NOVEL BORONATED POLYAMIDOAMINES AS MULTIFUNCTIONAL VECTORS FOR siRNA DELIVERY

NOVEL BORONATED POLYAMIDOAMINES AS MULTIFUNCTIONAL VECTORS FOR siRNA DELIVERY In this project an entirely novel approach is followed to obtain a next generation of polymeric siRNA vectors that can be easily and flexibly modified in order to meet the specific requirements for extracellular polyplex stabilization, blood compatibility, avoidance of immune interference, cell targeting, and effective release of siRNA in the cytosol. The novel generation of vectors is based on biodegradable disulfide-linked poly(amido amine) polymers (PAA/SS polymers) provided with boronic acid functionalities in their side chains. As it was found in previous work that PAA/SS polymers show good transfection properties and are readily degraded under the reductive conditions in the endosomes, these water-soluble, biodegradable polymers form an excellent starting point for smart functionalization with boronic acid groups. Incorporation of boronic acid functionalities in these polymers adds unique chemical properties which open the avenue to serve multiple essential functions for effective delivery of siRNA into the cytosol. The boronic acid group forms stable complexes with 1,2- or 1,3-diol groups, present in many biological compounds, like carbohydrates, glycoproteins, and ribonucleic acids. The fast, reversible, and pH-responsive formation of these complexes provides excellent possibilities to exploit the boronic acid group in siRNA delivery systems, i.c. (i) formation of stable siRNA polyplexes in the extracellular environment in order to protect the siRNA from degradation by reversible covalent binding of polymer-siRNA, (ii) fast pH-responsive release of siRNA from the polymer after internalization in order to display its antisense activity in the cytosol (iii) easy modification of the polyplexes with hydrophilic moieties (easy stealth modification) to obtain in vivo biocompatibility, (iv) easy binding of targeting groups to the polymers/polyplexes in order to obtain cell specificity. Moreover the simple binding via the boronic ester allows fast screening of several targeting groups and the use of combinations of targeting groups in polyplexes of these polymers. The physicochemical and biomedical properties of a selection of PAA/SS polymers with various degree of boronic acid content will be evaluated in connection with binding of siRNA for stable polyplex formation, binding of hydrophilic stealth polymer (dextran), binding of targeting groups (lactose, galactose, RGD, folate, etc.) and in vitro transfection properties. Promising polymeric vectors will be optimized for targeted delivery of siRNA in therapeutic treatment of rheumatoid arthritis.