Convenient Solid-Phase Attachment of Small-Molecule Ligands to Oligonucleotides via a Biodegradable Acid-Labile P-N-Bond

Abstract

One of the key problems in the design of therapeutic and diagnostic oligonucleotides is the attachment of small-molecule ligands for targeted deliveries in such a manner that provides the controlled release of the oligonucleotide at a certain moment. Here, we propose a novel, convenient approach for attaching ligands to the 5′-end of the oligonucleotide via biodegradable, acid-labile phosphoramide linkage. The method includes the activation of the 5′-terminal phosphate of the fully protected, support-bound oligonucleotide, followed by interaction with a ligand bearing the primary amino group. This technique is simple to perform, allows for forcing the reaction to completion by adding excess soluble reactant, eliminates the problem of the limited solubility of reagents, and affords the possibility of using different solvents, including water/organic media. We demonstrated the advantages of this approach by synthesizing and characterizing a wide variety of oligonucleotide 5′-conjugates with different ligands, such as cholesterol, aliphatic oleylamine, and p-anisic acid. The developed method suits different types of oligonucleotides (deoxyribo-, 2′-O-methylribo-, ribo-, and others).

Therapeutic Oligonucleotides: An Outlook on Chemical Strategies to Improve Endosomal Trafficking

“…However, the selectivity in cleavage at pH 7.4/5.5 has not been reported. Recently, a convenient solid-phase synthesis of oligonucleotide conjugates containing biodegradable, pH-sensitive phosphoramidate linkages has been reported (Figure 22) [270]. The effective release of oligonucleotides from small ligands under acidic conditions close to endosomes/lysosomes was observed while maintaining comparative stability at pH 6.…”

“…The developed versatile method can potentially be used to obtain a variety of oligonucleotides (i.e., ASOs, siRNAs, miRNAs, aptamers) conjugated to different ligands, and thus could give access to compounds with increased cellular delivery and endosomal release. Recently, a convenient solid-phase synthesis of oligonucleotide conjugates containing biodegradable, pH-sensitive phosphoramidate linkages has been reported (Figure 22) [270]. The effective release of oligonucleotides from small ligands under acidic conditions close to endosomes/lysosomes was observed while maintaining comparative stability at pH 6.…”

A Concise Review of The Role of Nanotechnology, Nanoparticles and Nanomedicine Play in The Diagnostics, Vaccination and Treatment Options For COVID-19

“…These include colorimetric assays made using nanoparticles, new optical sensors, nano immune-sensors for COVID-19, novel immune-chromatographic assays, aptamer based COVID-19 assays as well as bio-barcode assays [3]. Some of the nanotechnology, nanoparticles and nanomedicine based other applications as well as uses of in COVID-19 diagnostics and detection are presented in (see Figure 5 and 6 below) (see Table 1 below) [28][29][30][31][32][33][34][35][36][37][38].…”

“…11,15,18,[33][34][35][36][37][38] Nanotechnology, nanoparticles and nanomedicine based COVID-19 treatment options being developed currently. Natural polymers like chitosan, dextran, alginates, hyaluronic acid albumin, gelatin, and collagen have antiviral characteristics.-Synthetic polymers including polyethylene glycol, N-(2-hydroxypropyl)-methacrylamide copolymer, Poly (lactic-co-glycolic acid) (PLGA), poly-1-glutamic acid, polystyrene maleic anhydride copolymer found use in nano-drug delivery systems.…”