Characterization and performance of injection molded poly(methylmethacrylate) microchips for capillary electrophoresis

Injection molded poly(methylmethacrylate) (IM-PMMA), chips were evaluated as potential candidates for capillary electrophoresis disposable chip applications. Mass production and usage of plastic microchips depends on chip-to-chip reproducibility and on analysis accuracy. Several important properties of IM-PMMA chips were considered: fabrication quality evaluated by environmental scanning electron microscope imaging, surface quality measurements, selected thermal/electrical properties as indicated by measurement of the current versus applied voltage (I-V) characteristic and the influence of channel surface treatments. Electroosmotic flow was also evaluated for untreated and O2 reactive ion etching (RIE) treated surface microchips. The performance characteristics of single lane plastic microchip capillary electrophoresis (MCE) separations were evaluated using a mixture of two dyes-fluorescein (FL) and fluorescein isothiocyanate (FITC). To overcome non-wettability of the native IM-PMMA surface, a modifier, polyethylene oxide was added to the buffer as a dynamic coating. Chip performance reproducibility was studied for chips with and without surface modification via the process of RIE with O2 and by varying the hole position for the reservoir in the cover plate or on the pattern side of the chip. Additionally, the importance of reconditioning steps to achieve optimal performance reproducibility was also examined. It was found that more reproducible quantitative results were obtained when normalized values of migration time, peak area and peak height of FL and FITC were used instead of actual measured parameters.

Quantitative imaging of proteoglycan in cartilage using a gadolinium probe and microCT

OBJECTIVE

Micro-computed tomography (microCT) imaging has the potential to allow the three-dimensional (3D) visualization of cartilage morphology. However, cartilage intensity on a microCT image is weak because cartilage does not strongly attenuate X-rays. This work was designed to demonstrate that exposure of cartilage to charged gadolinium compounds modifies the intensity to allow an improved visualization of cartilage morphology and the determination of proteoglycan content.

DESIGN

Trypsin was used to deplete proteoglycan in bovine nasal cartilage disks. Disks were then exposed to Gd(3+), gadopentetate (Gd-DTPA(2-)), or gadoteridol (Gd-HP-DO3A), and imaged with microCT. The intensities of the disks were measured from the images and compared to the actual proteoglycan content determined with a dimethylmethylene blue assay.

RESULTS

Treatment of naïve disks with 200 mM Gd(3+) for 24h at room temperature produced a 2.8-fold increase in intensity on microCT images. Similar treatment with 200 mM Gd-DTPA(2-) produced a 1.4-fold increase. After 2h of trypsin treatment at room temperature, the intensities of cartilage disks exposed to 20 0mM Gd(3+) decreased by 12%. Conversely, the intensities of trypsin-treated disks exposed to 200 mM Gd-DPTA(2-) increased by 15%. Trypsin treatment caused a 4% increase in the intensities of disks exposed to neutral Gd-HP-DO3A. The correlation between proteoglycan content and the microCT intensity of cartilage treated with Gd(3+) was very good (r(2)=0.81).

CONCLUSIONS

Gadolinium and microCT allow an improved 3D visualization of cartilage and quantification of its proteoglycan content.

Fluorogenic assay for beta-glucuronidase using microchip-based capillary electrophoresis

Microchip capillary electrophoresis (CE) was used with a model enzyme assay to demonstrate its potential application to combinatorial drug screening. Hydrolysis with beta-glucuronidase of the conjugated glucuronide, fluorescein mono-beta-D-glucuronide (FMG), liberated the fluorescent product, fluorescein. FMG and fluorescein were detected by fluorescence, with excitation and emission at 480 and 520 nm, respectively. Microchip CE was used to separate FMG and fluorescein. Fluorescein production was monitored to assess beta-glucuronidase activity. Michaelis-Menten enzyme kinetics analysis yielded the Km value. The results were compared with those from experiments done by conventional CE. The Km value for beta-glucuronidase with FMG is being reported for the first time as 18 microM. The inhibition of beta-glucuronidase by the competitive inhibitor D-saccharic acid-1,4-lactone (SL) was also determined using microchip CE. Reactions were done with various concentrations of inhibitor and constant beta-glucuronidase and FMG concentrations. A dose-response plot was acquired and the IC50 value for SL was determined to be 3 microM.

Increasing bioanalytical throughput using pcSFC-MS/MS: 10 minutes per 96-well plate

The utility of packed-column supercritical, subcritical, and enhanced fluidity liquid chromatographies (pcSFC) for high-throughput applications has increased during the past few years. In contrast to traditional reversed-phase liquid chromatography, the addition of a volatile component to the mobile phase, such as CO2, produces a lower mobile-phase viscosity. This allows the use of higher flow rates which can translate into faster analysis times. In addition, the resulting mobile phase is considerably more volatile than the aqueous-based mobile phases that are typically used with LC-MS, allowing the entire effluent to be directed into the MS interface. High-throughput bioanalytical quantitation using pcSFC-MS/MS for pharmacokinetics applications is demonstrated in this report using dextromethorphan as a model compound. Plasma samples were prepared by automated liquid/liquid extraction in the 96-well format prior to pcSFC-MS/MS analysis. Three days of validation data are provided along with study sample data from a patient dosed with commercially available Vicks 44. Using pcSFC and MS/MS, dextromethorphan was quantified in 96-well plates at a rate of approximately 10 min/plate with average intraday accuracy of 9% or better. Daily relative standard deviations (RSDs) were less than 10% for the 2.21 and 14.8 ng/mL quality control (QC) samples, while the RSDs were less than 15% at the 0.554 ng/mL QC level.

Semi-automated 96-well solid-phase extraction and gas chromatography-negative chemical ionization tandem mass spectrometry for the trace analysis of fluprostenol in rat plasma

Semi-automated 96-well plate solid-phase extraction (SPE) was used for sample preparation of fluprostenol, a prostaglandin analog, in rat plasma prior to detection by gas chromatography-negative chemical ionization tandem mass spectrometry (GC-NCI-MS-MS). A liquid handling system was utilized for all aspects of sample handling prior to SPE including transferring of samples into a 96-well format, preparation of standards as well as addition of internal standard to standards, quality control samples and study samples. SPE was performed in a 96-well plate format using octadecylsilane packing and the effluent from the SPE was dried in a custom-made 96-well apparatus. The sample residue was derivatized sequentially with pentafluorobenzylbromide followed by N-methyl-N-trimethylsilyltrifluoroacetamide. The derivatized sample was then analyzed using GC-NCI-MS-MS. The dynamic range for the method was from 7 to 5800 pg/ml with a 0.1-ml plasma sample. The methodology was evaluated over a 4-day period and demonstrated an accuracy of 90-106% with a precision of 2.4-12.9%.

Use of short high-performance liquid chromatography columns and tandem-mass spectrometry for the rapid analysis of a prostaglandin analog, fluprostenol, in rat plasma

A short reversed-phase HPLC column and a tandem mass spectrometer were used to develop a stable-isotope-dilution assay for the rapid and sensitive analysis of fluprostenol, a prostaglandin analog, in rat plasma. A Waters Symmetry ODS column (2.1x10 mm) afforded rapid isocratic elution of fluprostenol (t(R)=40 s) but still provided a relatively large k' value of 4. The use of tandem mass spectrometry allowed the interference-free detection of fluprostenol under the rapid elution conditions, with a limit of quantitation of 25 pg ml(-1) fluprostenol, using 0.2 ml plasma sample volumes. The method was linear over three orders of magnitude, yielded accurate and precise results and allowed the pharmacokinetic profile of fluprostenol to be defined following intravenous administration in rats.

Determination of norepinephrine in small volume plasma samples by stable-isotope dilution gas chromatography-tandem mass spectrometry with negative ion chemical ionization

A stable-isotope based gas chromatography-tandem mass spectrometry-negative ion chemical ionization method was developed for the determination of norepinephrine (NE) levels in small volumes (25-100 microl) of plasma. NE was stabilized in plasma by the addition of semicarbazide and spiked with deuterium-labeled norepinephrine internal standard. The analytes were isolated from the plasma by solid-phase extraction using phenylboronic acid columns and derivatized using pentafluoropropionic anhydride. The derivatized analytes were chromatographed on a capillary column and detected by tandem mass spectrometry with negative ion chemical ionization. Unparalleled sensitivity and selectivity were obtained using this detection scheme, allowing the unambiguous analysis of trace levels of NE in small-volume plasma samples. Linear standard curves were obtained for NE over a mass range from 1 to 200 pg per sample. The method had a limit of quantitation of 10 pg NE/ml plasma when using a 100-microl sample aliquot (1 pg/sample). Accuracy for the analysis of plasma samples spiked with 10 to 200 pg NE/ml typically ranged from 100+/-10%, with RSD values of less than 10%. The methodology was applied to determine the effect of clonidine on plasma NE levels in conscious spontaneously hypertensive rats. Administration of clonidine (30 microg/kg) produced an approximately 80% reduction in plasma NE accompanied by a 30% reduction in heart and mean arterial pressure that persisted >90 min after drug administration. The ability to take multiple samples from individual rats allowed the time course for the effect of clonidine to be mapped out using only one group of animals.

Gas chromatographic-mass spectrometric analysis of hydroxylamine for monitoring the metabolic hydrolysis of metalloprotease inhibitors in rat and human liver microsomes

A gas chromatographic-mass spectrometric (GC-MS) method was developed for the analysis of hydroxylamine (HA) in supernatants obtained from liver microsomes. HA monitoring was used to determine the metabolic hydrolysis of two hydroxamic acid-based matrix metalloprotease inhibitors in rat and human liver microsomes. The hydrolysis of the hydroxamic acids to their corresponding carboxylic acids releases HA as a common metabolic product. HA was derivatized to acetone oxime by addition of acetone to the liver microsomal supernatant, followed by direct injection of the supernatant into the GC-MS, with detection of the oxime by selected-ion-monitoring. The method is simple, reproducible, and sensitive for the determination of the hydrolysis of hydroxamic acid compounds, where hydrolysis is the major metabolic pathway. The methodology can be used for rank ordering and selecting hydroxamic acid analogs based on their susceptibility to hydrolysis.

New cyclooxygenase-2/5-lipoxygenase inhibitors. 3. 7-tert-butyl-2, 3-dihydro-3,3-dimethylbenzofuran derivatives as gastrointestinal safe antiinflammatory and analgesic agents: variations at the 5 position

We report an expansion of the scope of our initial discovery that 5-keto-substituted 7-tert-butyl-2,3-dihydro-3,3-dimethylbenzofurans (DHDMBFs) are antiinflammatory and analgesic agents. Several other functional groups have been introduced at the 5 position: amides, amidines, ureas, guanidines, amines, heterocycles, heteroaromatics, and heteroaryl ethenyl substituents in the 5 position all provide active compounds. These compounds are dual cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) inhibitors. They inhibit both COX-1 and COX-2 with up to 33-fold selectivity for COX-2.

Comparison of p-fluoroketorolac and [18O3]ketorolac for use as internal standards for the determination of ketorolac by gas chromatography/mass spectrometry (GC/MS)

A chemical and a stable-isotope analog, p-fluoroketorolac and [18O3]ketorolac respectively, were directly compared for applicability as internal standards for the determination of ketorolac in plasma samples using gas chromatography/mass spectrometry (GC/MS) with selective-ion-monitoring detection, following derivatization to form the methyl esters. This comparison involved analyzing ketorolac calibration standards and spiked plasma samples that contained both internal standard candidates. The response for ketorolac and each internal standard was monitored simultaneously and electronically integrated peak heights were obtained. Thus, for each analysis performed, a response ratio was obtained for each internal standard relative to an identical ketorolac response. Linearity of response for ketorolac calibration standards and accuracy for spiked plasma sample analysis were compared using each internal standard. The use of [18O3]ketorolac as the internal standard provided superior accuracy data for the analysis of ketorolac in plasma samples.

New cyclooxygenase-2/5-lipoxygenase inhibitors. 1. 7-tert-buty1-2,3-dihydro-3,3-dimethylbenzofuran derivatives as gastrointestinal safe antiinflammatory and analgesic agents: discovery and variation of the 5-keto substituent

A series of 5-keto-substituted 7-tert-buty1-2,3-dihydro-3,3- dimethylbenzofurans (DHDMBFs) were prepared and evaluated as potential nonsteroidal antiinflammatory and analgesic agents. Interest in this class of compounds arose when a DHDMBF was found to be an active metabolite of the di-tert-butylphenol antiinflammatory agent tebufelone. We have now found that a variety of 5-keto-substituted DHDMBFs have good in vivo antiinflammatory and analgesic activity after oral administration. These compounds inhibit both cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) in vitro. The cyclooxygenase inhibition was found to be selective for the cyclooxygenase-2 isoform, and this combination of COX-2/5-LOX inhibition may be responsible for the gastrointestinal safety of compounds such as 30.

New cyclooxygenase-2/5-lipoxygenase inhibitors. 2. 7-tert-butyl-2,3-dihydro-3,3-dimethylbenzofuran derivatives as gastrointestinal safe antiinflammatory and analgesic agents: variations of the dihydrobenzofuran ring

A series of 5-keto-substituted 7-tert-buty1-2,3-dihydro-3,3- dimethylbenzofurans (DHDMBFs) were found to be nonsteroidal antiinflammatory and analgesic agents. These compounds are inhibitors of 5-lipoxygenase (5-LOX) and cyclooxygenase (COX) with selectivity for the COX-2 isoform. A series of analogues were prepared to investigate the scope of this lead. Five ketone side chains from active DHDMBFs were used to investigate the effects of changes in the DHDMBF "core": the size and identity of the heterocycle and the substituent requirements of the heterocycle and phenyl ring. Biological testing showed that a variety of structural changes can be accommodated, but no structure was clearly superior to the DHDMBF structure.

Isolation and quantification of fluoroacetate in rat tissues, following dosing of Z-Phe-Ala-CH2-F, a peptidyl fluoromethyl ketone protease inhibitor

Peptidyl fluoromethyl ketones (PFMK) are irreversible inhibitors of cathepsin B, a cysteine proteinase thought to be involved in the degradation of cartilage. It has been speculated that PFMK inhibitors may metabolize in rodents to form fluoroacetate (FAC), an extremely toxic poison. A highly selective and sensitive separation and detection scheme was developed to measure trace levels of FAC in rat tissues following PFMK dosing. The procedure consisted of extracting FAC from tissue and spiking the extract with [18O]2-fluoroacetate (18O-FAC) as an internal standard. FAC and 18O-FAC were further isolated from matrix components using ion-exchange, solid-phase extraction. The pentafluorobenzyl esters of FAC and 18O-FAC were formed to facilitate the chromatographic separation. Two-dimensional gas chromatography coupled with selected-ion-monitoring detection provided the final measurement. The assay had a limit of detection of 2 ng FAC per g tissue, and was capable of accurately quantitating as little as 10 ng FAC per g tissue with a S/N ratio of 40:1. Linearity was established over two orders of magnitude, from 2-500 ng ml-1, with 5 microliters injected on-column. The method was used to demonstrate that FAC was formed in rats following dosing with Z-Phe-Ala-CH2-F, a PFMK cathepsin enzyme inhibitor.

Determination of dextromethorphan and dextrorphan in human plasma by liquid chromatography/tandem mass spectrometry

Rapid, sensitive and selective methods were developed for the determination of dextromethorphan and its major metabolite, dextrorphan, in human plasma using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Plasma samples spiked with stable-isotope internal standards were prepared for analysis by a liquid-liquid back-extraction procedure. Dextromethorphan and dextrorphan were chromatographed on a short reversed-phase column, using separate isocratic mobile phase conditions optimized to elute each compound in approximately 1.1 min. For both analytes, calibration curves were obtained over four orders of magnitude and the limit of quantitation was 5 pg ml-1 using a 1 ml plasma sample volume. The accuracy across the entire range of spiked DEX and DOR concentrations was, in general, within 10% of the spiked value. The precision was generally better than 6% for replicate sample preparations at levels of 50 pg ml-1 or higher and typically better than 12% at levels below 50 pg ml-1. The method was applied for the evaluation of the pharmacokinetic profiles of dextromethorphan and dextrorphan in a human volunteer following peroral administration of a commercially available cough formulation.

Analysis of a novel antiinflammatory agent, 1-(7-tert.-butyl-2,3-dihydro-3,3-dimethylbenzo[b]furan-5-yl)-4- cyclopylbutan-1-one (PGV-20229), in plasma matrices by stable-isotope-dilution gas chromatography-mass spectrometry

A sensitive and selective GC-MS method was developed for the determination of low levels of a novel antiinflammatory agent, 1-(7-tert.-butyl-2,3-dihydro-3,3-dimethylbenzo[b]furan-5-yl)-4- cyclopropylbutan-1-one (I), in small volumes of animal plasma. The method involved the addition of 13C6-labeled-I to plasma samples, followed by a simple liquid-liquid extraction with hexane to isolate the analytes from matrix components. The levels of I in the sample extracts were determined by isotope-dilution GC-MS analysis using selected-ion monitoring. The method was linear over three orders of magnitude, with a limit of quantitation of 1.8 ng/ml I, using plasma sample volumes of 0.1 ml. The method was utilized to determine the pharmacokinetic parameters of I in rats and dogs, following intravenous administration.

Highly sensitive high-performance liquid chromatographic-tandem mass spectrometric method for the analysis of dextromethorphan in human plasma

A stable-isotope-dilution HPLC-tandem mass spectrometry-based method was developed for the determination of dextromethorphan in human plasma. Plasma samples were prepared for analysis by solid-phase extraction on octadecylsilane extraction cartridges. Dextromethorphan and the deuterium-labeled dextromethorphan internal standard were chromatographed on a short reversed-phase column and detected by a selected-reaction-monitoring scheme. Linear standard curves were obtained over three orders of magnitude and the limit of quantitation for dextromethorphan was 50 pg/ml, using a 1-ml plasma sample. The combination of HPLC and electrospray tandem mass spectrometry resulted in a rapid, selective and sensitive method for the analysis of dextromethorphan in plasma. The method was applied for the evaluation of the pharmacokinetic profile of dextromethorphan in human volunteers following peroral administration.

Validation and application of an immunoradiometric assay for the determination of human parathyroid hormone fragment 1-34 in dog plasma following subcutaneous and intravenous administration

A method for the measurement of human parathyroid hormone fragment 1-34 (PTH1-34) in dog plasma was developed by modification of a commercially available immunodiometric assay (IRMA) designed for the determination of rat PTH1-34 in serum. Major modifications were made to the assay in order to circumvent significant problems encountered during the validation of the IRMA. PTH1-34 was found to be highly unstable in both rat serum and dog serum and plasma at room temperature, in contrast to literature reports. The addition of a protease inhibitor cocktail to serum or plasma samples was necessary to prevent in-vitro proteolytic degradation of human PTH1-34 prior to analysis. Additionally, plasma was chosen over serum as the sample matrix to expedite the separation of samples from cells, minimizing proteolytic degradation prior to the addition of cocktail. Finally, the reported 100% cross-reactivity between rat and human PTH1-34 was found to be only 65%; therefore, a human PTH1-34 standard was substituted for the rat standard. These modifications allowed the accurate measurement of human PTH1-34 in plasma obtained from dogs dosed intravenously and subcutaneously with human PTH1-34 using a commercially available kit.

Evaluation of ketorolac concentrations in plasma and gingival crevicular fluid following topical treatment with oral rinses and dentifrices

Two clinical studies were conducted to determine the relative amounts of ketorolac detectable locally in the gingival crevicular fluid (GCF) and systemically in plasma after oral, topical drug administration. The rinse study compared topical administration of three concentrations of ketorolac tromethamine (0.1%, 0.5%, and 0.01%) in oral rinse formulations administered topically and a perorally administered capsule (10 mg), and the dentifrice study compared two concentrations of ketorolac in dentifrice formulations (0.15% and 1.0%) with a 0.1% oral rinse, all treatments administered topically. The dose-corrected systemic availability of the three oral rinses evaluated in the rinse study relative to the peroral capsule was about 15%. However, the ratios of the observed maximum GCF ketorolac concentration to maximum plasma ketorolac concentration ranged from 22 to 49, compared to less than 1 for the peroral ketorolac capsule. Using this ratio as an estimate of the ability of a treatment to target the drug to the gingival tissue, these data indicate that the ketorolac oral rinses achieved greater delivery of drug to the gingival tissue (presumed site of action for periodontitis) with a lower systemic drug load than peroral administration of a ketorolac capsule. The dose-corrected relative systemic bioavailabilities for the dentifrice treatments with respect to the 0.1% rinse in the dentifrice study were 59.2% and 86.4% for the 1.0% and 0.15% dentifrices, respectively, indicating that significantly less ketorolac was systemically available from the two dentifrices relative to the oral rinse. The relative bioavailabilities of ketorolac in the GCF after dosing with the dentifrice formulations with respect to the rinse were 89.1% for the 1.0% dentifrice and 19.7% for the 0.15% dentifrice. Thus, the 1.0% dentifrice appears to provide statistically equivalent levels of ketorolac to the gingival tissue as the 0.1% oral rinse with significantly less systemic exposure. The T1/2 of ketorolac in the GCF was about 0.5 h for all three treatments, which is significantly less than the plasma half-life of about 5.3 h. These data suggest that GCF levels of ketorolac should remain above the IC50 for PGE2-stimulated IL-1 bone resorption for about 7 h following treatment, assuming continuation of the first-order elimination observed over the first two postdosing hours. We conclude that oral rinses and dentifrices are effective and preferred vehicles for administration of ketorolac for use in treatment of periodontitis.

Determination of two mebeverine metabolites, mebeverine alcohol and desmethylmebeverine alcohol, in human plasma by a dual stable isotope-based gas chromatographic-mass spectrometric method

A dual stable isotope-based GC-MS method was developed for the simultaneous determination of two metabolites of mebeverine, mebeverine alcohol and desmethylmebeverine alcohol, in human plasma. Plasma samples were treated with beta-glucuronidase to cleave the glucuronide conjugates of both compounds prior to analysis. The treated plasma was prepared for analysis by solid-phase extraction using octadecylsilane cartridges. The isolated metabolites were derivatized and analyzed by GC-MS using selected-ion monitoring. Plots of peak-area ratio were linear with metabolite concentration from 2 to 200 ng/ml and the limit of detection for both metabolites was 0.5 ng/ml. The GC-MS methodology was applied to the analysis of plasma from human subjects following peroral administration of mebeverine. Pharmacokinetic parameters for both metabolites were determined and suggest that relative systemic mebeverine exposure may potentially be assessed using metabolite kinetics, if the latter subsequently are demonstrated to be linear with mebeverine dose.

Evaluation of a benchtop ion trap gas chromatographic-tandem mass spectrometric instrument for the analysis of a model drug, tebufelone, in plasma using a stable-isotope internal standard

The performance of a benchtop GC-ion trap MS-MS instrument, the Varian Saturn 4D, was evaluated for the analysis of a model drug, tebufelone, in plasma. The sample preparation scheme was designed to provide a highly complex extract with matrix-derived interferences eluting near and at the retention time of tebufelone and its stable-isotope-labeled analog. The performance of the ion trap in the selected-reaction-monitoring mode was evaluated and also compared with results obtained on a benchtop GC-MS linear quadrupole instrument operated in the selected-ion-monitoring mode. The ion trap, operated in the selected-reaction-monitoring mode, was found to provide a higher degree of selectivity for the analysis of tebufelone. The increased selectivity obtained on the ion trap operated in the selected-reaction-monitoring mode resulted in superior accuracy and precision, as well as a lower limit of quantitation relative to that obtained by the GC-MS analysis. A linear standard curve was obtained over three orders of magnitude and the limit of quantitation for tebufelone in plasma was 100 pg/ml using the GC-ion trap MS-MS instrument.

A comparison of topical ketorolac, systemic flurbiprofen, and placebo for the inhibition of bone loss in adult periodontitis

Systemic non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to reduce alveolar bone loss in periodontitis. This study assesses the efficacy of a topical NSAID rinse, containing ketorolac tromethamine as the active agent. Adult periodontitis patients (n = 55) were studied in this 6-month randomized, double blind, parallel, placebo and positive-controlled study. Each patient had a least 3 sites at high risk for bone loss as assessed by low dose bone scan. Groups, balanced for gender, were assigned to one of three regimens: bid ketorolac rinse (0.1%) with placebo capsule; 50 mg bid flurbiprofen capsule (positive control) with placebo rinse; or bid placebo rinse and capsule. Prophylaxes were provided every 3 months. Monthly examinations assessed safety, gingival condition, and gingival crevicular fluid PGE2. Standardized radiographs were taken at baseline and at 3 and 6 months for digital subtraction radiography. A significant loss in bone height was observed during the study period in the placebo group (-0.63 +/- 0.11; P < 0.001), but not in the flurbiprofen (-0.10 +/- 0.12; P = 0.40) or ketorolac rinse (+0.20 +/- 0.11 mm; P = 0.07) groups. Nested ANOVA revealed that ketorolac and flurbiprofen groups had less bone loss (P < 0.01) and reduced gingival crevicular fluid PGE2 levels (P < 0.03) compared to placebo. ANOVA suggests (P = 0.06) that ketorolac rinse preserved more alveolar bone than systemic flurbiprofen at the dose regimens utilized. These data indicate that ketorolac rinse may be beneficial in the treatment of adult periodontitis.

Supercritical fluid extraction as a sample preparation technique for the direct isolation of drugs from plasma prior to analysis

Supercritical carbon dioxide was used for the direct extraction of drugs from plasma prior to analysis. The supercritical fluid was directly passed through plasma samples spiked with either a neutral (flavone) or an acidic (ketorolac) drug. The addition of an antifoam agent to the plasma prior to extraction was required to avoid restrictor plugging caused by denaturation of the plasma proteins by the supercritical fluid. The effluent from the extraction cell was bubbled through a small volume of methanol or into an empty tube to trap the extracted drug. The effect of extraction pressure and time on absolute recovery were examined. The absolute recovery, selectivity, precision and accuracy of the supercritical fluid extraction approach was compared to conventional liquid-liquid extraction using reversed-phase HPLC with ultraviolet detection.

Effects of tebufelone (NE-11740), a new anti-inflammatory drug, on arachidonic acid metabolism

Tebufelone is a novel nonsteroidal anti-inflammatory drug (NSAID), of the di-tert-butylphenol (DTBP) class, which displays potent anti-inflammatory, analgesic and anti-pyretic properties in a variety of animal models. In this report, the effects of Tebufelone on arachidonic acid (AA) metabolism are reviewed. Tebufelone potently inhibits the formation of prostaglandins (PGE2) a key mediator of pain and inflammation, in isolated enzyme preparations (IC50 = 1.5 microM, KI = 0.35 microM), two in vitro cellular systems: rat peritoneal macrophages (IC50 = 0.02 microM) and human whole blood (IC50 = 0.08 microM), and ex vivo in man. In addition to PGE2 inhibition, which is common to all NSAIDs, higher concentrations of Tebufelone block the in vitro formation of products of the lipoxygenase pathway [leukotrienes (LTB4)] in rat macrophages (IC50 = 20 microM) and human whole blood (IC50 = 22 microM). Substrate incorporation studies (14C-AA) indicate that Tebufelone reversibly inhibits cyclooxygenase (CO) and 5-lipoxygenase (5-LO) enzymes rather than regulating the release of AA. Tebufelone was shown to be a more potent CO inhibitor than indomethacin and a less potent 5-LO inhibitor than RG-5901. Comparisons to structurally related compounds under development (E-5110, Esai; KME-4, Kanagafuchi), found Tebufelone to be the most potent CO inhibitor in vitro. All three DTBP compounds were equipotent 5-LO inhibitors. It is likely that Tebufelone's inhibitory effects on AA metabolism are, in part, responsible for its in vivo efficacy and enhanced safety profile.

Evaluation of capillary supercritical fluid chromatography with mass spectrometric detection for the analysis of a drug (mebeverine) in a dog plasma matrix

Supercritical fluid chromatography with mass spectrometric detection was evaluated as a technique for the analysis of drugs in biological fluids. Dog plasma was spiked with a model drug, mebeverine, and with a deuterium-labeled analog of mebeverine. The spiked plasma was prepared for analysis by solid-phase extraction on octadecylsilane cartridges. Mebeverine levels in the spiked dog plasma samples were determined by interpolation from a standard curve. Accuracy and precision of the analysis were determined within and between days. In general, accuracy was found to be 100 +/- 15% for plasma samples spiked with 6 to 60 ng mebeverine/ml. The relative standard deviation for replicate sample analysis over this concentration range was between 5 and 12.5%.

Solid-phase extraction with supercritical fluid elution as a sample preparation technique for the ultratrace analysis of flavone in blood plasma

A new sample preparation technique, solid-phase extraction with supercritical fluid elution, was developed for the selective isolation of ultratrace levels of drugs from plasma. Plasma samples spiked with a drug were applied to octadecylsilane cartridges and the cartridges were then washed, briefly dried and directly fitted into cells for subsequent supercritical fluid elution. The absolute recovery was studied by using a radiolabeled model compound. The extraction selectivity was examined by chromatographing the extracts with a reversed-phase high-performance liquid chromatographic method with ultraviolet detection. The effects of extraction pressure and the length of capillary restrictors on drug recovery were examined in order to determine the optimal conditions for supercritical fluid elution. The performance of the method was compared to that of conventional solid-phase extraction in terms of recovery, selectivity, precision and accuracy of analysis. Flavone was used as the model compound and dog plasma as the biological matrix for these studies.

Combined supercritical fluid extraction/solid-phase extraction with octadecylsilane cartridges as a sample preparation technique for the ultratrace analysis of a drug metabolite in plasma

Supercritical fluid extraction was coupled with solid-phase extraction using octadecylsilane cartridges for the selective isolation of ultratrace levels of a drug metabolite, mebeverine alcohol, from plasma. Plasma was directly applied to the extraction cartridge, the cartridge was washed to remove protein and then extracted under supercritical conditions using CO2/5% methanol. The effluent from the extraction cell was bubbled through a small volume of 2-propanol to trap the extracted mebeverine alcohol. The effects of extraction pressure and temperature on analyte recovery were examined. The absolute recovery, selectivity, precision, and accuracy of the combined supercritical fluid extraction/solid-phase extraction approach were compared to those of conventional solid-phase extraction using gas chromatography/mass spectrometry in the selected-ion monitoring mode. Mebeverine alcohol was used as a model compound, and dog plasma was employed as the biological matrix for these studies.

Application of liquid chromatography with on-line radiochemical detection to metabolism studies on a novel class of analgesics

Vanilloids are a class of compounds structurally related to capsaicin, the pungent principle of hot peppers, which are under development as a novel class of analgesics. Vanilloids undergo extensive first-pass metabolism when dosed orally to rats and mice. These compounds, as well as capsaicin, would be anticipated to be susceptible to three major routes of metabolism: (omega, beta)-oxidation of the alkyl side chain, hydrolysis of the amide bond and conjugation of the phenolic group. Olvanil [N-(3-methoxy-4-hydroxybenzyl)oleamide], radiolabelled with either 14C at the benzylic carbon or 3H in the oleyl side chain, was studied in various in vitro, in situ and in vivo metabolism models to determine the major route(s) of intestinal and hepatic metabolism in rats for this new class of compounds. Models used in metabolism studies included isolated hydrolytic enzymes, cell-free intestinal and liver supernatants, hepatocytes, enterocytes, perfused intestine and whole animal studies. Reversed-phase liquid chromatography (LC) with on-line radiochemical detection was used to examine the metabolic profiles from the different models. The major metabolic route for olvanil in both the intestine and the liver was found to be hydrolysis of the amide bond. The benefits of selective 14C and 3H labels in conjunction with LC with on-line radiochemical detection are discussed.

Heterogeneous enzyme immunoassay with electrochemical detection: competitive and "sandwich"-type immunoassays

In these competitive and "sandwich"-type heterogeneous enzyme immunoassays, based on liquid chromatography with electrochemical detection, rabbit immunoglobulin G is used as a model compound. Alkaline phosphatase (EC 3.1.3.1), the labeling enzyme, catalyzes conversion of phenyl phosphate to phenol. After separation on an octyldecylsilane column, the enzyme-generated phenol is detected in a thin-layer cell at a carbon-paste working electrode. The detection limit for phenol is 5.0 nmol/L. The electrode response varies linearly with concentration over a range of three orders of magnitude. For the sandwich-type assay procedure the detection limit is 10 ng/L; the linearity ranges over four orders of magnitude. The detection limit of the competitive immunoassay is 5 micrograms/L. The dynamic range spans two orders of magnitude.

Heterogeneous enzyme immunoassay with electrochemical detection: competitive and "sandwich"-type immunoassays

In these competitive and "sandwich"-type heterogeneous enzyme immunoassays, based on liquid chromatography with electrochemical detection, rabbit immunoglobulin G is used as a model compound. Alkaline phosphatase (EC 3.1.3.1), the labeling enzyme, catalyzes conversion of phenyl phosphate to phenol. After separation on an octyldecylsilane column, the enzyme-generated phenol is detected in a thin-layer cell at a carbon-paste working electrode. The detection limit for phenol is 5.0 nmol/L. The electrode response varies linearly with concentration over a range of three orders of magnitude. For the sandwich-type assay procedure the detection limit is 10 ng/L; the linearity ranges over four orders of magnitude. The detection limit of the competitive immunoassay is 5 micrograms/L. The dynamic range spans two orders of magnitude.

Electrochemical investigation of hapten-antibody interactions by differential pulse polarography

The binding of electroactively labeled estriol with estrogen-specific antibody and its subsequent displacement by unlabeled estriol have been monitored by differential pulse polarography. Estriol was found to be electro-inactive in the potential range -200 mV to -1000 mV vs a silver/silver chloride electrode. Estriol labeled in the 2 and 4 position with nitro groups was electroactive, giving two reduction waves at -422 mV and -481 mV vs a silver/silver chloride electrode. The peak current was linear with concentration over the range 60 micrograms/L to 3.7 mg/L. The addition of aliquots of estrogen-specific antibody reduced the peak current proportionately, indicating the binding of ligand to specific antibody. Subsequent addition of unlabeled estriol produced incremental increases in peak reduction current, indicating competitive and reversible binding of the two ligands for the antibody. Separation of bound from free labeled hapten was not necessary because reduction of the antibody-bound labeled estriol is attenuated at the electrode.

Electrochemical investigation of hapten-antibody interactions by differential pulse polarography

The binding of electroactively labeled estriol with estrogen-specific antibody and its subsequent displacement by unlabeled estriol have been monitored by differential pulse polarography. Estriol was found to be electro-inactive in the potential range -200 mV to -1000 mV vs a silver/silver chloride electrode. Estriol labeled in the 2 and 4 position with nitro groups was electroactive, giving two reduction waves at -422 mV and -481 mV vs a silver/silver chloride electrode. The peak current was linear with concentration over the range 60 micrograms/L to 3.7 mg/L. The addition of aliquots of estrogen-specific antibody reduced the peak current proportionately, indicating the binding of ligand to specific antibody. Subsequent addition of unlabeled estriol produced incremental increases in peak reduction current, indicating competitive and reversible binding of the two ligands for the antibody. Separation of bound from free labeled hapten was not necessary because reduction of the antibody-bound labeled estriol is attenuated at the electrode.