Researchers from Vellore Institute of Technology (India) and Shanghai University (China) have developed a bioink from chicken eggs that might be used for Organ 3D printing. The team lead by Murugan Ramalingam from Vellore Institute of Technologyhas recently published a research paper describing their research in the Journal of the Mechanical Behavior of Biomedical Materials.

In their research, the authors have used chicken eggs, which are rich in a protein called albumen primarily found in egg white and human umbilical vein endothelial cells (HUVECs) to create a bioink that could be used to print three-dimensional (3D) human tissueor organ structures. Their aim was to create a bioink capable of printing constructs to house tissue specific cells and to induce vascularization, that is, formation of blood vessels.

Previously, researchers have used a variety of biomaterials to print tissue constructs, however, formation of blood vessels remains a challenge. Bioprinting is the process of printing human tissue equivalents in a 3D printer and like a conventional desktop printer that uses ink, 3D bioprinters utilize special inks called bioinks. Bioinks are the combination of biomaterials, materials that are compatible with human physiology, and cells, the basic unit of life. Bioinks have been around since the early 2000’s and researchers in the field of tissue engineering have been extensively searching for materials & methods that can mimic the natural structure of tissues in our bodies and replicate them in laboratory conditions.

Currently, individuals suffering from end-stage life threatening organ diseases depend on organ transplantation as a therapeutic option. For example,a heart transplant is done for people suffering from cardiovascular diseases.However, there are several challenges which include shortage of organ donors, the risk of organ rejection and lifelong dependency on immunosuppressive medication, resulting in an increase in fatality rate. In order to circumvent these challenges and reduce dependency on organ donation, tissue engineering, a branch of regenerative medicine, attempts to generate tissues and organs outside of the body (laboratory condition) and implanting them to repair the damaged tissues and organs. Tissue engineering employ a scaffold, a temporary structural support environment, which is used to accommodate cells in a 3D space in order to facilitate growth and formation of the desired tissue and organ.

The choice of material is crucial when designing artificial tissuesor organs as any construct not created within the body will be rejected, negating the therapeutic value the construct has to offer. Additionally, the choice of additive biomanufacturing technique also plays an important role. Tissue engineers across the globe believe that 3D bioprinting will be the solution that will reduce dependency on organ donations as bioinks can be customized to be patient specific using their own cells (stem cells, for example) and reducing the risk of rejection and the 3D bioprinting offers the ability to print complex scaffolding network at the microscopic scale.

Proteins are essential micronutrients required for normal body function and certain types of protein that forms a scaffold where cells reside and give organs their strength and structure are found abundantly in our body. Protein based bioinks are being considered as desirable biomaterials as they offer intrinsic and tunable properties such as biocompatibility, biodegradability and nontoxicity with applications in a wide range of tissue structures. Aside from compatibility, cells naturally grow and spread when they are in familiar native-like environment and research has shown that this aspect plays an important role in the proliferation and differentiation of cells to specific lineages.

In their natural state, nature derived biomaterials display excellent biocompatibility but poor printability and thus require enhancements. The authors of this research paper combined sodium alginate (NaAlg), a natural polysaccharide found in brown algae, and albumen from egg whites, and incorporated them with HUVECs, which are a type of cell responsible for the formation of blood vessels. NaAlgexhibits properties such as non-toxicity, biodegradability, and biocompatibility, however in its pure form, alginate-based bioinks are inert hydrogels that inhibits cell adhesion. To overcome this challenge, bioactive materials such as albumen can be considered as a unique admixture function for tissue scaffolds and are incorporated with the NaAlgto enhance its properties. Albumen has versatile functional properties, including biocompatibility, anti-bacterial, anti-hypertensive, anti-inflammatory and cell growth stimulatory properties.

All tissues and organs in our body are supplied with oxygen and nutrients, and removal of cellular waste products via blood which travels in blood vessels. The formation of blood vessels in engineered constructs is crucial to ensure that the construct works as intended and becomes autologous. In their research, the team explores various ratios of NaAlgand albumen concentrations and reported that the cells maintained high cell viability on the composite scaffolds and conduce to stimulate endothelial sprouting and interconnected vessel network formation after culturing for a few days. 

Altogether, the results of this study imply that the 3D printed Albumen/NaAlg composite scaffolds have great potential in tissue and organ engineering, especially for inducing vascularization within the engineered biological system.

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