Development of Polydiphenylamine@Electrochemically Reduced Graphene Oxide Electrode for the D-Penicillamine Sensor from Human Blood Serum Samples Using Amperometry

Abstract

D-penicillamine (PA) is a sulfur group-containing drug prescribed for various health issues, but overdoses have adverse effects. Therefore, regular, selective, and sensitive sensing is essential to reduce the need for further treatment. In this study, diphenylamine (DPA) was electropolymerized in an aqueous acidic medium. The PA detection sensitivity, selectivity, and limit of detection were enhanced by electropolymerizing DPA on an electrochemically reduced graphene oxide (ERGO)/glassy carbon (GC) surface. The formation of p-DPA and ERGO was investigated using various techniques. The as-prepared p-DPA@ERGO/GC revealed the excellent redox-active (N-C to N=C) sites of p-DPA. The p-DPA@ERGO/GC electrode exhibited excellent electrochemical sensing ability towards PA determination because of the presence of the -NH-functional moiety and effective interactions with the -SH group of PA. The p-DPA@ERGO/GC exhibited a high surface coverage of 9.23 × 10^-12 mol cm^-2. The polymer-modified p-DPA@ERGO/GC electrode revealed the amperometric determination of PA concentration from the 1.4 to 541 μM wide range and the detection limit of 0.10 μM. The real-time feasibility of the developed p-DPA@ERGO/GC electrode was tested with a realistic PA finding in human blood serum samples and yielded a good recovery of 97.5-101.0%, confirming the potential suitability in bio-clinical applications.

Keywords: D-penicillamine; cyclic voltammetry; electrochemically reduced graphene oxide; electropolymerization; polydiphenylamine.

Figure 1

Chemical structure of (a) N,N-Diphenylamine; (b) D-Penicillamine; and (c) Poly(diphenylamine).

Scheme 1

Stepwise p-DPA@ERGO/GC electrode preparation.

Figure 2

(A) GO electrochemical reduction CV curve trace in 0.2 M PBS (pH 7.2) at a sweep rate of 50 mV s⁻¹; (B) electropolymerization of DPA on ERGO/GC in a 0.1 M H₂SO₄ contains 1 mM DPA monomer at a 50 mV s⁻¹ scan rate.

Figure 3

DPA stepwise electropolymerization reaction mechanism.

Figure 4

(A) Raman spectra of (a) GO and (b) ERGO; (B–D) FESEM of GO (B), ERGO (C), and p-DPA@ERGO (D); (E) high magnification image of p-DPA@ERGO.

Figure 5

(A) XPS survey spectrum of (a) GO, (b) ERGO, and (c) p-DPA@ERGO; (B,E) GO C 1s and O 1s; (C,F) ERGO C 1s and O 1s; (D,G) p-DPA@ERGO/GC C 1s and O 1s region spectra.

Figure 6

(A) CV scan rates of p-DPA@ERGO/GC in 0.1 M H₂SO₄ from 5 to 500 mV s⁻¹, (B) corresponding plot of peak current (I) versus scan rate; (C,D) electrochemical impedance spectroscopy and CV of (a) bare GC, (b) p-DPA/GC, and p-DPA@ERGO/GC in [Fe(CN)₆]^3−/4− (5 mM) solution of 0.1 M KCl; (E) CV trace of (a) bare GC, (b) activated GC, (c) p-DPA/GC, and (d) ERGO/GC, and (e) p-DPA@ERGO/GC-modified electrodes in the absence of analyte and a′, b′, c′, d′, and e′ in the presence of 1 mM PA with 0.1 M PBS at a 50 mV s⁻¹ scan rate; (F) scan rate effect of the p-DPA@ERGO/GC electrode in PA concentration of 1 mM.

Scheme 2

Possible electrochemical oxidation mechanism of PA at the p-DPA@ERGO/GC electrode.

Figure 7

(A) DPV curves of different PA concentrations (a) 10.0, (b) 60.0, (c) 108.8, (d) 205.6, (e) 393.8, (f) 663.0, (g) 999.0, (h) 1386.7, (i) 810, (j) 2254.0, (k) 2706.5, (l) 3155.3, (m) 3593.8, and (n) 4015.5 μM; (B) calibration plot of the PA oxidation current versus concentration (pH 7.2); (C) amperometric (i–t) measurements for current steps upon the addition of PA from 1.4 to 541 μM on p-DPA@ERGO/GC-modified electrode with an applied potential of +0.62 V; (D) calibration plot of the current versus PA concentration.