An impedance biosensor is reported that employs the bidentate thiol, 16-[3,5-bis(mercaptomethyl)phenoxy]-hexadecanoic acid (BMPHA), as a bifunctional reagent for antibody immobilization atop an Au electrode, and the results are compared to those obtained for the analogous monodentate reagent, 16-mercaptohexadecanoic acid (16 MHA). The detection limit for peanut protein Ara h 1 on the BMPHA bidentate thiol-coated Au electrode is approximately 0.71 ng/mL (0.01 nM), about 3x lower than that obtained on the comparable monodentate (16-MHA) thiol-coated Au electrode. Daily impedance measurements were employed to study antibody regeneration with a mild denaturing agent, 0.2 M KSCN at pH 7.3. The antibody-coated electrodes retained activity toward Ara h1 for 10 and 20 days of regeneration of the monodentate-and BMPHA-coated Au electrodes, respectively, illustrating the superior stability of protein films atop the BMPHA bidentate thiol. (C) 2016 The Electrochemical Society. All rights reserved.