Visual and sensitive detection of telomerase activity via hydrogen peroxide test strip

A novel triple signal amplification platform of peroxide test strip for sensitive detection of adenosine triphosphate

Peroxide test strip (PTS) has been widely used for the point-of-care testing (POCT), but its poor sensitivity is a big obstacle for analyzing trace target. Herein, a triple signal amplifying platform integrating the liposome enrichment, the hybridization chain reaction (HCR) circuit, and the image analysis method was constructed to enhance the visual readout of PTS for the sensitive detection of adenosine triphosphate (ATP), an important biomarker of food spoilage. In the presence of ATP, the HCR amplifier was firstly initiated on the surface of magnetic beads (MBs), inducing a large number of glucose oxidase (GOD) imbedded liposomes to be attached. After the magnetic separation, the linked liposomes were destroyed and the enriched GOD was released to react with glucose to produce H2O2, which can enhance the color change of PTS. Finally, an image analysis method was developed to further amplify the colorimetric difference of human visual perception of PTS readout. This triple signal amplification strategy was used to detect ATP in the linear range from 50 to 250 nmol/L, and the limit of detection (LOD, 3σ/k) was 0.65 nmol/L. Finally, this method has been successfully applied for accurate and sensitive detection of ATP in watermelon juice, showing its great potential for quick determining whether food is spoiled.

Progress and Opportunities in Photocatalytic, Electrocatalytic, and Photoelectrocatalytic Production of Hydrogen Peroxide Coupled with Biomass Valorization

Hydrogen peroxide (H2O2) has been considered an energy carrier (fuel) and oxidizer for various chemical synthesis and environmental remediation processes. Biomass valorization can generate high-value-added products in a green and pollution-free way to solve the energy and environmental crisis. The biomass valorization coupled with H2O2 generation via photo-, electro-, and photoelectrocatalysis plays a positive role in sustainable targets, which can maximize energy utilization and realize the production of value-added products and fuel synthesis. Recently, catalyst design and mechanism studies in H2O2 generation coupled with biomass valorization are in the infancy stage. Herein, this review begins with a background on photo-, electro-, and photoelectrocatalytic techniques for H2O2 generation, biomass valorization, and the H2O2 generation couples with biomass valorization. Meanwhile, the progress and reaction mechanism are reviewed. Finally, the prospects and challenges of a synergistic coupled system of H2O2 synthesis and value-added biomass in achieving high conversion, selectivity, and reaction efficiency are envisioned.

Efficient and fast detection of uric acid based on a colorimetric sensing method

The uric acid (UA) level is an important physiological indicator of the human body, and its abnormality can lead to a series of diseases. Therefore, the immediate detection of uric acid concentration has broad application prospects. Commonly used methods for the analysis of uric acid include chromatography, high-performance capillary electrophoresis and electrochemical methods. However, these methods have the disadvantages of cumbersome sample pre-treatment, high cost, time-consuming, and the need for experimental instruments and professional operators, which are extremely unfavorable for the detection of uric acid and the diagnosis of related diseases in resource-limited areas. In this study, a portable visualization method was developed for the detection of uric acid using hydrogen peroxide (H2O2) test strips. Uric acid enzyme specifically catalyzes the oxidation of uric acid to produce H2O2, which causes a significant change in the color of the H2O2 test strip. The response has good linearity in the range of 1 ∼ 50 μg mL-1. Thus, it provides a simple, rapid, and cost-effective visualized bioassay for uric acid.

Recent progress in the design of photocatalytic H2O2 synthesis system

Photocatalytic synthesis of hydrogen peroxide under mild reaction conditions is a promising technology. This article will review the recent research progress in the design of photocatalytic H2O2 synthesis systems. A comprehensive discussion of the strategies that could solve two essential issues related to H2O2 synthesis. That is, how to improve the reaction kinetics of H2O2 formation via 2e- oxygen reduction reaction and inhibit the H2O2 decomposition through a variety of surface functionalization methods. The photocatalyst design and the reaction mechanism will be especially stressed in this work which will be concluded with an outlook to show the possible ways for synthesizing high-concentration H2O2 solution in the future.

Sensitive naked-eye detection of telomerase activity based on exponential amplification reaction and lateral flow assay

Telomerase is a promising diagnostic and prognostic biomarker for cancers. Sensitive, simple, and reliable telomerase activity detection is vital for cancer diagnosis. Herein, we developed an ultrasensitive visualized assay for telomerase activity that combined the exponential amplification reaction (EXPAR) and lateral flow assay for easy and quick signal readout, which we termed as a lateral flow readout-EXPAR (LFR-EXPAR) assay. In the LFR-EXPAR assay, telomerase elongation products initiate the exponential amplification reaction, the generated trigger hybridizes with the reporter to form the recognition site of the nicking enzyme, and the nicking enzyme cuts the reporter strand. The degradation of the reporter can be detected with a universal lateral flow dipstick and read out with the naked eye. After conducting a series of proof-of-concept investigations, the LFR-EXPAR assay was found to achieve a sensitivity comparable to that of a TRAP (telomere repeat amplification protocol) assay. The LFR-EXPAR assay can be used to realize ultrasensitive and point-of-care detection of telomerase without requiring specialized instruments, holding great promise for early cancer diagnosis.

Dual biomineralized metal-organic frameworks-mediated conversion of chemical energy to electricity enabling portable PEC sensing of telomerase activity in bladder cancer tissues

In this work, we report on a portable photoelectrochemical (PEC) sensing system for telomerase activity detection based on dual biomineralized ZIF-8 nanoparticles (NPs)-medicated conversion of chemical energy to electricity and terminal deoxynucleoside transferase (TdTase)-catalyzed elongation of Y-junction DNA structure. Two kinds of biomineralized ZIF-8 NPs including glucose oxidase (GOx)-encapsulated ZIF-8 (GZIF) and horseradish peroxidase (HRP)-encapsulated ZIF-8 (HZIF) are involved in this assay system. The recognition of telomerase is started with telomerase-catalyzed elongation of a telomerase substrate (TS) primer, which generates a longer elongation chain to trigger the formation of a Y-junction DNA structure. The Y-junction DNA with abundant 3'-OH terminal and small steric hindrance facilitates the implement of TdTase-catalyzed elongation reaction, in which the branches of Y-junction DNA are elongated and endowed with biotin moiety to capture streptavidin-modified GZIF (SA-GZIF). The signal transduction is then achieved on a luminol/HZIF/CdS-based photoelectrode. Once the H₂O₂ produced from GZIF-catalyzed hydrolysis of glucose is introduced to the photoelectrode, chemiluminescence of HRP-luminol-H₂O₂-p-iodo-phenol (PIP) system confined in HZIF is activated to excite photocurrent of CdS NPs, which is then recorded by a portable digital multimeter (DMM). The developed PEC sensing system possesses a wide calibration range from 50 to 5000 HeLa cells and a low detection limit of 46 cells. Significantly, the sensing platform is successfully applied to evaluate the telomerase activity in resected bladder tumor tissues. This work not only provides a diagnostic tool for telomerase-related diseases but also open a new avenue for establishing PEC assay methods using metal-organic framework (MOF) NPs.

Structure engineering of silicon nanoparticles with dual signals for hydrogen peroxide detection

Fluorescent silicon nanoparticles (SiNPs) were synthesized by a one-step, simple, and green method with 3-Aminopropyltriethoxysilane (APTES) and ascorbic acid (AA) as reaction agents. Subsequently, the SiNPs and AgNPs nanocomplex (SiNPs@AgNPs) was constructed as the probe for hydrogen peroxide (H₂O₂) detection. The fluorescence of SiNPs was quenched due to the surface plasmonic-enhanced energy transfer between SiNPs and AgNPs. Meanwhile, the color tends to be yellow due to the existence of AgNPs. As the AgNPs were etched by H₂O₂, the fluorescence recovers and color fadings. Based on the well-designed structure, the "off-on" fluorescence sensing and "on-off" color sensing platforms for H₂O₂ were fabricated. The as-synthesized materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Fluorescence and UV-vis absorption spectra were used to evaluate the optical performance. The fabricated sensor exhibited a linear range of 1.0-100.0 μM, with a limit of detection of 0.36 μM for the fluorescence sensing of H₂O₂. Additionally, a linear range of 1.0-50.0 μM and a limit of detection of 0.45 μM were displayed for the detection of H₂O₂ by colorimetric assay. The feasibility in complex medium of the fabricated fluorescent and colorimetric dual-signal sensor was evaluated by the detection of H₂O₂ in phosphate buffer saline (PBS) and lake water samples.

Visual detection of glucose by hydrogen peroxide test strips

Glucose detection is of great significance in the fields of clinical analysis and food industry. Herein, a visual and portable method was developed for detecting glucose via hydrogen peroxide (H2O2)...

Telomerase detection using a DNA-PAINT strategy

Telomerase plays an important role in maintaining the length of telomere during cell division and is recognized as a new kind of biomarkers for cancer diagnosis. In this work, we present a brand new telomerase detection strategy based on a DNA points accumulation for imaging in nanoscale topography (DNA-PAINT) like strategy. With an extraordinary spatial resolution (∼10 nm), the DNA-PAINT based strategy offers several advantages. First, it avoids complicated polymerase chain reaction and electrophoresis procedures. Second, it enables super resolution imaging of the reaction products with a high signal-to-noise ratio and facilitates the location of telomeric elongation sites on the single particle level, which results in a high sensitivity. Third, the detection scheme of the DNA-PAINT strategy allows directin situvisualization of the telomeric elongation process, which has never been achieved before. All these advantages make the DNA-PAINT telomerase detection strategy significant for dynamic investigation of telomerase related physiological processes as well as cancer diagnosis.

Epoxy-functionalized macroporous carbon with embedded platinum nanoparticles for electrochemical detection of telomerase activity via telomerase-triggered catalytic hairpin assembly

Telomerase is regarded as a crucial biomarker for the early diagnosis of malignant tumors and a valuable therapeutic target. In this work, a telomerase-triggered amplification strategy was designed on the basis of a catalyzed hairpin assembly (CHA) for bridging a signal probe of platinum nanoparticles (Pt NPs) anchored on three-dimensional (3D) epoxy-functionalized macroporous carbon (Pt/MPC-COOH) in an ultrasensitive electrochemical biosensor. Pt/MPC-COOH nanomaterials with interconnected macroporous structure not only immobilized hairpin DNA probe 2 (H2) via an amide reaction (Pt/MPC-COOH-H2), but they also generated an obvious electrochemical signal in response to acetaminophen (AP) oxidation. After the introduction of telomerase, telomerase primer (TP) was extended to a telomerase extension product (TEP) with several hexamer repeats (TTAGGG)n to initiate the CHA cycle, leading to signal amplification. Subsequently, with the TEP-triggered CHA cycle amplification strategy, a large amount of Pt/MPC-COOH-H2 was introduced on the electrode surface for the construction of the electrochemical platform, which realized the sensitive detection of telomerase activity from 10² to10⁷ cells mL^-1 with a limit of detection (LOD) of 9.02 cells mL^-1. This strategy provides a sensitive method for the detection of biomolecules that could be useful for bioanalysis and early clinical diagnoses of diseases.

An all-in-one telomerase assay based on CRISPR-Cas12a trans-cleavage while telomere synthesis

As one of the crucial factors associated with human life span and cancer progression, telomerase is regarded as an emerging biomarker for cancer diagnosis. Therefore, a facile, rapid and sensitive approach for telomerase activity detection with point-of-care (POC) diagnosis potential is in great demands. Herein, an all-in-one telomerase activity detection assay was established based on the telomere synthesis activated CRISPR-Cas12a system. A telomerase extension reaction generated telomere repeats sequences (TTAGGG)_n, which was recognized by a customized CRISPR-guided RNA (crRNA) simultaneously, and finally activated a typical trans-cleavage based CRISPR-Cas12a detection assay. With the inherent sensitivity of CRISPR-Cas12a, this approach achieved a great linear regression ranging from 100 to 2000 HeLa cells and a limitation of detection down to 26 HeLa cells. Moreover, by using the proposed method, telomerase can be detected in one pot under isothermal condition (37 °C) by a simple and fast workflow (one step within 1 h). Due to its excellent performance, this all-in-one method shows great potential in POC detection of the telomerase activity.

Three-dimensional bipedal DNA walker enabled logic gates responding to telomerase and miRNA

In this work, we have developed a simple and reliable platform for simultaneous analysis of telomerase and miRNA. A three-dimensional bipedal DNA walking strategy is designed utilizing gold nanoparticles and MnO2 nanosheets. Given the merits of fast, sensitive and selective analysis, the developed method has great potential application in early clinical diagnosis.

An ultrasensitive and point-of-care sensor for the telomerase activity detection

Telomerase owns great application potential in diagnosis, therapy, prognosis, and drug screening of cancers. Thus, the ultrasensitive and point-of-care detection of telomerase activity meets the clinical demands extremely. Here, a sensor based on telomerase extends activators to unlock the ssDNase activity of CRISPR/Cas12a was created for the first time to detect the telomerase activity. Based on the fluorescence or CRISPR/Cas12a-based lateral flow assay, we achieve the ultrasensitive and point-of-care detection of telomerase activity in MCF-7 cells low to 57 cells·mL^-1 and 5.7 × 10² cells·mL^-1 in about 1 h, respectively. Besides, the detection of telomerase activity in different subtype breast cancer cells indicates that the proposed sensor possesses potential in the classification of breast cancer cell subtypes.