Chimeric Aptamers-Based and MoS2 Nanosheet-Enhanced Label-Free Fluorescence Polarization Strategy for Adenosine Triphosphate Detection

Optically active two-dimensional MoS2-based nanohybrids for various biosensing applications: A comprehensive review

Following the discovery of graphene, there has been a surge in exploring other two-dimensional (2D) nanocrystals, including MoS2. Over the past few decades, MoS2-based nanocrystals have shown great potential applications in biosensing, owing to their excellent physico-chemical properties. Unlike graphene, MoS2 shows layer-dependent finite band gaps (∼1.8 eV for a single layer and ∼1.2 for bulk) and relatively strong interaction with the electromagnetic spectrum. The tunability of the size, shape, and intrinsic properties, such as high optical absorption, electron mobility, mechanical strength and large surface area, of MoS2 nanocrystals, make them excellent alternative probe materials for preparing optical, photothermal, and electrical bio/immunosensors. In this review, we will provide insights into the rapid evolutions in bio/immunosensing applications based on MoS2 and its nanohybrids. We emphasized the various synthesis, characterization, and functionalization routes of 2D MoS2 nanosheets/nanoflakes. Finally, we discussed various fabrication techniques and the critical parameters, including the limit of detection (LOD), linear detection range, and sensitivity of the biosensors. In addition, the role of MoS2 in enhancing the performance of biosensors, the limitations associated with current biosensing technologies, future challenges, and clinical implications are addressed. The advantages/disadvantages of each biosensor technique are also summarized. Collectively, we believe that this review will encourage resolute researchers to follow up further with the state-of-the-art MoS2-based biosensing technology.

Dual-signal fluorescence aptasensing system for adenosine triphosphate assisting by MoS2 nanosheets

Adenosine triphosphate (ATP) has an irreplaceable role in the maintenance of many physiological processes and biological functions, and can be employed as an indicator of many diseases. In this work, we constructed a simple and sensitive dual-signal fluorescence aptasensing system for ATP detection with berberine as the signal reporter, ATP-aptamer as the recognition unit and MoS2 nanosheets as the signal amplification. In the absence of ATP, berberine can bind to the single-stranded DNA (ssDNA) of ATP-aptamer and selectively assemble on the surface of MoS2 nanosheets, leading to the fluorescence quenching of bererbine based on the fluorescence resonance energy transfer, denoted by "OFF". Accordingly, the fluorescence anisotropy signal is enhanced due to restriction on rotate of the fluorescent probe and denoted as "ON". Conversely, in the presence of ATP, it specifically interacts with ATP-aptamer and switches the free-curled single-stranded of ATP-aptamer to the G-quadruplex structure of ATP-aptamer/ATP/berberine, causing the detachment from the surface of the MoS2 nanosheet. Accordingly, the fluorescence signal was reversed from "OFF" to "ON", and the fluorescence anisotropy signal was turned "ON" to "OFF". The developed aptasensing system achieved a desirable sensitivity of 40.0 nM with fluorescent mode, and of 20.8 nM with fluorescent anisotropic mode. The sensing system has demonstrated high quality detection performance in human serum sample, and obtained the satisfactory recovery results for fluorescent of 93.0-108.5%, fluorescent anisotropic of 96.4-106.7%.

A naphthalimide-tyrosine-based dicationic amphiphile for intracellular 'turn-on' simultaneous detection of ATP and CTP

We have developed a new naphthalimide-based amphiphile (YN-1) for the simultaneous detection of ATP and CTP. In YN-1, the cationic tyrosine-linked polyamine (+2 charge, hydrophilic unit) is appended at the -peri position of naphthalimide (hydrophobic unit). YN-1 and its Boc-protected compound 4 were characterized using state-of-the-art spectroscopic and optical techniques such as NMR, IR, UV-vis and fluorescence. The fluorescence data revealed that YN-1 showed a 'turn-on' (λ_em = 440 nm) fluorescence response for nanomolar detection of nucleoside triphosphates such as ATP and CTP in 20% HEPES buffer-DMSO solution. YN-1 also showed a concentration-based discrimination between ATP and CTP. YN-1 has been successfully applied for bioimaging of nucleoside triphosphates in MCF-7 live cancer cells with good compatibility. Therefore, the important findings from the present work will provide insight for future development of fluorescent probes to detect various kinds of essential nucleoside triphosphates.

An Electrochemical Aptasensor Integrating Zeolitic Imidazolate Framework for Highly Selective Detection of Bioaerosols

Bioaerosols are the biological materials in the air, which may cause a continuous threat to human health. However, there are many challenges in monitoring bioaerosols such as lack of sensitivity and selectivity. Herein, we synthesized a series of nanohybrids containing zeolitic imidazolate frameworks (ZIFs) and covalent organic frameworks (COFs) to construct an electrochemical aptasensor for detecting adenosine triphosphate (ATP), a biomarker for bioaerosols. The synthesized nanohybrids can not only improve the selectivity of aptasensor because of the original crystal and chemical features of ZIF-67, but also boost its sensitivity due to the excellent conductivity of COFs. After optimizing the nanohybrids, the novel developed sensing platform achieved highly selective detection of ATP with an excellent detection limit of 0.11 nM in a wide linear range from 0.1 nM to 100 nM. Furthermore, this assay was applied to detect bioaerosols in real air samples, and the result showed a positive correlation with that of the culturing-based method, suggesting its potential applicability.

Electrochemical Aptamer Biosensor Based on ATP-Induced 2D DNA Structure Switching for Rapid and Ultrasensitive Detection of ATP

Herein, a two-dimensional (2D) DNA structure with multiple ATP aptamers was elegantly designed to establish an electrochemical biosensor for rapid and sensitive detection of ATP based on ATP-induced structure switching. Concretely, the prepared 2D DNA structure containing numerous ATP aptamers as ATP-specific toehold switches could not only immobilize a large number of methylene blue (MB) for generating a remarkable electrochemical signal, but also greatly increase the local concentration of ATP aptamers to obviously enhance the capture efficiency of ATP. Once the target ATP interacted with the toehold switches, the 2D DNA structure could be sharply collapsed to trigger the burst release of MB from the electrode surface, ultimately resulting in a significantly decreased electrochemical signal for ultrasensitive detection of target ATP over a short period of time. Impressively, by dexterously adjusting the length of the ATP-specific toehold switches to 15-base, optimization of the binding affinity between ATP and the toehold switches was achieved for cutting down the detection time to 30 min and achieving a low detection limit of 0.3 pM, which addressed the shortcoming of time-consuming and poor sensitivity in the previous sensors with a small quantity of ATP aptamers and deficient binding affinity to ATP. Consequently, this strategy opened a promising avenue for ultrasensitive and rapid detection of various biomolecules in biomedical application and disease diagnosis.

Selection, truncation and fluorescence polarization based aptasensor for Weissella viridescens detection

Weissella viridescens is a spoilage bacterium commonly found in low-temperature meat products. In this work, after fifteen rounds including three counter selection rounds of whole-cell systemic evolution of ligands by exponential enrichment (SELEX) in vitro, a novel aptamer L3 that can specifically recognize W. viridescens was obtained with a dissociation constant (K_d) value of 68.25 ± 5.32 nM. The sequence of aptamer L3 was optimized by truncation and a new aptamer sequence TL43 was obtained with a lower K_d value of 32.11 ± 3.01 nM. Finally, a simple and rapid fluorescence polarization (FP) platform was constructed to detect W. viridescens, in which FAM-labeled complementary sequence (FAM-cDNA) was employed to generate FP signal and streptavidin was used to amplify FP signal. In the presence of target bacteria, FP value decreased owning to the dissociation of FAM-cDNA from streptavidin/biotin-TL43/FAM-cDNA complex. Under optimal conditions, the concentration of W. viridescens and FP value displayed a good linear relationship with the detection range from 10² to 10⁶ cfu/mL. Moreover, the designed detection system had a good recovery rate of 90.6%-107.7% in smoked ham samples compared with classical plate counting method, indicating the great potential of the selected and truncated aptamer in practical biosensing applications.

Recent advances in fluorescence anisotropy/polarization signal amplification

Fluorescence anisotropy/polarization is an attractive and versatile technique based on molecular rotation in biochemical/biophysical systems. Traditional fluorescence anisotropy/polarization assays showed relatively low sensitivity for molecule detection, because widespread molecular masses are too small to produce detectable changes in fluorescence anisotropy/polarization value. In this review, we discuss in detail how the potential of fluorescence anisotropy/polarization signal approach considerably expanded through the implementation of mass amplification, recycle the target amplification, fluorescence probes structure-switching amplification, resonance energy transfer amplification, and provide perspectives at future directions and applications.

Molybdenum Disulfide-Based Nanoprobes: Preparation and Sensing Application

The use of nanoprobes in sensors is a popular way to amplify their analytical performance. Coupled with two-dimensional nanomaterials, nanoprobes have been widely used to construct fluorescence, electrochemical, electrochemiluminescence (ECL), colorimetric, surface enhanced Raman scattering (SERS) and surface plasmon resonance (SPR) sensors for target molecules' detection due to their extraordinary signal amplification effect. The MoS₂ nanosheet is an emerging layered nanomaterial with excellent chemical and physical properties, which has been considered as an ideal supporting substrate to design nanoprobes for the construction of sensors. Herein, the development and application of molybdenum disulfide (MoS₂)-based nanoprobes is reviewed. First, the preparation principle of MoS₂-based nanoprobes was introduced. Second, the sensing application of MoS₂-based nanoprobes was summarized. Finally, the prospect and challenge of MoS₂-based nanoprobes in future were discussed.

Applications of hybridization chain reaction optical detection incorporating nanomaterials: A review

The development of powerful, simple and cost-effective signal amplifiers has significant implications for biological research and analysis. Hybridization chain reaction (HCR) has attracted increasing attention because of its enzyme-free, simple, and efficient amplification. In the HCR process, an initiator probe triggered a pair of metastable hairpins through a cross-opening process to propagate a chain reaction of hybridization events, yielding a long-nicked double-stranded nucleic acid structure. To achieve more noticeable signal amplification, nanomaterials, including graphene oxide, quantum dots, gold, silver, magnetic, and other nanoparticles, were integrated with HCR. Various types of colorimetric, fluorescence, plasmonic analyses or chemiluminescence optical sensing strategies incorporating nanomaterials have been developed to analyze various targets, such as nucleic acids, small biomolecules, proteins, and metal ions. This review summarized the recent advances of HCR technology pairing diverse nanomaterials in optical detection and discussed their challenges.

A perylene diimide-based nanoring architecture for exogenous and endogenous ATP detection: biochemical assay for monitoring phosphorylation of glucose

Positively charged amphiphiles hold great significance in supramolecular chemistry due to their good solubility, and physiochemical and molecular recognition properties. Herein, we report the synthesis, characterization and molecular recognition properties of the dicationic amphiphile based on perylene diimide-tyrosine alkyl amide amine (PDI 3). PDI 3 showed the formation of a nanoring architecture in the self-assembled aggregated state (90% H₂O-DMSO mixture) as observed by SEM and TEM studies. The diameter of the nanoring is around 30-50 nm with a height varying from 1 to 2 nm. The self-assembled aggregates of PDI 3 are very sensitive towards nucleoside triphosphates. Upon addition of ATP, PDI 3 showed a decrease in the absorbance and emission intensity at 535 and 580 nm (due to the monomer state), respectively. The lowest detection limit for ATP is 10.8 nM (UV) and 3.06 nM (FI). Upon interaction of ATP with PDI 3, the nanoring morphology transformed into a spherical structure. These changes could be attributed to the formation of ionic self-assembled aggregates between dicationic PDI 3 and negatively charged ATP via electrostatic and H-bonding interactions. The complexation mechanism of PDI 3 and ATP was confirmed by optical, NMR, Job's plot, DLS, SEM and AFM studies. PDI 3 displays low cytotoxicity toward MG-63 cells and can be successfully used for the detection of exogenous and endogenous ATP. The resulting PDI 3 + ATP complex is successfully used as a 'turn-on' biochemical assay for monitoring phosphorylation of glucose.

Framework nucleic acid-wrapped protein-inorganic hybrid nanoflowers with three-stage amplified fluorescence polarization for terminal deoxynucleotidyl transferase activity biosensing

Herein, we proposed a terminal deoxynucleotidyl transferase (TdT), a potential biomarker of lymphoid tumors, responsive fluorescence polarization (FP)- sensing protocol based on framework nucleic acid (FNA)-wrapped protein-inorganic hybrid nanoflowers. To achieve this goal, a pair of poly-A-composed extension primers (EPa and EPb) was designed, and protein-inorganic hybrid nanoflowers were synthesized by a biomineralization reaction. EPa was labeled with carboxyfluorescein (FAM) fluorophore to create the preliminary FP signal. EPb was labeled with biotin to conjugate with hybrid nanoflowers. Upon introduction of TdT into the dTTP pool, both EPa and EPb can be catalyzed by TdT to incorporate numerous T bases, thereby facilitating intermolecular hybridization between 'A' and 'T' bases. The final assembled FNA-wrapped hybrid nanoflowers with greatly enhanced molecular volume and weight restrict the free rotation of attached FAMs, causing a great FP enhancement from a designated three-stage FP amplification. Under optimized conditions, the TdT can be detected with a detection limit of 0.023 U/mL and a linear detection from 0.1 U/mL to 100 U/mL within 20 min. As a proof-of-concept study, the first exploitation of FNA and protein-inorganic nanoflowers to improve the FP signal and the merit of FP without sample separation and washing opens a new avenue for biochemical study and disease diagnosis.

A Novel Electrochemical Aptasensor for the Ultrasensitive Detection of Adenosine Triphosphate Based on DNA-Templated Copolymers

Adenosine triphosphate (ATP) is a small but significant biological molecule that plays an important role in regulating cellular metabolism processes. Accurate and sensitive analytical techniques for detecting ATP are urgently needed. Herein, a new electrochemical aptasensor was designed in light of DNA-templated copolymers that parallel to the electrode for sensitive gauging of ATP. The ATP aptamer decorated by the electronic medium ferrocene can be regarded as a ″bridge″ connecting two DNA-templated copolymers. When ATP exists, because of the extraordinary binding selectivity of DNA-templated copolymers for target ATP, the rapid electron transfer of ferrocene was beneficial to the sensitive detection of target ATP. Specifically, our parallel DNA copolymers are more stable than upright DNA copolymers and have a faster signal transmission because of the close distance to the electrode; meanwhile, the nonspecific pollution is less. Consequently, the developed novel aptasensor exhibited a wide range of linear response toward ATP that was from 0.1 to 10 000 pM and high selectivity with a detection limit down to 11.5 fM. The electrochemical aptasensor has a broad application prospect in the detection of small biological molecules.

An "off-on" electrochemiluminescence biosensor coupled with strand displacement-powered 3D micromolecule walking nanomachine for ultrasensitive detection of adenosine triphosphate

A three-dimensional (3D) micromolecule walking nanomachine propelled by strand displacement was developed to establish a novel switching electrochemiluminescence (ECL) biosensor for ultrasensitive detection of adenosine triphosphate (ATP). Generally, walking nanomachines reported previously were limited to DNA walkers, while the proposed 3D walking nanomachine focused on the micromolecule walker. Firstly, TiO₂ and silver nanoparticles (Ag NPs) functionalized N-(4-aminobutyl)-N-(ethylisoluminol) (Ag-ABEI) were deposited onto the electrode surface to offer an enhanced ECL signal, resulting from the double catalytic effect of TiO₂ and Ag NPs for H₂O₂. Following, dopamine (DA)-labeled DNA duplex probes (S1/S2-DA) immobilized onto the modified electrode cut down the original ECL signal due to the quenching of DA toward ABEI (signal-off). Target ATP walker moved along the 3D DNA track, simultaneously releasing numerous DNA3, which was applied to displace S2-DA, resulting in the quenched ECL intensity recovery (signal-on). As a result, the biosensor showed a low limit of detection down to 0.5 nM (S/N = 3) and was successfully employed to determine ATP in human serum samples. Thus, the established biosensing strategy holds great potential for biochemical studies and clinical diagnosis.

Ex vivo and in vivo fluorescence detection and imaging of adenosine triphosphate

Background

Ex vivo and in vivo detection and imaging of adenosine triphosphate (ATP) is critically important for the diagnosis and treatment of diseases, which still remains challenges up to present.

Results

We herein demonstrate that ATP could be fluorescently detected and imaged ex vivo and in vivo. In particular, we fabricate a kind of fluorescent ATP probes, which are made of titanium carbide (TC) nanosheets modified with the ROX-tagged ATP-aptamer (TC/Apt). In the constructed TC/Apt, TC shows superior quenching efficiency against ROX (e.g., ~ 97%). While in the presence of ATP, ROX-tagged aptamer is released from TC surface, leading to the recovery of fluorescence of ROX under the 545-nm excitation. Consequently, a wide dynamic range from 1 μM to 1.5 mM ATP and a high sensitivity with a limit of detection (LOD) down to 0.2 μM ATP can be readily achieved by the prepared TC/Apt. We further demonstrate that the as-prepared TC/Apt probe is feasible for accurate discrimination of ATP in different samples including living cells, body fluids (e.g., mouse serum, mouse urine and human serum) and mouse tumor models.

Conclusions

Fluorescence detection and imaging of ATP could be readily achieved in living cells, body fluids (e.g., urine and serum), as well as mouse tumor model through a new kind of fluorescent ATP nanoprobes, offering new powerful tools for the treatment of diseases related to abnormal fluctuation of ATP concentration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00930-4.

Novel perylene probe-encapsulated metal-organic framework nanocomposites for ratiometric fluorescence detection of ATP

Adenosine triphosphate (ATP) plays an important role in various biological processes and the ATP level is closely associated with many diseases. Herein, a novel ratiometric fluorescence assay for ATP was developed based on the excimer-monomer transfer of a perylene probe. By encapsulating a perylene probe, N,N'-bis(6-caproic acid)-3,4:9,10-perylenediimide (PDI), into zeolitic imidazolate framework-8 (ZIF-8) nanocrystals, fluorescent nanocomposites (PDI@ZIF-8) with significant excimer emission of the perylene probe were prepared for the first time. The presence of ATP will trigger the decomposition of PDI@ZIF-8 due to much stronger coordination between ATP and Zn2+ than that of 2-methylimidazole and Zn2+. As a result, the encapsulated PDI probes were released, leading to significantly increased monomer emission accompanying the decrease in the excimer emission. The excimer-monomer transition signal was utilized for ratiometric ATP sensing and its potential application for detecting ATP in cell lysates was also successfully demonstrated.

ATP-responsive laccase@ZIF-90 as a signal amplification platform to achieve indirect highly sensitive online detection of ATP in rat brain

A novel electrochemical online system for indirect, highly sensitive and selective online monitoring of ATP in the cerebral microdialysate is presented based on the particular reaction of ATP with zeolitic imidazole framework-90 (ZIF-90) encapsulated laccase microcrystals (laccase@ZIF-90) and the natural catalytic activity of laccase.

A near-infrared-II fluorescence anisotropy strategy for separation-free detection of adenosine triphosphate in complex media

Fluorescence anisotropy (FA) has been widely applied for detecting and monitoring special targets in life sciences. However, matrix autofluorescence restricted its further application in complex biological samples. Herein, we report a near-infrared-II (NIR-II) FA strategy for detecting adenosine triphosphate (ATP) in human serum samples and breast cancer cell lysate, which employed NIR-II fluorescent Ag₂Se quantum dots (QDs) as tags to reduce matrix autofluorescence effect and applied graphene oxide (GO) to enhance fluorescence anisotropy signals. In the presence of ATP, the recognition between NIR-II Ag₂Se QDs labeled aptamer (QD-pDNA) and ATP led to the release of QD-pDNA from GO, resulting in the obvious decrease of FA values. ATP could be quantitatively detected in concentrations ranged from 3 nM to 2500 nM, with a detection limit down to 1.01 nM. This study showed that the developed NIR-II FA strategy could be applied for detecting targets in complex biological samples and had great potential for monitoring interactions between biomolecules in biomedical research.

A dual-function oligonucleotide-based ratiometric fluorescence sensor for ATP detection

Adenosine triphosphate (ATP) is the main energy currency of life that plays a vital role in supporting physiological activities in living organisms, including humans. Therefore, accurate and sensitive detection of ATP concentration is necessary in biochemical research and clinical diagnosis. Herein, a ratiometric fluorescence aptasensor was developed for ATP detection. A dual-function DNA strand comprising an ATP-binding aptamer (ABA) and berberine-binding aptamer (BBA) was designed and optimized, in which ABA can capture ATP and thioflavin T (ThT), whereas BBA can capture berberine. Interestingly, the fluorescence intensity of both berberine and ThT were enhanced as they were captured by this dual-function DNA strand. In the presence of ATP, the ABA on the 3'-end of the DNA bound specifically to its target, causing ThT release and a significant drop in ThT fluorescence. However, ATP had no significant effect on the interaction between berberine and DNA, remaining the enhanced fluorescence intensity of berberine stable. Based on this interesting phenomenon, a ratiometric fluorescence sensor was constructed that used the enhanced fluorescence intensity of berberine as reference to measure the fluorescence intensity of ThT for ATP detection. This ratiometric fluorescence strategy had excellent selectivity and high sensitivity towards ATP with a detection limit (3σ) as low as 24.8 nM. The feasibility of application of this method in biological samples was evaluated in human serum and urine samples, where it exhibited a good detection performance.

One-Step Synthesis of Methylene Blue-Encapsulated Zeolitic Imidazolate Framework for Dual-Signal Fluorescent and Homogeneous Electrochemical Biosensing

In vitro diagnosis requires target biomarkers to be reliably detected at an ultralow level. A dual-signal strategy permits self-calibration to overcome the interferences of experimental and environmental factors, and thus is regarded as a promising approach. However, currently reported works mainly concentrated on the same forms of energy of output signals. Herein, we propose a one-step strategy for synthesis of methylene blue-encapsulated zeolitic imidazolate framework-90 (MB@ZIF-90) with high loading, unique dual-signal property, exceptional recognition capability, and good stability, and we further pioneer MB@ZIF-90 as a dual-signal biosensor for label-free, enzyme-free, and ultrasensitive detection of adenosine triphosphate (ATP) by integration of fluorescence and homogeneous electrochemical techniques. The recognition of MB@ZIF-90 by target ATP spurs the decomposition of ZIF-90, subsequently permitting MB to be released into a supernatant. As compared to the case where ATP does not exist, obviously increased intensities in fluorescence and differential pulse voltammetry current are observed and both signals are directly proportional to ATP concentrations. Thus, the MB@ZIF-90-based biosensor achieved dual-signal detection of ATP in an ultrasensitive manner and displayed a more reliable diagnosis result than previously reported ATP biosensors. This dual-signal strategy provides a new opportunity to develop high-performance biosensors for in vitro diagnosis and demonstrates great potential for future applications in bioinformatics and clinical medicine.

Aptamer binding assays and molecular interaction studies using fluorescence anisotropy - A review

Binding of nucleic acid aptamers to specific targets and detection with fluorescence anisotropy (FA) or fluorescence polarization (FP) take advantage of the complementary features of aptamers and the fluorescence techniques. We review recent advances in affinity binding assays using aptamers and FA/FP, with an emphasis on studies of molecular interactions and identification of binding sites. Aptamers provide several benefits, including the ease of labelling fluorophores on specific sites, binding-induced changes in aptamer structures, hybridization of the aptamers to complementary sequences, changes in molecular volume upon binding of the aptamer to its target, and adsorption of aptamers onto nanomaterials. Some of these benefits have been utilized for FA/FP assays. Once the aptamer binds to its target, the resulting changes in molecular volume (size), structure, local rotation of the fluorophore, and/or the fluorescence lifetime influence changes to the FA/FP values. Measurements of these fluorescence anisotropy/polarization changes have provided insights into the molecular interactions, such as the binding affinity and the site of binding. Studies of molecular interactions conducted in homogeneous solutions, as well as those with separations, e.g., capillary electrophoresis, have been summarized in this review. Studies on mapping the position of binding in aptamers at the single nucleotide level have demonstrated a unique benefit of the FA/FP techniques and pointed to an exciting direction for future research.

Application of DNA nanodevices for biosensing

Deoxyribonucleic acid (DNA), the carrier of genetic information in living life, is an essential biomacromolecule in almost all living systems. DNA has advantages including, programmability, predictability, high rigidity, and stability. Through self-assembly or combination with other nanomaterials (such as gold nanoparticles, graphene oxides, quantum dots, and polymers), DNA can be applied to construct specific, stable, biocompatible, and functional nanodevices. DNA nanodevices have made greater contributions in a plethora of fields. In this review, we discuss the recent progress of DNA nanodevices in molecular detection and analysis. Meanwhile, we prospect the development of various DNA devices in biological analysis, clinical diagnosis and biomedical research.

Design of a Fluorescence Turn-on and Label-free Aptasensor Using the Intrinsic Quenching Power of G-Quadruplex to AMT

A novel fluorescent aptasensor based on the G-quadruplex induced fluorescent quenching of psoralen and the competitive interactions between 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT), adenosine triphosphate (ATP) and G-rich DNA functionalized split ATP aptamer was proposed. The binding of ATP to the G-rich DNA functionalized split aptamer induced a significant enhancement in fluorescence emission intensity while undergoing excitation at 340 nm. Under the optimal conditions, the developed aptasensor showed high selectivity and good accuracy for detecting ATP. The practicality of the proposed aptasensor has been confirmed by successfully analyzing ATP in spiked human blood serum samples with satisfactory results. As far as we know, this is the first time that the intrinsic quenching ability of G-quadruplex was applied to simply construct a fluorescence turn-on and label-free aptasensor. On account of the superiority of the simplicity of the design strategy, more work is expected in the future to develop a variety of novel sensors for other important analytes using the quenching capability of G-quadruplex through reasonable designs.

Adenosine triphosphate responsive metal-organic frameworks equipped with a DNA structure lock for construction of a ratiometric SERS biosensor

A novel ratiometric surface-enhanced Raman scattering (SERS) biosensor was constructed based on stimuli-responsive DNA functionalized metal organic frameworks (MOFs) for detection of adenosine triphosphate (ATP). As a result, the detection range of ATP was 1 nM to 200 nM with a detection limit of 0.4 nM. The ratiometric SERS biosensor strategy offers a lower detection limit and exhibits a more enhanced performance than the typical SERS detection based on single signal response, which may have potential for detection of other biomolecules or metal ions.

Coupling aptazyme and catalytic hairpin assembly for cascaded dual signal amplified electrochemiluminescence biosensing

Developing reliable and sensitive detection methods for adenosine triphosphate (ATP) is vital for both clinical diagnosis and food safety. In this work, by coupling aptazyme- and catalytic hairpin assembly (CHA)-based signal amplification and electrochemiluminescence (ECL), an ultrasensitive biosensor for sensing ATP was fabricated using Ru(bpy)₃²⁺-doped silica nanoparticles (RuSiO₂) as ECL probes and a ferrocene-functionalized hairpin DNA (hairpin-Fc) as quencher. The aptazyme-triggered cleavage of the DNA substrate and the CHA reaction both led to the circular release of trigger DNA, resulting in a significant dual signal amplification, with unprecedented enhancement up to 940-fold. Moreover, the bioconjugation of the DNA substrate with Au@Fe₃O₄ facilitated the separation and purification of the released trigger DNA, and effectively reduced the background signal. As a result, the as-prepared ECL biosensor exhibited a much lower detection limit of 0.054 pM for ATP, compared to those in previous reports, and showed high reliability for ATP detection in both spiked serum samples and Staphylococcus aureus. This work offers a new perspective for designing nucleic acid-based signal amplification for detecting ATP in bacterial analysis and clinical diagnosis.

A label-free hairpin aptamer probe for colorimetric detection of adenosine triphosphate based on the anti-aggregation of gold nanoparticles

A facile and rapid colorimetric approach was described for selective and sensitive determination of adenosine triphosphate (ATP) based on a hairpin aptamer probe and the anti-aggregation of AuNPs. Poly(diallyldimethylammonium chloride) (PDDA) can induce the aggregation of AuNPs due to the electrostatic interaction causing a red to blue color change. Upon the addition of ATP, aptamer-based hairpin probe is opened and releases flexible ssDNA ends. The released flexible ssDNA ends can interact with PDDA and prevent PDDA-induced AuNPs aggregation. Thus, a visible color change from blue to red and a decrease in the absorption ratio (A₆₁₀/A₅₂₀) are observed. Under the optimal conditions, the hairpin aptamer-based colorimetric assay exhibits high sensibility and selectivity for the detection of ATP with a detection limit of 1.7nM. Moreover, this assay is successfully used in the rapid determination of ATP in spiked human serum samples with good recoveries in the range of 102.88 to 104.07%.