Poly-L-Lysine Doped FmocFF Nanogels as Delivery Platforms for siRNA

Cationic nanogels (NGs), obtained by combining the low molecular weight peptide hydrogelator Fmoc-FF with poly-l-Lysine (PLL, MW ∼24,000 Da), have been evaluated as potential tools for effective delivery of short interfering RNA (siRNA) into cells. Mixed hydrogels composed of FmocFF in combination with PLL in increasing amount (from 1.0 to 7.0 mg/mL) were formulated through a solvent-switch method and characterized in terms of their mechanical properties, loading capabilities, and stability. Injectable NG loaded with cyanine 3-labeled siRNA (siRNA-Cy3) was obtained by a top-down approach through sub-micronization of the macroscopic hydrogel in the presence of polysorbate 80 (Tween 80) and sorbitane monooleate 80 (Span 80) as colloidal stabilizing surfactants. siRNA-Cy3 loading and release were evaluated by fluorescence spectroscopy, with and without a RiboGreen marker, and electrophoresis. NGs, with a hydrodynamic diameter (Dh) of 284 nm and a zeta potential of +31 mV, were found to be able to efficiently encapsulate siRNA-Cy3 (98%) and release it (70% after 72 h) in simulated biological fluids. Preliminary in vitro studies on human embryonic HEK293 kidney cells indicated a safety profile under the experimental conditions and validated the capacity of NG formulation to be internalized by active endocytic processes. Cationic polypeptide based NGs are promising nanoplatforms for the active delivery of siRNA.