Fluorescent film sensor for copper ion based on an assembled monolayer of pyrene moieties

We previously reported the construction of a family of fluorescent film sensors for organic copper salts by covalently coupling polycyclic aromatic hydrocarbons on epoxy-terminated self-assembled monolayers on glass plate surfaces. Here we investigate the sensing properties and mechanism of covalently coupling pyrene on a glass plate surface via a long flexible "Y" type spacer. X-ray photoelectron spectroscopy (XPS) and fluorescence spectra measurements demonstrate the covalent attachment of pyrene in our adlayer. Compared with those results obtained in the previous studies, this new film sensor did not show highly selectivity for organic copper salts, which can be attributed to the introduction of sulfonyl groups connecting the pyrene moieties and the spacers. The presence of sulfonyl units made the microenvironments of pyrene relatively hydrophilic and thus showed less screening effect for inorganic ions. The specificity and reversibility of the film sensor toward Cu (II) made it attractive for sensing applications.     

核苷磷酸盐对含双芘侧链荧光敏感器化合物的荧光猝灭与分子识别

合成了一种在水溶液中对核苷磷酸盐ATP,ADP,AMP阴离子具有识别能力的荧光化学敏感器分子---化合物1。通过检测化合物1在水溶液中芘激基缔合物荧光发射强度随核苷磷酸盐、腺嘌呤等的加入而引起的变化,求出不同核苷磷酸盐及腺嘌呤对芘激基缔合物荧光发射的猝灭常数,并进行了比较研究。利用荧光发射强度随不同核苷磷酸盐引入而发生的变化计算出化合物1对不同核苷磷酸盐进行配位的配位稳定常数。结果表明所合成的化合物1对ATP有着良好的识别力选择功能。此外,还利用分子力学的计算方法对化合物1及其与核苷磷酸盐形成配合物后的分子构象及几何尺寸作了计算,并结合实验结果进行了初步讨论。     

Binding and Sensing Properties of a Hybrid Naphthalimide–Pyrene Aza-Cyclophane towards Nucleotides in an Aqueous Solution

Selective recognition of nucleotides with synthetic receptors is an emerging direction to solve a series of nucleic acid-related challenges in biochemistry. Towards this goal, a new aza-cyclophane with two different dyes, naphthalimide and pyrene, connected through a triamine linker has been synthesized and studied for the ability to bind and detect nucleoside triphosphates in an aqueous solution. The receptor shows Foerster resonance energy transfer (FRET) in fluorescence spectra upon excitation in DMSO, which is diminished dramatically in the presence of water. According to binding studies, the receptor has a preference to bind ATP (adenosine triphosphate) and CTP (cytidine triphosphate) with a “turn-on” fluorescence response. Two separate emission bands of dyes allow one to detect nucleotides in a ratiometric manner in a broad concentration range of 10⁻⁵–10⁻³ M. Spectroscopic measurements and quantum chemical calculations suggest the formation of receptor–nucleotide complexes, which are stabilized by dispersion interactions between a nucleobase and dyes, while hydrogen bonding interactions of nucleobases with the amine linkers are responsible for selectivity.     

FRET- and PET-based sensing in a single material: expanding the dynamic range of an ultra-sensitive nitroaromatic explosives assay

A polyethylenimine polymer derivatized with pyrene moieties suitable for the fluorescence-based detection of nitroaromatic explosives (NAC) in aqueous systems is described. The system exhibits an exceptionally wide dynamic sensing range of 7 orders of magnitude (from 33 ppt to 225 ppm TNT or Tetryl). This broad range was achieved by the combination of FRET and PET sensing mechanisms in a single material. The sensing material is suitable for a paper strip assay. Simplicity, selectivity, and the wide dynamic range suggest this material for explosives detection in the field.     

Nucleotide recognition by protonated aminoglycosides

Interactions of protonated forms of kanamycin A with nucleotides and several simple phosphate anions have been studied by potentiometric and NMR titrations. The affinity of kanamycin A to anions is comparable to that observed with other aliphatic polyammonium receptors of similar charge, but it discriminates triphosphate nucleotides with different nucleobases with binding constants following the order GTP?CTP ≈ ATP. Kanamycin A also binds the respective uncharged nucleosides with the same selectivity. Binding of ATP is exothermic with a negative entropic contribution in contrast to what is expected for simple ion pairing. Other tested aminoglycosides, amikacin and streptomycin, bind ATP less efficiently than kanamycin A. Models of structures of kanamycin A complexes with ATP and GTP obtained by molecular mechanics (OPLS-2005) calculations based on ¹H and ³¹P NMR data confirm the possibility of nucleotide discrimination by simultaneous ion pairing of terminal nucleotide phosphate groups with ammonium sites of rings B and C and hydrogen bonding of the nucleobase at the ring A of the aminoglycoside.     

Novel bifunctional viologen-linked pyrene conjugates: Synthesis and study of their interactions with nucleosides and DNA

With the objective of developing efficient DNA oxidizing agents, a new series of viologen-linked pyrene conjugates with the general formula PYLnV(2+), having a different number of methylene spacer units (Ln) was synthesized, and their interactions with nucleosides and DNA have been investigated through photophysical and biophysical techniques. The viologen-linked pyrene derivatives PYL1V(2+) (n =equals; 1), PYL7V(2+) (n = 7), and PYL12V(2+) (n = 12) exhibited characteristic fluorescence emission of the pyrene chromophore centered around 380 nm but with significantly reduced yields when compared to those of the model compound PYL1Et(3)(+). The fluorescence quenching observed in these systems is explained through an electron-transfer mechanism based on a calculated favorable change in free energy (DeltaG(ET) = -1.59 eV), and the redox species characterized through laser flash photolysis studies. Intramolecular electron-transfer rate constants (k(ET)) were calculated from the observed fluorescence yields, and the singlet lifetimes of the model compound and are found to decrease with increasing spacer length. The DNA binding studies of these systems through photophysical, chiroptical, and viscometric techniques demonstrated that these systems effectively undergo DNA intercalation with association constants (KDNA) in the range of 1.1-2.6 x 10(4) M(-1) and exhibit 2:1 sequence selectivity for poly(dG) x poly(dC) over poly(dA) x poly(dT). Photoactivation of these systems initiates electron transfer from the singlet excited state of the pyrene chromophore to the viologen moiety followed by an electron transfer from DNA to the oxidized pyrene. This results in the formation of stable charge-separated species such as radical cations of both DNA and reduced viologen as characterized by laser flash photolysis studies and subsequently the oxidized DNA modifications. These novel systems are soluble in buffer media, stable under irradiation conditions, and oxidize DNA efficiently and selectively through a cosensitization mechanism and hence can be useful as photoactivated DNA cleaving agents.     

A novel fluorescent probe for formaldehyde based-on monomer-excimer conversion and its imaging in live cells

A novel fluorescent probe was developed for formaldehyde, which can be synthesized by one-step Buchwald–Hartwig reaction. When hydrazino-group of probe reacted with formaldehyde, hydrophobic reaction product aggregates into nanoparticles and results in the blue fluorescence due to the monomer-excimer effect. With enough sensitivity, high selectivity, good stability in physiological pH range and excellent biocompatibility, this probe can image formaldehyde in living cells.     

A general and versatile molecular design for host molecules working in water: a duplex-based potassium sensor consisting of three functional regions

A general and versatile molecular design for host molecules was proposed based on the structural motif of antibodies. A water-soluble potassium sensor was developed by this molecular design, which consists of three functional regions, benzo-15-crown-5 ether, DNA, and pyrene as guest-binding, dimerising, and signaling sites, respectively. The molecular sensor emitted the monomer fluorescence of the pyrene fluorophore predominantly when existing as a random structure, while it formed a duplex upon recognition of K+ to bring about monomer-excimer emission switching.     

Exploring the binding ability of polyammonium hosts for anionic substrates: selective size-dependent recognition of different phosphate anions by bis-macrocyclic receptors

Binding of mono-, di-, and triphosphate, adenosine diphosphate (ADP), and adenosine triphosphatase (ATP) with receptors L1-L3, composed of two [9]aneN(3) units separated by a 2,9-dimethylene-1,10-phenanthroline (L1), a 2,6-dimethylenepyridine (L2), or a 2,3-dimethylenequinoxaline (L3) spacer, has been studied by means of potentiometric titrations, (1)H and (31)P NMR measurements in aqueous solutions, and molecular modeling calculations. In the case of inorganic phosphates, the binding properties of the receptors appear to be determined by their geometrical features, in particular the distance between the two [9]aneN(3) units imposed by the spacer separating the two macrocyclic units. While L1 is able to selectively bind triphosphate over di- and monophosphate, L3 selectively coordinates the smaller monophosphate anion. Finally, L2 shows preferential binding of diphosphate. (1)H and (31)P NMR measurements show that the complexes are essentially stabilized by charge-charge and hydrogen-bonding interactions between the anion and the protonated amine groups of the macrocyclic subunits of the receptors. Molecular dynamics simulations suggest that the larger distance between the two macrocyclic units of L1 allows this receptor to form a larger number of hydrogen-bonding contacts with triphosphate, justifying its selectivity toward this anion. Conversely, in the case of L3, the two facing [9]aneN3 units give rise to a cleft of appropriate dimensions where the small monophosphate anion can be conveniently hosted. Considering nucleotide coordination, L1 is a better receptor for ATP and ADP than L2, thanks to the higher ability of phenanthroline to establish stabilizing π stacking and hydrophobic interactions with the adenine units of the guests.     

Differential receptors create patterns diagnostic for ATP and GTP

Herein we report the combination of a library of resin-bound sensors along with a multicomponent sensor array. This novel combinatorial array sensor system shows selectivity for nucleotide phosphates in solution. The design of the anchored receptor includes a 1,3,5-trisubstituted-2,4,6-triethylbenzene scaffold coupled with peptide libraries. Each chemosensor is placed into a micromachined cavity within a silicon wafer, and the optical changes observed by a charged-coupled device result in near-real-time digital analysis of solutions. A colorimetric displacement assay was performed, and time-dependent imaging studies of the selected sensing ensembles result in a differential responses upon addition of adenosine 5'-triphosphate (ATP), adenosine 5'-monophosphate (AMP), or guanosine 5'-triphosphate (GTP). An advantage to this approach is that it creates an array of sensors that gives a fingerprint response for each analyte. Principal component analysis indicates that the library of chemosensors can differentiate between ATP, GTP, and AMP. On the basis of factor loading values, individual sensors from the library were sequenced to elucidate their chemical composition.     

Oligonucleotide-based label-free Hg2+ assay with a monomer-excimer fluorescence switch

A novel fluorescent Hg(2+) sensor was developed based on the T-Hg(2+)-T structure and a thioflavine T monomer-excimer fluorescent switch. Under optimum conditions, the selectivity is remarkably high, and Hg(2+) can be quantified over the dynamic range of 0.1 to 1.2 μM, with a limit of detection (LOD) of ~20 nM and a linear correlation coefficient of 0.995.     

Optical chemosensor for Ag+, Fe3+, and cysteine: information processing at molecular level

A thiacalix[4]arene based chemosensor 3 bearing two pyrene groups has been synthesized which demonstrates ratiometric sensing with Ag(+) and fluorescence quenching with Fe(3+) ions in mixed aqueous media. The 'in situ' prepared Ag(+) and Fe(3+) complexes showed high selectivity toward cysteine. The molecular switching between three chemical inputs (Ag(+), Fe(3+), cysteine) results in various molecular logic gates which have been integrated sequentially to generate a sequential information processing device.     

Highly sensitive gold nanoparticle-based colorimetric probe for phytate detection with high selectivity over various phosphate derivatives

A competitive-assay-based colorimetric sensing system for phytate was developed using a combination of [Zn₃(1,3,5-tris[bis(pyridine-2-ylmethyl)aminomethyl]-2,4,6-triethylbenzene)]⁶⁺ as the receptor unit for the phytate and 11-mercaptoundecylphosphoric acid functionalized gold nanoparticles as the reporter unit. The detection limit of this assay system is ∼100 times more sensitive than that reported for colorimetric probes and is compatible with the high sensitivity of previous fluorescent probes. The proposed sensing system can easily detect phytate at less than ∼300 nM with the naked eye. Unlike previous sensing systems, this design provides a high selectivity for phytate over various phosphate derivatives, including ATP, pyrophosphate, and inositol trisphosphate, and works well over a broad pH range.     

Universal hybridization using LNA (locked nucleic acid) containing a novel pyrene LNA nucleotide monomer

A novel pyrene LNA nucleotide monomer is shown to mediate universal hybridization when incorporated into a DNA strand or a 2'-OMe-RNA/LNA chimeric strand. For the latter, high-affinity universal hybridization without compromising the base-pairing selectivity of bases neighbouring the universal pyrene LNA nucleotide monomer is documented.     

基于磁性辅助的杂交链反应放大检测三磷酸腺苷

本文提出了一种基于磁性辅助的杂交链反应放大检测三磷酸腺苷(ATP)的传感策略。磁性纳米粒子表面易于修饰,而且操作方便,具有很好的分离效果,能够提高生物传感的选择性。首先,利用生物素与链霉亲和素之间的亲和力作用,将生物素标记的ATP核酸适配体连接到链霉亲和素修饰的磁性纳米粒子表面,加入与ATP核酸适配体互补的一段DNA进行杂交,通过磁性分离除去未杂交上的DNA,加入靶向ATP,ATP与其适配体特异性结合将适配体的互补链通过磁性分离出来,磁性分离出的信号DNA继续用于下一步的杂交链反应,将信号放大,最后利用氧化石墨烯(GO)对荧光的猝灭效应降低背景荧光,达到高灵敏度、高选择性检测靶向ATP。其中,ATP的最低检测浓度为0.1nmol/L。     

β-Cyclodextrin polymer based fluorescence enhancement method for sensitive adenosine triphosphate detection

A sensitive and facile method for adenosine triphosphate detection has been developed that based on the prominent fluorescence enhancement capability of β-cyclodextrin polymer to pyrene through host-gest interaction.     

A gold nanoparticle-based colorimetric sensing ensemble for the colorimetric detection of cyanide ions in aqueous solution

A colorimetric sensing ensemble was prepared by mixing readily prepared adenosine triphosphate (ATP)-stabilized AuNPs with Cu²⁺-phenanthroline complexes. The sensing mechanism of the ensemble was examined by UV-vis spectrometry and transmission electron microscopy. The studies showed that the Cu²⁺-phenanthroline complex was converted to free phenanthroline when exposed to cyanide anions and the free phenanthroline caused the ATP-stabilized AuNPs to aggregate, which in turn, resulted in a visible color change in the AuNP solution. The ensemble could detect cyanide ions in aqueous solution at physiological pH, either spectrophotometrically or visually, with high selectivity toward cyanide anions over a range of mono- and di-anions commonly found in biological and environmental systems. This sensing ensemble also allows a quantitative assay of the analyte in a neutral aqueous solution, down to a concentration of 10⁻⁵ M.     

Pyrene-Based “Turn-Off” Probe with Broad Detection Range for Cu2+, Pb2+ and Hg2+ Ions

Detection of metals in different environments with high selectivity and specificity is one of the prerequisites of the fight against environmental pollution with these elements. Pyrenes are well suited for the fluorescence sensing in different media. The applied sensing principle typically relies on the formation of intra- and intermolecular excimers, which is however limiting the sensitivity range due to masking of e. g. quenching effects by the excimer emission. Herein we report a highly selective, structurally rigid chemical sensor based on the monomer fluorescence of pyrene moieties bearing triazole groups. This sensor can quantitatively detect Cu²⁺, Pb²⁺ and Hg²⁺ in organic solvents over a broad concentrations range, even in the presence of ubiquitous ions such as Na⁺, K⁺, Ca²⁺ and Mg²⁺. The strongly emissive sensor's fluorescence with a long lifetime of 165 ns is quenched by a 1 : 1 complex formation upon addition of metal ions in acetonitrile. Upon addition of a tenfold excess of the metal ion to the sensor, agglomerates with a diameter of about 3 nm are formed. Due to complex interactions in the system, conventional linear correlations are not observed for all concentrations. Therefore, a critical comparison between the conventional Job plot interpretation, the method of Benesi-Hildebrand, and a non-linear fit is presented. The reported system enables the specific and robust sensing of medically and environmentally relevant ions in the health-relevant nM range and could be used e. g. for the monitoring of the respective ions in waste streams.     

Identification and quantification of polynuclear aromatic compounds in synthoil by room-temperature phosphorimetry

Room-temperature phosphorimetry (r.t.p.) is used to identify and quantify polynuclear aromatic compounds in a synthetic fuel (Synthoil). Several trace and major components, benzo[a]pyrene, chrysene, fluorenes, fluoranthene, phenanthrene, and pyrene, have been identified and determined at concentrations ranging from tens to thousands of parts-per-million. The selectivity of the r.t.p. analysis is greatly improved by using selective heavy-atom perturbation and synchronous excitation scanning.     

Acoustic quantification of ATP using a quartz crystal microbalance with dissipation

A quartz crystal microbalance with a dissipation monitoring (QCM-D) sensor was developed for highly sensitive and specific detection of adenosine-5'-triphosphate (ATP) by using an aptamer. The binding of ATP molecules on the aptamer films could be calculated as accurate mass changes using multiple frequency and dissipation measurements. The detection is achieved by calculating the mass changes from conformational rearrangements of the sensor surface upon interaction with the target. The sensor was demonstrated to respond to changes in ATP concentrations in real time suitable for continuous monitoring applications. This sensor showed excellent selectivity toward ATP compared with other chemically similar nucleotide GTP. The feasibility of the sensor was demonstrated by analyzing ATP concentrations in cell culture media with serum. The maximum frequency change was about -2 Hz after injection of 500 μM ATP. The affinity constant of the aptamer was determined to be 49 ± 7.59 μM. The proposed sensor can extend the application of the QCM-D system in medical diagnosis, and could be adopted for the detection of other small molecules with the use of specific aptamers.