January 5, 2021
Fibrous proteins such as collagen and fibrinogen form a thin solid layer on the surface of an aqueous solution similar to the “skin” that forms on warm milk, according to a team of Penn State researchers, who believe this finding could lead to more efficient bioprinting and tissue engineering.
In the human body, fibrous proteins provide structural support for cells and tissues and aid in biomechanics. Collagen makes up 80 percent of our skin and 10 percent of our muscles, while fibrinogen helps in blood clotting by forming the hydrogel fibrin.
“Collagen and fibrinogen protein solutions are widely used as precursors of collagen and fibrin hydrogels in tissue engineering applications,” said Hemanth Gudapati, graduate student and teaching assistant in engineering science and mechanics. “This is because collagen and fibrin, which are used as structural materials for tissue engineering similar to their role in the human body, are nontoxic, biodegradable and mimics the natural microenvironments of cells.”
According to information, Mr. Gudapati and fellow researchers report in Soft Matter, for the first time that fibrous proteins form a solid layer on the surface of water due to aggregation of proteins at the air/water interface. This solid layer interferes with accurate measurements of the solution’s rheology, which is the study of fluid properties such as flow. Previously, it was only demonstrated that the other main type of protein, globular proteins, formed these solid layers at the air/water interface.
Accurate rheology measurements are vital for successful bioprinting. Measurement of viscosity is important for identifying what protein solutions are potentially printable, and for detecting inconsistencies in flow behavior among different batches of fibrous proteins.
“Accurate measurement of flow behavior helps in reliable or consistent delivery of the protein solutions during bioprinting,” Mr. Gudapati said. “This helps in the fabrication of things such as reliable organ-on-chip devices and disease models.”
A potential solution for accurate measurement is to add a surfactant such as polysorbate 80 to prevent the formation of film at the air/water interface.
The research also identifies the concentrations of protein solutions which are potentially printable via inkjet bioprinting, along with identifying bioprinting operating parameters.
Mr. Gudapati said there were other findings in their research that will require further investigation. These included the possibility that the aggregated fibrous proteins at the air/water interface may get released from the interface and that these protein aggregates may cause further accumulation of the proteins in the solutions.
Research was supported by the Osteology Foundation in Switzerland, the Hartz Family Career Development Professorship in Engineering and the Penn State Department of Engineering Science and Mechanics.