Publications by authors named "Ruqin Yu"

153 Publications

One-step enzyme-free detection of the miRNA let-7a via twin-stage signal amplification.

Talanta 2021 Aug 19;230:122158. Epub 2021 Feb 19.

State Key Laboratory for Chemo/Biosensing and Chemometrics, Hunan University, Changsha, 410082, PR China. Electronic address:

MicroRNAs (miRNAs) play a significant role in diverse biological processes. The abnormal expression of miRNAs is related to the development of cancers and various diseases. It is of great importance to sensitively and accurately detect miRNAs for early disease diagnosis and treatment. Here, a new fluorescence strategy was initially proposed for the enzyme-free sensing of let-7a by combining the strand displacement reaction (SDR) with the hybridization chain reaction (HCR). The sensor was successfully applied to the detection of the let-7a gene with a wide linear range from 25 pM to 250 nM and a limit of detection (LOD) of 9.01 pM. The fluorescence intensity has a good linear relationship with the logarithm of the target concentration. In addition, the biosensor allowed for the highly sensitive detection of the target genes even in complex human serum samples. With simple operation yet improved detection capability for let-7a, the developed fluorescent biosensor thus shows great potential for early clinical diagnosis as well as biological research.
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http://dx.doi.org/10.1016/j.talanta.2021.122158DOI Listing
August 2021

Ratiometric sensors with selective fluorescence enhancement effects based on photonic crystals for the determination of acetylcholinesterase and its inhibitor.

J Mater Chem B 2020 12;8(48):11001-11009

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.

Ratiometric fluorescent sensors are powerful tools for quantitative analyses. However, gold nano-clusters (AuNCs) as typical fluorophores in ratiometric sensors have some disadvantages, such as low luminous efficiency. In this study, a highly sensitive ratiometric fluorescence sensor was fabricated by the combination of AuNCs and fluorescein (FL), and the photonic crystals (PhCs) were used to selectively enhance the fluorescence intensity of AuNCs. This fluorescence sensor was used for the sensitive detection of acetylcholinesterase (AChE) and its inhibitor paraoxon. AChE can catalyze the hydrolysis of acetylthiocholine (ATCh) to form thiocholine (TCh), which can induce the fluorescence quenching of AuNCs while having no obvious influence on the fluorescence intensity of FL. AChE can be determined in the range from 0.1 to 25 mU mL-1 with a limit of detection (LOD) of 0.027 mU mL-1, and paraoxon can be determined in the range of 0.06 to 60 ng mL-1 with a LOD 0.025 ng mL-1. This method, as a new way to selectively improve the fluorescence signal of one of the fluorophores in the ratiometric sensor, would be a promising strategy for the sensitive determination of AChE and its inhibitor.
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http://dx.doi.org/10.1039/d0tb02197kDOI Listing
December 2020

Photonic crystal enhanced gold-silver nanoclusters fluorescent sensor for Hg ion.

Anal Chim Acta 2020 Jun 8;1114:50-57. Epub 2020 Apr 8.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, PR China.

Luminescent nanoclusters (NCs) have attracted much attention because of their good photostability and low toxicity, however, the low quantum yield is still a deficiency, and many increasing efforts are being devoted to enhance the luminescence intensity of NCs. In this paper, a method of enhancing the fluorescent signal of gold-silver nanoclusters (AuAgNCs) by photonic crystals (PhCs) was proposed. The fluorescent intensity of AuAgNCs on PhCs can be enhanced 8.0-fold in comparison to the control sample without PhCs. Furthermore, a novel fluorescence sensor of AuAgNCs based on PhCs is used for the sensitive and selective detection of Hg ion in the aqueous solution, the detection limit is 0.35 nM due to the PhCs enhancement effect for the fluorescence. This proposed method may not only develop a highly sensitive method for determination of Hg ion, but also expand the application of AuAgNCs in ultra-trace analysis.
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http://dx.doi.org/10.1016/j.aca.2020.04.011DOI Listing
June 2020

Cyclodextrin supramolecular inclusion-enhanced pyrene excimer switching for highly selective detection of RNase H.

Anal Chim Acta 2019 Dec 27;1088:137-143. Epub 2019 Aug 27.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.

Here, we report a novel fluorescence method for the highly selective and sensitive detection of RNase H by combining the use of a dual-pyrene-labeled DNA/RNA duplex with supramolecular inclusion-enhanced fluorescence. Initially, the probe is in the "off" state due to the rigidness of the double-stranded duplex, which separates the two pyrene units. In the presence of RNase H, the RNA strand of the DNA/RNA duplex will be hydrolyzed, and the DNA strand transforms into a hairpin structure, bringing close the two pyrene units which in turn enter the hydrophobic cavity of a γ-cyclodextrin. As a result, the pyrene excimer emission is greatly enhanced, thereby realizing the detection of RNase H activity. Under optimal conditions, RNase H detection can be achieved in the range from 0.08 to 4 U/mL, with a detection limit of 0.02 U/mL.
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http://dx.doi.org/10.1016/j.aca.2019.08.059DOI Listing
December 2019

Ultra-sensitive label-free electrochemical detection of the acute leukaemia gene Pax-5a based on enzyme-assisted cycle amplification.

Biosens Bioelectron 2019 Oct 14;143:111593. Epub 2019 Aug 14.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering Hunan University, Changsha, 410082, PR China. Electronic address:

Accurate and sensitive detection of the Pax-5a gene is of great importance in the early diagnosis and prognosis of acute leukaemia. Herein, a label-free electrochemical sensing system was proposed for the detection of the acute leukaemia Pax-5a gene based on enzyme-assisted signal amplification to generate abundant G-quadruplex/hemin DNAzyme. The presence of Pax-5a can open the hairpin probe (HP), which acts as a template. Under the action of the restriction enzymes Nt.BbvCI and Klenow fragment polymerase, the target gene Pax-5a is cycled to open the HP; On the other hand, a large number of G-quadruplex sequences are produced. The resulting G-quadruplex sequence is capable of forming the G-quadruplex/hemin complex on the surface of the electrode in the presence of hemin. The ultrasensitive label-free electrochemical detection of Pax-5a can be realized via the G-quadruplex/hemin complex-catalysed reduction of HO, and the detection limit was estimated to be as low as 4.6 fM. In addition, the biosensor has good specificity and stability, and also has excellent detection capabilities in a complex substrate environment. Therefore, the sensor shows great potential in bioanalysis and clinical diagnosis.
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http://dx.doi.org/10.1016/j.bios.2019.111593DOI Listing
October 2019

Fluorometric determination of the p53 cancer gene using strand displacement amplification on gold nanoparticles.

Mikrochim Acta 2019 07 6;186(8):517. Epub 2019 Jul 6.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering Hunan University, Changsha, 410082, People's Republic of China.

A fluorometric assay is described for the tumor suppressor gene p53. The method is based on strand displacement amplification on gold nanoparticles (GNPs). A FAM-labeled hairpin probe (HPP) is used that can hybridize to the GNP-confined linker strand, and the green fluorescence of the FAM label is quenched by the GNPs. In the presence of the p53 gene, it will hybridize with the HPP. This leads to fluorescence recovery. The primer then hybridizes with the opened HPP and induces the polymerization/displacement reactions. As a result, the hybridized p53 gene is released and, in turn, hybridizes with another HPP on the surface of the GNPs. This triggers the next round of hybridization/enzymatic polymerization/displacement reactions. This results in efficient strand displacement amplification and generates a substantially amplified signal. The method is referred to as GNP-HPP because it involves the use of GNPs and a HPP. The method allows the target DNA (p53) to be quantified down to 1.6 pM concentrations with a linear response in the 5 pM to 1 nM concentration range. In addition, mutant p53 genes can be easily distinguished from the wild-type gene. The method is highly sensitive, selective, and has a low background signal. Graphical abstract Schematic presentation of a chain hybridization signal amplification system (GNP-HPP) based on the use of gold nanoparticles (GNP) as a quenching source for the tumor suppressor gene p53 detection. The hairpin probe (HPP) having a 5'-end modified fluorophore was used as a signalling probe.
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http://dx.doi.org/10.1007/s00604-019-3609-0DOI Listing
July 2019

Palindromic molecular beacon-based intramolecular strand-displacement amplification strategy for ultrasensitive detection of K-ras gene.

Anal Chim Acta 2019 Aug 19;1065:98-106. Epub 2019 Mar 19.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering Hunan University, Changsha, 410082, PR China.

The sensitive detection of tumor proto-oncogenes is indispensable because the early diagnosis and accurate treatment of genetic diseases is the key guarantee of patients' health. In this study, we proposed a novel palindromic molecular beacon (PMB) that it bases on the signal amplification strategy for ultrasensitive detection of Kras gene codon 12. PMB is designed to have two palindromic fragments at its two ends, one of which is locked via folding into a hairpin structure and the other promotes the formation of PMB duplex via intermolecular self-hybridization. Target DNA can hybridize to the loop portion of PMB and release the palindromic fragment at the 3' end. Within the PMB duplex, the two palindromic fragments released hybridize with each other and serve as polymerization primer responsible for the strand-displacement amplification (SDA). Namely, hybridized target DNA can be displaced and initiates the next round of reactions, making the polymerization/displacement/hybridization process go forward circularly. As a result, a large number of polymerization products are produced, dramatically enhancing optical signal. Because primer hybridization and polymerization-based displacement occur within PMB duplex, the reaction process is called intramolecular strand-displacement amplification (ISDA). Via utilizing the newly-proposed PMB-based ISDA strategy, the target K-ras gene could be detected down to 10 pM with a wide response range of 1 × 10-1.5 × 10 M, and point mutations are easily distinguished, realizing the ultrasensitive, highly selective detection of K-ras gene. This impressive sensing paradigm demonstrates a new concept of signal amplification for the detection of disease-related genes only via using a simple way to efficiently amplify optical signal.
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http://dx.doi.org/10.1016/j.aca.2019.02.059DOI Listing
August 2019

Internal standard-based SERS aptasensor for ultrasensitive quantitative detection of Ag ion.

Talanta 2018 Aug 9;185:30-36. Epub 2018 Mar 9.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.

A ratiometric surface-enhanced Raman scattering (SERS) aptasensor based on internal standard (IS) methods was proposed for the ultrasensitive and reproducible quantitative detection of silver ion (Ag) with [email protected] core-shell nanoparticle ([email protected] NP) substrate. In principle, the thiolated 5'-Rox C-containing labeled aptamer probe (Rox-aptamer) is firstly immobilized on the SERS substrate surface and then hybridizes with the complementary DNA (cDNA) to form a rigid double-stranded DNA (dsDNA), in which the Rox Raman labels is used to produce the Raman signal. Furthermore, the pyridine is employed as an IS element to provide the ratiometric determination of target. In the presence of Ag, the Rox-aptamer is turned into the cytosine (C)-Ag-C mediated hairpin structure, which remarkably reduces the distance between the Rox labels and the [email protected] NP surface responsible for a measurable 'turn-on' signal change of Rox. This IS-based ratiometric SERS aptasensor exhibits a limit of detection of 50 pM for Ag with a linear detection range from 0.1 to 100 nM and the shortcoming of irreproducibility of SERS signal could be overcome. The proposed method provides a simple, robust, and rapid approach for the sensitive and reproducible quantitative detection of Ag, and it could also be used for the detection of other metal ions which exhibits specific interactions with natural or synthetic bases.
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http://dx.doi.org/10.1016/j.talanta.2018.03.014DOI Listing
August 2018

A Novel Biosensor Based on Terminal Protection and Fluorescent Copper Nanoparticles for Detecting Potassium Ion.

Anal Sci 2017 ;33(12):1369-1374

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University.

A novel biosensor for sensitively detecting potassium ion (K) has been developed based on fluorescent copper nanoparticles (Cu NPs). In our design, we employ a label-free single-strand DNA (ssDNA) that contains two parts. One is 3'-terminus structure-switching aptamers (SSAs) that can fold into G-quadruplex after binding with its target K. The other is 5'-terminus poly thymine (polyT) which works as a template to construct fluorescent Cu NPs. After incubating with K, the part SSAs go through target-induced conformational changes. Benifiting from the exceptional digestion ability of exonuclease I (Exo I), the G-quadruplexes display effective resistance to nuclease digestion, so that 5'-terminus polyT remains and the in situ formation of Cu NPs provides a turn-on fluorescent signal that is used to evaluate the concentration of K. The recovery of the fluorescence intensity is linearly correlated with the K concentration in the range of 0.05 to 1 mM with a detection limit of 0.05 mM. Compared with some methods, this assay is cost-effective and facile with high specificity. Meanwhile, this excellent strategy shows a great potentiality in other sensing approaches that can study the interaction between similar SSAs and different specific targets.
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http://dx.doi.org/10.2116/analsci.33.1369DOI Listing
August 2018

A label-free and highly sensitive strategy for uracil-DNA glycosylase activity detection based on stem-loop primer-mediated exponential amplification (SPEA).

Anal Chim Acta 2017 Oct 13;991:127-132. Epub 2017 Sep 13.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China. Electronic address:

Uracil-DNA glycosylase (UDG) plays essential roles in base excision repair (BER) pathway by eliminating uracil from DNA to sustain the genome integrity. Sensitive detection of UDG activity is of great significance in the study of many fundamental biochemical processes and clinical applications. We develop a label-free method for UDG activity detection using stem-loop primer-mediated exponential amplification (SPEA). In the presence of active UDG, the uracil base in helper hairpin probe (HP) can be excised to generate an abasic site (AP site), which can be cleaved by endonuclease IV (Endo IV) with a blocked primer released. This primer then triggers the strand displacement reaction to produce a dumb-bell structure DNA, which can initiate a loop-mediated isothermal amplification (LAMP) reaction. This reaction generates a large number of long double-strand DNA replicates, which can be stained by SYBR Green (SG) I to deliver enhanced fluorescence for quantitative detection of UDG activity. A linear range from 0.001 U/mL to 1 U/mL and a detection limit down to 0.00068 U/mL are achieved. This strategy has also been demonstrated for UDG assay in complex cell lysates, implying its great potential for UDG based clinical diagnostics and therapeutics.
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http://dx.doi.org/10.1016/j.aca.2017.08.042DOI Listing
October 2017

Novel ratiometric surface-enhanced raman spectroscopy aptasensor for sensitive and reproducible sensing of Hg.

Biosens Bioelectron 2018 Jan 19;99:646-652. Epub 2017 Aug 19.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China.

It is important to precisely monitor mercury (II) ions (Hg) for environment protection and human health monitoring. Although many strategies have been developed in the past decades, there still remains a challenge for developing an ultrasensitive, simple and reliable approach to detect Hg. Herein, we report a ratiometric surface-enhanced Raman scattering (SERS) aptasensor by employing aptamer-modified [email protected] core-shell nanoparticles ([email protected] NPs) as highly functional sensing probes, allowing for ultrasensitive detection of Hg. In principle, the thiolated 5'-Cy3 labeled aptamer probe (Cy3-aptamer) is firstly immobilized on the SERS substrate surface and then hybridizes with the 5'-Rox labeled complementary DNA (cDNA) to form a rigid double-stranded DNA (dsDNA), in which the Cy3 and Rox Raman labels are used to produce the ratiometric Raman signals. In the presence of Hg, the aptamer DNA turns into the thymine (T)-Hg-T mediated hairpin structure, leading to the dissociation of dsDNA. As a result, the Rox labels are away from the [email protected] NP SERS substrate while Cy3 labels are close to it. Therefore, the intensity of SERS signal from Cy3 labels increases while that from Rox labels decreases. The ratio between the Raman intensities of Cy3 labels and Rox labels is linear with Hg concentrations in the range from 0.001 to 1.0nM, and the limit of detection is estimated to be 0.4pM. The proposed strategy provides a new rapid, simple and reliable approach for sensitive detection of Hg and may create a universal methodology for developing analogous aptasensors for a wide range of other analytes determination.
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http://dx.doi.org/10.1016/j.bios.2017.08.041DOI Listing
January 2018

A dual enzyme-inorganic hybrid nanoflower incorporated microfluidic paper-based analytic device (μPAD) biosensor for sensitive visualized detection of glucose.

Nanoscale 2017 May;9(17):5658-5663

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.

A novel microfluidic paper-based analytic device (μPAD) biosensor is developed for sensitive and visualized detection of glucose. This biosensor is easily fabricated using the wax printing technique, with a hybrid nanocomplex composed of dual enzymes glucose oxidase (GOx) and horseradish peroxidase (HRP) and Cu(PO) inorganic nanocrystals incorporated in the detection zones. The hybrid nanocomplex is found to exhibit a flower-like structure, which allows co-immobilization of these two enzymes in a biocompatible environment. These nanoflowers not only preserve the activity and enhance the stability of the enzymes, but also facilitate the transport of the substrates between the two enzymes. The biosensor is demonstrated to enable rapid and sensitive quantification of glucose in the concentration range of 0.1-10 mM with a limit of detection (LOD) of 25 μM. It is also shown to be applicable to colorimetric quantitative detection of glucose in human serum and whole blood samples, implying its potential for clinical applications.
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http://dx.doi.org/10.1039/c7nr00958eDOI Listing
May 2017

Novel Aptasensor Platform Based on Ratiometric Surface-Enhanced Raman Spectroscopy.

Anal Chem 2017 03 22;89(5):2852-2858. Epub 2017 Feb 22.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University , Changsha, Hunan, China.

A novel aptasensor platform has been developed for quantitative detection of adenosine triphosphate (ATP) based on a ratiometric surface-enhanced Raman scattering (SERS) strategy. The thiolated 3'-Rox-labeled complementary DNA (cDNA) is first immobilized on the gold nanoparticle (AuNP) surface and then hybridizes with the 3'-Cy5-labeled ATP-binding aptamer probe (Cy5-aptamer) to form a rigid double-stranded DNA (dsDNA), in which the Cy5 and Rox Raman labels are used to produce the ratiometric Raman signals. In the presence of ATP, the Cy5-aptamer is triggered the switching of aptamer to form the aptamer-ATP complex, leading to the dissociation of dsDNA, and the cDNA is then formed a hairpin structure. As a result, the Rox labels are close to the AuNP surface while the Cy5 labels are away from. Therefore, the intensity of SERS signal from Rox labels increases while that from Cy5 labels decreases. The results show that the ratio between the Raman intensities of Rox labels and Cy5 labels is well linear with the ATP concentrations in the range from 0.1 to 100 nM, and the limit of detection reaches 20 pM, which is much lower than that of other methods for ATP detection and is also lower than that of SERS aptasensor for ATP detection. The proposed strategy provides a new reliable platform for the construction of SERS biosensing methods and has great potential to be a general method for other aptamer systems.
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http://dx.doi.org/10.1021/acs.analchem.6b04010DOI Listing
March 2017

Pattern recognition of enrichment levels of SELEX-based candidate aptamers for human C-reactive protein.

Biomed Tech (Berl) 2017 May;62(3):333-338

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Selecting aptamers for human C-reactive protein (CRP) would be of critical importance in predicting the risk for cardiovascular disease. The enrichment level of DNA aptamers is an important parameter for selecting candidate aptamers for further affinity and specificity determination. This paper is the first report on pattern recognition used for CRP aptamer enrichment levels in the systematic evolution of ligands by exponential enrichment (SELEX) process, by applying structure-activity relationship models. After generating 10 rounds of graphene oxide (GO)-SELEX and 1670 molecular descriptors, eight molecular descriptors were selected and five latent variables were then obtained with principal component analysis (PCA), to develop a support vector classification (SVC) model. The SVC model (C=8.1728 and γ=0.2333) optimized by the particle swarm optimization (PSO) algorithm possesses an accuracy of 88.15% for the training set. Prediction results of enrichment levels for the sequences with the frequencies of 6 and 5 are reasonable and acceptable, with accuracies of 70.59% and 76.37%, respectively.
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http://dx.doi.org/10.1515/bmt-2015-0230DOI Listing
May 2017

Sensitive inkjet printing paper-based colormetric strips for acetylcholinesterase inhibitors with indoxyl acetate substrate.

Talanta 2017 Jan 4;162:174-179. Epub 2016 Oct 4.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China.

A new paper-based biosensing approach has been developed for sensitive and rapid detection of acetylcholinesterase (AChE) inhibitors. The biosensing zone of the paper strip is constructed with an inkjet printing method, and the biomolecule AChE is immobilized into two layers of biocompatible sol-gel-derived silica ink with a "sandwich" form. Indoxyl acetate (IDA) is used as a chromogenic substrate, which is colorless and can be catalytically hydrolyzed into blue-colored indigo dipolymer. When the enzymatic activity of AChE is inhibited after incubation with organophosphate pesticides (OPs), there is a decreased hydrolysis of IDA accompanying with a drop in color intensity. Paraoxon and trichlorfon are used as the representative OPs in the assay. Due to the low solubility and high molar absorption coefficient of the IDA dipolymer product, the paper-based strip can form a neat blue sensing zone and shows obviously improved sensitivity with a limit of detection (LOD) of 0.01ngmL paraoxon and 0.04ngmL trichlorfon (S/N=3) and the LODs for visual detection are 0.03ngmL for paraoxon and 0.1ngmL for trichlorfon comparing with the previously reported colorimetric methods. The concentrations of paraoxon in apple juice samples are also detected, and the results are in accord well with these results from high-performance liquid chromatography, showing great potential for on-site detection of OPs in practical application. The developed assay can be used to qualitatively and semiquantitatively estimate with naked eyes and quantitatively assess OPs through image analysis.
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http://dx.doi.org/10.1016/j.talanta.2016.10.011DOI Listing
January 2017

A ligation-based loop-mediated isothermal amplification (ligation-LAMP) strategy for highly selective microRNA detection.

Chem Commun (Camb) 2016 Oct;52(86):12721-12724

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.

A novel ligation-based loop-mediated isothermal amplification (ligation-LAMP) method has been developed for miRNA detection, which enables highly selective and sensitive quantitative detection of miR-21 in a dynamic range from 1 fM to 1 nM with the ability to discriminate single-base mismatches.
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http://dx.doi.org/10.1039/c6cc06160eDOI Listing
October 2016

Label-Free Photonic Crystal-Based β-Lactamase Biosensor for β-Lactam Antibiotic and β-Lactamase Inhibitor.

Anal Chem 2016 09 30;88(18):9207-12. Epub 2016 Aug 30.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University , Changsha 410082, People's Republic of China.

A simple, label-free, and visual photonic crystal-based β-lactamase biosensor was developed for β-lactam antibiotic and β-lactamase inhibitor in which the penicillinase (a β-lactamase) was immobilized on the pH-sensitive colloidal crystal hydrogel (CCH) film to form penicillinase colloidal crystal hydrogel (PCCH) biosensing film. The hydrolysis of penicillin G (a β-lactam antibiotic) can be catalyzed by penicillinase to produce penicilloic acid, leading to a pH decrease in the microenvironment of PCCH film, which causes the shrink of pH-sensitive CCH film and triggers a blue-shift of the diffraction wavelength. Upon the addition of β-lactamase inhibitor, the hydrolysis reaction is suppressed and no clear blue-shift is observed. The concentrations of β-lactam antibiotic and β-lactamase inhibitor can be sensitively evaluated by measuring the diffraction shifts. The minimum detectable concentrations for penicillin G and clavulanate potassium (a β-lactamase inhibitor) can reach 1 and 0.1 μM, respectively. Furthermore, the proposed method is highly reversible and selective, and it allows determination of penicillin G in fish pond water samples.
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http://dx.doi.org/10.1021/acs.analchem.6b02457DOI Listing
September 2016

A novel logic gate based on liquid-crystals responding to the DNA conformational transition.

Analyst 2016 05;141(10):2870-3

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.

Described herein is a novel liquid crystal (LC)-based DNA logic gate constructed via employing the reorientation of LCs triggered by metal-ion-mediated DNA probe conformational changes.
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http://dx.doi.org/10.1039/c6an00504gDOI Listing
May 2016

Label-free liquid crystal biosensor for L-histidine: A DNAzyme-based platform for small molecule assay.

Biosens Bioelectron 2016 May 31;79:650-5. Epub 2015 Dec 31.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China.

We have developed a novel DNAzyme-based liquid crystal (LC) biosensor with high sensitivity for L-histidine, which is based on L-histidine-mediated formation of DNA duplexes by cleaving DNAzyme using L-histidine, resulting in a remarkable optical signal. Firstly, an optimal amount of capture probe is bound to the glass slide, which changes the surface topology as little as possible and shows a zero-background for the sensing system. When the DNAzyme molecule is cleaved by the target, L-histidine, a partial substrate strand is produced, which in turn can hybridize with the capture probe, forming a DNA duplex. The DNA duplexes induce LC molecules to undergo a homeotropic-to-tiled transition, obtaining a remarkable optical signal. The results show that the DNAzyme-based LC biosensor is highly sensitive to L-histidine with a detection limit of 50 nM. Compared with previously reported multi-step amplified methods, this newly designed assay system for L-histidine has no amplified procedures with comparable sensitivity. This method is an unprecedented example of DNAzyme-based LC biosensor for small molecules, which has potential to offer a DNAzyme-based LC model used in various targets.
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http://dx.doi.org/10.1016/j.bios.2015.12.107DOI Listing
May 2016

Synthesis of WS2xSe2-2x Alloy Nanosheets with Composition-Tunable Electronic Properties.

Nano Lett 2016 Jan 3;16(1):264-9. Epub 2015 Dec 3.

School of Chemistry, Physics and Mechanical Engineering Faculty, Queensland University of Technology , Garden Point Campus, QLD 4001 Brisbane, Australia.

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have recently emerged as a new class of atomically thin semiconductors for diverse electronic, optoelectronic, and valleytronic applications. To explore the full potential of these 2D semiconductors requires a precise control of their band gap and electronic properties, which represents a significant challenge in 2D material systems. Here we demonstrate a systematic control of the electronic properties of 2D-TMDs by creating mixed alloys of the intrinsically p-type WSe2 and intrinsically n-type WS2 with variable alloy compositions. We show that a series of WS2xSe2-2x alloy nanosheets can be synthesized with fully tunable chemical compositions and optical properties. Electrical transport studies using back-gated field effect transistors demonstrate that charge carrier types and threshold voltages of the alloy nanosheet transistors can be systematically tuned by adjusting the alloy composition. A highly p-type behavior is observed in selenium-rich alloy, which gradually shifts to lightly p-type, and then switches to lightly n-type characteristics with the increasing sulfur atomic ratio, and eventually evolves into highly n-doped semiconductors in sulfur-rich alloys. The synthesis of WS2xSe2-2x nanosheets with tunable optical and electronic properties represents a critical step toward rational design of 2D electronics with tailored spectral responses and device characteristics.
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http://dx.doi.org/10.1021/acs.nanolett.5b03662DOI Listing
January 2016

A novel fluorescence assay for inorganic pyrophosphatase based on modulated aggregation of graphene quantum dots.

Analyst 2016 Jan 19;141(1):251-5. Epub 2015 Nov 19.

College of Chemistry and Chemical Engineering, Hunan University, State Key Laboratory for Chemo/Biosensing and Chemometrics, Changsha, Hunan, China.

A simple and highly sensitive fluorometric method has been developed for inorganic pyrophosphatase (PPase) activity detection based on the disaggregation and aggregation of graphene quantum dots (GQDs). Copper ions can trigger the severe aggregation of GQDs with rich carboxyl groups, which results in effective fluorescence quenching. While, with the addition of pyrophosphate (PPi), the quenched fluorescence is effectively recovered owing to the strong interaction between PPi and Cu(2+). Furthermore, under the catalytic hydrolysis of PPase, the complex of PPi-Cu(2+)-PPi is rapidly disassembled, and the fluorescence is re-quenched. This method is highly sensitive and selective for PPase detection, with a linear correlation between the fluorescence intensity and the PPase concentration in the range from 1 to 200 mU mL(-1) with a detection limit down to 1 mU mL(-1) (S/N = 3). Additionally, the inhibition effect of NaF on the PPase activity is also studied. Thus, the proposed method may hold a potential application in the diagnosis of PPase-related diseases and screening of PPase inhibitors, to evaluate the function and inhibition of PPase in biological systems.
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http://dx.doi.org/10.1039/c5an01937kDOI Listing
January 2016

Electrochemical immunosensor based on Pd-Au nanoparticles supported on functionalized PDDA-MWCNT nanocomposites for aflatoxin B1 detection.

Anal Biochem 2016 Feb 30;494:10-5. Epub 2015 Oct 30.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.

This paper reports a label-free electrochemical immunosensor for the determination of aflatoxin B1 (AFB1), which is based on a gold electrode modified by a biocompatible film of carbon nanotubes/poly(diallyldimethylammoniumchloride)/Pd-Au nanoparticles (CNTs/PDDA/Pd-Au). The nanocomposite was characterized by transmission electron microscopy and the electrochemical behavior of modified electrodes was investigated by cyclic voltammetry. The CNTs/PDDA/Pd-Au nanocomposites film showed good electron transfer ability, which ensured high sensitivity to detect AFB1 in a range from 0.05 to 25 ng mL(-1) with a detection limit of 0.03 ng mL(-1) obtained at 3σ (where σ is the standard deviation of the blank solution, n = 10). The proposed immunosensor provides a simple tool for AFB1 detection. This strategy can be extended to any other antigen detection by using the corresponding antibodies.
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http://dx.doi.org/10.1016/j.ab.2015.10.008DOI Listing
February 2016

New function of exonuclease and highly sensitive label-free colorimetric DNA detection.

Biosens Bioelectron 2016 Mar 22;77:879-85. Epub 2015 Oct 22.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China. Electronic address:

Enzymatic manipulation and modulation of nucleic acids are a central part of cellular function, protection, and reproduction, while rapid and accurate detection of ultralow amount of nucleic acids remains a major challenge in molecular biology research and clinic diagnosis of genetic diseases. Herein, we reported that exonuclease III can degrade the G-quadruplex structure, indicating the new exonuclease's function. Basing on the function of exonuclease III, a novel G-quadruplex-hemin DNAzyme-based colorimetric detection of tumor suppressor gene p53 was successfully developed. Although only one oligonucleotide probe was involved, the sensing strategy could suppress the optical background and achieve an efficient G-quadruplex-hemin DNAzyme-based signal amplification. Specifically, a label-free functional nucleic acid probe (called THzyme probe) was designed via introducing target DNA probe-contained hairpin structure into G-quadruplex DNAzyme. Even if this probe can fold into G-quadruplex structure in the presence of hemin very different from the double-stranded DNA, it is easily degraded by exonuclease III. Thus, no change in UV-vis absorption intensity is detected in the absence of target DNA. However, the hybridization of target DNA can protect the integrity and catalytic activity of THzyme probe, producing the DNAzyme-amplified colorimetric signal. As a result, the p53 gene was able to be detected down to 1.0 pM (final concentration in the signal-generating solution: 50.0 fM) and mismatched target DNAs were easily distinguished. It is expected that this simple sensing methodology for DNA detection can find its utility in point-of-care applications.
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http://dx.doi.org/10.1016/j.bios.2015.10.037DOI Listing
March 2016

Two-dimensional transition metal dichalcogenides as atomically thin semiconductors: opportunities and challenges.

Chem Soc Rev 2015 Dec 19;44(24):8859-76. Epub 2015 Oct 19.

State Key Laboratory of Chemo/Biosensingand Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, Hunan 410082, P. R. China.

The discovery of graphene has ignited intensive interest in two-dimensional layered materials (2DLMs). These 2DLMs represent a new class of nearly ideal 2D material systems for exploring fundamental chemistry and physics at the limit of single-atom thickness, and have the potential to open up totally new technological opportunities beyond the reach of existing materials. In general, there are a wide range of 2DLMs in which the atomic layers are weakly bonded together by van der Waals interactions and can be isolated into single or few-layer nanosheets. The van der Waals interactions between neighboring atomic layers could allow much more flexible integration of distinct materials to nearly arbitrarily combine and control different properties at the atomic scale. The transition metal dichalcogenides (TMDs) (e.g., MoS2, WSe2) represent a large family of layered materials, many of which exhibit tunable band gaps that can undergo a transition from an indirect band gap in bulk crystals to a direct band gap in monolayer nanosheets. These 2D-TMDs have thus emerged as an exciting class of atomically thin semiconductors for a new generation of electronic and optoelectronic devices. Recent studies have shown exciting potential of these atomically thin semiconductors, including the demonstration of atomically thin transistors, a new design of vertical transistors, as well as new types of optoelectronic devices such as tunable photovoltaic devices and light emitting devices. In parallel, there have also been considerable efforts in developing diverse synthetic approaches for the rational growth of various forms of 2D materials with precisely controlled chemical composition, physical dimension, and heterostructure interface. Here we review the recent efforts, progress, opportunities and challenges in exploring the layered TMDs as a new class of atomically thin semiconductors.
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http://dx.doi.org/10.1039/c5cs00507hDOI Listing
December 2015

Cyclodextrin supramolecular inclusion-enhanced pyrene excimer switching for time-resolved fluorescence detection of biothiols in serum.

Biosens Bioelectron 2015 Jun 3;68:253-258. Epub 2015 Jan 3.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China.

We report here an efficient pyrene excimer signaling-based time-resolved fluorescent sensor for the measurement of biothiols (cysteine (Cys), homocysteine (Hcy), glutathione (GSH)) in human serum based on thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination chemistry and the inclusion interaction of cyclodextrin. The sensing mechanism of the approach is based on the competitive ligation of Hg(2+) ions by Hcy/Cys/GSH and T-T mismatches in a bis-pyrene-labeled DNA strand with the self-complementary 5' and 3' ends. The introduction of γ-cyclodextrin can provide cooperation for the molecular level space proximity of the two labeled pyrene molecules, moreover the hydrophobic cavity of γ-cyclodextrin can also offer protection for the pyrene dimer's emission from the quenching effect of environmental conditions and enhance the fluorescence intensity of the pyrene excimer. When the biothiols are not presented, the sensing ensemble is in the "off" state due to the long distance between the two labeled pyrene molecules resulted from the formation of a more stable T-Hg(2+)-T structure. While in the presence of biothiols, Hg(2+) interacts very strongly with thiol groups and the T-Hg(2+)-T structure is dehybridized, and then the pyrene excimer will be formed due to the self-complementary 5' and 3' ends of the DNA probe and the cooperation interaction of γ-cyclodextrin to pyrene dimer, thus resulting in switching the sensing ensemble to the "on" state. In the optimum conditions described, the linear concentration range of 1.0-100 μM with the limit of detection (LOD) of 0.36 μM for GSH was obtained. Moreover, due to the much longer lifetime of the pyrene excimer fluorescence than those of the ubiquitous endogenous fluorescent components, the time-resolved fluorescence technique has been successfully used for application in complicated biological samples.
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http://dx.doi.org/10.1016/j.bios.2015.01.004DOI Listing
June 2015

A cell-targeted, size-photocontrollable, nuclear-uptake nanodrug delivery system for drug-resistant cancer therapy.

Nano Lett 2015 Jan 12;15(1):457-63. Epub 2014 Dec 12.

Molecular Science and Biomedicine Laboratory, State Key Laboratory for Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, College of Biology, and Collaborative Research Center of Molecular Engineering for Theranostics, Hunan University , Changsha 410082, China.

The development of multidrug resistance (MDR) has become an increasingly serious problem in cancer therapy. The cell-membrane overexpression of P-glycoprotein (P-gp), which can actively efflux various anticancer drugs from the cell, is a major mechanism of MDR. Nuclear-uptake nanodrug delivery systems, which enable intranuclear release of anticancer drugs, are expected to address this challenge by bypassing P-gp. However, before entering the nucleus, the nanocarrier must pass through the cell membrane, necessitating coordination between intracellular and intranuclear delivery. To accommodate this requirement, we have used DNA self-assembly to develop a nuclear-uptake nanodrug system carried by a cell-targeted near-infrared (NIR)-responsive nanotruck for drug-resistant cancer therapy. Via DNA hybridization, small drug-loaded gold nanoparticles (termed nanodrugs) can self-assemble onto the side face of a silver-gold nanorod (NR, termed nanotruck) whose end faces were modified with a cell type-specific internalizing aptamer. By using this size-photocontrollable nanodrug delivery system, anticancer drugs can be efficiently accumulated in the nuclei to effectively kill the cancer cells.
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http://dx.doi.org/10.1021/nl503777sDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4296921PMC
January 2015

Background eliminated signal-on electrochemical aptasensing platform for highly sensitive detection of protein.

Biosens Bioelectron 2015 Apr 24;66:363-9. Epub 2014 Nov 24.

State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China.

Using platelet-derived growth factor B chain dimer (PDGF-BB) as the model target, a background current eliminated electrochemical aptameric sensing platform for highly sensitive and signal-on detection of protein is proposed in this paper. Successful fabrication of the biosensor depends on ingenious design of aptamer probe, which contains the aptamer sequence for PDGF-BB and the recognition sequence for EcoRI endonuclease. In the absence of PDGF-BB, the ferrocene labeled aptamer probe folds into a hairpin structure and forms a recognition site for EcoRI. By treatment with endonuclease, the specific and cleavable double-stranded region is cut off and redox-active ferrocene molecule is removed from the electrode surface, and almost no peak current is observed. When binding with target protein, the designed aptamer probe changes its conformation and dissociates the recognition double strand. The integrated aptamer probe is maintained when exposing to EcoRI endonuclease, resulting in obvious peak current. Therefore, a signal-on and sensitive sensing strategy for PDGF-BB detection is fabricated with eliminated background current. Under the optimized experimental conditions, a wide linear response range of 4 orders of magnitude from 20pgmL(-1) to 200ngmL(-1) is achieved with a detection limit of 10pgmL(-1). Moreover, the present aptameric platform is universal for the analysis of a broad range of target molecules of interest by changing and designing the sequence of aptamer probe.
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http://dx.doi.org/10.1016/j.bios.2014.11.044DOI Listing
April 2015

Discovery of the unique self-assembly behavior of terminal suckers-contained dsDNA onto GNP and novel "light-up" colorimetric assay of nucleic acids.

Biosens Bioelectron 2015 Feb 6;64:292-9. Epub 2014 Sep 6.

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China. Electronic address:

Noble metal nanoparticles are currently of great interest because of their unique optical properties and potential applications in disease diagnostics and cancer treatment. In the present work, a discovery was reported that dsDNA with terminal thiols at its two ends could lie easily flat onto the gold nanoparticle (GNP) surface rather than cross linked different GNPs, indicating an unique self-assembly behavior of newly-designed molecules on GNPs. This could intensively stabilize gold nanoparticles against aggregation even at a high salt concentration. On the basis of this discovery, a novel light-up colorimetric sensing strategy was developed for the detection of p53 gene by combining with the cyclical nucleic acid strand-displacement polymerization (CNDP). For the described colorimetric system, GNPs require no any surface functionalization, and target recognition reaction and CNDP amplification could be conducted under the optimized conditions to achieve a high efficiency. The high detection sensitivity and desirable selectivity are achieved, and the potential practical application was demonstrated. Besides, this sensing system can function in a wide range of salts, making it a suitable platform to cooperate with many biological processes.
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http://dx.doi.org/10.1016/j.bios.2014.09.008DOI Listing
February 2015

Cell membrane-anchored biosensors for real-time monitoring of the cellular microenvironment.

J Am Chem Soc 2014 Sep 16;136(38):13090-3. Epub 2014 Sep 16.

Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, College of Biology, Collaborative Innovation Center for Molecular Engineering for Theranostics, Hunan University , Changsha, 410082, China.

Cell membrane-anchored biochemical sensors that allow real-time monitoring of the interactions of cells with their microenvironment would be powerful tools for studying the mechanisms underlying various biological processes, such as cell metabolism and signaling. Despite the significance of these techniques, unfortunately, their development has lagged far behind due to the lack of a desirable membrane engineering method. Here, we propose a simple, efficient, biocompatible, and universal strategy for one-step self-construction of cell-surface sensors using diacyllipid-DNA conjugates as the building and sensing elements. The sensors exploit the high membrane-insertion capacity of a diacyllipid tail and good sensing performance of the DNA probes. Based on this strategy, we have engineered specific DNAzymes on the cell membrane for metal ion assay in the extracellular microspace. The immobilized DNAzyme showed excellent performance for reporting and semiquantifying both exogenous and cell-extruded target metal ions in real time. This membrane-anchored sensor could also be used for multiple target detection by having different DNA probes inserted, providing potentially useful tools for versatile applications in cell biology, biomedical research, drug discovery, and tissue engineering.
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http://dx.doi.org/10.1021/ja5047389DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4183634PMC
September 2014

Highly-sensitive liquid crystal biosensor based on DNA dendrimers-mediated optical reorientation.

Biosens Bioelectron 2014 Dec 20;62:84-9. Epub 2014 Jun 20.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China. Electronic address:

A novel highly-sensitive liquid crystal (LC) biosensing approach based on target-triggering DNA dendrimers was developed for the detection of p53 mutation gene segment at the LC-aqueous interface. In this study, the mutant-type p53 gene segment was the target to trigger the formation of DNA dendrimers from hairpin DNA probes by hybridization chain reaction, and the latter as a 'signal enhancement element' further induced the LC reorientation from tilted to homeotropic alignment, resulting in a corresponding optical changes of LC biosensors from birefringent to honeycombed textures or dark framework. The distinct optical reorientational appearances can serve as a characteristic signal to distinguish target concentrations ranging from 0.08 nM to 8 nM. Moreover, these optical phenomena suggest that the LC reorientation is related to the electric-dipole coupling between the adsorbed DNA and LC molecules, the conformational constraints of DNA and the internal electric field induction upon hybridization. This label-free LC biosensing strategy can open up a new platform for the sensitive detection of specific DNA sequences and enrich the application scope of an LC biosensing technique.
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http://dx.doi.org/10.1016/j.bios.2014.06.029DOI Listing
December 2014