Ratiometric electrochemical biosensor for ultrasensitive and highly selective detection of p53 gene based on nicking endonuclease-assisted target recycling and rolling circle amplification

Triblock polyadenine-based electrochemical aptasensor for ultra-sensitive detection of carcinoembryonic antigen via exonuclease III-assisted target recycling and hybridization chain reaction

Carcinoembryonic antigen (CEA), a key colon biomarker, demands a precise detection method for cancer diagnosis and prognosis. This study introduces a novel electrochemical aptasensor using a triblock polyadenine probe for ultra-sensitive detection of CEA. The method leverages Exonuclease III (Exo III)-assisted target recycling and hybridization chain reaction. The triblock polyadenine probe self-assembles on the bare gold electrode through the strong affinity between adenine and gold electrode, blocking CEA diffusion and providing a large immobilization surface. CEA binding to hairpin probe 1 (HP1), followed by the hybridization between HP1 and hairpin probe 2 (HP2), triggers DNA cleavage by Exo III, amplifying the signal via a hybridization chain reaction and producing numerous dsDNA walkers that generates a dramatic electrochemical impedance signal. Under optimized conditions, the aptasensor achieved two ultra-low detection limits: 0.39 ag∙mL-1 within the concentration range of 5 ag∙mL-1 to 5 × 106 ag∙mL-1, and 1.5 ag∙mL-1 within the concentration range of 5 × 106 ag∙mL-1 to 1 × 1010 ag∙mL-1. Its performance in human serum samples meets the practical standards, offering a promising new tool for ultrasensitive tumor marker detection, potentially revolutionizing early cancer diagnosis.

A ratiometric electrochemical biosensor based on ARGET ATRP for detection of HER2 gene

Human epidermal growth factor receptor 2 (HER2), a common proto-oncogene, is overexpressed in a subset of breast cancer patients. It is essential to track HER2 expression for early breast cancer diagnosis. Herein, a ratiometric electrochemical biosensor for detection of HER2 based on activators generated by electron transfer for atom transfer radical polymerisation (AGET ATRP) and hairpin DNA was developed. Specifically, hairpin DNA was first self-assembled on the gold electrode by Au-S bond. Upon capturing HER2, the stem-loop structure of hairpin DNA was unfolded, the signal value of methylene blue (MB) decreased as it moved away from the electrode surface. cDNA was linked with HER2 by complementary base pairing to introduce amino group. Then, the initiator 2-bromo-2-methylpropionic acid (BMP) were connected to the amino group on the cDNA to activate ARGET ATRP. The detection performance of biosensors for HER2 was explored by the ratio signal between two signal molecules. Under optimal conditions, this ratiometric electrochemical biosensor shows good selectivity and stability with a wide detection range of 1-1 × 106 pM and a detection limit of 78.47 fM. Furthermore, the biosensor exhibits satisfactory anti-interference ability due to the hairpin DNA and dual signal system, and has promising application prospects in the detection of other DNA disease markers.

Electrochemical biosensors for analysis of DNA point mutations in cancer research

Cancer is a genetic disease induced by mutations in DNA, in particular point mutations in important driver genes that lead to protein malfunctioning and ultimately to tumorigenesis. Screening for the most common DNA point mutations, especially in such genes as TP53, BRCA1 and BRCA2, EGFR, KRAS, or BRAF, is crucial to determine predisposition risk for cancer or to predict response to therapy. In this review, we briefly depict how these genes are involved in cancer, followed by a description of the most common techniques routinely applied for their analysis, including high-throughput next-generation sequencing technology and less expensive low-throughput options, such as real-time PCR, restriction fragment length polymorphism, or high resolution melting analysis. We then introduce benefits of electrochemical biosensors as interesting alternatives to the standard methods in terms of cost, speed, and simplicity. We describe most common strategies involved in electrochemical biosensing of point mutations, relying mostly on PCR or isothermal amplification techniques, and critically discuss major challenges and obstacles that, until now, prevented their more widespread application in clinical settings.

Ultrasensitive electrochemical platform for the p53 gene via molecular beacon-mediated circular strand displacement and terminal deoxynucleotidyl transferase-mediated signal amplification strategy

As an important tumor suppressor gene, the p53 gene is considered to be a typical biomarker for the early diagnosis and prognosis evaluation of severe cancer. Herein, an electrochemical biosensor was proposed for the ultrasensitive detection of the p53 gene based on molecular beacon-mediated circular strand displacement polymerization combined with terminal deoxynucleotide transferase-mediated template-free DNA extension. Firstly, the p53 gene opened the hairpin structure of the molecular beacon, thereby exposing the binding sequence region of the primer DNA. The circular strand displacement polymerization occurred in the presence of the primer DNA and phi29 DNA polymerase, subsequently resulting in the circulation of the p53 gene. With the catalysis of the terminal deoxynucleotide transferase, the 3'-OH terminal sequence of the molecular beacon elongated to produce long single-stranded DNA under the template-free DNA extension. Methylene blue bound with such DNA strands generated a strong differential pulse voltammetry (DPV) signal with a peak potential of -0.28 V. Under the optimal detection conditions, the DPV signal of methylene blue showed good linear relationships with the logarithm value of the p53 gene in two concentration ranges of 0.05 fM to 3 pM and 5 fM to 100 fM, and the detection limit of the p53 gene was as low as 0.018 fM. This electrochemical biosensor possessed high recognition ability for the p53 gene in its analogues and was successfully applied for p53 gene analysis in human serum samples.

A novel ratiometric electrochemical aptasensor for highly sensitive detection of carcinoembryonic antigen

A novel ratiometric electrochemical aptasensor was proposed for carcinoembryonic antigen (CEA) detection based on exonuclease III (Exo III)-assisted recycling and rolling circle amplification (RCA) strategies. A thiolated ferrocene-labeled hairpin probe 2 (Fc-HP2) was fixed on the gold nanoparticles (AuNPs)-modified gold electrode (AuE) surface through Au-S bonds. The presence of CEA led to the release of trigger, which hybridized with the 3'-protruding of hairpin probe 1 (HP1) and triggered the Exo III cleavage reaction, accompanied by the releasing of trigger and generation of new DNA fragment which was used for the successive hybridization with Fc-HP2. After the Exo III cleavage process, the remaining Fc-HP2 fragments hybridized as primers with the RCA template to initiate the RCA process, and long single-stranded polynucleotides were produced for methylene blue (MB) binding. Such changes resulted in the signal of Fc (I_Fc) decreased and that of MB (I_MB) increased, achieving a linear relationship between I_MB/I_Fc and logarithm of CEA concentrations ranging from 1.0 pg mL^-1 to 100.0 ng mL^-1 with a detection limit of 0.59 pg mL^-1. Additionally, the developed aptasensor had been successfully applied to detect CEA in human serum samples. Therefore, the proposed strategy might provide a new platform for clinical detections of CEA.

Ultrasensitive ratiometric fluorescent probes for Hg(ii) and trypsin activity based on carbon dots and metalloporphyrin via a target recycling amplification strategy

A ultrasensitive ratiometric fluorescent probe was developed for Hg(ii) and trypsin based on CDs and TPPS via a target recycling amplification strategy. The detection limits of Hg2+ and trypsin were 0.086 nM and 0.013 ng mL−1.