Exploring DNA-6MP interactions to develop a receptor with selective binding properties

This study focuses on identifying DNA sequences capable of selectively binding 6-mercaptopurine (6MP) or its analog, azathioprine (Aza), as a potential bioreceptor for biosensing methods. The approach used in the study is based on instrumental analysis methods such as UV-Vis spectroscopy, high performance liquid chromatography (HPLC), and nuclear magnetic resonance techniques to describe the interaction, its mode, and strength as well as selectivity of selected DNA sequences toward thiopurines. Thus, of the sequences tested, dsDNA GGCAGGACGGAG poses the ability to form complexes with 6MP, with an affinity constant of 2.52·10³ M^-1 as determined by DOSY NMR. Studies performed by HPLC technique confirmed the selectivity of the indicated strand toward selected interferents like natural metabolites and active pharmaceutical ingredients (API) used during azathioprine treatment. Further insights into the DNA-6MP interaction were provided by TOCSY and NOESY NMR experiments, highlighting the preference for guanine-rich sequences in binding, indicating a potential 6MP binding site in the dsDNA. The results also indicate the rapid conversion of azathioprine to 6-mercaptopurine upon contact with DNA, indirectly confirming the pro-drug nature of azathioprine. This research contributes to the development of DNA-based bioreceptors for selective determination of 6-mercaptopurine, with potential implications in personalized medicine and therapeutic drug monitoring.