Observation of Ɛ-Al₁₃-Keggin-oligonucleotide complexes in analytical sample solutions

Area of Science:

• Analytical Chemistry
• Materials Science
• Biochemistry

Background:

• Drug product stability testing is crucial for pharmaceutical quality control.
• Antisense oligonucleotides are a class of therapeutic nucleic acids.
• Aluminum cluster molecules, such as Ɛ-Al13-Keggin, can be encountered in analytical settings.

Purpose of the Study:

• To identify the source of new impurity peaks observed during antisense oligonucleotide drug product stability testing.
• To characterize the interaction between Ɛ-Al13-Keggin molecules and antisense oligonucleotides.
• To develop strategies to prevent artifact formation during sample preparation.

Main Methods:

• Impurity profiling using analytical techniques.
• Synthesis and characterization of Ɛ-Al13-Keggin molecules.
• Binding affinity studies between Ɛ-Al13-Keggin and various oligonucleotide sequences.
• Comparative analysis of sample preparation methods using different weighing materials.

Main Results:

• Observed impurity peaks were identified as complexes of Ɛ-Al13-Keggin molecules and antisense oligonucleotides.
• These complexes were determined to be analytical artifacts arising from the use of aluminum weigh boats.
• Ɛ-Al13-Keggin molecules demonstrated binding affinity to oligonucleotides of varying lengths and compositions, with a potential preference for 5-methylcytosine.
• Switching to polypropylene or glass weighing funnels eliminated the formation of these artifact complexes.

Conclusions:

• The use of aluminum weigh boats in sample preparation can lead to artifactual complex formation between Ɛ-Al13-Keggin molecules and antisense oligonucleotides.
• Modification of sample preparation procedures is essential to ensure accurate stability testing of oligonucleotide drug products.
• Alternative inert materials for sample handling prevent the co-precipitation of analytical artifacts.