Aptamer-siRNA conjugates

Aptamer-siRNA conjugates


Small interfering RNA (siRNA), known as short interfering RNA or silencing RNA, is a double-stranded RNA of 20 to 25 nucleotides formed when dsRNA is cleaved by specific nucleases in the cell.

The term aptamer, named by Ellington and Szostak in 1990, is derived from the Latin "aptus," which means "fit." The aptamer is an oligonucleotide sequence (RNA or DNA) selected from a library of random oligonucleotide sequences synthesized in vitro by the Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Aptamers are 20 to 80 nucleotides in length and can be folded into a well-defined three-dimensional (3D) structure. The aptamer can specifically combine with target molecules with high affinity, including heavy metal ions, cells, proteins, bacteria, viruses, etc.

A schematic  representation of the SELEX strategy of aptamer selection. Fig.1 A schematic representation of the SELEX strategy of aptamer selection. (Han J, 2020)

The combination of aptamers and siRNAs is known as aptamer-siRNA conjugates or AsiCs. When combined, AsiCs are internalized into the cell during endocytosis and, at least temporarily, enter the endosome or lysosome vesicles. Molecules that escape from the endosomal compartment are recognized by RNA interference (RNAi) mechanisms. Then, ribonuclease (Dicer) is combined with the siRNA of AsiC (black double-stranded, Fig.2), cutting the siRNA portion off from the aptamer and packing it into the RNA-induced silencing complex (RISC). RISC is a combination of proteins that further mediate the specific degradation of messenger RNA (mRNA). The Argonaute protein (AGO2) is a major component of RISC, which unwinds the siRNA double-strand and retains only the guide strand. Therefore, mRNA can pair with the guide strand loaded by RISC, and cleavage of mRNA will downregulate the gene expression relative to that mRNA. Aptamer-siRNA conjugates are one of the promising treatment methods for diseases such as cancer, cardiovascular diseases, and viral infections.

Concept of aptamer siRNA chimera (AsiC) delivery into a target cell. Fig.2 Concept of aptamer siRNA chimera (AsiC) delivery into a target cell. (Kruspe Sven, 2017)

The advantages of aptamer-siRNA conjugates

  • No immunogenicity and toxicity
  • Lower production cost
  • Relatively easily screened, synthesized, programmable designed, and chemically modified

Based on professional technical support, BOC Sciences is dedicated to providing design and synthesis of siRNA based on target genes and high quality aptamer. Additionally, we will optimize the chemical junction to enable direct coupling of RNAi to the end of the aptamer strand or complementary assembly.

The whole service flow

Custom siRNA synthesis

  • BOC Sciences offers a free siRNA design or you can submit selected siRNA sequences.
  • Comprehensive modification and labeling. From conventional modification to fluorescent/non-fluorescent labeling, even dual and multiple labeling.
  • Synthetic scale, 0.015 µmol, 50 nmol, 100 nmol, 200 nmol, 1 µmol, 5 µmol, 10 µmol, and > 10 µmol.
  • Quality control by analytical HPLC, mass spectrometry, annealing in RNase-free water, and double-stranded analysis by analytical gels.

Aptamer services

  • BOC Sciences provides aptamer development services. We use the SELEX method to select and obtain aptamers from nucleic acid sequence libraries with high affinity and high specificity for the target ligand. Your aptamer will purify by PAGE or HPLC and verify by mass spec.
  • BOC Sciences provides aptamer modifications services, such as biotin modifications are used in EMSA or Southern blotting. Fluorescence modifications are used for many imaging and diagnostic research with high sensitivity. 3' inverted thymidine modifications, 2'-O-methyl (OCH3) modifications, 2'-fluoro modifications and 2'-NH2 modifications to enhance their stability to nucleases.
  • BOC Sciences provides aptamer optimization services. Including basic sequence optimization, structure stability optimization, hydrophobic/hydrophilic part optimization, SELEX optimization, SELEX post-optimization.
  • BOC Sciences provides aptamer in vitro analysis services. Such as stability analysis and cytotoxicity assays.

Aptamer-siRNA conjugates

  • Coupling siRNA with target aptamer based on the chemical properties.
  • BOC Sciences establishes multiple engineering strategies for aptamer design to improve siRNA loading efficiency.
  • Functional optimization of aptamer-siRNA conjugates

Characterization services

  • Tertiary structural analysis
  • Thermodynamic analysis
  • Combined with affinity measurements
  • Competition assays


  • Stable and reproducible aptamer products
  • Aptamer with higher siRNA loading efficiency
  • Top technology supports multiple aptamer modifications
  • High quality raw materials
  • Free design
  • Experienced experts
  • Strict QA and QC
  • Advanced analytical equipments
  • Professional technical support
  • 1 on 1 customer service
  • Competitive price
  • Fast delivery

With much experience in aptamer design and coupling, BOC Sciences is fully capable and committed to providing you with a one-stop service for aptamer-siRNA conjugates services. Please feel free to contact us or send us an inquiry directly and we will be happy to assist you.


  1. Han J; et al. Application and development of aptamer in cancer: from clinical diagnosis to cancer therapy. J Cancer. 2020 Oct 4; 11(23): 6902-6915.
  2. Sven K; et al. Aptamer-siRNA Chimeras: Discovery, Progress, and Future Prospects. Biomedicines. 2017, 5(3).
  3. Aishwarya S; et al. Advances in siRNA delivery in cancer therapy. Artificial cells, nanomedicine, and biotechnology. 2018, 46(2).
* Only for research. Not suitable for any diagnostic or therapeutic use.
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