An electrochemical immunosensor for an alpha-fetoprotein cancer biomarker on a carbon black/palladium hybrid nanoparticles platform

The early detection of cancer is a key step in cancer survival. Thus, there is a need to develop low-cost technologies, such as electrochemical immunosensor technologies, for timely screening and diagnostics. The discovery of alpha-feto protein (AFP) as a tumour-associated antigen lends AFP as a biomarker for cancer detection and monitoring. Thus, immunosensors can be developed to target AFP in cancer diagnostics. Hence, we report the application of a hybrid nanocomposite of carbon black nanoparticles (CBNPs) and palladium nanoparticles (PdNPs) as a platform for the electrochemical immunosensing of cancer biomarkers. The hybrid carbon-metal nanomaterials were immobilised by using the drop-drying and electrodeposition technique on a glassy carbon electrode, followed by the immobilisation of the anti-AFP to fabricate an immunosensor. The nanoparticles were characterised with electron microscopy, voltammetry, and electrochemical impedance spectroscopy (EIS). Square wave voltammetry (SWV) and EIS were used to study the immunosensor signal toward the bio-recognition of the AFP cancer biomarker. The hybrid nanoparticles enhanced the immunosensor performance. A linear detection range from 0.005 to 1000 ng mL^-1 with low detection limits of 0.0039 ng mL^-1 and 0.0131 ng mL^-1 were calculated for SWV and EIS, respectively. The immunosensor demonstrated good stability, reproducibility, and selectivity. Its real-life application potential was tested with detection in human serum matrix.

Unique Electron-Transfer-Mediated Electrochemiluminescence of AuPt Bimetallic Nanoclusters and the Application in Cancer Immunoassay

Noble Metal nanoclusters (NCs) are promising electrochemiluminescence (ECL) emitters due to their amazing optical properties and excellent biocompatibility. They have been widely used in the detection of ions, pollutant molecules, biomolecules, etc. Herein, we found that glutathione-capped AuPt bimetallic NCs (GSH-AuPt NCs) emitted strong anodic ECL signals with triethylamine as co-reactants which had no fluorescence (FL) response. Due to the synergistic effect of bimetallic structures, the ECL signals of AuPt NCs were 6.8 and 94 times higher than those of monometallic Au and Pt NCs, respectively. The electric and optical properties of GSH-AuPt NCs differed from those of Au and Pt NCs completely. An electron-transfer mediated ECL mechanism was proposed. The excited electrons may be neutralized by Pt(II) in GSH-Pt and GSH-AuPt NCs, resulting in the vanished FL. Furthermore, abundant TEA radicals formed on the anode contributed electrons to the highest unoccupied molecular orbital of GSH-Au_2.5Pt NCs and Pt(II), booming intense ECL signals. Because of the ligand effect and ensemble effect, bimetallic AuPt NCs exhibited much stronger ECL than GSH-Au NCs. A sandwich-type immunoassay for alpha fetoprotein (AFP) cancer biomarkers was fabricated with GSH-AuPt NCs as signal tags, which displayed a wide linear range from 0.01 to 1000 ng·mL^-1 and a limit of detection (LOD) down to 1.0 pg·mL^-1 at 3S/N. Compared to previous ECL AFP immunoassays, this method not only had a wider linear range but also a lower LOD. The recoveries of AFP in human serum were around 108%, providing a wonderful strategy for fast, sensitive, and accurate cancer diagnosis.

Electrochemical and Photoelectrochemical Immunosensors for the Detection of Ovarian Cancer Biomarkers

Photoelectrochemical (PEC) sensing is an emerging technological innovation for monitoring small substances/molecules in biological or non-biological systems. In particular, there has been a surge of interest in developing PEC devices for determining molecules of clinical significance. This is especially the case for molecules that are markers for serious and deadly medical conditions. The increased interest in PEC sensors to monitor such biomarkers can be attributed to the many apparent advantages of the PEC system, including an enhanced measurable signal, high potential for miniaturization, rapid testing, and low cost, amongst others. The growing number of published research reports on the subject calls for a comprehensive review of the various findings. This article is a review of studies on electrochemical (EC) and PEC sensors for ovarian cancer biomarkers in the last seven years (2016-2022). EC sensors were included because PEC is an improved EC; and a comparison of both systems has, expectedly, been carried out in many studies. Specific attention was given to the different markers of ovarian cancer and the EC/PEC sensing platforms developed for their detection/quantification. Relevant articles were sourced from the following databases: Scopus, PubMed Central, Web of Science, Science Direct, Academic Search Complete, EBSCO, CORE, Directory of open Access Journals (DOAJ), Public Library of Science (PLOS), BioMed Central (BMC), Semantic Scholar, Research Gate, SciELO, Wiley Online Library, Elsevier and SpringerLink.

Dual-mode electrochemiluminescence and electrochemical sensor for alpha-fetoprotein detection in human serum based on vertically ordered mesoporous silica films

In this study, we demonstrated the highly sensitive detection of alpha-fetoprotein (AFP) by electrochemiluminescence (ECL) and electrochemistry (EC) based on the gated transport of the bifunctional probe (tris(1,10-phenanthroline) ruthenium (II) chloride, Ru (phen)₃Cl₂) into the nanochannels of vertically ordered mesoporous silica films (VMSFs). Due to the negatively charged surface and ultrasmall pore size, VMSF displays a signal amplification effect on Ru (phen)₃Cl₂ and is suitable for the construction of sensors with excellent sensitivity. With the linkage of (3-glycidyloxypropyl) trimethoxysilane, the anti-AFP antibody could covalently bind to the external surface of VMSF, generating a highly specific recognized sensing interface toward AFP. When AFP is presented, the formed immunocomplex hinders the diffusion of Ru (phen)₃Cl₂ to the underlying electrode surface, resulting in a decreased ECL or EC response. The dual-mode detection of AFP is achieved with a relatively low limit of detection (0.56 fg/ml for ECL and 4.5 pg/ml for EC) and a wide linear range (10 fg/ml∼1 μg/ml for ECL and 10 pg/ml∼1 μg/ml for EC). Moreover, owing to the inherent anti-fouling property of VMSF, satisfactory results in the analysis of human serum were obtained, showing the great potential of the designed strategy in clinical diagnosis.

Two-Dimensional Graphitic Carbon Nitride (g-C3N4) Nanosheets and Their Derivatives for Diagnosis and Detection Applications

The early diagnosis of certain fatal diseases is vital for preventing severe consequences and contributes to a more effective treatment. Despite numerous conventional methods to realize this goal, employing nanobiosensors is a novel approach that provides a fast and precise detection. Recently, nanomaterials have been widely applied as biosensors with distinctive features. Graphite phase carbon nitride (g-C3N4) is a two-dimensional (2D) carbon-based nanostructure that has received attention in biosensing. Biocompatibility, biodegradability, semiconductivity, high photoluminescence yield, low-cost synthesis, easy production process, antimicrobial activity, and high stability are prominent properties that have rendered g-C3N4 a promising candidate to be used in electrochemical, optical, and other kinds of biosensors. This review presents the g-C3N4 unique features, synthesis methods, and g-C3N4-based nanomaterials. In addition, recent relevant studies on using g-C3N4 in biosensors in regard to improving treatment pathways are reviewed.

Gold nanostar-enhanced electrochemiluminescence immunosensor for highly sensitive detection of cancer stem cells using CD133 membrane biomarker

Gold nanostars (AuNSs) demonstrate an intense electromagnetic field around tip of branches. In this research, we employed AuNSs-enhanced electrochemiluminescence (ECL) emission from graphitic carbon nitride nanosheets (g-CN nanosheets) to detect CD133 peptide as a cancer stem cell membrane biomarker. In this biosensor, the g-CN nanosheets were decorated with AuNSs (AuNSs@g-CN nanosheets). AuNSs@g-CN nanosheets exhibited strong and stable cathodic ECL emission compared to that of pure g-CN nanosheets. The ECL intensity from the AuNSs@g-CN nanosheets was over 30% higher than that of spherical gold nanoparticles (spherical AuNPs) decorated g-CN nanosheets. The additional ECL enhancement of AuNSs was due to the localized surface plasmon resonance (LSPR) effect located around multiple branch tips of AuNSs. The RSD of ECL curves intensities, obtained from successive potential scans for 10 cycles, were less than 4%, indicating the superior stability of the AuNSs@g-CN nanosheets. Under optimum conditions, the ECL intensity of GCE/AuNSs@g-CN nanosheets/anti-CD133 decreased linearly with CD133 peptide concentration in the range of 0.05-100 ng mL^-1. The LOD achieved was 0.257 ng mL^-1 (S/N = 3). The applicability of the designed biosensor in real samples was examined through the determination of CD133 peptide in spiked serum samples, from which satisfactory results were obtained.

Electrogenerated chemiluminescence resonance energy transfer between ZnGa2O4/g-C3N4 and gold nanoparticles/graphene and its application in the detection of thrombin

A label-free ECL sensor for thrombin was fabricated based on ECL resonance energy transfer occurred between ZnGa₂O₄/g-C₃N₄ and AuNP/GR nanocomposites, which revealed a new role of spinel-type semiconductor oxides in the fabrication of ECL sensors.

Electrochemical Sensing of α-Fetoprotein Based on Molecularly Imprinted Polymerized Ionic Liquid Film on a Gold Nanoparticle Modified Electrode Surface

A molecularly imprinted sensor was fabricated for alpha-fetoprotein (AFP) using an ionic liquid as a functional monomer. Ionic liquid possesses many excellent characteristics which can improve the sensing performances of the imprinted electrochemical sensor. To demonstrate this purpose, 1-[3-(N-cystamine)propyl]-3-vinylimidazolium tetrafluoroborate ionic liquid [(Cys)VIMBF₄] was synthesized and used as a functional monomer to fabricate an AFP imprinted polymerized ionic liquid film on a gold nanoparticle modified glassy carbon electrode (GCE) surface at room temperature. After removing the AFP template, a molecularly imprinted electrochemical sensor was successfully prepared. The molecularly imprinted sensor exhibits excellent selectivity towards AFP, and can be used for sensitive determination of AFP. Under the optimized conditions, the imprinted sensor shows a good linear response to AFP in the concentration range of 0.03 ng mL⁻¹~5 ng mL⁻¹. The detection limit is estimated to be 2 pg mL⁻¹.

An ultrasensitive electrochemical immunosensor based on the synergistic effect of quaternary Cu2SnZnS4 NCs and cyclodextrin-functionalized graphene

Cu₂ZnSnS₄ nanocrystals were first used as electrocatalysts for H₂O₂ reduction for the ultrasensitive detection of alpha-fetoprotein.

A review of electrogenerated chemiluminescent biosensors for assays in biological matrices

Electrogenerated chemiluminescence (ECL) is the production of light via electron transfer reactions between electrochemically produced reagents. ECL-based biosensors use specific biological interactions to recognize an analyte and produce a luminescent signal. Biosensors fabricated with novel biorecognition species have increased the number of analytes detected. Some of these analytes include peptides, cells, enzymes and nucleic acids. ECL biosensors are selective, simple, sensitive and have low detection limits. Traditional methods use ruthenium complexes or luminol to generate ECL. Nanomaterials can be incorporated into ECL biosensors to improve efficiency, but also represent a new class of ECL emitters. This article reviews the application of ruthenium complex, luminol and nanomaterial-based ECL biosensors to making measurements in biological matrices over the past 4 years.