The Role of Surface Chemistry in Impedimetric Aptasensing

Abstract

Surface chemistry is a key parameter in the choice of proper materials for electrochemical detection. It has been previously shown that the presence of oxygen containing groups (OCGs) on the surface of graphene oxide (GO) can be both effective and detrimental. This poses a question when GO materials are used as electrochemical platforms for biosensing. In this work, we study how the surface chemistry of graphene oxide nanocolloids (GONCs) affects the impedimetric biosensing of ochratoxin A (OTA), in terms of immobilization of biorecognition element and detection step. OCGs on GONCs were tuned by applying increasing reduction potentials from −0.3 V to −1.2 V, resulting in GONC platforms with decreasing amounts of oxygen functionalities. It was discovered that the sensitivity of biosensing is correlated to the residual amount of OCGs on GO surface. For a more detailed investigation, three representative materials, namely unreduced GONCs, as well as GONCs reduced at potentials of −0.8 V and −1.2 V were chosen. Results were compared in terms of calibration sensitivity, selectivity and reproducibility of the impedimetric response. GONCs reduced at −1.2 V have shown the best electroanalytical response for the impedimetric detection of OTA. These findings are anticipated to contribute to the design of novel biosensors, whereby an optimized platform is employed for the immobilization of the biorecognition element.

Unravelling the Aptamer‐Analyte Interaction Dynamics through Fluorescence Quenching in Graphene Quantum Dots (GQDs) Based Homogeneous Assays

“…It is well known that the interactions between the platform and the biorecognition element play a key role in the bio‐conjugation process. Specifically, the latter could be strongly influenced by the surface functionalization of the material used as biosensing platform . In order to gain more insights into the presence and amount of functional groups on the material, characterisation of GQDs was first carried out by X‐ray photoelectron spectroscopy (XPS) as well as Fourier Transform Infrared Spectroscopy (FT‐IR).…”

Advances on the Use of Graphene as a Label for Electrochemical Biosensors

“…By applying negative potentials to an oxidized graphene surface, a cathodic peak is observed (see Figure A), which is due to the reduction of the electroactive oxygen functionalities on the material . XPS characterization carried out before and after the electrochemical treatment showed a clear increase in the C/O ratio of the material, thus confirming the reduction of the electroactive OCGs on GO surface (see Figure C and D) . This ‘intrinsic electroactivity’ of graphene oxide was exploited for the first time by Bonanni et al.…”

“…One of the greatest challenges that are faced when developing a biosensor include the formation of a stable and specific layer of the biorecognition element. In order to achieve that on graphene surface: different functionalization strategies have been explored and compared, including physical adsorption, conjugation by covalent bonds or by the formation of affinity interactions (see Figure B); topological constraint of immobilized biorecognition elements have been investigated (see one example of DNA probe immobilization from different soldering points shown in Figure C); the kind and amount of surface functional groups have been tuned during graphene synthesis for the optimization of the bio‐conjugation process; large area CVD single‐layer graphene has been employed especially for biosensors based on for field effect transistors (see an example of bacteria detection on graphene‐FET modified with anti‐ E. coli antibody in Figure D) …”

Two-Dimensional Layered Nanomaterial-Based Electrochemical Biosensors for Detecting Microbial Toxins

“…In addition, high concentrations of OTA has certain hepatotoxicity. During the last 5 years, several 2D nanomaterial-based electrochemical biosensors including immunosensors and aptasensors have also been developed for sensing OTA [118][119][120][121][122][123][124][125][126][127][128][129][130][131]. For instance, a series of aptasensors based on rGO-AuNP nanocomposites have been constructed by Wang's group [118][119][120].…”