A glassy carbon electrode modified with graphene oxide, poly(3,4-ethylenedioxythiophene), an antifouling peptide and an aptamer for ultrasensitive detection of adenosine triphosphate

A Brief Review of Aptamer-Based Biosensors in Recent Years

Aptamers have recently become novel probes for biosensors because of their good biocompatibility, strong specificity, and high sensitivity. Biosensors based on peptides or nucleic acid aptamers are used in implantable and wearable devices owing to their ease of synthesis and economic efficiency. Simultaneously, amphoteric ionic peptides are being explored as antifouling layers for biosensors resistant to interference from extraneous proteins in serum. Thus, this paper reviews recently developed aptamer-based biosensors and introduces peptide- and nucleic acid-based biosensors, while focusing on the three primary classes of biosensors: electrochemical sensors, fluorescent or colorimetric biosensors, and electroluminescent sensors. Furthermore, we summarize their general construction strategies, describe specific electrochemical sensors that use peptides as an antipollution layer, and elucidate their advantages.

A dual-mode electrochemical biosensor based on GO-Fe3O4 doped PEDOT nanocomposite for the ultrasensitive assay of microRNA

MicroRNA, as a distinctive biomarker, plays a crucial role in the early prognosis and diagnosis of numerous severe diseases. However, due to its inherent properties such as low abundance, small size, and high sequence similarity, the sensitive and accurate detection of microRNA remains a major challenge. Herein, a dual-mode electrochemical biosensing platform was developed for microRNA detection, based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide-Fe3O4 (GO-Fe3O4) nanocomposite. The GO-Fe3O4/PEDOT composite demonstrated a porous microstructure, outstanding conductivity, and robust catalytic activity towards nitrite. It was electrodeposited onto the electrode surface in a one-step process using the cyclic voltammetry method (CV). The microRNA biosensor was obtained by anchoring DNA with amino groups to the GO-Fe3O4/PEDOT layer through the formation of amide bonds. The designed dual-mode microRNA biosensor demonstrated a broad linear range spanning from 10-15 M to 10-6 M, with low detection limits of 5.18 × 10-15 M and 7.36 × 10-15 M when using chronocoulometry (CC) and amperometric i-t curve (i-t) modes, respectively. Furthermore, a dual-mode electrochemical biosensor has been successfully developed and utilized for the detection of microRNA in human serum, demonstrating its potential for precise and sensitive microRNA detection and its practical application value in clinical medicine.

In situ anchored ternary hierarchical hybrid nickel@cobaltous sulfide on poly(3,4-ethylenedioxythiophene)-reduced graphene oxide for highly efficient non-enzymatic glucose sensing

A ternary hierarchical hybrid Ni@CoxSy/poly(3,4-ethylenedioxythiophene)-reduced graphene oxide (Ni@CoxSy/PEDOT-rGO) is rationally designed and in situ facilely synthesized as electrocatalyst to construct a binder-free sensing platform for non-enzymatic glucose monitoring through traditional electrodeposition procedure. The as-prepared Ni@CoxSy/PEDOT-rGO presents unique hierarchical structure and multiple valence states as well as strong and robust adhesion between Ni@CoxSy/PEDOT-rGO and GCE. Profiting from the aforementioned merits, the sensing platform constructed under optimal conditions achieved a wide detection range (0.2 μM ~ 2.0 mM) with high sensitivity (1546.32 μA cm-2 mM-1), a rapid response time (5 s), an ultralow detection limit (0.094 μM), superior anti-interference performance, excellent reproducibility and considerable stability. Furthermore, the sensor demonstrates an acceptable accuracy and appreciable recoveries ranging from 90.0 to 102.0% with less than 3.98% RSD in human blood serum samples, indicating the prospect of the sensor for the real samples analysis. It will provide a strategy to rationally design and fabricate ternary hierarchical hybrid as nanozyme for glucose assay.

Conjugated Polymers for Aptasensing Applications

Rapid and specific assaying of molecules that report on a pathophysiological condition, environmental pollution, or drug concentration is pivotal for establishing efficient and accurate diagnostic systems. One of the main components required for the construction of these systems is the recognition element (receptor) that can identify target analytes. Oligonucleotide switching structures, or aptamers, have been widely studied as selective receptors that can precisely identify targets in different analyzed matrices with minimal interference from other components in an antibody-like recognition process. These aptasensors, especially when integrated into sensing platforms, enable a multitude of sensors that can outperform antibody-based sensors in terms of flexibility of the sensing strategy and ease of deployment to areas with limited resources. Research into compounds that efficiently enhance signal transduction and provide a suitable platform for conjugating aptamers has gained huge momentum over the past decade. The multifaceted nature of conjugated polymers (CPs), notably their versatile electrical and optical properties, endows them with a broad range of potential applications in optical, electrical, and electrochemical signal transduction. Despite the substantial body of research demonstrating the enhanced performance of sensing devices using doped or nanostructure-embedded CPs, few reviews are available that specifically describe the use of conjugated polymers in aptasensing. The purpose of this review is to bridge this gap and provide a comprehensive description of a variety of CPs, from a historical viewpoint, underpinning their specific characteristics and demonstrating the advances in biosensors associated with the use of these conjugated polymers.

Effect of Secondary Structures on the Adsorption of Peptides onto Hydrophobic Solid Surfaces Revealed by SALDI-TOF and MD Simulations

The adsorption of peptides and proteins on hydrophobic solid surfaces has received considerable research attention owing to their wide applications to biocompatible nanomaterials and nanodevices, such as biosensors and cell adhesion materials with reduced nanomaterial toxicity. However, fundamental understandings about physicochemical hydrophobic interactions between peptides and hydrophobic solid surfaces are still unknown. In this study, we investigate the effect of secondary structures on adsorption energies between peptides and hydrophobic solid surfaces via experimental and theoretical analyses using surface-assisted laser desorption/ionization-time-of-flight (SALDI-TOF) and molecular dynamics (MD) simulations. The hydrophobic interactions between peptides and hydrophobic solid surfaces measured via SALDI-TOF and MD simulations indicate that the hydrophobic interaction of peptides with random coil structures increased more than that of peptides with an α-helix structure when polar amino acids are replaced with hydrophobic amino acids. Additionally, our study sheds new light on the fundamental understanding of the hydrophobic interaction between hydrophobic solid surfaces and peptides that have diverse secondary structures.

Electrochemical aptasensor based on electrodeposited poly(3,4-ethylenedioxythiophene)-graphene oxide coupled with Au@Pt nanocrystals for the detection of 17β-estradiol

An electrochemical aptasensor is reported for the sensitive and specific monitoring of 17β-estradiol (E2) based on the modification of electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT)-graphene oxide (GO) coupled with Au@Pt nanocrystals (Au@Pt). With excellent conductivity, chemical stability and active sites, the PEDOT-GO nanocomposite film was firstly in situ polymerized on the glassy carbon electrode by cyclic voltammetry. Subsequently, one-step synthesized Au@Pt were decorated on the conductive polymer, providing a platform for immobilizing the aptamer and enhancing the detecting sensitivity. With the addition of E2, since the interfacial electron transfer process was retarded by the E2-aptamer complex, the differential pulse voltammetry signal decreased gradually. Under optimum conditions, the calibration curve of E2 exhibited a linear range between 0.1 pM and 1 nM, with a low detection limit (S/N = 3) of 0.08 pM. The developed aptasensor showed admiring selectivity, stability, and reproducibility. It was tested in human serum, lake water and tap water samples after low-cost and simple pretreatment. Consequently, the developed platform could provide a new design thought for ultrasensitive detection of E2 in clinical and environmental samples.

Graphene-family materials in electrochemical aptasensors

The study of graphene-based carbon nanocomposites has remarkably increased in recent years. Functionalized graphene-based nanostructures, including graphene oxide and reduced graphene oxide, have great potential as new innovative electrode materials in the fabrication of novel electrochemical sensors. Electrochemical sensors based on aptamers attracted great attention because of their high sensitivity and selectivity, and simple instrumentation, as well as low production cost. Aptamers as a potent alternative to antibodies are functional nucleic acids with a high tendency to specific analytes. Electrochemical aptasensors show specific recognition ability for a wide range of analytes. Although aptamers are selected in vitro in contrast to antibodies, they are interesting due to advantages like high stability, easy chemical modifications, and the potential to be employed in nanostructured device fabrication or electrochemical sensing devices. Recently, new nanomaterials have shown a significant impact on the production of electrochemical sensors with high efficiency and performance. This review aims to give an outline of electrochemical aptasensors based on the graphene family materials and discuss the detection mechanism in this type of aptasensors. The present review summarizes some of the recent achievements in graphene-based aptasensors and includes their recent electroanalytical applications. Graphical Abstract Graphical Abstract.

Electrochemical biosensors based on nucleic acid aptamers

During recent decades, nucleic acid aptamers have emerged as powerful biological recognition elements for electrochemical affinity biosensors. These bioreceptors emulate or improve on antibody-based biosensors because of their excellent characteristics as bioreceptors, including limitless selection capacity for a large variety of analytes, easy and cost-effective production, high stability and reproducibility, simple chemical modification, stable and oriented immobilization on electrode surfaces, enhanced target affinity and selectivity, and possibility to design them in target-sensitive 3D folded structures. This review provides an overview of the state of the art of electrochemical aptasensor technology, focusing on novel aptamer-based electroanalytical assay configurations and providing examples to illustrate the different possibilities. Future prospects for this technology are also discussed. Graphical abstract.

A review on peptide functionalized graphene derivatives as nanotools for biosensing

Peptides exhibit unique binding behavior with graphene and its derivatives by forming bonds on its edges and planes. This makes them useful for sensing and imaging applications. This review with (155 refs.) summarizes the advances made in the last decade in the field of peptide-GO bioconjugation, and the use of these conjugates in analytical sciences and imaging. The introduction emphasizes the need for understanding the biotic-abiotic interactions in order to construct controllable peptide-functionalized graphitic material-based nanotools. The next section covers covalent and non-covalent interactions between peptide and oxidized graphene derivatives along with a discussion of the adsorption events during interfacing. We then describe applications of peptide-graphene conjugates in bioassays, with subsections on (a) detection of cancer cells, (b) monitoring protease activity, (c) determination of environmental pollutants and (d) determination of pathogenic microorganisms. The concluding section describes the current status of peptide functionalized graphitic bioconjugates and addresses future perspectives. Graphical abstractSchematic representation depicting biosensing applications of peptide functionalized graphene oxide.

A review on recent advancements in electrochemical biosensing using carbonaceous nanomaterials

This review, with 201 references, describes the recent advancement in the application of carbonaceous nanomaterials as highly conductive platforms in electrochemical biosensing. The electrochemical biosensing is described in introduction by classifying biosensors into catalytic-based and affinity-based biosensors and statistically demonstrates the most recent published works in each category. The introduction is followed by sections on electrochemical biosensors configurations and common carbonaceous nanomaterials applied in electrochemical biosensing, including graphene and its derivatives, carbon nanotubes, mesoporous carbon, carbon nanofibers and carbon nanospheres. In the following sections, carbonaceous catalytic-based and affinity-based biosensors are discussed in detail. In the category of catalytic-based biosensors, a comparison between enzymatic biosensors and non-enzymatic electrochemical sensors is carried out. Regarding the affinity-based biosensors, scholarly articles related to biological elements such as antibodies, deoxyribonucleic acids (DNAs) and aptamers are discussed in separate sections. The last section discusses recent advancements in carbonaceous screen-printed electrodes as a growing field in electrochemical biosensing. Tables are presented that give an overview on the diversity of analytes, type of materials and the sensors performance. Ultimately, general considerations, challenges and future perspectives in this field of science are discussed. Recent findings suggest that interests towards 2D nanostructured electrodes based on graphene and its derivatives are still growing in the field of electrochemical biosensing. That is because of their exceptional electrical conductivity, active surface area and more convenient production methods compared to carbon nanotubes. Graphical abstract Schematic representation of carbonaceous nanomaterials used in electrochemical biosensing. The content is classified into non-enzymatic sensors and affinity/ catalytic biosensors. Recent publications are tabulated and compared, considering materials, target, limit of detection and linear range of detection.

Biomedical Application of Electroactive Polymers in Electrochemical Sensors: A Review

Conducting polymers are of interest due to their unique behavior on exposure to electric fields, which has led to their use in flexible electronics, sensors, and biomaterials. The unique electroactive properties of conducting polymers allow them to be used to prepare biosensors that enable real time, point of care (POC) testing. Potential advantages of these devices include their low cost and low detection limit, ultimately resulting in increased access to treatment. This article presents a review of the characteristics of conducting polymer-based biosensors and the recent advances in their application in the recognition of disease biomarkers.