Optimisation of bioprinting protocols for improved tissue formation. A fight against gravity
Publicerad
Författare
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Tissue generation on demand gradually transforms into reality. Generated tissues
can be used for repairing native damaged tissues or be used as tissue models for evaluation
of drug efficiency or toxicity. The microfluidic-based bioprinter Biopixlar,
enables complex tissue generation with high-precision cell positioning. Yet, this
technology could benefit from further optimisation for improved tissue formation.
This project aimed to enhance printability (i.e. ease of viable cell attachment on a
surface) through attempts to decrease the cell sedimentation rate, caused by gravitational
force, within the printhead of Biopixlar. The project intended to exchange
current printing solution (i.e. the solution in which cells are hosted during the
printing process), containing polyethylene glycol (PEG) in phosphate saline buffer
(PBS), to a solution with the non-ionic density gradient medium Histodenz. Mesenchymal
stem cells (hMSCs) were chosen as a model cell line as they are promising
cells, commonly used in regenerative medicine. Biopixlar printability was evaluated
by the number of printed cells, cell viability, uniformity of printed shape and duration
of printing as well as length of the printed pattern. Two printing strategies
was performed, the first where continuous long lines were printed and the second
where pairs of lines where printed with intermediate breaks. By the exchange of
printing solution to Histodenz 12 % [w/v], the printing duration time was improved
by 500-600 %. Furthermore, the shape uniformity and cell count showed increased
stability between measurements when using Histodenz solutions compared to the
current printing solution. In addition, cell viability after exposure to Histodenz was
addressed using cell viability assays (MTS/MTT) on cultured cells supplemented
with live/dead staining of printed cells. The results indicate 66-83 % cell viability,
which is lower than usually obtained with currently used printing solution (over 95
%). However, these results were generated in extreme conditions (printing time)
and therefore require further investigation and optimisation. In conclusion, the use
of Histodenz solution 12 % [w/v] improved Biopixlar printing of hMSCs and were
considered superior over PEG solution, regardless of observed reduced cell viability.
Beskrivning
Ämne/nyckelord
printability, mesenchymal stem cells, Histodenz, polyethylene glycol, printing solution, bioprinting