Ultrasensitive detection of PSA in human serum using Label-Free electrochemical biosensor with magnetically induced Self-Assembly based on α-Fe2O3/Fe3O4@Au nanocomposites

To achieve the goals of early diagnosis, screening, and precision medicine for prostate cancer, this research designed a label-free electrochemical biosensor by combining magnetic probes (PSAA/α-Fe2O3/Fe3O4@Au) with magnetically induced self-assembly (MISA) technology to explore the application of prostate-specific antigen (PSA) in precise detection. Magnetic α-Fe2O3/Fe3O4 nanoparticles (NPs) were constructed using a hydrothermal-calcination reduction method. Subsequently, α-Fe2O3/Fe3O4@Au nanocomposites were prepared by reducing HAuCl4 with NaBH4 at a low temperature. The self-assembly method was adopted in two steps: firstly, the sulfhydryl-modified PSA aptamer is immobilized onto the material surface using Au–S bonds; secondly, the magnetic NPs and magnetic glassy carbon electrode (MGCE) undergo self-assembly. The biosensor showed good linear response in the range of 100 fg/mL to 100 ng/mL, with a detection limit of 0.78 pg/mL (S/N = 3) under optimal conditions. Repeatability, stability, selectivity, reproducibility, and the capability to analyze real samples were also investigated. With its cost-effectiveness, operational simplicity, and speed of analysis, the biosensing system platform holds great potential as a valuable tool in clinical PSA detection for point-of-care testing (POCT).