RESUMO

An innovative strategy is proposed to simultaneously exfoliate multi-walled carbon nanotubes (MWCNTs) and generate MWCNTs with immunoaffinity properties. This strategy was based on the non-covalent functionalization of MWCNTs with human immunoglobulin G (IgG) by sonicating 2.5 mg mL-1 MWCNTs in 2.0 mg mL-1 IgG for 15 min with sonicator bath. Impedimetric experiments performed at glassy carbon electrodes (GCE) modified with the resulting MWCNT-IgG nanohybrid in the presence of anti-human immunoglobulin G antibody (Anti-IgG) demonstrated that the immunoglobulin retains their biorecognition properties even after the treatment during the MWCNT functionalization. We proposed, as proof-of-concept, two model electrochemical sensors, a voltammetric one for uric acid quantification by taking advantages of the exfoliated MWCNTs electroactivity (linear range, 5.0 × 10-7 M - 5.0 × 10-6 M; detection limit, 165 nM) and an impedimetric immunosensor for the detection of Anti-IgG through the use of the bioaffinity properties of the IgG present in the nanohybrid (linear range, 5-50 µg mL-1; detection limit, 2 µg mL-1).

Assuntos

Técnicas Biossensoriais , Nanotubos de Carbono , Humanos , Técnicas Biossensoriais/métodos , Nanotubos de Carbono/química , Imunoensaio , Imunoglobulina G , Eletrodos

RESUMO

A multilayered iron oxide/reduced graphene oxide (ION-RGO) nanocomposite electrode is reported for the voltammetric sensing of bisphenol-A (BPA). Structural characterizations reveal the nanocomposite features RGO sheets decorated with nanometric spherical ION in a mixture of maghemite and magnetite phases. ITO substrate modified with the ION-RGO multilayered film exhibits strong electrocatalytic effect toward BPA oxidation, which is made possible by Fe(III) catalysts generated at the ION's surface after scanning the electrode potential from below 0 V (vs Ag/AgCl) and followed by the RGO phase conducting the transferred electrons. Under optimized differential pulse voltammetry conditions, the proposed sensor shows three linear working ranges 0.09-1.17 (r2 = 0.999), 1.17-3.81 (r2 = 0.995) and 3.81-8.20 (r2 = 0.998), with the highest sensitivity equaling 7.76 µA cm-2/µmol L-1 and the lowest limit of detection of 15 nmol L-1. A single electrode can be used for at least twenty consecutive runs loosing less than 15% of sensitivity, whereas electrodes fabricated in different bacthes exhibit almost identical perfomances. Determination of BPA in a thermal paper sample shows no difference (at 95% confidence level) between the proposed sensor and HPLC/UV. The sensor is neither influenced by the matrix composition nor by other emerging contaminants.