A highly sensitive and reusable magnetic nano-electrochemical biosensor for the detection of the liver cancer biomarker heat shock protein 70

• Aptamers offer a cost-effective alternative to traditional antibodies, with excellent specificity and high stability. • Fe 3 O 4 @Au-Apt7 magnetic nanoparticles can be easily immobilized on electrodes and readily recovered. • Rapid and sensitive detection offers an effective approach for the early diagnosis of liver cancer. A novel composite magnetic nanomaterial, functionalized with the aptamer Apt7, was developed. Its magnetic properties enable effective adsorption onto a magnetic glassy carbon electrode, forming a specific membrane designed for the detection of HSP70. The composite magnetic nanomaterial was synthesized using a chemical reduction method, resulting in uniformly sized Au-coated Fe 3 O 4 nanoparticles (Fe 3 O 4 @Au) with excellent electrical conductivity. Furthermore, the high-affinity aptamer Apt7 targeting HSP70 was selected using Systematic Evolution of Ligands by Exponential Enrichment (SELEX) and molecular fishing techniques. The thiol groups within the aptamer were effectively immobilized on the Au-coated Fe 3 O 4 nanoparticles surface via binding interactions with gold (Au). Electrochemical techniques were systematically employed to optimize the Apt7-modified biosensor, yielding a dissociation constant (K d ) of 72.49 pM. The optimized HSP70 biosensor demonstrated an extensive detection range, spanning from 10 pg mL −1 to 200 ng mL −1 , with a remarkable detection limit of 0.525 pg mL −1 (S/N = 3). This immunoassay proficiently detected HSP70 in human blood samples and exhibited superior performance relative to the commonly employed ELISA method in clinical analyses.