Exploitation of Cationic Silica Nanoparticles for Bioprinting of Large-Scale Constructs with High Printing Fidelity.

3D bioprinting allows the fabrication of 3-dimensional (3D) structures containing living cells whose 3D shape and architecture are matched to a patient. The feature is desirable to achieve personalized treatment of trauma or diseases. However, realization of this promising technique in the clinic is greatly hindered by inferior mechanical properties of most biocompatible bioink materials. Here, we report a novel strategy to achieve printing large constructs with high printing quality and fidelity using an extrusion-based printer. We incorporate cationic nanoparticles in an anionic polymer mixture, which significantly improves mechanical properties, printability and printing fidelity of the polymeric bioink due to electrostatic interactions between the nanoparticles and polymers. Addition of cationic-modified silica nanoparticles to an anionic polymer mixture composed of alginate and gellan gum results in significantly increased zero-shear viscosity (1062 %) as well as storage modulus (486 %). As a result, it is possible to print a large (centimeter-scale) porous structure with high printing quality, whereas the use of the polymeric ink without the nanoparticles leads to collapse of the printed structure during printing. We demonstrate such a mechanical enhancement is achieved by adding nanoparticles within a certain size range (<100 nm), and depends on concentration and surface chemistry of the nanoparticles as well as the length of polymers. Furthermore, shrinkage and swelling of the printed constructs during crosslinking are significantly suppressed by addition of nanoparticles compared to the ink without nanoparticles, which leads to high printing fidelity after crosslinking. The incorporated nanoparticles do not compromise biocompatibility of the polymeric ink, where high cell viability (> 90%) and extracellular matrix secretion are observed for cells printed with nanocomposite inks. The design principle demonstrated can be applied for various anionic polymer-based systems, which could lead to achievement of 3D bioprinting-based personalized treatment.