Reaching Tissue Engineering, Layer by Layer

Sherwin Yu | sherwin.yu@yale.edu December 11, 2007

The science of tissue engineering has taken another step forward thanks to Professor Paul Van Tassel’s latest investigations in the Yale Department of Engineering.

At the Tassel lab, ongoing research is focused on creating multilayer nanofi lms that integrate biomaterials, from which cells can receive chemical signals. Multilayer nanofi lms, typically only a few nanometers thick, “may serve as [hosts] to biological molecules when the goal is to induce a cellular response,” explains Tassel.

Cells receive signals through various biological recognition sites at the cell surface. Biomaterials— substances capable of copying cellular signals— are integrated into multilayer fi lms. Among the many biomaterials incorporated, fi bronectin (an extracellular matrix protein) is particularly important due to its role in cell attachment and spreading.

Nanofilms are made layer-by-layer, alternating positively-charged and negatively-charged layers. Each layer is composed of biodegradable polymers that are biological in origin to better meet the structural, mechanical, and degradation requirements for biomaterials and for compatibility in living systems.

Tassel’s research takes a step forward from previous fi bronectin-integrated nanofi lm studies because it accounts for the number of layers, terminal layer charge, fi bronectin adsorption of the fi lm, and the rates of cell spreading. Phase contrast optical microscopy helped analyze how human umbilical vein endothelial cells attached to and spread across multilayer fi lms. Test results have also shown that fi bronectin tends to adsorb strongly to fi lms ending with a positively-charged layer. In turn, cells spread farther and more evenly across fi lms that were coated with fi bronectin.

“Tissue engineering—where one seeks to create cellular constructs to replace diseased or damaged tissues—requires material scaffolds to support cell growth and development,” says Tassel. “Multilayer nanofi lm biomaterials, rendered bioactive via incorporation of biomolecules such as fi bronectin, show great promise in directing cell proliferation toward desired tissue structures.”