An electrochemical sensor based on MWCNTs and a PCCN222 peroxidase-like nanocomposite for sensitive and selective kaempferol detection

Abstract

Kaempferol (KA) is a flavonoid with a range of biological properties, including antitumor, antioxidant, antiviral and anti-inflammatory, and its extensive applications in biomedicine, food safety, and related fields underscore the importance of quantitative analysis for determining its concentration. In this study, an electrochemical sensor based on multi-walled carbon nanotubes (MWCNTs), PCN₂₂₂ and chitosan (CS) was developed for the determination of KA. MWCNTs exhibit hydrophobicity and conductivity, and they are better dispersed by DMF and crosslinked with PCN₂₂₂, which further improves the electrode's response, selectivity and sensitivity to KA due to the peroxide-like properties of PCN₂₂₂. The film formed by CS on the electrode surface serves to protect the nanocomposite from detaching during the operation. The linear range of this sensor is 0.01-0.4 and 0.6-9 μM, with a detection limit of 4.16 nM. This method can be used to detect the content of KA in plasma, which shows that the electrochemical sensor has strong practical application capabilities, as well as other advantages, such as high stability, strong anti-interference ability, and low detection limit. Moreover, the ultraviolet-visible spectrophotometer (UV) demonstrates that the catalytic rate of PCN₂₂₂ for KA is significantly faster than that for naringenin and puerarin. Therefore, the construction of CS/MWCNT-PCN₂₂₂/GCE electrochemical sensors has potential application value for clinical dosage control and monitoring of the drug metabolism of KA.

Fig. 1. Preparation scheme of CS/MWCNT–PCN₂₂₂/GCE.

Fig. 2. SEM images of MWCNTs (a), DMF-MWCNTs (b), PCN₂₂₂ (c), MWCNT–PCN₂₂₂ (d and e), and CS-MWCNT–PCN₂₂₂ (f) at 5 kV, and EDS spectrum of MWCNT–PCN₂₂₂ nanocomposite material (g).

Fig. 3. EIS of bare GCE, CS/MWCNTs/GCE, and CS/MWCNT–PCN₂₂₂/GCE in 0.1 M KCl solution containing 5 mM [Fe(CN)₆]^3−/4−. (Illustration: Randles equivalent circuit).

Fig. 4. (a) CVs of different modified GCEs in 50 mM pH 5 PBS containing 5 μM KA at a scan rate of 100 mV s⁻¹ (where a′, b′, and c′ are bare GCE, CS/MWCNTs/GCE, and CS/MWCNT–PCN₂₂₂/GCE, respectively). (b) Oxidation peak current of different modified electrodes in 10 μM KA.

Fig. 5. (a) CVs of CS/MWCNT–PCN₂₂₂/GCE to 5 μM KA at different scan speeds in PBS at 50 mM pH 5.0. (b) Relationship between peak current and scanning speed. (c) Linear relationship between oxidation peak potential E_pa and ln v.

Fig. 6. Electrochemical reaction mechanism of KA.

Fig. 7. (a) Effects of pH value the CVs of CS/MWCNT–PCN₂₂₂/GCE in 50 mM PBS 5 μM KA at a scan rate of 100 mV s⁻¹. (b) Relationship between pH value and oxidation peak current. (c) Linear relationship between peak oxidation potential E_pa and buffer pH.

Fig. 8. (a) DPV response of CS/MWCNT–PCN₂₂₂/GCE to different concentrations of KA. (b) Relationship between peak oxidation current and concentration of KA.

Fig. 9. (a) Response of five independent electrodes prepared in 50 mM, pH 5.0 PBS to the oxidation peak current of 1 μM KA. (b) DPV response of the same modified electrode to 5 μM KA. (c) Storage stability of the CS/MWCNT–PCN₂₂₂/GCE.

Fig. 10. UV spectra of continuous scanning (a) PCN₂₂₂-KA-H₂O₂, (b) PCN₂₂₂-puerarin-H₂O₂ and (c) PCN₂₂₂-naringenin-H₂O₂. (d) ΔA versus time in 50 mM pH 5 PBS containing PCN₂₂₂, H₂O₂, and different flavonoids (KA, puerarin and naringenin). (Illustration: (a) HRP-KA-H₂O₂, (b) HRP-puerarin-H₂O₂ and (c) HRP-naringenin-H₂O₂.) (d) ΔA versus time in 50 mM pH 5 PBS containing PCN₂₂₂, H₂O₂, and different flavonoids (KA, puerarin and naringenin). (e) Anti-interference ability of CS/MWCNT–PCN₂₂₂/GCE in 50 mM pH 5 PBS containing 50 μM different interfering substances (Glu, UA, Vb1, AA, KCl, and NaCl), 2 μM flavonoids interfering substances (puerarin and naringenin) and 2 μM KA (pink).