Selective determination of 6-mercaptopurine by a platinum nanoparticle-enhanced dsDNA-based electrochemical biosensor.

An electrochemical biosensor is presented utilizing short double-stranded DNA (dsDNA 5`-GGCAGGACGGAG-3`) with proven selective interaction with 6-mercaptopurine (6MP). Two biosensor designs were developed: one based on screen-printed graphite electrodes (GSPEs) with an adsorbed dsDNA layer (GSPE/dsDNA) and another one incorporating platinum nanoparticles to enhance the electrochemical response (GSPE/Pt-Cys-dsDNA). The developed GSPE/dsDNA and GSPE/Pt-Cys-dsDNA biosensors demonstrated a linear response within the nanomolar concentration range, from 200 to 1000 nM and from 2 to 75 nM, respectively. Selectivity studies confirmed effective discrimination of 6MP from common biointerferents and other coadministered drugs. Ultimately, the biosensor’s analytical performance was verified in artificial urine samples spiked with 6MP. The results from the biosensor with the Pt nanoparticles closely matched those from the reference HPLC method (±7%), confirming its accuracy and reliability. Overall, this work demonstrates how interactions of specific dsDNA sequence with small molecule can be translated into a robust electrochemical microanalytical tool for selective nanomolar determination of 6-mercaptopurine. This is the first reported DNA-based electrochemical approach for selective 6MP sensing, providing a rapid and cost-effective alternative to traditional instrumental methods.