Detection of urinary prostate specific antigen by a lateral flow biosensor predicting repeat prostate biopsy outcome

This work describes the development and the application of a lateral flow biosensor for the detection of the prostate specific antigen in urine (uPSA). The biosensor allowed uPSA detection in 10 minutes with a limit of detection and a range of quantification respectively of 20 ng/mL and 37 – 420 ng/mL, showing within and between-day coefficients of variation ≤ 13%. It showed 92% of accuracy and an almost perfect concordance with the reference electrochemiluminescence immunoassay method. The biosensor design provides the disappearance of the Test line signal at the cut-off concentration. This was achieved with a double layer sensing strategy, in which gold nanoparticles were functionalized with Staphylococcal protein A – a mediator – instead of anti-PSA antibody. This strategy allow making a fine-tune on the concentration of the specific antibody, obtaining an on/off switch of the Test line at the cut-off value. The cut-off value was also established in this work, based on the distribution of uPSA levels from 140 patients, who were suspected of prostate cancer and who underwent to first biopsy. The clinical application of the biosensor to predict repeat biopsy outcome in 28 patients showed sensitivity, specificity, positive and negative predictive values of 100%, 64%, 74% and 100%, respectively