Electroactive polymers for the detection of morphine

Abstract

The interaction between morphine (MO), a very potent analgesic psychoactive drug, and five electroactive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-methylthiophene) (P3MT), polypyrrole (PPy), poly(N-methylpyrrole (PNMPy) and poly[N-(2-cyanoethyl)pyrrole] (PNCPy), has been examined using theoretical calculations on model complexes and voltammetric measures considering different pHs and incubation times. Quantum mechanical calculations in model polymers predict that the strength of the binding between the different polymers and morphine increases as follows: PEDOT < PNMPy < Py < < P3MT a parts per thousand PNCPy. The most relevant characteristic of P3MT is its ability to interact with morphine exclusively through non-directional interactions. On the other hand, the variations of the electroactivity and the anodic current at the reversal potential evidence that the voltammetric response towards the presence of MO is considerably higher for P3MT and PNCPy than that for the other polymers at both acid (P3MT > PNMPy) and neutral (P3MT a parts per thousand PNCPy) pHs. Energy decomposition analyses of the interaction of MO with different model polymers indicate that the stronger affinity of MO for P3MT and PNCPy as compared to PEDOT, PNMPy, and PPy is due to more favorable orbital interactions. These more stabilizing orbital interactions are the result of the larger charge transfer from MO to P3MT and PNCPy model polymers that takes place because of the higher stability of the single occupied molecular orbital (SOMO) of these model polymers. Therefore, to design polymers with a large capacity to detect MO we suggest looking at polymers with high electron affinity