Amperometric biosensors for detection of the prostate cancer marker (PSA)

Prostate specific antigen (PSA) has been identified as the most reliable clinical tool for diagnosing and monitoring prostate cancer (CAP). Since, there is no curative therapy available for prostate cancer, detecting the disease at the early stage is the best hope of increasing mortality rate. There are some procedures available for the detection of prostate cancer e.g. Tandem-R PSA, Hybritech Inc. (USA), IMx-PSA Abbott Laboratories (USA). However, these are time consuming and costly. We have developed a very simple and cost effective technique for identification and monitoring of prostate cancer using amperometric immunosensor. PSA is a glycoprotein with 93% peptide and 7% sugar content and isoelectric pH of 6.9. It may exist in the human serum as free (f-PSA) and complex (PSA-ACT) forms. Normally if the total PSA (t-PSA) level is more than 10 ng/ml, CAP is suspected. This paper presents an amperometric detection procedure for t-PSA using three electrode system in which working electrode (WE) is made of hydroxyethyl cellulose (HEC) and rhodinised carbon. The method used is rapid, very easy to use and involves low cost compared with other procedures. The electrochemical response was directly observed due to enzymatic reaction via a sandwich immunoassay on the WE. Monoclonal capture antibody (Mab) to PSA was immobilised on the WE and the other Mab labelled by the enzyme marker, horseradish peroxidase (HRP), was used as a tracer antibody.