Growing cellular tissue may be done in 2 dimensional space (or a 3-D space that involves only a very short 3rd dimension, just short of a millimeter), but more complex items require the use of all three dimensions. Joseph Hoffman (PhD candidate) and Dr. Jennifer West [Rice, Bioengineering chairperson] described improvements enabling the use of a polyethylene glycol (PEG) hydrogel, which is engineered to mimic the human’s extracellular matrix. (The extracellular matrix provides support to the body, comprised of proteins and polysaccharides, forming the basis for connective tissue.) Their development of a “two-photon lithography” process was described in the November issue of SoftScience. This afforded them the ability to exert control and create intricate 3D patternsi a heterogeneous environment, to insure cells grow and move where the scientist desires. Their process afforded them the ability to define patterns within the hydrogel that ranged in size from 1 µm to nearly 1 mm.
This breakthrough was used byBlood vessel formation over time (red)Blood vessel formation over time (red) another Rice team to develop procedures to grow blood vessels and capillaries. Drs. West and Dickinson, along with PhD candidates Gould & Saik, and undergraduate Watkins reported on this development in Acta Biomateriala. The research involved “salting” the PEG with two kinds of cell types that are critical for blood vessel formation, along with growth factors. The hydrogel serves as a “scaffolding” to hold materials in place and control drug delivery rates. In this case, the immobilization within the hydrogel was critical because platelet derived growth factor has a very short lifespan in circulating blood (some 30 minutes). The bioengineered vessels were injected into mice cornea, where blood flow could be observed. (Mice cornea lack vasculature; any blood flow had to be the result of the injected hydrogels.)
The goal of this research is to provide blood circulation to organs harvested for transplantation. Currently, these organs are transported under ice to facilities where the chosen candidate is awaiting the organ. The inclusion of the hydrogel will afford continued nourishment for the organ during transport.
