Tissue Engineering

Organ and tissue loss or failure becomes more and more critical all over the world. Due to the shortage of the organ donors and the development of micro fabrication technology, engineering constructed tissue sources have attracted much more attention than before. Culturing tissue in vivo or in vitro based on patient’s cells is the most attractive way, since there is no foreign body reaction. However due to the lack of microcirculatory system at the earlier stage of the culture, no matter in vitro or in vivo, there is only very limited success. The time scale for revascularization happens is order of days (even with growth factors) and the time scale for cell death from hypoxia is order of hours. Therefore without capillary perfusion, the metabolism during cell growth cycle will eventually exhaust the supply of nutrient and oxygen from the external environment and the embedded cells suffer from the lack of nutrients, creating a bottleneck for the growth of thick (>1mm scale) 3D tissues. Studies confirm that the cells in the tissue are poorly cultured when they are further than ~400mm from the external nutrient source. As a matter of fact, in real tissue, almost all the cells stay within 100um distance from the nearby capillaries. In this project, we are trying to use artificial vascular bed to culture microvascular system and further 3d tissue in vitro. The micro vascular bed has same dimensions of real capillaries system. It is made of biocompatible materials, synthetic or natural. The micro fabrication technology supporting this project is called Projection Micro Stereolithorgraphy. It builds micro structure in a layer by layer manner. This technology has good resolution (<5um), is compatible with many biomaterials and is a 3D micro fabrication method.

Figure 1. Micro fabricated structures