A rapid, simple, high-performance liquid chromatography method for the clinical measurement of beta-lactam antibiotics in serum and interstitial fluid.

Background: enhanced methods of therapeutic drug monitoring are required to support the individualisation of antibiotic dosing based on pharmacokinetics (PK) parameters. PK studies can be hampered by limited total serum volume, especially in neonates, or by sensitivity in the case of critically ill patients. We aimed to develop a liquid chromatography-mass spectrometry (LC/MS) analysis of benzylpenicillin, phenoxymethylpenicillin and amoxicillin in single low volumes of human serum and interstitial fluid (ISF) samples, with an improved limit of detection (LOD) and limit of quantification (LOQ), compared with previously published assays. Methods: sample clean-up was performed by protein precipitation using acetonitrile. Reverse phase chromatography was performed using triple quadrupole LC/MS. The mobile phase consisted of 55% methanol in water + 0.1% formic acid, with a flow rate of 0.4 mL min-1. Antibiotics stability was assessed at different temperatures. Results: chromatographic separation was achieved within 3 minutes for all analytes. Three common penicillins can now be measured in a single low-volume blood and ISF sample (15 µL) for the first time. Validation has demonstrated the method to be linear over the range 0.0015-10 mg L-1, with an accuracy of 93-104% and high sensitivity, with LOD ≈ 0.003 mg L-1 and LOQ ≈ 0.01 mg L-1 for all three analytes, which is critical for use in dose optimisation/individualisation. All evaluated penicillins indicated good stability at room temperature over 4 h, at (4 °C) over 24 h and at -80 °C for 6 months. Conclusion: the developed method is simple, rapid, accurate and clinically applicable for the quantification of three penicillin classes.

[(89)Zr]oxinate4 for long-term in vivo cell tracking by positron emission tomography.

PURPOSE: (111)In (typically as [(111)In]oxinate3) is a gold standard radiolabel for cell tracking in humans by scintigraphy. A long half-life positron-emitting radiolabel to serve the same purpose using positron emission tomography (PET) has long been sought. We aimed to develop an (89)Zr PET tracer for cell labelling and compare it with [(111)In]oxinate3 single photon emission computed tomography (SPECT). METHODS: [(89)Zr]Oxinate4 was synthesised and its uptake and efflux were measured in vitro in three cell lines and in human leukocytes. The in vivo biodistribution of eGFP-5T33 murine myeloma cells labelled using [(89)Zr]oxinate4 or [(111)In]oxinate3 was monitored for up to 14 days. (89)Zr retention by living radiolabelled eGFP-positive cells in vivo was monitored by FACS sorting of liver, spleen and bone marrow cells followed by gamma counting. RESULTS: Zr labelling was effective in all cell types with yields comparable with (111)In labelling. Retention of (89)Zr in cells in vitro after 24 h was significantly better (range 71 to >90%) than (111)In (43-52%). eGFP-5T33 cells in vivo showed the same early biodistribution whether labelled with (111)In or (89)Zr (initial pulmonary accumulation followed by migration to liver, spleen and bone marrow), but later translocation of radioactivity to kidneys was much greater for (111)In. In liver, spleen and bone marrow at least 92% of (89)Zr remained associated with eGFP-positive cells after 7 days in vivo. CONCLUSION: [(89)Zr]Oxinate4 offers a potential solution to the emerging need for a long half-life PET tracer for cell tracking in vivo and deserves further evaluation of its effects on survival and behaviour of different cell types.

Synthesis and characterisation of zirconium complexes for cell tracking with Zr-89 by positron emission tomography.

The increasing availability of the long half-life positron emitter Zr-89 (half life 78.4 h) suggests that it is a strong candidate for cell labelling and hence cell tracking using positron emission tomography. The aim was to produce a range of neutral ZrL4 lipophilic complexes for cell labelling which could be prepared under radiopharmaceutical conditions. This was achieved when the ligand was oxine, tropolone or ethyl maltol. The complexes can be prepared in high yield from zirconium(iv) precursors in hydrochloric or oxalic acid solution. The oxinate and tropolonate complexes were the most amenable to chromatographic characterisation, and HPLC and ITLC protocols have been established to monitor their radiochemical purity. The radiochemical synthesis and quality control of (89)Zr(oxinate)4 is reported as well as preliminary cell labelling data for the oxinate, tropolonate and ethyl maltolate complexes which indicates that (89)Zr(oxinate)4 is the most promising candidate for further evaluation.

Synthesis, characterisation and detection of γ-hydroxybutyrate salts.

Sodium, potassium, magnesium and calcium salts of gamma-hydroxybutyrate have been synthesised from gamma-butyrolactone and the corresponding group 1 or 2 hydroxide. Although the group 2 salts are non-hygroscopic, FT-IR spectroscopy and elemental analysis revealed them to be hydrated. X-ray powder diffraction was found to be a quick, non-destructive method of discriminating between the four salts. The Smith and the chlorophenol red/modified Schweppes reagent presumptive colour tests gave positive results regardless of the salt tested. Microcrystalline tests for NaGHB were in accordance with previous literature reports, but results for the other three salts were not reliable.