Browsing by Author "Silva, Eduarda M.P."
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- Analytical methods for quantification of tranexamic acid in biological fluids: A reviewPublication . Silva, Eduarda M.P.; Barreiros, Luisa; Sá, Paula; Afonso, Carlos; Kozek-Langenecker, Sibylle; Segundo, Marcela A.Tranexamic acid (TXA) is a synthetic derivative of the amino acid lysine with antifibrinolytic properties. There is still a lack of pharmacokinetic and pharmacodynamic data concerning variable age groups undergoing surgeries with high blood loss. The optimum dose and administration schedules of TXA are still subject of research, aiming at a safe inhibition of fibrinolysis in the perioperative period. Hence, effective methods for determination of TXA in biological samples are needed. The aim of this review is to discuss the required sample treatment procedures and the analytical methods applied for quantification of TXA, focusing on selected derivatisation agents and internal standards. Methods comprising a separative step (GC, LC or CZE) coupled to spectrophotometric, fluorimetric and mass spectrometry detection were considered, showing a tendency for implementation of MS/MS methods in more recent reports. Detection limits ranging from 0.01 to 0.5 μg mL− 1 in blood plasma were so far attained using LC-MS/MS.
- Determination of tranexamic acid in human plasma by UHPLC coupled with tandem mass spectrometry targeting sub-microgram per milliliter levelsPublication . Barreiros, Luisa; Amoreira, Júlia L.; Machado, Sandia; Fernandes, Sara R.; Silva, Eduarda M.P.; Sá, Paula; Kietaibl, Sibylle; Segundo, Marcela A.Tranexamic acid (TXA) is an antifibrinolytic drug, with the ability to inhibit lysine binding at plasminogen receptors, used in adult trauma patients with on-going or at risk of significant haemorrhage. To understand the pharmacokinetics and pharmacodynamics of this drug in variable age groups undergoing surgeries with high blood loss, effective methods for determination of TXA in biological samples at sub-μg mL−1 are still required. We describe herein the development and validation of a method based on ultra-high performance liquid chromatography coupled to triple quadrupole-tandem mass spectrometry to quantify TXA in human plasma. An inexpensive, simple and efficient sample clean-up was implemented, not requiring matrix-matching calibration. Sample preparation consisted in protein precipitation using acetonitrile containing 0.5% (v/v) formic acid, followed by hydrophilic interaction based chromatographic separation, with elution in isocratic mode using a combination of acetonitrile and water (75:25, v/v), with quantification of TXA based on selected reaction monitoring. Good linearity was achieved (r2 > 0.997) for TXA concentrations ranging from 30 to 600 ng mL−1, with LOD of 18 ng mL−1 in plasma. The developed method proved to be selective, sensitive, accurate (96.4–105.7% of nominal values) and precise (RSD ≤ 4.5%). TXA was found to be stable in plasma extracts standing 24 h at room temperature (20 °C) or in the autosampler, and after three freeze-thawing cycles. Mean recovery values of TXA spiked plasma samples were ≥91.9%. No significant matrix effects were observed. The proposed methodology was successfully applied to the clinical study of plasma samples recovered during scoliosis surgery of pediatric patients pretreatment with TXA.
- Fast monolith-based chromatographic method for determination of methotrexate in drug delivery studiesPublication . Barbosa, Ana Isabel; Fernandes, Sara; Machado, Sandia; Sousa, Patrícia; Sze, Ong Yong; Silva, Eduarda M.P.; Barreiros, Luisa; Lima, Sofia A.C.; Reis, Salette; Segundo, Marcela A.Methotrexate (MTX) is a derivative of aminopterin, used as an anticancer or an anti-inflammatory agent. The development of suitable drug delivery systems containing MTX is an active area of research, requiring suitable analytical methods. Therefore, a high-throughput HPLC method is proposed for determination of MTX in the delivery system and permeation studies. Chromatographic separation was achieved on a reversed phase monolithic C18 column using isocratic elution (phosphate buffer (pH 7.0, 10 mM)-ACN (91:9, v/v)) and spectrophotometric detection at 302 nm. Total run time was 3.5 min, with MTX retention time of 2.1 min, providing 17 determinations per hour. The method was found to be specific, accurate (99.2–110%) and precise for intra-day (RSD ≤ 3.5%) and inter-day assays (RSD ≤ 3.4%). MTX showed stability after 24 h at room temperature or in the autosampler (4 °C) and over three freeze-thaw cycles with recoveries ≥94.2%. The validated method was successfully applied to establish in vitro drug release profile of MTX delivered by lipid nanoparticles. Application to pig skin permeation media provided mean recovery values ranging from 94.1 to 101.6% (RSD ≤ 1.1%).