A sensitive electrochemical immunosensor based on poly(2-aminobenzylamine) film modified screen-printed carbon electrode for label-free detection of human immunoglobulin G

Flower-like WSe2 used as bio-matrix in ultrasensitive label-free electrochemical immunosensor for human immunoglobulin G determination

The abnormal concentrations of human immunoglobulin G (hIgG) refers to many kinds of diseases. Analytical methods with the characteristics of rapid response, easy operation and high sensitivity should be designed to accurately determinate the hIgG levels in human serum. In this work, a label-free electrochemical immunosensor based on WSe₂/rGO was developed to sensitively detect human immunoglobulin G. First, the flower-like transition metal dichalcogenides (TMDCs) Tungsten Diselenide (WSe₂) with large effective specific surface area and porous structure was synthesized by hydrothermal synthesis. As a bio-matrix, the flower-like WSe₂ efficiently increased the active sites for loading antibodies. Meanwhile, reduced graphene oxide (rGO) obtained by tannic acid reduction was used to improve the current response of the sensing interface. WSe₂ was combined with rGO and the electrochemical active surface area (ECSA) of the sensing interface was enlarged to 2.1 times that of GCE. Finally, the combination of flower-like WSe₂ and rGO broadened the detection range and reduced the detection limit of the sensing platform. The immunosensor exhibited a high sensitivity with a wide linear range of 0.01-1000 ng/mL and low detection limit of 4.72 pg/mL. The real sample analysis of hIgG were conducted under optimal conditions, and the spiked recovery rates were between 95.5 and 104.1%. Moreover, satisfactory results were obtained by testing the stability, specificity and reproducibility of the immunosensor. Therefore, it can be concluded that the as-proposed immunosensor has the application potential of clinical analyze of hIgG in human serum.

A sandwich-like configuration with a signal amplification strategy using a methylene blue/aptamer complex on a heterojunction 2D MoSe2/2D WSe2 electrode: Toward a portable and sensitive electrochemical alpha-fetoprotein immunoassay

Liver cancer is one of the most common global health problems that features a high mortality rate. Alpha-fetoprotein (AFP) is a potential liver cancer biomarker for the diagnosis of liver cancer. The quantitative detection of AFP at an ultratrace level has important medical significance. Using the reaction of the antibody-antigen pair in an immunosensor enables the sensitive and selective AFP assay. Finding a strategy in signal generation and amplification is challenging to fabricate new sensitive electrochemical immunosensors for AFP detection. This study demonstrates the construction of a simple, reliable, and label-free immunosensor for the detection of AFP on a smart phone. Exfoliated two-dimensional (2D) molybdenum diselenide (MoSe2) and 2D tungsten diselenide (WSe2) were employed to modify the disposable screen-printed carbon electrode (SPCE) to use as the electrochemical platform, which is affixed to a small potentiostat connected to a smart phone. The modified electrode offers antibody immobilization and allows detection of AFP via an immunocomplex forming a sandwich-like configuration with the AFP-corresponding aptamer. A heterojunction 2D MoSe2/2D WSe2 composite improves the SPCE's reactivity and provides a large surface area and good adsorption capacity for the immobilizing antibodies. The signal generation for the immunosensor is from the electrochemical response of methylene blue (MB) intercalating into the aptamer bound on the electrode. The response for the proposed sandwich-like immunosensor is proportional to the AFP concentration (1.0-50,000 pg ml-1). The biosensor has potential for the development of a simple and robust point-of-care diagnostic platform for the clinical diagnosis of liver cancer, achieving a low limit of detection (0.85 pg ml-1), high sensitivity, high selectivity, good stability, and excellent reproducibility.

Inkjet Printing: A Viable Technology for Biosensor Fabrication

Printing technology promises a viable solution for the low-cost, rapid, flexible, and mass fabrication of biosensors. Among the vast number of printing techniques, screen printing and inkjet printing have been widely adopted for the fabrication of biosensors. Screen printing provides ease of operation and rapid processing; however, it is bound by the effects of viscous inks, high material waste, and the requirement for masks, to name a few. Inkjet printing, on the other hand, is well suited for mass fabrication that takes advantage of computer-aided design software for pattern modifications. Furthermore, being drop-on-demand, it prevents precious material waste and offers high-resolution patterning. To exploit the features of inkjet printing technology, scientists have been keen to use it for the development of biosensors since 1988. A vast number of fully and partially inkjet-printed biosensors have been developed ever since. This study presents a short introduction on the printing technology used for biosensor fabrication in general, and a brief review of the recent reports related to virus, enzymatic, and non-enzymatic biosensor fabrication, via inkjet printing technology in particular.

A gold nanoparticle-dye/poly(3-aminobenzylamine)/two dimensional MoSe2/graphene oxide electrode towards label-free electrochemical biosensor for simultaneous dual-mode detection of cancer antigen 15-3 and microRNA-21

A dual-mode electrochemical biosensor is successfully developed for simultaneous detection of two different kinds of breast cancer biomarkers, namely cancer antigen 15-3 (CA 15-3) and microRNA-21 (miRNA-21), for the first time. The sensor composes of a poly(3-aminobenzylamine)/two-dimensional (2D) molybdenum selenide/graphene oxide nanocomposite modified two-screen-printed carbon electrode array (dual electrode), functionalized individually with 2,3-diaminophenazine-gold nanoparticles and toluidine blue-gold nanoparticles. Both kinds of the redox probe-gold nanoparticles are employed as signaling molecules and supports for immobilization of anti-CA 15-3 antibodies and capture DNA-21 probes, respectively. Due to the good conductivity and high surface-to-volume ratio of the nanocomposite, high amount of the antibodies and capture probes can be immobilized on the modified dual-electrode, giving the efficient duplex detection. Consequently, the biosensor provides good selectivity, and high sensitivity for the dual target analyte detection. The experimental results show that this label-free biosensor exhibits good linear responses to the concentrations of both target analytes with the limits of detection (LODs) of 0.14 U mL^-1 and 1.2 fM for CA 15-3 and miRNA-21, respectively. This assay strategy has a great potential to be further developed for the simultaneous detection of a variety of miRNAs and protein biomarkers for point-of-care (POC) diagnostic applications.

Development of electrochemical biosensors for simultaneous multiplex detection of microRNA for breast cancer screening

A highly sensitive electrochemical biosensors has been developed for the detection of multiplex micro ribonucleic acids (miRNAs) by modifying an electrode with reduced graphene oxide/poly(2-aminobenzylamine)/gold nanoparticles and adopting porous, hollow silver-gold nanoparticles as tagged labeling with metal ions. In addition, an anti-deoxyribonucleic acid (DNA)-RNA hybrid [S9.6] antibody was used to detect different hybridized capture DNAs and miRNAs that can detect multiple miRNAs simultaneously. The developed electrochemical platform exhibits high selectivity, stability, and sensitivity with a wide linear range from 1 fM to 10 nM and a low detection limit of 0.98 fM, 3.58 fM, and 0.25 fM for miRNA-155, miRNA-21, and miRNA-16, respectively. In addition, the proposed electrochemical biosensor capable for the simultaneous detection of miRNA-155, miRNA-16, and miRNA-21, which are breast cancer biomarkers, in normal human serum, can be adopted and potentially used for breast cancer screening.

A Redox Cu(II)-Graphene Oxide Modified Screen Printed Carbon Electrode as a Cost-Effective and Versatile Sensing Platform for Electrochemical Label-Free Immunosensor and Non-enzymatic Glucose Sensor

A novel copper (II) ions [Cu(II)]-graphene oxide (GO) nanocomplex-modified screen-printed carbon electrode (SPCE) is successfully developed as a versatile electrochemical platform for construction of sensors without an additionally external redox probe. A simple strategy to prepare the redox GO-modified SPCE is described. Such redox GO based on adsorbed Cu(II) is prepared by incubation of GO-modified SPCE in the Cu(II) solution. This work demonstrates the fabrications of two kinds of electrochemical sensors, i.e., a new label-free electrochemical immunosensor and non-enzymatic sensor for detections of immunoglobulin G (IgG) and glucose, respectively. Our immunosensor based on square-wave voltammetry (SWV) of the redox GO-modified electrode shows the linearity in a dynamic range of 1.0-500 pg.mL-1 with a limit of detection (LOD) of 0.20 pg.mL-1 for the detection of IgG while non-enzymatic sensor reveals two dynamic ranges of 0.10-1.00 mM (sensitivity = 36.31 μA.mM-1.cm-2) and 1.00-12.50 mM (sensitivity = 3.85 μA.mM-1.cm-2) with a LOD value of 0.12 mM. The novel redox Cu(II)-GO composite electrode is a promising candidate for clinical research and diagnosis.

A Bifunctional Nanosilver-Reduced Graphene Oxide Nanocomposite for Label-Free Electrochemical Immunosensing

A bi-functional material based on silver nanoparticles (AgNPs)-reduced graphene oxide (rGO) composite for both electrode modification and signal generation is successfully synthesized for use in the construction of a label-free electrochemical immunosensor. An AgNPs/rGO nanocomposite is prepared by a one-pot wet chemical process. The AgNPs/rGO composite dispersion is simply cast on a screen-printed carbon electrode (SPCE) to fabricate the electrochemical immunosensor. It possesses a sufficient conductivity/electroreactivity and improves the electrode reactivity of SPCE. Moreover, the material can generate an analytical response due to the formation of immunocomplexes for detection of human immunoglobulin G (IgG), a model biomarker. Based on electrochemical stripping of AgNPs, the material reveals signal amplification without external redox molecules/probes. Under optimized conditions, the square wave voltammetric peak current is responded to the logarithm of IgG concentration in two wide linear ranges from 1 to 50 pg.ml-1 and 0.05 to 50 ng.ml-1, and the limit of detection (LOD) is estimated to be 0.86 pg.ml-1. The proposed immunosensor displays satisfactory sensitivity and selectivity. Importantly, detection of IgG in human serum using the immunosensor shows satisfactory accuracy, suggesting that the immunosensor possesses a huge potential for further development in clinical diagnosis.

A novel site-induced biomolecule anchoring strategy based on solid superacid ZrO2/SO42- for fabricating label-free IgG electrochemical immunosensors

In this work, a unique zirconium dioxide solid superacid (ZrO₂/SO₄²⁻) was utilized for the fabrication of an IgG electrochemical immunosensor.