Synthesis and properties of oligodeoxyribonucleotide—polyethylene glycol conjugates

Abstract

Pools of oligonucleotide conjugates consisting of 10-400 different molecular species were synthesized. The conjugates contained a varying number of ethylene glycol units attached to 3'-terminal, 5'-terminal and internal positions of the oligonucleotides. Conjugate synthesis was performed by phosphoramidite solid phase chemistry using suitably protected polyethylene glycol phosphoramidites and PEG-derivatized solid supports containing polydisperse PEGs of various molecular weight ranges. The pools were analyzed and fractionated by chromatographic and electrophoretic techniques, and the composition of isolated conjugates was revealed by matrix-assisted laser desorption/ionization mass spectrometry. The number and attachment sites of coupled ethylene glycol units greatly influence the hydrophobicity of the conjugates, as well as their electrophoretic mobilities. Conjugation had little effect on the hybridization behavior of oligonucleotide conjugates with unmodified complementary oligonucleotide strands. Melting temperatures were between 67 and 73 degrees C, depending on the size and number of coupled PEG chains, compared to 68 degrees C for the unmodified duplex. Conjugates with PEG coupled to both 3'- and 5'-terminal positions showed a more than 10-fold increase in exonuclease stability.

Bioconjugation of Oligonucleotides for Treating Liver Fibrosis

“…PEG can be introduced to an ODN at the 3' end or 5' end or internal positions in the solid-phase synthesis of ODNs (488)(489)(490). However, these synthesis strategies do not allow easy upscaling.…”

“…PEG coupling to both the 3' and 5' terminal positions of an antisense ODN produced more than 10-fold increase in exonuclease stability, while having no effect on the ability of hybridization (488). Furthermore, the cellular uptake of ODNs can also benefit from PEGylation (496).…”

“…It was found that only the conjugate with linear PEG showed anti-HIV activity. Furthermore, the number and attachment sites (at the 5', 3' or both 5' and 3' termini) of the conjugated PEG greatly influence the hydrophobicity of the conjugates (488).…”

Molecular Modeling of PEGylated Peptides, Dendrimers, and Single-Walled Carbon Nanotubes for Biomedical Applications

“…Also, they can sterically shield molecules encapsulated in drug carriers and thus have been covalently or noncovalently conjugated to a number of pharmaceuticals, a process called PEGylation [1,2]. These biomedical applications of PEGylation have been shown to reduce the cytotoxicity as well as increase the water solubility and circulating lifetime of drug molecules or drug carriers such as peptides [3,4], oligonucleotides [5][6][7][8], lipid liposomes [9][10][11][12][13], biodegradable hydrogels [14,15] and nanoparticles [16][17][18][19]. Although experiments have revealed vital information on the large-scale interactions of PEGs with drugs and drug carriers, many atomic-level questions that cannot be answered by experiments remain to be solved.…”

Hybridization and cellular uptake properties of lipophilic oligonucleotide-dendrimer conjugates

“…Examples are conjugates with cationic compounds, such as poly-(L)-lysine 9 or polyamides, 10 lipophilic conjugates, such as cholesterol, 11 long chain alcohols, 12 phospholipids, 13 aromatic compounds, 14 as well as polyethylene glycol. 15 Furthermore, the effect of attachment of these compounds at different position of the oligonucleotides including the bases, the backbone and the 3 ' -or 5 ' end was investigated. Uekama and coworkers reported that gene transfer activity was significantly improved by conjugates of α-, β-, and γ-cyclodextrins with polyamidoamine starburst dendrimers.…”