Creating perfusable channels in tissue with embedded printing

To supply cells with nutrients and oxygen and remove metabolic waste, tissue needs to contain perfusable channels. These channels become especially important when engineering thick tissues for human implantation or as a platform for in vitro testing.

Ren et al. studied embedded printing methods and three different representative sacrificial materials for creating perfusable channels.

Embedded printing uses a container filled with a crosslinkable and yield-stress matrix bath. The material is non-Newtonian, acting as a solid when still and turning liquidlike with applied pressure. The researchers printed patterns inside the bath with sacrificial inks, which were eventually removed to leave perfusable channels in thick tissues.

The team tested three sacrificial materials commonly used for bioprinting. The inks had different properties like thermoreversibility or water solubility, which allowed them to be physically removed.

“We studied this based on three different physical metrics,” said author Yong Huang. “First, printability, or can we print a sacrificial channel pattern inside the matrix bath? The second is whether these materials will diffuse into the matrix bath or vice versa, which affects the channel formation performance. The third metric is based on if we can remove the sacrificial materials to form channels easily.”

The sacrificial ink with shear-thinning properties allowed for channels with a broader range of diameters. Because the bath and the inks were aqueous, there was diffusion of the bath into the channel pattern and vice versa. Inks and bath materials with a low diffusion coefficient minimized this effect.

In the future, the authors aim to model the channel diameter and diffusion, as well as engineer multiscale thick vascularized tissues inside the bath.

Source: “Study of sacrificial ink-assisted embedded printing for 3D perfusable channel creation for biomedical applications,” by Bing Ren, Kaidong Song, Anil Reddy Sanikommu, Yejun Chai, Matthew A. Longmire, Wenxuan Chai, Walter L. Murfee, and Yong Huang, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0068329 .