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Biomedical subjects

Christophe Chassaing

Publications and source records attributed to Christophe Chassaing.

5 recordsLinked to original sources
PubMed2004

A direct comparison of the performance of ground, beaded and silica-grafted MIPs in HPLC and turbulent flow chromatography applications.

Spherical molecularly imprinted polymers (MIPs) specific to the beta-blocker propranolol have been synthesised using two different approaches and compared to traditional ground monolithic MIPs in HPLC and TFC applications. TFC is a LC technique used for rapid extraction of compounds directly from complex matrices. It can be easily coupled to HPLC and MS for automation of an extraction/analysis procedure. Spherical MIP beads were produced using a suspension polymerisation technique and silica/MIP composite beads by grafting MIP to spherical silica particles using a surface-bound initiator species. Synthesis of both beaded and silica-grafted MIPs was more practical than using the traditional grinding method and yields of spherical particles of the required size between 80 and 100% were routinely achieved. Under HPLC conditions, beaded and ground MIP materials showed a degree of chiral separation for all of the nine beta-blockers tested. The beaded MIP, however, showed much better flow properties and peak shape than the ground material. Silica-grafted MIP showed some separation in five of the drugs and a large improvement in peak shape and analysis times compared with both ground and beaded MIPs. The materials prepared were also used in extraction columns for Turbulent Flow Chromatography (TFC). Although no imprinting effect was observed under typical TFC conditions, beaded polymer materials showed promise for use as TFC extraction columns due to the good flow properties and clean extracts obtained.

Adrenergic beta-Antagonists↗
PubMed2003

Microwave-assisted solid-phase synthesis of phthalimides.

[reaction: see text] A traceless solid-phase synthesis of substituted phthalimides is proposed. The target compounds are obtained within minutes by a microwave-assisted cyclative cleavage in good yields and excellent purities.

Journal Article↗
PubMedDate not supplied

Evolution of an open-access quantitative bioanalytical mass spectrometry service in a drug discovery environment.

Increased demand for assays for compounds at the early stages of drug discovery within the pharmaceutical industry has led to the need for open-access mass spectrometry systems for performing quantitative analysis in a variety of biological matrices. The open-access mass spectrometers described here are LC/MS/MS systems operated in 'multiple reaction monitoring' (MRM) mode to obtain the sensitivity and specificity required to quantitate low levels of pharmaceutical compounds in an excess of biological matrix. Instigation of these open-access systems has resulted in mass spectrometers becoming the detectors of choice for non-expert users, drastically reducing analytical method development time and allowing drug discovery scientists to concentrate on their core expertise of pharmacokinetics and drug metabolism. Setting up an open-access facility that effectively allows a user with minimal mass spectral knowledge to exploit the MS/MS capability of triple quadrupole mass spectrometers presents a significantly different challenge from setting up qualitative single stage mass spectrometry systems. Evolution of quantitative open access mass spectrometry within a pharmaceutical drug metabolism and pharmacokinetics group, from its beginnings as a single generic system to a series of specialist fully integrated walk-up facilities, is described.

Automation↗
PubMedDate not supplied

Controlled trials of very high dose folic acid, vitamins B12 and B6, intravenous folinic acid and serine for treatment of hyperhomocysteinemia in ESRD.

BACKGROUND: Hyperhomocysteinemia is seen in most hemodialysis (HD) patients and is an independent risk factor for cardiovascular disease. Homocysteine metabolism via remethylation requires activated folate and vitamin B12 and metabolism via transsulfuration requires serine and vitamin B6. Prior studies have shown highly variable effects of supplemental B vitamin and folate therapy for hyperhomocysteinemia. We undertook a fully controlled trial with abnormally high doses of folic acid alone or with supplemental vitamin B6 and B12 compared with active folate alone or with serine. METHODS: Two prospective studies were undertaken in hemodialysis patients. In the first study (protocol A), hyperhomocysteinemia was treated in 77 patients with 30 or 60 mg folic acid with or without vitamins B6 and B12 for eight weeks and compared with matching placebos. In the second study (protocol B), hyperhomocysteinemia was treated in 37 patients with intravenous folinic acid given alone or with serine and compared with matching placebos. All patients received the standard of care treatment with a multivitamin tablet before and throughout the protocol to test the hypothesis that additional therapy is required over and above the routine therapy for maximum reduction in total homocysteine (tHcy). RESULTS: Normal volunteers; The mean (SD) tHcy of 128 normal subjects was 6.5 (4) micromol/L. Protocol A; Plasma folate increased significantly in the groups given folic acid at both four and eight weeks (P = 0.0001 at both time points). Plasma vitamin B12 was significantly increased at four weeks (P = 0.0018) but not at eight weeks (P = 0.064) in those given Vitamin B12. However, tHcy did not differ between treatment groups at baseline (P = 0.63), four weeks (P = 0.79) or eight weeks (P = 0.74). Protocol B: Plasma folate increased significantly at four weeks in those receiving folinic acid (P = 0.0001) but tHcy was not significantly different between groups (P = 0.92). In neither study was there any significant change in tHcy comparing before and during any treatment intervention. CONCLUSIONS: In our studies high dose oral folic acid, intravenous folinic acid, vitamins B6 and B12 and oral serine were ineffective at lowering tHcy in patients on hemodialysis when given folic acid, folinic acid serine or B vitamins in addition to routine folic acid and B vitamin supplements.

Administration, Oral↗