Design and Synthesis of an Adamantane Phosphoramidite for Programmable and Automated Oligonucleotide-Functionalization

Solid-phase synthesis has revolutionized the programmable preparation of oligonucleotides (ONs), enabling precise gene expression modulation and expanding their applications in therapeutic and material sciences. To further enhance ON functionality, this study introduces a novel adamantane-based phosphoramidite for oligonucleotide modification. Adamantane, known for its hydrophobicity and stability, was incorporated into nucleic acid aptamers using automated synthesis. Two aptamers─Sgc8 and AS1411─were functionalized with one or two adamantane units, and the products were purified and validated using high-performance liquid chromatography and mass spectrometry. The incorporation of adamantane significantly altered the aptamers' polarity and facilitated their self-assembly with poly-β-cyclodextrin, forming stable supramolecular complexes, as demonstrated by polyacrylamide gel electrophoresis. Additionally, adamantane-modified AS1411 exhibited enhanced degradation of its target protein, nucleolin, in MCF-7 cells, suggesting potential utility in targeted protein regulation. These findings establish a versatile platform for functionalizing ONs, broadening their potential for biomedical and nanotechnological applications.