Biodegradable Polyester of Poly (Ethylene glycol)-sebacic Acid as a Backbone for β-Cyclodextrin-polyrotaxane: A Promising Gene Silencing Vector.

Background: Polyrotaxane, a macromolecular interlocked assembly, consisting of cyclodextrin has excellent inclusion capabilities and functionalization capacity, which makes it a versatile material as a vector for gene delivery applications. Objective: A biodegradable linear aliphatic polyester axle composed of Polyethylene Glycol (PEG) and Sebacic Acid (SA) was used to fabricate the beta-Cyclodextrin (beta-CD) based polyrotaxane as a cationic polymeric vector and evaluated for its potential gene silencing efficiency. Methods: The water-soluble aliphatic polyester was synthesized by the solvent esterification process and characterized using viscometry, GPC, FT-IR and H-1 NMR spectroscopy. The synthesized polyester was further evaluated for its biodegradability and cellular cytotoxicity. Hence, this water-soluble polyester was used for the step-wise synthesis of polyrotaxane, via threading and blocking reactions. Threading of beta-CD over PEG-SA polyester axle was conducted in water, followed by end-capping of polypseudorotaxane using 2,4,6-trinitrobenzenesulfonic acid to yield polyester-based polyrotaxane. For gene delivery application, cationic polyrotaxane (PRTx(+)) was synthesized and evaluated for its gene loading and gene silencing efficiency. Results and Discussion: The resulting novel macromolecular assembly was found to be safe for use in biomedical applications. Further, characterization by GPC and H-1 NMR techniques revealed successful formation of PE-beta-CD-PRTx with a threading efficiency of 16%. Additionally, the cellular cytotoxicity assay indicated biosafety of the synthesized polyrotaxane, exploring its potential for gene delivery and other biomedical applications. Further, the biological profile of PRTx(+): siRNA complexes was evaluated by measuring their zeta potential and gene silencing efficiency, which were found to be comparable to Lipofectamine 3000, the commercial transfecting agent. Conclusion: The combinatory effect of various factors such as biodegradability, favourable complexation ability, near zero zeta potentials, good cytotoxicity properties of poly (ethylene glycol)-sebacic acid based beta-Cyclodextrin-polyrotaxane makes it a promising gene delivery vector for therapeutic applications.