Structural effect of fluorophore on phenylboronic acid fluorophore/cyclodextrin complex for selective glucose recognition

Based on the design of the fluorescent site of a fluorescent probe, we have created a unique system that changes its twisting response to sugar. Two probes were synthesized, in which phenylboronic acid and two kinds of aromatic fluorescent site (pyrene or anthracene) were conjugated by an amide bond. In the fluorescence measurement of pyrene-type probe 1, dimer fluorescence was observed at high pH. In induced circular dichroism (ICD) experiments, a response was observed only in the presence of glucose and γ-cyclodextrin, and no response was seen with fructose. On the other hand, in the fluorescence measurement of anthracene-type probe 2, dimer fluorescence was observed in the presence of both glucose and galactose, and the fluorescence was different from the case of fructose. When the ICD spectra of these inclusion complexes were measured, an inversion of the Cotton effect, which indicates a change in the twisted structure, was observed in galactose and glucose. These differences in response to monosaccharides may originate in the interaction between the fluorescent site and the cyclodextrin cavity.     

Opal photonic crystal double-network hydrogel for visual detection through structural color and fluorescent responsiveness

Photonic crystal hydrogels are widely used in the field of visual detection, based on the response of the structural color to external stimulus, such as pH, temperature, near-infrared light, and so on. Here, we develop an opal photonic crystal hydrogel by combining polystyrene (PS) photonic crystals with a fluorescent double-network hydrogel and focus on both its visual detection function and mechanical property. The opal hydrogel is composed of nanocomposite hydrogel as the first network and ionic crosslinked hydrogel as the second network. The introduction of PS photonic crystals and terbium ions endows the opal hydrogel distinctive structural colors and fluorescence, respectively. Because of volume changes, the structural color of the opal hydrogel selectively responses to metal ions and organic solvents. Attributing to the ion exchange interaction, the opal hydrogel exhibits fluorescent responses to various metal ions. Combining the responsiveness of structural color and fluorescence, a visual dual-detection mode is set up, with better detection sensitivity and selectivity. Moreover, the characteristics of nanocomposite and double-network crosslinking ensure the opal hydrogel enough mechanical properties to undergo cycle visual detection. Consequently, the fabricated opal hydrogel is promising for use in visual detection to multiple substances in single- or dual-detection mode.     

Fluorescence analysis for thermo-sensitive hydrogel microspheres

Poly(N-isopropylacrylamide) (PNIPAM) hydrogel microspheres were prepared by precipitation polymerization above the polymer's lower critical solution temperature (LCST) in water. The hydrodynamic size of PNIPAM microspheres exhibited a thermo-sensitive change around the LCST. In order to obtain information about the interface of the hydrogels, contact angle measurement, protein adsorption, and fluorescence analysis were performed. Contact angle measurement and protein adsorption showed a gradual change around the LCST similar to the change of the hydrodynamic size. However, fluorescence study exhibited a sharp change at the LCST. In addition, a quenching experiment was employed to elucidate the location of the fluorescent probes. In the PNIPAM latex, the probes were located where they were less quenchable as compared to the PNIPAM solution. It seems probable that the probes can penetrate into the crosslinked PNIPAM hydrogel and might reflect the inner environment of the hydrogel. The effect of salt on thermo-sensitive behaviour was also detected by fluorescence analysis. On the other hand, the hydrogel microsphere prepared from poly(acryloyl pyrrolidine) (PAPr) showed a gradual change in fluorescence with temperature.     

Optical characteristics of responsive biopolymers; co-polycondensation of tri-functional amino acids and Cy-3 bis-amine with diacylchlorides

The synthesis and fluorescence behaviour of a range of amphiphilic poly(l-lysine co-bis-amine-Cy-3 iso-phthalamide) polymers that incorporate low levels of Cy-3 dye co-monomer (0.5-2.1% (w/w)) in their backbone have been investigated in aqueous solution over a range of pH values. The desired functionality of these biocompatible, hydrophobically modified polyelectrolytes was achieved by incorporating pendant hydrophilic carboxyl groups along the polymer backbone, via the l-lysine moiety, balanced by a degree of hydrophobicity introduced via the iso-phthaloyl moiety. Thus, the polymer changes from an extended conformation at high degrees of ionisation to a compact conformation stabilised by hydrophobic association at low degrees of ionisation and eventually precipitates from solution. At intermediate degrees of ionisation, such polymers exhibit amphiphilic properties. A bis-functional cyanine fluorophore derivative, co-polymerised within the polymer backbone, is demonstrated to act as a fluorescent reporter on the conformational state of the polymer. The materials have higher intrinsic fluorescence intensity per fluorophore monomer over a broad range of concentrations than bis-amine Cy-3 and their maximum fluorescence intensity is up to eight fold higher than the maximum intensity of bis-amine Cy-3, which is limited by quenching. It is also shown that the free fluorophore can be used to probe the conformation of unlabelled poly(l-lysine iso-phthalamide) through electrostatic interaction with the polymer. The technique allows rapid spectrophotometric determination of polymer conformation and offers the potential of an environmentally sensitive molecular pH probe for in vivo use.     

Synthesis and photophysical properties of a blue water-soluble fluorescent polymer for Ni2+ and proton sensing

A monomer 7-hydroxy-4-methyl-8-(4′-allyloxypiperazin-1′-yl) methylcoumarin with blue fluorescence was synthesized. The present investigation dealt with the synthesis and characterization of a coumarin monomer, containing a piperazine group. Then it was copolymerized with N-vinylpyrrolidone to obtain a water-soluble fluorescent copolymer (poly(Al-HMPC-co-VP)). The fluorescence characteristics of the polymer as a function of pH sensor were investigated in aqueous solution. It was found that the polymer displayed sensitive fluorescence signal amplification over a wide pH scale, which was ascribed to a photoinduced electron transfer from the piperazine receptor to the coumarin fluorophore. In addition, the influence of metal cations on the fluorescence intensity of poly(Al-HMPC-co-VP) were also studied. Obvious fluorescence enhancement was due to the photophysical response of the polymer to the presence of Ni²⁺ ion. The results suggest that copolymer may offer potential application as a reusable polymer for sensor protons and Ni²⁺ ion in aqueous solution.     

Poly(vinyl alcohol)–Carbon Nanodots Fluorescent Hydrogel with Superior Mechanical Properties and Sensitive to Detection of Iron(III) Ions

A high‐strength fluorescent hydrogel is prepared by physical cross‐linking of carbon nanodots (CNDs) with poly(vinyl alcohol) (PVA). The stretching and compression of the PVA hydrogel are improved with CNDs by 176% and 64%, respectively. It still has excellent self‐healing behaviors without adding other healing agents. In addition, the search for rapid detection of heavy metals is still a huge challenge. The resulting hydrogel exhibits fluorescence quenching in the presence of Fe³⁺ by the fluorescence characteristics of CNDs, which has high selectivity and sensitivity. The PVA‐CNDs fluorescent hydrogel can be used as a solid detection platform for Fe³⁺, where the detection limit is found to be 10 µm for Fe³⁺ by fluorescence studies.     

磺化β-环糊精/PVA凝胶电刺激响应行为的研究

首先将β-环糊精(β-CD)和聚乙烯醇(PVA)用戊二醛交联制成凝胶;然后以浓硫酸作为改性剂,将磺酸根引入凝胶中,制备出一种阴离子型磺化β-CD/PVA凝胶,并对该凝胶的平衡溶胀率、粘接性能和电刺激响应行为等进行了研究。结果表明:该凝胶在Na2SO4水溶液中的平衡溶胀率随离子强度增加而减小;其剪切强度随PVA含量增加呈先升后降态势,并且在w(PVA)=5%时相对最大(3.8 MPa)。在非接触性直流电场作用下,该凝胶在Na2SO4水溶液中弯向电场负极,其弯曲偏转速率和应变随外加电压增加而增大,并且在离子强度为0.15 mol/L时相对最大;在循环电场作用下,该凝胶的电刺激响应行为具有良好的重现性和可逆性。     

A novel coumarin‐based fluorescent probe for selective detection of cysteine over homocysteine

A coumarin‐based fluorescent probe containing both acrylate moiety and an allyl substituent was developed for distinguishing cysteine from homocysteine. The maximum absorption wavelength of the probe showed a bathochromic shift upon addition of cysteine and the colour changed from colourless to yellow. The maximum fluorescence emission at 462 nm of the probe was dramatically enhanced upon addition of cysteine in aqueous solution. In HEPES buffer (pH = 7.4, EtOH/H₂O = 9:1, v/v), both of the fluorescence emission bands of the probe at ca. 390 and 462 nm were intensely enhanced upon the addition of cysteine, while other amino acids, namely, homocysteine, asparaginic acid, methionine, glycine, phenylalaninase, valine, tryptophan, serine, glutamic acid and glutathione, did not cause a remarkable change. The probe can be used for selectively colorimetric and ratiometric fluorescent detection of cysteine over homocysteine and other common amino acids in both organic media and aqueous solution. The concentration of cysteine can be estimated by titration of the probe in aqueous solution, and the detection limit of the probe towards cysteine was 2 μmol/L.     

快速响应聚(N-异丙基丙烯酰胺)水凝胶的制备及性能

以N-异丙基丙烯酰胺为单体、N,N′-亚甲基双丙烯酰胺为交联剂、过硫酸铵为引发剂、N,N,N,′N′-四甲基乙二胺为加速剂,在不同浓度的羧甲基纤维素的水溶液中,在低温下聚合/交联制备了一系列快速响应的温度敏感性聚(N-异丙基丙烯酰胺)水凝胶。用SEM观察了其表面形态,测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学。结果表明,与传统水凝胶相比,该水凝胶的溶胀性能有所提高,并且对温度的变化具有较快的响应速率。以质量分数为0.75%的羧甲基纤维素水溶液中制备的水凝胶为例,该水凝胶在20℃时的溶胀比为21.4,而传统水凝胶在相同温度时的溶胀比仅为12.9;该水凝胶在1 m in内失去60%的水,在4 m in内失去约80%的水,而传统水凝胶在15 m in内仅失去66%左右的水。     

可连续识别Cu2+和PPi的荧光探针的合成及性能研究

连续识别型荧光探针能在同一测试条件下连续识别两种离子,使得离子的检测更具专一性,是在普通同类型探针检测功能方面的拓展。设计合成了以7-二乙氨基香豆素为母体、咪唑-2-甲醛为识别基团的一种高选择性的席夫碱型荧光探针CI,用于连续识别Cu²⁺和焦磷酸根离子(PPi)。探针CI对Cu²⁺表现出了明显的“开-关”荧光淬灭响应,淬灭率为100%,而形成的配合物CI-Cu²⁺对PPi呈现明显的“关-开”荧光增强响应。探针CI对Cu²⁺和PPi的检出限均为0.14μmol/L,其与Cu²⁺的配位比为1∶1,而CI-Cu²⁺配合物与PPi以2∶1配位。在pH 5~11的范围内,探针CI和CI-Cu²⁺具有很好的识别能力。     

苯甲醛修饰的聚酰胺胺树状大分子的合成与荧光性能研究

以乙二胺为中心核,丙烯酸甲酯为支化单体,苯甲醛为端基官能团合成了3.0代和4.0代两种聚酰胺胺-苯甲醛树状大分子。对其荧光性能进行了研究,结果表明,溶液中的Fe3+对不同代数聚酰胺胺-苯甲醛树状大分子的荧光具有淬灭效应,并且荧光发射峰出现了红移现象。溶液中的Zn2+对聚酰胺胺-苯甲醛树状大分子的荧光具有增强作用,但是当Zn2+与树状大分子摩尔比持续增加时,其混合溶液的荧光强度却减小。     

Al~(3+)荧光探针的合成及识别性能研究

以2-羟基-1-萘甲醛和邻苯二胺为原料,通过席夫碱反应合成了一个Al~(3+)荧光探针。采用紫外-可见和荧光光谱法研究了探针在乙腈溶液中对金属离子的识别能力。实验结果表明,该探针在乙腈及其水溶液中可以有效、快速地检测Al~(3+)。通过荧光滴定曲线、Job's曲线和Benesi-Hildebrand曲线,得出探针分子与Al~(3+)的配合比和配合常数分别为2∶1和2.65×10~5,并测得Al~(3+)的最低检出限为1.85×10~(-8)mol/L。     

葡萄糖修饰罗丹明B的荧光探针的合成及其性质研究

设计合成一种用于pH测定的荧光探针,以罗丹明B、1-O-丙炔基-2,3,4,6-四-O-乙酰基-β-D-葡萄糖苷等为原料,利用Click反应,合成葡萄糖修饰罗丹明B荧光探针,并利用核磁共振波谱对其结构进行表征。进一步研究了该探针的荧光性质,并利用MTT法评价了所制备荧光探针的细胞毒性。实验结果表明,弱酸性条件下,在578 nm处有强荧光发射峰。在pH 4.0~6.5范围内,荧光强度与pH呈线性关系,并具有良好的可逆性。细胞毒性试验中,当浓度≥40μmol/L时,细胞的生存能力开始降低,通过拟合计算半抑制浓度IC50为36.56μmol/L。所合成的荧光探针有望用于细胞微环境的pH检测。     

A new thermosensitive fluorescent probe for diol sensing: Poly(N-isopropylacrylamide-co-vinylphenylboronic acid)-alizarin red S complex

The reversible complex formation between newly synthesized temperature sensitive copolymer, N-isopropylacrylamide-co-4-vinylphenylboronic acid and diol carrying molecules was first investigated by fluorescence spectroscopy. This investigation resulted in a development of a temperature sensitive-fluorescent probe used for quantitative determination of diol carrying molecules. In the first stage of competitive assay developed in this study, the receptor (i.e. boronic acid groups of temperature sensitive copolymer) and the reporter (a catechol dye, alizarin red S) associated at the selected pH and temperature to give a fluorescent cyclic boronate ester. The stimuli–responsive character of copolymer allowed to control the formation of fluorescent complex by adjusting the temperature. The maximum intensity was observed at 660 nm in the emission spectrum of the cyclic boronate ester. The fluorescent receptor–reporter complex (i.e. cyclic borate ester formed from boronic acid and ARS) was then partly dissociated in the presence of diol carrying guest due to the formation of another non-fluorescent complex between copolymer and guest. Various agents from different material groups, fructose, ascorbic acid, β-nicotinamide adenine dinucleotide (β-NAD) and horse radish peroxidase (HRP) were used as target diol carrying agents. The decrease in fluorescent intensity due to the dissolution of the receptor–reporter complex is proportional to the concentration of target diol carrying agent.     

Effect of chemical composition on the response of zwitterionic glucose sensitive hydrogels studied by design of experiments

A stimuli‐responsive hydrogel that contains the anionic monomer 3‐acrylamidophenylboronic acid and the cationic monomer N‐[3‐(dimethylamino)propyl]acrylamide binds with cis‐diol groups of glucose molecules selectively and reversibly. Even though such hydrogels have good selectivity for glucose, there are still remaining thresholds that should be overcome to enhance the sensitivity (swelling pressure response magnitude) and to reduce the response time (inverse of 1st order rate constant). In this study, the sensitivity and response time of zwitterionic glucose sensitive hydrogels (GSHs) were studied with three factor DOE analysis. The DOE results show that the molar ratio of 3‐acrylamidophenylboronic acid/N‐[3‐(dimethylamino)propyl]acrylamide and the wt % of monomer in the pregel solution are the most important factors for enhancing the hydrogel sensitivity. In addition, fast response times can best be achieved by decreasing the molar ratio of cross‐linker. The results of this study will be useful as guidelines for the optimal synthesis of glucose sensitive hydrogels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40667.     

带β-环糊精侧基水凝胶的制备与性能研究

用顺丁烯二酸酐（MAH）对β-环糊精（β-CD）进行化学改性制备丁烯二酸单酯化β-环糊精单体（MAH-β-CD）。用氧化还原自由基引发单体MAH-β-CD、丙烯酰胺（AM）以及丙烯磺酸钠（SAS）共聚,合成水凝胶,用红外光谱对产物结构表征。溶胀研究结果表明该水凝胶具有良好的温度、pH敏感性。     

Equilibrium swelling properties of weakly lonizable 2-hydroxyethyl methacrylate (HEMA)-based hydrogels

Hydrogles, sensitive to pH, were prepared by copolymerizing 2-hydroxyethyl methacrylate (HEMA) with 2-dimethylaminoethyl methacrylate (DMA). The mole fraction of the DMA monomer present during synthesis was fixed at 0.3, while the volume fraction of total monomer varied from 0.29 ( I ) to 1.0 ( II ). Swelling equilibria were measured in citrate of phosphate buffer for pH from 3.0 to 7.6 Swelling of the hydrogels depends on the volume fraction monomer present during synthesis, solution, pH, and identity of the buffer, Hydrogel I reached a four-fold larger swelling ratio (g swollen hydrogel/g dry hydrogel) in pH 3.0 citrate buffer, as compared to hydrogel II . Experimental results are interpreted on the basis of ideal Donnan equilibria. © 1994 John Wiley & Sons, Inc.     

Facile preparation and potential application of water‐soluble polymeric temperature/pH probes bearing fluorescein

An unsaturated monomer bearing xanthene groups and allyloxyfluorescein (Al‐Flu), was synthesized from fluorescein and allyl bromide by etherification. The structure of the monomer was confirmed by IR and mass spectroscopy and ¹H‐NMR, and ¹³C‐NMR spectroscopy. With azobisisobutyronitrile as a thermal initiator in tetrahydrofuran under 65–70°C, a copolymer of allyloxyfluorescein and acrylamide [poly(Al‐Flu‐co‐AM)] was obtained and was characterized by the methods of IR spectroscopy, ultraviolet–visible spectroscopy, and differential scanning calorimetry. The experimental results show that the fluorescence spectra of water‐soluble poly(Al‐Flu‐co‐AM) was dependent on the pH and temperature in the solution. Moreover, poly(Al‐Flu‐co‐AM) had an excellent linear response between the relative fluorescence intensity and temperature in the range 0–60°C and had a nonlinear response from pH 0.00 to 12.85 between the relative fluorescence intensity and pH. The pH and temperature sensitivities of the fluorescence could be advantageous for it as a multifunctional material to probe pH and temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

A fluorescent probe for the dual detection of mercury ions and thiols based on a simple coumarin derivative

A fluorescent probe based on a simple coumarin derivative could recognise mercury ions (Hg(ii )) and thiols selectively in aqueous solution. The addition of Hg(ii ) induced a blue shift of the fluorescence emission band of the probe while the fluorescence was almost quenched by the addition of p‐toluenethiol or cysteine (Cys). The detection limit of the probe towards Hg(ii ) and Cys was 8 µmol/L. The probe could be used for the detection of Hg(ii ) and thiols by the naked eye under ultraviolet light irradiation.     

Novel fluorescence method for cure monitoring of hydrosilation‐curable silicones

This study aimed to evaluate a reactive fluorescent probe, 9,10‐bis‐(phenylethynyl) anthracene (BPEA), for cure monitoring of hydrosilation‐curable silicones. The hydrosilation‐curable silicones consisted of a vinyl‐terminated polydimethylsiloxane prepolymer, a methylhydrosiloxane‐dimethylsiloxane copolymer, and an inhibitor, 1,3‐divinyltetramethyldisiloxane. The hydrosilation reaction was catalyzed with the solution of a platinum catalyst in the prepolymer. The catalyst solution also contained a trace amount of the reactive fluorescent probe. Three hydrosilation‐curable silicones, with the prepolymer of varying molar mass, were investigated. Each of the hydrosilation‐curable silicones was mixed with the catalyst solution at the mass ratio of 1 : 1 to initiate the cure. During the cure of each mixture at 22°C, the elastic modulus of the mixture and the fluorescence spectrum of the probe at the excitation wavelength of 360 nm were measured. Initially, the elastic modulus changed slowly, but then increased rapidly as a result of the increase in molar mass. The elastic modulus leveled off and reached a plateau value at the setting time. The ratio of the fluorescence intensities at 422 and 466 nm increased steadily, and then leveled off and reached a plateau value at the setting time, in agreement with the setting time determined from the change in elastic modulus. The reactive fluorescent probe, BPEA, can therefore be used for nondestructive fluorescence monitoring of hydrosilation‐curable silicones. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009