Isolation of antisense oligonucleotides

1. A method of isolating fully thioated single stranded antisense oligonucleotides from a biological solution, which method comprises the steps of contacting the biological solution with an immobilised metal ion adsorption chromatography (IMAC) resin to adsorb antisense oligonucleotides to said resin and subsequently contacting the resin with an eluent under conditions that provide desorption of the antisense oligonucleotides from said resin, wherein the fully thioated antisense oligonucleotides are separated from incorrectly synthesised and/or incorrectly thioated antisense oligonucleotides in said solution; further wherein the metal ion is Zr 2+ or Fe 3+ .

2. The method of claim 1 , wherein the biological solution is a synthesis reaction of antisense oligonucleotides.

3. The method of claim 1 , further wherein fully thioated antisense oligonucleotides are separated from incorrectly synthesised oligonucleotides.

4. The method of claim 1 , wherein fully thioated antisense oligonucleotides are separated from incorrectly thioated antisense oligonucleotides containing 1-5 bonds without thioation.

5. The method of claim 1 , wherein the antisense oligonucleotides are of a size in the range of 5-30 base pairs.

6. The method of claim 1 , wherein the pH of the biological solution is below about 7 during the adsorption of antisense oligonucleotides.

7. The method of claim 1 , which in addition comprises a subsequent step of polishing the isolated antisense oligonucleotides.