Ultrasensitive electrochemical immunoassay for carcinoembryonic antigen based on three-dimensional macroporous gold nanoparticles/graphene composite platform and multienzyme functionalized nanoporous silver label

A simple electrochemical strategy for the detection of the cancer marker CA19-9 by signal amplification using copper organic framework nanocomposite

In this work, label-free electrochemical immunosensing of the cancer biomarker carbohydrate antigen 19-9 (CA19-9) is reported using [Fe(CN)6]3-/4- as a signal probe and a copper organic framework (Cu-BTC) nanocomposite for the amplification of the signal. The immunosensor was fabricated by the following process. First, the Cu-BTC nanomaterial with a larger surface area and good biocompatibility was synthesized to improve the dispersion of gold nanoparticles (Au NPs). Then, nitrogen-doped graphene (N-GR) was combined with Cu-BTC to form the nanocomposite. The synthesized Cu-BTC@N-GR@AuNPs@CS nanocomposite was employed to modify the surface of the immunosensor to accelerate the electron transfer rate and improve the immobilization amount of CA19-9 antibodies (Ab). Various techniques, including TEM, SEM and XPS were used to characterize Cu-BTC and nanocomposites. Differential pulse voltammetry (DPV) was used to measure the electrochemical response of the immunosensor in [Fe(CN)6]3-/4-. The signal intensity of the immunosensor was linearly changed upon increasing the concentration of CA19-9 antigen from 10 μU mL-1 to 100 U mL-1, and a detection limit of 4.2 μU mL-1 was achieved. Furthermore, the immunosensor showed good stability, reproducibility and specificity, indicating its potential application in clinical analysis.

Gold nanoparticles-oxidized multi-walled carbon nanotubes as electrochemiluminescence immunosensors

Oxidized multi-walled carbon nanotube/nano-gold (AuNP-ox-MWCNT) composites with strong electrochemiluminescence (ECL) activity were applied to construct a new ECL immunosensor for the detection of carcinoembryonic antigen (CEA). The immunosensor showed a linear response range of 10-100 ng mL^-1 and detection limit of 0.76 ng mL^-1 (at a signal-to-noise ratio of 3). The as-developed immunosensor exhibited several advantages, including being simple to fabricate and being label free. The results indicated that ox-MWCNTs as a luminescent material have great application potential in analysis.

Copper peroxide/ZIF-8 self-producing H2O2 triggered cascade reaction for amperometric immunoassay of carbohydrate antigen 19-9

Generally, H₂O₂ is frequently adopted to improve analysis capabilities of various detection systems. However, the addition of H₂O₂ with relatively higher concentration can lower the bioactivity of antibodies or antigens and the sensing interface stability in most peroxidase and peroxidase-like immunosensors. In order to solve these issues, we designed a novel copper peroxide/ZIF-8 immunoprobe that can self-produce H₂O₂ to trigger a cascade reaction for the sensitive detection of carbohydrate antigen 19-9. Specifically, CP/ZIF-8 plays a key role as a "signal switch" in the immunosensor. In the presence of HCl, the structures of ZIF-8 and copper peroxide can be broken, producing Cu²⁺ and H₂O₂ and a subsequent Fenton-type reaction that generates •OH. The resulting •OH can induce the decomposition of 3-aminobenzeneboronic acid/poly (vinyl alcohol) (PVA) film on the electrode. Although the immunosensor initially showed little current signal due to the poor conductivity pf ZIF-8 and PVA, the current signal was significantly amplified by a HCl-triggered cascade reaction. Under optimal conditions, the immunosensor displayed a wide linear range from 0.0001 to 100 U mL^-1 with an ultralow limit of detection of 53.5 μU mL^-1 (S/N = 3) for carbohydrate antigen 19-9. Considering these advantages, namely self-producing H₂O₂ and easy operation, this strategy paves a new way to design other novel sensors.

Label-assisted chemical adsorption triggered conversion of electroactivity of sensing interface to achieve the Ag/AgCl process for ultrasensitive detection of CA 19-9

Efficient strategies in enhancing sensitivity are pivotal to ultrasensitive detection of tumor markers. In this work, based on the strategy of label-assisted chemical adsorption triggered conversion of electroactivity of sensing interface, a Ag/AgCl process was achieved to enhance sensitivity of the constructed sandwich-type amperometric immunosensor for ultrasensitive detection of carbohydrate antigen 19-9 (CA19-9). Briefly, polydopamine-Ag nanoparticles (PDA-Ag NPs), as signal precursor, combined with labeling antibody were served as labels and graphene oxide-melamine (GO-MA) substrate with chemical absorption capacity was applied as smart sensing interface. After successfully incubating labels, there was primitively no current response due to the poor conductivity between labels and electrode. However, in the presence of H₂O₂, Ag NPs from labels can be etched into Ag ions, which were adsorbed by GO-MA to form GO-MA-Ag as electroactive substrate. Then, the substrate exhibited a sharp and stable electrochemistry peak of solid-state Ag/AgCl process in the buffer containing KCl. The sensitivity toward detection of CA19-9 was notably enhanced based on the appearance of sharp peak. Under optimum conditions, the designed immunosensor demonstrated a wide working range from 0.0001 to 100 U mL^-1 and an ultralow detection limit 0.032 mU mL^-1. Thus, utilizing this strategy to construct immunosensor was highly promising in clinical diagnosis for ultrasensitive detection of tumor makers.

Screen printed carbon electrode sensor with thiol graphene quantum dots and gold nanoparticles for voltammetric determination of solatol

This work, a highly selective and sensitive sensor is described for voltammetric determination of the sotalol (SOT). The dual actions of sotalol lead to reductions in the automaticity of myocardial cells and in conduction through the atrioventricular node. Drug analysis has an extensive impact on public health. The molecularly imprinted sensor was constructed by modifying a screen printed carbon electrode (SPCE) with thiol graphene quantum dots (GQD-SH) and gold nanoparticles (AuNPs). Under optimal conditions the nanotools has a dynamic range that covers the 0.1-250 μM SOT concentration range, and the detection limit is 0.035 μM. This is lower than any of the previously reported methods. The MIP-sensor also exhibited excellent selectivity, good stability and adequate reproducibility for the detection of the SOT over its structural analogs. The prepared sensor was successfully applied to the measurement of SOT in various real samples including tablet and human blood serum.

Three dimensional sea-urchin-like PdAuCu nanocrystals/ferrocene-grafted-polylysine as an efficient probe to amplify the electrochemical signals for ultrasensitive immunoassay of carcinoembryonic antigen

A novel sandwich-like immunosensor was efficiently fabricated for detection of carcinoembryonic antigen (CEA) with three dimensional sea-urchin-like PdAuCu nanocrystals (PdAuCu NCs)/ferrocene-grafted-polylysine (Fc-g-PLL) as the label of secondary antibodies (Ab₂) and Au nanoparticles (Au NPs) as the substrate material. Herein, PdAuCu NCs were directly synthesized with polyethylene oxide (PEO) as a growth-directing agent by a facile one-step aqueous method without any organic solvent. Meanwhile, Fc-g-PLL was obtained by covalent linkage of Fc with PLL via Schiff-base reaction. The well-dispersed PdAuCu NCs by Fc-g-PLL have the enlarged surface area, enhanced catalytic properties and superior biocompatibility to amplify the current signals. The resultant immunosensor shows linear relationship of the electrochemical responses with the CEA concentrations within a broader linear range (0.001-100.0 ng mL^-1) and a lower detection limit (0.23 pg mL^-1, S/N = 3). Furthermore, the immunosensor was explored for practical assay of CEA in human serum samples with accredited results. The novel immunoassay provides a feasible platform for early medical diagnosis.

Fabrication of an ultrasensitive and selective electrochemical aptasensor to detect carcinoembryonic antigen by using a new nanocomposite

A lable-free electrochemical aptasensor was successfully developed for the sensitive detection of carcinoembryonic antigen as a tumor biomarker. To do this, a ternary nanocomposite of hemin, graphene oxide and multi-walled carbon nanotubes was used. The aptamer can be attached to the surface of a hemin, graphene oxide and multi-walled carbon nanotubes glassy carbon electrode through -NHCO- covalent bonds to form a sensing surface. Through fourier transform infrared spectroscopy and scanning electron microscopy, it was indicated that hemin can be successfully incorporated into hemin, graphene oxide and multi-walled carbon nanotubes. Hemin, which protects graphene nanosheets, also serves as an in-situ probe owing to its well-defined redox properties. Multi-walled carbon nanotubes in the modifier enhance conductivity and facilitate the electron transfer between hemin and the glassy carbon electrode. In this study, carcinoembryonic antigen got specifically bound to the aptamer, and the current changes were used for selective and specific detection of that antigen. The devised aptasensor proved to have excellent performance with a wide linear range of 1.0 × 10^-15 - 1.0 × 10^-8 gmL^-1 and a detection limit of 0.82 fg mL^-1. The inter-day and intra-day values of RSD% were obtained in the range of 0.10-2.91 and 2.21-4.56 respectively. According to the experiments conducted on real samples, it may be claimed that the proposed label-free electrochemical aptasensor is capable enough of determining carcinoembryonic antigen in clinical diagnostics.

Tactile Chemomechanical Transduction Based on an Elastic Microstructured Array to Enhance the Sensitivity of Portable Biosensors

Tactile sensors capable of perceiving biophysical signals such as force, pressure, or strain have attracted extensive interest for versatile applications in electronic skin, noninvasive healthcare, and biomimetic prostheses. Despite these great achievements, they are still incapable of detecting bio/chemical signals that provide even more meaningful and precise health information due to the lack of efficient transduction principles. Herein, a tactile chemomechanical transduction strategy that enables the tactile sensor to perceive bio/chemical signals is proposed. In this methodology, pyramidal tactile sensors are linked with biomarker-induced gas-producing reactions, which transduce biomarker signals to electrical signals in real time. The method is advantageous as it enhances electrical signals by more than tenfold based on a triple-step signal amplification strategy, as compared to traditional electrical biosensors. It also constitutes a portable and general platform capable of quantifying a wide spectrum of targets including carcinoembryonic antigen, interferon-γ, and adenosine. Such tactile chemomechanical transduction would greatly broaden the application of tactile sensors toward bio/chemical signals perception which can be used in ultrasensitive portable biosensors and chemical-responsive chemomechanical systems.

Recent advances in functionalized micro and mesoporous carbon materials: synthesis and applications

Functionalized nanoporous carbon materials have attracted the colossal interest of the materials science fraternity owing to their intriguing physical and chemical properties including a well-ordered porous structure, exemplary high specific surface areas, electronic and ionic conductivity, excellent accessibility to active sites, and enhanced mass transport and diffusion. These properties make them a special and unique choice for various applications in divergent fields such as energy storage batteries, supercapacitors, energy conversion fuel cells, adsorption/separation of bulky molecules, heterogeneous catalysts, catalyst supports, photocatalysis, carbon capture, gas storage, biomolecule detection, vapour sensing and drug delivery. Because of the anisotropic and synergistic effects arising from the heteroatom doping at the nanoscale, these novel materials show high potential especially in electrochemical applications such as batteries, supercapacitors and electrocatalysts for fuel cell applications and water electrolysis. In order to gain the optimal benefit, it is necessary to implement tailor made functionalities in the porous carbon surfaces as well as in the carbon skeleton through the comprehensive experimentation. These most appealing nanoporous carbon materials can be synthesized through the carbonization of high carbon containing molecular precursors by using soft or hard templating or non-templating pathways. This review encompasses the approaches and the wide range of methodologies that have been employed over the last five years in the preparation and functionalisation of nanoporous carbon materials via incorporation of metals, non-metal heteroatoms, multiple heteroatoms, and various surface functional groups that mostly dictate their place in a wide range of practical applications.

Graphene- gold based nanocomposites applications in cancer diseases; Efficient detection and therapeutic tools

Early detection and efficient treatment of cancer disease remains a drastic challenge in 21st century. Throughout the bulk of funds, studies, and current therapeutics, cancer seems to aggressively advance with drug resistance strains and recurrence rates. Nevertheless, nanotechnologies have indeed given hope to be the next generation for oncology applications. According to US National cancer institute, it is anticipated to revolutionize the perspectives of cancer diagnosis and therapy. With such success, nano-hybrid strategy creates a marvelous preference. Herein, graphene-gold based composites are being increasingly studied in the field of oncology, for their outstanding performance as robust vehicle of therapeutic agents, built-in optical diagnostic features, and functionality as theranostic system. Additional modes of treatments are also applicable including photothermal, photodynamic, as well as combined therapy. This review aims to demonstrate the various cancer-related applications of graphene-gold based hybrids in terms of detection and therapy, highlighting the major attributes that led to designate such system as a promising ally in the war against cancer.

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 electrochemical detection of Dicer1 3'UTR for the fast analysis of alternative cleavage and polyadenylation

Alternative cleavage and polyadenylation (APA) is involved in several important biological processes in animals, e.g. cell growth and development, and cancer progression. The increasing data show that cancer cells are inclined to produce mRNA isoforms with a shortened 3'UTR undergoing APA. For example, the Dicer1 isoform with a shorter 3'untranslated region (3'UTR) was found to be overexpressed in some cancer cells, which may be used as a potential novel prognostic biomarker for cancer. In the present work, a novel electrochemical biosensor for ultrasensitive determination of Dicer1 was designed by using gold nanoparticles and p-sulfonated calix[6]arene functionalized reduced graphene oxide (Au@SCX6-rGO) as nanocarriers. The results showed that the expressions of the shorter 3'UTR (Dicer1-S) both in BT474 and SKBR3 were obviously higher than those of the longer Dicer1 (Dicer1-L) by the constructed biosensor, which agreed well with the result analyzed by the RT-qPCR method. The detection ranges of Dicer1-S and Dicer1-L were 10^-14-10^-9 M and 10^-15-10^-10 M. The LODs were 3.5 and 0.53 fM. The specificity of the proposed biosensor was also very high. For the first time, the expressional analysis of different 3'UTRs caused by APA was studied by an electrochemical method. Moreover, the use of a macrocyclic host for constructing an electrochemical/biosensing platform has rarely been reported. The proposed electrochemical sensing strategy is thus expected to provide a new method for determination of novel biomarkers and a novel method for fast and cheap analysis of APA.

Graphene and the immune system: Challenges and potentiality

In the growing area of nanomedicine, graphene-based materials (GBMs) are some of the most recent explored nanomaterials. For the majority of GBM applications in nanomedicine, the immune system plays a fundamental role. It is necessary to well understand the complexity of the interactions between GBMs, the immune cells, and the immune components and how they could be of advantage for novel effective diagnostic and therapeutic approaches. In this review, we aimed at painting the current picture of GBMs in the background of the immune system. The picture we have drawn looks like a cubist image, a sort of Picasso-like portrait looking at the topic from all perspectives: the challenges (due to the potential toxicity) and the potentiality like the conjugation of GBMs to biomolecules to develop advanced nanomedicine tools. In this context, we have described and discussed i) the impact of graphene on immune cells, ii) graphene as immunobiosensor, and iii) antibodies conjugated to graphene for tumor targeting. Thanks to the huge advances on graphene research, it seems realistic to hypothesize in the near future that some graphene immunoconjugates, endowed of defined immune properties, can go through preclinical test and be successfully used in nanomedicine.

Screen-printed electrode produced by printed-circuit board technology. Application to Cancer Biomarker Detection by means of plastic antibody as sensing material

This research work presents, for the first time, a screen-printed electrode (SPE) made on a PCB board with silver tracks (Ag) and a three electrode configuration (AgxO-working, AgxO-counter and Ag/AgxO-reference electrodes), following the same approach as printed-circuit boards (PCBs). This low cost and disposable device was tested for screening a cancer biomarker in point-of-care. The selected biomarker was carcinogenic embryonic antigen (CEA) protein, routinely used to follow-up the progression of specific cancer diseases. The biosensor was constructed by assembling a plastic antibody on the Ag-working electrode area, acting as the biorecognition element of the device. The protein molecules that were entrapped on the polymer and positioned at the outer surface of the polypyrrole (PPy) film were removed by protease action. The imprinting effect was tested by preparing non-imprinted (NPPy) material, including only PPy as biorecognition element. Infrared and Raman studies confirmed the surface modification of these electrodes. The ability of the sensing material to rebind CEA was measured by several electrochemical techniques: cyclic voltammetry (CV), impedance spectroscopy (EIS) and square wave voltammetry (SWV). The linear response ranged from 0.05 to 1.25 pg/mL against logarithm concentration. Overall, producing screen-printed electrodes by means of conventional PCB technology showed promising features, mostly regarding cost and prompt availability. The plastic antibody-based biosensor also seems to be a promising tool for screening CEA in point-of-care, with low response time, low cost, good sensitivity and high stability.

Proximity hybridization-regulated electrochemical stripping of silver nanoparticles via nanogold induced deposition for immunoassay

An electrochemical immunosensor was developed for detection of a biomarkerviatarget-induced proximity hybridization and electrochemical stripping analysis of silver nanoparticles.

Immunosensing procedures for carcinoembryonic antigen using graphene and nanocomposites

Two-dimensional (2D) graphene, sp²-hybridized carbon, and its two major derivatives, graphene oxide (GO) and reduced graphene oxide (rGO) have played an important role in immunoassays (IAs) and immunosensing (IMS) platforms for the detection of carcinoembryonic antigen (CEA), an implicated tumor biomarker found in several types of cancer. The graphene family with high surface area is functionalized to form stable nanocomposites with gold nanoparticles (AuNPs) and electron mediators. The capture anti-CEA antibody (Ab) with high density can be anchored on AuNPs of such composites to provide remarkable detection sensitivity, significantly below the level found in normal subjects and cancer patients. Electrochemical and fluorescence/chemiluminescence-quenching properties of graphene-based nanocomposites are exploited in various detection schemes. Future endeavors are envisioned for the development of an array platform with high-throughput for CEA together with other tumor biomarkers and C-reactive protein, a universal biomarker for infection and inflammation. The ongoing efforts dedicated to the replacement of a lab-based detector by a cellphone with smart applications will further enable cost-effective and frequent monitoring of CEA in order to establish its clinical relevance and provide tools for real-time monitoring of patients during chemotherapy.

A sensitive electrochemical sensor for direct phoxim detection based on an electrodeposited reduced graphene oxide–gold nanocomposite

The principal objective of this study was to develop a sensitive and selective electrochemical sensor for phoxim detection based on a reduced graphene oxide–gold nanocomposite (RGO–Au) modified grassy carbon electrode (GCE).

Immunosensor for prostate-specific antigen using Au/Pd@flower-like SnO2 as platform and Au@mesoporous carbon as signal amplification

The illustration for the constructed electrochemical immunosensor and the signal amplification strategy.

A label-free electrochemical immunosensor for carcinoembryonic antigen detection on a graphene platform doped with poly(3,4-ethylenedioxythiophene)/Au nanoparticles

In this work, a two-step method was developed for the fabrication of a graphene sensing platform doped with poly(3,4-ethylenedioxythiophene)/Au nanoparticles (AuNPs/PEDOT/GR).

Cerium oxide-deposited mesoporous silica nanoparticles for the determination of carcinoembryonic antigen in serum using inductively coupled plasma-mass spectrometry

CeO2-deposited mesoporous silica nanoparticles were synthesized as a probe to determine carcinoembryonic antigen (CEA) in serum by inductively coupled plasma-mass spectrometry (ICP-MS). The prepared mesoporous nanoparticles were modified and tagged to the target for sandwich-type immunoassay. Fe3O4 magnetic nanoparticles (MNPs) were also synthesized and immobilized with antibody to extract the target biomarker. The calibration curve of the synthesized CeO2-deposited silica nanoparticles, which was plotted by the signal ratio of (140)Ce/(57)Fe measured by ICP-MS vs. the concentration of CEA, showed excellent linearity and sensitivity owing to the signal amplification and low spectral interference. Under optimal conditions, the sandwich-type analytical method was applied to determine CEA in serum spiked in the range of 0.001-5 ng mL(-1) and showed a limit of detection of 0.36 ng mL(-1). Since the deposited CeO2 in the mesoporous silica layer can be substituted by other metal compounds, various kinds of metal-deposited nanoparticles can be prepared as probe materials for multiplex detection in bioanalysis.

A chitosan-Au-hyperbranched polyester nanoparticles-based antifouling immunosensor for sensitive detection of carcinoembryonic antigen

An electrochemical immunosensor was developed for the detection of carcinoembryonic antigen in whole blood, based on the antibiofouling properties of carboxylic acid group functionalized hyperbranched polyester nanoparticles.