Homogeneous DNA Detection Based on Fluorescence Quenching by Nanoparticles in Single-step Format :Target-Induced Configuration Transform

A new strategy for homogeneous detection of DNA hybridization in single-step format was developed based on fluorescence quenching by gold nanoparticles. The gold nanoparticle is functionalized with 5’-thiolated 48-base oligonucleotide (probe sequence), whose 3’-terminus is labeled with fluorescein (FAM), a negatively charged fluorescence dye. The oligonucleotide adopts an extended configuration due to the electrostatic repulsion between negatively charged gold nanoparticle and the FAM-attached probe sequence. After addition of the complementary target sequence, specific DNA hybridization induces a conformation change of the probe from an extended structure to an arch-like configuration, which brings the fluorophore and the gold nanoparticle in close proximity. The fluorescence is efficiently quenched by gold nanoparticles. The fluorescence quenching efficiency is related to the target concentration, which allows the quantitative detection for target sequence in a sample. A linear detection range from 1.6 to 209.4 nmol/L was obtained under the optimized experimental conditions with a detection limit of 0.1 nmol/L. In the assay system, the gold nanoparticles act as both nanoscaffolds and nanoquenchers. Furthermore, the proposed strategy, in which only two DNA sequences are involved, is not only different from the traditional molecular beacons or reverse molecular beacons but also different from the commonly used sandwich hybridization methods. In addition, the DNA hybridization detection was achieved in homogenous solution in a single-step format, which allows real-time detection and quantification with other advantages such as easy operation and elimination of washing steps.     

A supramolecular fluorescent probe based on cucurbit[10]uril for sensing the pesticide dodine

We report herein a new fluorescent probe for the selective recognition and determination of dodine among 20 different pesticides.This fluorescent probe was assembled through host-guest complexation between cucurbit[10]uril(Q[10]) and aminopropyl-1-pyrenebutanamide(PBA) and is designated as PBA@Q[10].Addition of dodine to PBA@Q[10] results in a dramatic enhancement of fluorescence intensity at 390 nm,accompanied by fluorescence quenching at 488 nm.On this basis,the detection limit is 6.78 × 10^-7 mol/L.The response mechanism is a competitive interaction:dodine occupies the cavity of Q[10] and forces PBA to leave.     

Highly luminescence manganese doped carbon dots

Heteroatom doped carbon dots(CDs) with distinct merits are of great attractions in various fields such as solar cells, catalysis, trace element detection and photothermal therapy. In this work, we successfully synthesized blue-fluorescence and photostability manganese-doped carbon dots(Mn-CDs) with a quantum yield up to 7.5%, which was prepared by a facile one-step hydrothermal method with sodium citrate and manganese chloride. The Mn-CDs is the high mono-dispersity, uniform spherical nanoparticles. The Mn element plays a critical role in achieving a high quantum yield in synthesis of carbon dots, which was confirmed by the structure analysis using XPS and FTIR. Spectroscopic investigations proved that the decent PLQY and luminescence properties of Mn-CDs are due to the heteroatom doped, oxidized carbon-based surface passivation. In addition, the Mn-CDs are demonstrated as promising fluorescent sensors for iron ions with a linear range of 0–500 mmol/L and a detection limit of2.1 nmol/L(turn-off), indicating their great potential as a fluorescent probe for chemical sensing.     

Coumarinocoumarin-based fluorescent probe for the sensitive and selective detection of hydrazine in living cells and zebra fish

A coumarinocoumarin-based fluorescent probe,JCCA,was developed for the detection of N2 H4.JCCA exhibited a fast turn-on fluorescence enhancement in response to N2 H4 with good selectivity,sensitivity and a detection limit of 7.4 nmol/L.Significantly,JCCA displayed a good capability for visualizing N2 H4 in living cells and zebra fish.     

A new fluorescent probe with ultralow background fluorescence for imaging of endogenous cellular selenol under oxidative stress

A new fluorescent probe (Rhod-Sec) for selenol detection with ultralow background fluorescence have been developed in this paper, which showed a 380-fold off-on fluorescence response, and can be applied to visualize the fluctuation of selenol in HepG2 cells through LPS-induced cells oxidation resistance.     

Naphthalimide-rhodamine based fluorescent probe for ratiometric sensing of cellular pH

The pH values of lysosomes in cancer cells is slightly lower than that in normal cells, which can be used to distinguish cancer cells from normal cells. According to this, a naphthalimide-rhodamine based fluorescent probe(hereafter referred to as RBN) with a pK_a of 4.20 was designed and synthesized for ratiometric sensing of cellular pH via fluorescence resonance energy transfer(FRET), which can respond to different pH precisely through ratiometric fluorescence intensity(Ⅰ_(577)/Ⅰ_(540)). RBN can be employed to distinguish cancer cells from normal cells on the basis of different fluorescent response, in particular, RBN showed excellent water solubility and low cell toxicity, all these are quite significant for potential application in cancer diagnose and therapy.     

Fluorescein-derived fluorescent probe for cellular hydrogen sulfide imaging

In this work, a fluorescein-derived fluorescent probe for H2 S based on the thiolysis of dinitrophenyl ether is reported. This probe exhibits turn-on fluorescence imaging of H2 S in living cells and bulk solutions with excellent selectivity. The reaction mechanism was explained by means of absorption, fluorescence and HPLC–MS.     

The specific detection of Cu(Ⅱ) using an AIE-active alanine ester

Cu(Ⅱ) detection is important because it plays crucial role in several biological processes and ecological systems.Fluorescent techniques have attracted more and more attention in Cu(Ⅱ) detection.In this report,we contribute a novel strategy to use fluorescence spectroscopy for Cu(Ⅱ) specific detection.The specificity relies on the fact that,of the many metal cations,only Cu(Ⅱ) can catalyze the hydrolyzation of a-amino acid ester.The novelty originates from the unique aggregation-induced emission(AIE) property of the fluorescent label.We designed a model a-amino acid ester(TPE-Ala) constructed with alanine and tetraphenylethene-functionalized methanol(TPE-methanol).In comparison with the precursor TPE-Ala, TPE-methanol has lower solubility and is easy to form aggregates in water,thereby displaying a higher fluorescent response.Thus,the Cu(Ⅱ) catalyzed hydrolyzation can be monitored by recording the fluorescence enhancement and fluorescent detection Cu(Ⅱ) is rationally achieved.     

Bioactivated in vivo assembly(BIVA) peptide-tetraphenylethylene(TPE) probe with controllable assembled nanostructure for cell imaging

The emergence of fluorescent light-up molecular probe, which can specifically turn on their fluorescent in the presence of stimulation factors, has open up a new opportunity to advance biosensing and bioimaging. In this work, we designed and synthesized a peptide-AIE conjugate probe for cell imaging with controlled in situ assembled nanostructures. The modular designed probe is consisted of a selfassembled peptide-tetraphenylethene(TPE) motif, a fibroblast activation protein alpha(FAP-α)responsive motif, a hydrophilic motif and a targeting motif. The probe exhibits typically turn-on fluorescence property specifically triggered by FAP-α, which is a significant overexpressed membrane protein on pancreatic tumor cells. Interestingly, the peptide modified the TPE dramatically impacts the assembled nanostructure, which can be modulated by peptide sequences. As a result, the peptide FF(PhePhe) modification of TPE as the self-assembled motif provides a suitable balance of the probe with lightup property and nanofiber assembled structure in situ. Finally, our probe could effectively detect the FAP-α on tumor cells with high specificity. Meantime, the nanofibers in situ assembled on the surface of CAFs enhanced the probe accumulation and prolonged the retention for cell imaging. We envision that this study may inspire new insights into the design of nanostructure controlled AIE light-up bio-probe.     

Ratiometric Fluorescent Probe Based on Novel Red-emission BODIPY for Determination of Bovine Serum Albumin

A novel red-emission boron-dipyrromethene（BODIPY） dye with a pyrrole ring was synthesized simply via one-pot reaction. The spectral properties of it were investigated under the conditions of different solvents. The results show that the as-prepared BODIPY dye is extremely sensitive to solvent polarity, and the fluorescent emission enhances with the decrease of solvent polarity. In aqueous buffer, the addition of bovine serum albumin leads to a ratiometric change in absorption spectra with an association constant of 1.16×10^6 L/mol. Meanwhile, the fluorescence emission increases greatly at 622 nm but changes slightly at 575 nm. The response time is very short（less than 3 min）, and the changes of color can be noticed by naked eyes. Bovine serum albumin can be detected by this ratiometric fluorescence probe, but other proteins or enzymes cannot be detected by this method, which indicates that this novel dye has high selectivity towards bovine serum albumin. The reason is that bovine serum albumin has suitable hydro- phobic cavities for binding with the dye. In addition, the dye molecule can penetrate cell membrane easily and make a fast fluorescent stain, which makes it a potential probe for living-cell fluorescence imaging.     

Direct and single-step sensing of primary ovarian cancers related glycosidases

High sensitive, accurate detection for tumor-associated overexpressed enzyme activity is highly significant for further understanding enzyme function, discovering potential drugs, and early diagnosis and prevention of diseases. In this work, we developed a facile, direct and single-step detection platform for primary ovarian cancers related glycosidase activity based on the inner filter effect(IFE) between glycosidase catalytic product and black phosphorus quantum dots(BPQDs). Highly fluorescent BPQDs were successfully synthesized from bulk black phosphorus by a simple liquid exfoliation method. Under the catalysis of β-galactosidase, p-nitrophenyl-β-D-galactopyranoside(PNPG) was transformed into pnitrophenol(PNP) and β-D-galactopyranoside. Meanwhile, the absorption of catalytic product PNP greatly overlapped with the excitation and emission spectra of fluorescent BPQDs, leading to the fluorescence quenching of BPQDs with a high quenching efficiency. The proposed sensing strategy provided a low detection limit of 0.76 U/L, which was 1 — 2 orders of magnitude lower than most unmodified sensing platforms. D-Galactal was selected as the inhibitor for β-galactosidase to further assess the feasibility of screening potential inhibitors. The fluorescence recovery of BPQDs suggests that the unmodified sensing platform is feasible to discover potential drugs of β-galactosidase. Our work paves a general way in the detection of glycosidase activity with fluorescent BPQDs, which can be promising for glycosidase-related disease diagnosis and pathophysiology elucidation.     

Synthesis of a flavonoid fluorescent probe for the detection of sulfur dioxide derivatives and cell imagingEI北大核心CSCD

A novel fluorescent probe HMQC was synthesized for HSOf detection by coupling flavonoid derivatives with 3-quinoline salt. In PBS buffer solution, the probe showed high selectivity, good sensitivity (58 nmol/L) and rapid response (150 s) for the detection of HSO3−. The possible sensing mechanism of the probe was discussed by nuclear magnetic hydrogen spectroscopy, mass spectrometry and theoretical calculation, indicating that the addition reaction between HSO3− and the C=C bond of the probe led to the fluorescence enhancement. The probe HMQC could be used for the detection of HSO3− in living cells, making it to be a promising tool for delecting HSO3−. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

A highly efficient and selective probe for F- detection based on 1H-imidazo[4,5-b]phenazine derivative

A new colorimetric and fluorimetric chemosensor for F detection based on 1H-imidazo[4,5-b]phenazine derivative has been designed and synthesized.It shows excellent fluorescent specific selectivity and sensitivity for F in DMSO solution.Upon addition of F to the solution of probe 1,a remarkable color change from yellow to red could be observed easily by the naked-eye.The detection limit of this probe toward F is 6.2 10 6mol/L.Analysis by1 H NMR proved that the imidazolyl N–H could be hydrogen-bonded with added fluoride anions,and results in the difference of colors.     

A simple,water-soluble,Fe3+-selective fluorescent probe and its application in bioimaging

A simple,water-soluble,Fe³⁺-selective fluorescent probe,derived from rhodamine B,was synthesized and characterized.The probe exhibits a fluorescence response toward Fe³⁺ with acceptable sensitivity and selectivity and even facilitates visual or naked-eye detection of Fe³⁺.The experiment results show that the response of the probe to Fe³⁺ is pH-independent over a wide range of 4.0-10.0.In addition,fluorescence microscopic imaging experiments have proven that the probe is cell permeable and can be used for monitoring intracellular Fe³⁺ in living cells.     

A squaraine based fluorescent probe for mercury ion via coordination induced deaggregation signaling

Due to the high affinity between dithiocarbamate(DTC) and Hg2+,a fluorescent probe based on squaraine chromophore with DTC side arm for Hg2+via coordination induced deaggregation signaling has been designed and synthesized.Squaraine has a high tendency to aggregate in aqueous solution,and such self-aggregation usually results in a dramatic absorption spectral broadening with fluorescence emission quenching.The combination of the DTC side arm of the probe with Hg2+induces steric hindrance,leading to the deaggregation of the dye complex,companying with a fluorescence emission restoration.In EtOH–H2O(20:80,v/v) solution,this ‘‘turn on' fluorescent probe has high selectivity and sensitivity toward Hg2+over other metal ions,and the limit of detection for Hg2+was estimated as2.19 ? 10à8mol/L by 3s/k.     

Anaphthalimide-based fluorescent probe for mercaptocontaining compounds

A polarity-sensitive fluorescent probe MNP was rationally designed and synthesized with naphthalimide as the fluorophore and maleimide as the receptor for thiols. MNP is weakly fluorescent due to the photoinduced electron-transfer(PET) from the fluorophore to the receptor, and it displays evidently solvatochromic UV–vis and fluorescence spectra: the emission shifted from 495 nm in n-hexane to545 nm in phosphate buffer solution. Michael addition reaction between thiols and the maleimide in MNP inhibited the PET process, which led to about eight-fold fluorescence enhancement. In addition,MNP showed highly sensitivity to mercapto-containing proteins and it could detect as low as 20.4 mg/m L of BSA in PBS. MNP has potential in fluorescent imaging of thiols in living cells.     

A near-infrared fluorescent probe for monitoring fluvastatin-stimulated endogenous H2S production

Most reported fluorescent probes have limitations in practical applications in living systems due to the strong autofluorescence background,construction of probes with near-infrared(NIR) fluorescence emission is an accessible approach for addressing this challenge.We here designed a NIR fluorescent probe for monitoring the endogenous production of H_2S in living cells.The designed probe showed significant NIR fluorescence turn-on response to H_2S with high selectivity,enabling the sensitive detection H_2S.Importantly,the probe could be applied in monitoring the endogenous production of H_2S in raw 264.7 macrophages.This study showed that fluvastatin can promote the activity of cystathionineγ-lyase(CSE) for generation H_2S.     

Sensitive and enzyme-free detection for single nucleotide polymorphism using microbead-assisted toehold-mediated strand displacement reaction

This report described a free-enzyme, convenient and inexpensive genotyping biosensor capable of detecting single nucleotide polymorphism at normal temperature based on the combination of toeholdmediated strand displacement reaction(toehold-SDR) and microbead-capture technique. The biosensor consists of a pre-hybridized strand formed by a reporter probe and a capture probe. In the presence of a mutant sequence, there is no toehold-mediated strand displacement and the reporter probe cannot be released from the pre-hybridized strand. Microbeads capture the fluorescent pre-hybridized strand through biotin–streptavidin interaction, so microbeads give out significant fluorescence signal, while there is no fluorescence in the solution. However, in the presence of a matched target, the strand displacement is effectively initiated and the reporter probe is released from pre-hybridized strand. After adding microbeads, the solution produces bright fluorescence, while microbeads have no obvious signal.Genotypes are identified conveniently according to the fluorescence intensity of the solution. The method provides a simple and inexpensive strategy to detect point mutation. Moreover, this biosensor shows the linear relationship in the range of 1–40 nmol/L and reaches a detection limit of 0.3 nmol/L.     

Switch-on fluorescence sensor for ascorbic acid detection based on MoS2 quantum dots-MnO2 nanosheets system and its application in fruit samples

In this work,molybdenum disulfide quantum dots(MoS_2 QDs) were firstly prepared by hydrothermal method using sodium molybdate and glutathione as precursors,and applied in ascorbic acid detection.When joining MnO_2 nanosheets into MoS_2 QDs solution,they produced an obvious fluorescence quenching,which should be due to inner filter effect(IFE).Meanwhile,the fluorescent probe was formed,Interestingly,we found that this quenching phenomenon disappeared with the addition of ascorbic acid,In other words,the fluorescence gradually restored.This recovery phenomenon is mainly due to the reduction effect of ascorbic acid for MnO_2 nanosheets.Under the optimum conditions,the limit of detection(LOD) of 39 nmol/L for ascorbic acid was achieved with a linear range of 0.33-5.00 μmol/L.The repeatability was better than 5.0% for ascorbic acid in both standard and fruit samples(n = 3).Moreover,the as-fabricated fluorescent sensing system was successfully employed to detect the ascorbic acid levels in hawthorn and jujube with satisfactory results.