Characterizing the Process Physics of Ultrasound-Assisted Bioprinting

Parth Chansoria,Rohan Shirwaiker

doi:10.1038/s41598-019-50449-w

Parth Chansoria, Rohan Shirwaiker

Open Access

https://doi.org/10.1038/s41598-019-50449-w

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Abstract

3D bioprinting has been evolving as an important strategy for the fabrication of engineered tissues for clinical, diagnostic, and research applications. A major advantage of bioprinting is the ability to recapitulate the patient-specific tissue macro-architecture using cellular bioinks. The effectiveness of bioprinting can be significantly enhanced by incorporating the ability to preferentially organize cellular constituents within 3D constructs to mimic the intrinsic micro-architectural characteristics of native tissues. Accordingly, this work focuses on a new non-contact and label-free approach called ultrasound-assisted bioprinting (UAB) that utilizes acoustophoresis principle to align cells within bioprinted constructs. We describe the underlying process physics and develop and validate computational models to determine the effects of ultrasound process parameters (excitation mode, excitation time, frequency, voltage amplitude) on the relevant temperature, pressure distribution, and alignment time characteristics. Using knowledge from the computational models, we experimentally investigate the effect of selected process parameters (frequency, voltage amplitude) on the critical quality attributes (cellular strand width, inter-strand spacing, and viability) of MG63 cells in alginate as a model bioink system. Finally, we demonstrate the UAB of bilayered constructs with parallel (0°–0°) and orthogonal (0°–90°) cellular alignment across layers. Results of this work highlight the key interplay between the UAB process design and characteristics of aligned cellular constructs, and represent an important next step in our ability to create biomimetic engineered tissues.

Highlights

While bioprinting is highly effective in recapitulating the macro-geometry of the intended tissues, there is a scope to improve the capabilities to enable biomimicry of tissues’ micro-architectural characteristics
We focus on the bioprinting of constructs with controllable cellular arrays utilizing standing bulk acoustic wave (SBAW) for cell manipulation
Based on the analytical model described above, we investigate key parameters associated with ultrasound-assisted bioprinting (UAB) – excitation mode, frequency, voltage amplitude, transducer-reflector distance, and alignment time – that govern the critical quality attributes of interest within the bioprinted constructs with cellular alignment – cell viability, width of cellular strands, and spacing between adjacent cellular strands

Summary

Introduction

While bioprinting is highly effective in recapitulating the macro-geometry of the intended tissues, there is a scope to improve the capabilities to enable biomimicry of tissues’ micro-architectural characteristics. Www.nature.com/scientificreports surface acoustic wave (SSAW)-based acoustophoresis has been extensively explored from single cell manipulation[30] to creation of cellular patterns with highly defined spatial organizations[29,31,32]. We focus on the bioprinting of constructs with controllable cellular arrays utilizing standing bulk acoustic wave (SBAW) for cell manipulation. We integrate the UAC with a commercial bioprinter (BioAssemblyBotTM) to study the ultrasonically induced alignment of MG63 cells in single and multi-layered extrusion-bioprinted alginate constructs. The cross-patterning UAC consists of two pairs of orthogonally arranged plate-type piezo-transducers and opposing flat glass reflectors (Fig. 1a), which allows the creation of constructs with 0°–90° cellular alignment in alternating layers.

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