1This article studies the synthesis and properties of copolymers of aniline and both 2-amino (2ABSA) and 3-aminobenzenesulfonic acids (3ABSA) with a molar degree of sulfonation from 3 to 33% for 3ABSA and 10 to 43% for 2ABSA. The small segments of the sulfonic species in the polymer chain (molar fraction = 0.03) confer solubility in alkaline medium (around 0.012 g L-1) and good electrochemical response at pH 7.2 improving those for the unmodified polyaniline (PANI). Taking advantage of the electroactivity at physiological pH, the electrochemical response of redox couples (ferrocyanide(II)/ferricyanide(III) and ferrocene/ferrocenium) has been anal, sed. The electrochemical response of Cytochrome c (Cyt c) solutions has been also studied at pH 7.2 in presence and absence of ferrocene/ferrocenium species. (c) 2006 Elsevier Ltd. All rights reserved.