Shape Fidelity Evaluation of Alginate-Based Hydrogels through Extrusion-Based Bioprinting

Abstract

Extrusion-based 3D bioprinting is a promising technique for fabricating multi-layered, complex biostructures, as it enables multi-material dispersion of bioinks with a straightforward procedure (particularly for users with limited additive manufacturing skills). Nonetheless, this method faces challenges in retaining the shape fidelity of the 3D-bioprinted structure, i.e., the collapse of filament (bioink) due to gravity and/or spreading of the bioink owing to the low viscosity, ultimately complicating the fabrication of multi-layered designs that can maintain the desired pore structure. While low viscosity is required to ensure a continuous flow of material (without clogging), a bioink should be viscous enough to retain its shape post-printing, highlighting the importance of bioink properties optimization. Here, two quantitative analyses are performed to evaluate shape fidelity. First, the filament collapse deformation is evaluated by printing different concentrations of alginate and its crosslinker (calcium chloride) by a co-axial nozzle over a platform to observe the overhanging deformation over time at two different ambient temperatures. In addition, a mathematical model is developed to estimate Young’s modulus and filament collapse over time. Second, the printability of alginate is improved by optimizing gelatin concentrations and analyzing the pore size area. In addition, the biocompatibility of proposed bioinks is evaluated with a cell viability test. The proposed bioink (3% w/v gelatin in 4% alginate) yielded a 98% normalized pore number (high shape fidelity) while maintaining >90% cell viability five days after being bioprinted. Integration of quantitative analysis/simulations and 3D printing facilitate the determination of the optimum composition and concentration of different elements of a bioink to prevent filament collapse or bioink spreading (post-printing), ultimately resulting in high shape fidelity (i.e., retaining the shape) and printing quality.

Multilayer 3D bioprinting and complex mechanical properties of alginate-gelatin mesostructures

“…Consequently, it can also be used to tune the mechanical properties towards a targeted tissue replacement. The effect of the mesostructure generated through certain print patterns has hardly been studied due to difficulties associated with bioprinting constructs with enough structural integrity 16 , 17 . Consequently, it is essential to ensure high printability and shape fidelity of the hydrogel to tackle these issues.…”

“…Therefore, maintaining a steady flow for a period of time long enough to fabricate 3D structures is highly challenging. As a result, most previous studies have focused on 2D porous constructs of AG hydrogels 17 , 29 .…”

Point‐of‐Care Diagnostic Platforms for Loop‐Mediated Isothermal Amplification

“…The utilization of 3D printers can also facilitate the development of LAMP platforms, as 3D printing enables fast prototyping with minimum knowledge of the micromanufacturing. [172][173][174][175][176] Moreover, quantification of LAMP assays can be a labor-intense task that is prone to human bias. The adoption of machine learning-enabled image analysis methods can increase the LAMP analysis speed and accuracy.…”

Formalin-free fixation and xylene-free tissue processing preserves cell-hydrogel interactions for histological evaluation of 3D calcium alginate tissue engineered constructs

“…Alternatively, ECM proteins such as gelatin or decellularized ECM can be incorporated directly by mixing them with alginate. Their inclusion has recently been shown to reduce swelling of calcium alginate-based hydrogels allowing for longer term and more stable culture (De Santis et al, 2021;Temirel et al, 2022). In order to evaluate whether FF could work in hybrid alginate systems, we fabricated sodium alginate or sodium alginate-gelatin films of 8 mm diameter followed by crosslinking with 50, 200 or 500 mM CaCl 2 solutions to create thin membranes (Li et al, 2016).…”