Novel Immunoprobe Based on MOF-818 Synergizing with an Antifouling Sensing Interface to Improve Immunosensors

Abstract

Sensitivity and accuracy are both of great significance for immunosensors in practical application; thus, it is an effective strategy to improve the performance of immunosensors from the above two aspects. Herein, we reported a multifunctional immunoprobe based on metal−organic framework 818 (MOF-818) that possessed dual catalytic activity to enhance the sensitivity of immunosensors. In the presence of dopamine and hydrogen peroxide, MOF-818 can accelerate the oxidative polymerization of dopamine to couple biomolecules and facilitate the formation of semiquinone radicals and hydroxyl radicals. The obtained hydroxyl radicals promoted oxidation of the electrochemical signal molecule thionine and then realized cascade amplification of current change. To achieve high precision detection, a gold-electroplated glassy carbon electrode was assembled with an antifouling material (difunctional polyethylene glycol (HS-PEG-NH 2 )) to form a hydration layer, which was exploited to increase hydrophilicity and minimize non-specific adsorption. Carbohydrate antigen 72-4 (CA72-4) was chosen as a target analyte to examine the performance of immunosensors with a lower limit of detection with 26.48 nU mL −1 and a linear range from 1 μU mL −1 to 10 U mL −1 . The method possessed a promising prospect in practical application due to its remarkable performance in human serum detection.

Anti-Fouling Strategies of Electrochemical Sensors for Tumor Markers

“…The strong hydrophilicity of PEG was utilized to form a dense hydration layer, which effectively reduced the adsorption of non-specific proteins on the electrode surface and achieved the expected anti-fouling effect. The results showed that when human serum epididymal protein 4 (HE-4), human immunoglobulin (IgG), carcinoma antigen 125 (CA12-5), and neuron-specific enolase (NSE) were selected as interferences, the corresponding currents produced were negligible [46]. The fabrication process of the electrochemical immunosensor is shown in Figure 1.…”

“…In most cases, the method used to reduce non-specific adsorption involves applying anti-fouling materials directly onto the electrode's surface. These materials include PEG and its derivatives [44][45][46][47][48][49], zwitterionic polymers [41,[50][51][52], peptides [53][54][55][56][57], and hydrogels [58][59][60][61], among others [62][63][64]. A new method has been developed in recent years, whereby the immunorecognition and signal readout platforms are separated, and the anti-fouling material is used to modify magnetic beads instead of the electrode's surface, resulting in good conductivity of the electrode [65][66][67][68][69][70][71][72].…”

“…The fabrication process of the electrochemical immunosensor based on MOF-818 synergizing with an anti-fouling sensing interface. Reprinted with permission from Ref [46],. Copyright @ 2022, American Chemical Society.…”

Universal and High-Speed Zeptomolar Protein Serum Assay with Unprecedented Sensitivity

“…In the case of proteins, EC assays can analyze samples with target concentrations 5−6 orders of magnitude lower than traditional ELISA. 22,23 However, most existing EC methods are still unable to accurately detect trace amounts of protein. They also face the challenges of multistep handling and biofouling at the electrode interface, which results in nonspecific high background noise and risk of false positives.…”

“…EC assays provide a powerful and promising tool for the development of sensitive detection of proteins due to their rapidity, robustness, sensitivity, cost-effectiveness, and environmental insensitivity toward electroactive labels. − With the impressive sensitivity demonstrated so far, they have the potential to replace ELISA in certain applications, especially those involving point-of-care testing and in vitro diagnosis. In the case of proteins, EC assays can analyze samples with target concentrations 5–6 orders of magnitude lower than traditional ELISA. , However, most existing EC methods are still unable to accurately detect trace amounts of protein. They also face the challenges of multistep handling and biofouling at the electrode interface, which results in nonspecific high background noise and risk of false positives.…”