Characterizing the Process Physics of Ultrasound-Assisted Bioprinting

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.

3D Composite Bioprinting for Fabrication of Artificial Biological Tissues

“…Chansoria et al . developed an ultrasound-assisted bio 3D printing technology that used the standing bulk acoustic wave produced by an ultrasonic alignment chamber around the printing platform to arrange the cells in the printed structure to construct single or multi-layer anisotropic cell structure ( Figure 4A )[ 66 ]. Kirillova et al .…”

“…(A) The ultrasonic-assisted extrusion printing with the capacity of no-contact cell arrangement based on the acoustophoretic principle (from ref. [ 66 ] licensed under Creative Commons Attribution 4.0 license). (B) The extrusion printing system combined with the external magnetic field and material component mixing printhead for adjusting the material concentration and particle orientation during printing procedure (from ref.…”

Digitally Fabricated and Naturally Augmented In Vitro Tissues

“…[ 93 ] D) Computer simulation of osteosarcoma cell alignment in 2% w/v sodium alginate using an acoustic frequency of 2 MHz. [ 94 ] Viability staining (green) showing 90% of viable cells both in unaligned and aligned samples. Images reproduced and adapted with permission: (A) [ 90 ] Copyright 2018, the Authors.…”

“…C) In vivo demonstration of nerve cell orientation along magnetically aligned anisotropic microgels [93]. D) Computer simulation of osteosarcoma cell alignment in 2% w/v sodium alginate using an acoustic frequency of 2 MHz [94]. Viability staining (green) showing 90% of viable cells both in unaligned and aligned samples.…”

3D bioprinting of cells, tissues and organs

“…Even though bioprinting enables the homogenous distribution of cells representing the macro-architectural properties, it lacks control of the tissue micro-architecture such as orientation of cells within the bioprinted constructs. Chansoria and Shirwaiker delved deep into the physics of ultrasound-assisted bioprinting (UAB) that utilizes the acoustophoresis principle to align MG63 cells within single and multi-layered extrusion-bioprinted alginate constructs 12 . Cells were aligned both orthogonally and in parallel to the printed filaments, thus mimicking cellular anisotropy in tissues such as ligaments, tendons, and cardiac muscle.…”