The most transparent research

Abstract

Biomedicine would be a breeze if organisms were transparent. With the ability to see through tissues, scientists could spot the development of tumors more easily in study animals. And biologists could study exactly how an animal's organs develop by observing them as they grow. In effect, the secrets of the body would be out there for everyone to see.

The thought of peering into our tissues may sound like science fiction, but one day it could be science. Using ideas from genetics, electrical engineering, chemistry and solid-state physics, a handful of researchers are working on ways to render biological tissues transparent.

Some have already succeeded: in 2007, Richard White, a biologist at the Dana Farber Cancer Institute in Boston, used careful breeding techniques to create a transparent adult zebrafish named casper, evoking a reference to the famous cartoon ghost by the same name. Now, more than 100 labs around the world are using these transparent fish to study cancer pathology and development in real time. “The field of in vivo imaging—looking at things that are happening inside an actual organism—is growing rapidly,” White says.

Researchers are even making strides toward turning human tissue transparent. The primary reason we can't see what's inside of us is that light scatters when it passes through tissue. The body is densely packed with many types of substances, such as bone and fat, and light travels through them at different speeds because they have what physicists refer to as different refractive indices. The result is that light can't pass through biological tissues in a straight line, much as car headlights don't pass through dense fog. To fix this problem, scientists are working on developing ways to stop tissues from scattering light. Indeed, “if you take away the scattering properties of human tissues, we would look more or less like jellyfish,” explains Changhuei Yang, an electrical engineer and bioengineer at the California Institute of Technology.

Though their approaches (described in the following pages) are diverse, these researchers share the common goal of making it one day possible to see what's going on deep inside of the body—a feat that would provide new insights into our biology and help doctors diagnose and treat disease much more easily. “We're trying to push the limits in terms of what can we uncover,” says Bernard Choi, a bioengineer at the University of California–Irvine.