A Novel Electrochemiluminescent Immunoassay Based on Target Transformation Assisted with Catalyzed Hairpin Assembly Amplification for the Ultrasensitive Bioassay

Research on the dentification of Panax ginseng and Panax quinquefolium using catalysed hairpin assembly technology

INTRODUCTION

Panax ginseng and Panax quinquefolium are traditional Chinese herb medicines and similar in morphology and some chemical components but differ in drug properties, so they cannot be mixed. However, the processed products of them are often sold in the form of slices, powder, and capsules, which are difficult to identify by traditional morphological methods. Furthermore, an accurate evaluation of P. ginseng, P. quinquefolium and the processed products have not been conducted.

OBJECTIVE

This study aimed to establish a catalysed hairpin assembly (CHA) identification method for authenticating products made from P. ginseng and P. quinquefolium based on single nucleotide polymorphism (SNP) differences.

METHOD

By analysing the differences of SNP in internal transcribed spacer 2 (ITS2) in P. ginseng and P. quinquefolium to design CHA-specific hairpins. Establish a sensitive and efficient CHA method that can identify P. ginseng and P. quinquefolium, use the sequencing technology to verify the accuracy of this method in identifying Panax products, and compare this method with high-resolution melting (HRM).

RESULTS

The reaction conditions of CHA were as follows: the ratio of forward and reverse primers, 20:1; hairpin concentration, 5 ng/μL. Compared with capillary electrophoresis, this method had good specificity and the limit of detection was 0.5 ng/μL. The result of Panax product identification with CHA method were coincidence with that of the sequencing method; the positive rate of CHA reaction was 100%.

CONCLUSION

This research presents an effective identification method for authenticating P. ginseng and P. quinquefolium products, which is helpful to improve the quality of Panax products.

Functionalized nanomaterials-based electrochemiluminescent biosensors and their application in cancer biomarkers detection

To detect a range of trace biomarkers associated with human diseases, researchers have been focusing on developing biosensors that possess high sensitivity and specificity. Electrochemiluminescence (ECL) biosensors have emerged as a prominent research tool in recent years, owing to their potential superiority in low background signal, high sensitivity, straightforward instrumentation, and ease of operation. Functional nanomaterials (FNMs) exhibit distinct advantages in optimizing electrical conductivity, increasing reaction rate, and expanding specific surface area due to their small size effect, quantum size effect, and surface and interface effects, which can significantly improve the stability, reproducibility, and sensitivity of the biosensors. Thereby, various nanomaterials (NMs) with excellent properties have been developed to construct efficient ECL biosensors. This review provides a detailed summary and discussion of FNMs-based ECL biosensors and their applications in cancer biomarkers detection.

Development of Nanobody-Displayed Whole-Cell Biosensors for the Colorimetric Detection of SARS-CoV-2

The accurate and effective detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential to preventing the spread of infectious diseases and ensuring human health. Herein, a nanobody-displayed whole-cell biosensor was developed for colorimetric detection of SARS-CoV-2 spike proteins. Serving as bioreceptors, yeast surfaces were genetically engineered to display SARS-CoV-2 binding of llama-derived single-domain antibodies (nanobodies) with high capture efficiency, facilitating the concentration and purification of SARS-CoV-2. Gold nanoparticles (AuNPs) employed as signal transductions were functionalized with horseradish peroxidase (HRP) and anti-SARS monoclonal antibodies to enhance the detection sensitivity. In the presence of SARS-CoV-2 spike proteins, the sandwiched binding will be formed by linking engineered yeast, SARS-CoV-2 spike proteins, and reporter AuNPs. The colorimetric signal was generated by the enzymatic reaction of HRP and its corresponding colorimetric substrate/chromogen system. At the optimal conditions, the developed whole-cell biosensor enables the sensitive detection of SARS-CoV-2 spike proteins in a linear range from 0.01 to 1 μg/mL with a limit of detection (LOD) of 0.037 μg/mL (about 4 × 108 virion particles/mL). Furthermore, the whole-cell biosensor was demonstrated to detect the spike protein of different SARS-CoV-2 variants in human serum, providing new possibilities for the detection of future SARS-CoV-2 variants.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Aggregation-Induced Electrochemiluminescence Immunosensor Based on 9,10-Diphenylanthracene Cubic Nanoparticles for Ultrasensitive Detection of Aflatoxin B1

9,10-Diphenylanthracene cubic nanoparticles (DPA CNPs) with aggregation-induced emission characteristic (AIEgens) were synthesized through a facile reprecipitation method; then, a bright and stable electrochemiluminescence (ECL) signal can be observed when the DPA CNPs were modified at the glassy carbon electrode (GCE) in the presence of Tri-n-propylamine (TPA). This phenomenon is ascribed to the molecules with restricted movement that greatly blocked the energy leakage during the relaxation of the excited state, which facilitated the emission of energy in the form of photons. In addition, the size confinement effect of DPA CNPs in the aggregated state effectively enhanced the ECL emission. The application of DPA CNPs with AIE characteristics in an electrochemiluminescence immunosensor has not been reported. In this contribution, a free-label aggregation-induced electrochemiluminescence immunosensor based on DPA CNPs was fabricated and a simple strategy for ultrasensitive detection of aflatoxin B₁ (AFB₁) was proposed. The ECL signal is quenched linearly in the range of 0.01 pg/mL to 100 ng/mL for AFB₁, and the detection limit is 3 fg/mL. In summary, the prepared sensor exhibits high sensitivity, acceptable accuracy, good anti-interference ability and stability, and satisfactory detection toward AFB₁ in walnut samples. Therefore, the fabricated immunosensor will have significant applications in the fields of food, medicine, and so on.

Electrochemiluminescence immunosensor based on the quenching effect of CuO@GO on m-CNNS for cTnI detection

A sandwich-type electrochemiluminescence (ECL) immunosensor based on the resonance energy transfer (RET) was proposed for ultrasensitive detection of cardiac troponin I (cTnI). The RET behavior could be generated between graphite carbon nitride nanosheets (m-CNNS) as donor and copper oxide@graphene oxide (CuO@GO) as acceptor, achieving the quenching effect of CuO@GO on m-CNNS for cTnI detection. The m-CNNS synthesized by mechanical grinding of the graphite carbon nitride (CN) not only has better dispersion and higher specific surface area, but also has high luminous efficiency and stable chemical properties. Therefore, m-CNNS was used as the matrix material and luminophore. As the acceptor, CuO@GO prepared by in-situ chemical synthesis of CuO NPs onto GO sheets also has a high specific surface area, which could be used as a label of secondary antibody (Ab₂). Under optimal conditions, cTnI could be determined within the linear range of 0.1 pg mL^-1 to 100 ng mL^-1 and had a low detection limit (0.028 pg mL^-1, S/N = 3). Meanwhile, the prepared ECL immunosensor possessed great stability, specificity and reproducibility, providing a new method for detecting cTnI and other biomarkers.

Enhanced biosensing strategies using electrogenerated chemiluminescence: recent progress and future prospects

An overview of enhancement strategies for highly sensitive ECL-based sensing of bioanalytes enabling early detection of cancer.