A novel label-free amperometric immunosensor for carcinoembryonic antigen based on Ag nanoparticle decorated infinite coordination polymer fibres

Selective Detection of Alkaline Phosphatase Activity in Environmental Water Samples by Copper Nanoclusters Doped Lanthanide Coordination Polymer Nanocomposites as the Ratiometric Fluorescent Probe

In this paper, a novel, accurate, sensitive and rapid ratiometric fluorescent sensor was fabricated using a copper nanoclusters@infinite coordination polymer (ICP), specifically, terbium ion-guanosine 5'-disodium (Cu NCs@Tb-GMP) nanocomposites as the ratiometric fluorescent probe, to detect alkaline phosphatase (ALP) in water. The fluorescence probe was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The experimental results showed that, compared with Tb-GMP fluorescent sensors, Cu ratiometric fluorescent sensors based on NCs encapsulated in Tb-GMP had fewer experimental errors and fewer false-positive signals and were more conducive to the sensitive and accurate detection of ALP. In addition, the developed fluorescent probe had good fluorescence intensity, selectivity, repeatability and stability. Under optimized conditions, the ratiometric fluorescent sensor detected ALP in the range of 0.002-2 U mL^-1 (R² = 0.9950) with a limit of detection of 0.002 U mL^-1, and the recovery of ALP from water samples was less than 108.2%. These satisfying results proved that the ratiometric fluorescent probe has good application prospects and provides a new method for the detection of ALP in real water samples.

Current and Prospective of Breast Cancer Biomarkers

Biomarkers have shown great promise over the past decade the process of drug development more effective and have become an integral part of diagnosis of diseases. Biosensors were integrated with biomarker detection and point-of-care detection for signal amplification, high specificity and sensitivity, rapid response time, low cost, simplicity and multi-analytical testing. In order to detect more sensitively, these particular biomarkers have been explored with the possibility of real-time measurements in order to develop simple and compact systems which can analyze complex specimens. Various biosensors including electrochemical biosensors have recently been developed based on disease-specific biomarkers in the diagnosis of cancer disease. The main objective of the book chapter is to review research with new materials/methods in electrochemical biosensing techniques to detection of breast cancer biomarkers and evaluating latest techniques for detection of important analytes in real samples. In this book chapter, the recent development of electrochemical biosensors of breast cancer biomarkers will be reviewed. Furthermore, recent and future trend application of breast cancer biomarkers will be discussed.

Construction of electrochemical immunosensors based on redox hydrogels for ultrasensitive detection of carcinoembryonic antigens

The introduction of cellulose nanocrystals (CNCs) endows a redox hydrogel with a larger specific surface area and better adhesion to an electrode.

An ultrasensitive immunosensor based on manganese dioxide-graphene nanoplatelets and core shell Fe3O4@Au nanoparticles for label-free detection of carcinoembryonic antigen

A novel electrochemical immunosensor was developed for label-free detection of carcinoembryonic antigen (CEA) as a cancer biomarker. The designed immunosensor was based on CEA antibody (anti-CEA) anchored with core shell Fe₃O₄@Au nanoparticles which were immobilized on a screen-printed carbon electrode modified with manganese dioxide decorating on graphene nanoplatelets (SPCE/GNP-MnO₂/Fe₃O₄@Au-antiCEA). The SPCE was placed onto a home-made electrode holder for easy handling. The approach was based on direct binding of CEA to a fixed amount of anti-CEA on the modified electrode for the specific detection using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) monitored in a solution containing 5 mM [Fe(CN)₆^3-/4-] prepared in 0.1 M phosphate buffer at pH 7.4. The difference in signal response owing to the redox reaction of [Fe(CN)₆]^3-/4- before and after interaction with CEA was regarded as the immunosensor response corresponding directly to the CEA concentration. Under optimized conditions, the linear range of 0.001-100 ng/mL, and the detection limits of 0.10 pg/mL (LSV) and 0.30 pg/mL (EIS) were evaluated. The applicability of the immunosensor was verified by well-corresponding determination of CEA in diluted human serum samples by electrochemiluminescence (ECL) immunoassay. Therefore, the proposed immunosensor could be suitable enough for a real sample analysis of CEA.

Electrochemical biosensors for the detection of lung cancer biomarkers: A review

Cancer is one of the most widespread challenges and important diseases, which has the highest mortality rate. Lung cancer is the most common type of cancer, so that about 25% of all cancer deaths are related to the lung cancer. The lung cancer is classified as two different types with different treatment methodology: the small cell lung carcinoma and nonsmall cell lung carcinoma are two categories of the lung cancer. Since the lung cancer is often in the latent period in its early stages, therefore, early diagnosis of lung cancer has many challenges. Hence, there is a need for sensitive and reliable tools for preclinical diagnosis of lung cancer. Therefore, many detection methods have been employed for early detection of lung cancer. As lung cancer tumors growth in the body, the cancerous cells release numerous DNA, proteins, and metabolites as special biomarkers of the lung cancer. The levels of these biomarkers show the stages of the lung cancer. Therefore, detection of the biomarkers can be used for screening and clinical diagnosis of the lung cancer. There are numerous biomarkers for the lung cancer such as EGFR, CEA, CYFRA 21-1, ENO1, NSE, CA 19-9, CA 125 and VEGF. Nowadays, electrochemical methods are very attractive and useful in the lung cancer detections. So, in this paper, the recent advances and improvements (2010-2018) in the electrochemical detection of the lung cancer biomarkers have been reviewed.

A novel label-free electrochemical immunosensor based on the enhanced catalytic currents of oxygen reduction by AuAg hollow nanocrystals for detecting carbohydrate antigen 199

Herein, bimetallic alloyed AuAg hollow nanocrystals (AuAg HNCs) were prepared by a simple one-pot aqueous method using polycytidysic acid (PCA) as the green growth-directing agent. The novel immunosensor for carbohydrate antigen 199 (CA199) was further constructed based on the enhanced catalytic currents of oxygen reduction reaction (ORR) by AuAg HNCs. By virtue of the good biocompatibility and catalytic activity of AuAg HNCs, the immunosensor exhibited superior analytical performance for the assay of CA199 under the optimal experimental conditions, the ORR signals linearly decreased with the increased CA199 concentrations in the range of 1 ~ 30UmL^-1, with the low detection limit of 0.228UmL^-1, improved stability, reproducibility and selectivity.

Recent Advances in Electrochemical Immunosensors

Immunosensors have experienced a very significant growth in recent years, driven by the need for fast, sensitive, portable and easy-to-use devices to detect biomarkers for clinical diagnosis or to monitor organic pollutants in natural or industrial environments. Advances in the field of signal amplification using enzymatic reactions, nanomaterials such as carbon nanotubes, graphene and graphene derivatives, metallic nanoparticles (gold, silver, various oxides or metal complexes), or magnetic beads show how it is possible to improve collection, binding or transduction performances and reach the requirements for realistic clinical diagnostic or environmental control. This review presents these most recent advances; it focuses first on classical electrode substrates, then moves to carbon-based nanostructured ones including carbon nanotubes, graphene and other carbon materials, metal or metal-oxide nanoparticles, magnetic nanoparticles, dendrimers and, to finish, explore the use of ionic liquids. Analytical performances are systematically covered and compared, depending on the detection principle, but also from a chronological perspective, from 2012 to 2016 and early 2017.

Ultrasensitive Label-free Electrochemical Immunosensor based on Multifunctionalized Graphene Nanocomposites for the Detection of Alpha Fetoprotein

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of alpha fetoprotein (AFP). Multifunctionalized graphene nanocomposites (TB-Au-Fe₃O₄-rGO) were applied to modify the electrode to achieve the amplification of electrochemical signal. TB-Au-Fe₃O₄-rGO includes the advantages of graphene, ferroferric oxide nanoparticles (Fe₃O₄ NPs), gold nanoparticles (Au NPs) and toluidine blue (TB). As a kind of redox probe, TB can produce the electrochemical signal. Graphene owns large specific surface area, high electrical conductivity and good adsorption property to load a large number of TB. Fe₃O₄ NPs have good electrocatalytic performance towards the redox of TB. Au NPs have good biocompatibility to capture the antibodies. Due to the good electrochemical performance of TB-Au-Fe₃O₄-rGO, the effective and sensitive detection of AFP was achieved by the designed electrochemical immunosensor. Under optimal conditions, the designed immunosensor exhibited a wide linear range from 1.0 × 10⁻⁵ ng/mL to 10.0 ng/mL with a low detection limit of 2.7 fg/mL for AFP. It also displayed good electrochemical performance including good reproducibility, selectivity and stability, which would provide potential applications in the clinical diagnosis of other tumor markers.

Recent advances in biosensor development for the detection of cancer biomarkers

Cancer is the second largest disease throughout the world with an increasing mortality rate over the past few years. The patient's survival rate is uncertain due to the limitations of cancer diagnosis and therapy. Early diagnosis of cancer is decisive for its successful treatment. A biomarker-based cancer diagnosis may significantly improve the early diagnosis and subsequent treatment. Biosensors play a crucial role in the detection of biomarkers as they are easy to use, portable, and can do analysis in real time. This review describes various biosensors designed for detecting nucleic acid and protein-based cancer biomarkers for cancer diagnosis. It mainly lays emphasis on different approaches to use electrochemical, optical, and mass-based transduction systems in cancer biomarker detection. It also highlights the analytical performances of various biosensor designs concerning cancer biomarkers in detail.

An ultrasensitive label-free electrochemical immunosensor based on signal amplification strategy of multifunctional magnetic graphene loaded with cadmium ions

Herein, a novel and ultrasensitive label-free electrochemical immunosensor was proposed for quantitative detection of human Immunoglobulin G (IgG). The amino functionalized magnetic graphenes nanocomposites (NH₂-GS-Fe₃O₄) were prepared to bond gold and silver core-shell nanoparticles (Au@Ag NPs) by constructing stable Au-N and Ag-N bond between Au@Ag NPs and -NH₂. Subsequently, the Au@Ag/GS-Fe₃O₄ was applied to absorb cadmium ion (Cd²⁺) due to the large surface area, high conductivity and exceptional adsorption capability. The functional nanocomposites of gold and silver core-shell magnetic graphene loaded with cadmium ion (Au@Ag/GS-Fe₃O₄/Cd²⁺) can not only increase the electrocatalytic activity towards hydrogen peroxide (H₂O₂) but also improve the effective immobilization of antibodies because of synergistic effect presented in Au@Ag/GS-Fe₃O₄/Cd²⁺, which greatly extended the scope of detection. Under the optimal conditions, the proposed immunosensor was used for the detection of IgG with good linear relation in the range from 5 fg/mL to 50 ng/mL with a low detection limit of 2 fg/mL (S/N = 3). Furthermore, the proposed immunosensor showed high sensitivity, special selectivity and long-term stability, which had promising application in bioassay analysis.

A porous CuO nanowire-based signal amplification immunosensor for the detection of carcinoembryonic antigens

A novel electrochemical immunosensor was developed for the detection of CEA based on CNTs–AuNPs as a platform and pCuOw@Fc as labels. The immunosensor showed enhanced electrochemical performance toward the detection of CEA.

Graphene oxide supported rhombic dodecahedral Cu2O nanocrystals for the detection of carcinoembryonic antigen

In this work, a simple electrochemical immunosensor was developed for the detection of carcinoembryonic antigen (CEA) based on rhombic dodecahedral Cu2O nanocrystals-graphene oxide-gold nanoparticles (rCu2O-GO-AuNPs). GO as the template and surfactant resulting in rCu2O exhibit improved rhombic dodecahedral structure uniformity and excellent electrochemical performance. Moreover, GO was found to be able to effectively improve the long stability of rCu2O on the electrode response. Under optimal conditions, the immunosensor showed a low limit of detection (0.004 ng ml(-1)) and a large linear range (0.01-120 ng ml(-1)). This work presents a potential alternative for the diagnostic applications of GO-supported special morphology materials in biomedicine and biosensors.

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.

A sandwich-type electrochemical immunosensor for carcinoembryonic antigen based on signal amplification strategy of optimized ferrocene functionalized Fe₃O₄@SiO₂ as labels

A sandwich-type electrochemical immunosensor was developed for sensitive detection of carcinoembryonic antigen (CEA) by using ferroferric oxide@silica-amino groups (Fe3O4@SiO2-NH2) as carriers and gold nanoparticles-graphene oxide (GO-AuNPs) as platform. The Fe3O4@SiO2-NH2 surface was used as linked reagents for co-immobilization of ferrocenecarboxylic acid (Fc-COOH) and secondary anti-CEA (Ab2) to prepare the signal probe, and it also could hasten the decomposition of hydrogen peroxide (H2O2) to amplify signals. Differential pulse voltammetry (DPV) was successfully used to quantify CEA. Under the optimized conditions, the designed immunosensor shows an excellent analytical performance wide dynamic response range of CEA concentration from 0.001 ng mL(-1) to 80 ng mL(-1) with a relatively low detection limit of 0.0002 ng mL(-1) (S/N=3), and high specificity and good reproducibility. The proposed immunosensor was successfully used to determine CEA in spiked human serum samples.

Unexpected in-situ Free Radical Generation and Catalysis to Ag/Polymer Nanocomposite

In this study, we discover unexpectedly that simple reaction of AgNO₃ with oleic acid (OA) without solvent and surfactant could generate alkyl free radical which can catalyze double-bond polymerization of OA to form 1D polymeric oleic acid (POA) chain. In certain conditions, these POA chains circumvolute tightly each other to form microspheres and micro-plates in which monodisperse 4-5 nm Ag nanoparticles (NPs) were absorbed. It has been revealed that alkyl free radical generated during the redox reaction of carboxyl group of OA with Ag⁺ at relative low temperature. Then, the alkyl free radical catalyzed the double-bond polymerization of OA when the reaction temperature was further increased. Different from commonly-seen hydrophobic nanoparticles prepared in oleic acid-based microemulsion system, the nanocomposites cannot dispersed in n-hexane and could dispersed in ethanol and THF. The unusual dispersion behavior has been explained in terms of their structure and polarity of POA chain. The method combines the nucleation of Ag nanoparticles and the polymerization of monomer in a facile one-pot reaction, which provides a novel way for metal-polymer microsphere nanocomposite with low-cost, easy-operation and high-yield.

Polymethacrylate coated electrospun PHB fibers: An exquisite outlook for fabrication of paper-based biosensors

Electrospun polyhydroxybutyrate (PHB) fibers were dip-coated by polymethyl methacrylate-co-methacrylic acid, poly(MMA-co-MAA), which was synthesized in different molar ratios of the monomers via free-radical polymerization. Fabricated platfrom was employed for immobilization of the dengue antibody and subsequent detection of dengue enveloped virus in enzyme-linked immunosorbent assay (ELISA). There is a major advantage for combination of electrospun fibers and copolymers. Fiber structre of electrospun PHB provides large specific surface area available for biomolecular interaction. In addition, polymer coated parts of the platform inherited the premanent presence of surface carboxyl (-COOH) groups from MAA segments of the copolymer which can be effectively used for covalent and physical protein immobilization. By tuning the concentration of MAA monomers in polymerization reaction the concentration of surface -COOH groups can be carefully controlled. Therefore two different techniques have been used for immobilization of the dengue antibody aimed for dengue detection: physical attachment of dengue antibodies to the surface and covalent immobilization of antibodies through carbodiimide chemistry. In that perspective, several different characterization techniques were employed to investigate the new polymeric fiber platform such as scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA) measurement and UV-vis titration. Regardless of the immobilization techniques, substantially higher signal intensity was recorded from developed platform in comparison to the conventional ELISA assay.

An ultrasensitive electrochemical immunosensor for CEA using MWCNT-NH2 supported PdPt nanocages as labels for signal amplification

An ultrasensitive sandwich-type immunosensor was proposed by using MWCNT-NH₂ supported PdPt nanocages as labels for signal amplification.

Layer-by-layer self-assembly of 2D graphene nanosheets, 3D copper oxide nanoflowers and 0D gold nanoparticles for ultrasensitive electrochemical detection of alpha fetoprotein

In this work, a novel and ultrasensitive label-free electrochemical immunosensor was developed for the quantitative detection of alpha fetoprotein (AFP).

Application of three-dimensional flower-like nanomaterials in the fabrication of sandwich-type electrochemical immunosensors

A novel and ultrasensitive sandwich-type electrochemical immunosensor was developed for the quantitative detection of carcinoembryonic antigen (CEA) in this work.

Current Trends in Nanomaterial-Based Amperometric Biosensors

The last decade has witnessed an intensive research effort in the field of electrochemical sensors, with a particular focus on the design of amperometric biosensors for diverse analytical applications. In this context, nanomaterial integration in the construction of amperometric biosensors may constitute one of the most exciting approaches. The attractive properties of nanomaterials have paved the way for the design of a wide variety of biosensors based on various electrochemical detection methods to enhance the analytical characteristics. However, most of these nanostructured materials are not explored in the design of amperometric biosensors. This review aims to provide insight into the diverse properties of nanomaterials that can be possibly explored in the construction of amperometric biosensors.