DNA super-lattice-based aptasensor for highly sensitive and selective detection of cortisol

Monitoring cortisol is one of the current challenges in medicine, as this hormone plays an essential role in several physiological processes. One of the main interests is the accurate clinical diagnosis of stress and anxiety, as the patients release this hormone in body fluids such as saliva or sweat. An electrochemical biosensor for cortisol detection emerges as a bright spot to be explored, as it can be a very straightforward technique, making the detection and quantification of cortisol simpler and more accessible and the diagnosis more precise. We report a protocol to build a novel biosensor for cortisol detection by coupling aptamers with DNA-based superlattices. We evaluated its analytical performance by correlating the electrochemical results with the highly oriented structure of the DNA-based superlattice in previous work. We demonstrated that this structure provides the advantage of very high electron transfer. It could be affected by the specific interaction events on the surface of DNA combined with the high affinity of the cortisol/aptamer. We report selective and sensitive results (linear response range from 0.5 up to 10 nmol L−1 fitted by the equation ΔRct(Ohm) = (410 ± 13) + (931 ± 30) [cortisol] (nmol L−1), with R2 = 0.992, and LOD of 0.13 nmol L−1, adjusted for practical use in saliva samples, which could be further optimized to quantify even lower concentrations. © 2022 The Author(s)