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Abstract This study was focused on extraction and purification of prostate specific antigen (PSA) from human seminal fluidas a basic material for the production of radioimmunoassay (RIA) components. Highly pure PSA wasobtainedwith purity 98.34± 1.62 %, recovery 65.83 ± 1.14 % and molecular weight 33 KDa as documented by SDS-PAGE. Using this locally purified PSA, the radioimmunoassay three main components was prepared,polyclonal antibody (anti-PSA), radio-iodinated PSA tracer and PSA standards. Polyclonal anti-PSA was produced by immunizing eightwhite New-Zealand rabbits with PSA through primary and four subsequent booster injections. The obtained anti-PSA titer was 1/1000 with displacement ranged from 65.9 to 80.3 % between rabbits.PSA tracerwas preparedusing optimized chloramine-T method, gave a yield 53.8±1.55% and specific activity 64.57±1.85 µCi/µg. The purity of this tracer was 98.0±1.85% as reported by paper electrophoresis results. PSA standards were prepared using locallypurified PSA antigen dissolved in two different matrices bovine serum and assay buffer. The radioimmunoassay parameters have been optimized, then formulated and the validity tests was carried out to the obtained standard curve, the result of validation reported as sensitivity 0.29 ng/ml, cross reactivity with related tumor marker to be less than 0.2 ng/ml, intrassay and interassay precision with coefficient of variation ranged from 4.1 to 6.9 % and accuracy test (recovery and dilution) ranged from 93.3 to 108.3 %.Finally the locally produced PSA-RIA system compared with commercialenzyme immunoassay (EIA)kit, giving a strong positive linear correlation with ‘r’ equal to 0.998. The results obtained provide an economic, highly sensitive and accurate RIA system for estimation of PSA as a diagnostic tool for prostatic diseases. |