Advances in 3D printing have led to new ways to make bone and some other relatively simple body parts that can be implanted in patients. But finding an ideal bio-ink has stalled progress toward printing more complex tissues with versatile functions, for example, tissues that can be loaded with pharmaceuticals.
Most inks currently being developed for 3D printing are made of thermoplastics, silicones, collagen and gelatin or alginate. But there are limits to how these inks can be used. For example, the temperatures, pH changes and crosslinking methods that may be required to toughen some of these materials can damage cells or other biological components that researchers would want to add to the inks. Additives, such as cytokines and antibiotics, are useful for directing stem cell functions and controlling infections, respectively. To address these limitations, David L. Kaplan and his colleagues turned to silk protein to develop a way to avoid these harsh processing conditions.
The researchers combined silk proteins, which are biocompatible, and glycerol, a non-toxic sugar alcohol commonly found in food and pharmaceutical products. The resulting ink was said to be clear, flexible, stable in water, and didn't require any processing methods that would limit its versatility.
