Determination of a new antibacterial peptide S-thanatin in rat plasma by an indirected-ELISA.

In this study, antimicrobial peptide S-thanatin (Ts) was chemically synthesized and linked to keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA) by carbodiimide reagent. Rabbits were immunized with Ts-KLH and polyclonal antibody against Ts was purified by fractional precipitation of ammonium sulfate, coupled with anion-exchange chromatography. The purified antibody specifically binding to Ts residues but not BSA molecules was observed by Western-Blot analysis. Ts-BSA was selected as immobilized antigen and reacted with the residual antibody after the excess of anti-Ts antibody was combined with Ts in the sample. The binding antibody was recognized by HRP-conjugated secondary antibody. Finally, the horseradish peroxidase in the complex could catalyze the TMB substrate, resulting in color development. The method was evaluated by analysis of linearity, precision and accuracy and successfully applied in determination of Ts in rat plasma. The data of the pharmacokinetic parameters were also obtained. The proposed ELISA has a great value in routine analysis of Ts for its therapeutic monitoring and pharmacokinetic studies.