Headlines
As reported by The Hartford Courant, January 25, 2007.
Bioengineering and Biomaterials
By A. Jon Goldberg Ph.D., University of Connecticut Health Center
I’m not sure what got me interested in science, much yet biomaterials. My family moved at the end of my junior year in high school (That was a real bummer, I was dating the captain of the cheerleaders!), then again just before I started college. So, I was looking to be part of a group, any group. That certainly wasn’t the electrical engineering major I blindly selected going into college. However, one advantage of laboratory courses, any laboratory course, is that you get to know people. My chemistry lab teaching assistant seemed decent. Over spilled nitric acid she told me she was a metallurgical engineering major. I had no idea what that was, but metallurgy was small, everyone seemed nice, and I could feel included in this group.
Two years later, Professor Henckel was explaining how the movement of defects in the otherwise pristine crystallographic atomic structure of metals controlled the material’s physical and mechanical properties… and I was hooked. Since then I look at everything—metals, plastics, trees—and see the molecular structure and wonder how it controls strength, translucency, even biocompatibility.
When I went to graduate school, I got involved with designing materials for medical and dental applications. Scientifically, the principles are the same: design the microstructure to achieve the desired bulk and surface properties. However, I had to learn the clinical applications to understand the goals and effectively communicate with the clinicians. Thus, I wandered into the field of biomedical engineering and more specifically, biomaterials.
A New Take On Braces
Working with teams of clinicians, scientists, and other engineers, we have engineered some materials that might be familiar to you. Ever had braces or known someone who does? For a long time, orthodontic appliances were made exclusively with stainless steel. We knew, however, that the devices would be more effective in moving teeth if the material had a lower stiffness and also a higher strength. No problem. Titanium was close to what we needed, but its usual stiffness is too high. However, titanium assumes one of two possible atomic structures, depending on the temperature. The higher temperature body-centered-cubic atomic arrangement can be maintained at room temperature by adding vanadium. (Look at the periodic table of elements and you will see why Ti and V can be readily combined.) The results are referred to as beta-titanium alloys. Adjusting the heating-cooling and wire-drawing processes, gave us beta-titanium wires commonly used in orthodontics today.
New Directions in Biomaterials
In the past, implanted materials were designed to be inert. The biomaterial didn’t adversely affect the body and the body didn’t degrade the implant. One example is a chromium cobalt artificial knee.
The field of biomaterials is now moving toward a new direction: control of molecular-level interactions between materials and the body. The new paradigm for biomedical engineering is to integrate materials and biology at the molecular level. Instead of a distinct “wall” between the implant and the body, the new goal is to create materials that can “signal” the adjacent cells to attach, not attach, or evolve toward a new cell type. In the future damaged cartilage might be regenerated by implanting a porous biomaterial scaffold seeded with stem cells. The surface of the scaffold will be decorated with molecules that instruct the stem cells to evolve towards cartilage. Simultaneously, the scaffold will resorb (dissolve). The end result will be new cartilage with no implant. This new field of regenerative medicine still requires design of microstructures to achieve desired mechanical and biological properties, and it requires a team approach. So, again I’ve found a nice group.