Non-classical crystallisation pathway directly observed for a pharmaceutical crystal via liquid phase electron microscopy.

Non-classical crystallisation (NCC) pathways are widely accepted, however there is conflicting evidence regarding the intermediate stages of crystallisation, how they manifest and further develop into crystals. Evidence from direct observations is especially lacking for small organic molecules, as distinguishing these low-electron dense entities from their similar liquid-phase surroundings presents signal-to-noise ratio and contrast challenges. Here, Liquid Phase Electron Microscopy (LPEM) captures the intermediate pre-crystalline stages of a small organic molecule, flufenamic acid (FFA), a common pharmaceutical. High temporospatial imaging of FFA in its native environment, an organic solvent, suggests that in this system a Pre-Nucleation Cluster (PNC) pathway is followed by features exhibiting two-step nucleation. This work adds to the growing body of evidence that suggests nucleation pathways are likely an amalgamation of multiple existing non-classical theories and highlights the need for the direct evidence presented by in situ techniques such as LPEM.

Towards a classification strategy for complex nanostructures.

The range of possible nanostructures is so large and continuously growing, that collating and unifying the knowledge connected to them, including their biological activity, is a major challenge. Here we discuss a concept that is based on the connection of microscopic features of the nanomaterials to their biological impacts. We also consider what would be necessary to identify the features that control their biological interactions, and make them resemble each other in a biological context.

Joubert syndrome: an affected female with bilateral colobomata.

Joubert syndrome is an autosomal recessive disease characterised by hypoplasia or agenesis of the cerebellar vermis, a syndrome of episodic apnoea-hyperpnoea, rhythmic protrusion of the tongue, abnormal eye movements, hypotonia, ataxia, and psychomotor retardation. Extracerebral malformations include multicystic kidney disease, congenital hepatic fibrosis, sacral dermoid cyst and polydactyly. We report the clinical and pathological findings of a 15-year-old girl with Joubert syndrome diagnosed at autopsy. This patient had bilateral colobomata, which has not been previously described in females with Joubert syndrome.

High-performance liquid chromatographic determination of carbamazepine and carbamazepine 10,11-epoxide in plasma and saliva following solid-phase sample extraction.

A rapid, sensitive and simple to operate high-performance liquid chromatographic method for the simultaneous determination of carbamazepine (CBZ) and carbamazepine 10,11-epoxide (CBZ-EP) in plasma and saliva is described. The drug and its metabolite are extracted from both plasma and saliva using commercially available reversed-phase octadecylsilane bonded silica columns (Bond-Elut C18, 2.8 ml capacity). Separation of CBZ and CBZ-EP was achieved by reversed-phase chromatography, using a mobile phase consisting of acetonitrile-methanol-water (19:37:44) at a flow-rate of 1.8 ml/min in conjunction with a Nova-Pak C18 column. The analytical column, in Radial-Pak cartridge form, was used in combination with a Z-module RCSS and protected by a Guard-Pak precolumn module containing a Guard-Pak mu Bondapak C18 insert. Using ultraviolet detection at 214 nm, levels in the region of 50-100 ng/ml for CBZ and CBZ-EP can be measured with only 250 and 500 microliters of plasma and saliva, respectively. The method, which has been used to determine steady-state concentrations of the drug and its metabolite in paediatric patients receiving CBZ monotherapy, is also suitable for pharmacokinetic studies.

Improved high-performance liquid chromatographic method for the simultaneous determination of caffeine and its N-demethylated metabolites in plasma using solid-phase extraction.

An improved high-performance liquid chromatographic method for the simultaneous determination of caffeine and its N-demethylated metabolites in plasma is described. Excellent resolution of all components is provided by reversed-phase chromatography using a mobile phase consisting of 1% acetic acid-methanol (83:17) at a flow-rate of 2.7 ml/min, in conjunction with a Waters Assoc. Nova-Pak C18 column which was protected by a Waters Assoc. Guard-Pak precolumn module containing a Guard-Pak CN cartridge. Rapid extraction of caffeine and the dimethylxanthines from plasma was achieved using reversed-phase octadecylsilane bonded-silica columns (Bond-Elut C18). With only 100 microliters of sample, plasma levels in the region of 50 ng/ml for the dimethylxanthines and 100 ng/ml for caffeine can be determined using ultraviolet detection at 273 nm. The method has been used for measuring umbilical cord plasma samples to provide information regarding foetal exposure to caffeine and its metabolites and is also suitable for therapeutic drug monitoring of caffeine and theophylline levels in the treatment of neonatal apnoea.

Simultaneous determination of caffeine and its N-demethylated metabolites in umbilical cord plasma using high-performance liquid chromatography.

A convenient high-performance liquid chromatographic method for the simultaneous determination of caffeine and its N-demethylated metabolites in plasma is described. Separation is achieved by reversed-phase chromatography using a mobile phase consisting of 0.01 M sodium acetate buffer, pH 5.0-methanol-tetrahydrofuran (95:4:1) in conjunction with a mu Bondapak C18 column protected by a guard column containing Bondapak C18/Corasil. With a flow-rate of 3 ml/min, levels in the region of 50 ng/ml for the dimethylxanthines and 100 ng/ml for caffeine can be determined by ultraviolet detection at 254 nm. The method was used clinically for measuring cord blood samples to provide information regarding fetal exposure to caffeine and its N-demethylated metabolites during late pregnancy.