Molecular frameworks of polymerized 3-aminobenzoic acid for chemical modification and electrochemical recognition

The main purpose of this work is to provide insight into the molecular frameworks that are the products of 3-aminobenzoic acid (3ABA) polymerization. The employment of vibrational spectroscopic (FTIR and FT Raman) and mass spectrometric (MS) methods enabled us to determine the structures of oligomers that form during both the chemical and electrochemical oxidative polymerization of 3ABA. It was found that i) the intermolecular connections in the nanolayer were realized through amino groups similarly to the aniline polymerization mechanism, ii) the carboxyl groups of 3ABA were not significantly damaged during polymerization, which was important for their subsequent post-modification by 3-aminophenylboronic acid (3APBA); the presence of both amino and phenolic groups on oligomeric backbones was responsible for appropriate acid-base behaviour and also for the N-acetylneuraminic acid (NANA) recognition that occurred between the modified electrode surface and the tested solutions, in which both pH and NANA content varied. The pH sensitivity of oligomers deposited onto a platinum disc electrode observed during potentiometric measurements additionally confirmed the presence of groups (in particularly, carboxyl and amino groups) taking part in acid-base equilibrium and contributing to the recognition process. The ability of modified oligomers to detect NANA was proved using electrochemical impedance spectroscopy (EIS) and potentiometry in the range from 25 pM up to 741 pM NANA at pH 7, independently of the measuring technique.