The Department of Chemistry at the College of Science, University of Basrah, discussed a Ph.D. dissertation entitled:

“Development of Gold and Silver Nanoparticle-Based Colorimetric Biosensors for the Detection of Methamphetamine (Crystal Meth) in Biological Specimens”

by the postgraduate student Jumana Mohammed Khalaf.

The dissertation aims to synthesize and characterize gold and silver nanoparticles through a green chemistry method using N-Acetyl-L-cysteine as both a reducing and capping agent. The nanoparticle surfaces were then functionalized with a thiolated single-stranded DNA aptamer specific to methamphetamine, with the purpose of developing a sensitive, selective, and eco-friendly colorimetric aptasensor for methamphetamine detection in biological samples.

The prepared nanoparticles were characterized using UV–Vis, FTIR, XRD, TEM, FESEM-EDX, DLS, and zeta potential, while the developed biosensors were analyzed using UV–Vis and GC–MS to confirm nanoparticle formation and successful aptamer conjugation.

The results demonstrated that the detection mechanism relied on a distinct color change upon methamphetamine binding—shifting from red to blue in the case of gold nanoparticles, and from colorless to yellow in the case of silver nanoparticles—due to nanoparticle aggregation. Calibration curves showed good linearity between absorbance ratios and methamphetamine concentration, with limits of detection (LOD) of 0.112 μM for AuNPs and 0.165 μM for AgNPs.

Furthermore, the developed biosensors were successfully applied to real biological samples such as blood, urine, saliva, hair, and nails, showing high efficiency, good sensitivity, and rapid response. A comparison with the conventional GC–MS technique confirmed the reliability of the biosensor as a practical, low-cost, rapid, and non-invasive alternative for clinical and forensic applications.

The study also recommends the possibility of developing similar detection systems using different nanocarriers or other specialized aptamers.