Rapid quantitative detection of capsaicinoids in serum based on an electrochemical immunosensor with a dual-signal amplification strategy

A new ratiometric molecularly imprinted electrochemical sensor for the detection of Sunset Yellow based on gold nanoparticles

Since a high dosage or excessive intake of Sunset Yellow (SY) may pose a threat to human health, it is in great demand to construct an effective method to detect and control SY. Based on the molecularly imprinted polymers (MIPs) and dual-signal output mode, a ratiometric molecularly imprinted electrochemical sensor (RMIECs) was developed for sensitive detection of SY. AuNPs not only provided a large specific surface area to enhance the electron transfer rate but also served as a reference signal (S1), together with SY signal (S2), to produce dual signals. For a proof-of-application study, RMIECs was applied to detect SY with a wide linear range from 10 nM to 100 μM and a low detection limit (LOD) of 1.60 nM (S/N = 3, n = 3). Besides, the method was applied in spiked food samples with recoveries of 94.0 ∼ 97.0 % as well as relative errors of 5.4 ∼ 8.3 %, revealing its promising potential in detection of SY.

Recent Advances in Electrochemical Immunosensors with Nanomaterial Assistance for Signal Amplification

Electrochemical immunosensors have attracted immense attention due to the ease of mass electrode production and the high compatibility of the miniature electric reader, which is beneficial for developing point-of-care diagnostic devices. Electrochemical immunosensors can be divided into label-free and label-based sensing strategies equipped with potentiometric, amperometric, voltammetric, or impedimetric detectors. Emerging nanomaterials are frequently used on electrochemical immunosensors as a highly rough and conductive interface of the electrodes or on nanocarriers of immobilizing capture antibodies, electroactive mediators, or catalyzers. Adopting nanomaterials can increase immunosensor characteristics with lower detection limits and better sensitivity. Recent research has shown innovative immobilization procedures of nanomaterials which meet the requirements of different electrochemical immunosensors. This review discusses the past five years of advances in nanomaterials (metal nanoparticles, metal nanostructures, carbon nanotubes, and graphene) integrated into the electrochemical immunosensor. Furthermore, the new tendency and endeavors of nanomaterial-based electrochemical immunosensors are discussed.

A simple and rapid homogeneous fluorescence polarization immunoassay for rapid identification of gutter cooking oil by detecting capsaicinoids

In order to address the widespread concerns with food safety such as adulteration and forgery in the edible oil field, this study developed a fluorescence polarization immunoassay (FPIA) based on a monoclonal antibody in a homogeneous solution system for determination of capsaicinoids in gutter cooking oil by using chemically stable capsaicinoids as an adulteration marker. The prepared fluoresceinthiocarbamyl ethylenediamine (EDF) was coupled with capsaicinoid hapten C, and the synthesized tracer was purified by thin-layer chromatography (TLC) and showed good binding to the monoclonal antibody CPC Ab-D8. The effects of concentration of tracer and recognition components, type and pH of buffer and incubation time on the performance of FPIA were studied. The linear range (IC₂₀ to IC₈₀) was 3.97-97.99 ng/mL, and the half maximal inhibitory concentration (IC₅₀) was 19.73 ng/mL, and the limit of detection (LOD) was 1.56 ng/mL. The recovery rates of corn germ oil, soybean oil and peanut blend oil were in the range of 94.7-132.3%. The experimental results showed that the fluorescence polarization detection system could realize the rapid detection of capsaicinoids, and had the potential to realize on-site identification of gutter cooking oil. As a universal monoclonal antibody, CPC Ab-D8 can also specifically identify capsaicin and dihydrocapsaicin, so the proposed method can be used to quickly monitor for the presence of gutter cooking oil in normal cooking oil.

Highly Sensitive Capsaicin Electrochemical Sensor Based on Bimetallic Metal-Organic Framework Nanocage

The content of capsaicin can be used as exotic markers of kitchen recycled oil. In this study, a bimetallic MOF nanocage (Fe^III-HMOF-5) was successfully prepared by a one-step solvothermal method and used for electrode modification to prepare a highly sensitive electrochemical sensor for rapid detection of capsaicin. Capsaicin could be selectively immobilized onto the Fe^III-HMOF-5 surface during infiltrating adsorption, thus exhibiting very excellent sensing performance. The detection conditions of the sensor were optimized. Under optimum conditions, the electrochemical sensor can linearly detect capsaicin in the range between 1–60 μM with a detection limit of 0.4 μM. In addition, the proposed electrochemical sensor showed excellent stability and selectivity. The real sample tests indicated the proposed electrochemical sensor was comparable to conventional UV spectrophotometry.

Construction of bifunctional electrochemical biosensors for the sensitive detection of the SARS-CoV-2 N-gene based on porphyrin porous organic polymers

In this study, a novel porphyrin-based porous organic polymer (POP) was constructed using 5,10,15,20-tetramine (4-aminophenyl) porphyrin (TAPP) and 5,5'-diformyl-2,2'-bipyridine (DPDD) as organic ligands via a solvothermal method (represented as TAPP-DPDD-POP). Then, it was utilized as a bifunctional scaffold for constructing a sensitive sensing strategy toward the nucleocapsid phosphoprotein (N-gene) of SARS-CoV-2. The obtained TAPP-DPDD-POP is composed of nanospheres with a size of 100-300 nm and possesses a highly conjugated and π-π stacking network. The coexistence of the porphyrin and bipyridine moieties of TAPP-DPDD-POP afforded considerable electrochemical activity and a strong binding interaction toward the SARS-CoV-2 N-gene-targeted antibody and targeted the aptamer strands of the N-gene. The TAPP-DPDD-POP-based aptasensor and immunosensor were manufactured for the sensitive analysis of SARS-CoV-2 N-gene, and exhibited the limit of detection (LOD) of 0.59 fg mL^-1 and 0.17 fg mL^-1, respectively, within the range of 0.1 fg mL^-1 to 1 ng mL^-1 of N-gene. The sensing performances of both the TAPP-DPDD-POP-based aptasensor and immunosensor were better than those of existing electrochemical biosensors for analyzing the N-gene, accompanied with excellent stability, high selectivity and reproducibility. The TAPP-DPDD-POP-based aptasensor and immunosensor were then employed to detect the N-gene from various environments, including human serum, river water, and seafoods. This work provides a new method of using an electrochemically active POP to sensitively and selectively analyze SARS-CoV-2 in diverse environments.