Organ perfusion techniques in drug development

Drug permeability assay using microhole-trapped cells in a microfluidic device

As orally administered drugs must be absorbed from the intestine into the blood circulation, permeability assays of drug candidates have been widely used in the early screening stages of drug discovery. In this study, a microfluidic device was developed for the drug permeability assay, considering the in vivo delivery path of drugs in humans. A microhole array for cell trapping was fabricated using the poly(dimethylsiloxane) (PDMS) molding technique by mimicking the intestinal epithelial cell membrane. On the basis of mathematical simulations, the configuration of the microfluidic device, including a microhole array and a mixing channel, was optimized to trap cells firmly in each microhole. At the flow rate under optimal conditions, cells were effectively trapped in a microhole array without cell damage. We measured the permeability of 10 drugs, including those with high and low permeability in microchannels, and compared the results with the reported values of permeability in the human and rat intestine. Most drugs had a high p value (p > 0.4), and only a few drugs had a low p value less than 0.05 by t test. Though their measured permeabilities are not the same as those in vivo human intestine, it shows that in vivo permeabilities in the human and rat intestine are highly correlated with those measured by the microfluidic device (R(2) = 0.9013 and R(2) = 0.8765, respectively). Also, the fraction of the dose absorbed in the human intestine (F(a)) indicated that the drug permeability measured using this device was significantly correlated (R(2) = 0.9641) with those in human subjects. As the microfluidic assay system is dependent on cells trapped inside a microhole array, it is a valuable tool in drug discovery as well as an alternative to animal testing.

Development and application of a simplified sample preparation method for determination of TEGDMA and related metabolites

Analysis of biological samples obtained from in vivo experiments can be often challenging. In general it is not possible to apply the commonly used matrices that are necessary for the experiments to the desired analysis systems without further conditioning or sample purification steps. Besides possible adverse effects for instruments, interference between analytes and matrices can affect the correct measurement of analytes. Different methods of sample preparation can be used to convert biological samples into samples suitable for analysis; SPE and HS-SPME are two well established methods. Research of in vivo metabolism of triethyleneglycoledimethacrylate (TEGDMA), one of the most frequently contained comonomer in dental restorative materials, demands sample preparation methods that offer separation of TEGDMA and its related metabolites from biological matrices. In the presented study two methods for sample preparation were developed in order to analyze TEGDMA as well as its metabolites triethyleneglycole (TEG), 2,3-epoxymethacrylicacid methylester (2,3-EMME), and methacrylacid methylester (MAME) in Krebs-Henseleit buffer samples to facilitate a subsequent analysis via GC-MS. An easy and time-saving separation protocol was developed. Recovery rates of TEGDMA and TEG after SPE were 21 +/- 3% and 105 +/- 12%, respectively, recovery rate after headspace extraction of 2,3-EMME and MAME was higher at 48 degrees C compared with 20 degrees C extraction temperature. The tested range for 2,3-EMME and MAME concentration after HS-SPME extraction was 0.1-100 mg/L and both analytes showed a good linearity.

The phenolic compounds of olive oil: structure, biological activity and beneficial effects on human health

The Mediterranean diet is rich in vegetables, cereals, fruit, fish, milk, wine and olive oil and has salutary biological functions. Epidemiological studies have shown a lower incidence of atherosclerosis, cardiovascular diseases and certain kinds of cancer in the Mediterranean area. Olive oil is the main source of fat, and the Mediterranean diet's healthy effects can in particular be attributed not only to the high relationship between unsaturated and saturated fatty acids in olive oil but also to the antioxidant property of its phenolic compounds. The main phenolic compounds, hydroxytyrosol and oleuropein, which give extra-virgin olive oil its bitter, pungent taste, have powerful antioxidant activity bothin vivoandin vitro. The present review focuses on recent works analysing the relationship between the structure of olive oil polyphenolic compounds and their antioxidant activity. These compounds' possible beneficial effects are due to their antioxidant activity, which is related to the development of atherosclerosis and cancer, and to anti-inflammatory and antimicrobial activity.

An ESR contrast agent is transported to rat liver through organic anion transporter

Carboxy PROXYL is a useful extracellular paramagnetic contrast reagent in electron spin resonance (ESR) and magnetic resonance imaging (MRI). Active transfer of the probe was investigated using an in situ liver model in rats. Carboxy PROXYL, a nitroxyl spin probe, was perfused into in situ liver perfusion system from Wistar rats. Concentration of nitroxyl form of the spin probe in effluent increased gradually after introducing perfusate with the spin probe and reached a plateau. The disappearance of Carboxy PROXYL from the perfusate was 40%, which could not be explained with its partition coefficient. Administration of non-selective inhibitors of organic anion transporters, p-aminohippuric acid and penicillin G, inhibited competitively and in a dose dependent manner the transfer of Carboxy PROXYL into rat liver in situ, resulting in increases of Carboxy PROXYL in the effluent. The results demonstrate that there is an active transfer system of an ESR contrast reagent into in situ rat liver through organic anion transporters.

Oleuropein, an antioxidant polyphenol from olive oil, is poorly absorbed from isolated perfused rat intestine

Epidemiological studies have shown that the incidence of heart disease and certain cancers is lower in the Mediterranean region. This has been attributed to the high consumption of olive oil in the Mediterranean diet, which contains polyphenolic compounds with antioxidant activity. Although many in vitro studies have been performed to elucidate mechanisms by which these compounds may act, there are virtually no data relating to their fate after ingestion. Therefore, we decided to investigate the intestinal absorption of one of the major olive oil polyphenolics, oleuropein. To do this, a novel in situ intestinal perfusion technique was developed, and the absorption of oleuropein was studied under both iso-osmotic and hypotonic luminal conditions. Oleuropein was absorbed, with an apparent permeability coefficient (P:(app)) of 1.47 +/- 0.13 x 10(-6) cm/s (+/-SE) observed under iso-osmotic conditions. The mechanism of absorption is unclear but may involve transcellular transport (SGLT1) or paracellular movement. Under hypotonic conditions, the permeability of oleuropein was significantly greater (5.92 +/- 0.49 x 10(-6) cm/s, P: < 0.001). This increase is thought to be due to an increase in paracellular movement facilitated by the opening of paracellular junctions in response to hypotonicity. Overall, we determined that the olive oil polyphenolic oleuropein can be absorbed, albeit poorly, from isolated perfused rat intestine. Therefore, it is possible that it or its metabolites may confer a positive health benefit after the consumption of olive oil, most likely via an antioxidant mechanism.