Establishment of an in vitro placental barrier model cultured under physiologically relevant oxygen levels.

The human placental barrier facilitates many key functions during pregnancy, most notably the exchange of all substances between the mother and fetus. However, preclinical models of the placental barrier often lacked the multiple cell layers, syncytialization of the trophoblast cells and the low oxygen levels that are present within the body. Therefore, we aimed to design and develop an in vitro model of the placental barrier that would reinstate these factors and enable improved investigations of barrier function. BeWo placental trophoblastic cells and human umbilical vein endothelial cells were co-cultured on contralateral sides of an extracellular matrix-coated transwell insert to establish a multilayered barrier. Epidermal growth factor and forskolin led to significantly increased multi-nucleation of the BeWo cell layer and increased biochemical markers of syncytial fusion, for example syncytin-1 and hCGß. Our in vitro placental barrier possessed size-specific permeability, with 4000-Da molecules experiencing greater transport and a lower apparent permeability coefficient than 70 000-Da molecules. We further demonstrated that the BeWo layer had greater resistance to smaller molecules compared to the endothelial layer. Chronic, physiologically low oxygen exposure (3-8%) increased the expression of hypoxia-inducible factor 1α and syncytin-1, further increased multi-nucleation of the BeWo cell layer and decreased barrier permeability only against smaller molecules (457 Da/4000 Da). In conclusion, we built a novel in vitro co-culture model of the placental barrier that possessed size-specific permeability and could function under physiologically low oxygen levels. Importantly, this will enable future researchers to better study the maternal-fetal transport of nutrients and drugs during pregnancy.

Miniaturized microfluidic formats for cell-based high-throughput screening.

Cell-based high-throughput screening (HTS) has become an important method used in pharmaceutical drug discovery, and is presently carried out using robots and micro-well plates. A microfluidic-based device for cell-based HTS using a traditional cell-culture protocol would be a key enabler in miniaturization and in increasing throughput without consequent detrimental effects on the physiological significance of the screen. In this paper, we illustrate the advances in miniaturization of cell-based HTS, especially using microfabrication and microfluidics. We also detail a novel microfluidic HTS device targeted for cell-based assays using traditional non-compartmentalized agar gel as a cell-culture medium and electric control over drug dose. The basic design of this device consists of a gel layer supported by a nanoporous membrane that is bonded to microchannels underneath it. The pores of the membrane are blocked everywhere except in selected regions that serve as fluidic interfaces between the microchannel below and the gel above. Upon application of an electric field, nanopores start to act as electrokinetic pumps. By selectively switching an array of such micropumps, a number of spots containing drug molecules are created simultaneously in the gel layer. By diffusion, drugs reach the top surface of the gel where cells are to be grown. Based on this principle, a number of different devices can be fabricated using microfabrication technology. The fabricated devices include a single drug spot-forming device, a multiple drug spot-forming device, and a microarray drug spot-forming device. By controlling the pumping potential and duration, spots sizes ranging from 200 mu;m to 6 mm in diameter and having inter-spot distances of 0.4 to 10 mm have been created. The absence of diffusional transport through the nanoporous interfaces without an electric field is demonstrated. A number of representative molecules, including surrogate drug molecules (trypan blue and methylene blue) and biomolecules (DNA and protein) were selected for demonstration purposes. A dosing range of 50 to 3000 mu;g and a spot density of 156 spots/cm2 were achieved. The drug spot density was found to be limited by molecular diffusion in gel, so a numerical study was carried to determine ways to increase density. Based on this simulation, a diffusion barrier was proposed, which uses a specially dimensioned (having shallow grooves) gel sheet to reduce diffusion.

Microfluidic Devices for Automation of Assays on Drosophila Melanogaster for Applications in Drug Discovery and Biological Studies.

Drug discovery is a long and expensive process, which usually takes 12-15 years and could cost up to ~$1 billion. Conventional drug discovery process starts with high throughput screening and selection of drug candidates that bind to specific target associated with a disease condition. However, this process does not consider whether the chosen candidate is optimal not only for binding but also for ease of administration, distribution in the body, effect of metabolism and associated toxicity if any. A holistic approach, using model organisms early in the drug discovery process to select drug candidates that are optimal not only in binding but also suitable for administration, distribution and are not toxic is now considered as a viable way for lowering the cost and time associated with the drug discovery process. However, the conventional drug discovery assays using Drosophila are manual and required skill operator, which makes them expensive and not suitable for high-throughput screening. Recently, microfluidics has been used to automate many of the operations (e.g. sorting, positioning, drug delivery) associated with the Drosophila drug discovery assays and thereby increase their throughput. This review highlights recent microfluidic devices that have been developed for Drosophila assays with primary application towards drug discovery for human diseases. The microfluidic devices that have been reviewed in this paper are categorized based on the stage of the Drosophila that have been used. In each category, the microfluidic technologies behind each device are described and their potential biological applications are discussed.

A Review of Sensing Systems and Their Need for Environmental Water Monitoring.

Water is a valuable natural resource and is needed to sustain human life. Water pollution significantly jeopardizes clean drinking water supplies, it is hazardous to human health, and it inhibits economic development. Well-designed sensors that can continuously monitor water quality during transport and identify contaminants in the watershed help effectively control pollution and thereby manage water resources. However, the commercially available sensors are expensive and require frequent maintenance. These limitations often make these sensors inadequate for continuous water monitoring applications. This review evaluates many sensors based on colorimetric, electrochemical, and optical sensors. Sensors suitable for estimating the amount of dissolved oxygen, nitrates, chlorine, and phosphates are presented. A review of recently developed high quality sensors for measuring the previously mentioned components of water is also presented. Future directions in this area of developing high quality sensors for water monitoring are discussed.

Artificial placenta--lung assist devices for term and preterm newborns with respiratory failure.

Respiratory insufficiency is a major cause of neonatal mortality and long-term morbidity, especially in very low birth weight infants. Today, non-invasive and mechanical ventilation are commonly accepted procedures to provide respiratory support to newborns, but they can reach their limit of efficacy. To overcome this technological plateau and further reduce mortality rates, the technology of an "artificial placenta", which is a pumpless lung assist device connected to the umbilical vessels, would serve to expand the therapeutic spectrum when mechanical ventilation becomes inadequate to treat neonates with severe respiratory insufficiency.
The first attempts to create such an artificial placenta took place more than 60 years ago. However, there has been a recent renaissance of this concept, including developments of its major components like the oxygenator, vascular access via umbilical vessels, flow control, as well as methods to achieve hemocompatibility in extracorporeal circuits. This paper gives a review of past and current development, animal experiments and human case studies of artificial placenta technology.