Construction of Electrochemical Immunosensing Interface for Multiple Cancer Biomarkers Detection

Simultaneous detection of multiple neuroendocrine tumor markers in patient serum with an ultrasensitive and antifouling electrochemical immunosensor

Neuroendocrine tumors (NETs) are rare heterogeneous tumors that are often misdiagnosed and mistreated. Most NETs patients are diagnosed as advanced. Early on-time detection of NETs is significant for precision therapy. Here, an ultrasensitive and antifouling label-free electrochemical immunosensor was constructed for simultaneous analysis of NETs biomarkers chromogranin A (CgA) and chromogranin B (CgB). The metal ion functionalized porous magnesium silicate/gold nanoparticles/polyethylene glycol/chitosan (PMS-M²⁺/AuNPs/PEG/CS) composites were employed as the sensing platforms. By combining PEG and CS with good hydrophilicity, the sensing interface exhibited outstanding antifouling ability in complex biological systems. PMS with high surface area and the porous structure can efficiently load Cu²⁺ and Pb²⁺, which could directly generate independent electrochemical peak currents that reflected the concentrations of CgA and CgB. Under optimal conditions, this immunosensor can detect CgA and CgB with good linearity from 0.1 pg mL^-1 to 100 ng mL^-1 as low as 5.3 and 2.1 fg mL^-1, respectively. Moreover, this immunosensor can accurately detect CgA and CgB levels in clinical serum, which were well consistent with the enzyme-linked immunosorbent assay (ELISA). This strategy provided a sensitive, simple and low-cost platform for clinical screening and point-of-care diagnosis of NETs.

Photothermal-Induced Electrochemical Interfacial Region Regulation Enables Signal Amplification for Dual-Mode Detection of Ovarian Cancer Biomarkers

Detection sensitivity of an electrochemical immunosensor mainly depends on the accessible distance toward the sensing interface; regulating the electrochemical interfacial region thereon is an effective strategy for signal amplification. Herein, a photothermal-regulated sensing interface was designed based on a near-infrared (NIR)-responsive hydrogel probe for ultrasensitive detection of human epididymis protein 4 (HE4). Silver nanoparticle-deposited graphene oxide nanosheet (AgNPs@GO) hybrids as electrochemical signal tags and a photothermal transducer, which were encapsulated in the poly(N-isopropylacrylamide) (pNIPAM) hydrogel, were used to develop the NIR-responsive GO@AgNPs-pNIPAM hydrogel probe. Under NIR light irradiation, the excellent photothermal effect of AgNPs@GO hybrids not only rapidly converted NIR light into heat for temperature readout but also triggered the shrinkage behavior of the hydrogel for electrochemical signal amplification. Compared with the conventional sandwich immunoassay, the shrinkage behavior of the hydrogel signal probe endowed itself with interface regulation capability to improve the electrochemical reaction efficiency; on the basis of ensuring the extended outer Helmholtz plane (OHP) region, the proposed photothermal-induced interface regulation also shortened the OHP, leading to higher sensitivity. Moreover, the obtained dual-mode signals provided satisfactory accuracy for the detection of tumor markers. Therefore, this detection scheme provided an opportunity for the broad applications of the photothermal effect in clinical diagnosis.

Ca2+-Triggered pH-Response Sodium Alginate Hydrogel Precipitation for Amplified Sandwich-Type Impedimetric Immunosensor of Tumor Marker

Signal amplification is of great significance in the ultrasensitive electrochemical impedimetric immunoassays for tumor marker detection. A cascaded signal amplification approach was designed using gold nanoparticle-CaCO₃ microspheres (AuNP-CaCO₃) to trigger pH-responsive alginate hydrogel precipitation for sandwich-type impedimetric immunosensor. AuNP-CaCO₃ exerts a large hindrance effect and can release Ca²⁺ ions under weak acidic conditions, and thus can serve as a multifunctional label. The hindrance effect of AuNP-CaCO₃ can significantly enhance the impedance response as the initial signal amplification. Then, part of CaCO₃ dissolves under weak acid conditions and releases Ca²⁺, which can cross-link with alginate to generate an insoluble alginate hydrogel precipitate on the sensing interface, significantly increasing the impedance signal. The impedance signal can be further amplified by making the hydrogel negatively charged based on the pH-responsive surface charge properties of the alginate hydrogel. Benefiting from the cascaded signal amplification, this impedimetric immunosensor exhibits a linear range from 1.0 fg mL^-1 to 100 ng mL^-1, an detection limit of 0.09 fg mL^-1, and ultrahigh sensitivity of 973.01 Ω (lg(ng mL^-1))^-1 toward the assay of prostate specific antigen (PSA).

Ultrasensitive profiling of multiple biomarkers from single cells by signal amplification mass spectrometry

A signal amplification protocol based on mass spectrometry (MS) was developed to profile simultaneously multiple biomarkers from a single cell using various mass label (ML)-modified Au nanoparticles (AuNPs). The strategy with ultrahigh sensitivity and specificity has potential prospects in the deep exploration of molecular and cellular characterization.

Recent Advances in Enhancement Strategies for Electrochemical ELISA-Based Immunoassays for Cancer Biomarker Detection

Electrochemical enzyme-linked immunosorbent assay (ELISA)-based immunoassays for cancer biomarker detection have recently attracted much interest owing to their higher sensitivity, amplification of signal, ease of handling, potential for automation and combination with miniaturized analytical systems, low cost and comparative simplicity for mass production. Their developments have considerably improved the sensitivity required for detection of low concentrations of cancer biomarkers present in bodily fluids in the early stages of the disease. Recently, various attempts have been made in their development and several methods and processes have been described for their development, amplification strategies and testing. The present review mainly focuses on the development of ELISA-based electrochemical immunosensors that may be utilized for cancer diagnosis, prognosis and therapy monitoring. Various fabrication methods and signal enhancement strategies utilized during the last few years for the development of ELISA-based electrochemical immunosensors are described.