Optimization of guar gum-gelatin bioink for 3D printing of mammalian cells

Abstract

Bioprinting, as a fabrication technique, has witnessed significant progress over the past decade. Therefore, the development of bioink is crucial for the success of bioprinting as the process is governed by the properties of biomaterials used in bioink. Due to the lack of standards, only a limited number of bioinks are available, because of which direct comparison between two bioinks is not possible. This is the biggest hurdle in the advancement of extrusion-based bioprinting. This study focuses on providing a standard method for bioinks by analyzing the effect of storage modulus (G′), loss modulus (G″), tan ∂ (G”/G′), and bloom strength on their printability. A new economical bioink comprising gelatin and different concentrations of guar gum (a plant-based biopolymer) was studied. Guar gum is water soluble and is known for its ability to form highly viscous solutions even at lower concentrations. This new combination of biopolymer was formulated to obtain a broad range of bloom strength, G′ and G”. Tan ∂ was calculated using G’ and G”, followed by bloom test. These physical parameters were correlated with the printability of bioink, after evaluation of filament formation. Results suggested that the guar gum-gelatin bioinks having bloom strength in the range of 480–750 and tan ∂ in the range of 0.15–0.2, were able to form filament upon extrusion and were therefore considered as printable. Compared to oscillatory shear tests, the bloom test is a rapid and easy analytical technique for predicting the printability of bioinks. Cell examination is difficult when the scaffold possesses autofluorescence; hence two different assays were employed, viz. The live/dead assay and staining with Hoechst nuclear stain for analysis of the bioprinted cells. Apart from the bioink characterization, the methodology employed in this investigation can be used as a standard to analyze the printability of other extrusion-based bioinks.