Highly selective detection of methamphetamine in urine using biosynthesized graphene oxide-gold nanoparticle composite modified electrodes

Abstract

This study presents a novel electrochemical aptasensor for the detection of methamphetamine, utilizing a biosynthesized graphene oxide-gold nanoparticle (GO-AuNP) composite. The nanocomposite was synthesized using Shewanella oneidensis MR-1, offering a green and cost-effective alternative to traditional chemical methods. Characterization by UV–vis spectroscopy, TEM, XRD, and FTIR confirmed the successful formation of the GO-AuNP composite, with AuNPs averaging 18.3 ± 3.7 nm in diameter uniformly distributed on GO sheets. The aptasensor was optimized for aptamer concentration (10 μM), incubation time (30 minutes), and pH (7.4). Electrochemical impedance spectroscopy measurements revealed a linear relationship between the change in charge transfer resistance and the logarithm of methamphetamine concentration from 0.5 nM to 500 nM. The aptasensor achieved a detection limit of 0.15 nM, surpassing many existing methods. Cross-reactivity studies with potential interferents showed minimal response, with all tested compounds exhibiting less than 15 % relative signal compared to methamphetamine. The sensor demonstrated good reproducibility (RSD = 4.8 %) and retained over 90 % of its initial response after 30 days of storage. Analysis of spiked urine samples yielded recovery rates between 96.8 % and 103.5 %, validating the aptasensor's potential for real-world applications in sports doping control and clinical diagnostics.