Electrochemical immunosensor for the carcinoembryonic antigen based on a nanocomposite consisting of reduced graphene oxide, gold nanoparticles and poly(indole-6-carboxylic acid)

Conducting polymer composite-based biosensing materials for the diagnosis of lung cancer: A review

The development of a simple and fast cancer detection method is crucial since early diagnosis is a key factor in increasing survival rates for lung cancer patients. Among several diagnosis methods, the electrochemical sensor is the most promising one due to its outstanding performance, portability, real-time analysis, robustness, amenability, and cost-effectiveness. Conducting polymer (CP) composites have been frequently used to fabricate a robust sensor device, owing to their excellent physical and electrochemical properties as well as biocompatibility with nontoxic effects on the biological system. This review brings up a brief overview of the importance of electrochemical biosensors for the early detection of lung cancer, with a detailed discussion on the design and development of CP composite materials for biosensor applications. The review covers the electrochemical sensing of numerous lung cancer markers employing composite electrodes based on the conducting polyterthiophene, poly(3,4-ethylenedioxythiophene), polyaniline, polypyrrole, molecularly imprinted polymers, and others. In addition, a hybrid of the electrochemical biosensors and other techniques was highlighted. The outlook was also briefly discussed for the development of CP composite-based electrochemical biosensors for POC diagnostic devices.

Formation of a Conducting Polymer by Different Electrochemical Techniques and Their Effect on Obtaining an Immunosensor for Immunoglobulin G

In this work, a conducting polymer (CP) was obtained through three electrochemical procedures to study its effect on the development of an electrochemical immunosensor for the detection of immunoglobulin G (IgG-Ag) by square wave voltammetry (SWV). The glassy carbon electrode modified with poly indol-6-carboxylic acid (6-PICA) applied the cyclic voltammetry technique presented a more homogeneous size distribution of nanowires with greater adherence allowing the direct immobilization of the antibodies (IgG-Ab) to detect the biomarker IgG-Ag. Additionally, 6-PICA presents the most stable and reproducible electrochemical response used as an analytical signal for developing a label-free electrochemical immunosensor. The different steps in obtaining the electrochemical immunosensor were characterized by FESEM, FTIR, cyclic voltammetry, electrochemical impedance spectroscopy, and SWV. Optimal conditions to improve performance, stability, and reproducibility in the immunosensing platform were achieved. The prepared immunosensor has a linear detection range of 2.0-16.0 ng·mL^-1 with a low detection limit of 0.8 ng·mL^-1. The immunosensing platform performance depends on the orientation of the IgG-Ab, favoring the formation of the immuno-complex with an affinity constant (Ka) of 4.32 × 10⁹ M^-1, which has great potential to be used as point of care testing (POCT) device for the rapid detection of biomarkers.

Electrochemical Micro-Immunosensor of Cubic AuPt Dendritic Nanocrystals/Ti3C2-MXenes for Exosomes Detection

Exosomes are extracellular vesicles that exist in body circulation as intercellular message transmitters. Although the potential of tumor-derived exosomes for non-invasive cancer diagnosis is promising, the rapid detection and effective capture of exosomes remains challenging. Herein, a portable electrochemical aptasensor of cubic AuPt dendritic nanocrystals (AuPt DNs)/Ti₃C₂ assisted in signal amplification, and aptamer CD63 modified graphene oxide (GO) was immobilized on a screen-printed carbon electrode (SPCE) as the substrate materials for the direct capture and detection of colorectal carcinoma exosomes. Cubic AuPt DNs/Ti₃C₂ was synthesized according to a simple hydrothermal procedure, and the AuPt DNs/Ti₃C₂-Apt hybrid demonstrated an efficient recognition of exosomes. Under optimal conditions, a detection limit of down to 20 exosomes µL^-1 was achieved with the linear range from 100 exosomes μL^-1 to 5.0 × 10⁵ exosomes μL^-1. The proposed immunosensor could be suitable for the analysis of exosomes and has clinical value in the early diagnosis of cancer.

Functional Ionic Liquids Decorated Carbon Hybrid Nanomaterials for the Electrochemical Biosensors

Ionic liquids are gaining high attention due to their extremely unique physiochemical properties and are being utilized in numerous applications in the field of electrochemistry and bio-nanotechnology. The excellent ionic conductivity and the wide electrochemical window open a new avenue in the construction of electrochemical devices. On the other hand, carbon nanomaterials, such as graphene (GR), graphene oxide (GO), carbon dots (CDs), and carbon nanotubes (CNTs), are highly utilized in electrochemical applications. Since they have a large surface area, high conductivity, stability, and functionality, they are promising in biosensor applications. Nevertheless, the combination of ionic liquids (ILs) and carbon nanomaterials (CNMs) results in the functional ILs-CNMs hybrid nanocomposites with considerably improved surface chemistry and electrochemical properties. Moreover, the high functionality and biocompatibility of ILs favor the high loading of biomolecules on the electrode surface. They extremely enhance the sensitivity of the biosensor that reaches the ability of ultra-low detection limit. This review aims to provide the studies of the synthesis, properties, and bonding of functional ILs-CNMs. Further, their electrochemical sensors and biosensor applications for the detection of numerous analytes are also discussed.

New Ultrasensitive Sandwich-Type Immunoassay of Dendritic Tri-Fan Blade-like PdAuCu Nanoparticles/Amine-Functionalized Graphene Oxide for Label-Free Detection of Carcinoembryonic Antigen

The early detection of tumor markers has an effective role in the treatment of cancer. Here, a new sandwich-type electrochemical immunosensor for early label-free detection of the cancer biomarker carcinoembryonic antigen (CEA) was developed. Dendritic tri-fan blade-like PdAuCu nanoparticles (PdAuCu NPs)/amine functionalized graphene oxide (NH₂-GO) were the label of secondary antibodies (Ab₂), and Au nanoparticle-decorated polydopamines (Au/PDA) were immobilized on a screen-printed carbon electrode (SPCE) as the substrate materials. Dendritic tri-fan blade-like PdAuCu NPs/NH₂-GO was synthesized according to a simple hydrothermal procedure and used to immobilize antibodies (Ab₂) with large surfaces areas, increased catalytic properties and good adsorption to amplify the current signals. Subsequently, Ab₂/PdAuCu NPs/NH₂-GO catalyzed the reduction of H₂O₂ in the sandwich-type immunoreactions. Under optimal conditions, the immunosensor exhibited a satisfactory response to CEA with a limit detection of 0.07 pg mL⁻¹ and a linear detection range from 0.1 pg mL⁻¹ to 200 ng mL⁻¹. The proposed immunosensor could be suitable enough for a real sample analysis of CEA, and has clinical value in the early diagnosis of cancer.

Poly(indole-5-carboxylic acid)/reduced graphene oxide/gold nanoparticles/phage-based electrochemical biosensor for highly specific detection of Yersinia pseudotuberculosis

Yersinia pseudotuberculosis is an enteric bacterium causing yersiniosis in humans. The existing Yersinia pseudotuberculosis detection methods are time-consuming, requiring a sample pretreatment step, and are unable to discriminate live/dead cells. The current work reports a phage-based electrochemical biosensor for rapid and specific detection of Yersinia pseudotuberculosis. The conductive poly(indole-5-carboxylic acid), reduced graphene oxide, and gold nanoparticles are applied for surface modification of the electrode. They possess ultra-high redox stability and retain 97.7% of current response after performing 50 consecutive cycles of cyclic voltammetry.The specific bacteriophages vB_YepM_ZN18 we isolated from hospital sewage water were immobilized on modified electrodes by Au-NH₂ bond between gold nanoparticles and phages. The biosensor fabricated with nanomaterials and phages were utilized to detect Yersinia pseudotuberculosis successfully with detection range of 5.30 × 10² to 1.05 × 10⁷ CFU mL^-1, detection limit of 3 CFU mL^-1, and assay time of 35 min. Moreover, the biosensor can specifically detect live Yersinia pseudotuberculosis without responding to phage-non-host bacteria and dead Yersinia pseudotuberculosis cells. These results suggest that the proposed biosensor is a promising tool for the rapid and selective detection of Yersinia pseudotuberculosis in food, water, and clinical samples.

CdS Quantum-Dots-Decorated V2O5 Nanosheets as Chemically Etchable Active Materials for Sensitive Photoelectrochemical Immunoassay of Carcinoembryonic Antigen

We report here CdS quantum-dots (QDs)-decorated V₂O₅ nanosheets as high-performance and chemically etchable photoelectric active materials for constructing a photoelectrochemical (PEC) immunoassay platform. CdS QDs-decorated V₂O₅ nanosheets as new photoelectric materials can show superior photocurrent to V₂O₅ nanosheets and CdS QDs under visible-light irradiation because of the promoted photogenerated electron-hole separation and the increased visible-light absorption. V₂O₅ nanosheets can be etched by ascorbic acid (AA) because of the reduction of V₂O₅ to V⁴⁺, and the photocurrent of CdS/V₂O₅-nanocomposite-modified indium tin oxide electrode decreases significantly after being etched by AA. Inspired by this phenomenon, a PEC immunoassay platform is constructed for carcinoembryonic antigen (CEA) detection by using CdS/V₂O₅ nanocomposite as the photoelectric material and AA-encapsulated liposome immunonanocapsules as labels. The linear detection range for detecting CEA is from 0.5 pg mL^-1 to 1 ng mL^-1, with a limit of detection of 0.1 pg mL^-1. The proposed method also shows good selectivity, excellent reproducibility, and satisfactory recovery in detection of CEA in human serum samples. We believe that this work will lay the foundation for the future development of V₂O₅-based materials for PEC analysis, and also provide a reasonable design and implementation for the development of PEC immunoassay.

Electrochemical biosensors based on antibody, nucleic acid and enzyme functionalized graphene for the detection of disease-related biomolecules

The application of biomacromolecule functionalized graphene electrochemical biosensors in the detection of pathogens and disease markers was reviewed.

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.

Graphene Quantum Dots Decorated Gold-Polyaniline Nanowire for Impedimetric Detection of Carcinoembryonic Antigen

A label-free impedimetric immunosensor based on N, S-graphene quantum dots@Au-polyaniline (N, S-GQDs@Au-PANI) nanowires was fabricated for the quantitative detection of carcinoembryonic antigen (CEA). The N, S-GQDs and Au-PANI were synthesized by a simple hydrothermal pyrolysis and interfacial polymerization, respectively. Subsequently, 2-9 nm N, S-GQDs are successfully decorated onto 30-50 nm Au-PANI nanowires by Au-thiol linkage to serve as the bifunctional probe for amplifying the electrochemical activity as well as anchoring anti-CEA. The N, S-GQDs@Au-PANI nanowires are excellent conducting materials to accelerate the electron transfer, while the formation of CEA antibody-antigen bioconjugates after the addition of CEA significantly increase the charge transfer resistance, and subsequently provides a highly stable and label-free immunoassay platform for the impedimetric detection of CEA. The label-free immunosensor exhibits a wide linear range from 0.5 to 1000 ng mL-1 with a low detection limit of 0.01 ng mL-1. The N, S-GQDs@Au-PANI based immunosensor also shows high selectivity and stability over other cancer makers and amino acids. Moreover, this promising platform is successfully applied to the detection of CEA in human serum samples with excellent recovery of (96.0 ± 2.6)-(103 ± 3.8)%. These results clearly demonstrate a newly developed highly efficient and label-free impedimetric immunosensor for the detection of CEA using N, S-GQDs@Au-PANI nanowires as the biosensing probe, which can pave the gateway for the fabrication of high performance and robust impedimetric immunosensor to detect cancer makers in early stage of cancer diagnosis and therapy.

Gold/WS2 nanocomposites fabricated by in-situ ultrasonication and assembling for photoelectrochemical immunosensing of carcinoembryonic antigen

Tungsten disulfide (WS₂) nanosheets were obtained by exfoliating WS₂ bulk crystals in N-methylpyrrolidone by ultrasonication. Gold nanoparticles (GNPs) were synthesized by in-situ ultrasonication of sodium citrate and HAuCl₄ while fabricating the WS₂ nanosheets. In this way, the GNPs were self-assembled on WS₂ nanosheets to form a GNPs/WS₂ nanocomposite through interaction between sulfur and gold atoms. The photoelectrochemical response of WS₂ nanosheets is significantly enhanced after integration of the GNPs. The GNPs/WS₂ nanocomposite was coated onto a glassy carbon electrode (GCE) to construct a sensing interface which then was modified with an antibody against the carcinoembryonic antigen (CEA) to obtain a photoelectrochemical immunosensor for CEA. Under optimized conditions, the decline in relative photocurrent is linearly related to the logarithm of the CEA concentration in the range from 0.001 to 40 ng mL^-1. The detection limit is 0.5 pg mL^-1 (at S/N = 3). The assay is sensitive, selective, stable and reproducible. It was applied to the determination of CEA in clinical serum samples. Graphical abstract Schematic presentation of the fabrication of Au/WS₂ nanocomposites by in-situ ultrasonication and the procedure for the CEA photoelectrochemical immunosensor preparation, and the photocurrent response towards the carcinoembryonic antigen.

A cascade amplification strategy of catalytic hairpin assembly and hybridization chain reaction for the sensitive fluorescent assay of the model protein carcinoembryonic antigen

A cascade nucleic acid amplification strategy is presented for fluorometric aptamer based determination of the model protein carcinoembryonic antigen (CEA). Amplification is accomplished by combining catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR). In this assay, a specially designed single-stranded DNA containing the aptamer sequence (AS) specific for CEA is hybridized with an inhibitor strand (IS) to form a double-stranded DNA (IS@AS). In the presence of CEA, it will recognize and bind to the AS strand which causes the release of IS. By introducing two DNA hairpins (H1 and H2; these containing complementary sequences) CHA will be activated via the hybridization reactions of H1 and H2. This is accompanying by the formation of a double-stranded DNA (H1-H2) and the release of CEA@AS. The liberated CEA@AS further drives successive recycling of the CHA, thereby generating further copies of H1-H2. The resultant H1-H2 hybrids act as primers and trigger HCR with the help of other two DNA hairpins (H3 and H4) containing G-rich toehold at the 5'-terminus and 3'-terminus of H3 and H4, respectively. The fluorescent probe N-methyl mesoporphyrin IX (NMM) is finally intercalated into the G-rich domains of the long DNA nanostructures due to formation of G-quadruplex structures. This generates a fluorescent signal (best measured at excitation/emission wavelengths of 399/610 nm) that increases with the concentration of target (CEA). This aptamer-based fluorescence assay is highly sensitive and has a linear range that covers the 1 pg·mL^-1 to 2 ng·mL^-1 CEA concentration range, with a 0.3 pg·mL^-1 detection limit. Graphical abstract By integrating catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) for effective signal enhancement, a novel cascade amplification strategy is presented to develop a sensitive and selective fluorescent method for the assay of the model protein carcinoembryonic antigen (CEA).

Nanomaterial-doped conducting polymers for electrochemical sensors and biosensors

This review summarizes recent advances in the development of electrochemical sensors and biosensors based on nanomaterial doped conducting polymers.

Nanotechnology-Enhanced No-Wash Biosensors for in Vitro Diagnostics of Cancer

In vitro biosensors have been an integral component for early diagnosis of cancer in the clinic. Among them, no-wash biosensors, which only depend on the simple mixing of the signal generating probes and the sample solution without additional washing and separation steps, have been found to be particularly attractive. The outstanding advantages of facile, convenient, and rapid response of no-wash biosensors are especially suitable for point-of-care testing (POCT). One fast-growing field of no-wash biosensor design involves the usage of nanomaterials as signal amplification carriers or direct signal generating elements. The analytical capacity of no-wash biosensors with respect to sensitivity or limit of detection, specificity, stability, and multiplexing detection capacity is largely improved because of their large surface area, excellent optical, electrical, catalytic, and magnetic properties. This review provides a comprehensive overview of various nanomaterial-enhanced no-wash biosensing technologies and focuses on the analysis of the underlying mechanism of these technologies applied for the early detection of cancer biomarkers ranging from small molecules to proteins, and even whole cancerous cells. Representative examples are selected to demonstrate the proof-of-concept with promising applications for in vitro diagnostics of cancer. Finally, a brief discussion of common unresolved issues and a perspective outlook on the field are provided.

High sensitivity surface plasmon resonance biosensor for detection of microRNA and small molecule based on graphene oxide-gold nanoparticles composites

A versatile and sensitive surface plasmon resonance (SPR) biosensor based on two layers of graphene oxide-gold nanoparticles (GO-AuNPs) composites was designed for the detection of microRNA (miRNA) and small molecule adenosine. The bottom layer, which acted as a functionalized substrate on the sensor chip, provided a high specific surface area convenient for the immobilization of capture DNA molecules. The upper layer served as a signal-amplification element. By employing these two layers of GO-AuNPs composites, the dual amplification strategy was achieved so that a measurement of miRNA-141 with a detection limit of 0.1fM was obtained. Moreover, the developed SPR biosensor showed decent selectivity toward miRNA-200 family members. Especially, the SPR biosensor demonstrated its applicability for the detection of miRNA-141 in cancer cell extractions, and the results obtained were consistent with those obtained by qRT-PCR. Interestingly, small molecule adenosine could also be detected using this SPR biosensor in combination with a split aptamer. Considering the superior sensitivity, selectivity and generality, this work promised much potential for the detection of various biomolecules.