Nuclear matrix protein 22 (NMP22) is considered one of the noninvasive biological indications in the urine that has recently captured extensive clinical attention for bladder cancer screening and surveillance. Hence, it is imperative to create a straightforward, sensitive, and precise NMP22 assay. As a type of carbon nanomaterial, carboxylated multiwalled carbon nanotubes (CMWCNTs) exhibit exceptional electrical conductivity and abundant carboxyl groups. The silver nanoparticles and zeolitic imidazolate frameworks-8 composite (AgNPs-ZIF-8), which is a three-dimensional material, possess a wide surface area, acceptable electrical conductivity, and satisfactory biocompatibility. More importantly, it can also immobilize NMP22 antibodies in striking amounts via the Ag–NH2 bonds. Along these lines, in this work, AgNPs were decorated on ZIF-8 and modified on the glassy carbon electrode together with CMWCNTs. The comparative advantages of carbon nanotubes, metal–organic frameworks, and AgNPs were successfully combined to develop an electrochemical immunosensor with superior sensitivity and reliability for the detection of NMP22 in urine. It should be mentioned that the immunosensor not only has a wide linear range (10–2 to 105 pg mL–1) and a low detection limit (8.8 fg mL–1, S/N = 3) but also exhibits robust precision, excellent selectivity, and desirable stability. Aside from that, the immunosensor was effectively utilized to detect human urine samples, demonstrating an excellent performance.
Bladder cancer is a highly prevalent and frequently occurring tumor. Nuclear matrix protein 22 (NMP22) is one of the non-invasive biological indications in the urine that has captured extensive clinical attention recently for bladder cancer screening and surveillance. Nevertheless, at the pre-tumor stage, the universally used clinical immunoassays are unable to identified trace amounts of NMP22 in urine. Hence, it is imperative to create a straightforward, sensitive, and precise NMP22 assay. As a type of carbon nanomaterial, carboxylated multi-walled carbon nanotubes exhibit exceptional electrical conductivity and abundant carboxyl groups. The silver nanoparticles and zeolitic imidazolate frameworks-8 (AgNPs@ZIF-8) composite, which is a three-dimensional material, has a wide surface area, acceptable electrical conductivity, and satisfactory biocompatibility. More importantly, it can also immobilize NMP22 antibodies in striking amounts via Ag-NH2 bonds. The benefits of carbon nanotubes, metal-organic frameworks, and AgNPs were successfully combined to develop an electrochemical immunosensor with superior sensitivity and reliability to detect NMP22 in urine. It deserves to be mentioned that the immunosensor not only has a wide linear range (10-2pg mL-1~105pg mL-1) and a low detection limit (8.8 fg mL-1, S/N = 3), but exhibits robust repeatability, excellent selectivity, and desirable stability. Aside from that, the immunosensor was effectively utilized to detect human urine samples, which showed excellent performance.
Lung cancer is one of the malignant tumors with the highest mortality rate, and the detection of its tumor marker carcinoma antigen 125 (CA125) is significant. Here, an electrochemical immunoassay for CA125 was described. Nitrogen-doped reduced graphene oxide (N-rGO), carboxylated multi-walled carbon nanotubes (CMWCNTs) and gold nanoparticles (AuNPs) were applied to co-modify glassy carbon electrode (GCE), after incubation with Anti-CA125, the modified electrode was employed for the specific detection of CA125. The N-rGO@CMWCNTs (Nitrogen-doped reduced graphene oxide@carboxylated multi-walled carbon nanotubes) were used as a matrix, while CS@AuNPs (Chitosan@gold nanoparticles) with high conductivity and biocompatibility was immobilized on it through the reaction between carboxyl groups from CMWCNTs and amino groups, hydroxyl groups from chitosan (CS), resulting in the effect of double signal amplification. The immunosensor demonstrated excellent electrochemical performance with a linear detection range of 0.1 pg mL−1–100 ng mL−1, and the detection limit was as low as 0.04 pg mL−1 (S/N = 3). It had been verified that this method had good precision and high accuracy, and the immunosensor could remain stable for 10 days. This research provided a new method for the detection of CA125 in serum.
Lead (Pb) and cadmium (Cd) are pervasive environmental pollutants known for their significant biological toxicity. The traditional methods for detecting these ions include flameless atomic absorption spectrophotometry, hydride-generation atomic fluorescence spectrometry, and inductively coupled plasma atomic emission spectrometry. However, these methods often necessitate large-scale instruments and complex procedures. In contrast, electrochemical detection methods offer advantages such as rapidity, portability, and sensitivity, making them suitable for the simultaneous detection of heavy metals. Metal-organic frameworks (MOFs), characterized by their exceptional adsorption and enrichment capabilities for heavy metal ions, have shown promise in this regard. Nevertheless, the poor conductivity of most MOFs has limited their electrochemical applications. In this study, glassy carbon electrodes (GCEs) were modified using the MOF ZIF-8, in combination with a bismuth complex and carboxylated multi-walled carbon nanotubes, resulting in the fabrication of Bi@ZIF-8/CMWCNTs/GCE electrochemical sensors. Under optimized conditions, Pb2+ and Cd2+ showed good linear relationships with the peak current in the concentration range of 2.0-50.0 μg/L. In the concentration range studied, the regression equations for Pb2+ and Cd2+ were determined as follows: y = 0.2982x + 0.4553 (r = 0.9962) for Pb2+ and y = 0.3631x + 0.1242 (r = 0.9949) for Cd2+. The detection limits for Pb2+ and Cd2+ were 0.76 μg/L and 0.87 μg/L, respectively. The relative standard deviations (RSDs) for 50 μg/L mixed standard solution of Pb and Cd were 1.89% and 1.23%, respectively. Furthermore, the RSDs for the same modified electrode tested with 50 μg/L Pb2+ and Cd2+ mixed standard solution over seven consecutive days were 2.27% and 1.42%, respectively, under identical conditions. In practice, the lead and cadmium concentrations of a lake were found to range from 4.42 μg/L to 5.60 μg/L, while the lead and cadmium concentrations of effluent from a wastewater plant ranged from 11.83 μg/L to 14.49 μg/L. This research not only describes a new electrochemical platform for the simultaneous determination of lead and cadmium in water but also provides a new method for the simultaneous determination of lead and cadmium in water. This research is valuable for promoting the application of MOFs in the field of electrochemistry.
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