A study of the impact of co-adsorbents on DSSC electron transfer processes: anti-π-stacking vs. shield effect.

In this study we report a detailed exploration of the use of two different co-adsorbents - namely bis-methoxyphenylphosphinic acid (BMPP) and chenodeoxycholic acid (CDCA) - known to increase photoconversion efficiency (PCE) of DSSCs sensitized with N719. We have explored the variation of their abilities with the [co-ads]/[D] ratio of the sensitization bath in order to lower the intermolecular deactivations (anti-π-stacking effect) and recombinations between photo-injected electrons and the oxidized mediator (shield effect). EIS-λ technique has been used for this purpose, allowing the two effects considered here to be accurately quantified. DSSC containing BMPP allowed to improve the cell PCE by 60% with a ratio [co-ads]/[D] = 1, exhibiting a strong shield effect, while the maximum PCE obtained with CDCA was slightly over 7% (corresponding to 30% improvement) with a ratio [co-ads]/[D] = 10 and exhibiting a strong anti-π-stacking effect.

Treatment of highly concentrated tannery wastewater using electrocoagulation: Influence of the quality of aluminium used for the electrode.

This paper deals with the ability of electrocoagulation (EC) to remove simultaneously COD and chromium from a real chrome tanning wastewater in a batch stirred electro-coagulation cell provided with two aluminium-based electrodes (aluminium/copper/magnesium alloy and pure aluminium). Effects of operating time, current density and initial concentration of Cr(III) and COD have been investigated. The concentrations of pollutants have been successfully reduced to environmentally acceptable levels even if the concentrated effluent requires a long time of treatment of around 6h with a 400A/m(2) current density. The aluminium alloy was found to be more efficient than pure aluminium for removal of COD and chromium. Dilution of the waste has been tested for treatment: high abatement levels could be obtained with shorter time of treatment and lower current densities. Energy consumption of the electrocoagulation process was also discussed. The dilution by half of the concentrated waste leads to a higher abatement performance of both COD and chromium with the best energy efficiency.

Electrocoagulation of cutting oil emulsions using aluminium plate electrodes.

The treatment of very concentrated oil-water emulsions by electrocoagulation (EC) was experimentally investigated as a pre-treatment step prior to a membrane process. The oil-water emulsion was prepared from a cutting mineral oil B22 currently used for drilling and machining operations. The electrocoagulation progress was followed by the measurement of COD, turbidity and pH in a batch process with recirculation of the liquid. This study is mainly focused on the effects of operating parameters such as initial pH, current density, oil concentration and recirculation rate, on the de-emulsification efficiency. Kinetic curves showed that the EC process exhibits two phases: a "reactive phase" during which the COD and the turbidity removals increase with electrolysis, and a stationary phase for which further aluminium dissolution is useless in the pollution abatement. The results showed that the treatment efficiency increases with increasing current density, but decreases with oil concentration. It appears that treatment of the considered cutting oil is completed through dissolution of around 10mgAl/g oil, with a slight positive effect of the liquid flow rate. Best results are also obtained with initial pH near 7.

Differential distribution of adipokines between serum and synovial fluid in patients with osteoarthritis. Contribution of joint tissues to their articular production.

OBJECTIVE: To analyze the distribution of leptin, adiponectin and resistin between paired serum and synovial fluid (SF) samples of patients with osteoarthritis (OA) and to determine the potential sources of these adipokines in the joint. The active free form of leptin was also examined by evaluating the level of the soluble leptin receptor (sOb-R). METHODS: Levels of adipokines and sOb-R were measured by a sandwich enzyme-linked immunosorbent assay in serum and SF collected from OA patients. The levels of adipokines were also determined in conditioned media from cultured joint tissues (synovium, infrapatellar fat pad, meniscus, osteophyte, cartilage and bone). RESULTS: The adipokines exhibited different patterns of distribution between the joint and the circulating compartment. Serum levels of resistin and adiponectin exceeded those in the paired SF. Conversely, leptin SF concentrations were similar or higher than those measured in serum counterparts. Leptin and adiponectin in SF may derive from each joint tissue examined, whereas resistin was not detected in conditioned media of cultured explants. Synovium and infrapatellar fat pad were the major sources of adipokines, but osteophytes released also large amounts of leptin. The sOb-R deficiency found in SF further increased the difference in the bioactive leptin levels between serum and SF. A gender-specific difference was observed with women exhibiting the highest level of free leptin in the joint. CONCLUSION: These data demonstrated that adipokines serum levels are not predictive values for SF determination. The joint cavity is a special space where each adipokine undergoes specific regulatory pathways, strengthening the hypothesis that adipokines may have local effects in the joint and may account for the high prevalence of OA in women.

Up-regulation of fatty acid metabolizing-enzymes mRNA in rat spinal cord during persistent peripheral local inflammation.

Persistent peripheral inflammation is associated with repetitive painful inputs into the spinal cord, leading to a chronic pain state. Related dramatic changes occur in the central nervous system (CNS) including central sensitization, which results in hyperalgesia. This neural plasticity involves in part fatty acids as functional and structural compounds. We hypothesized that central modification of fatty acids metabolism might occur after prolonged peripheral noxious stimulation. In the present study, the regulation of genes involved in fatty acids metabolism in the rat CNS was investigated during a chronic pain state. Using semiquantitative RT-PCR, we explored in the neuraxis the mRNA expression of brain acyl-CoA synthetases (ACS) and acyl-CoA oxidase (ACO), which are major fatty acid-metabolizing enzymes, following complete Freund's adjuvant (CFA) injection into a hind paw. Similar spinal up-regulation of the isoforms ACS2, ACS3, ACS4, and of ACO was detected early after 30 min, reaching a maximal after 6 h post-injection. Other peaks were also observed after 4 and 21 days post-inoculation, corresponding to the acute and chronic inflammation, respectively. Induction occurred only in the lumbar spinal cord ipsilaterally to the inflamed paw and was completely inhibited by a local anaesthesia of the sciatic nerve, suggesting a neural transmission of the inducing signal. Moreover, intrathecal injection of MK801, a noncompetitive NMDA antagonist, partially prevented these inductions, highlighting the involvement of the neurotransmitter glutamate in the central ACS and ACO up-regulation. These findings suggest that the fatty metabolism is stimulated in the CNS during a chronic pain state.

Articular diffusion of meloxicam after a single oral dose: relationship to cyclo-oxygenase inhibition in synovial cells.

OBJECTIVE: To investigate the distribution of meloxicam in the human knee joint and to compare it with the inhibition of cyclo-oxygenase (COX) activity in synovial cells. DESIGN: Prospective pharmacokinetic study and in vitro laboratory investigation. PATIENTS AND PARTICIPANTS: 42 male and female patients aged 26 to 85 years hospitalised for rheumatic disease and requiring a diagnostic and/or therapeutic knee puncture. METHODS: After a single oral dose of meloxicam 15mg, synovial fluid and blood samples were collected once per patient at various intervals after administration. Meloxicam concentrations were determined by a validated high performance liquid chromatography assay, protein binding by equilibrium dialysis, and pharmacokinetic parameters were calculated by noncompartmental analysis from the mean drug concentration-time profiles. The inhibitory effect of meloxicam on COX activity was investigated separately in unstimulated or interleukin-1beta-stimulated human synovial cells from osteoarthritic patients. RESULTS: Meloxicam was found in synovial fluid at the earliest sampling time (1 hour). Peak concentrations were reached approximately 6 hours postdose in both plasma (842 microg/L) and synovial fluid (320 microg/L). A plateau was observed after the distribution phase (6 hours), corresponding to a constant ratio of drug concentration between synovial fluid and plasma of about 0.47. This ratio was higher in patients with acute inflammation (0.58) than in those with no inflammation (0.38). Meloxicam was extensively bound to protein, mainly to serum albumin. The area under the drug concentration-time curve (AUC) in plasma was more than 2.5 times that in synovial fluid. The AUC for free meloxicam was similar in plasma and synovial fluid. The 50% inhibitory concentrations (IC50) for basal and stimulated COX activity in human synovial cells were 33.7 nmol/L (11.8 microg/L) and 2.0 nmol/L (0.70 microg/L), respectively. The free concentration of meloxicam in synovial fluid was higher than the IC50 for stimulated COX activity from 6 to 36 hours postdose. CONCLUSION: On the basis of free synovial concentrations and the IC50 for stimulated COX activity, meloxicam is expected to have a long duration of action. Inhibition of COX activity is expected to be more marked in inflamed synovium compared with non-inflamed synovium.

High interaction alginate-hyaluronate associations by hyaluronate deacetylation for the preparation of efficient biomaterials.

The paper presents fundamental investigations of alginate-hyaluronate association with significant polymer interactions for preparation of efficient biomaterials. For this purpose, acetamide functions of hyaluronate were partly cleaved by hydrazine at high temperature, yielding amino groups accessible to carboxylic functions of the alginate chain. Alginate-hyaluronate association was studied both in dissolved state by rheological measurements and CD, and in the form of gel slabs prepared after calcium diffusion. Appreciable interaction between carboxylic groups of alginate and the released amino groups of hyaluronate was put into evidence by enhanced values of the viscosity of mixed solutions, and by assessment of the properties of the gel formed: moderate deacetylation allowed gels of improved hardness and viscosity. Nevertheless, high deacetylation was observed to hinder the gel formation by Ca(2+) complexation of alginate, by the significant competition of COOH-NH(2) association. Interaction between alginate and modified hyaluronate results in regular gel structure, with small cavities.

In vitro stereoselective degradation of carprofen glucuronide by human serum albumin. Characterization of sites and reactive amino acids.

Acyl glucuronides formed from carboxylic acids can undergo hydrolysis, acyl migration, and covalent binding to proteins. In buffers at physiological pH, the degradation of acylglucuronide of a chiral NSAID, carprofen, consisted mainly of acyl migration. Acidic pH reduced hydrolysis and acyl migration, thus stabilizing the carprofen acyl glucuronides. Addition of human serum albumin (HSA) led to an increased hydrolysis of the conjugates of both enantiomers. This protein protected R-carprofen glucuronide from migration and therefore improved its overall stability. Hydrolysis was stereoselective in favor of the S conjugate. The protein domains and the amino acid residues likely to be responsible for the hydrolytic activity of HSA were deduced from the results of various investigations: competition with probes specific of binding sites, effects of pH and of chemical modifications of albumin. Dansylsarcosine (DS), a specific ligand of site II of HSA, impaired the hydrolysis, whereas dansylamide (DNSA) and digoxin, which are specific ligands of sites I and III, respectively, had no effect. The extent of hydrolysis by HSA strongly increased with pH, indicating the participation of basic amino acids in this process. The results obtained with chemically modified HSA suggest the major involvement of Tyr and Lys residues in the hydrolysis of glucuronide of S-carprofen, and of other Lys residues for that of its diastereoisomer.

Glycation of human serum albumin by acylglucuronides of nonsteroidal anti-inflammatory drugs of the series of phenylpropionates.

The covalent binding to human serum albumin (HSA), of acylglucuronides from carboxylic nonsteroidal anti-inflammatory drugs (NSAIDs) was investigated. The adduct formation was followed and quantitated by HPLC and by radiometric detection. Three types of albumin adducts were evidenced. The acylglucuronide or the drug itself was bound to 0.2 up to 9% of the albumin molecules, depending on the drug, whereas the majority of adducts (23-49% of albumin molecules) retained the glucuronic acid moiety. The possible involvement of specific Lys located in site I of albumin in the formation of these main adducts was demonstrated, using a series of HSA whose specific Lys residues have been modified chemically. This study shows that acylglucuronides from NSAIDs can significantly contribute to the glycation of proteins, such as albumin.

Human and rat liver UDP-glucuronosyltransferases are targets of ketoprofen acylglucuronide.

Acylglucuronides formed from carboxylic acids by UDP-glucuronosyltransferases (UGTs) are electrophilic metabolites able to covalently bind proteins. In this study, we demonstrate the reactivity of the acylglucuronide from the nonsteroidal anti-inflammatory drug, ketoprofen, toward human and rat liver UGTs. Ketoprofen acylglucuronide irreversibly inhibited the glucuronidation of 1-naphthol and 2-naphthol catalyzed by human liver microsomes or by the recombinant rat liver isoform, UGT2B1, which is the main isoform involved in the glucuronidation of the drug. A decrease of about 35% in the glucuronidation of 2-naphthol was observed when ketoprofen acylglucuronide was produced in situ in cultured V79 cells expressing UGT2B1. Inhibition was always associated with the formation of microsomal protein-ketoprofen adducts. The presence of these covalent adducts within the endoplasmic reticulum of cells expressing UGT2B1 was demonstrated following addition of ketoprofen to culture medium by immunofluorescence microscopy with antiketoprofen antibodies. Immunoblots of liver microsomes incubated with ketoprofen acylglucuronide and probed with antiketoprofen antibodies revealed the presence of several protein adducts; among those was a major immunoreactive protein at 56 kDa, in the range of the apparent molecular mass of UGTs. The adduct formation partially prevented the photoincorporation of the UDP-glucuronic acid (UDP-GlcUA) analog, [beta-32P]5N3UDP-GlcUA, on the UGTs, suggesting that ketoprofen glucuronide covalently reacted with the UDP-GlcUA binding domain. Finally, UGT purification from rat liver microsomes incubated with ketoprofen glucuronide led to the isolation of UGT adducts recognized by both anti-UGT and antiketoprofen antibodies, providing strong evidence that UGTs are targets of this metabolite.

Hyaluronate-alginate gel as a novel biomaterial: mechanical properties and formation mechanism.

With the aim of producing a biomaterial for surgical applications, the alginate-hyaluronate association has been investigated to combine the gel-forming properties of alginate with the healing properties of hyaluronate. Gels were prepared by diffusion of calcium into alginate-hyaluronate mixtures, with an alginate content of 20 mg/mL. The hyaluronate source was shown to have significant effect on the aspect and the properties of the gels. The gels have viscoelastic behaviour and the transient measurements carried out in creep mode could be interpreted through a Kelvin-Voigt generalised model: experimental data led to the steady state hardness and a characteristic viscosity of the gel. Gels prepared from Na rooster comb hyaluronate with weight ratio up to 0.50 have satisfactory mechanical properties, and fully stable gels are obtained after a few days; on the contrary, use of lower molecular weight hyaluronate led to loose gels for hyaluronate contents over 0.25. Gel formation was investigated by measurements of the exchange fluxes between the calcium chloride solution and the forming gel, which allowed thorough investigations of the occuring diffusion phenomena of water, calcium ion and hyaluronate. Strong interactions of water with hyaluronate reduce significantly the rate of weight loss from the gel beads and allows higher water content in steady-state gels. Calcium content in the gel samples could be correlated to the actual alginate concentration, whatever the nature and the weight ratio of hyaluronate.

Hyaluronate-alginate combination for the preparation of new biomaterials: investigation of the behaviour in aqueous solutions.

With the aim of producing a biomaterial for surgical applications, the alginate-hyaluronate association has been investigated. Crossed techniques were used to assess the existence of polymer interactions in aqueous solutions up to 20 mg/ml. Alginate was obtained from algae and hyaluronate was purified from rooster comb. Viscometry measurements using the capillary technique or the Couette flow, together with circular dichroism investigations, evidenced the moderate significance of interactions between the two polysaccharides in dilute solutions. In addition, the case of more concentrated solutions and containing 20 mg/ml alginate was approached by rheological measurements in the flow mode; the behaviour of the polymer associations appeared as a compromise between those of individual polysaccharides.

Separation and quantification by ion-association capillary zone electrophoresis of unsaturated disaccharide units of chondroitin sulfates and oligosaccharides derived from hyaluronan.

An analytical method has been developed for assay of unsaturated disaccharides of chondroitin sulfates and of oligosaccharides (tetra- and hexasaccharides) of hyaluronan, using ion-association capillary zone electrophoresis. Samples were applied at the anode (the usual polarity), using a borate buffer modified by an ion-pairing reagent, tetrabutylammonium (TBA) phosphate, and the effect of the concentration of the ion-pairing reagent on various electrophoretic parameters (electroosmotic flow, electrophoretic mobility of products, capacity factors) was observed. Increasing concentrations of the reagent led to a decrease of zeta potential, probably due to specific adsorption of the quaternary ammonium ion onto the capillary wall. The authors propose a mechanism of separation, in which anionic borate complexes are formed and interact with TBA ion inside the capillary tube. The capillary electrophoretic system described is potentially a powerful method for specific measurement of the concentrations in joint tissues of chondroitin 4-sulfate, chondroitin 6-sulfate, and hyaluronan, whose relative abundances may vary in various diseases or after local treatments with, for example, antiinflammatory drugs, chondroprotective agents, or orthopedic implants.

Effect of dimethicone (polysilane gel) on the stereoselective pharmacokinetics of ketoprofen.

OBJECTIVE: Since dimethicone may be employed to improve gastrointestinal tolerability of non steroidal anti-inflammatory drugs (NSAIDs), we studied its influence on the pharmacokinetics of ketoprofen in subjects receiving a single oral dose of racemic ketoprofen. PATIENTS AND METHODS: In a cross-over experimental design, 12 healthy fasting volunteers were given a single oral dose (100 mg) of racemic ketoprofen, administered with or without dimethicone. The kinetic parameters measured were area under the concentration (AUC), maximum peak plasma concentration (Cmax), time to reach peak concentration (tmax), elimination half-life (t1/2), mean residence time (MRT) and urinary excretion for R and S enantiomers. RESULTS: Dimethicone reduced the peak concentration of both R and S ketoprofen by about 10% (P<0.05) and also induced a slight but non-significant increase in the mean time to achieve peak concentration. However, this treatment had no significant effect on the bioavailability and the elimination of R and S enantiomers, as shown by AUC, t1/2 and MRT values. The absorption patterns were equivalent for both ketoprofen isomers, since plasma pharmacokinetic parameters were similar. Nevertheless, the urinary recovery was significantly lower for R ketoprofen than for its antipode. The administration of dimethicone did not alter this stereoselectivity. CONCLUSION: The administration of dimethicone to alleviate the epigastralgic effects related to NSAIDs does not affect the efficacy of the treatment. Dimethicone did not significantly alter the bioavailability of ketoprofen, chosen as an example of an NSAID, especially that of the pharmacologically active S enantiomer.

Stereoselective irreversible binding of ketoprofen glucuronides to albumin. Characterization of the site and the mechanism.

We have previously shown that the acyl glucuronide of racemic ketoprofen can irreversibly bind in vitro to plasma proteins (Dubois, N., et ai., Drug Metab. Dispos. 21, 617-623, 1993), but the mechanism of the reaction has not been characterized. In the present study, the reactivity toward albumin of the glucuronide of both ketoprofen enantiomers was investigated. The extent of binding increased with the concentration of both protein and glucuronide. However, the two diastereoisomers showed different reactivities toward human serum albumin (HSA): the maximum yield of adducts with the glucuronide of the S-enantiomer was twice that obtained with the glucuronide of its antipode. The maximum extent of irreversible binding was at 4 hr for the R-ketoprofen conjugate, but was later for the S-form. Chemical modifications of albumin indicated that the glucuronide of the S-isomer reacted only with lysine residues, whereas the R-form linked covalently mainly with tyrosine residues and secondarily with lysine residues. A competition study using specific binding probes and fatty acids showed that the conjugates of S- and R-ketoprofen reacted with amino acids located in sites I and II of HSA, respectively. Taken together, these findings suggest that the irreversible binding of ketoprofen to albumin depends on the stereochemistry of the aglycon: the R-enantiomer binds to site II of the protein probably by a nucleophilic attack by tyrosine and/or lysine residues, whereas adduct formation via the conjugate of the S-enantiomer could occur at site I of HSA by the Schiff base mechanism. This irreversible binding at sites I and II may affect the major function of albumin (i.e. the transport of drugs and endogenous compounds).

Influence of severity of chronic inflammatory joint disease on the pharmacokinetics of indomethacin and etodolac.

The goal of this study was to look for correlations between the severity of chronic inflammatory joint disease and pharmacokinetic parameters of nonsteroidal antiinflammatory drugs. Disease severity data (pain severity and magnitude of abnormalities in laboratory tests for inflammation) and pharmacokinetic data (area under the curve in the morning (AUCm) and maximum plasma concentration (Cmax) were collected during a prospective, randomized, double-blind, parallel-group study. Two groups of nine and 11 patients, respectively, were given 300 mg etodolac b.i.d or 50 mg indomethacin b.i.d. by the oral route, for three days, after a 36-hour placebo washout. Univariate analyses demonstrated statistically significant negative correlations between pharmacokinetic parameters of both study drugs and a number of disease severity parameters. In the multivariate analysis of data for etodolac, the sigma erythrocyte sedimentation rate contributed significantly to variations in all pharmacokinetic parameters and explained 100% of the variations in free S-enantiomer AUCm and in total and free S-enantiomer Cmax. For indomethacin, pain contributed to variations in Cmax values of the total and free forms; the sigma erythrocyte sedimentation rate was also a factor in variations in total indomethacin. These negative correlations suggest that severity of chronic inflammatory joint disease may influence the pharmacokinetics of nonsteroidal antiinflammatory drugs.

Stereoselective distribution of tiaprofenic acid in synovium and cartilage in osteoarthritic patients.

OBJECTIVE: In order to document the stereoselective distribution in joints of a chiral nonsteroidal anti-inflammatory drug, the relative affinities of the enantiomers of tiaprofenic acid in synovium and for cartilage were compared. METHODS: The distribution of tiaprofenic acid in synovium and in cartilage was studied 25 h after administering the racemic drug for 2 days (600 mg of a sustained-release preparation, once daily), in 12 inpatients with osteoarthritis of the hip requiring arthroplasty. Enantiomers were quantified in plasma and freeze-ground tissues by a chiral HPLC assay. RESULTS: Plasma concentrations of the dextrorotatory (R) enantiomer (0.40 microgram/ml) were higher than those of its antipode. The concentration of racemate in synovium (in dried and fresh tissues, 150% and 40%, respectively, of the concentration in plasma) was much higher than that in cartilage (in dried tissues 32% of the plasma concentration). The ratio of the active, dextrorotatory (R) enantiomer to its antipode was higher in synovial tissue than in plasma. CONCLUSION: Tiaprofenic acid is distributed stereoselectively in plasma and synovium, which contain a higher concentration of the active, dextrorotatory (R) enantiomer. In cartilage, it reaches only a very low concentration.

Albumin binding sites for etodolac enantiomers.

Non-steroidal anti-inflammatory drugs (NSAIDs) are strongly bound to human serum albumin (HSA), mainly to sites I and II. The aim of this study was to characterize the binding site(s) of etodolac enantiomers under physiological conditions (580 microM HSA) using equilibrium dialysis. The protein binding of etodolac enantiomers, alone or in various ratios, was studied in order to evaluate the potential competition between them. Our results showed that (S)-etodolac was more strongly bound to HSA than (R)-etodolac. The displacement of one enantiomer by its antipode was observed only at high concentrations of the competitor, and was more pronounced for (S)-form. Displacement studies of the enantiomers by specific probes of sites I and II of albumin, dansylamide, and dansylsarcosine, respectively, showed that (R)-etodolac was slightly displaced by both these probes whereas the free concentration of (S)-etodolac increased markedly in the presence of dansylsarcosine. Moreover, the binding of ligands to sites I and II is usually affected by alkaline pH, by chloride ions, and by fatty acids. For etodolac, the presence of 0.1 and 1 M chloride ions and increasing pH (5.5-9) decreased the binding of both enantiomers. The same result was obtained with addition of octanoic acid. Conversely, the addition of oleic, palmitic, or stearic acid to the protein solution increased the binding of (R)-etodolac, but decreased that of its antipode. All these findings suggest (R)- and (S)-etodolac interact mainly with site II of HSA, and that the (R)-isomer is also bound to site I under physiological conditions.

Stereoselective disposition of ibuprofen enantiomers in human cerebrospinal fluid.

Since both (R)- and (S)-enantiomers of ibuprofen may act on the central nervous system, we investigated their plasma and cerebrospinal fluid (CSF) concentrations in 46 patients with nerve-root compression pain requiring a lumbar puncture. Each patient received an oral dose of 800 mg rac-ibuprofen. A single blood and CSF sample was drawn concomitantly from each patient at intervals between 30 min and 8 h after dosing. Both isomers peaked later in the CSF (3 h) than in the plasma (1.5 h). Their CSF concentrations became higher than their concurrent free plasma concentrations after 90 min. The estimated elimination half-lives of (R)- and (S)-ibuprofen were 1.7 h and 2.5 h in plasma and 3.9 h and 7.9 h in CSF, respectively. The AUCCSF/AUCplasma ratios (0, 8 h) were 0.009 and 0.015 for the (R)- and (S)-forms, respectively.