Electrochemical Aptasensor with Layer‐by‐layer Deposited Polyaniline for Aflatoxin M1 Voltammetric Determination

Abstract

Mycotoxins are highly toxic metabolites of some fungi that frequently contaminate water, food and feed and hence cause several human and animal diseases. In this work, a new approach to the fast and reliable determination of aflatoxin M1 (AFM1) in water and milk has been proposed with reagent free protocol of signal measurement. For this purpose, DNA aptamer selective to AFM1 was entrapped between two thin layers of polyaniline (PANI) electrodeposited on glassy carbon electrode. The incubation of the aptasensor in the AFM1 solution results in remarkable decrease of the PANI intrinsic activity monitored by direct current voltammetry or electrochemical impedance spectroscopy. Appropriate calibration curves were linear in the range from 3 to 90 ng/L with limit of detection (LOD) 1–5 ng/L depending on the measurement mode. Mechanism of signal generation involves shielding electrostatic interactions between the PANI and aptamer in the surface layer and variation of its redox activity attributed to the emeraldine form of PANI. Selectivity of the response was proved by similar experiments with aflatoxin B1 and ochratoxin A and by comparison of the results with those obtained with non‐specific aptamer in the sensing layer. Simple protocol for milk pretreatment has been proposed for reliable detection of AFM1 on the level of its threshold limited values (20 ng/L).

Hierarchical engineering of Mn2O3/carbon nanostructured electrodes for sensitive screening of acetylcholine in biological samples

“…The surface charge resistance (Rct) is represented by the semicircle outlines, while the electron diffusion velocity is represented by lines. 61–65 The Mn 2 O 3 FL/C/GCE displayed a low semicircle and high line pathway. While the GCE and Mn 2 O 3 NLs/C/GCE showed a high semicircle and low line pathway.…”

“…The EIS measurements are one of the tools that are used for outlining the electrochemical properties of the fabricated electrodes. 49,60–62 The EIS examination of GCE, Mn 2 O 3 NLs/C/GCE, and Mn 2 O 3 FL/C/GCE showed the surface resistance and electron diffusion pathways. Fig.…”

Impedimetric Determination of Kanamycin in Milk with Aptasensor Based on Carbon Black-Oligolactide Composite

“…The equivalent circuit chosen ascribes the charge transfer conditions that take place on the electrode covered with a rather thick permeable layer so that two independent equillibria exist on the inner and outer interface of the modifying layer. Previously, the formation of two semicircles was observed in impedimetric biosensors utilizing bulky nonconductive but charged molecules like DNA [ 33 , 48 ] or antibodies [ 49 , 50 ], which are able to form differently charged areas in close proximity to the electrode interface. The specific form of the Nyquist diagrams and its relation to the heterogeneity of the surface layer and its properties is discussed in [ 51 , 52 ].…”

Advances in Electrochemical Aptasensors Based on Carbon Nanomaterials

“…The aptamers commonly bear negative charge related to the phosphate residues of the backbone and hence they can be rather easily accumulated on positively charge carriers. For this purpose, some polyelectrolytes, such as poly(ethylene imine) (PEI) [103,104], poly(diallyldimethylammonium chloride) (PDDA) or polyaniline [105], are used as a kind of molecular "glue" combining oppositely charged components of the surface layer (e.g., carboxylated carbonaceous materials and aptamers). Electrostatic assembling is governed by the charge density and flexibility of the charge carriers and is also affected by small ions present in the solution as a supporting electrolyte.…”

“…The above description does not exhaust the variety of the methods for monitoring aptamer-analyte interactions described in the aptasensors using carbon nanomaterials. Thus, the intrinsic redox activity of electroactive polymers such as polyaniline and polypyrrole changes with analyte binding due to variation of the charge distribution and counter ion access within the polymer layer [105]. In some cases, aptamer acts as a specific sorbent and accumulates analyte molecules for their following oxidation on electrode.…”