Comparative study of different radioiodination methods of monoclonal antibody for immunoradiometric assay of prostate specific antigen

Forutan, Haleh; Khodabakhsh, Marziyeh; Jouharideha, Farib; Pourabdi, Ladan

Comparative study of different radioiodination methods of monoclonal antibody for immunoradiometric assay of prostate specific antigen

Document Type : Research Paper

Authors

Haleh Forutan

Marziyeh Khodabakhsh

Farib Jouharideha

Ladan Pourabdi

Abstract

Prostate specific antigen (PSA), a serine protease, is a highly reliable biochemical marker used for detection and management of prostate cancer. PSA in serum samples is measured by an immunoanalytical technique such as immunoradiometric assays (IRMA). In this study the preparation method and the effective factors on the efficiency and the stability of the labeled anti-PSA monoclonal antibody with I-125 as a tracer in the immunoradiometric kit (IRMA) were investigated. To perform an IRMA assay, at first, the labeled anti-PSA monoclonal antibody was formed using oxidizing agents, namely Chloramine-T and Iodogen, then the product was separated and purified by Sephadex G-25 column. After the determination of radiochemical purity, I-125 labeled antibody was used in the in-house PSA IRMA kit. The effects of the proportion antibody/I-125(17.6-53 µg/mCi), Chloramine-T/antibody (0.75 & 1.5 µg/µg) and the labeling time (15-60 s) on the efficiency and stability of the labeled antibody were studied. According to the calibration curve and concentration of control samples, Chloramine-T radioiodination procedure was optimized (Chloramine-T/antibody: 1.5 µg/µg & labeling time: 50s). The variety of the proportion antibody/I-125 was ineffective in radioiodination efficiency. The Chloramine-T radiolabeled antibody was found to be stable for 30 days when stored at 4^◦C. Also radioiodination using Iodogen was studied at different Iodogen concentrations (0.1&0.2 mg/ml) and Dichlromethane volumes (0,200&400 µl). According to the obtained results, the appropriate amount of Iodogen and Dichlromethane were obtained to be 0.1mg/ml and 200µl. But Iodogen radiolabeled antibody showed poor immunoradioactivity and stability after two weeks. The results show that the Chlroamine-T procedure is more suitable than the Iodogen method, so the Chloramine-T radiolabeled antibody could be used as a tracer in IRMA system for quality control of in-house PSA kit. By studying the results of t-Test analysis, the decision criteria (sig 2-tailed= 0.993) and confidence interval (95%), it can be seen that the values are well correlated.

Keywords

Specific prostate antigen kit

Immunoradiometric assay

Monoclonal antibody

Radioiodination

Chlroamine-T

Iodogen

Sephadex G-25

Immunoradianetric kit

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