Sensitive Detection Of Telomerase Activity Research Articles

A triggered DNA nanomachine with enzyme-free for the rapid detection of telomerase activity in a one-step method

BackgroundTelomerase is considered a biomarker for the early diagnosis and clinical treatment of cancer. The rapid and sensitive detection of telomerase activity is crucial to biological research, clinical diagnosis, and drug development. However, the main obstacles facing the current telomerase activity assay are the cumbersome and time-consuming procedure, the easy degradation of the telomerase RNA template and the need for additional proteases. Therefore, it is necessary to construct a new method for the detection of telomerase activity with easy steps, efficient reaction and strong anti-interference ability. ResultsHerein, an efficient, enzyme-free, economical, sensitive, fluorometric detection method for telomerase activity in one-step, named triggered-DNA (T-DNA) nanomachine, was created based on target-triggered DNAzyme-cleavage activity and catalytic molecular beacon (CMB). Telomerase served as a switch and extended few numbers of (TTAGGG)n repeat sequences to initiate the signal amplification in the T-DNA nanomachine, resulting in a strong fluorescent signal. The reaction was a one-step method with a shortened time of 1 h and a constant temperature of 37 °C, without the addition of any protease. It also sensitively distinguished telomerase activity in various cell lines. The T-DNA nanomachine offered a detection limit of 12 HeLa cells μL−1, 9 SK-Hep-1 cells μL−1 and 3 HuH-7 cells μL−1 with a linear correlation detection range of 0.39 × 102–6.25 × 102 HeLa cells μL−1 for telomerase activity. SignificanceIn conclusion, our study demonstrated that the triggered-DNA nanomachine fulfills the requirements for rapid detection of telomerase activity in one-step under isothermal and enzyme-free conditions with excellent specificity, and its simple and stable structure makes it ideal for complex systems. These findings indicated the application prospect of DNA nanomachines in clinical diagnostics and provided new insights into the field of DNA nanomachine-based bioanalysis.

A SERS Biosensor Based on Functionalized Au-SiNCA Integrated with a Dual Signal Amplification Strategy for Sensitive Detection of Telomerase Activity During EMT in Laryngeal Carcinoma.

This paper aims to construct a surface-enhanced Raman spectroscopy (SERS) biosensor based on functionalized Au-Si nanocone arrays (Au-SiNCA) using a dual signal amplification strategy (SDA-CHA) to evaluate telomerase activity during epithelial-mesenchymal transition (EMT) in laryngeal carcinoma (LC). A SERS biosensor based on functionalized Au-SiNCA was designed with an integrated dual-signal amplification strategy to achieve ultrasensitive detection of telomerase activity during EMT in LC patients. Labeled probes (Au-AgNRs@4-MBA@H1) and capture substrates (Au-SiNCA@H2) were prepared by modifying hairpin DNA and Raman signal molecules. Using this scheme, telomerase activity in peripheral mononuclear cells (PMNC) could be successfully detected with a limit of detection (LOD) as low as 10-6 IU/mL. In addition, biological experiments using BLM treatment of TU686 effectively mimicked the EMT process. The results of this scheme were highly consistent with the ELISA scheme, confirming its accuracy. This scheme provides a reproducible, selective, and ultrasensitive assay for telomerase activity, which is expected to be a potential tool for the early screening of LC in future clinical applications.

Multifunctional semiconducting carbon nitrides enabling sequential fluorescent sensing of telomerase activity and internal self-checking

Improving the detection reliability of biosensors is essential but challenging. The dual-signal self-checking function is useful for the development of reliable biosensors; however, it inevitably increases the complexity of the sensing system. Thus, biosensors with intrinsic self-checking functions that do not require additional chemicals, specific sensor assemblies, and/or instruments are highly desirable. Herein, integrating the ability of fluorescence detection and photodegradation by carbon nitride nanosheets (CNNS), a biosensor with a self-checking function for sensitive telomerase activity detection was constructed. Acriflavine (AF) was screened from various dyes to form the most effective CNNS-AF donor-acceptor (D-A) interfaces by experiments and density functional theory (DFT) calculations, considering spectral match, electrostatic interaction, and non-covalent stacking. As a result, the proposed fluorescence biosensor not only showed highly sensitive detection of telomerase activity but also had an internal self-checking function by photodegradation of AF via continuous excitation and measurement of recovered fluorescence. This study sheds light on CNNS-based D-A interfaces with synergistic fluorescence detection and photocatalysis-induced self-checking properties for future clinical diagnosis with high sensitivity and reliability.

Sensitive and amplification-free detection of telomerase activity by self-extension of telomerase and trans-cleavage of CRISPR/Cas12a

Telomerase is a well-known cancer biomarker, and the reliable and sensitive detection of telomerase activity is of vital significance for cancer diagnosis and treatment. Despite many attempts, the sensitive methods for telomerase activity assay mainly depend on the various nucleic acid amplification, which requires complex primers/probes design and multiple enzymes. In addition, the multiple experimental procedures may introduce false-positive results from cross-contamination of amplification products challenging the reliability of telomerase-based diagnostics detection. Herein, we present a reliable, amplification-free, and sensitive strategy for the detection of telomerase activity based on the self-extension of telomerase and trans-cleavage of CRISPR/Cas12a. In this work, crRNA/Cas12a complexes can specifically target the self-extending telomere-repetitive DNA and activate the typical CRISPR/Cas12a-based fluorescent output system, which allows the detection of telomerase activity in very few cancer cells (5 HeLa cells) without complex primer design and any nucleic acid amplification. Furthermore, the proposed method holds high reliability and specificity in distinguishing tumor cells from normal cells. With these unique features, including high sensitivity and reliability, excellent specificity, and simplicity, this method highlights a great potential for telomerase-related research and broadens the CRISPR-Cas12a-based sensing toolbox.

A primer extension activating 3D DNAzyme walker for in situ imaging and sensitive detection of telomerase activity.

Acquiring information on telomerase activity at multiple levels contributes to a better understanding of its role in various physiological and pathological processes. Herein, a primer extension activating 3D DNAzyme walker is developed for in situ imaging and sensitive detection of telomerase activity. This walker is constructed via co-modifying specially designed hairpin structured walking strands and track strands on a gold nanoparticle (AuNP). The walking strand contains a pre-blocked DNAzyme sequence and a telomerase primer hybridized to its root. The track strand embeds at an RNA cleavage site and is labeled with the FAM group. After this walker is taken up by cells, the telomerase primer is extended under the action of endogenous telomerase to liberate DNAzyme. The liberated DNAzyme cuts track strands in the presence of the cofactor Mn2+ to drive the walker's processive operation, resulting in an enhanced fluorescence recovery of the AuNP-quenched FAM fluorophore. In situ imaging of telomerase activity in three different cell lines (MCF-7 cells, HeLa cells and HL-7702 cells) was well implemented. The discrimination of cancer cells from normal cells and the screening of telomerase inhibitors have been achieved. The sensitive detection of telomerase activity in HeLa cell lysate has also been realized with a detection limit of 10 cells. This walker performed a new approach for monitoring telomerase activity from different levels, providing a potential tool for clinical diagnosis, prognostic evaluation and drug screening.

SERS-based copper-mediated signal amplification strategy for simple and sensitive detection of telomerase activity

Simple and sensitive detection of telomerase activity is of vital importance for both early diagnosis and therapy of malignant tumors. Inspired by DNA-biobarcode amplification reported by Chad A. Mirkin, we developed a facile DNA-biobarcode-like SERS-based copper-mediated signal amplification strategy for sensitive detection of telomerase activity. In this strategy, a duplex DNA constructed by hybridization of a copper oxide nanoparticle (CuO NP)-labeled reporting sequence (RS) with the telomerase primer sequence (TS) is ingeniously designed, and anchored on the magnetic bead (MB) to build the CuO NPs-encoded magnetic bead (MB-CuO NPs) detection probe. Upon selective sensing of telomerase, telomerase elongation reaction and structure change of TS products make the CuO NP-RS displace and separate from MB. The separated CuO NPs are dissolved into a mass of Cu2+, which prompt monodisperse dopamine-functionalized AgNPs (D-AgNPs) signal probe into aggregation, resulting in color changes and significantly enhancing of SERS signal. The SERS signal increases with the increase of Cu2+, which is directly proportional to the telomerase. Benefiting from the transformation of CuO NP to Cu2+ with a high amplification effect, this strategy could realize the telomerase activity measurement down to 3 HeLa cells and a dynamic range of 10–10000 cells. It shows a significant improvement of sensitivity without need for other enzymes and elaborate design, which escapes from the complicated manipulations and design in polymerase chain reaction (PCR) and DNA amplification techniques. Moreover, with this strategy, telomerase activities of different cell lines and telomerase inhibitors screening were successfully performed. Significantly, it can also be utilized for visual detection of telomerase, which validates the potential on-site application and its application as point-of-care testing (POCT) for efficient monitoring. Given the high-performance for telomerase analysis, the strategy has a promising application in biological detection and clinical diagnosis, as well as point-of-care tests.

Proximity binding-triggered multipedal DNA walker for the electrochemiluminescence detection of telomerase activity

The sensitive detection of telomerase activity is of great significance for the early diagnosis and treatment of cancer. Here, an innovative electrochemiluminescence resonance energy transfer (ECL-RET) sensor was explored to reliably detect telomerase activity based on proximity binding-triggered multipedal DNA walker. In this system, CdS quantum dots (CdS QDs) and silver nanoclusters (Ag NCs) were applied as ECL donor and acceptor, respectively. By ingeniously introducing a repetitive bases sequence (TTAGGG) along the telomerase primer, multiple same DNA “legs” were formed, leading to the activation of proximity binding-triggered multipedal DNA walker. Unlike the traditional unipedal DNA walker, one walking step of multipedal DNA walker concurrently initiated the responsivity of multiple signals, resulting in the shortening of the walking time and improvement of the signal amplification efficiency. Thus, under optimal conditions, the designed ECL-RET sensor exhibited a wide dynamic correlation of HeLa cells’ telomerase activity from 1 × 102 to 1 × 106 cells/mL and a low detection limit of 16 cells/mL. Moreover, this sensor realized the general and reliable analysis of telomerase activity in different cell lines. Due to the outstanding application potential in real samples, it is believed that the ECL-RET sensing system provides a new approach for the application of telomerase activity assays in cancer diagnostics.

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.

Electrochemical biosensor for telomerase activity assay based on HCR and dual interaction of the poly-adenine DNA with Au electrode and Ce-Ti dioxide nanorods

Abstract A new electrochemical biosensor for sensitive detection of telomerase activity based on the hybridization chain reaction and the dual interaction of the poly-adenine (polyA) DNA with Au electrode and Ce-Ti dioxide nanorods (Ce-Ti NRs) has been constructed. Deoxynucleotide triphosphates (dNTPs) can be incorporated at the 3´-OH of TS primer by telomerase to generate the extension products with telomeric repeats (TTAGGG)n (TEP), which can hybridize with hairpin (HP) DNA and open it to form a duplex DNA with a short poly-adenine DNA single-stranded tail (s1). The duplex DNA can be recognized and selectively cleaved into single-stranded DNA fragment s1 and TEP by exonuclease III (Exo III). The released TEP can then hybridize with the HP again to initiate the s1 recycling process, which will result in the massive release of s1 fragments from HP. The s1 fragments can be immobilized on the Au electrode surface through the interaction between polyA and Au electrode on one hand. On the other hand, Ce-Ti NRs can be adsorbed on the Au electrode surface by the interaction between Ce-Ti NRs and the phosphate groups of s1, resulting in the decrease of the differential pulse voltammetry (DPV) current of the redox probe. The higher activity of telomerase, more HP can be hybridized and cleaved, more poly-adenine and Ce-Ti NRs can be immobilized on electrode surface, and remarkable decrease of the DPV signal can be observed. The biosensor exhibited good sensitivity toward telomerase activity in HeLa cells.

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

The point of care testing (POCT) of telomerase activity is critical for early diagnosis of cancer. Herein, a colorimetric method was developed for visual detection of telomerase activity via hydrogen peroxide test strip. It is based on the telomerase-controlled in-situ formation of hydrogen peroxide. Firstly, biotinylated telomerase substrate (TS) primer was attached on the surface of magnetic beads (MBs) via the streptavidin-biotin reaction to form MB-TS complex. Then, TS primers were elongated by telomerase to form long telomere elongated products (TEP) which contains TTAGGG repeat units. The in-situ formed MB-TEP complex specifically hybridized with glucose oxidase modified cDNA (GOD-cDNA). After magnetic separation and washing, the MB-TEP/GOD-cDNA complex incubated with glucose solution to in-situ produce hydrogen peroxide which was detected by hydrogen peroxide test strip. One long TEP hybridized with multiple GOD-cDNAs, which enriched GOD to highly efficiently catalyze glucose for generating hydrogen peroxide. Thus, the visual assay achieved sensitive detection of telomerase activity, and the limit of detection (LOD) reached as low as 10 HeLa cells/μL by naked eyes and 4.5 HeLa cells/μL by absorbance measurements. Therefore, it offers a sensitive and low-cost method for visual detection of telomerase activity, which also, widens the application of commercial hydrogen peroxide test strip in the development of non-H2O2 biosensors.

Sensitive detection of telomerase activity in cells using a DNA-based fluorescence resonance energy transfer nanoprobe

Telomerase activity is inhibited in normal somatic cells but abnormally high in the majority of cancer cells. Maintenance of active telomerase in cancer cells promotes proliferation and immortalization. With the difference in telomerase activity between cancer and normal cells in mind, we designed a nanoprobe based on quantum dot (QD) and fluorescence resonance energy transfer (FRET). The nanoprobe consisted of a specific sequence of DNA with the two ends labeled with QD as a fluorescent donor and Alexa488 as a fluorescent acceptor, respectively. FRET signal tracking was performed by adjusting the distance between donors and acceptors, and changes in the FRET signal shown to be related to telomerase activity. Incubation of cells with the nanoprobe facilitated sensing of intracellular telomerase activity, and consequent discrimination between normal and cancer cells. Our novel DNA nanoprobe based on QD-FRET achieved sensitive detection of telomerase in cells up to a detection limit of one cell, and quantitative detection of telomerase activity in different numbers of cells. The nanoprobe generated in this study is expected to allow dynamically monitoring of the changes in telomerase activity in cells under treatment with drugs, providing a potential basis for early diagnosis and management of cancer.

Regulation of multiple energy transfer processes in a simple nano-system for sensitive telomerase detection

Telomerase, as a potential biomarker for early cancer diagnostics and therapies, has attracted considerable interests concerning its detection and monitoring. Herein, we develop a novel method for sensitive detection of telomerase activity by designing a gold nanoparticles/graphene oxide (AuNPs/GO) probe. The AuNPs were functionalized with a telomerase substrate (TS) primer and a 6-carboxy-fluorescein (FAM)-modified complementary DNA (P1). In the absence of telomerase, P1 exists in the random-coiled conformation, and the fluorescence resonance energy transfer (FRET) from FAM to AuNPs and GO results in efficient fluorescence quenching. In the presence of telomerase, the multiple hybridization between TS extension products and P1 leads to the conformation transition of P1 from single-stranded DNA to double-stranded rigid structure, and thus the FRET process can be prevented with the efficient fluorescence recovery. The metal enhanced fluorescence (MEF) effect between FAM and AuNPs can further effectively enhance the fluorescence of FAM, and thus the sensitivity and specificity of telomerase detection can be remarkably improved. It is worth mentioning that the proposed strategy does not need to design complex hairpin structure and allows the measurement of telomerase activity in three crude cell extracts equivalent to 7 HeLa cells, 8 A549 cells and 8 L929 cells in 1 h. In addition, the present sensing platform can be applied to inhibitor screening, in situ telomerase imaging, and intracellular drug delivery.

Plasmonic colorimetric biosensor for visual detection of telomerase activity based on horseradish peroxidase-encapsulated liposomes and etching of Au nanobipyramids

Telomerase aberrant activation is a critical feature in the vast majority of cancers. To visualize telomerase expression level in tumor cells, we developed a plasmonic colorimetric sensor for highly sensitive detection of telomerase activity by integrating an excellent etching substrate Au nanobipyramids (Au NBPs) with a liposome-based signal amplification strategy. Upon telomerase-triggered extension, the telomerase activity was converted into the amount of the attached horseradish peroxidase-encapsulated liposomes (HRP-Ls) on the surfaces of magnetic beads. Afterwards, HRP was liberated from the liposomes following the addition of H2O2-3,3′,5,5′-tetramethylbenzidine sulfate (TMB) substrate, and then the oxidation reaction between H2O2 and TMB was initiated to form TMB2+. The morphological evolution of Au NBPs relied on the TMB2+-mediated etching reaction, which gave rise to tremendous localized surface plasmon resonance (LSPR) responses and concomitant tonality transitions. Benefiting from cascaded signal amplification capacity of HRP-Ls and the intriguing optical properties of Au NBPs, an impressive sensitivity toward telomerase was obtained with detection limits equivalent to 1 HeLa cell for LSPR peak measurement and a visual detection limit of 20 HeLa cells. Furthermore, a facile and portable kit was fabricated for visual evaluation of telomerase activity in different cell lines.

A seesaw ratiometric probe for dual-spectrum imaging and detection of telomerase activity in single living cells.

Herein, a seesaw ratiometric (SR) probe is designed which integrates fluorescence and surface enhanced Raman scattering (SERS) technology. Fluorescence imaging enables tracking of the spatiotemporal dynamic behaviour of telomerase. Meanwhile, SERS reverse ratiometric measurement can enable sensitive detection of telomerase activity in single living cells.

Primer-Modified G-Quadruplex-Au Nanoparticles for Colorimetric Assay of Human Telomerase Activity and Initial Screening of Telomerase Inhibitors.

G-quadruplexes formed by 3'-overhang of guanine-rich human telomeric DNA at the end of chromosome have important implication in inhibiting the telomerase activity. Telomerase catalyzes the elongation of telomeres by adding telomeric repeats sequence TTAGGG onto the end of the chromosome. Since telomerase is over-expressed in 80-90% of all known human tumors, the enzyme can be recognized as a biomarker for cancer diagnosis and a therapeutic target. Thus, the sensitive detection of telomerase activity is essential to cancer diagnosis and therapy, and screening of anticancer drugs. Gold nanoparticles (AuNPs) have been widely applied as a colorimetric probe for assay owing to their unique size- and distance-dependent optical properties. Human telomerase activity can be visualized by using primer-modified Au nanoparticles. The extremely high extinction coefficients of AuNPs offered high sensitivity. Here, we describe a protocol for the preparation of primer-modified Au nanoparticles for colorimetric assay of human telomerase activity and initial screening of telomerase inhibitors.

A sensitive assay of telomerase activity based on the controllable aggregation of quantum dots

In order to overcome the shortcomings of traditional methods for telomerase activity detection of time-consuming and susceptibility to interferences in cell extracts, here, we develop a semiconductor quantum dots-streptavidin conjugates (QDs-SA)-based biosensor for sensitive detection of telomerase activity. In the absence of telomerase, the aggregation and thus the fluorescence quenching of QDs-SA can be observed in buffer solution due to charge shielding effect. In the presence of telomerase and biotin-dATP, QDs-SA will bind to telomerase elongation products due to the high affinity between the biotin and streptavidin, protecting the QDs-SA from aggregation and retaining their strong fluorescence. This sensor exhibited good fluorescence responses toward telomerase activity from HeLa cells in the range of 40–1000 cells with a detection limit of 13 cells or A549 cells within the linear range of 20–500 cells with a detection limit of 9 cells. Furthermore, the sensor can be used to efficiently monitor the evolution of telomerase activity in living cells, demonstrating great potential in tumor diagnosis and inhibitor drug screening.

Sensitive detection of telomerase activity in cancer cells using portable pH meter as readout

This study developed a portable and sensitive biosensor for the detection of telomerase activity extracted from HeLa cells by monitoring urease regulated pH change. In the presence of telomerase, the telomerase substrate (TS) primer was elongated by adding telomeric repeats (TTAGGG)n firstly. The TS primer was then immobilized onto streptavidin magnesphere paramagnetic particles (PMPs). The elongated repeat unit can hybridize with biotinylated complementary DNA (cDNA) to specifically capture biotinylated urease onto PMPs. After magnetic separation, the PMPs complex was mixed with urea solution. As urease can catalyze the hydrolysis of urea into ammonia and induce pH increasing of the solution, the activity of telomerase can be detected by pH-sensitive dyes or by a portable pH meter easily. The changed pH has a linear relationship with the logarithm of the number of HeLa cells from 50 to 10,000 and with a detection limit of ~20 HeLa cells, which indicated the proposed method have potential application in telomerase-related cancer diagnosis.

Magneto-controlled photoelectrochemical sensor for sensitive monitoring of telomerase activity based on removal of electron acceptors mediated by G-quadruplex/hemin complexes

Herein we report on a novel magneto-controlled photoelectrochemical (PEC) sensor for sensitive detection of telomerase activity based on an electron-acceptor elimination strategy. For telomerase activity sensing, a telomerase substrate (TS) primer is anchored on the surface of magnetic beads (MBs). Under telomerase catalysis, the TS primer is extended to generate longer G-rich single strand DNA, which can bind with hemin to form G-quadruplex/hemin complexes. Based on this mechanism, the resulting MBs are used to capture hemin molecules in electrolyte solution and reduce their concentration. Since hemin acts as electron acceptor for a p-CuBi2O4 nanorod-based photocathode, a decrease in hemin concentration will lead to a decreasing photocurrent signal. By recording the decay of the photocurrent, the telomerase activity can be monitored with high sensitivity. Under optimal conditions, the developed sensor allows measurement of telomerase activity in cell extracts over the range 100–2000 HeLa cells with the limit of detection (LOD) as low as 53 cells (S/N = 3). The practicability of the developed method is also demonstrated by using it to screen telomerase inhibitors.

Polyamidoamine starburst dendrimer-activated chromatography paper-based assay for sensitive detection of telomerase activity

Telomerase is extensively expressed in various cancer cells and recognized as a target for cancer drug discovery. In the present study, a simple and amplification-free fluorescence assay based on polyamidoamine starburst dendrimer (PAMAM dendrimer)-activated paper device is proposed for sensitive detection of telomerase activity through hybridization of Cy5 modified single strand DNA probes with telomerase extension products. The paper substrate is fabricated by hand drawing according to a template, which is low cost, instrument free and easy operation. PAMAM is rich in amino groups on its surface and employed to immobilize the telomerase substrate (TS) primer. Highly sensitive detection of telomerase activity in HeLa cell lysate of 10 cells is achieved since the PAMAM dendrimer-activated paper surface can provide high density of binding sites for immobilization of TS primer. The experimental results also demonstrate that the assay can be employed to evaluate telomerase activity levels of various cell lines and screen telomerase inhibitors.

Evaluation of foodborne risks for mother and child health; contamination of foods of animal origin by antibiotics in the republic of Georgia

Herein we report on a novel magneto-controlled photoelectrochemical (PEC) sensor for sensitive detection of telomerase activity based on an electron-acceptor elimination strategy. For telomerase activity sensing, a telomerase substrate (TS) primer is anchored on the surface of magnetic beads (MBs). Under telomerase catalysis, the TS primer is extended to generate longer G-rich single strand DNA, which can bind with hemin to form G-quadruplex/hemin complexes. Based on this mechanism, the resulting MBs are used to capture hemin molecules in electrolyte solution and reduce their concentration. Since hemin acts as electron acceptor for a p-CuBi2O4 nanorod-based photocathode, a decrease in hemin concentration will lead to a decreasing photocurrent signal. By recording the decay of the photocurrent, the telomerase activity can be monitored with high sensitivity. Under optimal conditions, the developed sensor allows measurement of telomerase activity in cell extracts over the range 100–2000 HeLa cells with the limit of detection (LOD) as low as 53 cells (S/N = 3). The practicability of the developed method is also demonstrated by using it to screen telomerase inhibitors.