Modulating rheological characteristics of bio-ink with component weight and shear rate for enhanced bioprinted scaffold fidelity

The study focuses on the formulation of a hybrid hydrogel comprising alginate, carboxymethyl cellulose (CMC), and TEMPO-oxidized nano-fibrillated cellulose (TO-NFC) for bioprinting precise scaffold for tissue engineering applications. Even though controlling the capacity of porosity during scaffold fabrication can positively assist the encapsulated cell growth, the lack of the right material choice and percentage may make it difficult to 3D bioprint scaffold conforming user user-defined porosity, shape fidelity, and cell viability. In our earlier work, we have demonstrated that hybrid-hydrogel made of alginate, CMC, and TO-NFC has shown promising characteristics of bio-ink for tissue scaffold applications [1]. Carefully controlled material composition can help generate the required shear rate in the nozzle to flow the composition smoothly, confirming proper filament width and eventually, defined scaffold porosity. However, achieving the desired rheological property from the composition is an exhaustive process with a series of experiments. Due to their complex behavior after mixing, a predictive viscosity model is necessary. To address that challenge, we propose a multiple linear regression-based model with an adjusted-R² value of 89 % to estimate the viscosity of composition with respect to the weight percentage of alginate, CMC, TO-NFC, and various shear rates. There are 23 unique compositions prepared with various weight percent of Alginate, CMC, and TO-NFC, a comprehensive set of 483 viscosity measurements was obtained. These measurements were collected at 21 distinct shear rate levels, ranging from 0.1 to 100 s⁻¹. We observed while the same solid content can result in a wide range of viscosity by systematically varying the percentage of Alginate, CMC, TO-NFC, and shear rate, similar viscosity levels can also be attained across a range of compositions prepared with varying solid contents of them. After a 10-day incubation period, we assessed the morphology and viability of Porc1 cells encapsulated in one of the 23 compositions, revealing a significantly higher percentage of viability at 89 %. This fine-tuning of rheological properties by varying percentages and shear rates enhances the accuracy and fidelity of the printed scaffold, ensuring a realistic representation of the desired scaffold architecture. Such a predictive model can help prepare bio-ink with relative ease and a smaller number of experiments which can help expedite the development of new bio-ink for bio-printing applications.