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At least 1,153 records · Page 64Linked to original sources
PubMed2005

Validating regulatory-compliant wide dynamic range bioanalytical assays using chip-based nanoelectrospray tandem mass spectrometry.

Automated chip-based infusion nanoelectrospray ionization coupled to tandem mass spectrometry (nanoESI-MS/MS) was used to validate a bioanalytical assay conforming to United States Food and Drug Administration (FDA) regulatory guidelines and Good Laboratory Practices (GLP). Reboxetine was used as the analyte fortified in dog plasma along with an analog internal standard (IS). The best nanoESI response for reboxetine was observed with 90% acetonitrile (ACN)/water without any mobile phase modifiers. The analyte and IS were extracted from dog plasma samples by liquid-liquid extraction (LLE). The supernatant was concentrated to dryness and redissolved in 90% ACN/water for nanoESI. Selected reaction monitoring (SRM) data were collected for all samples to generate ion current profiles with a base width of approximately 20 s. Selectivity experiments showed no interferences in blank plasma samples. Interferences as a result of in-source collision-induced dissociation of metabolites were not an issue due to the previously documented metabolism of reboxetine. Matrix suppression was evaluated across multiple lots of dog plasma as well as over different animal species (rabbit, rat, mouse) and different anticoagulants (heparin, EDTA). Matrix suppression ranged from approximately 30-60% across the different lots, species etc.; however, in all instances, the analyte and the IS were suppressed by similar amounts, suggesting the similarity in ionization properties between the two. A three-batch validation was performed (each batch consisting of four different concentrations, six replicates of each concentration) and demonstrated inter-assay accuracy (% relative error; RE) of less than +/-8% and an inter-assay precision (% relative standard deviation; RSD) of less than 7%, thus meeting regulatory guidelines. A comparison of analyses by nanoESI-MS/MS and liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) showed that nanoESI-MS/MS had a greater slope for the calibration standard curve compared to LC/MS/MS, indicating greater sensitivity for the former technique. It is also noteworthy that the amount of sample infused during nanoESI-MS/MS was approximately 80-fold less compared to the amount of sample injected during LC/MS/MS. The absence of carryover (attributed to the lack of a common fluid path) in the nanoESI technique enabled the extension of the assay linear dynamic range to 500,000-fold, and the possibility of analyzing samples in a single batch without the need for re-analysis of samples with high concentrations. This technology offers the possibility for increased throughput for studies supporting drug development by providing fast data turnaround for assays conforming to regulatory guidelines and GLPs.

Animals↗
PubMed2007

Application of phenylboronic acid modified hydrogel affinity chips for high-throughput mass spectrometric analysis of glycated proteins.

The complexity of the human plasma proteome is greatly increased by post-translational modifications. Besides physiological modifications, pathological conditions such as diabetes are responsible for adding to this complexity by producing advanced glycation endproducts (AGEs). When searching for specific biomarkers it is a prerequisite to reduce this complexity prior to analysis. To do this, agarose hydrogel was used to create a high-capacity affinity layer on the modified aluminum surface of MALDI (matrix-assisted laser desorption/ionization) targets. 3-Aminophenylboronic acid was immobilized via cyanogen bromide activation as a ligand for affinity sorption of glycated proteins, followed by their direct detection by MALDI. High protein capacity of prepared MALDI chips, efficient separation and low non-specific protein binding were demonstrated. The results show that phenylboronic acid modified hydrogels are very suitable for creating affinity surfaces for the high-throughput analysis of AGEs.

Aluminum↗
PubMed1995

Structure of the osmo-regulated H2O-channel, AQP-CHIP, in projection at 3.5 A resolution.

An osmo-regulated H2O-channel, aquaporin-CHIP, from bovine red blood cell membranes was purified and reconstituted with lipids, forming two-dimensional crystalline patches that diffract to about 3.0 A resolution. Electron diffraction patterns and high-resolution images of the crystalline patches embedded in glucose were recorded and used to calculate the projection map at 3.5 A resolution. The map confirms that the osmo-regulated H2O-channel basic packing unit is a tetramer and begins to reveal it's structural design. The basic architecture of the H2O-channel protein consists of a trapezoid-like envelope and a substructure located within the trapezoid that could play a crucial role in the channel structure itself; near this substructure there is a region of very low density, which is the probable site of the channel. The trapezoid-like envelope is composed of high density regions many of which can be interpreted as projections of alpha-helices along their axes.

Animals↗
PubMed2000

New approaches for innovations in sensitive Edman sequence analysis by design of a wafer-based chip sequencer.

In the last few years the development of new mass spectrometric techniques enabled fast and sensitive protein analysis by the introduction of mass spectrometry (MS) fingerprinting and MS/MS sequencing. For these methods mixtures of peptide fragments of the proteins can be employed, whereas the Edman degradation method requests purified peptides. On the other hand, Edman sequencing has the advantages that interpretation of the data is more simple, extended sequences can be derived, and reliable sequence information on unknown proteins is possible. Hence, Edman chemistry as an alternative technique to MS is still valuable. But higher sensitivity of the sequencers is needed in order to meet modern demands, e.g. in proteomics research. We designed a wafer-based chip sequencer for protein and peptide sequencing in the femto- to attomole range. The main advantage of our new design is the complete integration of dead volume free valves together with reactor and converter and volume-measuring loops within one wafer-based system. In this system aggressive chemicals and solvents for the Edman degradation can be delivered in sub-microliter amounts, which allows a considerable shortening of the degradation cycles. Further, we developed sensitive maintenance and tightness tests to prove a precise and reproducible delivery of the chemicals and the reduction of drying times as compared with conventional sequencers. Real parallel processing of several samples can easily be implemented. The system is designed to serve future needs in protein research.

Indicators and Reagents↗
PubMed2003

Chemosensitivity testing of human tumors using Si-sensor chips.

Chemotherapy is, on its own or in combination with other treatments, a very effective anticancer therapy. Introduced in the middle of the last century, chemotherapy today still faces the problem of determining which specific agent or agents are able to yield the desired clinical therapeutical effect for a particular tumor and patient. Numerous tests in vitro have been developed to detect chemosensitivity and chemoresistance and also for screening new drugs. Three groups of tests can be defined: 1, cell viability tests; 2, measurements of cell metabolism; and 3, clonogenic assays. Test time, tissue preparation, complexity of test performance, and correlation with the clinical progress of the disease are criteria used to judge how successful the tests are. The introduction of Si-sensor chips, which are able to detect metabolic changes in living cells, has opened up new possibilities in this field. Basically two sensor principles or types can be considered: (a) the light-addressed potentiometric sensor (LAPS) and (b) the multisensor array (MSA). Whereas LAPS measures one, MSA registers online many parameters (for instance, impedance, pH, O2, temperature). The aim of this chapter is to review this technology and to present recent applications using cells, tissue slices, and biopsies.

Antineoplastic Agents↗
PubMed1988

Phase I study of weekly-administered iproplatin [cis-dichloro-trans-dihydroxy-bis-isopropylamine platin (chip, JM9)].

Iproplatin [cis-dichlor-trans-dihydroxy-bis-isopropylamine platinum (CHIP, JM9)] is a new antineoplastic platinum analogue with an octahedral conformation. It has more water solubility than does cisplatin and was found to have less neurotoxicity and nephrotoxicity in experimental animals than cisplatin. Like cisplatin, it has been demonstrated to have a broad spectrum of activity in experimental tumor systems. A phase I study of iproplatin was conducted in 28 patients (12 with melanoma, 8 with sarcoma, 6 with breast cancer, and 2 with colon cancer). All patients had failed prior chemotherapy. Four consecutive doses of iproplatin were administered at weekly intervals followed by a rest period of two weeks for hematologic recovery (one course). One hundred forty-two weekly doses were administered with all patients except three receiving at least one full course. The weekly starting dose of 40 mg/m2 was increased to 120 mg/m2 given over 30 minutes without hydration. Myelosuppression predominantly thrombocytopenia, was the dose-limiting toxicity at weekly doses of greater than or equal to 95 mg/m2 per course. With iproplatin doses 75 mg/m2, 95 mg/m2, and 120 mg/m2, the lowest median granulocyte counts were 2.6 x 10(3)/mm3, 2.2 x 10(3)/mm3, and 1.8 x 10(3)/mm3, respectively. Similarly, at iproplatin doses of 75 mg/m2, 95 mg/m2, and 120 mg/m2, the lowest median platelet counts were 144 x 10(3)/mm3, 99 x 10(3)/mm3, and 31 x 10(3)/mm3, respectively. Mild to moderate nausea and vomiting were observed in the majority of patients. No significant neurotoxicity, nephrotoxicity, or ototoxicity was observed. Objective tumor regression was not observed in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Agents↗
PubMed1988

Urinary protein and enzyme excretion in patients receiving chemotherapy with the cis-platinum analogs carboplatin (CBDCA, JM8) and iproplatin (CHIP, JM9).

Urinary protein and enzyme excretion was measured in 33 patients with solid tumours receiving chemotherapy with the cis-platinum analogs carboplatin (JM8, CBDCA) and iproplatin (JM9, CHIP). The patients were given up to six courses of the drugs at 4-week intervals, and serial urine samples were collected weekly for periods up to 28 weeks. Overall there was no significant increase in the alkaline phosphatase (ALP), lactate dehydrogenase (LD), and N-acetyl glucosaminidase (NAG) excretion of the first posttreatment samples compared with the pretreatment samples. During the course of treatment there were transient increases in all three enzymes, some quite marked. There was no consistent increase in urinary protein or enzyme excretion during the period of treatment, suggesting that there was no cumulative nephrotoxicity. There was no change in creatinine clearance or urinary beta 2-microglobulin content. Iproplatin appeared marginally more toxic on the basis of elevated NAG and ALP during the second half of the treatment periods compared with the first (P less than 0.01 and less than 0.025, respectively).

Acetylglucosaminidase↗
PubMed1990

A strategy for the development of two clinically active cisplatin analogs: CBDCA and CHIP.

The antitumor agent cisplatin has a broad antitumor spectrum and has been incorporated into regimens that are curative for some malignant diseases. However, one of the major limitations to its clinical usefulness is the incidence of severe toxicities involving several major organ systems. Therefore, much enthusiasm has been generated for the development of cisplatin analogs that demonstrate an improved therapeutic index in some preclinical models. The two most promising analogs are CBDCA (carboplatin) and CHIP (iproplatin). The preclinical and early clinical trial results have demonstrated that these two compounds show activity in cisplatin-responsive tumors. The preclinical background providing the rationale for the clinical development of these two analogs is described. We suggest a means of screening for each analog's clinical antitumor activity and determining the analogs' utility against specific malignant diseases compared with that of the parent compound or standard treatment.

Animals↗
PubMed1992

Evaluation of CHIP (iproplatin) in recurrent pediatric malignant solid tumors. A phase II study (Pediatric Oncology Group).

CHIP (325 mg/M2), a second generation cisplatin derivative, was administered intravenously every 3 weeks to 85 pediatric patients with recurrent sarcomas (19), osteosarcomas (20), neuroblastoma (23), germ cell tumors (10), and other malignant tumors (7). Thirty-eight of them had been previously exposed to cisplatin. Partial remissions were only observed in 3 of 23 (13% SE = 7%) patients having neuroblastoma. Severe thrombocytopenia (65%) and neutropenia (35%) were the dose limiting factors.

Adolescent↗
PubMed1992

Phase II study of iproplatin (CHIP) in patients with cisplatin-refractory germ cell tumors; the need for alternative strategies in the investigation of new agents in GCT.

Fifteen patients with advanced, cisplatin-refractory germ cell tumors (GCT) were treated with iproplatin (CHIP). No objective responses were noted in any of the patients treated. By restricting the entry criteria to heavily pre-treated patients, the identification of new active agents in phase II trials may be hindered. Alternative strategies for the investigation of new agents in patients with GCT should be considered, particularly when studying the efficacy and relative toxicity of platinum analogues.

Antineoplastic Agents↗
PubMed1984

Determination of salt in potato chips.

To have an idea about the contribution of snack foods to sodium intake, the salt contents of 39 samples of potato chips sold on the Belgian market have been determined. Therefore two methods were applied: determination of chlorides by titration and of sodium by spectroscopic methods as atomic-absorption spectrofotometry (AAS) or direct-coupled plasma emission spectral analysis (DCP). The results obtained indicate a good correlation between the different methods used. However, the salt values obtained with the AAS detection technique and with titrimetry are slightly higher than those found with the DCP spectroscopic analysis. From the total samples analyzed 40% contained more than 2% of sodium chloride.

Belgium↗
PubMed2001

Micro-array chip analysis of carbonyl-metabolising enzymes in normal, immortalised and malignant human oral keratinocytes.

Enzymes involved in various protective and metabolic processes of carbonyl compounds were analysed utilising a micro-array method in a three-stage in vitro model for oral carcinogenesis involving cultured normal, immortalised and malignant human oral keratinocytes. A complete transcript profiling of identified carbonyl-metabolising enzymes belonging to the ADH, ALDH, SDR and AKR families is presented. Expression of 17 transcripts was detected in normal, 14 in immortalized and 19 in malignant keratinocytes of a total of 12,500 genes spotted on the micro-array chip. For the detected transcripts, about half were changed by cell transformation, and for the various enzyme families, differences in expression patterns were observed. The detected AKR transcripts displayed a conserved pattern of expression, indicating a requirement for the keratinocyte phenotype, while most of the detected SDRs displayed changed expression at the various stages of malignancy. The importance of multiple experiments in using a microarray technique for reliable results is underlined and, finally, the strength of the method in detecting co-expressed enzymes in metabolic pathways is exemplified by the detection of the formaldehyde-scavenging pathway enzymes and the polyol pathway enzymes.

Alcohol Dehydrogenase↗
PubMed2005

Association of the HLA region with multiple sclerosis as confirmed by a genome screen using >10,000 SNPs on DNA chips.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system, with a complex genetic background. Here, we present a genome screen for association in small scale, employing 11,555 single nucleotide polymorphisms (SNPs) on DNA chips for genotyping 100 MS patients stratified for HLA-DR2+ and 100 controls. More than 500 SNPs revealed significant differences between cases and controls before Bonferroni correction. A fraction of these SNPs was reanalysed in two additional cohorts of patients and controls, using high-throughput genotyping methods. A marker on chromosome 6p21.32 (rs2395182) yielded the highest significance level, validating the established HLA-DR association.

Genetic Linkage↗
PubMed2003

Determination of inorganic selenium species by miniaturised isotachophoresis on a planar polymer chip.

The use of miniaturised isotachophoresis to allow the simultaneous determination of two inorganic selenium species has been investigated using a poly(methyl methacrylate) chip with a 44-mm-long, 200-microm-wide, 300-microm-deep separation channel. The miniaturised device included an integrated on-column, dual-electrode conductivity detector and was used in conjunction with a hydrodynamic fluid transport system. A simple electrolyte system has been developed which allowed the separation of selenium(IV) and selenium(VI) species to be made in under 210 s. The limits of detection were calculated to be 0.52 mg L(-1) for selenium(IV) and 0.65 mg L(-1 )for selenium(VI). The method allowed the separation of the selenium species from a range of common anions including fluoride, nitrate, nitrite, phosphate, sulfate and sulfite.

Journal Article↗
PubMed2003

A rapid enzyme assay for beta-galactosidase using optically gated sample introduction on a microfabricated chip.

The ability to perform enzyme assays on microchips is demonstrated using optically gated sample introduction. The hydrolysis of fluorescein mono- beta- d-galactopyranoside (FMG) by beta- d-galactosidase ( beta-Gal) is continuously monitored using a microchip for 5 to 10 min. The outcome of the reaction was analyzed by performing serial on-chip separations of fluorescent substrate, FMG, and product, fluorescein. Kinetic information about beta-Gal has been successfully obtained by varying the concentration of FMG. beta-Gal enzymes from two different sources including bovine liver and E. coli., have been examined and compared to each other and to results obtained using traditional assay methods. In addition, the competitive inhibition of beta-Gal by phenylethyl beta- d-thiogalactoside (PETG) and beta-lactose has been studied using this technique. PETG is found to have higher inhibition than lactose in the hydrolysis. This separation-based enzyme assay technique avoids the possible fluorescence interference between FMG and fluorescein, which is a problem with the traditional plate assay method. Additionally, the amount of the enzyme and substrate required with this technique is at least four orders of magnitude lower than the traditional plate assay method. By using optically gated sample introduction, microchips allow continuous serial injections and separations without any potential switch, thus making this technique ideal as a sensor for enzyme assays. This technique should therefore be valuable for high-throughput screening in the drug discovery industry.

Fluoresceins↗
PubMed2005

A capillary electrophoresis chip with hydrodynamic sample injection for measurements from a continuous sample flow.

A microchip-based capillary electrophoresis device supported by a microfluidic network made of poly(dimethylsiloxane), used for measuring target analytes from a continuous sample flow, is presented. The microsystem was fabricated by means of replica molding in combination with standard microfabrication technologies, resulting in microfluidic components and an electrochemical detector. A new hydrodynamic sample injection procedure is introduced, and the maximum number of consecutive measurements that can be made with a poly(dimethylsiloxane) capillary electrophoresis chip with amperometric detection is investigated with respect to reproducibility. The device features a high degree of functional integration, so the benefits associated with miniaturized analysis systems apply to it.

Biosensing Techniques↗
PubMed2001

Multiport flow-control system for lab-on-a-chip microfluidic devices.

A multiport system suitable for pressure control on a lab-on-a-chip microfluidic device is described. An algorithm and a strategy for calculating pressures were developed to control the flow from multiple reservoirs for the microfluidic devices. Dye mixing and enzyme assay titration experiments were performed using pressure-driven flow only. Results show a good linear response over two orders of dynamic range.

Algorithms↗
PubMed2001

Polyester microchannel chip for electrophoresis--incorporation of a blue LED as light source.

A blue-light-emitting diode was incorporated as a fluorescence-excitation light source into a polyester microchannel chip fabricated by in situ polymerization. Placing the light-emitting facet of the diode close to the microchannel obviated any need for an additional optical arrangement. Fluorescence from the sample was transmitted by an optical fiber incorporated into the microchip perpendicular to the LED. FITC labeled amino acids were separated in the presence of 5 mM SDS by using the microchip and were detected by LED-induced fluorescence.

Amino Acids↗