Development of Excipient-Free Freeze-Dryable Unimolecular Hyperstar Polymers for Efficient siRNA Silencing

Area of Science:

• Biomaterials Science
• Nanotechnology
• Gene Therapy

Background:

• Efficient delivery of small interfering RNA (siRNA) is crucial for gene therapy.
• Current siRNA delivery systems often require excipients and can degrade during lyophilization.
• Familial amyotrophic lateral sclerosis (ALS) is linked to mutations in the Cu, Zn superoxide dismutase 1 (SOD1) gene.

Purpose of the Study:

• To design a novel unimolecular hyperstar polymer for enhanced siRNA delivery.
• To evaluate the stability and efficacy of the polymer-siRNA complex after lyophilization and reconstitution.
• To compare the transfection efficiency of the novel polymer with a commercial standard.

Main Methods:

• Synthesis of a unimolecular hyperstar polymer with a biodegradable hyperbranched core and cationic arms.
• Complexation of siRNA with the hyperstar polymer.
• Assessment of siRNA transfection efficiency in vitro, specifically targeting the SOD1 gene.
• Evaluation of complex stability and transfection efficiency after repeated lyophilization and reconstitution cycles.

Main Results:

• The hyperstar polymer efficiently complexed with siRNA via its cationic arms.
• siRNA/hyperstar complexes demonstrated superior transfection efficiency compared to Lipofectamine2000 for the SOD1 gene.
• The unimolecular structure prevented inter-polymer interactions during lyophilization, preserving transfection efficiency after freeze-drying and reconstitution.
• No excipients were required for processing, simplifying the formulation.

Conclusions:

• Unimolecular hyperstar polymers offer a stable and efficient platform for siRNA delivery.
• This novel polymer system overcomes the limitations of lyophilization instability in conventional siRNA carriers.
• The developed polymer holds promise for developing stable, ready-to-use siRNA therapeutics, particularly for neurodegenerative diseases like ALS.