RNA aptamers and spiegelmers: synthesis, purification, and post-synthetic PEG conjugation

Curr Protoc Nucleic Acid Chem. 2011 Sep;Chapter 4:Unit 4.46.1-30. doi: 10.1002/0471142700.nc0446s46.


This unit describes the solid-phase synthesis and downstream processing for RNA oligonucleotides with a length of up to 40 to 50 nucleotides on a 1- to 4-mmol scale with subsequent conjugation to PEG using the L-RNA spiegelmer NOX-E36 as an example. Following synthesis and two-step deprotection, the crude oligonucleotide is purified by preparative reversed-phase HPLC and desalted by tangential flow ultrafiltration. The resulting intermediate amino-modified oligonucleotide is reacted with NHS-ester-activated PEG, and the oligonucleotide-PEG conjugate is obtained after preparative AX-HPLC purification, followed by ultrafiltration and lyophilization. Critical process parameters are described, as well as time considerations and examples for analytical methods used as in-process and quality controls.

MeSH terms

  • Aptamers, Nucleotide / chemical synthesis*
  • Aptamers, Nucleotide / isolation & purification*
  • Chromatography, High Pressure Liquid
  • Freeze Drying
  • Oligonucleotides / chemistry
  • Oligonucleotides / isolation & purification
  • Phosphorothioate Oligonucleotides / chemistry
  • Polyethylene Glycols / chemistry
  • Solid-Phase Synthesis Techniques
  • Ultrafiltration


  • Aptamers, Nucleotide
  • Oligonucleotides
  • Phosphorothioate Oligonucleotides
  • Polyethylene Glycols