Session: Nucleic Acids, Carbohydrates and Peptides:

Gadolinium-Based Contrast Agents (GBCA) are used extensively to improve Magnetic Resonance Imaging (MRI) resolution. However, recent studies have shown toxic levels of gadolinium (Gd) accumulation in patients undergoing MRI, leading to organ damage among other possible side effects. One way to circumvent this issue is to reduce the dosage administered, which in turn requires GBCA’s with higher efficacy. The contrast enhancement effect depends on molecular weight and the ability to form hydrogen bonds with water, both of which may be improved upon by the binding of an aptamer, or short, single-stranded DNA oligonucleotide (~40-80 bases long). In this study, aptamers for the GBCA known as Gd-DOTAM were developed via Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Forty rounds of SELEX were performed, with Gd-DOTAM reduced from 0.1 mM to 0.2 nM. Aptamer selectivity was determined by gel electrophoresis, with quantification by UV spectroscopy to be 21-45 ng/uL. The final aptamer pool was incorporated into E. coli cells via heat-shock transformation, and from 61 colonies, six consensus sequences were obtained. Preliminary UV fluorescence assays utilizing FAM/Dab tagged to modified aptamers and Complementary Strands (CS) respectively, show high binding affinity in the low microMolar range.

Marlin Halim

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