrices with lower surface area, loaded with unfractionated heparin, zero order kinetics was observed. In this paper, we have defined a heparin release silica xerogel system and we have pointed out how modulation of its synthesis parameters allows adjusting the release of heparin according to therapeutic needs.     

Sorption of uranium using silica gel with benzoylthiourea derivatives

Benzoylthiourea derivatives (N,N-diphenyl-N′-(3-methylbenzoyl)thiourea and diphenyl-N′-(4-methylbenzoyl)thiourea) were impregnated onto silica gel. The preconcentration of uranium(VI) from aqueous solution was investigated. Extraction conditions were optimized in batch method prior to determination by uv–visible absorption spectrometry using arsenazo(III). The optimum pH for quantitative adsorption was found as 3–7. Quantitative recovery of uranium (VI) was achieved by stripping with 0.1 mol L^?1 HCl. Equilibration time was determined as 30 min for 99% sorption of U(VI). Under optimal conditions, dynamic linear range of for U(VI) was found as 0.25–10 μg mL^?1. The relative standard deviation as percentage and detection limit were 5.0% (n = 10) for 10 μg mL^?1 U(VI) solution and 8.7 ng mL^?1, respectively. The method was employed to the preconcentration of U(VI) ions in soil and tap water samples.     

FAAS determination of palladium after its selective recovery by silica modified with hydrazone derivative

Amino propyl silica (APS) gel reacts immediately with benzyl monopyridyl hydrazone (BMPH) to produce a new effective and selective derivative (BMPH-APS) for the separation and preconcentration of traces of Pd(II) in aqueous solution. Factors affecting the sorption and desorption of Pd ions have been investigated. Acidic aqueous solution of 0.5% thiourea in 0.5 mol L^?1 HCl has been used as eluent for the desorption of Pd(II). The stripped metal ion was determined by flame AAS. The modified silica quantitatively sorbed Pd(II) at pH 2–4 with a sorption capacity of 0.65 mmol g^?1 and preconcentration factor of 250 fold in less than one minute (t_1/2). Common other ions did not interfere except Co(II) which was eliminated by EDTA . The limit of detection (LOD) is 0.1 ng mL^?1 and the relative standard deviation (R. S. D.) for 10 replicate measurements at 20 ng mL^?1 Pd level was 1.51%. The method was successfully applied for Pd preconcentration in highly concentrated salt solutions and in spiked clay, road dust, scrap and water samples.     

Fabrication,characterization and evaluation of bacterial cellulose-based capsule shells for oral drug delivery

Bacterial cellulose (BC) was investigated for the first time for the preparation of capsule shells for immediate and sustained release of drugs. The prepared capsule shells were characterized using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The BC capsule shells were studied for drug release using an USP type-I dissolution apparatus. Irrespective of the drying method and the thickness of the BC sheet, the capsule shells displayed an immediate drug release profile. Moreover, the addition of release-retardant cellulosic polymers sustained the drug release having first-order kinetics for hydroxypropylmethylcellulose and carboxymethyl cellulose sodium with R ² values of 0.9995 and 0.9954, respectively. Furthermore, these capsules shells remained buoyant in 0.1 N HCl (pH 1.2) solution up to 12 h. This study showed that BC is a promising alternative to gelatin capsules with both immediate and sustained drug release properties depending upon the compositions of the encapsulated materials.     

Synthesis of pectin-N,N-dimethyl acrylamide hydrogel by gamma radiation and application in drug delivery (in vitro)

The objective of the work is to synthesize pectin-N, N-Dimethylacrylamide (DMAA) hydrogel by gamma radiation without using any initiators and cross-linking agents. Effect of radiation doses on gel fraction and equilibrium swelling as a function of pH were studied, and 5 kGy radiation dose was found to be the optimum dose for hydrogel synthesis. The grafting /crosslinking was investigated by Fourier transform infrared spectroscopy. Thermal properties and surface morphology were studied by differential scanning calorimetry and scanning electron microscopy. To study the drug release kinetics, 5-fluorouracil was loaded into the hydrogel and in vitro release was carried out in simulated gastric and intestinal fluid. The release profile of drug showed that more than 90% of the loaded drugs were released after 4 hours at both gastric fluid and intestinal fluid pH. Drug release data was fitted into zero order, Higuchi and Korsmeyer-Peppas kinetic models. Higuchi model was found to be the best fitted and release exponent ‘n’ value of Korsmeyer-Peppas model indicated the non-Fickian transport.     

Inhibitive effect by extract of Mentha rotundifolia leaves on the corrosion of steel in 1 M HCl solution

An extract of Mentha rotundifolia leaves (EMRL) was tested as a corrosion inhibitor of steel in 1 M HCl using electrochemical impedance spectroscopy, Tafel polarization methods, and weight loss measurements. The inhibition efficiency of the extract of Mentha rotundifolia leaves was calculated and compared. We note good agreement between these methods. The results obtained revealed that the inhibitor tested differently reduced the kinetics of the corrosion process of steel. Its efficiency increases with the concentration and attained 92.87 % at 35 %. The effect of temperature on the corrosion behavior of steel in 1 M HCl was also studied in the range 298 and 338 K. The thermodynamic data of activation were determined. Mentha rotundifolia extract is adsorbed on the steel surface according to a Langmuir adsorption model.     

pH- and temperature-responsive hydrogels of acrylic acid,N-isopropylacrylamide and a non-ionic surfmer: phase behaviour,swelling properties and drug release

Copolymer hydrogels composed of N-isopropylacrylamide (NIPAM), acrylic acid (AA) and the non-ionic surfactant monomer (surfmer) ω-methoxy poly(ethylene oxide)₄₀undecyl-α-methacrylate (PEO-R-MA-40) were prepared and studied with regard to swelling behaviour and drug release behaviour. The gels were prepared upon γ-irradiation of the corresponding aqueous comonomer solution in a one-step reaction. Transparent, stable hydrogels were obtained. Studies of light transmission indicate a dual pH- and T-responsive behaviour, which originates from the AA and NIPAM content of the gels, respectively. Presence of large amounts of surfmer increases the phase transition temperature, but also increases the network density, which lowers the permeability of the gels. Swelling properties and release of ibuprofen (Ibu) were studied in simulated gastric fluid (SGF, pH 1) and phosphate buffer solution (PBS, pH 6.8). It was found that swelling and release are controlled by the nature and quantity of comonomers, pH, temperature and ionic strength of the aqueous phase. Swollen gels shrink in SGF and PBS, whereas dry gels exhibit a strong swelling both in SGF and PBS. Copolymer gels of AA and surfmer exhibit a strong, linear release of Ibu in SGF and PBS. If NIPAM is copolymerized in the gel, the drug release is decelerated in SGF probably due to formation of hydrogen bonds between NIPAM and Ibu at low pH. For example, a gel composed of 10 % (w/w) NIPAM, 1 % (w/w) AA and 1.5 % (w/w) surfmer exhibits a release of 10 % within 2 h in SGF and 58 % within 20 h in PBS.     

Fluorescence studies of the sol–gel transition in deoxygenated conditions

The results of steady-state and time-resolved fluorescence studies of the sol-gel transition initiated by acidic hydrolysis of silane sols of pH 1.8–5.9 are presented. The gelation process was carried out in an oxygen-free atmosphere using pyrene as a fluorescence probe at concentrations of 1×10 ^-5–1×10 ^-2 M. The silica gels were prepared from sols consisting of tetraethylorthosilicate, ethanol and water in a molar ratio of 1:6:6. The steady-state spectra recorded during gelation allowed the polarity to be determined in the microenvironment of the probe for different pH and pyrene concentration. The investigation of the kinetics of fluorescence decay permitted us to discuss the formation of pyrene aggregates due to variations occurring in the gel net.     

Purification and Characterization of Novel Halo-Acid-Alkali-Thermo-stable Xylanase from Gracilibacillus sp. TSCPVG

An aerobic xylanolytic moderately halophilic and alkali-tolerant bacterium, Gracilibacillus sp. TSCPVG, produces multiple xylanases of unusual halo-acid-alkali-thermo-stable nature. The purification of a major xylanase from TSCPVG culture supernatant was achieved by hydrophobic and gel permeation chromatographic methods followed by electroelution from preparatory PAGE. The molecular mass of the purified xylanase was 42 kDa, as analyzed by SDS-PAGE, with a pI value of 6.1. It exhibited maximal activity in 3.5 % NaCl and retained over 75 % of its activity across the broad salinity range of 0–30 % NaCl, indicating a high halo-tolerance. It showed maximal activity at pH 7.5 and had retained 63 % of its activity at pH 5.0 and 73 % at pH 10.5, signifying the tolerance to broad acid to alkaline conditions. With birchwood xylan as a substrate, K _m and specific activity values were 21 mg/ml and 1,667 U/mg, respectively. It is an endoxylanase that degrades xylan to xylose and xylobiose and had no activity on p-nitrophenyl-β-d-xylopyranoside, p-nitrophenyl-β-d-glucopyranoside, p-nitrophenyl acetate, carboxymethylcellulose, and filter paper. Since it showed remarkable stability over different salinities, broad pH, and temperature ranges, it is promising for application in many industries.     

Validated HPLC and HPTLC Method for Simultaneous Quantitation of Amlodipine Besylate and Olmesartan Medoxomil in Bulk Drug and Formulation

Two methods are described for simultaneous determination of amlodipine besylate and olmesartan medoxomil in formulation. The first method was based on the HPTLC separation of two drugs on Merck HPTLC aluminium sheets of silica gel 60 F₂₅₄ using n-butanol: acetic acid: water (5:1:0.1, v/v/v) as the mobile phase. The second method was based on the HPLC separation of the two drugs on the RP-PerfectSil-100 ODS-3–C₁₈ column from MZ-Analysetechnik GmbH, Germany and acetonitrile/0.03 M ammonium acetate buffer (pH = 3) in a ratio of 55:45 as the mobile phase. Both methods have been applied to formulation without interference of excipients of formulation.     

Fluorescent Dye Conjugates of Rabbit Arylsulfatase A as a Biological Tracer for Protein Endocytosis

Fluorescent dye conjugates of arylsulfatase A (ASA) from rabbit liver were prepared at pH 9.0 in 0.1 M sodium bicarbonate buffer. The modification of amino or sulphadryl groups by dichlorotriazinylamino-fluorescein or Lucifer yellow fluorescent dyes did not alter the characteristic features of the enzyme molecule such as enzyme activity, dimerization of the protein molecule at pH 4.5 and anomalous kinetics of the native enzyme. The fluorescence intensity of the Lucifer yellow enzyme conjugates were quenched when the pH of the protein solution was changed from pH 7.5 to 4.5. Therefore, the Lucifer yellow enzyme conjugate can be used to study the kinetics of pH-dependent association and dissociation of the ASA. Availability of such fluorescent dyes conjugates of ASA or other lysosomal enzyme may be used as a biological tracer to study the receptor dependent endocytosis of enzyme molecules.     

Nano engineered biodegradable capsules for the encapsulation and kinetic release studies of ciprofloxacin hydrochloride

Polyelectrolyte based nano and micro capsules have been extensively studied as promising drug carrier in recent years. Natural degradable capsules have received great deal of attention due to their fascinating structural and morphological characteristics, biocompatibility, sustained and targeted-release capabilities. In this work, chitosan - dextran sulphate nano capsules were prepared via Layer-by-Layer (L-b-L) technique using sacrificial template for drug delivery applications. The loading and in vitro release studies were performed using ciprofloxacin hydrochloride as a model drug. The release media used in the study are plain water and Phosphate Buffered Saline (PBS). The optimum drug load was 389 ​μg, at a loading pH of 2.1 and a temperature of 25 ​°C for 50 ​min encapsulation time. The drug loaded capsules exhibited a slow and sustained release up to 24 ​h and the maximum release rate was obtained at pH 1.2 in water and pH 7.4 in PBS. Least amount of drug release occurred at pH 5.0 in both the release media. The amounts of drug release in water at pH 1.2, pH 5.0 and pH 7.4 are 309 ​μg, 163 ​μg and 251 ​μg respectively where as the corresponding values in the case of PBS (at pH 1.2, pH 5.0 and pH 7.4) are 236 ​μg, 198 ​μg and 251 ​μg respectively. Two different models namely, Ritger - Peppas and Higuchi models were chosen to study the release kinetics behaviour of ciprofloxacin hydrochloride. The prepared bio-degradable capsules had potential as drug carrier for targeting antibacterial drugs with diverse functionality.     

Nitrogen-doped carbon nanotubes modified with gold nanoparticles for simultaneous analysis of N-acetylcysteine and acetaminophen

A novel film consisting of nitrogen-doped multi-walled carbon nanotubes modified with gold nanoparticles (further denoted as N-MWCNTs/AuNPs) was fabricated and applied for the simultaneous electrochemical analysis of N-acetylcysteine (NAC) and acetaminophen (AC) in phosphate buffer solution (PBS, pH 7.0). The fabricated film exhibits powerful response towards simultaneous analysis of NAC and AC followed by well-separated cyclic voltammetric waves (～440 mV). The oxidation peak currents of NAC and AC increase linearly with their concentrations in the ranges of 0.100–1.510 mM and 0.063–0.190 mM, respectively. The detection limits of N-MWCNTs/AuNPs towards NAC and AC were estimated to be 3.0 and 0.35 μM, respectively. The good catalytic activity, the high detection ability, and the great stability of N-MWCNTs/AuNPs verify that such composite materials are extremely promising for the construction of biosensors.     

Exploring Thermophilic Cellulolytic Enzyme Production Potential of Aspergillus fumigatus by the Solid-State Fermentation of Wheat Straw

Cellulases can be used for biofuel production to decrease the fuel crises in the world. Microorganisms cultured on lignocellulosic wastes can be used for the production of cellulolytic enzymes at large scale. In the current study, cellulolytic enzyme production potential of Aspergillus fumigatus was explored and optimized by employing various cultural and nutritional parameters. Maximum endoglucanase production was observed after 72 h at 55 °C, pH 5.5, and 70 % moisture level. Addition of 0.3 % of fructose, peptone, and Tween-80 further enhanced the production of endoglucanase. Maximum purification was achieved with 40 % ammonium sulfate, and it was purified 2.63-fold by gel filtration chromatography. Endoglucanase has 55 °C optimum temperature, 4.8 optimum pH, 3.97 mM K _m, and 8.53 μM/mL/min V _max. Maximum exoglucanase production was observed at 55 °C after 72 h, at pH 5.5, and 70 % moisture level. Further addition of 0.3 % of each of fructose, peptone, and Tween-80 enhances the secretion of endoglucanase. It was purified 3.30-fold in the presence of 40 % ammonium sulfate followed by gel filtration chromatography. Its optimum temperature was 55 °C, optimum pH was 4.8, 4.34 mM K _m, and 7.29 μM/mL/min V _max. In the case of β-glucosidase, maximum activity was observed after 72 h at 55 °C, pH 5.5, and 70 % moisture level. The presence of 0.3 % of fructose, peptone, and Tween-80 in media has beneficial impact on β-glucosidase production. A 4.36-fold purification was achieved by 40 % ammonium sulfate precipitation and gel filtration chromatography. Optimum temperature of β-glucosidase was 55 °C, optimum pH was 4.8, K _m was 4.92 mM, and V _max 6.75 μM/mL/min. It was also observed that fructose is better than glucose, and peptone is better than urea for the growth of A. fumigatus. The K _m and V _max values indicated that endoglucanase, exoglucanase, and β-glucosidase have good affinity for their substrates.     

Solid phase extraction using silica gel functionalized with Sulfasalazine for preconcentration of uranium(VI) ions from water samples

Silica gel surface was chemically functionalized by reaction the silanol from the silica surface with 3-chloropropyltrimethoxysilane followed by reaction with Sulfasalazine. This new sorbent has been used for the preconcentration of low levels of U(VI) ions from an aqueous phase. Parameters involved in extraction efficiency such as pH, weight of the sorbent, volume of sample and eluent were optimized in batch and column methods prior to determination by spectrophotometry using arsenazo(III) reagent. The results showed that U(VI) ions can be sorbed at pH range of 5.0–6.0 in a minicolumn and quantitative recovery of U(VI) (>98.0?±?1.6%) was achieved by stripping with 2.5 mL of 0.1 mol L^?1 HCl. The sorption capacity of the functionalized silica gel was 1.15 mmol g^?1 of U(VI). A linear calibration graph was obtained over the concentration range of 0.02–27.0 μg mL^?1 with a limit of detection of 1 μg L^?1 in treatment with 1000 mL of the U(VI) solution in which the preconcentration factor was as high as 400. The method was employed to the preconcentration of U(VI) ions from spiked ground water and synthetic sea water samples.     

pH-Sensitive Self-Assembled Microspheres Composed of Poly(Ethyleneimine) and Cinnamic Acid

Microspheres which were sensitive to pH change were developed by utilizing cinnamic acid (CA) as a physical cross-linker for poly(ethyleneimine) (PEI). At pH 7.0, the microspheres were efficiently formed at the PEI/CA ratio of 1:3.4, 1:5.1, and 1:7.1 (w/w), which corresponded to the protonated amino group/deprotonated carboxyl group ratio of 5:5, 4:6, and 3:7. The mean diameter of wet microspheres was 3.2 ± 0.3 to 8.8 ± 0.5 μm and that of dry ones was 1.7 ± 0.2 to 2.7 ± 0.2 μm. The microspheres were disappeared upon the alkalification, possibly because the electrostatic interaction between PEI and CA was slackened down and the hydrophobic interaction among CA molecules was weakened. At pH 5.0 and 7.0, the microsphere released its content in a sustained manner and the release degree in 24 h was less than 40%. Whereas, at pH 8.0 and 9.0, the microsphere exhibited a burst release and the release degree in 24 h was greater than 80%. In the alkali condition, not only the electrostatic interaction between PEI and CA but also the hydrophobic interaction among CA molecules became weaker, leading to the disintegration of the microsphere and resulting in a burst and intensive release.     

Slow aggregation and disaggregation of TiO2 nanocrystals in aqueous HCl solutions

The kinetics of slow aggregation and disaggregation of the plate-shaped TiO₂ nanocrystals in aqueous HCl solutions at room temperature was studied using turbidimetry and small-angle X-ray scattering. The rate of slow aggregation of the diluted TiO₂ hydrosols with 0.3 ≤ pH ≤ 3 was compared. The sols with pH about 1 were the most stable and the aggregation rate increased at the decrease of pH from 1 to 0.3 and at the increase of pH from 1 to 3. The reversible loose aggregates slowly formed at the low pH, while the more stable aggregates grew at higher pH.