Branched vascular network architecture: a new approach to lung assist device technology.

OBJECTIVE: A lung assist device would serve an important clinical need as a bridge to transplant or destination therapy for patients with end-stage lung disease. A new lung assist device has been developed that incorporates a branched network of vascular channels adjacent to a gas chamber, separated by a thin, gas-permeable membrane. This study investigated 2 potential gas exchange membranes within this new architecture. METHODS: Oxygen and carbon dioxide exchange within the device was tested in vitro using 3 gas-permeable membranes. Two of the membranes, silicone only and silicone-coated microporous polymer, were plasma impermeable. The third, a microporous polymer, was used as a control. Gas exchange testing was done using anticoagulated porcine blood over a range of flow rates. RESULTS: Oxygen and carbon dioxide transfer was demonstrated in the device and increased nearly linearly from 0.6 to 8.0 mL/min blood flow for all of the membranes. There was no significant difference in the gas transfer between the silicone and the silicone-coated microporous polymer membranes. The transfer of oxygen and carbon dioxide in the device was similar to existing hollow fiber oxygenators controlling for surface area. CONCLUSIONS: The silicone and silicone-coated microporous polymer membranes both show promise as gas-permeable membranes in a new lung assist device design. Further optimization of the device by improving the membranes and reducing the channel diameter in the vascular network will improve gas transfer. The current device may be scaled up to function as an adult lung assist device.

Microfabrication of three-dimensional engineered scaffolds.

One of the principal challenges facing the field of tissue engineering over the past 2 decades has been the requirement for large-scale engineered constructs comprising precisely organized cellular microenvironments. For vital organ assist and replacement devices, microfluidic-based systems such as the microcirculation, biliary, or renal filtration and resorption systems and other functional elements containing multiple cell types must be generated to provide for viable engineered tissues and clinical benefit. Over the last several years, microfabrication technology has emerged as a versatile and powerful approach for generating precisely engineered scaffolds for engineered tissues. Fabrication process tools such as photolithography, etching, molding, and lamination have been established for applications involving a range of biocompatible and biodegradable polymeric scaffolding materials. Computational fluid dynamic designs have been used to generate scaffold designs suitable for microvasculature and a number of organ-specific constructs; these designs have been translated into 3-dimensional scaffolding using microfabrication processes. Here a brief overview of the fundamental microfabrication technologies used for tissue engineering will be presented, along with a summary of progress in a number of applications, including the liver and kidney.