Greenness assessment of a molecularly imprinted polymeric sensor based on a bio-inspired polymer

Abstract

Methyldopa, a synthesized dopamine substitute with phenolic, amine, and carboxylic groups, was used to create a selective molecular imprinted polymer (MIP) for detecting formoterol fumarate dihydrate (FFD), a long-acting beta2-agonist for asthma and COPD. The bio-inspired polymer (MD) was electro-grafted onto a pencil graphite electrode (PGE) using cyclic voltammetry in a phosphate buffer (pH 6.5). An indirect method involving a redox probe (ferrocyanide/ferricyanide) and differential pulse voltammetry measured FFD binding to the MIP's 3D cavities. The sensor showed a linear response range from 1 × 10⁻⁹ M to 2 × 10⁻¹⁰ M, with a detection limit of 1.7 × 10⁻¹¹ M. The polymethyldopa (PMD) and FFD interaction was assessed by UV spectroscopy, and the method was validated per ICH guidelines. Green analytical approaches, including RGB and GAPI, were also implemented. The goal was to use advances in molecularly imprinted polymers to develop a more precise and selective electrochemical sensor for FFD quantification.

Keywords: Electrochemical sensors, Green analytical procedure index, red green blue model; Formoterol; Molecularly-imprinted polymers; Mussel-inspired polymers; Poly (methyldopa).

Fig. 1

Chemical structure of formoterol fumarate dihydrate

Fig. 2

The UV spectra of the template: formoterol fumarate, monomer methyldopa, the equimolar mixture of both, and the calculated sum of formoterol and methyldopa

Fig. 3

Cyclic voltammograms of electro-polymerization process of methyldopa over 10 cycles with a scan rate of 130 mV/S

Fig. 4

The cyclic voltammograms of the same electrode for a redox probe solution (equimolar 5 mM [Fe (CN) 6]^3−/4− in 0.1 M KCl) after polymerization, after washing, and after rebinding

Fig. 5

The X-ray photoelectron survey spectrum of the PGE/PMD modified electrode showing three prominent peaks for C 1s, N 1s, and O 1s

Fig. 6

The various parameters optimization that affect the polymerization process of methyldopa (A): polymerization pH, (B): scan rate, (C): number of cycles

Fig. 7

Differential pulse voltammograms of redox probe (equimolar of 5 mM [Fe (CN) ₆]^3−/4− in 0.1 M KCl) at MIP/PGE surface in the presence of various concentrations of FFD ranging from (2 × 10^− 10 M to 1 × 10^− 9 M) performed at optimum conditions

Fig. 8

Calibration curve of FFD concentrations ranging from (2 × 10^− 10 M to 1 × 10^− 9 M) performed at the optimized conditions

Fig. 9

GAPI assessment pictogram generated for the evaluation of proposed method’s greenness (A) and the reported method (B) ^[25]

Fig. 10

The comparison between the results obtained from RGB model for the developed and reported method