Cancer immunosensor based on apo and holo transferrin binding

An electrochemical fluorescence dual-mode strategy for HER2-positive breast cancer cell detection

Breast cancer is one of the most prevalent malignancies worldwide, with HER2-overexpressing subtypes exhibiting increased aggressiveness and poorer prognosis. Accurate identification of HER2-positive subtypes is essential for the effective implementation of HER2-targeted therapy. In this study, an electrochemical fluorescence dual-mode strategy was developed for the high sensitive detection of HER2-positive breast cancer cells. Immunofluorescent quantum dot probes (IFQDs) with both fluorescence and enzyme catalysis were constructed. It labelled HER2 sites on the cell membrane to enable fluorescent imaging and cell counting. Furthermore, alkaline phosphatase (ALP) on the probe surface catalyzed the reduction of silver on the surface of the Au NPs@ITO electrode through enzyme-induced metallization, thereby enabling quantitative detection of the cells via stripping voltammetry. The application of two methods, namely enzyme-induced metallization and enrichment of signal species on the electrode surface, significantly enhanced the sensitivity of this analytical strategy. The self-monitoring of dual signals achieved more accurate analytical performance. The dual-mode strategy demonstrated satisfactory results in identifying breast cancer cells with varying HER2 expression levels and even in complex samples. It indicated that the electrochemical fluorescence dual-mode strategy had potential for typing and quantitative detection of cells with varying HER2 expression levels.

Advanced electrocatalytic materials based biosensors for cancer cell detection – A review

Herein, we have highlighted the latest developments on biosensors for cancer cell detection. Electrochemical (EC) biosensors offer several advantages such as high sensitivity, selectivity, rapid analysis, portability, low‐cost, etc. Generally, biosensors could be classified into other basic categories such as immunosensors, aptasensors, cytosensors, electrochemiluminescence (ECL), and photo‐electrochemical (PEC) sensors. The significance of the EC biosensors is that they could detect several biomolecules in human body including cholesterol, glucose, lactate, uric acid, DNA, blood ketones, hemoglobin, and others. Recently, various EC biosensors have been developed by using electrocatalytic materials such as silver sulfide (Ag2S), black phosphene (BPene), hexagonal carbon nitrogen tube (HCNT), carbon dots (CDs)/cobalt oxy‐hydroxide (CoOOH), cuprous oxide (Cu2O), polymer dots (PDs), manganese oxide (MnO2), graphene derivatives, and gold nanoparticles (Au‐NPs). In some cases, these newly developed biosensors could be able to detect cancer cells with a limit of detection (LOD) of 1 cell/mL. In addition, many remaining challenges have to be addressed and validated by testing more real samples and confirm that these EC biosensors are more accurate and reliable to measure cancer cells in the blood and salivary samples.

Clinically Deployable Bioelectronic Sensing Platform for Ultrasensitive Detection of Transferrin in Serum Sample

Varying levels of transferrin (Tf) have been associated with different disease conditions and are known to play a crucial role in various malignancies. Regular monitoring of the variations in Tf levels can be useful for managing related diseases, especially for the prognosis of certain cancers. We fabricated an immunosensor based on graphene oxide (GO) nanosheets to indirectly detect Tf levels in cancer patients. The GO nanosheets were deposited onto an indium tin oxide (ITO)-coated glass substrate and annealed at 120 °C to obtain reduced GO (rGO) films, followed by the immobilization of an antibody, anti-Tf. The materials and sensor probe used were systematically characterized by UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were also used for the stepwise sensor probe characterizations and Tf detection in serum samples, respectively. The anti-Tf/rGO/ITO immunosensor DPV output demonstrated an excellent Tf detection capability in the linear range of 0.1 mg mL^-1 to 12 mg mL^-1 compared to the enzyme-linked immunosorbent assay (ELISA) detection range, with a limit of detection (LOD) of 0.010 ± 0.007 mg mL^-1. Furthermore, the results of the fabricated immunosensor were compared with those of the ELISA and autobioanalyzer techniques, showing an outstanding match with < 5% error and demonstrating the immunosensor's clinical potential.

A novel sandwich impedimetric immunosensor for detection of apolipoprotein-A1 based on the gold nanoparticle-hybridized mercapto-β-cyclodextrin-Pb(II) metal-organic framework

A novel sandwich electrochemical impedimetric immunosensor was proposed to detect apolipoprotein-A1 (Apo-A1), a common biomarker for bladder cancer. The molybdenum disulfide/graphene quantum dot (MoS₂/GQD) nanocomposites were modified on the surface of a glassy carbon electrode (GCE) and used to immobilize the biotinylated antibody (Ab₁) with the help of chitosan and glutaraldehyde (denoted as BSA/Ab₁/CHIT/MoS₂/GQD/GCE). Pb(II)-thiol-β-cyclodextrin metal-organic framework (denoted as Pb-MOF) was synthesized with lead metal ions and thiol-β-cyclodextrin ligands by a one-pot solvothermal method, and then, gold nanoparticles were modified on the surface of Pb-MOF (Pb-MOF-AuNPs) by Au-S bond, which was used as signal label for the recombinant antibody (Ab₂). When the immunosensor of BSA/Ab₁/CHIT/MoS₂/GQD/GCE reacted with Apo-A1, Pb-MOF-AuNPs-Ab₂/BSA was connected to the electrode when immunoreaction occurred, and an immune sandwich structure was formed, which led to significantly increased charge transfer resistance of electrochemical probe for ferrocyanide (II)/(III) within the frequency range 10^-1 ~ 10⁵ Hz at 5 mV amplitude and the potential of 0.180 V (vs. SCE). Based on this principle, the quantitative detection of Apo-A1 was established. The relative change of electrochemical resistance and the logarithmic value of Apo-A1 concentration showed a linear relationship with a linear coefficient of 0.9989 in the range 1.00 pg mL^-1 and 1.00 μg mL^-1 with the limit of detection of 0.30 pg mL^-1. The selectivity, repeatability, and other performance of the proposed immunosensor were also investigated. The immunosensor was successfully applied to the detection of real serum and urine samples with recovery in the range 96.4 ~ 109.1% (RSD < 3.8%), indicating that it could be helpful for the clinical diagnosis of bladder cancer.

A review of electrochemical impedance spectroscopy for bioanalytical sensors

Electrochemical impedance spectroscopy (EIS) is a powerful technique for both quantitative and qualitative analysis. This review uses a systematic approach to examine how electrodes are tailored for use in EIS-based applications, describing the chemistries involved in sensor design, and discusses trends in the use of bio-based and non-bio-based electrodes. The review finds that immunosensors are the most prevalent sensor strategy that employs EIS as a quantification technique for target species. The review also finds that bio-based electrodes, though capable of detecting small molecules, are most applicable for the detection of complex molecules. Non-bio-based sensors are more often employed for simpler molecules and less often have applications for complex systems. We surmise that EIS has advanced in terms of electrode designs since our last review on the subject, although there are still inconsistencies in terms of equivalent circuit modelling for some sensor types. Removal of ambiguity from equivalent circuit models may help advance EIS as a choice detection method, allowing for lower limits of detection than traditional electrochemical methods such as voltammetry or amperometry.

Ultrasensitive electrochemical detection of CYFRA 21-1 via in-situ initiated ROP signal amplification strategy

The cytokeratin19 fragment (CYFRA 21-1) is an essential biomarker for non-small cell lung cancer (NSCLC). This work proposed a novel electrochemical immunosensor with a high selective and sensitive detection of CYFRA 21-1via the ring-opening polymerization (ROP) signal amplification strategy. Specifically, 3-mercaptopropionic (MPA) was employed as a cross-linking agent to immobilize cAb on the electrode surface for subsequent specific capture of CYFRA 21-1. After CYFRA 21-1 bound to cAb, the amino groups of them were blocked with acrolein. Then, the sandwich-type compositions were formed via the specific recognition between detection antibody (dAb) and CYFRA 21-1. Finally, the ROP was triggered by the amino group on dAb and the polymers containing a large number of ferrocene electroactive molecules were in situ grown on the electrode surface, thereby outputting a high sensing signal. Under optimal conditions, the fabricated immunosensor showed an ultrasensitive and highly selective with a linear range of 1 pg/mL ∼1 μg/mL, and the detection limit down to 9.08 fg/mL. Furthermore, a bright correlation was obtained for CYFRA 21-1 detection in the clinical serum samples. By merits of its ease of operation, environmental friendliness and low cost, this method had considerable potential application in bioanalytical for the ultrasensitive quantitation of biological molecules.

Electrochemical Sensors for Detection of Markers on Tumor Cells

In recent years, the increasing incidence and mortality of cancer have inspired the development of accurate and rapid early diagnosis methods in order to successfully cure cancer; however, conventional methods used for detecting tumor cells, including histopathological and immunological methods, often involve complex operation processes, high analytical costs, and high false positive rates, in addition to requiring experienced personnel. With the rapid emergence of sensing techniques, electrochemical cytosensors have attracted wide attention in the field of tumor cell detection because of their advantages, such as their high sensitivity, simple equipment, and low cost. These cytosensors are not only able to differentiate tumor cells from normal cells, but can also allow targeted protein detection of tumor cells. In this review, the research achievements of various electrochemical cytosensors for tumor cell detection reported in the past five years are reviewed, including the structures, detection ranges, and detection limits of the cytosensors. Certain trends and prospects related to the electrochemical cytosensors are also discussed.