Ultrasensitive electrochemical immunoassay for BRCA1 using BMIM·BF₄-coated SBA-15 as labels and functionalized graphene as enhancer

Strategies and Applications of Graphene and Its Derivatives-Based Electrochemical Sensors in Cancer Diagnosis

Graphene is an emerging nanomaterial increasingly being used in electrochemical biosensing applications owing to its high surface area, excellent conductivity, ease of functionalization, and superior electrocatalytic properties compared to other carbon-based electrodes and nanomaterials, enabling faster electron transfer kinetics and higher sensitivity. Graphene electrochemical biosensors may have the potential to enable the rapid, sensitive, and low-cost detection of cancer biomarkers. This paper reviews early-stage research and proof-of-concept studies on the development of graphene electrochemical biosensors for potential future cancer diagnostic applications. Various graphene synthesis methods are outlined along with common functionalization approaches using polymers, biomolecules, nanomaterials, and synthetic chemistry to facilitate the immobilization of recognition elements and improve performance. Major sensor configurations including graphene field-effect transistors, graphene modified electrodes and nanocomposites, and 3D graphene networks are highlighted along with their principles of operation, advantages, and biosensing capabilities. Strategies for the immobilization of biorecognition elements like antibodies, aptamers, peptides, and DNA/RNA probes onto graphene platforms to impart target specificity are summarized. The use of nanomaterial labels, hybrid nanocomposites with graphene, and chemical modification for signal enhancement are also discussed. Examples are provided to illustrate applications for the sensitive electrochemical detection of a broad range of cancer biomarkers including proteins, circulating tumor cells, DNA mutations, non-coding RNAs like miRNA, metabolites, and glycoproteins. Current challenges and future opportunities are elucidated to guide ongoing efforts towards transitioning graphene biosensors from promising research lab tools into mainstream clinical practice. Continued research addressing issues with reproducibility, stability, selectivity, integration, clinical validation, and regulatory approval could enable wider adoption. Overall, graphene electrochemical biosensors present powerful and versatile platforms for cancer diagnosis at the point of care.

Synthesis and Functionalization of Graphene Materials for Biomedical Applications: Recent Advances, Challenges, and Perspectives

Since its discovery in 2004, graphene is increasingly applied in various fields owing to its unique properties. Graphene application in the biomedical domain is promising and intriguing as an emerging 2D material with a high surface area, good mechanical properties, and unrivalled electronic and physical properties. This review summarizes six typical synthesis methods to fabricate pristine graphene (p-G), graphene oxide (GO), and reduced graphene oxide (rGO), followed by characterization techniques to examine the obtained graphene materials. As bare graphene is generally undesirable in vivo and in vitro, functionalization methods to reduce toxicity, increase biocompatibility, and provide more functionalities are demonstrated. Subsequently, in vivo and in vitro behaviors of various bare and functionalized graphene materials are discussed to evaluate the functionalization effects. Reasonable control of dose (<20 mg kg^-1 ), sizes (50-1000 nm), and functionalization methods for in vivo application are advantageous. Then, the key biomedical applications based on graphene materials are discussed, coupled with the current challenges and outlooks of this growing field. In a broader sense, this review provides a comprehensive discussion on the synthesis, characterization, functionalization, evaluation, and application of p-G, GO, and rGO in the biomedical field, highlighting their recent advances and potential.

Hierarchy of hybrid materials. Part-II: The place of organics-on-inorganics in it, their composition and applications

Hybrid materials or hybrids incorporating organic and inorganic constituents are emerging as a very potent and promising class of materials due to the diverse but complementary nature of their properties. This complementarity leads to a perfect synergy of properties of the desired materials and products as well as to an extensive range of their application areas. Recently, we have overviewed and classified hybrid materials describing inorganics-in-organics in Part-I (Saveleva, et al., Front. Chem., 2019, 7, 179). Here, we extend that work in Part-II describing organics-on-inorganics, i.e., inorganic materials modified by organic moieties, their structure and functionalities. Inorganic constituents comprise of colloids/nanoparticles and flat surfaces/matrices comprise of metallic (noble metal, metal oxide, metal-organic framework, magnetic nanoparticles, alloy) and non-metallic (minerals, clays, carbons, and ceramics) materials; while organic additives can include molecules (polymers, fluorescence dyes, surfactants), biomolecules (proteins, carbohydtrates, antibodies and nucleic acids) and even higher-level organisms such as cells, bacteria, and microorganisms. Similarly to what was described in Part-I, we look at similar and dissimilar properties of organic-inorganic materials summarizing those bringing complementarity and composition. A broad range of applications of these hybrid materials is also presented whose development is spurred by engaging different scientific research communities.

Nanotechnology‐based electrochemical biosensors for monitoring breast cancer biomarkers

Breast cancer is categorized as the most widespread cancer type among women globally. On-time diagnosis can decrease the mortality rate by making the right decision in the therapy procedure. These features lead to a reduction in medication time and socioeconomic burden. The current review article provides a comprehensive assessment for breast cancer diagnosis using nanomaterials and related technologies. Growing use of the nano/biotechnology domain in terms of electrochemical nanobiosensor designing was discussed in detail. In this regard, recent advances in nanomaterial applied for amplified biosensing methodologies were assessed for breast cancer diagnosis by focusing on the advantages and disadvantages of these approaches. We also monitored designing methods, advantages, and the necessity of suitable (nano) materials from a statistical standpoint. The main objective of this review is to classify the applicable biosensors based on breast cancer biomarkers. With numerous nano-sized platforms published for breast cancer diagnosis, this review tried to collect the most suitable methodologies for detecting biomarkers and certain breast cancer cell types.

Hybrid Nanobioengineered Nanomaterial-Based Electrochemical Biosensors

Nanoengineering biosensors have become more precise and sophisticated, raising the demand for highly sensitive architectures to monitor target analytes at extremely low concentrations often required, for example, for biomedical applications. We review recent advances in functional nanomaterials, mainly based on novel organic-inorganic hybrids with enhanced electro-physicochemical properties toward fulfilling this need. In this context, this review classifies some recently engineered organic-inorganic metallic-, silicon-, carbonaceous-, and polymeric-nanomaterials and describes their structural properties and features when incorporated into biosensing systems. It further shows the latest advances in ultrasensitive electrochemical biosensors engineered from such innovative nanomaterials highlighting their advantages concerning the concomitant constituents acting alone, fulfilling the gap from other reviews in the literature. Finally, it mentioned the limitations and opportunities of hybrid nanomaterials from the point of view of current nanotechnology and future considerations for advancing their use in enhanced electrochemical platforms.

Nano-bio interfaces effect of two-dimensional nanomaterials and their applications in cancer immunotherapy

The field of two-dimensional (2D) nanomaterial-based cancer immunotherapy combines research from multiple subdisciplines of material science, nano-chemistry, in particular nano-biological interactions, immunology, and medicinal chemistry. Most importantly, the "biological identity" of nanomaterials governed by bio-molecular corona in terms of bimolecular types, relative abundance, and conformation at the nanomaterial surface is now believed to influence blood circulation time, bio-distribution, immune response, cellular uptake, and intracellular trafficking. A better understanding of nano-bio interactions can improve utilization of 2D nano-architectures for cancer immunotherapy and immunotheranostics, allowing them to be adapted or modified to treat other immune dysregulation syndromes including autoimmune diseases or inflammation, infection, tissue regeneration, and transplantation. The manuscript reviews the biological interactions and immunotherapeutic applications of 2D nanomaterials, including understanding their interactions with biological molecules of the immune system, summarizes and prospects the applications of 2D nanomaterials in cancer immunotherapy.

A novel label-free electrochemical immunesensor for ultrasensitive detection of LT toxin using prussian blue@gold nanoparticles composite as a signal amplification

In the current study, a novel electrochemical label-free immunosensor is proposed for sensitive detection of heat-labile enterotoxin (LT) from Escherichia coli. Firstly, a glassy carbon electrode (GCE) was modified by a mixture containing reduced graphene oxide/room temperature ionic liquid (rGO/RTIL) composite. Then, simultaneous electrodeposition of prussian blue and gold nanoparticles led to formation of prussian blue@gold nanoparticles (PB@GNPs) composite on the electrode surface. The modified electrode was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. After immobilization of anti-LT and blocking the unreacted sites with BSA (bovine serum albumin), the analytical performance of the proposed immunosensor was evaluated under optimal conditions (i.e. optimal pH, incubation time and temperature of incubation). Square wave voltammetry (SWV) was used to determine different concentrations of the LT antigen. The linear dynamic range of the proposed immunosensor was from 0.01 to 50 µg/mL and the detection limit of the immunosensor was found to be 0.0023 µg/mL. An acceptable selectivity in the real sample, long-term stability and goodreproducibility made the fabricated immunosensor a good candidate for detecting LT.

Performance of the Polydopamine-Graphene Oxide Composite Substrate in the Osteogenic Differentiation of Mouse Embryonic Stem Cells

Graphene oxide (GO) is a biocompatible material considered a favorable stem cell culture substrate. In this study, GO was modified with polydopamine (PDA) to facilitate depositing GO onto a tissue culture polystyrene (PT) surface, and the osteogenic performance of the PDA/GO composite in pluripotent embryonic stem cells (ESCs) was investigated. The surface chemistry of the PDA/GO-coated PT surface was analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). A high cell viability of ESCs cultured on the PDA/GO composite-coated surface was initially ensured. Then, the osteogenic differentiation of the ESCs in response to the PDA/GO substrate was assessed by alkaline phosphatase (ALP) activity, intracellular calcium levels, matrix mineralization assay, and evaluation of the mRNA and protein levels of osteogenic factors. The culture of ESCs on the PDA/GO substrate presented higher osteogenic potency than that on the uncoated control surface. ESCs cultured on the PDA/GO substrate expressed significantly higher levels of integrin α5 and β1, as well as bone morphogenetic protein receptor (BMPR) types I and II, compared with the control groups. The phosphorylation of extracellular signal-regulated kinase (ERK)1/2, p38, and c-Jun-N-terminal kinase (JNK) mitogen-activated protein kinases (MAPKs) was observed in ESCs culture on the PDA/GO substrate. Moreover, BMP signal transduction by SMAD1/5/8 phosphorylation was increased more in cells on PDA/GO than in the control. The nuclear translocation of SMAD1/5/8 in cells was also processed in response to the PDA/GO substrate. Blocking activation of the integrin α5/β1, MAPK, or SMAD signaling pathways downregulated the PDA/GO-induced osteogenic differentiation of ESCs. These results suggest that the PDA/GO composite stimulates the osteogenic differentiation of ESCs via the integrin α5/β1, MAPK, and BMPR/SMAD signaling pathways.

Mesoporous Materials-Based Electrochemical Biosensors from Enzymatic to Nonenzymatic

Mesoporous materials have drawn more and more attention in the field of biosensors due to their high surface areas, large pore volumes, tunable pore sizes, as well as abundant frameworks. In this review, the progress on mesoporous materials-based biosensors from enzymatic to nonenzymatic are highlighted. First, recent advances on the application of mesoporous materials as supports to stabilize enzymes in enzymatic biosensing technology are summarized. Special emphasis is placed on the effect of pore size, pore structure, and surface functional groups of the support on the immobilization efficiency of enzymes and the biosensing performance. Then, the development of a nonenzymatic strategy that uses the intrinsic property of mesoporous materials (carbon, silica, metals, and composites) to mimic the behavior of enzymes for electrochemical sensing of some biomolecules is discussed. Finally, the challenges and perspective on the future development of biosensors based on mesoporous materials are proposed.

New Insights into Layered Graphene Materials as Substrates to Regulate Synthesis of Ni-P Nanomaterials for Electrocatalytic Oxidation of Methanol and Water

The doping ring-core nickel phosphide/graphene nanomaterial is obtained by H₂ reduction of the flower-like nickel phosphates/graphene oxide (NiPOGO) and sea urchin-like nickel phosphates/chemically converted graphene (NiPOG) substrates. The obtained structure of nickel phosphates depends on the influence of different kinds of oxygen-containing groups on the graphene substrate. The substrate can also affect the particle size and distribution of nickel phosphate nanoparticles. The substrate can adjust the particle size, distribution, and exposed growth direction of nickel phosphide. These materials with high activity are employed as electrochemical catalysts for methanol oxidation reactions, which is ∼7 times that of pure nickel phosphide, and there is a very small Tafel slope of 47 mV decade^-1 in the water oxidation reaction. Our results highlight that the substrate structure is essential to catalytic materials for electrochemical oxidation of methanol and water.

Nanosilica: Recent Progress in Synthesis, Functionalization, Biocompatibility, and Biomedical Applications

Silica nanoparticles (Si-NPs) are widely explored in biomedical applications due to their high surface area, excellent biocompatibility, and tunable pore size. The silica surface can be readily functionalized for wide range of applications such as cellular imaging, biosensing, and targeted drug delivery. This comprehensive review discusses different synthesis methodologies of Si-NPs and their surface functionalization with various functional groups. Nanosilica functionalization methods are discussed in detail, emphasizing their suitability for targeted drug delivery, cancer therapy, bioimaging, and biosensing. The toxicity assessment of nanosilica is also critically reviewed to get a clear focus before employing them for nanomedicine.

Voltammetric sandwich immunoassay for Cronobacter sakazakii using a screen-printed carbon electrode modified with horseradish peroxidase, reduced graphene oxide, thionine and gold nanoparticles

The authors describe a sandwich-type of electrochemical immunoassay for rapid determination of the foodborne pathogen Cronobacter sakazakii (C. sakazakii). Polyclonal antibody against C. sakazakii (anti-C. sakazakii) and horseradish peroxidase were immobilized on a nanocomposite consisting of reduced graphene oxide, thionine and gold nanoparticles (AuNPs) that was placed on a screen-printed carbon electrode (SPCE). Thionine acts as an electron mediator which also shortens the electron transfer pathway from the conjugated HRP to the electrode surface and amplifies the electrochemical signal. The AuNPs, in turn, improve the electron transfer rate and increase the surface area for capturing antibody. The morphologies of the electrodes were characterized by means of field emission scanning electron microscopy. The electrochemical performance of the immunoassay was evaluated by cyclic voltammetry and differential pulse voltammetry. Under optimal experimental conditions, the electrochemical immunoassay, best operated at a woking potential of -0.18 V (vs. Ag/AgCl) and scan rate of 20 mV/s has a linear response that covers the 8.8 × 10⁴ to 8.8 × 10⁸ CFU·mL^-1 C. sakazakii concentration range, with a 1.0 × 10⁴ CFU·mL^-1 detection limit (at an S/N ratio of 3). The assay was applied to the detemination of C. sakazakii in spiked infant milk powder and gave recoveries ranging from 92.0 to 105.7%. Graphical abstract A sandwich-type electrochemical immunosensor was designed for C. sakazakii based on the use of rGO. TH, HRP, antibody and AuNPs were anchored on rGO. The nanocomposites were used as traces tag and H₂O₂ as enzyme substrates. AuNPs were modified on SPCE by electrodeposition.

Novel synthetic routes of large-pore magnetic mesoporous nanocomposites (SBA-15/Fe3O4) as potential multifunctional theranostic nanodevices

In this paper, novel magnetic silica nanocomposites were prepared by anchoring magnetite nanoparticles onto the outer surface of mesoporous SBA-15 silica; the magnetic nanoparticles were prepared by microemulsion and solvothermal methods, varying the synthesis conditions in order to control the final physicochemical, textural and magnetic properties. The morphology and mesostructure of the materials were characterized by X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), N₂ adsorption-desorption, and Transmission and Scanning Electron Microscopy (TEM and SEM). Magnetic silica nanocomposites feature a two-dimensional hexagonal arrangement constituted by a homogeneous pore channel system with diameters between 13 and 18 nm and a Brunauer-Emmett-Teller (BET) surface area higher than 260 m² g^-1. The different morphologies of the samples are given by the presence of diverse magnetic nanoparticle arrangements covalently linked onto the outer surface of the mesoporous silica rods. This confers on them a superparamagnetic behaviour with a magnetic response between 50-80 emu g^-1, even though the weight percent of magnetite present in the samples does not exceed 21.7%. In addition, the magnetic nanocomposites exhibit magnetic hyperthermia with moderate Specific Absorption Rate (SAR) values.

Albumin (BSA) adsorption onto graphite stepped surfaces

Nanomaterials are good candidates for the design of novel components with biomedical applications. For example, nano-patterned substrates may be used to immobilize protein molecules in order to integrate them in biosensing units. Here, we perform long MD simulations (up to 200 ns) using an explicit solvent and physiological ion concentrations to characterize the adsorption of bovine serum albumin (BSA) onto a nano-patterned graphite substrate. We have studied the effect of the orientation and step size on the protein adsorption and final conformation. Our results show that the protein is stable, with small changes in the protein secondary structure that are confined to the contact area and reveal the influence of nano-structuring on the spontaneous adsorption, protein-surface binding energies, and protein mobility. Although van der Waals (vdW) interactions play a dominant role, our simulations reveal the important role played by the hydrophobic lipid-binding sites of the BSA molecule in the adsorption process. The complex structure of these sites, that incorporate residues with different hydrophobic character, and their flexibility are crucial to understand the influence of the ion concentration and protein orientation in the different steps of the adsorption process. Our study provides useful information for the molecular engineering of components that require the immobilization of biomolecules and the preservation of their biological activity.

Nanomaterials for Electrochemical Immunosensing

Electrochemical immunosensors resulting from a combination of the traditional immunoassay approach with modern biosensors and electrochemical analysis constitute a current research hotspot. They exhibit both the high selectivity characteristics of immunoassays and the high sensitivity of electrochemical analysis, along with other merits such as small volume, convenience, low cost, simple preparation, and real-time on-line detection, and have been widely used in the fields of environmental monitoring, medical clinical trials and food analysis. Notably, the rapid development of nanotechnology and the wide application of nanomaterials have provided new opportunities for the development of high-performance electrochemical immunosensors. Various nanomaterials with different properties can effectively solve issues such as the immobilization of biological recognition molecules, enrichment and concentration of trace analytes, and signal detection and amplification to further enhance the stability and sensitivity of the electrochemical immunoassay procedure. This review introduces the working principles and development of electrochemical immunosensors based on different signals, along with new achievements and progress related to electrochemical immunosensors in various fields. The importance of various types of nanomaterials for improving the performance of electrochemical immunosensor is also reviewed to provide a theoretical basis and guidance for the further development and application of nanomaterials in electrochemical immunosensors.

A sensitive non-enzymatic immunosensor composed of silver nanoflowers for squamous cell carcinoma antigen

In this work, a sensitive sandwich-type non-enzymatic electrochemical immunosensor for quantitative detection of squamous cell carcinoma antigen (SCCA) is designed and fabricated.

Redox active molybdophosphate produced by Cu3(PO4)2nanospheres for enhancing enzyme-free electrochemical immunoassay of C-reactive protein

Redox-active molybdophosphate produced by Cu₃(PO₄)₂nanospheres has been directly employed for signal amplification of an enzyme-free electrochemical immunosensor.

A sub-picomolar assay for protein by using cubic Cu2O nanocages loaded with Au nanoparticles as robust redox probes and efficient non-enzymatic electrocatalysts

In this work, a simple and sensitive electrochemical aptasensor for protein (thrombin – TB used as the model) was developed by using cubic Cu₂O nanocages (Cu₂O-NCs) loaded with Au nanoparticles (AuNPs@Cu₂O-NCs) as non-enzymatic electrocatalysts and robust redox probes.

Printed organo-functionalized graphene for biosensing applications

Graphene is a highly promising material for biosensors due to its excellent physical and chemical properties which facilitate electron transfer between the active locales of enzymes or other biomaterials and a transducer surface. Printing technology has recently emerged as a low-cost and practical method for fabrication of flexible and disposable electronics devices. The combination of these technologies is promising for the production and commercialization of low cost sensors. In this review, recent developments in organo-functionalized graphene and printed biosensor technologies are comprehensively covered. Firstly, various methods for printing graphene-based fluids on different substrates are discussed. Secondly, different graphene-based ink materials and preparation methods are described. Lastly, biosensing performances of printed or printable graphene-based electrochemical and field effect transistor sensors for some important analytes are elaborated. The reported printed graphene based sensors exhibit promising properties with good reliability suitable for commercial applications. Among most reports, only a few printed graphene-based biosensors including screen-printed oxidase-functionalized graphene biosensor have been demonstrated. The technology is still at early stage but rapidly growing and will earn great attention in the near future due to increasing demand of low-cost and disposable biosensors.

Bioinspired Synthesis of All-in-One Organic-Inorganic Hybrid Nanoflowers Combined with a Handheld pH Meter for On-Site Detection of Food Pathogen

With a mild elaborately bioinspired one-pot process, Con A-GOx-CaHPO4 nanoflowers are prepared. Employing the as-prepared all-in-one hybrid nanoflowers as signal tags, a simple but potentially powerful amplification biosensing technology for the detection of food pathogen with excellent simplicity, portability, sensitivity, and adaptability is achieved.

An ultrasensitive sandwich-type electrochemical immunosensor based on functionalized mesoporous carbon for IgG detection

Immunoglobulin (IgG) plays an important role in the accurate diagnosis of some diseases.

Cubic Cu2O nanoframes with a unique edge-truncated structure and a good electrocatalytic activity for immunosensor application

In this work, an ultrasensitive sandwich-type electrochemical immunosensor was developed for the quantitative detection of prostate specific antigen (PSA). Gold nanoparticles decorated 3-aminopropyltriethoxysilane functionalized graphene sheets (Au@APTES-GS) with a large specific surface area, good biocompatibility and superior electron transfer ability were employed as the matrix. In addition, cubic Cu2O nanoframes with hollow edges were employed as the label for the first time. Scanning electron microscope (SEM) images were used to confirm the nanostructure of Au@APTES-GS and Cu2O. Using square wave voltammetry (SWV) to monitor the electrocatalytic process, the signal amplification mechanism of the matrix and the label were explored successfully. Here we find that the unique edge-truncated structure of Cu2O nanoframes can load with a larger amount of redox mediators, ferrocenecarboxylic acid (Fc-COOH), offering a higher electrochemical signal response. Apart from that, Cu2O nanoframes have a good electrocatalytic activity towards the Fc-COOH and hydrogen peroxide (H2O2), making a contribution to further enhance the sensitivity of the fabricated immunosensor. Under optimal conditions, the proposed immunosensor achieved an ultrasensitive and specific detection of PSA, and displayed acceptable reproducibility, selectivity and stability. This work may provide an effective method for the clinical monitoring of tumor markers and demonstrate the potential application promising of nanoframes in the fabrication of immunosensors.

Cu-Based Metal-Organic Frameworks as a Catalyst To Construct a Ratiometric Electrochemical Aptasensor for Sensitive Lipopolysaccharide Detection

In this work, we developed a sensitive and efficient ratiometric electrochemical method for lipopolysaccharide (LPS) detection using Cu-based metal-organic frameworks (Cu-MOFs) as a catalyst and target-triggered quadratic cycles for signal amplification. First, in the presence of target LPS, the conformation change of the specifically designed hairpin probes 1 (HP1) triggered the target cyclic-induced polymerization to produce the output DNA with the aid of phi29 DNA polymerase (phi29). Then, the obtained output DNA hybridized with ferrocene-labeled hairpin probes 2 (Fc-HP2, which were immobilized on the electrode) to generate a nicking endonuclease (N.BstNBI) cleavage site. Thus, with N.BstNBI, the original signal molecules of Fc left from the electrode, and the single-stranded capture-probe-modified sensing interface was obtained. At this time, signal probes conducted by Au-nanoparticles-functionalized Cu-MOFs and labeled hairpin probes 3 (HP3/AuNPs/Cu-MOFs) were hybridized with capture probes for hairpin assembly. Herein, AuNPs/Cu-MOFs were not only used as nanocarriers for immobilizing HP3 but also acted as electroactive materials for signal reporting. With the proposed target-triggered quadratic cycles, the cleavage sites of Fc-HP2 were cut, and capture probes were obtained to hybridize with HP3/AuNPs/Cu-MOFs, which caused the signal decrease of Fc. Then Cu-MOFs were closed to the electrode for the signal increase of Cu-MOFs. Furthermore, when glucose was present in the detection solution, AuNPs/Cu-MOFs catalyzed the oxidation of glucose to realize the enzyme-free signal amplification. By measuring the peak currents ratio of the Cu-MOFs and Fc, the proposed aptasenor for LPS detection showed a low detection limit (0.33 fg/mL) and a wide linear range from 1.0 fg/mL to 100 ng/mL with high accuracy and sensitivity. This ratiometric electrochemical approach is expected to be a valuable strategy for detection of other analytes.

Graphene as a signal amplifier for preparation of ultrasensitive electrochemical biosensors

Early diagnostics of diseases performed with minimal money and time consumption has become achievable due to recent advances in development of biosensors. These devices use biorecognition elements for selective interaction with an analyte and signal readout is obtained via different types of transducers. Operational characteristics of biosensors have been reported to improve substantially, when a diverse range of nanomaterials was employed. This review presents construction of electrochemical biosensors based on graphene, atomically thin 2D carbon crystals, which is currently intensively studied nanomaterial. The most attractive directions of graphene applications in biosensor preparation are discussed here including novel detection and amplification schemes exploiting graphene's unique electrochemical, physical and chemical properties. The future of graphene-based biosensors is most likely bright, but there is still a lot of work to do to fulfill high expectations.