Thursday, October 17, 2013 3:30 pm
-
3:30 pm
EDT (GMT -04:00)
Mousa
Jafari,
PhD
Post-Doctoral
Fellow
University
of
Waterloo
RNA
interference
is
a
post-transcriptional
gene
silencing
process
whereby
short
interfering
RNAs
(siRNAs)
induce
the
sequence-specific
degradation
of
complementary
messenger
RNA.
Despite
their
promising
therapeutic
capabilities,
siRNA-based
strategies
suffer
from
enzymatic
degradation
and
poor
cellular
uptake.
Several
carrier-based
approaches
have
been
employed
to
enhance
the
stability
and
efficiency
of
siRNA
delivery.
Considering
their
safety,
efficiency,
and
targeting
capabilities,
peptide-based
delivery
systems
have
shown
great
promise
for
overcoming
the
main
obstacles
in
siRNA
therapeutic
delivery.
Peptides
are
versatile
and
easily
designed
to
incorporate
a
number
of
specific
attributes
required
for
efficient
siRNA
delivery.
This
talk
will
focus
on
the
design,
characterization
and
utilization
of
a
new
class
of
amphipathic
peptides
for
siRNA
delivery.
The
study
includes
(i)
designing
amphipathic,
amino
acid
pairing
peptide
sequences
for
siRNA
delivery,
(ii)
in
vitro
experiments
to
evaluate
transfection
efficacy
of
the
designed
peptides,
(iii)
physicochemical
characterization
of
the
interaction
between
peptides
and
siRNA,
and
(iv)
identification
of
the
internalization
pathway
and
kinetics
of
peptide-siRNA
complexes.
Applying
several
biophysical,
thermodynamic,
spectroscopic
and
microscopic
approaches,
the
interaction
of
peptide
with
siRNA
was
characterized.
The
designed
peptides
adopted
a
stable
helical
structure
in
saline
or
upon
co-assembling
with
siRNA,
forming
nano-sized
complexes.
The
complexes
showed
high
gene
knockdown
efficiency
with
very
limited
cyto-toxicity.
It
was
found
that
the
electrostatic
interaction
of
the
peptide-siRNA
complex
with
heparin
sulphate
proteoglycans
at
the
cell
surface
is
required
to
trigger
the
uptake
process.
Using
endocytic
inhibitors,
a
size-dependent
cellular
uptake
mechanism
of
the
complexes
was
revealed.
This
work
provides
essential
information
for
peptide
design
and
characterization
in
the
development
of
peptide-based
siRNA
delivery.