Ultrasensitive Fluorescence Detection Research Articles

Design, synthesis, solvatochromism, and colorimetric detection of amines based on isolated perylene bisimide anionic radical π-dimers

Some π-molecular radicals typically exist in solution as π-dimers with metastable characteristics. Therefore, attempting to improve the stability of radical π-dimers is a fascinating endeavor. Herein, a series of hydroxyl-functionalised isolated perylene bisimide anionic radical π-dimers were obtained by using intramolecular hydrogen bond assistance in a one-step process for the first time. It is also found that these radical π-dimers exhibit solvatochromism and acid-base discoloration, when the intermolecular hydrogen bonds are disrupted. Perylene bisimide anionic radical π-dimers exhibit unique properties such as solvatochromism and acid-base discoloration. These characteristics make them suitable for ultra-sensitive colorimetric and fluorescent dual-signal detection of amines. Among them the π-dimer 3 achievable the lowest detection limits of 0.13 ppb, 0.02 ppb and 0.049 ppb for primary, secondary and tertiary amines, respectively. Additionally, colorimetric films prepared using these radical π-dimers demonstrate high sensitivity, enabling detection of amines at ppb levels. We believe that this class of radical π-dimers could be develop into a new class of environmental stimuli-responsive materials.

Ultrasensitive Fluorescence Detection of Ascorbic Acid Using Silver Ion-Modulated High-Quality CdSe/CdS/ZnS Quantum Dots.

Improving the sensitivity of the fluorescence method for the detection of bioactive molecules is crucial in biochemical analysis. In this work, an ultrasensitive sensing strategy was constructed for the detection of ascorbic acid (AA) using high-quality 3-mercaptopropionic acid-capped CdSe/CdS/ZnS quantum dots (MPA-CdSe/CdS/ZnS QDs) as the fluorescent probe. The prepared water-soluble QDs exhibited a high photoluminescence quantum yield (PL QY) of up to 96%. Further, the fluorescence intensity of the QDs was intensively quenched through the dynamic quenching of Ag+ ions due to an efficient photoinduced electron transfer progress. While the existence of AA before adding Ag+ ions, Ag+ ions were reduced. Thus, the interaction of the QDs and Ag+ ions was destroyed, which led to the fluorescence distinct recovery. The detection limit of AA could be as low as 0.2 nM using this sensing system. Additionally, most relevant small molecules and physiological ions had no influence on the analysis of AA. Satisfactory results were obtained in orange beverages, showing its great potential as a meaningful platform for highly sensitive and selective AA sensing for clinical analysis.

Ultrahigh-Speed 3D DNA Walker with Dual Self-Protected DNAzymes for Ultrasensitive Fluorescence Detection and Intracellular Imaging of microRNA.

Herein, a dual self-protected DNAzyme-based 3D DNA walker (dSPD walker), composed of activated dual self-protected walking particles (ac-dSPWPs) and track particles (TPs), was constructed for ultrasensitive and ultrahigh-speed fluorescence detection and imaging of microRNAs (miRNAs) in living cells. Impressively, compared with the defect that "one" target miRNA only initiates "one" walking arm of the conventional single self-protected DNAzyme walker, the dSPD walker benefits from the secondary amplification and spatial confinement effect and could guide "one" target miRNA to generate "n" secondary targets, thereby initiating "n" nearby walking strands immediately, realizing the initial rate over one-magnitude-order faster than that of the conventional one. Moreover, in the process of relative motion between ac-dSPWPs and TPs, the ac-dSPWPs could cleave multiple substrate strands simultaneously to speed up movement and reduce the derailment rate, as well as combine with successive TPs to facilitate a large amount of continuous signal accumulation, achieving an ultrafast detection of miRNA-221 within 10 min in vitro and high sensitivity with a low detection limit of 0.84 pM. In addition, the DNA nanospheres obtained by the rolling circle amplification reaction can capture the Cy5 fluorescence dispersed in liquids, which achieves the high-contrast imaging of miRNA-221, resulting in further ultrasensitive imaging of miRNA-221 in cancer cells. The proposed strategy has made a bold innovation in the rapid and sensitive detection as well as intracellular imaging of low-abundance biomarkers, offering promising application in early diagnosis and relevant research of cancer and tumors.

Electrophilicity Modulation for Sub-ppm Visualization and Discrimination of EDA.

Precise and timely recognition of hazardous chemical substances is of great significance for safeguarding human health, ecological environment, public security, etc., especially crucial for adopting appropriate disposition measures. Up to now, there remains a practical challenge to sensitively detect and differentiate organic amines with similar chemical structures with intuitive analysis outcomes. Here, a unique optical probe with two electrophilic recognition sites for rapid and ultra-sensitive ratiometric fluorescence detection of ethylenediamine (EDA) is presented, while producing distinct fluorescence signals to its structural analog. The probe exhibits ppb/nmol level sensitivity to liquidous and gaseous EDA, specific recognition toward EDA without disturbance to up to 28 potential interferents, as well as rapid fluorescence response within 0.2 s. By further combining the portable sensing chip with the convolutional algorithm endowed with image processing, this work cracked the problem of precisely discriminating the target and non-targets at extremely low concentrations.

A novel dual-mode aptasensor based on a multiple amplification system for ultrasensitive detection of lead ions using fluorescence and surface-enhanced Raman spectroscopy.

In this work, we develop a dual recycling amplification aptasensor for sensitive and rapid detection of lead ions (Pb2+) using fluorescence and surface-enhanced Raman scattering (FL-SERS). The aptasensor allows targeted cleavage of substrates through specifically binding with the Pb2+-dependent aptamer (M-PS2.M). Ultrasensitive detection of trace Pb2+ has been achieved using an enzyme-free nonlinear hybridization chain reaction (HCR) and the FL-SERS technique. The lower limit of detection (LOD = 3σ/k) is 0.115 pM in FL mode and 1.261 fM in SERS mode. The aptasensor is characterized by high reliability and specificity, among other things, to distinguish Pb2+ from other metal ions. In addition, the aptasensor can detect Pb2+ in actual water with good recovery. Compared with the single-mode aptasensor, the dual-mode aptasensor is characterized by high reliability, an extensive detection range, and high specificity.

Ultra-sensitive fluorescent detection of strychnine based on carbon dot self-assembled gold nanocage sensing probe.

The ultra-sensitive detection of strychnine is crucial to provide powerful evidence in strychnine poisoning cases. In this study, a novel fluorescent carbon dots (CDs) self-assembled gold nanocage (AuNCs) composite is synthesized for the ultra-sensitive detection of strychnine using molecularly imprinted polymer sensing technology (MIPs-CDs@AuNCs). With strong loading and delivery capability of AuNCs, the CDs could be loaded into AuNCs, where the anisotropy of CDs could significantly decrease and the fluorescence of the MIPs-CDs@AuNCs probe gained lower relative standard deviation (RSD). Moreover, the fluorescence response of MIPs-CDs@AuNCs to target strychnine was observed to be more significant than MIPs-CDs without gold nanocages. Under optimal conditions, the developed MIPs-CDs@AuNCs fluorescence strategy showed good linear relationship at the concentration of strychnine from 3 ng mL-1 to 200 ng mL-1 with the limit of detection as low as 1 ng mL-1. Besides, real blood samples were analyzed without complex pre-preparation procedure to investigate the performance of the proposed molecularly imprinted fluorescence probe, and satisfactory results were obtained with absolute deviations between -1.16 ng mL-1 and 1.28 ng mL-1, which exhibited a great potential for the detection of strychnine in health care work.

Molecularly imprinted polymer-coated hybrid optical waveguides for sub-aM fluorescence sensing.

The sensitivity of fluorescent sensors is crucial for their applications. In this study, we propose a molecularly imprinted polymer (MIP)-coated optical fibre-hybrid waveguide-fibre sensing structure for ultrasensitive fluorescence detection. In such a structure, the MIP coated-hybrid waveguide acts as a sensing probe, and the two co-axially connected optical fibres act as a highly efficient probing light launcher and a fluorescence signal collector, respectively. For the dual-layered waveguide sensing probe, the inner hybrid waveguide core was fabricated using a hollow quartz nanoparticle-hybridized polymer composite with a low refractive index, and the outer MIP coating layer possesses a high refractive index. Simulations showed that this dual-layer configuration can cause light propagation from the waveguide core to the MIP sensing layer with an efficiency of 98%, which is essential for detection. To validate this concept, we adopted a popular fluorescent dye, rhodamine B, to evaluate the sensing characteristics of the proposed system. We achieved an extremely low limit of detection of approximately 1.3 × 10-19 g ml-1 (approximately 0.27 aM).

Ultrasensitive fluorescence detection of gonyautoxins in seawater using a novel molecularly imprinted nanoprobe

Gonyautoxins (GTXs), a group of potent neurotoxins belonging to paralytic shellfish toxins (PSTs), are often associated with harmful algal blooms of toxic dinoflagellates in the sea and represent serious health and ecological concerns worldwide. In the study, a highly selective and sensitive fluorescence nanoprobe was constructed based on photoinduced electron transfer recognition mechanism to rapidly detect GTXs in seawater, using specific entrapment of molecularly imprinted polymers (MIPs) combined with fluorescence analyses. The green emissive fluorescein isothiocyanate was grafted in a silicate matrix as a signal transducer and fluorescence intensity of the nanoprobe with a core-shell structure exhibited a strong enhancement due to efficient analyte blockage in a short response time. Under optimal conditions, the developed MIPs nanoprobe presented an excellent analytical performance for spiked seawater samples including a recovery from 94.44 % to 98.23 %, a linear range between 0.018 nmol L−1 and 0.36 nmol L−1, as well as good accuracy. Furthermore, the method had extremely high sensitivity, with limit of detection obtained as 0.005 nmol L−1 for GTXs and GTX2/3. Finally, the nanoprobe was applied for the determination of GTXs in seven natural seawater samples with GTXs mixture (0.035–0.058 nmol L−1) or single GTX2/3 (0.033–0.050 nmol L−1), and the results agreed well with those of a UPLC-MS/MS method. The findings of our study suggest that the constructed MIPs-based fluorescence enhancement nanoprobe was suitable for rapid, selective and ultrasensitive detection of GTXs, particular GTX2/3, in natural seawater samples.

FADH2-mediated radical polymerization amplification for microRNA-21 detection

For early diagnosis of disease, ultrasensitive mircoRNA-21 detection has considerable potential. In this paper, an ultra-sensitive fluorescence detection method for microRNA was developed by atom transfer radical polymerization (ATRP). This ATRP reaction was first initiated by using flavin mononucleotide (FADH2). The DNA probe 1 modified with amino group was fixed on the magnetic nanoparticle Fe3O4, and microRNA-21 was added to form the probe 1-microRNA-21. Another carboxy-modified DNA 2 forms a sandwich structure with the bound microRNA-21. Two terminally modified DNA types are used as microRNA probes, using complementary base pairing to form a stable super-sandwich structure between the DNA probe and the microRNA. Under optimal conditions, microRNA was detected in PBS buffer with a detection limit of 0.19 fM. And even in 10% of human serum, microRNA-21 can be detected with a detection limit of 47.8 fM. Results show that this method has high selectivity, efficiency and stability, which broad application prospect in microRNA ultra-sensitive detection.

A Cascade Signal Amplification Strategy for the Ultrasensitive Fluorescence Detection of Cu2+ via λ-Exonuclease-Assisted Target Recycling with Mismatched Catalytic Hairpin Assembly.

Herein, an ultrasensitive DNAzyme-based fluorescence biosensor for detecting Cu2+ was designed using the cascade signal amplification strategy, coupling λ-exonuclease-assisted target recycling and mismatched catalytic hairpin assembly (MCHA). In the designed detection system, the target, Cu2+, can activate the Cu2+-dependent DNAzyme to cause a cleavage reaction, releasing ssDNA (tDNA). Then, tDNA binds to hairpin DNA (H0) with an overhanging 5'-phosphorylated terminus to form dsDNA with a blunt 5'-phosphorylated terminus, which activates the dsDNA to be digested by λ-Exo and releases tDNA along with another ssDNA (iDNA). Subsequently, the iDNA initiates MCHA, which can restore the fluorescence of carboxyfluorescein (FAM) previously quenched by tetramethylrhodamine (TAMRA), resulting in a strong fluorescent signal. Furthermore, MCHA efficiently improves the signal-to-noise ratio of the detection system. More importantly, tDNA recycling can be achieved with the λ-Exo digestion reaction to release more iDNA, efficiently amplifying the fluorescent signal and further improving the sensitivity to Cu2+ with a detection limit of 60 fM. The practical application of the developed biosensor was also demonstrated by detecting Cu2+ in real samples, proving it to be an excellent analytical strategy for the ultrasensitive quantification of heavy metal ions in environmental water sources.

Cu2+-functionalized Zr-MOF triggers O-phenylendiamine oxidation for ultrasensitive ratiometric fluorescence detection of nerve agent simulant

Developing a fluorescence sensor capable of precisely identifying highly toxic nerve agents has become a focus of research, given that they are easily available and can be used by terrorists to threaten the security of the world. In this work, we designed a ratiometric fluorescence sensing platform with Cu2+-modified UiO-66-NH2 (Cu2+@UiO-66-NH2) and o-phenenediamine (OPD) as signal indicators and successfully used for the liquid and gas detection of the nerve agent simulant diethyl chlorophosphate (DCP). UiO-66-NH2 obtained oxidase activity by simple Cu2+ modification, which catalyzed the oxidation of OPD to give a yellow fluorescent product 2, 3-diaminophenazine (DAP). In this detection system, the fluorescence of UiO-66-NH2 was greatly enhanced by blocking the ligand metal charge transfer (LMCT) process inside the framework by DCP. At the same time, the amino group of DAP was phosphorylated by DCP, and the attenuation of DAP fluorescence was observed by the static quenching effect. In addition, the Cu2+@UiO-66-NH2/OPD loaded agarose hydrogel device can be used to detect DCP vapor with naked eyes and showed satisfactory detection result (LOD: 6.65 ppb).

Dual-layer 3D DNA nanostructure: The next generation of ultrafast DNA nanomachine for microRNA sensing and intracellular imaging

The working efficiency of traditional 3D DNA nanomachines is extremely restricted due to the complex DNA components modified on nanoparticles in the same spatial height. Herein, an ultrafast dual-layer 3D DNA nanomachine (UDDNM) based on catalytic hairpin assembly (CHA) was developed by assembling two different lengths of hairpin DNA on the surface of gold nanoparticles, the long hairpin 1 (H1), to capture the trigger, and the short hairpin 2 (H2), as the signal probe, to recycle the trigger. Compared to the traditional single-layer 3D DNA nanomachine, the dual-layer 3D DNA nanostructure greatly enhances the effective collision between trigger and targeted DNA probe, H1, since the H1 located in outer layer would react with the trigger, inhibiting the invalid collision between the trigger and residual DNA component, H2, and remarkably decreasing the steric hindrance associated with the nucleic acids layer around the nanoparticles. Especially, when the distance of two layers was fixed at 3 nm, the corresponding UDDNM could accomplish the overall reaction only in 3 min with a dramatically high initial rate of up to 5.93 × 10−7 M s−1, which was at least 5-fold beyond that of the typical single-layer 3D DNA nanomachines. As a proof of concept, the described UDDNM was successfully applied in ultrasensitive fluorescence detection and sensitive intracellular imaging of miRNA-21. Consequently, our strategy, based on the creation of dual-layer 3D DNA nanostructure, may create a new approach to designing the next generation of DNA nanomachine and has enormous potential for applications in bio-analysis, logic gate operations, and clinical diagnoses.

Tannic acid-accelerated fenton chemical reaction amplification for fluorescent biosensing: The proof-of-concept towards ultrasensitive detection of DNA methylation

As a promising biomarker, the level of methylated DNA usually changes in the early stage of the cancer. Ultrasensitive detection of the changes of methylated DNA offers possibility for early diagnosis of cancer. In this work, a tannic acid-accelerated Fenton chemical reaction amplification was firstly proposed for the construction of ultrasensitive fluorescent assay. Tannic acid was used as reductant to accelerate Fenton reaction procedure through the conversion of Fe3+/Fe2+, generating hydroxyl radicals (·OH) continuously. The produced ·OH oxidized massive non-fluorescent terephthalic acid (TA) to fluorescent-emitting hydroxy terephthalic acid (TAOH). In this way, the fluorescent signal could be greatly enhanced and the sensitivity was improved almost 116 times. The proposed signal amplification strategy was further applied to detect of DNA methylation with the assistance of liposome encapsulated with tannic-Fe3+ complexes. The methylated DNA was firstly captured through the hybridization with its complementary DNA that were pre-modified in the 96-well plate via the combination between streptavidin (SA) and biotin. Then, 5 mC antibody on the surface of liposomes specially recognized and combined with methylation sites, which brought large amount of tannic-Fe3+ complexes to participate Fenton reaction. The fluorescence of generated TAOH was depended on the concentration of methylated DNA. The assay showed good analytical performance for methylated DNA with a limit of detection (LOD) of 1.4 fM. It's believed that tannic acid-accelerated Fenton chemical reaction amplification strategy provides a promising platform for ultrasensitive fluorescent detection of low abundant biomarkers.

Beyond carbon dots: Intrinsic reducibility in Ti3C2 MXene quantum dots induces ultrasensitive fluorescence detection and scavenging of Mn(VII)

Recently, cutting two-dimension MXenes into quantum dots (QDs) becomes a hotspot due to the introduction of photoluminescence properties with concomitantly extensive applications. However, it is still a challenge to utilize MXene QDs (MQDs) for the simultaneous detection and scavenging heavy metal ions that may threaten environment safety and human health. Herein, MQDs are prepared by hydrothermal treatment of Ti3C2 MXene in the presence of ethylenediamine and oxidized by H2O2 to obtain carbon dots (CDs). These MQDs and CDs with various functional groups show excellent dispersibility, small size (less than 10 nm), good fluorescence, and high stability. Then, Ti3C2 MQDs are firstly utilized to establish the fluorescent probe towards Mn(VII) with limit of detection (LOD) as low as 5.2 nM. The ultrasensitive selectivity of Ti3C2 MQDs is attributed to their inherent reducibility, which can cause the redox reaction between Ti3C2 MQDs and Mn(VII) with precipitous fluorescence quenching and elimination of Mn(VII). After the lack of reducibility, CDs show selective response to Mn(VII) with LOD of 230 nM based on synergistic inner-filter effect (IFE) and static quenching. Furthermore, the MQDs are successfully applied as a dual functional platform to evaluate the level of Mn (VII) and scavenge it in plant leaves. The comparation of MQDs and CDs for Mn(VII) detection and scavenging will bring more inspiration about intrinsic properties of QDs derived from MXenes for their composite material design and multifunctional use.

Ultrasensitive fluorescence detection of multiple DNA methyltransferases based on DNA walkers and hyperbranched rolling circle amplification

The accurate and ultrasensitive detection of multiple methyltransferases was in great request for clinical diagnosis and epigenetic therapy. Here, a novel fluorescence assay was proposed for ultrasensitive CpG methyltransferase (M.SssI) and DNA adenine methyltransferase (Dam) activity detection based on hyperbranched rolling circle amplification (HRCA) and DNA walkers. The biosensor showed an extremely high sensitivity due to the dual-amplification strategy of HRCA and DNA walker. The LOD of the biosensor for M.SssI and Dam methyltransferase was estimated at 0.0004 U/mL and 0.001 U/mL, respectively. Without the presence of M.SssI methyltransferase, the corresponding recognition site of hairpin HM was cleaved by HpaII endonuclease, generating a DNA fragment (T-DNA) and inducing the DNA walker-HRCA reaction. Since the HRCA products contained numerous double-strand DNA (dsDNA), SYBR Green I could be embedded in the dsDNA, leading to a high fluorescent signal. In the presence of M.SssI methyltransferase, the corresponding recognition site of hairpin HM was methylated and the HpaII endonuclease-catalyzed stem of hairpin HM dissociation was hindered, leading to no DNA fragment (T-DNA) present. Hence, the DNA walker-HRCA reaction was not initiated and the fluorescent signal of SYBR Green I remained at a low level. Similarly, DNA adenine methyltransferase (Dam) and its inhibitors could also be detected by redesigning hairpin HD with the Dam recognition sequences. Furthermore, the sensing system was applied to analyze the endogenic Dam methyltransferase in the real samples such as E. coli cell lysate.

Bidirectional motivated bimodal isothermal strand displacement amplifier with a table tennis-like movement for the ultrasensitive fluorescent and colorimetric detection of depression-related microRNA.

An increasing number of studies have highlighted the potential of microRNAs (miRNAs) as physiological indicators of major depressive disorder (MDD). Herein, we developed a bidirectional-motivated bimodal isothermal strand displacement amplifier (BB-ISDA) for the ultrasensitive fluorescent and colorimetric detection of MDD-related miRNA-132. In the BB-ISDA system, a pair of functionalized hairpin probes (HP1 and HP2) with nicking recognition sites are designed to recognize target miRNA. The recognition of target miRNA by HP1 (or HP2) generates copious numbers of nicked triggers by HP1 (or HP2)-based ISDA to recognize HP2 (or HP1) by autonomous strand polymerization, cleavage, and displacement, which in turn induces the subsequent generation of copious numbers of nicked G-quadruplex triggers by HP2 (or HP1)-based ISDA to recognize HP1 (or HP2) along a same line. After many cycles, this bidirectional motivated table-tennis-like movement amplifies the fluorescent signal from HP1 and the colorimetric signal from HP2, simultaneously. The dual-signal output pattern was cross-validated for sensing miRNA-132. Each of the detection modal shows the capability for qualitative and quantitative detection of miRNA-132 with high sensitivity and specificity. The adaptability of the bimodal mechanism was verified via the detection of target miRNA-132 from clinical human blood samples. We envision that this BB-ISDA with dual-signal output for accurate and reliable analysis of miRNA is promising for the molecular diagnosis of human mental diseases.

A facile enzyme-assisted multiple recycling amplification strategy for ultrasensitive fluorescence detection of HIV-1 DNA

We developed an enzyme-assisted multiple signal amplification reaction for target nucleic acid detection. In this strategy, the target nucleic acid as triggers, and in the presence of two specific primers, DNA polymerase and DNA nicking endonuclease act in concert to promote the repetitive cycle DNA replication process, leading to an exponential increase in nucleic acid sequence. Both ends of each sequence of the amplification products and the specific primer could from a unit of Mg2+-DNAzyme which in the presence of cofactor Mg2+ could recognize and cyclically cleave the hairpin probes in the solution and thus realize real-time fluorescence detection of HIV-1 DNA. Under optimal conditions, the detection limit of this method is 10−17 M. The simple in design, isothermal conditions and easy fluorescence measurement of this method exhibits superior sensitivity and specificity, and thus holds great potential to be a promising assay for quantitative detection of DNA or RNA in theoretical and clinic studies.

A label-free fluorescent aptasensor based on a novel exponential rolling circle amplification for highly sensitive ochratoxin A detection

Rapid and sensitive analysis of ochratoxin A (OTA) plays an important role in food safety. Here, an aptasensor based on novel exponential rolling circle amplification (ERCA) was proposed for ultrasensitive and label-free fluorescence detection of OTA. The attachment of OTA to its aptamer could release H and rapidly hybridize with CT to initiate rolling circle amplification (RCA). The amplicons could further displace H from APH to initiate recycled RCA, achieving exponential growth of amplification products that contained G4 dimers for lighting up ThT. Benefiting from the exponential amplification efficiency of the ERCA strategy and the high fluorescence quantum yield of G4 dimer/ThT, this strategy exhibited a wide linear range from 10 fg/mL to 10 ng/mL with a detection limit of 4.3 fg/mL. In addition, the aptasensor displayed satisfactory recoveries in real sample analysis. We believe that this novel aptasensor possesses promising application prospects in food safety and medicine detection.

ALP-assisted chemical redox cycling signal amplification for ultrasensitive fluorescence detection of DNA methylation.

Affinity assays allow direct detection of DNA methylation events without requiring a special sequence. However, the signal amplification of these methods heavily depends on nanocatalysts and bioenzymes, making them suffer from low sensitivity. In this work, alkaline phosphatase (ALP)-assisted chemical redox cycling was employed to amplify the sensitivity of fluorescence affinity assays for DNA methylation detection using Ru@SiO2@MnO2 nanocomposites as fluorescent probes. In the ALP-assisted chemical redox cycling reaction system, ALP hydrolyzed 2-phosphate-L-ascorbic acid trisodium salt (AAP) to produce AA, which could reduce MnO2 nanosheets to form Mn2+, making the fluorescence recovery of Ru@SiO2 nanoparticles possible. Meanwhile, AA was oxidized to dehydroascorbic acid (DHA), which was re-reduced by tris(2-carboxyethyl) phosphine (TCEP) to trigger a redox cycling reaction. The constantly generated AA could etch large amounts of MnO2 nanosheets and greatly recover Ru@SiO2 fluorescence, amplifying the signal of the fluorescence assay. Employing the proposed ALP-assisted chemical redox cycling signal amplification strategy, a sensitive affinity assay for DNA methylation detection was achieved using ALP encapsulated liposomes that were linked with the 5mC antibody (Ab) to bind with methylated sites. A detection limit down to 2.9 fM was obtained for DNA methylation detection and a DNA methylation level as low as 0.1% could be distinguished, which was superior to conventional affinity assays. Moreover, the affinity assays could detect DNA methylation more specifically and directly, implying their great potential for the analysis of tumor-specific genes in liquid biopsy.

Ultrasensitive fluorescence detection of nitro-explosives by dihydro-oxoisobenzofuranyl-phthalazinone obtained from the Cd(ii)-catalyzed cyclization of azinodimethylidyne-benzoic acid

Ultrasensitive detection of nitroexplosives is accomplished by utilizing the fluorescent probe dihydro-oxoisobenzofuranyl-phthalazinone obtained from the Cd(ii)-catalyzed cyclization of azinodimethylidyne-benzoic acid.