Photoluminescence-based ultrasensitive DNA detection of typhoid using MgO nanomaterials

Abstract

An ultrasensitive optical DNA biosensor based on magnesium oxide (MgO) nanoparticles is reported for the detection of Salmonella typhimurium. The sensing mechanism relies on photoluminescence (PL) modulation governed by defect-mediated charge transfer interactions known as photoinduced electron transfer upon DNA hybridization. The MgO nanostructures exhibit strong emission centered at ∼780 nm, which is significantly enhanced upon probe DNA immobilization due to surface defect passivation. Subsequent hybridization with target DNA induces concentration-dependent PL quenching, enabling quantitative detection in the range of 30–150 aM. A linear calibration response with a high correlation coefficient (R2 = 0.96) is obtained, yielding a limit of detection of 4.2 aM. The biosensor demonstrates excellent specificity, with a ∼6.5-fold higher response for complementary DNA compared to non-complementary sequences. The observed PL modulation is attributed to radiative recombination suppression via charge transfer interactions following dsDNA formation. The developed platform offers a rapid, label-free, and highly sensitive approach for pathogen detection, highlighting the potential of MgO-based optical biosensors for advanced diagnostic applications.