Reliable inkjet printing of chondrocytes and MSCs using reservoir agitation

Drop-on-demand (DoD) inkjet printing has been explored for a range of applications, including those to selectively deposit cellular material, due to the high accuracy and scalability of such systems when compared with alternative bioprinting techniques. Despite this, there remain considerable limitations when handling cell suspensions due to the agglomeration and sedimentation of cells during printing, leading to a deterioration in jetting performance. The objective of this work was to design and assess the effectiveness of a custom agitation system to maintain cellular dispersion within the ink reservoir during printing. The cell printing performance of an inkjet printer was assessed with and without the use of a custom agitation system, with biological characterisation performed to characterise the impact of the agitator on cellular viability and function. Cell printing performance was retained over a 2 h printing period when incorporating an agitated reservoir, with a gradual reduction in performance observed under a non-agitated configuration. Cell assays indicated that the agitation process did not significantly affect the viability, metabolic activity or morphology of the mesenchymal stromal cell (MSC) or chondrocyte cell types. This study therefore provides a new methodology to increase process reliability within DoD printing platforms when jetting cellularised material.