Sustainable electrochemical biosensor using polyol-protected probes and magnetic MOFs for thermally robust coronavirus gene detection

• MMOF-based electrochemical biosensors enable rapid and sensitive nucleocapsid gene detection but face thermal stability challenges. • Covalent DNA conjugation and polyol protection strategies improved probe stability and prolonged sensor performance under heat. • Kinetic modeling and electrochemical analysis confirmed glycerol and polyethylene glycol effectively mitigated thermal degradation effects. Magnetic metal–organic frameworks (MMOFs) offer a promising, environmentally conscious platform for electrochemical sensing due to their high surface area, easy functionalization, and compatibility with green synthesis routes. In this study, MMOFs were synthesized using ferric chloride, imidazole, and histidine, then functionalized with covalently bound DNA capture probes for the electrochemical detection of the coronavirus nucleocapsid gene. Target-probe hybridization was transduced using neutral red intercalation and differential pulse voltammetry. To enhance thermal robustness, polyol-based protectants, polyethylene glycol and glycerol, were evaluated for their ability to preserve DNA functionality under high-temperature exposure (50–90 °C). Kinetic degradation behavior was modeled using a first-order Arrhenius approach, revealing that glycerol significantly reduced probe degradation and increased sensor half-life from 0.23 to 1.36 days at 90 °C. The probe density on the MMOF surface was shown to influence thermal stability, with moderate densities yielding optimal retention of the detection signal. The genosensor demonstrated ultra-low detection limits (down to 0.38 fM) and excellent linearity across six orders of magnitude in various biological fluids, including saliva, urine, and serum. This work demonstrates a sustainable sensing strategy that integrates green materials, benign thermal protection, and reusable nanostructures—advancing the development of eco-friendly diagnostic technologies.