1 research outputs found
Oxygen-Purged Microfluidic Device to Enhance Cell Viability in Photopolymerized PEG Hydrogel Microparticles
Encapsulating
cells within biocompatible materials is a widely
used strategy for cell delivery and tissue engineering. While cells
are commonly suspended within bulk hydrogel-forming solutions during
gelation, substantial interest in the microfluidic fabrication of
miniaturized cell encapsulation vehicles has more recently emerged.
Here, we utilize multiphase microfluidics to encapsulate cells within
photopolymerized picoliter-volume water-in-oil droplets at high production
rates. The photoinitiated polymerization of polyethylene glycol diacrylate
(PEGDA) is used to continuously produce solid particles from aqueous
liquid drops containing cells and hydrogel forming solution. It is
well understood that this photoinitiated addition reaction is inhibited
by oxygen. In contrast to bulk polymerization in which ambient oxygen
is rapidly and harmlessly consumed, allowing the polymerization reaction
to proceed, photopolymerization within air permeable polydimethylsiloxane
(PDMS) microfluidic devices allows oxygen to be replenished by diffusion
as it is depleted. This sustained presence of oxygen and the consequential
accumulation of peroxy radicals produce a dramatic effect upon both
droplet polymerization and post-encapsulation cell viability. In this
work we employ a nitrogen microjacketed microfluidic device to purge
oxygen from flowing fluids during photopolymerization. By increasing
the purging nitrogen pressure, oxygen concentration was attenuated,
and increased post-encapsulation cell viability was achieved. A reaction-diffusion
model was used to predict the cumulative intradroplet concentration
of peroxy radicals, which corresponded directly to post-encapsulation
cell viability. The nitrogen-jacketed microfluidic device presented
here allows the droplet oxygen concentration to be finely tuned during
cell encapsulation, leading to high post-encapsulation cell viability