Efficiency of electrochemical immuno- vs. apta(geno)sensors for multiple cancer biomarkers detection

The interest in biosensors technology has been constantly growing over the last few years. It is still the biggest challenge to design biosensors able to detect two or more analytes in a single measurement. Electrochemical methods are frequently used for this purpose, mainly due to the possibility of applying two or more different redox labels characterized by independent and distinguished electrochemical signals. In addition to antibodies, nucleic acids (aptamers) have been increasingly used as bioreceptors in the construction of such sensors. Within this review paper, we have collected the examples of electrochemical immuno- and geno(apta)sensors for simultaneous detection of multiple analytes. Based on many published literature examples, we have emphasized the recent application of multiplexed platforms for detection of cancer biomarkers. It has allowed us to compare the progress in design strategies, including novel nanomaterials and amplification of signals, to get as low as possible limits of detection. We have focused on multi-electrode and multi-label strategies based on redox-active labels, such as ferrocene, anthraquinone, methylene blue, thionine, hemin and quantum dots, or metal ions such as Ag+, Pb2+, Cd2+, Zn2+, Cu2+ and others. We have finally discussed the possible way of development, challenges and prospects in the area of multianalyte electrochemical immuno- and geno(apta)sensors.

Photoinduced Ordered Growth of Copper-Doped Polyaniline Nanotubes: A Method to Improve the Catalytic Activity for C-N Coupling Reactions

Polyaniline-supported metal nanoparticles (M@PANIs) have been widely employed as catalysts for organic reactions. Traditionally, the catalytic activities of the materials can be improved by introducing functional groups onto the aniline monomers, but it may enhance the catalyst cost and reduce the production yield of the material. This work reports a new strategy for improving the catalytic activity of M@PANIs. It was found that induced by visible light in the presence of a polymeric carbon nitride catalyst and copper dopant, the oxidative polymerization of simple aniline occurred slowly and orderly to produce the copper-doped polyaniline nanotubes. The unique tubular structure protected the catalytically active Cu(I) inside and endowed even more sufficient contact of the catalytic sites with reactants so that the material exhibited excellent catalytic performances in C-N coupling reactions.

A facile electrochemical immunosensor based on EDTA-Pb2+ complexation reaction

The sensitivity of electrochemical (EC) sensors has been improved through the development of multiple approaches. However, the majority of EC sensors were limited in their practical application by high costs or tedious procedures. Herein, based on ethylenediaminetetraacetic acid (EDTA)-Pb2+ complexation reaction, a facile and affordable immunosensor was designed. Pb2+-magnesium silicate hydrate was served as the sensing substrate. The immunorecognition process was carried out in the Eppendorf tube, and antibody-functionalized Pb2+-polydopamine was utilized as immunoprobe. In the tube, the quantitative and appropriate excess of EDTA was introduced to complex with Pb2+ on the immunoprobes. The remaining EDTA was added to the sensing substrate surface to coordinate with some Pb2+ in it. This leaded to the reduction of the EC signal of Pb2+, which was related to the antigen concentration. Using prostate-specific antigen as the model analyte, the sensitive detection was realized with a low limit of detection (30.49 fg mL-1). Remarkably, the assay results were available within 24 min, sensibly faster than the most existing EC sensors.

Bio-functionalized carbon dots for signaling immuno-reaction of carcinoembryonic antigen in an electrochemical biosensor for cancer biomarker detection

Early diagnosis of cancer demands sensitive and accurate detection of cancer biomarkers in blood. Carbon dots (CDs) bio-functionalization with antibodies, peptides or aptamers have played significant role in cancer diagnosis and targeted cancer therapy. Herein, a biosensor for detection of cancer biomarker carcinoembryonic antigen (CEA) in blood serum has been designed using CDs bio-functionalized with HRP-conjugated CEA antibody (CUCDs@CEAAb2) as detection probe. CDs were synthesized by upscaling of cow urine, a nitrogen rich biomass waste, by hydrothermal method. Detection probe based on CDs resulted in 3.5 times higher sensitivity as compared to conventional electrochemical sandwich immunoassay. To further improve the sensor performance, hyper-branched polyethylenimine grafted poly amino aniline (PEI-g-PAANI) was used as the sensing interface, which enabled immobilization of higher amount of capture antibody. Detection of CEA in human blood serum coupled with wide linear range (0.5-50 ng/ml), good specificity, stability, reproducibility and low detection limit (10 pg/ml) signified the excellence of CUCDs based CEA immunosensor. CUCDs exhibited excitation wavelength dependent fluorescence property and showed strong blue emission under UV irradiation. MTT assay indicated that the material is not toxic towards human dental pulp stem cells (hDPSCs) and MG63 osteosarcoma cells (cell viability > 90%). The present study demonstrates a methodology for valorization of animal waste to a cost-effective carbon based functional nanomaterial for clinical detection of cancer biomarkers.

3-Polythiophene Acetic Acid Nanosphere Anchored Few-Layer Graphene Nanocomposites for Label-Free Electrochemical Immunosensing of Liver Cancer Biomarker

This study devised a label-free electrochemical immunosensor for the quantitative detection of alpha-fetoprotein (AFP). 3-Polythiophene acetic acid (3-PTAA) nanoparticles were anchored onto a few-layer graphene (FLG) nanosheet, and the resulting nanocomposite was utilized as the immunosensor platform. The AFP antibody (anti-AFP) was immobilized on 3-PTAA@FLG via a covalent interaction between the amine group of anti-AFP and the carboxylic group of 3-PTAA via ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) coupling. FLG is largely responsible for providing electrochemical signals, whereas 3-PTAA nanoparticles are well-known for their ability to be compatible with biological molecules in neutral aqueous solutions. Moreover, the carboxyl group present in 3-PTAA effectively binds anti-AFP through EDC/NHS conjugation. Owing to good dispersibility and higher surface area of 3-PTAA, it is very convenient for casting the polymer directly on the electrode substrate followed by immobilization of anti-AFP. Thus, it is feasible to regulate the activity of AFP proteins and control the spatial distribution of the immobilized anti-AFP proteins. The electrochemical sensing performance was assessed via cyclic voltammetry and electrochemical impedance spectroscopy. For an increase in the bioconjugate concentration, the results demonstrated a surge in charge-transfer resistance and a consequent decline in the current response. This approach effectively detected AFP at an extended dynamic range of 0.0001-250 ng/mL with a detection limit of 0.047 pg/mL. Furthermore, the sensing capacity of the immunosensor for AFP detection has been demonstrated to be steady in real human serum cultures. Our approach exhibits good electrochemical performance in terms of reproducibility, selectivity, and stability, which would surely impart budding applications in the clinical diagnosis of several other tumor markers.

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.

Fractionated Sonodynamic Therapy Using Gold@Poly(ortho-aminophenol) Nanoparticles and Multistep Low-Intensity Ultrasound Irradiation to Treat Melanoma Cancer: In Vitro and In Vivo Studies

OBJECTIVE

Cancer treatment using ultrasound irradiation with low intensities along with a sonosensitizer has been found to have significant advantages, such as high penetration depth in tissues, non-invasive therapeutic character, minor side effects, good patient adherence and preferential tumor area treatment. In the present study, gold nanoparticles covered by poly(ortho-aminophenol) (Au@POAP NPs) were synthesized and characterized as a new sonosensitizer.

METHODS

We investigated Au@POAP NPs efficacy on fractionated ultrasound irradiation for treatment of melanoma cancer in vitro as well as in vivo.

DISCUSSION

In vitro examinations revealed that although Au@POAP NPs (with a mean size of 9.8 nm) alone represented concentration-dependent cytotoxicity against the B16/F10 cell line, multistep ultrasound irradiation (1 MHz frequency, 1.0 W/cm² intensity, 60 s irradiation time) of the cells in the attendance of Au@POAP NPs led to efficient cell sonodynamic therapy (SDT) and death. Histological analyses revealed that in vivo fractionated SDT toward melanoma tumors of male balb/c mice led to no residual viable tumor cell after 10 d.

CONCLUSION

A deep sonosensitizing effectiveness of Au@POAP NPs on fractionated low-intensity ultrasound irradiation was attained with the main mechanism of tumor cell eradication of promotion of apoptosis or necrosis through dramatically increased reactive oxygen species levels.

Redox-labelled detection probe enabled immunoassay for simultaneous detection of multiple cancer biomarkers

Some of the cancer biomarkers often lack specificity and sensitivity; thus, simultaneous detection of multiple biomarkers can make the diagnosis more accurate. Also, simple sensing system without utilization of extra reagents like mediator or substrate during detection event is desirable for point-of-care testing. To address this, mediator and substrate-free amperometric biosensor for simultaneous detection of cancer biomarkers carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) have been demonstrated by designing two different redox-labelled detection probes. Colloidal nanoparticles of polyaniline-pectin conjugated with AFP antibody along with ferrocene and silver nanoparticles conjugated with CEA antibody along with anthraquinone were used as redox probes to bind with AFP and CEA during the detection event. Sensor constructed using carboxylic acid tethered polyaniline as immobilization matrix displayed 5 times wider linear range than conventional polyaniline for AFP and CEA detection by sandwich electrochemical assay. The detection limit was 30 pg mL^-1 for AFP and 80 pg mL^-1 for CEA. The biosensor displayed appropriate sensitivity, good specificity, and negligible cross-reactivity between the two targets. The proposed sensor was used to determine APF and CEA in human blood serum. The strategy demonstrated can be further extended for detection of panel of cancer biomarkers by designing appropriate redox probes.

Monoclonal antibody as a targeting mediator for nanoparticle targeted delivery system for lung cancer

Lung cancer is the second most common type of cancer after breast cancer. It ranks first in terms of mortality rate among all types of cancer. Lung cancer therapies are still being developed, one of which makes use of nanoparticle technology. However, conjugation with specific ligands capable of delivering drugs more precisely to cancer sites is still required to enhance nanoparticle targeting performance. Monoclonal antibodies are one type of mediator that can actively target nanoparticles. Due to the large number of antigens on the surface of cancer cells, monoclonal antibodies are widely used to deliver nanoparticles and improve drug targeting to cancer cells. Unfortunately, these antibodies have some drawbacks, such as rapid elimination, which results in a short half-life and ineffective dose. As a result, many of them are formulated in nanoparticles to minimize their major drawbacks and enhance drug targeting. This review summarizes and discusses articles on developing and applying various types of monoclonal antibody ligand nanoparticles as lung cancer target drugs. This review will serve as a guide for the choice of nanoparticle systems containing monoclonal antibody ligands for drug delivery in lung cancer therapy.

Highly Conductive PPy-PEDOT:PSS Hybrid Hydrogel with Superior Biocompatibility for Bioelectronics Application

Conductive polymer hydrogels (CPHs) hold significant promise in broad applications, such as bioelectronics and energy devices. Hitherto, the development of a facile and scalable synthesis method for CPHs with high electrical conductivity and biocompatibility has still been a challenge. Herein, we demonstrate highly conductive PPy-PEDOT:PSS hybrid hydrogels which are prepared by a simple solution-mixing method. This fabrication method involves the mixing of a pyrrole monomer with a PEDOT:PSS dispersion, followed by in situ chemical oxidative polymerization to form polypyrrole (PPy). The electrostatic interaction between negatively charged PSS and positively charged conjugated PPy facilitates the formation of PPy-PEDOT:PSS hybrid hydrogels. The conductivity of the PPy-PEDOT:PSS hybrid hydrogels is 867 S m^-1. The PPy-PEDOT:PSS hybrid hydrogels show excellent biocompatibility. Moreover, the PPy-PEDOT:PSS hybrid hydrogels have a hierarchical porous structure which facilitates the 3D cell culture within the hydrogels. The PPy-PEDOT:PSS hybrid hydrogels exhibit excellent in situ biomolecular detection and real-time cell proliferation monitoring performance, indicating their potential as highly sensitive electrochemical biosensors for bioelectronics applications. Our strategy for the fabrication of CPHs with the electrostatic interaction between the negatively charged conductive polymer and positively charged conductive polymer would provide new opportunities for the design of highly conductive conjugated hydrogels for bioelectronics applications and energy devices.

A novel electrochemical lung cancer biomarker cytokeratin 19 fragment antigen 21-1 immunosensor based on Si3N4/MoS2 incorporated MWCNTs and core-shell type magnetic nanoparticles

Lung cancer is one of deadliest and most life threatening cancer types. Cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) is a significant biomarker for the diagnosis of non-small cell lung cancer (NSCLC). Due to these reasons, a novel electrochemical immunosensor based on a silicon nitride (Si3N4)-molybdenum disulfide (MoS2) composite on multi-walled carbon nanotubes (Si3N4/MoS2-MWCNTs) as an electrochemical sensor platform and core-shell type magnetic mesoporous silica nanoparticles@gold nanoparticles (MMSNs@AuNPs) as a signal amplifier was presented for CYFRA21-1 detection in this study. Capture antibody (Ab1) immobilization on a Si3N4/MoS2-MWCNT modified glassy carbon electrode (Si3N4/MoS2-MWCNTs/GCE) was firstly successfully performed by stable electrostatic/ionic interactions between the -NH2 groups of the capture antibody and the polar groups of Si3N4/MoS2. Then, specific antibody-antigen interactions between the electrochemical sensor platform and the signal amplifier formed a novel voltammetric CYFRA21-1 immunosensor. The prepared composite materials and electrochemical sensor surfaces were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A linearity range of 0.01-1.0 pg mL-1 and a low detection limit (LOD) of 2.00 fg mL-1 were also obtained for analytical applications. Thus, the proposed immunosensor based on Si3N4/MoS2-MWCNTs and MMSNs@AuNPs has great potential for medical diagnosis of lung cancer.

Multiplex bioassaying of cancer proteins and biomacromolecules: Nanotechnological, structural and technical perspectives

Since the specific proteins (carbohydrate antigens, ligands and interleukins) get raised up in body tissue or fluids in cancer cases, early detection of them will provide an effective treatment and survival rate. Sensitive and accurate determination of multiple cancer proteins can be engaged in chorus by simultaneous/multiplex detection in the biomedical fields. Bioassaying technology is one of the non-invasive, high-sensitive, and economical methods. Currently, extensive application of nanomaterial (biocompatible polymers, metallic and metal oxide) in bioassays resulted in ultra-high sensitive and selective diagnosis. This review article focuses on types of multiplex bioassays for delicate and specific determination of cancer proteins for diagnostic aims. It also covers two modes of multiplex bioassays as multi labeled bioassays and spatially-separated test zones (multi-electrode mode). In this review, the nanotechnological, structural, and technical perspectives in the multiplex analysis of cancer proteins were discussed. Finally, the use of different types of nanomaterials, polysaccharides, biopolymers and their advantages in signal amplification are discussed.

Nanostructures for nonlabeled and labeled electrochemical immunosensors: Simultaneous electrochemical detection of cancer markers: A review

The simultaneous electrochemical determination of multiple tumor antigens has attracted a great deal of attention, which can effectively enhance the capability and accuracy of the analysis. Nanostructured materials mostly played a key major role in the electrochemical immunosensors fabrication and operation improvement. This review focused mainly on the protocols for using nanostructures to fabricate electrochemical (nonlabeled@label-free and labeled@sandwich-type) immunosensors. Furthermore, this review has also described the diverse classes of electroactive nanospecies which are a complementary part of any immunosensor that assists to reach the selectivity for the target antigen. Finally, the important analytical characteristics of the published immunosensors were discussed (electrochemical detection technique, linear range, and detection limit). Studies published between the years 2009-2018 have been included in this review.

Improved screen-printed carbon electrode for multiplexed label-free amperometric immuniosensor: Addressing its conductivity and reproducibility challenges

A new screen-printed carbon electrode (SPCE) with multiple working electrodes and one signal output channel without counter and reference electrodes was designed. The multiple working electrodes can be individually modified for each target of interest. The SPCE contained one signal output channel, making the immuniosensor be realized by common single-channel electrochemical workstation. The counter and reference electrodes were independent of disposable SPCE, reducing costs and eliminating precious metal pollution. Platinum network as counter electrode improved the reproducibility of the SPCE. Moreover, method of generating hydrogel on working electrode was used to enhance the conductivity of SPCE. Based on this, a multiplexed single channel label-free amperometric immuniosensor for four tumor markers, namely, squamous cell carcinoma antigen (SCCA), fragment antigen 21-1 (Cyfra21-1), carbohydrate antigen 125 (CA125), and neuron specific enolase (NSE) was developed, and the corresponding detection limits were 5.5pgmL^-1, 4.8pgmL^-1, 0.0054UmL^-1 and 2.3pgmL^-1, respectively. The sensitivity of this immunosensor was 0.83µA (lg(ngmL^-1))^-1 for SCCA, 1.92µA (lg(ngmL^-1))^-1 for Cyfra21-1, 4.75µA (lg(UmL^-1))^-1 for CA125 and 2.40µA (lg(ngmL^-1))^-1 for NSE. Among them, the sensitivities of CA125 and NSE were four-fold higher than those of the previous works.

A sensitive label-free electrochemical immunosensor for detection of cytokeratin 19 fragment antigen 21-1 based on 3D graphene with gold nanopaticle modified electrode

Previous studies have confirmed that cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) serves as a powerful biomarker in non-small cell lung cancer (NSCLC). Herein, we report for the first time a label-free electrochemical immunosensor for sensitive and selective detection of tumor marker CYFRA21-1. In this work, three-dimensional graphene @ gold nanoparticles (3D-G@Au) nanocomposite was modified on the glassy carbon electrode (GCE) surface to enhance the conductivity of immunosensor. The anti-CYFRA21-1 captured and fixed on the modified GCE through the cross-linking of chitosan (CS), glutaraldehyde (GA) and anti-CYFRA21-1. The differential pulse voltammetry (DPV) peak current change due to the specific interaction between anti-CYFRA21-1 and CYFRA21-1 on the modified electrode surface was utilized to detect CYFRA21-1. Under optimized conditions, the proposed electrochemical immunosensor was employed to detect CYFRA21-1 and exhibited a wide linear range of 0.25-800ngmL^-1 and low detection limit of 100pgmL^-1 (S/N = 3). Moreover, the recovery rates of serum samples were in the range from 95.2% to 108.7% and the developed immunosensor also shows a good correlation (less than 6.6%) with enzyme-linked immunosorbent assay (ELISA) in the detection of clinical serum samples. Therefore, it is expected that the proposed immunosensor based on a 3D-G@Au has great potential in clinical medical diagnosis of CYFRA21-1.

A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO2@PEI nanoparticles for NSE analysis

Poly(ethylenimine) (PEI) and Ru(bpy)3(2+)-doped silica (Ru-SiO2) nanoparticles were simply mixed together to prepare a novel self-enhanced electrochemiluminescence (ECL) composite of Ru-SiO2@PEI. The hollow Ru-SiO2@PEI nanoparticles were used to build an ECL immunosensor for the analysis of neuron specific enolase (NSE). PEI not only assembled on the surface of Ru-SiO2 nanoparticles through the electrostatic interaction to act as co-reactant for Ru(bpy)3(2+) ECL, but also provided alkaline condition to etch the Ru-SiO2 nanoparticles to form the hollow Ru-SiO2@PEI nanoparticles with porous shell. The unique structure of the Ru-SiO2@PEI nanoparticles loaded both a large amount of Ru(bpy)3(2+) and its co-reactant PEI at the same time, which shortened the electron-transfer distance, thereby greatly enhanced the luminous efficiency and amplified the ECL signal. The developed immunosensor showed a wide linear range from 1.0 × 10(-11) to 1.0 × 10(-5) mg mL(-1) with a low detection limit of 1.0 × 10(-11) mg mL(-1) for NSE. When the immunosensor was used for the determination of NSE in clinical human serum, the results were comparable with those obtained by using enzyme-linked immunosorbent assay (ELISA) method. The proposed method provides a promising alternative for NSE analysis in clinical samples.

Novel electrochemical redox-active species: one-step synthesis of polyaniline derivative-Au/Pd and its application for multiplexed immunoassay

Electrochemical redox-active species play crucial role in electrochemically multiplexed immunoassays. A one-pot method for synthesizing four kinds of new electrochemical redox-active species was reported using HAuCl4 and Na2PdCl4 as dual oxidating agents and aniline derivatives as monomers. The synthesized polyaniline derivative-Au/Pd composites, namely poly(N-methyl-o-benzenediamine)-Au/Pd, poly(N-phenyl-o-phenylenediamine)-Au/Pd, poly(N-phenyl-p-phenylenediamine)-Au/Pd and poly(3,3',5,5'-tetramethylbenzidine)-Au/Pd, exhibited electrochemical redox activity at -0.65 V, -0.3 V, 0.12 V, and 0.5 V, respectively. Meanwhile, these composites showed high H2O2 electrocatalytic activity because of the presence of Au/Pd. The as-prepared composites were used as electrochemical immunoprobes in simultaneous detection of four tumor biomarkers (carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA199), carbohydrate antigen 72-4 (CA724), and alpha fetoprotein (AFP)). This immunoassay shed light on potential applications in simultaneous gastric cancer (related biomarkers: CEA, CA199, CA724) and liver cancer diagnosis (related biomarkers: CEA, CA199, AFP). The present strategy to the synthesize redox species could be easily extended to other polymers such as polypyrrole derivatives and polythiophene derivatives. This would be of great significance in the electrochemical detection of more analytes.

Design of immunoprobes for electrochemical multiplexed tumor marker detection

Many approaches have been developed for simultaneous detection of multiple tumor markers. Among these approaches, the electrochemical immunoassay has the advantage of high sensitivity and specificity and could be easily expanded into multiplex detection platform. For the simultaneous multianalyte electrochemical immunosensor, performance is closely related with the characteristics of the immunoprobes and substrate. In order to construct a multilabeled immunoprobe platform, the most important issue is how to discriminate each signal for each analyte from the multiple antigen-antibody reactions. Currently, enzyme-based, noble metal nanomaterials, carbonmaterials and polymer-based nanomaterial immunoprobes have been used for dual- or three-analyte detections. However, there are still some challenges in developing sensitive method to detect three or more tumor markers owing to the lack of redox-active species that can produce three or more distinctive peaks. Additionally, for the immunosensing substrate, good conductivity, high specific surface area and good biocompatibility are further necessities.