Overview on the Design of Magnetically Assisted Electrochemical Biosensors

Overview on the Development of Electrochemical Immunosensors by the Signal Amplification of Enzyme- or Nanozyme-Based Catalysis Plus Redox Cycling

Enzyme-linked electrochemical immunosensors have attracted considerable attention for the sensitive and selective detection of various targets in clinical diagnosis, food quality control, and environmental analysis. In order to improve the performances of conventional immunoassays, significant efforts have been made to couple enzyme-linked or nanozyme-based catalysis and redox cycling for signal amplification. The current review summarizes the recent advances in the development of enzyme- or nanozyme-based electrochemical immunosensors with redox cycling for signal amplification. The special features of redox cycling reactions and their synergistic functions in signal amplification are discussed. Additionally, the current challenges and future directions of enzyme- or nanozyme-based electrochemical immunosensors with redox cycling are addressed.

Recent Advances in Metallic Nanostructures-assisted Biosensors for Medical Diagnosis and Therapy

The field of nanotechnology has witnessed remarkable progress in recent years, particularly in its application to medical diagnosis and therapy. Metallic nanostructures-assisted biosensors have emerged as a powerful and versatile platform, offering unprecedented opportunities for sensitive, specific, and minimally invasive diagnostic techniques, as well as innovative therapeutic interventions. These biosensors exploit the molecular interactions occurring between biomolecules, such as antibodies, enzymes, aptamers, or nucleic acids, and metallic surfaces to induce observable alterations in multiple physical attributes, encompassing electrical, optical, colorimetric, and electrochemical signals. These interactions yield measurable data concerning the existence and concentration of particular biomolecules. The inherent characteristics of metal nanostructures, such as conductivity, plasmon resonance, and catalytic activity, serve to amplify both sensitivity and specificity in these biosensors. This review provides an in-depth exploration of the latest advancements in metallic nanostructures-assisted biosensors, highlighting their transformative impact on medical science and envisioning their potential in shaping the future of personalized healthcare.

Biorecognition element-free electrochemical detection of recombinant glycoproteins using metal-organic frameworks as signal tags

Accurate and sensitive determination of recombinant glycoproteins is in great demand for the treatment of anemia-induced chronic kidney disease and the illegal use of doping agents in sports. In this study, an antibody and enzyme-free electrochemical method for the detection of recombinant glycoproteins was proposed via the sequential chemical recognition of hexahistidine (His₆) tag and glycan residue on the target protein under the cooperation interaction of nitrilotriacetic acid (NTA)-Ni²⁺complex and boronic acid, respectively. Specifically, NTA-Ni²⁺ complex-modified magnetic beads (MBs-NTA-Ni²⁺) are employed to selectively capture the recombinant glycoprotein through the coordination interaction between His₆ tag and NTA-Ni²⁺ complex. Then, boronic acid-modified Cu-based metal-organic frameworks (Cu-MOFs) were recruited by glycans on the glycoprotein via the formation of reversible boronate ester bonds. MOFs with abundant Cu²⁺ ions acted as efficient electroactive labels to directly produce amplified electrochemical signals. By using recombinant human erythropoietin as a model analyte, this method showed a wide linear detection range from 0.01 to 50 ng/mL and a low detection limit of 5.3 pg/mL. With the benefits from the simple operation and low cost, the stepwise chemical recognition-based method shows great promise in the determination of recombinant glycoproteins in the fields of biopharmaceutical research, anti-doping analysis and clinical diagnosis.

Progress in Electrochemical Immunosensors with Alkaline Phosphatase as the Signal Label

Electrochemical immunosensors have shown great potential in clinical diagnosis, food safety, environmental protection, and other fields. The feasible and innovative combination of enzyme catalysis and other signal-amplified elements has yielded exciting progress in the development of electrochemical immunosensors. Alkaline phosphatase (ALP) is one of the most popularly used enzyme reporters in bioassays. It has been widely utilized to design electrochemical immunosensors owing to its significant advantages (e.g., high catalytic activity, high turnover number, and excellent substrate specificity). In this work, we summarized the achievements of electrochemical immunosensors with ALP as the signal reporter. We mainly focused on detection principles and signal amplification strategies and briefly discussed the challenges regarding how to further improve the performance of ALP-based immunoassays.

Fabrication of a Novel and Ultrasensitive Label-Free Electrochemical Aptasensor Based on Gold Nanostructure for Detection of Homocysteine

The current attempt was made to detect the amino acid homocysteine (HMC) using an electrochemical aptasensor. A high-specificity HMC aptamer was used to fabricate an Au nanostructured/carbon paste electrode (Au-NS/CPE). HMC at high blood concentration (hyperhomocysteinemia) can be associated with endothelial cell damage leading to blood vessel inflammation, thereby possibly resulting in atherogenesis leading to ischemic damage. Our proposed protocol was to selectively immobilize the aptamer on the gate electrode with a high affinity to the HMC. The absence of a clear alteration in the current due to common interferants (methionine (Met) and cysteine (Cys)) indicated the high specificity of the sensor. The aptasensor was successful in sensing HMC ranging between 0.1 and 30 μM, with a narrow limit of detection (LOD) as low as 0.03 μM.