Fig. 2
From: Recent progress in microRNA-based delivery systems for the treatment of human disease
Chemical modifications improve stability, biodistribution, cellular uptake and delivery efficiency and increase the tracer function of oligonucleotides. (0) Unmodified RNA; (1) phosphorothioate-, (2) methylphosphonate-, or (3) boranophosphate-containing oligonucleotides containing a sulfur, methyl, or borano group, respectively; (4) 2′-O-methyl, (5) 2′-O-methoxyethyl, (6) or 2′-fluoro introduced into the 2′ oxygen of the ribose; (7) LNAs; (8) PNAs; (9) PMOs; and terminal chemical modifications, including (10) Cy3-, (11) cholesterol-, (12) biotin- and (13) amino-modified oligonucleotides could increase the stability and tracer function of oligonucleotides for in vivo delivery