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 β-Cyclodextrin (β-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 1H 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 β-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 1H NMR techniques revealed successful
formation of PE-β-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 β-Cyclodextrin-polyrotaxane makes it a promising gene delivery vector for therapeutic applications.