Considerations on the quantitative analysis of apparent amorphicity of milled lactose by Raman spectroscopy.

The main purpose of the study was to evaluate various pre-processing and quantification approaches of Raman spectrum to quantify low level of amorphous content in milled lactose powder. To improve the quantification analysis, several spectral pre-processing methods were used to adjust background effects. The effects of spectral noise on the variation of determined amorphous content were also investigated theoretically by propagation of error analysis and were compared to the experimentally obtained values.

Combined in vitro-in vivo approach to assess the hepatobiliary disposition of a novel oral thrombin inhibitor.

Two clinical trials and a large set of in vitro transporter experiments were performed to investigate if the hepatobiliary disposition of the direct thrombin inhibitor prodrug AZD0837 is the mechanism for the drug-drug interaction with ketoconazole observed in a previous clinical study. In Study 1, [(3)H]AZD0837 was administered to healthy male volunteers (n = 8) to quantify and identify the metabolites excreted in bile. Bile was sampled directly from the jejunum by duodenal aspiration via an oro-enteric tube.

The degree of compression of spherical granular solids controls the evolution of microstructure and bond probability during compaction.

The effect of degree of compression on the evolution of tablet microstructure and bond probability during compression of granular solids has been studied. Microcrystalline cellulose pellets of low (about 11%) and of high (about 32%) porosity were used. Tablets were compacted at 50, 100 and 150 MPa applied pressures and the degree of compression and the tensile strength of the tablets determined.

Structural features determining the intestinal epithelial permeability and efflux of novel HIV-1 protease inhibitors.

The primary aim of this study was to identify structural features that alter the intestinal epithelial permeability and efflux in a series of novel HIV-1 protease inhibitors (PIs). Eleven PIs were selected containing a tertiary alcohol in a transition-state mimicking scaffold, in which two substituents (R(1) and R(2) ) were varied systematically. Indinavir was selected as a reference compound.

Paracellular porosity and pore size of the human intestinal epithelium in tissue and cell culture models.

The paracellular space defines the passive permeation of hydrophilic compounds in epithelia. The goal of this study was to characterise the paracellular permeation pathway in the human intestinal wall and differentiated epithelial cell models (MDCKII, Caco-2 and 2/4/A1). The permeabilities of hydrophilic polyethylene glycols (PEG) were investigated in diffusion chambers, and mass spectrometry was used to obtain accurate concentrations for each PEG molecule.

CFTR and tight junctions in cultured bronchial epithelial cells.

Airway epithelial salt and water transport takes place through paracellular and transcellular pathways. This transport depends critically on the epithelial sodium channel (ENaC) and the cystic fibrosis transmembrane conductance regulator (CFTR), operating in concert with the paracellular pathway through the tight junctions (TJ). Normal (16HBE14o-), cystic fibrosis (CFBE41o-), and corrected CFBE41o- (CFBE41o-pCep4 overexpressing wtCFTR) airway epithelial cell lines were cultured under isotonic conditions.

Regional levels of drug transporters along the human intestinal tract: co-expression of ABC and SLC transporters and comparison with Caco-2 cells.

A vast number of drugs are subjected to active or facilitated transport and multiple transport mechanism may contribute to the net flux during drug absorption. The main objective of this study was to quantify the regional mRNA expression and determine the co-expression of drug transporters from the ABC (Pgp, BCRP, MRP2, MRP3) and SLC (PEPT1, MCT1, OATPB, OCTN2, OCT1) families along the human intestine (duodenum, jejunum, ileum, and colon). A second objective was to compare the transporter expression between the different intestinal regions and Caco-2 cells.

Caco-2 permeability of weakly basic drugs predicted with the double-sink PAMPA pKa(flux) method.

The aim of this study was to analyze pH-dependent permeability of cationic drugs in Caco-2 cell monolayers using the pK(a)(flux) method and to correlate the results with those obtained in PAMPA (parallel artificial membrane permeability assay). The pH-dependent permeability of verapamil and propranolol was studied in Caco-2 cell monolayers. The data were subsequently processed using software developed for the PAMPA pK(a)(flux) method.

Orally active antiviral tripeptide glycyl-prolyl-glycinamide is activated by CD26 (dipeptidyl peptidase IV) before transport across the intestinal epithelium.

The tripeptide amide glycyl-prolyl-glycinamide (GPG-amide) is a new antiretroviral drug candidate, but its absorption mechanism is unknown. In this investigation, the transport and metabolism of GPG-amide were studied in a model of the human intestinal epithelium, Caco-2 cell monolayers. The results show that when the tripeptide amide came into contact with the apical enterocyte membrane, it was degraded by CD26 (dipeptidyl peptidase IV) to glycylproline and the antiretrovirally active metabolite glycinamide.

Exploring the quantitative relationship between the level of MDR1 transcript, protein and function using digoxin as a marker of MDR1-dependent drug efflux activity.

A limited number of gene expression studies have investigated the quantitative relationships between the amount of transcript, level of protein or activity/function, with disparate conclusions regarding these relationships. Collectively these studies indicate that the relevance of quantitative transcript analysis as a predictor of phenotype has to be evaluated on a gene-by-gene or even a case-by-case basis. The purpose of this study was to define a suitable marker for MDR1-dependent drug efflux, and to quantitatively investigate the relationships between the amount of transcript, protein and drug efflux in the frequently used Caco-2 cell model.

A new principle for tight junction modulation based on occludin peptides.

The aim of this study was to investigate whether peptides from the extracellular loops of the tight junction protein occludin could be used as a new principle for tight junction modulation. Peptides of 4 to 47 amino acids in length and covering the two extracellular loops of the tight junction protein occludin were synthesized, and their effect on the tight junction permeability in Caco-2 cells was investigated using [14C]mannitol as a para-cellular marker. Lipopeptide derivatives of one of the active occludin peptides (OPs), synthesized by adding a lipoamino acid containing 14 carbon atoms (C14-) to the N terminus of the peptide, were also investigated.

Absorption classification of oral drugs based on molecular surface properties.

The aim of this study was to investigate whether easily calculated and comprehended molecular surface properties can predict drug solubility and permeability with sufficient accuracy to allow theoretical absorption classification of drug molecules. For this purpose, structurally diverse, orally administered model drugs were selected from the World Health Organization (WHO)'s list of essential drugs. The solubility and permeability of the drugs were determined using well-established in vitro methods in highly accurate experimental settings.

Determination of transport in the Caco-2 cell assay of compounds varying in lipophilicity using LC-MS: enhanced transport of Leu-enkephalin analogues.

Purpose: To synthesize a number of analogues of Leu-enkephalin with different lipophilicities and to develop an LC-MS method for determining the Caco-2 cell permeability values of these compounds.

Methods: A number of sugar and sugar plus lipoamino acid analogues of Leu-enkephalin were synthesized by solid-phase and solution methods. An LC-MS method was developed for analyzing the Caco-2 cell assay samples and validated against the traditional method using radiolabelled compounds.