Detection of prostate specific antigen in serum at the femto-gram per milliliter level using the intrinsic amplification of a field-effect enzymatic immuno-sensing system

Ultrasensitive detection of prostate specific antigen (PSA) has been achieved by applying the field-effectenzymatic detection (FEED) technique to the sandwich immuno-sensing technique. The voltage-controlled intrinsic amplification provided by FEED enabled the detection of PSA contained in serumon the femto-gram/mL level. Two electrochemical approaches used to obtain the amperometric detec-tion signal resulted in similar detection limits and sensitivities. The lowest PSA detection limit achievedwas 27 fg mL-1. The high selectivity of the detection system was reflected in the fact that PSA detectionwas successful on the fg mL-1level, where biological substances other than PSA had a 1-million-foldhigher concentration. Electron transfer through the immunological sandwich nanostructure has beenobserved in the detection of biomarkers. However, our results showed that electron transfer through thenanostructure could be controlled using an external voltage, leading to an ultralow detection limit for PSA