Ultrasensitive Sandwich-Type SERS-Biosensor-Based Dual Plasmonic Superstructure for Detection of Tacrolimus in Patients

Tacrolimus (FK506) is widely used in the prevention of organ transplant rejection and the treatment of autoimmune diseases, but it is difficult to detect within the low and narrow concentration range in practical clinical fields. A magnetic plasmonic superstructure-targets-plasmonic superstructure-based sandwich-type SERS biosensor is presented here to ultrasensitively detect FK506 in the blood of organ transplant patients. The spiky Fe3O4@SiO2@Ag flower magnetic superstructure and hollow Ag@Au superstructure enhanced the SERS signals by providing rich sharp tips, cavities, and abundant hot spot gaps. And the magnetic feature makes it easy to concentrate and separate the biological target. Using the designed sandwich-type SERS biosensor, FK506 could be detected within a range of 0.5–20 ng/mL with a detection limit of 0.33 ng/mL. All results indicated that the sandwich-type SERS biosensor has good stability, sensitivity, and anti-interference properties. It is noteworthy that this allowed us to successfully analyze FK506 in the blood of transplant patients, which is in strong agreement with the clinical results. Consequently, the attractive sandwich-type SERS biosensor can be used for the detection of FK506 in real samples, which is promising for clinical diagnosis.