Speaker
Description
Introduction
Embedded bioprinting enables the deposition of bioinks within a supportive matrix, traditionally composed of viscoplastic gels. While these materials offer mechanical stability, they often compromise nutrient and oxygen transport to embedded cells [1]. To address these limitations, our group introduced in-foam bioprinting, a novel approach that utilizes a nutrient-rich, albumin-based foam as the support medium [2]. Despite its advantages, this albumin-based foam suffers from rapid degradation, limiting its application for longer prints. In this study, the incorporation of pectin as a stabilizing agent to enhance foam stability is investigated. The effects of pectin on foam properties, print fidelity, and cell viability are evaluated to assess its suitability as an improved support material for embedded bioprinting.
Materials and Methods
The foam was prepared by dissolving albumin and pectin powders in DMEM and mechanically mixing at 2000 rpm for 2 minutes (Figure 1A). Three compositions were studied: 8% w/v albumin (Alb8), 8% w/v albumin with 1% w/v pectin (Alb8Pec1) and 8% w/v albumin with 2% w/v pectin (Alb8Pec2). A rheometer with concentric cylinder geometry was used to perform rheological characterizations of the foam. Chitosan 2% w/v with gelling agent (0.1M β-glycerol phosphate, 0.075M sodium hydrogen carbonate) hydrogel was used for printability studies using an extrusion bioprinter and was embedded with L929 fibroblasts for cell studies. The cell-laden bioink was bioprinted into each foam composition as well as a standard gelatin microparticle support bath as used in Freeform Reversible Embedding of Suspended Hydrogels (FRESH) bioprinting [1] to ensure and compare cell viability. All cell viability tests were measured through live/dead assays using calcein and ethidium homodimer-1 to stain the live and dead cells respectively. The dissolved oxygen levels of the support baths were measured over time using a non-invasive optical oxygen sensor.
Results and Discussion
The foams containing pectin maintained the important rheological properties required by support baths such as shear thinning behavior and recovery properties (Figure 1B). The addition of pectin increases foam stability in terms of delaying bubble coalescence and liquid drainage when compared to the Alb8 foam presented in our previous work [2] (Figure 1C-F). Low-viscosity and slow-crosslinking chitosan hydrogels were successfully printed in the foams (Figure 1G). Cell-laden constructs printed in the foams containing 1% w/v and 2% w/v pectin exhibited higher cell viability compared to those printed in albumin-only foam (Figure 1H). When compared to FRESH support baths, in-foam bioprinting had higher cell viability when left in the supports for 3 and 5 hours with Alb8Pec1 exhibiting the highest viability overall (Figure 1I). Dissolved oxygen level measurements over time demonstrated that foam supports have slightly higher oxygen levels potentially contributing to their increased viability (Figure 1J).
Conclusions
Pectin enhances foam stability and preserves key support bath properties, while also enabling higher cell viability than conventional methods similar to FRESH. Combined with high dissolved oxygen content, these advantages position in-foam bioprinting as a strong candidate for complex tissue engineering.
References
[1] Shiwarski et al., 2021, APL Bioeng
[2] Madadian et al., 2024, Small Science
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