In situ volumetric imaging and analysis of FRESH 3D bioprinted constructs using optical coherence tomography

Abstract

As 3D bioprinting has grown as a fabrication technology, so too has the need for improved analytical methods to characterize engineered constructs. This is especially challenging for engineered tissues composed of hydrogels and cells, as these materials readily deform when trying to assess print fidelity and other properties non-destructively. Establishing that the 3D architecture of the bioprinted construct matches its intended anatomic design is critical given the importance of structure-function relationships in most tissue types. Here we report development of a multimaterial bioprinting platform with integrated optical coherence tomography (OCT) for in situ volumetric imaging, error detection, and 3D reconstruction. We also report improvements to the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) bioprinting process through new collagen bioink compositions, gelatin microparticle support bath optical clearing, and optimized machine pathing. This enables quantitative 3D volumetric imaging with micron resolution over centimeter length scales, the ability to detect a range of print defect types within a 3D volume, and real-time imaging of the printing process at each print layer. These advances provide a comprehensive methodology for print quality assessment, paving the way toward the production and process control required for achieving regulatory approval and ultimately clinical translation of engineered tissues.

Development of a high-performance open-source 3D bioprinter

“…To measure the grid spacing we captured a 3D volumetric image using optical coherence tomography (OCT) (Fig. 4 C) 30 , which revealed close agreement between the as-designed and measured dimensions (Fig. 4 D).…”

“…The 3D reconstruction demonstrates recapitulation of the features of the model and 3D gauging analysis revealed a deviation of − 29 ± 107 µm (mean ± STD) between the FRESH printed ear and the original 3D model (Fig. 4 H) 30 . Together, these two examples demonstrate that the average error and standard deviation of the printed scaffolds are within the mechanical limitations of the bioprinter we built, and on par with commercial bioprinters 31 .…”

“…4 G, Supplementary Fig. S24 ) 30 . The 3D reconstruction demonstrates recapitulation of the features of the model and 3D gauging analysis revealed a deviation of − 29 ± 107 µm (mean ± STD) between the FRESH printed ear and the original 3D model (Fig.…”

“…The second print, the ear scaffold, showed that the bioprinter can produce more complex 3D shapes and the quantitative gauging analysis confirmed that the fidelity achieved using collagen bioink was similar to our published results using other FRESH 3D bioprinters 13 , 14 , 32 . Other important characteristics of FRESH printed collagen constructs, such as stability over time and biocompatibility, have been extensively described in our prior work 13 , 30 , 32 . These examples demonstrate that the converted 3D bioprinter is capable of both accurate motion and high-fidelity printing of the intended geometry.…”

“…3 B–D). Considering that most bioprinter nozzle diameters range from 100 to 500 µm, this will produce high quality results for a wide range of applications 12 , 13 , 30 . While analysis of the motion control system is important, it does not provide a full assessment of bioprinter performance.…”