Fiber-Filled Hybrid Hydrogel for Bio-Manufacturing

Extrusion-based three-dimensional (3D) bio-printing deposits cell-laden bio-ink with high spatial resolution and may offer living tissue regeneration. Due to the biocompatibility, very low cytotoxicity, and high-water content, natural hydrogels are commonly considered as the cell-laden bio-ink for scaffold fabrication. However, due to the low mechanical integrity, a large-scale scaffold (>10 layers) with intricate architecture is a challenge. In this paper, we developed and characterized a novel bio-ink consisting of alginate, carboxymethyl cellulose (CMC), and 2,2,6,6 tetramethyl-1-piperidinyloxy (TEMPO)-mediated nanofibrillated cellulose (TO-NFC) for bio-printing applications. The potential of cellulose derivatives in terms of rheological property to satisfy scaffold architecture and cell viability is explored with a relatively small amount of solid content (<5%). By combining alginate, CMC, and TO-NFC as a hybrid hydrogel, we design to overcome their individual challenges as bio-ink. At the design stage, we have considered two main characteristics: printability and shape fidelity with quantitative indices following their rheological characteristics. Our proposed hydrogel blend (5% solid content) demonstrates a 0% collapse rate for 3-mm pillar distance and 25% fusion rate for 5 mm × 5 mm pore size which can ensure shape fidelity. We fabricated 42 layers and a 9-mm tall scaffold structure with relatively lower applied pressure (10 psi). The proposed hybrid hydrogel is used to prepare bio-ink encapsulating cells, and cell viability is measured as 90% after 10 days of incubation.