Interfacial flow processing of collagen.

A new method for creating substrates made out of ordered collagen fibers, on which cells in culture can align, is proposed. The substrates can be used for research in cell culture, and this research presents a significant advance in the technology to coat implants in order to improve cell adhesion. In the procedure presented here, a molecular solution of collagen is spread at the interface of a saline solution and air to induce fiber formation, compressed at a high speed to induce orientation and deposited on solid substrates via Langmuir-Blodgett transfer. Several interfacial techniques are employed to investigate the behavior of collagen, which is shown to be dependent on the salt concentration of the subphase as well as the temperature. After Langmuir-Blodgett transfer, primary human fibroblasts and adipose-derived stem cells are cultured on the collagen substrates. Both types of cells respond favorably to the collagen orientation and align with the deposited fibers. The technique presented here provides a simple method to produce well-controlled, oriented collagen substrates that can be used in tissue culture research or scaffolding applications without the use of additives and/or bioincompatible materials.

Lung surfactant gelation induced by epithelial cells exposed to air pollution or oxidative stress.

Lung surfactant lowers surface tension and adjusts interfacial rheology to facilitate breathing. A novel instrument, the interfacial stress rheometer (ISR), uses an oscillating magnetic needle to measure the shear viscosity and elasticity of a surfactant monolayer at the air-water interface. The ISR reveals that calf lung surfactant, Infasurf, exhibits remarkable fluidity, even when exposed to air pollution residual oil fly ash (ROFA), hydrogen peroxide (H2O2), or conditioned media from resting A549 alveolar epithelial cells (AEC). However, when Infasurf is exposed to a subphase of the soluble fraction of ROFA- or H2O2-treated AEC conditioned media, there is a prominent increase in surfactant elasticity and viscosity, representing two-dimensional gelation. Surfactant gelation is decreased when ROFA-AEC are pretreated with inhibitors of cellular reactive oxygen species (ROS), or with a mitochondrial anion channel inhibitor, as well as when A549-rho0 cells that lack mitochondrial DNA and functional electron transport are investigated. These results implicate both mitochondrial and nonmitochondrial ROS generation in ROFA-AEC-induced surfactant gelation. A549 cells treated with H2O2 demonstrate a dose-dependent increase in lung surfactant gelation. The ISR is a unique and sensitive instrument to characterize surfactant gelation induced by oxidatively stressed AEC.