A fast label-free biosensor based on WLRS for the determination of PSA as semen indicator in forensic samples is developed. The sensor is based on a two-step immunoassay which employs the same polyclonal anti-PSA antibody as capture and detection antibody followed by reaction with streptavidin as a signal enhancement step. Following this protocol, a detection limit of 0.5 ng/mL was achieved and the assay's linear response range extended up to 500 ng/mL. Thus, taking into account the quantification limit of 1.0 ng/mL and the average PSA concentration in semen (0.2–5.5 mg/mL), semen quantities of a few nanoliters could be detected. A linear correlation was found for semen dilutions ranging from 5000 to 360,000. The lack of interference by other bodily fluids was confirmed by analysing stains of blood, urine and saliva prior to and after the addition of semen. Finally, the sensor was evaluated by analysing 51 forensic casework samples which were also analysed with a semi-quantitative membrane strip test (Seratec® PSA), through microscopic detection of spermatozoa, and male DNA identification through detection of Y chromosome. The results obtained with the sensor were in excellent agreement with those provided by an immunoradiometric assay kit (PSA-RIACT) and in complete agreement with the findings using the membrane strip assay, spermatozoa and Y chromosome detection. The excellent analytical performance and small size of the instrument make the sensor developed an attractive tool for use in forensic evidence screening for semen detection.
G.Koukouvinos, A.Metheniti, Ch.-E.Karachaliou, D.Goustouridis, E.Livaniou, K.Misiakos, I.Raptis, A.Kondili, P.Miniati, P.Petrou, S.Kakabakos Talanta 175 443(2017) “White light reflectance spectroscopy biosensing system for fast quantitative prostate specific antigen determination in forensic samples”


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