Abstract
Abstract Vascularization of bioprinted constructs to ensure sufficient nutrient supply still remains to be a significant task in the tissue engineering community. In order to mimic functional tissue, it is necessary to be able to print vessels in various size scales, which places particularly high demands on the 3D printing technology and materials. In this preliminary study, we focused on the production of small hollow structures for the application in small functional units of living tissue. To fabricate hollow structures, the freeform reversible embedding of suspended hydrogels (FRESH) - method was utilized (Hinton et al.). A sodium alginate solution (5 % w/v) was used as a bioink. The scaffolds were fabricated with the Allevi 1 (Allevi Inc., PA, USA), a pneumatic extrusion-based bioprinter and plotted into a gelatine slurry serving as fugitive support. For first cell experiments, the bioink was loaded with immortalized mouse HL1-cells. A proof of concept could be shown since we were able to reliably create vessel-like structures with an inside diameter of 1.2 to 1.6 mm, a length of up to 8 mm and a wall thickness of 0.4 to 0.6 mm. In this study, the geometric requirements to print hollow structures for small functional tissues could be achieved. To expand the field of applications the resolution of the printing process has to be further improved. Moreover, the cell density should be increased to reach physiological cell numbers and extended with endothelial cells.
Highlights
The application of microfabrication techniques and 3D printing recently gained great attention in the medical, scientific community [1]
The idea of using 3D printing devices to engineer tissue or organs as mimicking substitutes for the native ones is promising and ambitious at the same time. Besides many challenges, such as cell density or the mechanical integrity of the scaffolds, one of the biggest challenges remains the supply of the cells with necessary nutrients
The construction of a vascular system consisting of microchannels is becoming indispensable and is in the focus of several studies applying different techniques ranging from the maturation of vessels in vitro to directly 3D printing of microchannels [3]
Summary
The application of microfabrication techniques and 3D printing recently gained great attention in the medical, scientific community [1]. Smaller vessels for the supply of small structural subunits of organs, such as nephrons or liver lobules, or in vitro tumor models are difficult to fabricate due to the special demands on the material and the accuracy of the manufacturing process [4–6]. In this preliminary study we present first results for the production of small hollow structures on the basis of extrusion-based bioprinting into a gelatine support bath using freeform reversible embedding of suspended hydrogels (FRESH) [7]. A cell-incorporated bioink was prepared to investigate cell viability after finishing the 3D printing process Both inks are based on an aqueous sodium alginate solution (5% w/v). One day after printing the LIVE/DEADTM Viability/Cytotoxicity Kit (Thermo Fisher Scientific, Waltham, USA) for mammalian cells was accomplished according to manufacturer's instructions and analyzed using the ELYRA PS. 1 LSM 780 confocal microscope (Carl Zeiss, Jena, Germany)
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