Nearly all medical implants and tissue engineered structures (i.e. lab-grown organs) are implanted or grown in a manner where it is difficult to non-destructively assess performance or progress and to make adjustments on the fly. For instance, suppose we wish to engineer a vascular graft to repair a damaged coronary blood vessel. In this case, we would start by taking a scaffold material shaped like a blood vessel and then coating it with endothelial and smooth muscle cells. We would then 'grow' the structure in a bioreactor for a fixed period of time and then implant it into the patient. During this entire process, there are few techniques for assessing the quality and performance of the graft, especially after implantation. In other words, unlike most traditional engineering systems where sensors and feedback processes aid design and monitoring, tissue engineering typically occurs in a 'black box' system. The most common technique for assessing the viability of such structures is to sacrifice the patient and perform histological analysis on the sample. This is not particularly appealing to most patients. I am working on instrumenting standard tissue engineering graft materials with sensors and actuators designed to allow us to actively sense and manipulate tissue engineered structures during their 'growth' phase and, hopefully, through their implanted lifetime. I start with standard tissue engineering graft material--electrospun polymer sheets (high surface area, cell friendly sheets that effectively look and behave like strong paper)--and attempt to incorporate useful devices into them. I am currently looking into muscle engineering where the cells are coated onto my graft sheets. Muscle can be both monitored and actuated electrically from circuits that are embedded within the graft material, while devices such as strain gauges can provide a readout for certain mechanical characteristics of the developing tissue. I am working on creating a hybrid material that incorporates standard tissue engineering scaffold materials (synthetic polymers, collagen, etc.) with standard, planar microfabrication techniques. The result is intended to be an interactive 'graft' material on which cells can be seeded and which can then monitor things like mechanical strain, oxygen consumption and electrical activity and then allow the user (either a physician or a researcher) to make real-time changes such as adjusting electric fields within the material or using on-board microfluidic channels to dose specific chemicals to control cellular behavior. Currently, nearly all materials designed to interact with multicellular systems (tissue engineering scaffolds, culture equipment and medical implants) rely on a hands-off approach. While many sophisticated materials exist that can release drugs over time and change their material properties, few of these systems allow for real-time feedback. Given this, we aim to develop a suite of techniques that allows for active, spatiotemporal manipulation of tissue constructs. Specifically, we are exploring producing scaffolds containing integrated chemical dosing systems capable of programmable chemical factor delivery to specific points in a 3D tissue scaffold.
Project end date: 02/02/11