A voltammetric immunosensor based on nanobiocomposite materials for the determination of alpha-fetoprotein in serum

Laser-Induced Electrochemical Biosensor Modified with Graphene-Based Ink for Label-Free Detection of Alpha-Fetoprotein and 17β-Estradiol

In this research, a novel electrochemical biosensor is proposed based on inducing graphene formation on polyimide substrate via laser engraving. Graphene polyaniline (G-PANI) conductive ink was synthesized by planetary mixing and applied to the working zone of the developed sensor to effectively enhance the electrical signals. The laser-induced graphene (LIG) sensor was used to detect alpha-fetoprotein (AFP) and 17β-Estradiol (E2) in the phosphate buffer saline (PBS) buffer and human serum. The electrochemical performance of the biosensor in determining these biomarkers was investigated by differential pulse voltammetry (DPV) and chronoamperometry (CA). In a buffer environment, alpha-fetoprotein (AFP) and 17β-Estradiol detection range were 4-400 ng/mL and 20-400 pg/mL respectively. The experimental results showed a limit of detection (LOD) of 1.15 ng/mL and 0.96 pg/mL for AFP and estrogen, respectively, with an excellent linear range (R2 = 0.98 and 0.99). In addition, the designed sensor was able to detect these two types of biomarkers in human serum successfully. The proposed sensor exhibited excellent reproducibility, repeatability, and good stability (relative standard deviation, RSD = 0.96%, 1.12%, 2.92%, respectively). The electrochemical biosensor proposed herein is easy to prepare and can be successfully used for low-cost, rapid detection of AFP and E2. This approach provides a promising platform for clinical detection and is advantageous to healthcare applications.

Evaluation of a Voltametric E-Tongue Combined with Data Preprocessing for Fast and Effective Machine Learning-Based Classification of Tomato Purées by Cultivar

The potential of a voltametric E-tongue coupled with a custom data pre-processing stage to improve the performance of machine learning techniques for rapid discrimination of tomato purées between cultivars of different economic value has been investigated. To this aim, a sensor array with screen-printed carbon electrodes modified with gold nanoparticles (GNP), copper nanoparticles (CNP) and bulk gold subsequently modified with poly(3,4-ethylenedioxythiophene) (PEDOT), was developed to acquire data to be transformed by a custom pre-processing pipeline and then processed by a set of commonly used classifiers. The GNP and CNP-modified electrodes, selected based on their sensitivity to soluble monosaccharides, demonstrated good ability in discriminating samples of different cultivars. Among the different data analysis methods tested, Linear Discriminant Analysis (LDA) proved to be particularly suitable, obtaining an average F1 score of 99.26%. The pre-processing stage was beneficial in reducing the number of input features, decreasing the computational cost, i.e., the number of computing operations to be performed, of the entire method and aiding future cost-efficient hardware implementation. These findings proved that coupling the multi-sensing platform featuring properly modified sensors with the custom pre-processing method developed and LDA provided an optimal tradeoff between analytical problem solving and reliable chemical information, as well as accuracy and computational complexity. These results can be preliminary to the design of hardware solutions that could be embedded into low-cost portable devices.

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.

Electrochemical α-fetoprotein immunosensor based on Fe3O4NPs@covalent organic framework decorated gold nanoparticles and magnetic nanoparticles including SiO2@TiO2

The early diagnosis of major diseases such as cancer is typically a major issue for humanity. Human α-fetoprotein (AFP) as a sialylated glycoprotein is of approximately 68 kD molecular weight and is considered to be a key biomarker, and an increase in its level indicates the presence of liver, testicular, or gastric cancer. In this study, an electrochemical AFP immunosensor based on Fe₃O₄NPs@covalent organic framework decorated gold nanoparticles (Fe₃O₄ NPs@COF/AuNPs) for the electrode platform and double-coated magnetic nanoparticles (MNPs) based on SiO₂@TiO₂ (MNPs@SiO₂@TiO₂) nanocomposites for the signal amplification was fabricated. The immobilization of anti-AFP capture antibody was successfully performed on Fe₃O₄ NPs@COF/AuNPs modified electrode surface by amino-gold affinity, while the conjugation of anti-AFP secondary antibody on MNPs@SiO₂@TiO₂ was achieved by the electrostatic/ionic interactions. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) analysis, cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) techniques were used to characterize the nanostructures in terms of physical and electrochemical features. The limit of detection (LOD) was 3.30 fg mL^-1. The findings revealed that the proposed electrochemical AFP immunosensor can be effectively used to diagnose cancer.

Gold Nanowires Array-Based Closed Bipolar Nanoelectrode System for Electrochemiluminescence Detection of α-Fetoprotein on Cell Surface

Inspired by the promising applications of a closed bipolar electrodes (c-BPEs) system in electrochemiluminescence (ECL) detection of cell adhesion and disease-related biomarkers, here, a gold nanowires array-based c-BPEs system was constructed for cell surface protein detection. Regular and uniform gold nanowires array were prepared by intermittent potentiostatic deposition. Then, two poly(dimethylsiloxane) (PDMS) chips with a hole diameter of 2 mm as a reservoir were placed at both sides of Au nanowires array to construct c-BPEs system. Thionine-functionalized silicon dioxide nanoparticles conjugated to antibody (Ab2-Th@SiO₂) were used as the electrochemical probe, while [Ru(bpy)₃]²⁺-wrapped SiO₂ nanoparticles (Ru(II)@SiO₂) were employed as the ECL signal readout. Taking α-fetoprotein (AFP) as model, the gold nanowires array-based c-BPEs system allowed sensitive detection of AFP at a linear range from 0.002 to 50.0 ng/mL and at least 6 living cells ascribing to the synergetic amplification effect at both sensing and reporting chambers. Besides, the amount of AFP expressed by HepG2 cells was calculated to be 6.71 pg/cell. The presented strategy with high sensitivity provided a promising and universal platform for the detection of other cancer cells and disease-related biomarkers (such as proteins, glycan, miRNA).

A dual-signal self-checking photoelectrochemical immunosensor based on the sole composite of MIL-101(Cr) and CdSe quantum dots for the detection of α-fetoprotein

Designing a photoelectrochemical (PEC) immunosensor that can produce dual photocurrent signals which can refer to each other is a great importance but a big challenge. In this manuscript, a novel dual photocurrent signals immunosensor was constructed for the detection of α-fetoprotein (AFP). Unlike the usual method of using two composite materials to provide cathode and anode photocurrent respectively, this work applies only one compound of MIL-101 (Cr) and CdSe quantum dots (QDs). Thereinto, we found that the photocurrent polarity of MIL-101(Cr) would switch by adjusting applied voltage. And then CdSe QDs was introduced by simple ultrasound mixing to boost the dual photocurrent signals. Furthermore, in the composite of M&C, the electron transfer path between MIL-101(Cr) and CdSe QDs may switch between "Z-type" and "Ⅱ-type" by adjusting voltage. Benefiting by the dual signals, the proposed sensor can not only perform sensitively quantitative detection of α-fetoprotein (AFP), but also can intuitively estimate the accuracy and reliability of the test result by determining whether the corresponding relationship of "cathode photocurrent-analyte concentration-anode photocurrent" is established. The linear ranges of the sensing electrodes as cathode and anode are the same, both from 0.1 to 300 ng mL^-1. The limit of detection (LOD) is 0.082 ng mL^-1 (S/N = 3) when it used as an anode, and the LOD is 0.054 ng mL^-1 (S/N = 3) when it served as cathode. Furthermore, this sensor showed acceptable stability, reproducibility, specificity, and feasibility of detecting AFP in human serum, which has broad development prospects in the early clinical diagnosis.

Gold Microstructures/Polyaniline/Reduced Graphene Oxide/Prussian Blue Composite as Stable Redox Matrix for Label-free Electrochemical Immunoassay of α-Fetoprotein

Sensitivity amplification strategies in label-free electrochemical immunosensors are mainly limited by redox molecules leaking and degradation of electrical conductivity caused by layers of decoration. Herein, a relatively stable and sensitive label-free electrochemical immunosensor based on a hierarchically flower-like gold microstructures/polyaniline/reduced graphene oxide/prussian blue (HFG/PANI/rGO/PB) composite modified electrode was stepwise fabricated for determination of α-fetoprotein (AFP). In this process, the effect of PANI and rGO on the proposed immunosensor was studied. In detail, PANI/rGO due to the unique electrochemical properties can effectively prevent PB leakage and form a stable sensing platform, which causes sensitive responsiveness and thus a more satisfied detection limit. Meanwhile, the HFG with good biological compatibility can effectively immobilize plenty of antibodies. Under optimal conditions, the HFG/PANI/rGO/PB modified immunosensor exhibited an excellent linearity (0.01 - 30 ng/mL) and a low detection limit (0.003 ng/mL) (S/N = 3), suitable specificity as well as stability and reproducibility towards AFP. The present work offered a promising platform for clinical hepatocellular carcinoma diagnostics.

Selection and characterization of a novel affibody peptide and its application in a two-site ELISA for the detection of cancer biomarker alpha-fetoprotein

Alpha-fetoprotein (AFP) is one of the most important biomarkers associated with primary liver cancer, and the main approaches for diagnosis are based on immunoassay. Affibody is a 58 amino acids peptide derived from the Z domain of staphylococcal protein A and generally applied in imaging diagnosis, clinical therapeutics and biotechnology research. The aim of this study was therefore to develop a novel affibody-based ELISA for detection of AFP. After three rounds of biopanning, six AFP-binding affibody peptides were selected using phage display technology, among them affibody Z_AFPD2 showed high and specific binding affinity to AFP. An affibody dimer of Z_AFPD2 was created, named (Z_{AFP D2})₂, expressed in E.coli and the purified (Z_{AFP D2})₂ recombinant protein showed higher binding affinity to AFP, as well as high thermal stability. A novel affibody-based two-site ELISA method using Z_AFPD2 or (Z_{AFP D2})₂ and polyclonal antibody to detect AFP was developed, the detection limit of the immunoassay using (Z_{AFP D2})₂ was 2 ng mL^-1 that was 4 times lower than Z_AFPD2, which meets the requirements for practical application. Therefore, this concept of affibody-based ELISA may provide a new method for the detection of various cancer biomarkers.

Gold nanoparticles decorated reduced graphene oxide nanolabel for voltammetric immunosensing

This study describes the development and testing of a simple and novel enzyme-free nanolabel for the detection and signal amplification in a sandwich immunoassay. Gold nanoparticles decorated reduced graphene oxide (rGOAu) was used as the nanolabel for the quantitative detection of human immunoglobulin G (HIgG). The rGOAu nanolabel was synthesised by one pot chemical reduction of graphene oxide and chloroauric acid using sodium borohydride. The pseudo-peroxidase behaviour of rGOAu makes the nanolabel unique from other existing labels. The immunosensing platform was fabricated using self-assembled monolayers of 11-mercaptoundecanoic acid (11-MUDA) on a gold disc electrode. The covalent immobilisation of antibody was achieved through the bonding of the carboxyl group of 11-MUDA and the amino group of the antibody using chemical linkers [1-ethyl-3-(3-dimethylaminopropyl)carbodiimide] and N-hydroxysuccinimide. The fabricated immunosensor exhibited a linear range that included HIgG concentrations of 62.5-500 ng ml^-1. The sensor was also used for the testing of HIgG in the blood sample.

Recent Progress in Nanomaterial-Based Electrochemical Biosensors for Cancer Biomarkers: A Review

This article reviews recent progress in the development of nanomaterial-based electrochemical biosensors for cancer biomarkers. Because of their high electrical conductivity, high affinity to biomolecules, and high surface area-to-weight ratios, nanomaterials, including metal nanoparticles, carbon nanotubes, and graphene, have been used for fabricating electrochemical biosensors. Electrodes are often coated with nanomaterials to increase the effective surface area of the electrodes and immobilize a large number of biomolecules such as enzymes and antibodies. Alternatively, nanomaterials are used as signaling labels for increasing the output signals of cancer biomarker sensors, in which nanomaterials are conjugated with secondary antibodies and redox compounds. According to this strategy, a variety of biosensors have been developed for detecting cancer biomarkers. Recent studies show that using nanomaterials is highly advantageous in preparing high-performance biosensors for detecting lower levels of cancer biomarkers. This review focuses mainly on the protocols for using nanomaterials to construct cancer biomarker sensors and the performance characteristics of the sensors. Recent trends in the development of cancer biomarker sensors are discussed according to the nanomaterials used.

Simple and signal-off electrochemiluminescence immunosensor for alpha fetoprotein based on gold nanoparticle-modified graphite-like carbon nitride nanosheet nanohybrids

A simple, signal-off electrochemiluminescence immunosensor for sensitive and selective detection of alpha fetoprotein was developed based on gold nanoparticle modified graphite-like carbon nitride nanosheet nanohybrids.

An optionality further amplification of an sandwich-type electrochemical immunosensor based on biotin–streptavidin–biotin strategy for detection of alpha fetoprotein

An optionality further amplification of sandwich-type electrochemical immunosensor based on biotin–streptavidin–biotin strategy.

Wire-in-Tube IrOx Architectures: Alternative Label-Free Immunosensor for Amperometric Immunoassay toward α-Fetoprotein

A sensitive, label-free immunosensor based on iridium oxide (IrOx, 0≤x≤2) nanofibers, which were synthesized through a simple one-spinneret electrospinning method, was first developed for immunoassay of the cancer biomarker α-fetoprotein (AFP). The specific wire-in-tube nanostructure could be obtained and the composition of IrOx nanofibers also could be controlled through changing the annealing temperature. The unique structure and properties of IrOx nanofibers obtained at 500 °C not only led to increased electrode surface area and accelerated electron transfer kinetics but also could provide a highly stable matrix for the convenient conjugation of biomolecules together with chitosan (CS). The good electrochemical properties of the IrOx-nanofiber-modified immunosensor allowed one to detect AFP over a wide concentration range from 0.05 to 150 ng/mL, with a detection limit of 20 pg/mL. The proposed immunosensor also has been used to determine AFP in human serum with satisfactory results. The present protocol was shown to be quite promising for clinical screening of cancer biomarkers and point-of-care diagnostics applications.

A sensitive label-free amperometric immunosensor for alpha-fetoprotein based on gold nanorods with different aspect ratio

A simple and accurate label-free amperometric immunosensor for α-fetoprotein (AFP) detection is developed based on gold nanorods (GNRs) with different aspect ratio and compared with gold particles (GNPs). The positively charged GNRs and GNPs due to the surface immobilized cetyltrimethyl ammonium bromide (CTAB) can adsorb the negatively charged AFP antibody (Ab) directly. The presence of the GNRs not only enhanced the immobilized amount of biomolecules, but also improved the electrochemical properties of the immunosensor. With the aid of GNRs, the electrochemical signal was greatly enhanced in comparison with GNPs. Under optimal conditions, the proposed immunosensor could detect AFP in a linear range from 0.1 to 200 ng/mL with a detection limit of 0.04 ng/mL (signal-to-noise ratio = 3), and it also possessed good reproducibility and storage stability. Moreover, the detection of AFP in five human serum samples also showed satisfactory accuracy. The proposed methodology was potentially attractive for clinical immunoassay.

Post-genomics nanotechnology is gaining momentum: nanoproteomics and applications in life sciences

The post-genomics era has brought about new Omics biotechnologies, such as proteomics and metabolomics, as well as their novel applications to personal genomics and the quantified self. These advances are now also catalyzing other and newer post-genomics innovations, leading to convergences between Omics and nanotechnology. In this work, we systematically contextualize and exemplify an emerging strand of post-genomics life sciences, namely, nanoproteomics and its applications in health and integrative biological systems. Nanotechnology has been utilized as a complementary component to revolutionize proteomics through different kinds of nanotechnology applications, including nanoporous structures, functionalized nanoparticles, quantum dots, and polymeric nanostructures. Those applications, though still in their infancy, have led to several highly sensitive diagnostics and new methods of drug delivery and targeted therapy for clinical use. The present article differs from previous analyses of nanoproteomics in that it offers an in-depth and comparative evaluation of the attendant biotechnology portfolio and their applications as seen through the lens of post-genomics life sciences and biomedicine. These include: (1) immunosensors for inflammatory, pathogenic, and autoimmune markers for infectious and autoimmune diseases, (2) amplified immunoassays for detection of cancer biomarkers, and (3) methods for targeted therapy and automatically adjusted drug delivery such as in experimental stroke and brain injury studies. As nanoproteomics becomes available both to the clinician at the bedside and the citizens who are increasingly interested in access to novel post-genomics diagnostics through initiatives such as the quantified self, we anticipate further breakthroughs in personalized and targeted medicine.

New competitive dendrimer-based and highly selective immunosensor for determination of atrazine in environmental, feed and food samples: the importance of antibody selectivity for discrimination among related triazinic metabolites

A new voltammetric competitive immunosensor selective for atrazine, based on the immobilization of a conjugate atrazine-bovine serum albumine on a nanostructured gold substrate previously functionalized with poliamidoaminic dendrimers, was realized, characterized, and validated in different real samples of environmental and food concern. Response of the sensor was reliable, highly selective and suitable for the detection and quantification of atrazine at trace levels in complex matrices such as territorial waters, corn-cultivated soils, corn-containing poultry and bovine feeds and corn flakes for human use. Selectivity studies were focused on desethylatrazine, the principal metabolite generated by long-term microbiological degradation of atrazine, terbutylazine-2-hydroxy and simazine as potential interferents. The response of the developed immunosensor for atrazine was explored over the 10(-2)-10(3) ng mL(-1) range. Good sensitivity was proved, as limit of detection and limit of quantitation of 1.2 and 5 ng mL(-1), respectively, were estimated for atrazine. RSD values <5% over the entire explored range attested a good precision of the device.

Label-free immunosensor based on Pd nanoplates for amperometric immunoassay of alpha-fetoprotein

In this paper, Pd nanoplates were used as a kind of electrode materials for fabrication of an electrochemical immunosensor, which was applied for detection of cancer biomarker alpha-fetoprotein (AFP). Thanks to the unique structure and properties of Pd nanoplates, the antibody of AFP (Ab) was effectively immobilized onto the surface of the Pd nanoplates modified glassy carbon electrode (GCE). Moreover, the good electrochemical properties of Pd nanoplates greatly improved the electronic transmission rate and enhanced the electrochemical signal, which led to an increase of the detection sensitivity. Based on the specific antibody-antigen interaction, a label-free immunosensor based on Pd nanoplates was developed for sensing of AFP. The current method allows us to detect AFP over a wide concentration range from 0.01 to 75.0 ng/mL with a detection limit of 4 pg/mL. The proposed immunosensor has been used to determine AFP in human serum with satisfactory results.

Dual-signal amplification strategy for ultrasensitive photoelectrochemical immunosensing of α-fetoprotein

An ultrasensitive photoelectrochemical immunoassay of cancer biomarker α-fetoprotein (AFP) is proposed that uses titanium dioxide (TiO(2)) coupled with AFP-CdTe-GOx bioconjugate, which featured AFP antigen and glucose oxidase (GOx) labels linked to CdTe quantum dots (QDs) for signal amplification. The synthesized CdTe QDs yielded a homogeneous and narrow size distribution, which allowed the binding of AFP and GOx on CdTe QDs. Greatly enhanced sensitivity for AFP came from a dual signal amplification strategy. First, an effective matching of energy levels between the conduction bands of CdTe QDs and TiO(2) allowed for fast electron injection from excited CdTe QDs to TiO(2) upon irradiation, which reduced the recombination process of electron-hole pairs and prompted photoelectrochemical performance. Second, GOx enzyme could catalyze glucose to produce H(2)O(2), which acted as a sacrificial electron donor to scavenge the photogenerated holes in the valence band of CdTe QDs, further causing an enhanced photocurrent. Thus, on the basis of the dual signal amplification strategy, the competitive immunosensor based on the specific binding of anti-AFP antibodies to AFP and AFP-CdTe-GOx bioconjugates was achieved. This proposed biosensor for AFP possessed largely increased linear detection range from 0.5 pg/mL to 10 μg/mL with a detection limit of 0.13 pg/mL. The proposed amplification strategy shows high sensitivity, stability, and reproducibility and can become a promising platform for other protein detection.