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1'-Sugar-Tethered Cholesterol-Modified siRNAs with Variable Linker Lengths for Carrier-Free Delivery and Enhanced
Yurina Shimada1, Ayane Tsuchida2, Shin Ando3
1Department of Life Science and Chemistry, the Graduate School of Natural Science and Technology, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
ACS Omega
|July 28, 2026
Summary
Newly developed cholesterol-conjugated small interfering RNAs (siRNAs) enable carrier-free delivery and potent gene silencing. Optimized linker lengths enhance cellular uptake and RNA interference (RNAi) activity for therapeutic applications.
Area of Science:
- Biochemistry
- Molecular Biology
- Drug Delivery
Background:
- Small interfering RNAs (siRNAs) are promising therapeutics but face delivery challenges.
- Chemical modifications are crucial for efficient siRNA delivery and RNA interference (RNAi).
- Cholesterol conjugation is a strategy to enhance siRNA cellular uptake and activity.
Purpose of the Study:
- To design and synthesize novel cholesterol-conjugated siRNAs with varying linker lengths.
- To evaluate the impact of linker length on siRNA duplex stability and RNAi efficiency.
- To demonstrate carrier-free cellular uptake and gene silencing capabilities of modified siRNAs.
Main Methods:
- Synthesis of cholesterol derivatives with 0, 2, 4, and 6-carbon alkyl linkers (Y1-Y4).
- Conjugation of cholesterol derivatives to the 3' end of siRNA passenger strands.
- Thermal melting analysis (Tm) to assess duplex stability.
- X-ray crystallography to determine structural basis of stabilization.
- Functional evaluation in HCT116 colon cancer cells for gene knockdown (KNTC2) and IC50 analysis.
Main Results:
- All cholesterol modifications increased siRNA duplex stability, with Y1 (Chol-C0) showing the highest Tm.
- X-ray crystallography revealed defined cholesterol orientations and interactions contributing to stabilization.
- Cholesterol conjugation significantly improved carrier-free cellular uptake and gene silencing in a linker-length-dependent manner.
- The 4-carbon linker (Y3: Chol-C4) demonstrated the most potent KNTC2 knockdown and lowest IC50 value (141.5 nM).
- The 2-carbon linker (Y2: Chol-C2) also showed strong efficacy, while Chol-C0 and Chol-C6 were less effective.
Conclusions:
- Optimized linker lengths in 1'-sugar-tethered cholesterol-conjugated siRNAs are critical for efficient carrier-free delivery.
- These modified siRNAs exhibit potent RNA interference activity, offering a promising approach for siRNA-based therapeutics.
- The study provides a structural and functional basis for the design of next-generation siRNA delivery systems.
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