(256g) Optimization of Cationic Nanogel Composition for Enhanced Co-Delivery of siRNA and Chemotherapeutics

Authors: 
Spencer, D. S., The University of Texas at Austin
Luu, B. C., The University of Texas at Austin
Peppas, N. A., University of Texas at Austin
Beckman, D. W., The University of Texas at Austin
Off-target toxicity and multi-drug resistance are two major limitations of current chemotherapeutic regimens as they lead to poor quality of life and low survivability. Targeted co-delivery of siRNA and chemotherapeutics offers a promising strategy to sensitize and kill cancer refractory to currently employed therapeutic regimens while minimizing side-effects. Here, we studied cationic nanogels as carriers of siRNA and chemotherapeutics for intracellular therapeutic delivery.

Biodegradable cationic nanogels were synthesized in an oil-in-water emulsion via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) of methacrylate monomers. The ratio of hydrophobic/hydrophilic (tert-butyl methacrylate, 2-hydroxyl ethyl methacrylate, and 2-aminoethyl methacrylate) and aromatic (benzyl methacrylate) character versus overall cationic character of nanogels (2-(diethylamino)ethyl methacrylate) was systematically modulated to enhance therapeutic co-loading of siRNA and doxorubicin through balance of electrostatic, hydrogen bonding, hydrophobic, and aromatic interactions. Biodegradability was imparted through a disulfide crosslinker and ligand conjugation was conducted through carbodiimide chemistry.

Composition was verified using infrared spectroscopy and differences in tertiary amine content, volume swelling ratio, apparent surface charge, and dry size were analyzed using potentiometric titration, dynamic light scattering, zeta potential, and electron microscopy. Co-loading was optimized with respect to pH, ionic strength, and N/P ratio and compared with nanogel composition and volume swelling ratio. Material cytocompatibility in cancerous and healthy cell lines and a hemolysis assay were utilized to identify toxicity thresholds and optimal nanogel critical swelling pH. Transfection and cytotoxicity of loaded nanogels were investigated in vitro in drug resistant cell lines to demonstrate the co-delivery potential of this nanogel platform.