(55a) Efficient Tuning of siRNA Dose Response By Combining Mixed Polymer Nanocarrierswith Simple Kinetic Modeling
AIChE Annual Meeting
2016
2016 AIChE Annual Meeting
Liaison Functions
Undergraduate Research Forum I
Sunday, November 13, 2016 - 3:30pm to 3:45pm
silence genes and treat a wide range of genetic diseases. For clinical applications, siRNA must be
encapsulated within nanoscale delivery vehicles to survive in vivo. These nanocarriers must be stable
enough to deliver siRNA into targeted cells while simultaneously releasing siRNA from the nanocarriers
within these cells. Cationic polymers are a promising nanocarrier method for siRNA delivery in which
the polymers electrostatically self-assemble with siRNA to form polyplex structures. However, many
cationic polymer nanocarriers lack efficient siRNA delivery capabilities and controlled release
mechanisms. To regulate siRNA release, our laboratories previously demonstrated the use of photo-
responsive diblock copolymers to provide a method for modulating siRNA release via light-mediated
charge reversal of the cationic polymer block, which breaks apart the polyplex structure and releases
siRNA only upon the photo-stimulus. Herein, we explore the ability to modulate polyplex stability and
gene silencing activity using mixtures of these photo-responsive diblock copolymers with two different
cationic block lengths. The polymer with the shorter cationic block is shown to promote more siRNA
release and form a polyplex smaller in diameter, while the polymer with the longer cationic block is
shown to have increased polyplex stability and increased overall positive surface charge. By mixing the
two polymers, the contradictory demand for stability and release in polyplex systems is addressed, and
the polyplex diameter and surface charge are balanced to enhance uptake into cells. Through
formulation of polyplexes from a 50/50 mixture of the two different diblock copolymer lengths, the level
of gene knockdown easily was optimized to achieve the maximum level of 70% GAPDH protein silencing
for a single dose in NIH/3T3 cells. In addition to maximizing gene silencing by tuning polymer
composition, simple kinetic modeling was employed to create dosing schedules based on siRNA, mRNA,
and protein concentrations in the cells over the dosing process. This modeling allowed an increase to
84% GAPDH protein silencing upon applying a second dose of polyplexes. Thus, this work demonstrates
that pairing advances in biomaterial design with simple kinetic modeling provides new insight into gene
silencing dynamics and a strategy for efficient tuning of polymer composition to maximally control gene
silencing through polyplex siRNA delivery.