Ultrasensitive electrochemical biosensor based on reduced graphene oxide-tetraethylene pentamine-BMIMPF6 hybrids for the detection of α2,6-sialylated glycans in human serum

Non-enzymatic electrochemical sensor based on ionic liquid [BMIM][PF6] functionalized zirconium‑copper bimetallic MOF composite for the detection of nitrite in food samples

In this study, we developed an electrochemical sensor utilizing a composite material consisting of zirconium‑copper bimetallic metal-organic framework functionalized with ionic liquid [BMIM][PF6]. This composite material was fabricated by simple wet impregnation method, which not only maintains excellent electrocatalytic activity but also enhances electron transfer rate and electroactive surface area. The ZrCu-MOF-818/ILs composite modified electrode has been demonstrated as an effective tool for the detection of nitrite. The electrode exhibited a remarkable limit of detection (LOD) of 0.148 μM and wide linear ranges of 6-3000 μM and 3000-5030 μM. It is worth noting that the sensor displayed excellent reproducibility and repeatability, with relative standard deviation (RSD) values of 1.06% and 1.37%, respectively. Furthermore, the proposed method was successfully applied for the detection of nitrite in tap water and pickle juice.

Glycan-Based Electrochemical Biosensors: Promising Tools for the Detection of Infectious Diseases and Cancer Biomarkers

Glycan-based electrochemical biosensors are emerging as analytical tools for determining multiple molecular targets relevant to diagnosing infectious diseases and detecting cancer biomarkers. These biosensors allow for the detection of target analytes at ultra-low concentrations, which is mandatory for early disease diagnosis. Nanostructure-decorated platforms have been demonstrated to enhance the analytical performance of electrochemical biosensors. In addition, glycans anchored to electrode platforms as bioreceptors exhibit high specificity toward biomarker detection. Both attributes offer a synergy that allows ultrasensitive detection of molecular targets of clinical interest. In this context, we review recent advances in electrochemical glycobiosensors for detecting infectious diseases and cancer biomarkers focused on colorectal cancer. We also describe general aspects of structural glycobiology, definitions, and classification of electrochemical biosensors and discuss relevant works on electrochemical glycobiosensors in the last ten years. Finally, we summarize the advances in electrochemical glycobiosensors and comment on some challenges and limitations needed to advance toward real clinical applications of these devices.

Systematic review on lectin-based electrochemical biosensors for clinically relevant carbohydrates and glycoconjugates

Carbohydrates and glycoconjugates are involved in numerous natural and pathological metabolic processes, and the precise elucidation of their biochemical functions has been supported by smart technologies assembled with lectins, i.e., ubiquitous proteins of nonimmune origin with carbohydrate-specific domains. When lectins are anchored on suitable electrochemical transducers, sensitive and innovative bioanalytical tools (lectin-based biosensors) are produced, with the ability to screen target sugars at molecular levels. In addition to the remarkable electroanalytical sensitivity, these devices associate specificity, precision, stability, besides the possibility of miniaturization and portability, which are special features required for real-time and point-of-care measurements. The mentioned attributes can be improved by combining lectins with biocompatible 0-3D semiconductors derived from carbon, metal nanoparticles, polymers and their nanocomposites, or employing labeled biomolecules. This systematic review aims to substantiate and update information on the progress made with lectin-based biosensors designed for electroanalysis of clinically relevant carbohydrates and glycoconjugates (glycoproteins, pathogens and cancer biomarkers), highlighting their main detection principles and performance in highly complex biological milieus. Moreover, particular emphasis is given to the main advantages and limitations of the reported devices, as well as the new trends for the current demands. We believe that this review will support and encourage more cutting-edge research involving lectin-based electrochemical biosensors.

Au@BSA microspheres-luminol and a novel luminescent Zeolitic Imidazolate Framework were used for potential-resolved electrochemiluminescence to detect dual targets

Here, a novel electrochemiluminescence biosensor based on potential-resolved strategy was firstly prepared for the detection of dual targets α2,3-sialylated glycans and α2,6-sialylated glycans. This is the first time that Au@BSA microsphere was used to connect with luminol to enhance its ECL intensity, and it can generate ECL signals at positive potential. Zeolitic Imidazolate Framework-8 (ZIF-8) and Meso-tetra (4-carboxyphenyl) porphyrin (TCPP) were linked using a one-pot method to synthesize a novel luminescent ZIF (L-ZIF) named TZZ, which can emit ECL signals at negative potential. Moreover, magnetite microspheres were used to construct a sandwich-type biosensor to obtain higher sensitivity and reduce background signals. In addition, the biosensor manufactured directly in solution have a wider linear range than constructed on electrode because it has more available space than the electrode surface. Due to the above advantages, the prepared ECL biosensor exhibited high sensitivity, stability and broader linear range, even for practical analysis. Therefore, the prepared ECL biosensor will become a promising method for determination of α2,3-sialylated glycans and α2,6-sialylated glycans in clinical applications in the future. What is more, it provides a potential method for detection of other multi-targets.

Dual-type responsive electrochemical biosensor for the detection of α2,6-sialylated glycans based on AuNRs-SA coupled with c-SWCNHs/S-PtNC nanocomposites signal amplification

In this study, a dual-type responsive electrochemical biosensor was developed for the quantitative detection of α2,6-sialylated glycans (α2,6-sial-Gs), a potential biomarker of tumors. The gold nanorods (AuNRs), which exhibited great specific surface area, as well as good biocompatibility, was synthesized by the way of seed growth method. Furthermore, a biotin-streptavidin (biotin-SA) system was introduced to improve the immunoreaction efficiency. Accordingly, a label-free biosensor was fabricated based on AuNRs-SA for the quick detection of α2,6-sial-Gs by recording the signal of differential pulse voltammetry (DPV). Furthermore, to expand the ultrasensitive detection of α2,6-sial-Gs, a carboxylated single-walled carbon nanohorns/sulfur-doped platinum nanocluster (c-SWCNHs/S-PtNC) was synthesized for the first time as a novel signal label, which showed an excellent catalytic performance. The usage of c-SWCNHs/S-PtNC could significantly amplify the electrochemical signal recorded by the amperometric i-t curve. Herein, a sandwich type biosensor was constructed by combining the AuNRs-SA on the electrode and c-SWCNHs/S-PtNC (signal amplifier). The label-free biosensor possessed a linear range from 5 ng mL^-1 to 5 μg mL^-1 with a detection limit of 0.50 ng mL^-1, and the sandwich-type biosensor possessed a wide linear range from 1 fg mL^-1 to 100 ng mL^-1 with a detection limit of 0.69 fg mL^-1. Furthermore, the biosensor exhibited excellent recovery and stability, indicating its potential for use in actual samples.

Nanotechnology in Glycomics: Applications in Diagnostics, Therapy, Imaging, and Separation Processes

This review comprehensively covers the most recent achievements (from 2013) in the successful integration of nanomaterials in the field of glycomics. The first part of the paper addresses the beneficial properties of nanomaterials for the construction of biosensors, bioanalytical devices, and protocols for the detection of various analytes, including viruses and whole cells, together with their key characteristics. The second part of the review focuses on the application of nanomaterials integrated with glycans for various biomedical applications, that is, vaccines against viral and bacterial infections and cancer cells, as therapeutic agents, for in vivo imaging and nuclear magnetic resonance imaging, and for selective drug delivery. The final part of the review describes various ways in which glycan enrichment can be effectively done using nanomaterials, molecularly imprinted polymers with polymer thickness controlled at the nanoscale, with a subsequent analysis of glycans by mass spectrometry. A short section describing an active glycoprofiling by microengines (microrockets) is covered as well.

Versatile aptasensor for electrochemical quantification of cell surface glycan and naked-eye tracking glycolytic inhibition in living cells

Quantifying the glycan expression status on cell surfaces is of vital importance for insight into the glycan function in biological processes and related diseases. Here we developed a versatile aptasensor for electrochemical quantification of cell surface glycan by taking advantage of the cell-specific aptamer, and the lectin-functionalized gold nanoparticles acting as both a glycan recognition unit and a signal amplification probe. To construct the aptasensor, amine-functionalized mucin 1 protein (MUC1) aptamer was first covalently conjugated to carboxylated-magnetic beads (MBs) using the succinimide coupling (EDC-NHS) method. On the basis of the specific recognition between aptamer and MUC1 protein that overexpressed on the surface of MCF-7 cells, the aptamer conjugated MBs showed a predominant capability for cell capture with high selectivity. Moreover, a lectin-based nanoprobe was designed by noncovalent assembly of concanavalin A (ConA) on gold nanoparticles (AuNPs). This nanoprobe incorporated the abilities of both the specific carbohydrate recognition and the signal amplification based on the gold-promoted reduction of silver ions. By coupling with electrochemical stripping analysis, the proposed sandwich-type cytosensor showed an excellent analytical performance for the ultrasensitive detection of MCF-7 cells and quantification of cell surface glycan. More importantly, taking advantage of Con A-gold nanoprobe catalyzed silver enhancement, the proposed method was further used for naked-eye tracking glycolytic inhibition in living cells. This aptasensor holds great promise as a new point-of-care diagnostic tool for analyzing glycan expression on living cells and further helps cancer diagnosis and treatment.

A new strategy for label-free electrochemical immunoassay based on "gate-effect" of β-cyclodextrin modified electrode

A novel label-free electrochemical immunoassay was developed for prostate-specific antigen (PSA) detection via using β-cyclodextrin (β-CD) assembled layer created gates for the electron transfer of probe. To construct the sensor, a gold electrode was self-assembled with monoclonal anti-PSA antibody labeled 6-mercapto-β-cyclodextrin. Interspaces among β-CD molecules in the layer were automatically formed on gold electrode, which act as the channel of the electron transfer of [Fe(CN)6](3-/4-) probe. When PSA bind with anti-PSA, it can block these channels on the electrode surface due to their steric hindrance effect, resulting in the decrease in redox current of the probe. Through such a gate-controlled effect, ultra trace amount of PSA may make the currents change greatly after the immunoreaction, which enhanced the signal-to-noise ratio to achieve the amplification effect. By evaluating the logarithm of PSA concentrations, the immunosensor had a good linear response to the current changes with a detection limit of 0.3 pg/mL (S/N = 3) when PSA concentration ranged from 1.0 pg/mL to 1.0 ng/mL. The label-free immunosensor exhibited satisfactory performances in sensitivity, repeatability as well as specificity.

Multi-purpose electrochemical biosensor based on a “green” homobifunctional cross-linker coupled with PAMAM dendrimer grafted p-MWCNTs as a platform: application to detect α2,3-sialylated glycans and α2,6-sialylated glycans in human serum

Sialylated glycans are crucial molecular targets for cancer diagnosis and clinical research.