The influence of viscoelastic properties of bioinks on 3D bioprinted tissue models - A study of cell behaviour and printability
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Biotechnology (MPBIO), MSc
Publicerad
2023
Författare
Ekström, Sofie
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The recent advancement within the field of 3D bioprinting has enabled its appli cation in areas such as the pharmaceutical industry, tissue engineering and many
types of cell-based research. The principle is to utilize 3D printing technology to
print a variety of biomaterials together with viable cells, to produce accurate tissue
models by mimicking the in vivo cell environment. Bioinks used for 3D bioprint ing are commonly composed of hydrogels based on naturally derived polymers like
gelatin, collagen, alginate and nanofibrillated cellulose (NFC). Bioinks are viscoelas tic materials which can be crosslinked after being printed to keep their structure and
shape. The crosslinking method and conditions determine the stiffness of the result ing tissue construct, which can in turn also affect the behaviour of incorporated cells.
This study aims to investigate the influence of the bioink’s viscoelastic properties
on both cell behaviour and printability of the bionink. The studied bioinks include
CELLINK Bioink, GelMA, GelMA C, GelXA and Photogel95, which are crosslinked
either ionically using a CaCl2 solution or using photo-crosslinking, or a combination
of the two.
The bioinks’ viscoelastic properties, as well as stiffness after crosslinking at two
different conditions for each bioink were investigated using rheological measure ments, showing that different stiffnesses could be achieved. 3D bioprinting of the
bioinks with mesenchymal stem cells (MSC) was used to produce samples which
were crosslinked at the same two conditions, cultured over 14 days and analyzed at
several time points. The cell viability was evaluated by fluorescent staining using
Calcein-AM and propidium iodide (PI), and the cell morphology by using Actin Green and DAPI, followed by fluorescent microscopy imaging. The stiffness of the
cell samples over time was also evaluated by measurements at the same time points.
The stiffness of the cell samples over time showed some unexpected results and high
variation between samples, which can to some extent be explained by the method
not being fully suitable and well-adapted for these samples. The cell viability was
relatively high at day 1 for all bioinks and crosslinking conditions, above 90 % for
most samples but around 80 % for a few. A decrease in cell viability was then
observed for all samples at day 7 and day 14. The cell morphology analysis showed
cells spreading in all gelMA-based bioinks at day 7 and day 14, except for Photogel95.
However, no distinct correlations between the stiffnesses achieved at the different
crosslinking conditions and the cell behaviour could be determined.
Beskrivning
Ämne/nyckelord
3D bioprinting, bioinks, viscoelastic properties, rheology, MSC.