An efficient and controlled method for immunodetection, using polystyrene (PS) microbeads conjugated with an elastin-like polypeptide (ELP), was investigated. ELP is a temperature-sensitive polymer that exhibits a hydrophilic-hydrophobic phase transition at the lower critical solution temperature. To introduce amine groups, ELP was modified with lysine for conjugation with PS microbeads functionalized with carboxylic groups. Prostate-specific antigen (PSA), a cancer marker, was detected from a biomolecular mixture using ELP-conjugated PS microbeads and ELP-conjugated antiPSA. External stimuli were used to reversibly separate the PSA-antiPSA complex. The stimuli-responsiveness of the ELP provided a designable generic biosurface for diagnostic detection.