Bioinks

Bioinks are materials that mimic an extracellular matrix environment to support the adhesion, proliferation, and differentiation of mammalian cells. Bioinks distinguish themselves from traditional biomaterials such as hydrogels, polymer networks, and foam scaffolds due to their ability to be deposited as filaments during an additive manufacturing process. Additionally, unlike traditional additive manufacturing materials such as thermoplastic polymers, ceramics, and metals which require the use of harsh solvents, cross-linking modalities and high temperatures to be printed, bioinks are processed under much milder conditions. These mild conditions are necessary to preserve compatibility with living cells, and prevent degradation of bioactive molecules and macroproteins. These bioinks are often adopted from existing hydrogel biomaterials and derived from natural polymers such as gelatins, alginates, fibrin, chitosan, and hyaluronic acids that are sensitive to their processing conditions.

Unlike the thermoplastics that are often utilized in traditional 3D printing, the chain entanglements and ionic interactions within the hydrogel-like bioink rather than temperature dominate shape fidelity. The natural derivation of many bioinks often results in a high water content and sensitivity to harsh processing conditions. Therefore, bioink filaments are often deposited at or below human body temperature and under mild conditions to preserve bioink printability. Additional considerations must be taken into account when printing bioinks blended with a cell suspension due to the need to preserve cell viability.

Differences from traditional 3D printing materials

Bioink compositions and chemistries are often inspired and derived from existing hydrogel biomaterials. However, these hydrogel biomaterials were often developed to be easily pipetted and cast into well plates and other molds. Altering the composition of these hydrogels to permit filament formation is necessary for their translation as bioprintable materials. However, the unique properties of bioinks offer new challenges in characterizing material printability. Unlike traditional 3D printing materials such as thermoplastics that are essentially ‘fixed’ once they are printed, bioinks are a dynamic system due to their high water contains and often non-crystalline structure. The shape fidelity of the bioink after filament deposition must also be characterized. Finally, the printing pressure and nozzle diameter must be taken into account to minimize the shear stresses placed on the bioink and on any cells within the bioink during the printing process. Too high shear forces may damage or lyse cells, adversely affecting cell viability.

...
Wikipedia