High-sensitivity detection of PSA by Time-resolved fluorometry with Europium Chelate

Prostate-specific antigen (PSA) is an androgen-dependent glycoprotein protease (M.W. 33 kDa) and a member of kallikrein super-family of serine protease, and has chymotrypsin-like enzymatic activity. It is synthesized by the prostate epithelial cells and found in the prostate gland and seminal plasma as a major protein. It is widely used as a clinical marker for diagnosis, screening, monitoring and prognosis of prostate cancer. In normal male adults, the concentration of PSA in the blood is below 4 ng/ml and this value increases in patients with the prostate cancer or the benign prostatic hyperplasia (BPH) due to its leakage into the circulatory system. As such, systematic monitoring of the PSA level in the blood can provide critical information about the progress of the prostatic disease. We have fabricated a bread-board time resolved fluorescence system that could detect a concentration of Prostate Specific Antigen(t-PSA) at clinically meaningful level in plasma as well as in whole blood sample. We chose Europium chelates as the fluorescence markers to attach to the PSA for its long decay lifetime and relative photostability. We have simplified the electronic circuits considerably by employing a MCS. With this setup, we have successfully proved that PSA concentration of 4pg/mL can be detected with acceptable reliability.