Open AccessThe Influence of Printing Parameters and Cell Density on Bioink Printing Outcomes
Author(s) -
Gregory J. Gillispie,
Albert Han,
Meryem UzunPer,
John P. Fisher,
Antonios G. Mikos,
M. Khalid Khan Niazi,
James J. Yoo,
Sang Jin Lee,
Anthony Atala
Publication year - 2020
Publication title -
tissue engineering. part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.964
H-Index - 111
eISSN - 1937-335X
pISSN - 1937-3341
DOI - 10.1089/ten.tea.2020.0210
Subject(s) - volumetric flow rate , materials science , rheology , limiting , screen printing , composite material , cell size , biomedical engineering , nanotechnology , mechanical engineering , engineering , mechanics , physics , biology , microbiology and biotechnology
Bioink printability persists as a limiting factor toward many bioprinting applications. Printing parameter selection is largely user-dependent, and the effect of cell density on printability has not been thoroughly investigated. Recently, methods have been developed to give greater insight into printing outcomes. This study aims to further advance those methods and apply them to study the effect of printing parameters (feedrate and flowrate) and cell density on printability. Two printed structures, a crosshatch and five-layer tube, were established as printing standards and utilized to determine the printing outcomes. Acellular bioinks were printed using a testing matrix of feedrates of 37.5, 75, 150, 300, and 600 mm/min and flowrates of 21, 42, 84, 168, and 336 mm 3 /min. Structures were also printed with cell densities of 5, 10, 20, and 40 × 10 6 cell/mL at 150 mm/min and 84 mm 3 /min. Only speed ratios (defined as flowrate divided by feedrate) from 0.07 to 2.24 mm 2 were suitable for analysis. Increasing speed ratio dramatically increased the height, width, and wall thickness of tubular structures, but did not influence radial accuracy. For crosshatch structures, the area of pores and the frequency of broken filaments were decreased without impacting pore shape ( Pr ). Within speed ratios, feedrate and flowrate had negligible, inconsistent effects. Cell density did not affect any printing outcomes despite slight rheological changes. Printing outcomes were dominated by the speed ratio, with feedrate, flowrate, and cell density having little impact on printing outcomes when controlling for speed ratio within the ranges tested. The relevance of these results to other bioinks and printing conditions requires continued investigation by the bioprinting community, as well as highlight speed ratio as a key variable to report and suggest that rheology is a more sensitive measure than printing outcomes.