First generation poly(propyleneimine) dendrimers functionalised with 1,8-naphthalimide units as fluorescence sensors for metal cations and protons

The synthesis of two new green fluorescent poly(propyleneimine) dendrimers from first generation has been described. The new materials are comprised of a 1,8-naphthalimide fluorophore having a substituent at C-4 position. The substituent in the first case is a N,N-dimethylaminoethylamino group while in the second one it is N-methylpiperazine. The spectroscopic and photophysical characteristics of the new dendrimers determined in organic solvent of different polarity have been presented. Both dendrimers show substantial increases in their fluorescence intensity in the presence of metal cations (Zn²⁺, Co²⁺, Ni²⁺, Pb²⁺, Mn²⁺, Cu²⁺, Fe³⁺ and Ag⁺) and protons. The influence of the photoinduced electron transfer on their sensing properties has been discussed.     

Studying the photophysical properties of a polymerizable 1,8‐naphthalimide dye and its copolymer with styrene as potential fluorescent sensors for metal cations

The photophysical characteristics of a polymerizable 1,8‐naphthalimide dye and its copolymer with styrene have been investigated. The functional properties of both low and high molecular weight fluorophores in the presence of different metal cations have been discussed with regard to their potential application as fluorosensors for the metal cations and protons. In acetonitrile solution the monomeric 1,8‐naphthalimide enhances its fluorescence emission in the presence of metal cations (Zn²⁺, Fe³⁺, Co²⁺, Pb²⁺, Cu²⁺, Ni²⁺, and Mn²⁺). In aqueous media the poly(St‐co‐MD) exhibits a selective response to Fe³⁺ cations. The monomeric and polymeric fluorophores also exhibit a considerable increase in their fluorescence intensity at acidic pH values (pH < 6) which suggest that they could be used as ON–OFF probes in analytical devices for signaling the presence of protons. Copyright © 2008 John Wiley & Sons, Ltd.     

A novel blue fluorescent chemosensor for metal cations and protons,based on 1,8‐naphthalimide and its copolymer with styrene

A new blue emitting 2‐allyl‐6‐(2‐dimethylaminoethyloxy)‐benzo[de]isoquinoline‐1,3‐dione, bearing an allylic group has been designed and synthesized. Bulk radical copolymerization has been carried out in order to prepare a fluorescent copolymer, based on styrene. The main photophysical characteristics of the monomeric and polymeric fluorophores have been investigated both in the absence and presence of metal cations and protons. It has been found that the monomeric naphthalimide can be used as a sensor for protons and Zn²⁺, Ni²⁺, Ce³⁺, Cu²⁺, Co²⁺, Ag⁺ cations. The polymeric fluorophore has been shown to be a selective chemosensor for Cu²⁺ cations. Copyright © 2006 John Wiley & Sons, Ltd.     

New green fluorescent polyvinylcarbazole copolymer with 1,8‐naphthalimide side chains as chemosensor for iron cations

The synthesis and basic photophysical characteristics of a novel green fluorescent polyvinylcarbazole polymer containing 4‐N,N‐dimethylaminoethyleneamino‐1,8‐naphthalimide side chains has been described. The ability to sense metal cations has been monitored by fluorescence emission spectroscopy. It is shown that the fluorescent intensity is very sensitive to the Fe²⁺ cations and the copolymer can be used as an homogeneous and heterogeneous fluorescent sensor for Fe²⁺ cations. Copyright © 2004 John Wiley & Sons, Ltd.     

Design and synthesis of a new fluorescent tripod for chemosensor applications

A new yellow-green fluorescent tripod based 1,8-naphthalimide has been synthesized and characterised. Its photophysical properties have been investigated in organic solvents of different polarity. The effect that the metal ions (Cd²⁺, Co²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Ni²⁺, Pb²⁺, Cu²⁺, Ba²⁺, Fe³⁺ and Ag⁺) produce upon the fluorescent intensity of acetonitrile solutions of the tripod has been discussed viewing its potential applications as a detector for metal cations. The influence of protons on the fluorescence intensity of the tripod in DMF and methanol–water (1:4 v/v) solutions has also been investigated.     

Metal cations for the determination of fluorescent phosphoinositides by capillary electrophoresis

Phosphatidylinositol (PI) and its phosphorylated derivatives known as phosphoinositides (PIPs), are essential regulators of cell signaling and membrane trafficking, cytoskeletal dynamics, and nuclear functions. Disruption of PI metabolism is associated with disorders such as immune dysfunction, cardiovascular disease, and cancer; therefore, there is currently great interest in studying PIPs and their metabolic enzymes. Here, we describe a method for the separation of fluorescent PI and its seven fluorescent phosphorylated derivatives by CE‐LIF. The CE method utilizes a Tris buffer and sodium deoxycholate in the presence of 30% 1‐propanol and 5% of a dynamic coating reagent, EOTrol^TM low reverse (EOTrol LR). It is simple, fast, highly sensitive, and it offers LODs in the order of 1.5 amol. The effect of cations such as lithium, sodium, potassium, cesium, barium, manganese, zinc, magnesium, calcium, spermine, and gentamicin were evaluated. Calcium and magnesium provided the best selectivity and resolution for the separation of the analytes while magnesium offered the best data reproducibility. The developed CE method would be useful in the studies of enzymatic activity in the PI and PIPs metabolic pathways using CE‐based in vitro and CE cell‐based assays, and/or for drug screening.     

Rapid capillary zone electrophoresis method for the determination of metal cations in beverages

A rapid and reliable capillary zone electrophoresis method for the determination of inorganic cations was developed. The complete separation of K⁺, Ba²⁺, Ca²⁺, Na⁺, Mg²⁺, Mn²⁺, Ni²⁺, Cd²⁺, Li⁺ and Cu²⁺ can be achieved in 4 min with a simple electrolyte composed by 10 mM imidazole as the carrier buffer and background absorbance provider and acetic acid as the complexing agent (pH 3.60). Injection was performed hydrostatically by elevating the sample at 10 cm for 30 s. The running voltage was +25 kV at room temperature. Indirect UV-absorption detection was achieved at 185 nm. The detection limit was in the range between 0.06 mg/l (Mg²⁺) and 0.57 mg/l (K⁺) and the quantification limits ranged from 0.10 mg/l (Ni²⁺) to 0.80 mg/l (Cu²⁺). The calibration graphs were linear in the concentration range from the quantification limit till at least 1 g/l in K⁺, 10 mg/l in Ba²⁺, Ca²⁺, Mg²⁺, Mn²⁺, Ni²⁺ and Cd²⁺, 40 mg/l in Na⁺ and 12 mg/l in Li⁺ and Cu²⁺. The repeatability, intraday and interday analysis were ≤1.55% and ≤3.64% for migration time and ≤3.38% and ≤3.63% for peak area. The method developed has been applied to several beverage samples with only a simple dilution and filtration treatment of the sample. The proposed method is simple, fast, cheap and it is achieved with common products in either laboratory. For these reasons, it is a very useful method for routine analysis.     

Synthesis and selectivity of sym-hydroxydibenzo-14crown-4 ionophores for protons,alkali metal cations,and alkaline earth cations in polymeric membranes

Six derivatives of sym-hydroxydibenzo-14-crown-4 have been prepared and incorporated into solvent-polymeric membranes. Responses of the membranes to protons, alkali metal cations, and alkaline earth cations have been determined. The preferred uptake of protons is attributed to proton complexation by stable crown ether alcohol and diol monohydrate species.     

Retention behavior of alkali, alkaline earth and transition metal cations in ion chromatography with an unmodified silica gel column

An unmodified silica gel (Develosil 30-5) column (150×4.6 mm I.D.) has been applied to the ion chromatographic separation of alkali, alkaline earth and transition metal cations. The retention behavior of the above cations on the bare substrate was investigated using a number of weak inorganic and organic acid eluents. During this investigation, several separations were achieved and the most suitable eluent conditions were identified. It was concluded that: (a) 1.5 mM HNO₃-0.5mM pyridine-2,6-dicar☐ylic acid eluent was the most effective for the simultaneous separation of common alkali and alkaline earth metal cations, (b) 1.5 mM oxalic acid eluent resulted in the best separation of alkali, alkaline earth, and transition metal cations, (c) 0.5 mM CuSO₄ eluent could be used for the separation of alkali metal cations alone and (d) 0.5 mM ethylenediamine-oxalic acid eluent at pH 5.5 resulted in themost efficient separation of both alkaline earth and transition metal cations.     

A novel fluorescent sensor for metal cations and protons based of bis-1,8-naphthalimide

A newly synthesized bis-1,8-naphthalimide aimed to increase its fluorescence intensity in the presence of protons or metal cations has been investigated. Its spectral photophysical characteristics in acetonitrile and chloroform solutions are described. The influence of metal cations (Zn(2+), Ni(2+), Ce(3+), Co(2+), Cu(2+) and Ag(+)) and protons on the fluorescence intensity has been investigate with regard to obtain fluorescence sensors for this ions in the environment.     

Molecularly imprinted polymers-based sensors for bisphenol-A: Recent developments and applications in environmental,food and biomedical analysis

Bisphenol A (BPA) is a well-known endocrine-disrupting industrial compound that is found throughout many aspects of our daily life; from the water we drink and the food we eat to the babies’ bottles and children’s plastic toys. Chronic exposure to BPA may result in some severe medical issues which account for the great importance of its monitoring and removal from everyday products. The use of molecularly imprinted polymers (MIPs) for that purpose has acquired a lot of traction in recent decades. MIPs are artificial antibodies with selective recognition cavities for specifically targeted substances. They are created using a variety of synthetic methods and employed in numerous types of sensors to be used in a wide range of applications. In this review, we focus on the different production methods of MIPs and the varied types of electrochemical and optical sensors that employed MIPs to detect and analyze BPA. Finally, the broad variety of applications of MIPs in environmental, foodstuff, and biological samples are thoroughly examined. Future expected trends and prospective developments are also assessed.     

Synthesis and characterization of ferrocenyl-acridine dyads and their multiresponse to proton and metal cations

Two new π-conjugated linked ferrocenyl-acridine dyads, (9-ethynylferrocenyl)acridine (3a) and (1-(ferrocenylethynyl)-4-ethynylbenzenyl)-acridine (3b), have been synthesized and investigated. UV-Vis spectroscopic and electrochemical studies reveal that 3a offers stronger electronic communication between terminal subunits than the extended system 3b, as shown by a stronger and lower-energy metal-to-ligand charge transfer (MLCT) transition and a more positive redox potential. Both of 3a and 3b show multiresponse to protons and selected metal ions (M = Zn²⁺, Pb²⁺, Hg²⁺, Fe³⁺, Cr³⁺), with a MLCT transition shift to the lower-energy, a redox potential shift to anode, and a luminescence increasing.     

Cucurbit[8]uril-improved recognition using a fluorescent sensor for different metal cations

ABSTRACT

Metal cations in aqueous solutions at different pHs (1.5, 4.5 and7.2) can be detected using the known inclusion complex H33258@Q8 as a fluorescent probe. Indeed, the fluorescence intensity of H33258 increases rapidly upon increasing the amount of Q[8] up to a Q[8]:H33258 ratio of 2:1, even at pH 1.5. The experimental results reveal that the probe not only exhibited selective recognition of metal cations at different pH but also showed different recognition for metal cations at different pHs. At pH 7.2, the probe responded to quite a variety metal cations, including one of the third main group elements, Al³⁺, four transition metal cations, Hg²⁺, Fe³⁺, Fe²⁺, and Cr³⁺ and three lanthanide cations Eu³⁺, Tm³⁺ and Yb³⁺; At pH 4.5, the probe responded to only two transition metal cations, Hg²⁺ and Fe³⁺. Unexpectedly, the probe lost its recognition properties at pH 1.5.     

Thermo and pH sensitive fluorescent polymer sensor for metal cations in aqueous solution

A new monomeric fluorophore N‐acryl‐N'‐(quinolin‐8‐yl)thiourea (AQT) was synthesized. Free radical copolymerization was carried out in order to prepare a water‐soluble fluorescent copolymer, based on N‐isopropylacrylamide. The fluorescent characteristic of the aqueous solutions of copolymers was investigated both in varied pH and in the presence of metal cations. The polymer‐ contained AQT was found to be a selective chemosensor for Ni, Pb, Co ions especially for Co ion. The obtained copolymers show thermo‐sensitive lower critical solution temperature (LCST) ranging from 32.5 to 37.5°C with varied ratios of AQT, N, N‐dimethylacrylamide and N‐isopropylamide. Copyright © 2007 John Wiley & Sons, Ltd.     

Developing a genetically encoded green fluorescent protein mutant for sensitive light-up fluorescent sensing and cellular imaging of Hg(II)

Hg(II) is well-known for quenching fluorescence in a distance dependent manner. Nevertheless, when we exposed the fluorophore of a green fluorescent protein (GFP) toward Hg(II), through H148C mutation, the GFP fluorescence could be “lighted up” by Hg(II) down to sub-nM level. The detection linear range is 0.5–3.0 nM for protein solutions at 8.0 nM. The GFPH148C protein displayed a promising selectivity toward Hg(II) and also the cellular imaging capacity. Spectra measurements suggested that the ground-state redistribution of protein contributed to the fluorescence enhancement, which was found not limited to Hg(II), and thus presented an opening for building a pool of GFP-based chemosensors toward other heavy metal ions.     

The effects of biologically important divalent and trivalent metal cations on the cyclization step of dopamine autoxidation reaction: A quantum chemical study

Dopamine is the most essential monoaminergic neurotransmitter involved in the pathophysiology of neurodegenerative disorders, and its autoxidation has been recognized as one of the potential trigger factors for dopaminergic neuron loss. The cyclization of dopamine o-quinone was shown to be the irreversible and rate-limiting step of the autoxidation reaction at physiologic pH values. Furthermore, various metal ions such as Al³⁺, Fe³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Mn²⁺ have been clinically associated with neurodegeneration, especially Parkinsonism and dementia. It has been proposed that these metal ions could increase the rate of the dopamine autoxidation reaction; however, the exact mechanism has not yet been fully understood. Using advanced quantum chemical calculations with the inclusion of solvent effects we showed that except for Mn²⁺, the studied metal cations could form complexes with dopamine o-quinone and significantly increase the dopamine o-quinone cyclization rate in aqueous solution; first, by enabling the cyclization to proceed spontaneously without the attack of the unprotonated amino group by hydroxide ion; second, by decreasing the intrinsic activation energy; and third, by decreasing the free energy of protonated amino group deprotonation. The latter also decreases the protective effect of acidic pH on dopamine autoxidation found in synaptic vesicles. The results are fully consistent with experimental data and provide deeper understanding of the effects of metal cations on the dopamine autoxidation reaction at physiologic pH values.     

Quantum mechanics/fluctuating charge calculations for absorption spectra of aqueous green fluorescent protein chromophore

We applied the quantum mechanics/fluctuating charges (QM/FQ) method to simulate the absorption spectra of three protonated forms of p-hydroxybenzylidene imidazolone (p-HBDI) in water. Configurations of solute-solvent were generated from molecular dynamics (MD) simulation within the context of a hybrid scheme in which solute and solvents were treated at QM and molecular mechanics, respectively. Nonperiodic spherical boundary condition was used. To examine the influence on simulated spectra coming from the geometrical relaxation of solute, the MD simulations were carried out for two cases: frozen and flexible molecular geometry of solute. As a result of our calculations, the simulations using the flexible solute's structure delivered vertical excitation energies closer to experimental data than those of a frozen solute, especially for the neutral case. For spectral broadening, changing from fixed geometry of solute to a flexible one led to a significant increase for both neutral and anionic forms of p-HBDI, but no effect happened for the cationic one.     

Separation of metal cations in acidic solution by capillary electrophoresis with direct and indirect UV detection

Methods for the detectionn of metal cations under acidic conditions, near PH 2, in capillary electrophoresis (CE) were investigatged. Conditions for direct UV detection of UV absorbing metal cations such as Cr³⁺, Cu²⁺, Fe³⁺, UO₂²⁺, VO²⁺, and VO²⁺ were established With aqueous HCl or HClO₄ as the electroyte carrier. The speciation of vanadium(IV) and vanadium(V) at PH 2.3 by CE was achieved with direct detection at 185 nm. With the strong absorbance at 185 nm, no complexation was needed to detect the metal cations. An indirect UV detrection scheme for acidic conditions was also investigated. Several background carrier electolytes (BCES) were studied including 4-methylbenzylamince, nicontinamide, pyridazine, guanidine, 3-picoline, and chromium (III) to determine their effectivencess under very acidic conditions. The efect of ioni c surfactants and the nonionic surfactant, Trition X-100, on the peak heights and N Values was also studied.     

基于1,8-萘酰亚胺与罗丹明B间荧光共振能量转移的高选择性Hg2+比率荧光探针

以罗丹明B与1,8-萘二甲酰亚胺反应合成了1个高选择性Hg²⁺比率荧光探针(RN). 在甲醇/乙腈/4-羟基哌嗪乙磺酸缓冲溶液(pH=7.2, 体积比8:1:1)中, RN对Hg²⁺具有比色和比率荧光双重响应. 加入Hg²⁺后, RN的紫外-可见光谱在约556 nm处产生强吸收, 溶液由浅绿色变为橙色, 其它金属离子对RN的紫外-可见光谱几乎无影响. 无Hg²⁺存在时, RN的荧光光谱在540 nm处出现萘二甲酰亚胺荧光团的特征峰; 加入Hg²⁺后, 540 nm处的发射带逐渐消失, 同时在580 nm附近产生强荧光, 荧光颜色从绿色变为橙色. 这归因于从萘酰亚胺到开环罗丹明B的荧光共振能量转移(FRET), 探针RN对Hg²⁺的比率荧光响应具有高选择性, 不受其它共存金属离子的干扰.     

Biquinolino-modified beta-cyclodextrin dimers and their metal complexes as efficient fluorescent sensors for the molecular recognition of steroids

A series of bridged beta-cyclodextrin (beta-CyD) dimers possessing functional tethers of various lengths was synthesized in moderate yield by the treatment of 2,2'-biquinoline- 4,4'-dicarboxylic dichloride with beta-CyD or mono[6-oligo(ethylenediamino)-6-deoxy]-beta-CyDs. The products were 2,2'-biquinoline-4,4'-dicarboxy-bridged bis(6-O-beta-CyD) (8), N,N'-bis(2-aminoethyl)-2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CyD) (9), and N,N'-bis(5-amino-3-azapentyl)-2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CyD) (10). The reaction of 8-10 with copper perchlorate give their copper(II) complexes 11-13 in satisfactory yields of over 77 %. All the bis(beta-CyD)s 8-13 act as efficient fluorescent sensors and display remarkable fluorescence enhancement upon addition of optically inert steroids. The inclusion complexation behaviors of 8-13 when treated with the representative steroids cholate (14), deoxycholate (15), and glycocholate (16) in aqueous solution at 25 degrees C were investigated by means of UV/Vis spectroscopy, conductivity and fluorescence measurements, circular dichroism spectroscopy, and 2D NMR spectroscopy. The tether length of bis(beta-CyD) 9 allows it to adopt a cooperative host-tether-guest binding mode in which the spacer and guest are co-included in the two CyD cavities. As a result of this cooperation, 9 has a stability constant (K(s)) about 2x10(2) times higher than that of monomodified beta-CyD 4 for inclusion complexation with cholate. Metallooligo(beta-CyD)s with four beta-CyD units have enhanced binding abilities compared with monomodified beta-CyDs. These metallo compounds have binding affinities for guest steroids that are up to 50-4.1x10(3) times higher than those of CyDs 2-4. The guest-induced fluorescence enhancement of bis(CyD)s opens a new channel for the design of sensor materials. The complex stability constants of these compounds are discussed from the viewpoint of induced-fit interaction and cooperative multiple binding between host and guest.