Research in the area of cardiac tissue engineering is focused on the development of functional 3-dimensional cardiac muscle tissue in vitro, which includes bioengineered cardiac patches, pumps and ventricles. One of the major challenges in the field of cardiovascular tissue engineering is determining how to support the increased metabolic demands of 3-dimensional tissue constructs, due to the increase in both cellular mass and density compared to monolayer cultures. Traditional culture systems rely on passive diffusion for the delivery of oxygen and soluble factors. However, perfusion systems can provide continuous delivery of cell culture media to 3D tissue constructs, which promotes more active delivery of oxygen, soluble factors, and shear stress, which can be utilized to guide tissue maturation and functional remodeling of bioengineered tissues. We have previously described a perfusion system and demonstrated compatibility over short time periods (similar to hours) with 2-dimensional monolayer cell culture and 3-dimensional tissue constructs. The objectives of our current study were to: introduce CO2 buffering to stabilize media pH in order to achieve long term culture within the system, incorporate sensors capable of recording high media oxygen concentrations, and to increase the culture time of bioengineered heart muscle within the perfusion system in order to increase their functional performance. We showed that exposure of bioengineered heart muscle to perfusion for a period of 24 h increased their functional performance, as measured by cellular viability, total protein, total RNA, spontaneous contractility, twitch force, and specific force. (C) 2008, The Society for Biotechnology, Japan. All rights reserved.