Abstract
Reconstructing and quantitatively assessing the internal architecture of opaque three-dimensional (3D) bioprinted hydrogel scaffolds is difficult but vital to the improvement of 3D bioprinting techniques and to the fabrication of functional engineered tissues. In this study, swept-source optical coherence tomography was applied to acquire high-resolution images of hydrogel scaffolds. Novel 3D gelatin/alginate hydrogel scaffolds with six different representative architectures were fabricated using our 3D bioprinting system. Both the scaffold material networks and the interconnected flow channel networks were reconstructed through volume rendering and binarisation processing to provide a 3D volumetric view. An image analysis algorithm was developed based on the automatic selection of the spatially-isolated region-of-interest. Via this algorithm, the spatially-resolved morphological parameters including pore size, pore shape, strut size, surface area, porosity, and interconnectivity were quantified precisely. Fabrication defects and differences between the designed and as-produced scaffolds were clearly identified in both 2D and 3D; the locations and dimensions of each of the fabrication defects were also defined. It concludes that this method will be a key tool for non-destructive and quantitative characterization, design optimisation and fabrication refinement of 3D bioprinted hydrogel scaffolds. Furthermore, this method enables investigation into the quantitative relationship between scaffold structure and biological outcome.
Highlights
One of the major challenges in tissue engineering is developing suitable scaffolds that meet the requirements for application in regenerative medicine [1,2]
The LC was designed as a central cylindrical channel (1 mm diameter) with rectangular branches laterally connected to other pores at a defined depth of 1 mm (Fig. 1)
The orientation, shape and width of the laterally connected branch channels can be clearly and intuitively observed in images C2, C4 and C6. 3D observations of the hydrogel polymer matrix segmented from Optical coherence tomography (OCT) images are shown in D1–D6
Summary
One of the major challenges in tissue engineering is developing suitable scaffolds that meet the requirements for application in regenerative medicine [1,2]. Three-dimensional (3D) bioprinting seems to be a promising method to fabricate porous scaffolds in a controllable manner with cell-loaded biomaterials, such as hydrogel [3,4,5]. There remain many challenges in the 3D bioprinting of hydrogels in predesigned geometries because of the poor mechanical properties and complex composition of hydrogels [7,8,9]. The inner architectural features of a scaffold strongly affect cell behaviour and, in turn, the functionality of the engineered tissues [10,11]. There is a need for a high-resolution imaging technique that can penetrate deeply and nondestructively into the 3D bioprinted hydrogel scaffolds
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