Increased delivery efficiency with high cell viability in
serpentine device
Nucleofection and viral transduction are effective methods for
intracellular delivery of gene into different cells (Bilal, Vacaflores,
& Houtman, 2015)´(Kebriaei et al., 2016) but because of substantial
reduction in cell viability and recovery of cells using this
conventional transfection methods ,we sought to investigate if
comparable intracellular delivery efficiencies and higher viability
could be achieved via our pattern.
For our proof-of-concept study, we selected an approximately 11.0 kB GFP
construct including anti-BCMA gene to transfect into myeloma cell via
serpentine microfluidic device. We observed an increased level of GFP
expression compared to cells processed through nucleofection. (Fig. 2)
To confirm that lower DNA volumes in our pattern is required compared to
nucleofection, various plasmid concentration was applied to the device.
Also, the effects of different speeds were evaluated on the percentage
of GFP positive cells as shown in the diagram (fig 3). Our data showed
that delivery efficiency increased with increasing flow rate across
designed pattern but viability in flow rate of 13 ml/h decreased
compared to lower speeds. However, viability impacts on expression of
critical genes associated with function, we observed that cell viability
and delivery efficiency in 9 ml/h had better results.
GFP expression levels ranging from 19 % to 55.7 % in live cells were
observed approximately 24hours post-transfection, with significant
increase in expression detected in cells processed with different flow
rates. (fig3 A). Interestingly, the GFP expression observed in the live
cell population was linearly correlated with increasing flow rate until
11 ml/h, indicating that the overall expression level of GFP by
augmenting chaotic advection in channel has been enhanced.
While delivery efficiency and viability are important success metrics
for cell engineering, unintended changes to cell phenotype may adversely
impact functional potential. Accompanying the significant decrease in
viability, cell death is remarkable in nucleofected cells and progresses
days after transfection (Zhang et al., 2014).In comparison,
intracellular delivery of gene via our design showed only slight
decreases in cell viability two days after transfection compared to
nucleofection. Quantifying the GFP expression levels in transfected
cells revealed a peak transfection efficiency of 55.7 % when applying
0.5 μg/ml plasmid. (fig3 B) We found that the levels of GFP expression
were significantly higher across all concentrations and speeds compared
to nucleofection. Cumulatively, these results suggest that delivery of
plasmid DNA at various concentration and different flow rates via our
microfluidic device varies the transfection efficiency and cell
viability with optimal levels achieved when delivering 0.5 μg mL−1 DNA
in 9 ml/h speed.