Search

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged as a novel pathogen in 2019. The virus is responsible for a severe acute respiratory syndrome outbreak, affecting the respiratory system of infected individuals. COVID-19 is a super amplifier of basic diseases, and the disease with basic diseases is often more serious. Controlling the spread of the COVID-19 pandemic relies heavily on the timely and accurate detection of the virus. To resolve the problem, a polyaniline functionalized NiFeP nanosheet array-based electrochemical immunosensor using Au/Cu2O nanocubes as a signal amplifier is fabricated for the detection of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP). Polyaniline (PANI) functionalized NiFeP nanosheet arrays are synthesized as an ideal sensing platform for the first time. PANI is coated on the surface of NiFeP by electropolymerization to enhance biocompatibility, beneficial for the efficient loading of the capture antibody (Ab1). Significantly, Au/Cu2O nanocubes possess excellent peroxidase-like activity and exhibit outstanding catalytic activity for the reduction of H2O2. Therefore, Au/Cu2O nanocubes combine with a labeled antibody (Ab2) through the Au–N bond to form labeled probes, which can effectively amplify current signals. Under optimal conditions, the immunosensor for the detection of SARS-CoV-2 NP shows a wide linear range of 10 fg mL−1–20 ng mL−1 and a low detection limit of 1.12 fg mL−1 (S/N = 3). It also exhibits desirable selectivity, repeatability, and stability. Meanwhile, the excellent analytical performance in human serum samples confirms the practicality of the PANI functionalized NiFeP nanosheet array-based immunosensor. The electrochemical immunosensor based on the Au/Cu2O nanocubes as a signal amplifier demonstrates great potential for application in the personalized point-of-care (POC) clinical diagnosis. [ABSTRACT FROM AUTHOR]

Detection of tumor biomarkers is of great significance for early diagnosis of cancer. Herein, we fabricated a novel lab-on-a chip surface-enhanced Raman scattering (SERS) (LoC-SERS) biosensing platform for highly sensitive and specific detection of thrombin and platelet-derived growth factor-B (PDGF-B) using aptamer recognition technology. This strategy relies on the specific aptamer recognition between SERS probes (Ag–Au core–shell nanorods (Ag–AuNRs) modified with Raman reporter molecules and detection aptamer) and SERS capture substrate (Au nanoflower (AuNF) substrates modified with capture aptamer), which significantly amplify the plasmonic coupling effect that allows the ultrasensitive and high specificity SERS detection. The limits of detection (LODs) are as low as 3.62 fM for thrombin and 2.86 fM for PDGF-B. Such LoC-SERS platform is further employed to simultaneously detect two types of gastric carcinoma-related with high sensitivity and specificity, which meanwhile exhibit robust capacity of resisting disturbance in practical samples. The results revealed that the present LoC-SERS platform displayed excellent analytical performance, including superior reproducibility, specificity, and sensitivity. Satisfactory results were obtained in real sample analysis with the LoC-SERS platform. [ABSTRACT FROM AUTHOR]

A novel surface-enhanced Raman scattering and lateral flow assay (SERS–LFA) biosensor with multiple channels based on an aptamer has been proposed in this work. The developed biosensor was designed for the rapid, convenient, sensitive and specific detection of vascular endothelial growth factor (VEGF) and osteopontin (OPN) in several samples simultaneously. During the assay, VEGF and OPN were recognized by detection aptamers immobilized on cuprous oxide nanocubes (Cu2O NCs) and captured by capture aptamers to form a sandwich structure on the test lines. In this way, generous numbers of "hot spots" formed by the aggregation of Cu2O NCs remarkably enhanced the SERS signals of Raman reporters (NBA and 4-ATP). The detection limits were as low as 0.78 pg mL−1 for the VEGF and 0.86 pg mL−1 for OPN in the human serum within 15 min, respectively. Additionally, the biosensor possesses favorable specificity, reproducibility, uniformity and stability. In the clinical analysis of serum specimens, patients with cervical cancer can be differentiated from healthy volunteers. Consequently, the presented aptamer-based SERS–LFA biosensor with multiple channels provides a powerful tool for the early diagnosis of cervical cancer. [ABSTRACT FROM AUTHOR]

In this study, we apply catalytic hairpin assembly (CHA) as the signal amplification strategy for the quantification of carcinoembryonic antigen (CEA) and cytokeratin fragment antigen 21-1 (CYFRA21-1) with a surface-enhanced Raman scattering (SERS) microfluidic chip (LoC-SERS) as the carrier. Herein, antibody–DNA conjugates are designed to assist the application of CHA amplification in protein detection. In the presence of protein biomarkers, antibody–DNA conjugates can specifically bind to the target proteins, forming the antigen@antibody–DNA conjugates. The terminal free part of the DNA on the conjugates can trigger the CHA events to connect SERS nanotags to capture nanoprobes. Then, micro-magnet can gather the CHA products in a rectangular chamber, resulting in the aggregation of SERS nanotags, which can ultimately generate abundant "hot spots" for SERS signal enhancement. Using this strategy, CEA and CYFRA21-1 can be successfully determined with a limit of detection (LOD) as low as pg mL−1, much lower than recently reported methods. Meanwhile, a non-small cell lung cancer (NSCLC)-xenografted mouse model was established, and SERS was applied to analyze the expression level of CEA and CYFRA21-1 in tumorigenesis and development. The comparison between SERS results and those of the ELISA method demonstrated a high degree of consistency, suggesting that the proposed CHA-assisted LoC-SERS device has satisfying accuracy. Thus, introducing the CHA strategy via the design of antibody–DNA conjugates opens new gates to ultra-sensitive and specific SERS detection of protein biomarkers. [ABSTRACT FROM AUTHOR]

Circulating tumor DNA (ctDNA) is an ideal biomarker for cancer diagnosis based on liquid biopsy, so there is an urgent need for developing an efficient, rapid, and ultrasensitive detection method to meet clinical needs. In this paper, a novel surface-enhanced Raman scattering (SERS) microfluidic chip combined with a catalytic hairpin assembly (CHA) was proposed to detect two non-small cell lung cancer (NSCLC)-related ctDNA (TP53 and PIK3CA-Q546K) simultaneously. The chip consists of six channels for parallel detection. In the reaction region, the CHA reaction between HP1 of the SERS probe and HP2 of the capture substrate was triggered by ctDNAs to form HP1–HP2 duplexes. As the reaction proceeds, more and more SERS probes are captured on the substrate. The gathered reaction products continuously form a lot of hot spots, which greatly enhance the SERS signal. This reaction was completed within 5 minutes. Through this method, the detection limits of TP53 and PIK3CA-Q546K in human serum were as low as 2.26 aM and 2.34 aM, respectively. The microfluidic chip also exhibited high specificity, reproducibility and stability. The clinical feasibility of the SERS microfluidic chip was verified by analyzing the serum samples of healthy subjects and NSCLC patients. The reliability of the experimental results was verified by the qRT-PCR test. The constructed SERS-based analytical micro-platform has great potential in dynamic monitoring of cancer staging and could be used as a clinical tool for early cancer screening. [ABSTRACT FROM AUTHOR]

Research methods for DNA detection have been widely extended since the application of nanotechnology, but it remains a challenge to detect specific DNA sequences or low abundance genes in biological samples with accuracy and sensitivity. Herein, a novel biosensor is proposed for the analysis of target DNA in maize based on a high-density "hot spot" surface-enhanced Raman scattering (SERS) substrate and hybridization chain reaction (HCR) amplification strategy. Finite-difference time-domain (FDTD) simulation confirmed that the electromagnetic field enhancement at the gaps between the adjacent Au nanoflowers (AuNFs) was much richer than that around a single AuNF, indicating that the aggregated AuNFs had a good SERS signal amplification effect. Based on the high-density "hot spots" AuNF substrate, the HCR of biotin-hairpin DNA (bio-H1 and bio-H2) could be triggered by the existence of target DNA and a long double-stranded DNA (dsDNA) could be formed rapidly. Due to the biotin and streptavidin (SA) interaction, SERS probes prepared by modifying biotin-DNA-cyanine 5 (bio-DNA-Cy5) on the surface of Ag–Au core–shell nanorods (Ag–AuNRs) could be assembled along the dsDNA, causing significant signal enhancement. The developed biosensor displayed a significant sensitivity with a broad detection range covering from 0.01 to 1 × 104 fM, and the limit of detection (LOD) was as low as 6.31 aM. Moreover, SERS was applied to detect target DNA in maize extract to verify the feasibility of the detection strategy. This strategy could not only carry out the ultrasensitive detection of target DNA but also provide an informative supplement to the SERS biosensing platform. [ABSTRACT FROM AUTHOR]

A novel surface-enhanced Raman scattering (SERS)-lateral flow assay (LFA) biosensor in combination with catalytic hairpin assembly (CHA) signal amplification has been developed for the analysis of miR-196a-5p and miR-31-5p associated with lung cancer. In the presence of target miRNAs, two hairpin DNAs self-assembled into double-stranded DNA, making biotin molecules on the surface of Au–Ag nanoshuttles (Au–AgNSs) exposed. Therefore, the target enters the next cycle, while SERS complexes were trapped and concentrated on the different test lines (T1 and T2 lines), strongly amplifying the SERS signals. Through the finite difference time domain method, it was proved that the intense electromagnetic field enhancements provided "hot spots" for SERS in the nanogaps between aggregated Au–AgNSs, making Au–AgNSs exhibit excellent SERS performance. The prepared biosensor enabled rapid, sensitive, specific and simultaneous detection of miR-196a-5p and miR-31-5p. The whole detection time was short (40 min), and the detection limits of miR-196a-5p and miR-31-5p were as low as 1.171 nM and 2.251 nM in phosphate buffer, and were 1.681 nM and 2.603 nM in human serum, respectively. For the high accuracy diagnosis of lung cancer, SERS was successfully applied to quantitatively detect these two miRNAs in clinical serum from lung cancer patients at different stages and healthy subjects. The results of the SERS-LFA method were comparable to those of the real-time polymerase chain reaction. The designed multiple signal amplification SERS biosensor would be a very promising alternative tool for miRNA research in the field of biomedical diagnosis, which is of vital importance in the early detection and prevention of lung cancer. [ABSTRACT FROM AUTHOR]

The highly sensitive and reliable detection, imaging, and monitoring of changes of intracellular caspase-3 are critical for understanding the cell apoptosis and studying the progression of caspase-3-related cervical cancer. Herein, we present a novel surface-enhanced Raman scattering (SERS) probe for the detection of caspase-3 during cervical cancer cell apoptosis, composed of Au nanoboxes modified with Nile blue A as a Raman reporter and a caspase-3-specified peptide as a molecular cross-linker. In the presence of caspase-3, the substrate peptides can be cleaved and the changed surface charge of the Au nanoboxes results in the Au nanoboxes–NBA–peptide assembling to form aggregates and a great enhancement of SERS signal. The finite-difference time-domain simulation showed that hot spots mainly located in the nanogaps of the aggregated Au nanoboxes, which in theory proved the rationality of this signal amplification method. The SERS probes exhibited excellent reproducibility and selectivity toward caspase-3. A detection limit of 0.127 fM was obtained for caspase-3, with a dynamic range from 1 fM to 1 nM. MTT assay demonstrated that the probes had no obvious cytotoxicity within a certain concentration range. HeLa cells were treated with doxorubicin to induce long-term apoptosis. Upon cellular uptake of these probes, the spatiotemporal dynamics of caspase-3 in apoptotic cells could be real-time monitored using SERS. The activity of caspase-3 increased with the prolongation of apoptosis time. The SERS results were in accordance with that of western blotting assay. This kind of probe can offer great potential for the determination of enzymatic activities in the physiological processes of cells. [ABSTRACT FROM AUTHOR]

A CoNi-based metal–organic framework (CoNi-MOF) nanosheet array is synthesized by the treatment of a CoNi layered double hydroxide nanosheet array on Ni foam with 3,5-diaminobenzoic acid. The CoNi-MOF nanosheet array with amino and carboxyl groups can be used to capture the human chorionic gonadotropin (HCG) primary antibody (HCG Ab1). Nile Blue decorated ZnNi-MOF (NB@ZnNi-MOF) spheres immobilized with HCG secondary antibodies (HCG Ab2) are used for signal amplification. When HCG exists in an analytical sample, a sandwich structure is formed and an electrochemical signal is produced. The analytical signal generated during the detection is caused by the conversion of Co(II) and Co(III) in the CoNi-MOF nanosheet array. The Nile Blue of the NB@ZnNi-MOF sphere, as a kind of redox-active species, is responsible for the electrochemical signal amplification in the immunosensor. On the basis of the above advantages, the HCG immunosensor exhibits a lower limit of detection (1.85 × 10−3 mIU mL−1) and a wide linear range from 0.005 mIU mL−1 to 250 mIU mL−1. Additionally, this immunosensor is used to quantitatively detect HCG in human blood serum and shows good correlations with the standard enzyme-linked immunosorbent assay (ELISA), providing a high value on clinical diagnosis. [ABSTRACT FROM AUTHOR]

The electrode design is of considerable importance for developing enhanced electrochemical sensing platforms. Conductive metal–organic frameworks (MOFs), with high surface area, high conductivity, and large pore volume, possess an ideal architecture for the detection of molecules. In this study, we report the first electro-oxidation of glucose in an alkaline solution using conductive Ni-based metal–organic framework nanosheet arrays on carbon cloth (Ni-MOF NSAs/CC) as a non-noble metal catalyst. Compared with a number of ligands coordinated to nickel salt, 2,3,6,7,10,11-hexaaminotriphenylene hexahydrochloride was selected as the best ligand to synthesize Ni-MOF because it has the highest electrocatalytic activity for glucose oxidation. The 3D Ni-MOF NSAs/CC electrode, as multifunctional sensors, was used to detect glucose with a low detection limit of 0.57 μM (S/N = 3), a wide linear range of 0.001–7 mM, high sensitivity of 13428.89 μA mM−1 cm−2, and good selectivity. The results demonstrate that the as-prepared Ni-MOF NSAs/CC has considerable development and application potential for clinical medical testing. [ABSTRACT FROM AUTHOR]

The high incidence of premature rupture of membranes (PROM) is closely related to the lack of screening methods. Herein, a rapid and sensitive detection model for procalcitonin (PCT) and interleukin-6 (IL-6) was established utilizing the principle of antigen antibody binding and combined with surface enhanced Raman spectroscopy (SERS) and immunochromatographic assay (ICA), which could be used for the detection of specific biomarkers at a low concentration of peripheral blood and early detection of PROM patients. 5,5′-Dithiobis-2-nitrobenzoic acid labeled monoclonal anti-IL-6 on gold nanocages (GNCs) and 4-methylthiobenzoic acid labeled monoclonal anti-PCT on GNCs were employed as SERS tags. In the presence of IL-6 and PCT, the antigen-SERS tag complexes were trapped and concentrated on the two test lines. The unique characteristics of GNCs with hollow and multi-branch angle allowed high SERS performance in the system by increasing the biological binding sites and hot spots. Through finite difference time domain simulation, it could be concluded that the electromagnetic field between the gaps of GNC dimers was stronger than that of the single GNC, which proved the feasibility of ICA based on surface enhanced Raman scattering (SERS-ICA) in theory. The detection limits of IL-6 and PCT in phosphate buffer were 7.897 pg mL−1 and 7.725 pg mL−1, meanwhile the detection limits of peripheral blood were 8.414 pg mL−1 and 8.017 pg mL−1, respectively. In addition, the detection of real-world samples showed that SERS-ICA was available to evaluate the concentrations of IL-6 and PCT. The experimental data of SERS-ICA were in accordance with that of enzyme-linked immunosorbent assay. These results indicated that SERS-ICA had great potential in the early screening of PROM. [ABSTRACT FROM AUTHOR]

Variations in the intracellular expression level of cancer-related microRNAs (miRNAs) are connected with worsening tumor progression. A simple, accurate, and sensitive analytical method for the imaging and detection of intracellular miRNA is still a great challenge due to the low abundance of miRNAs and the complexity of intracellular environments. In this work, target miRNA (miRNA)-mediated catalytic hairpin assembly (CHA)-induced gold nanocage (GNC)-hairpin DNA1 (hpDNA1)-hpDNA2-GNC nanostructures were designed for surface-enhanced Raman scattering (SERS) detection and imaging of the specific miR-125a-5p in the normal lung epithelial cell line (BEAS-2B cells) and lung cancer cell line (A549 cells). The finite difference time domain (FDTD) simulations showed that the polymer of GNCs possessed a much stronger electromagnetic field in nanogaps than that of single GNC, theoretically confirming the rational design of the CHA assembly strategy. Using this method, miR-125a-5p can be detected in a wide linear range with a detection limit of 43.96 aM and high selectivity over other miRNAs in vitro. Moreover, SERS imaging successfully detected and distinguished the expression levels of intracellular miR-125a-5p in BEAS-2B cells and A549 cells. The results obtained by the SERS assay were consistent with those obtained by the real-time quantitative polymerase chain reaction (qRT-PCR). This method can offer a powerful strategy for the imaging and quantitative detection of various types of biomolecules in vitro as well as in living cells. [ABSTRACT FROM AUTHOR]

In this communication, for the first time, an easy preparation method of nickel–iron (Ni–Fe) hybrid nanocubes for glucose oxidation, which is highly efficient in alkaline media, is described. As an impressive redox probe for glucose, the Ni–Fe hybrid nanocubes exhibit many remarkable sensing performances, for example, low-response time (7 s), broad detection range (from 10 μM to 20.5 mM), and low detection limit (0.64 μM, S/N = 3). The selectivity, reliability and stability of the Ni–Fe hybrid nanocubes for glucose oxidation are also investigated. The glucose sensor based on Ni–Fe hybrid nanocubes shows a superior sensing performance to that of Ni-based or Fe-based electrochemical sensors. Furthermore, the Ni–Fe hybrid nanocubes were used to detect glucose in real samples of human blood serum. All the findings demonstrate that the glucose sensor based on Ni–Fe hybrid nanocubes is successful for glucose detection and shows promise for future applications in medical diagnostics, the food industry and biological processes. [ABSTRACT FROM AUTHOR]

Bone marrow mesenchymal stem cells (BMSCs) are multipotent stem cells, which play an important role in the repair of bone injury, angiogenesis, immune diseases, cancer invasion and metastasis. Therefore, increasing attention has been focused on the study of BMSCs. However, the identification and discrimination of the undifferentiated and differentiated BMSCs, which are closely related and morphologically similar, are still a challenge using traditional methods. In this study, we report a novel surface-enhanced Raman scattering (SERS) substrate based on hollow gold nanoflower (HAuNF)-decorated silicon wafers for distinguishing the differentiation of BMSCs. The flower-like, hollow Au nanoparticles were successfully synthesized by a seed-mediated growth approach. We demonstrated that fabricated HAuNF substrates had very good reproducibility, homogeneous SERS activity and a high SERS effect. Using HAuNF substrates as a high-performance in vitro sensing platform allowed us to monitor the changes in the cellular biochemical composition during the differentiation of BMSCs. SERS spectra were analyzed using principal component analysis (PCA), which successfully segregated the subtypes of BMSCs. Furthermore, the results of biological assay suggested that the adipogenic inductor and the osteogenic inductor could induce the differentiation of BMSCs into adipocytes and osteocytes, respectively. The SERS technique based on HAuNF substrates provides a sensitive, efficient and non-invasive detection method for studying the differentiation of stem cells. [ABSTRACT FROM AUTHOR]

A new fluorescence turn-on probe for Hg2+imaging in living cells was judiciously designed based on the interactions of Hg2+to both thiol and alkyne moieties in a rhodamine scaffold, and the likely novel sensing mechanism has been proposed. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged as a novel pathogen in 2019. The virus is responsible for a severe acute respiratory syndrome outbreak, affecting the respiratory system of infected individuals. COVID-19 is a super amplifier of basic diseases, and the disease with basic diseases is often more serious. Controlling the spread of the COVID-19 pandemic relies heavily on the timely and accurate detection of the virus. To resolve the problem, a polyaniline functionalized NiFeP nanosheet array-based electrochemical immunosensor using Au/Cu 2 O nanocubes as a signal amplifier is fabricated for the detection of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP). Polyaniline (PANI) functionalized NiFeP nanosheet arrays are synthesized as an ideal sensing platform for the first time. PANI is coated on the surface of NiFeP by electropolymerization to enhance biocompatibility, beneficial for the efficient loading of the capture antibody (Ab 1 ). Significantly, Au/Cu 2 O nanocubes possess excellent peroxidase-like activity and exhibit outstanding catalytic activity for the reduction of H 2 O 2 . Therefore, Au/Cu 2 O nanocubes combine with a labeled antibody (Ab 2 ) through the Au-N bond to form labeled probes, which can effectively amplify current signals. Under optimal conditions, the immunosensor for the detection of SARS-CoV-2 NP shows a wide linear range of 10 fg mL -1 -20 ng mL -1 and a low detection limit of 1.12 fg mL -1 (S/N = 3). It also exhibits desirable selectivity, repeatability, and stability. Meanwhile, the excellent analytical performance in human serum samples confirms the practicality of the PANI functionalized NiFeP nanosheet array-based immunosensor. The electrochemical immunosensor based on the Au/Cu 2 O nanocubes as a signal amplifier demonstrates great potential for application in the personalized point-of-care (POC) clinical diagnosis.

Herein, we proposed a novel biosensor based on a high-density "hot spot" Au@SiO 2 array substrate and rolling circle amplification (RCA) strategy for the ultrasensitive detection of CpG methyltransferase (M.SssI) activity. In the presence of M.SssI, the RCA process can be triggered, causing the augmentation of the single-stranded DNA (ssDNA) at the tail of the double-stranded DNA (dsDNA), and the ssDNA can be hybridized with numerous DNA probes labeled with Raman reporters in the next steps. Afterwards, the resultant ssDNA can be modified to the Au@SiO 2 array substrate with the SERS enhancement factor of 7.49 × 10 6 . The substrate was synthesized by using a monolayer SiO 2 array to pick up the Au nanoparticle (AuNP) array and finite-difference time-domain (FDTD) simulation showed its excellent SERS effect. Particularly, the developed biosensor displayed a significant sensitivity with a broad detection range covering from 0.005 to 50 U mL -1 , and the limits of detection (LODs) in PBS buffer and human serum were 2.37 × 10 -4 U mL -1 and 2.51 × 10 -4 U mL -1 , respectively. Finally, in order to verify the feasibility of its clinical application, the serum samples of healthy subjects and breast cancer, prostate cancer, gastric cancer and cervical cancer patients were analyzed, and the reliability of the results was also confirmed by western blot (WB) experiments. Taking advantage of these merits, the proposed biosensor can be a very promising alternative tool for the detection of M.SssI activity, which is of vital importance in the early detection and prevention of tumors.

A CoNi-based metal-organic framework (CoNi-MOF) nanosheet array is synthesized by the treatment of a CoNi layered double hydroxide nanosheet array on Ni foam with 3,5-diaminobenzoic acid. The CoNi-MOF nanosheet array with amino and carboxyl groups can be used to capture the human chorionic gonadotropin (HCG) primary antibody (HCG Ab1). Nile Blue decorated ZnNi-MOF (NB@ZnNi-MOF) spheres immobilized with HCG secondary antibodies (HCG Ab2) are used for signal amplification. When HCG exists in an analytical sample, a sandwich structure is formed and an electrochemical signal is produced. The analytical signal generated during the detection is caused by the conversion of Co(ii) and Co(iii) in the CoNi-MOF nanosheet array. The Nile Blue of the NB@ZnNi-MOF sphere, as a kind of redox-active species, is responsible for the electrochemical signal amplification in the immunosensor. On the basis of the above advantages, the HCG immunosensor exhibits a lower limit of detection (1.85 × 10-3 mIU mL-1) and a wide linear range from 0.005 mIU mL-1 to 250 mIU mL-1. Additionally, this immunosensor is used to quantitatively detect HCG in human blood serum and shows good correlations with the standard enzyme-linked immunosorbent assay (ELISA), providing a high value on clinical diagnosis.

We have constructed a novel NIR fluorescent turn-on hydrogen sulfide probe suitable for fluorescent imaging in living cells based on thiolysis of dinitrophenyl ether.

We have constructed a novel NIR fluorescent turn-on Cu(+) probe suitable for imaging endogenous Cu(+) ions in living cells based on a tricarbocyanine scaffold and a high affinity Cu(+) receptor.

A novel reversible fluorescence turn-on chemosensor 1 for Hg(2+) was constructed based on a new receptor composed of an S atom and an alkene moiety. The sensor showed a large fluorescence enhancement response (1000-fold enhancement), high selectivity, and high sensitivity with a detection limit of 27.5 nM. Significantly, the reversible sensor functioned well in the near pure aqueous medium and could be employed for Hg(2+) imaging in living cells.