Optimal Hydrophobicity in Ring-Opening Metathesis Polymerization-Based Protein Mimics Required for siRNA...

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Cellular Biology

Background:

• Developing effective delivery reagents for biologically relevant cargo, such as small interfering RNA (siRNA), is crucial.
• Understanding the relationship between polymer structure and cargo internalization is key to improving delivery systems.

Purpose of the Study:

• To explore how polymer structure, specifically hydrophobic block length and side chain composition, influences siRNA internalization.
• To identify optimal hydrophobic characteristics for guanidinium-rich protein transduction domain mimics (PTDMs) in siRNA delivery.

Main Methods:

• Synthesis of diblock copolymers with varying hydrophobic block lengths (symmetric and asymmetric) and side chain compositions (dimethyl, methyl phenyl, diphenyl, diethyl, diisobutyl, dicyclohexyl).
• Evaluation of siRNA internalization efficiencies in Jurkat T cells and HeLa cells.
• Quantification of relative hydrophobicities using high-performance liquid chromatography (HPLC).

Main Results:

• Both symmetric and asymmetric PTDMs promoted siRNA internalization, with asymmetric PTDMs showing greater internalization at 20 repeat units of cationic charge.
• A critical window of hydrophobicity was identified, with PTDMs containing methyl phenyl (MePh), diisobutyl (diBu), and diphenyl (dPh) hydrophobic blocks demonstrating superior siRNA internalization.
• Hydrophobicity, quantified by HPLC retention times, directly correlated with internalization efficiency, with intermediate hydrophobicities being optimal.

Conclusions:

• The study elucidates structure-activity relationships for PTDMs in siRNA delivery.
• Optimizing the hydrophobic characteristics of PTDMs is essential for efficient cellular internalization of siRNA.
• These findings will guide the rational design of next-generation siRNA delivery reagents.