Fluorescent and magnetic dual-responsive coreshell imprinting microspheres strategy for recognition and detection of phycocyanin

Molecular imprinting as a versatile technology is emerging for diverse species in various fields; however protein imprinting faces several problems related to the size, structural complexity, conformational flexibility, and compatibility with solvents. Herein, by using phycocyanin as a model, with physiological significance and fluorescence characteristics, we developed a facile and highly efficient approach to obtain fluorescent and magnetic dual-responsive coreshell imprinting microspheres. Twostage miniemulsion polymerization was employed, based on surface immobilization of phycocyanin with aminolysis and aldehyde modification on superparamagnetic support particles. The dual-responsive imprinting microspheres exhibited high adsorption capacity of 10.53 mg g(-1), excellent binding selectivity toward phycocyanin with a high imprinting factor of 2.41, and good reproducibility with standard error within 10%. Furthermore, fast simple magnetic separation and sensitive fluorescent detection in a wide pH range was offered for phycocyanin, showing a good linearity within 0.01-1.0 mg L-1 (R-2 = 0.9970) and a favorable detectability up to 1.5 ng mL(-1). Consequently, the imprinting microspheres were successfully applied as sorbents for selective isolation of phycocyanin from protein mixtures and special imaging recognition. Taking advantages of dual-responsive polymers and surface imprinting, the developed strategy provides great application potentials for convenient, rapid targeting identification/enrichment and separation of proteins and thereby contributing to targeting drug delivery and protein research.Molecular imprinting as a versatile technology is emerging for diverse species in various fields; however protein imprinting faces several problems related to the size, structural complexity, conformational flexibility, and compatibility with solvents. Herein, by using phycocyanin as a model, with physiological significance and fluorescence characteristics, we developed a facile and highly efficient approach to obtain fluorescent and magnetic dual-responsive coreshell imprinting microspheres. Twostage miniemulsion polymerization was employed, based on surface immobilization of phycocyanin with aminolysis and aldehyde modification on superparamagnetic support particles. The dual-responsive imprinting microspheres exhibited high adsorption capacity of 10.53 mg g(-1), excellent binding selectivity toward phycocyanin with a high imprinting factor of 2.41, and good reproducibility with standard error within 10%. Furthermore, fast simple magnetic separation and sensitive fluorescent detection in a wide pH range was offered for phycocyanin, showing a good linearity within 0.01-1.0 mg L-1 (R-2 = 0.9970) and a favorable detectability up to 1.5 ng mL(-1). Consequently, the imprinting microspheres were successfully applied as sorbents for selective isolation of phycocyanin from protein mixtures and special imaging recognition. Taking advantages of dual-responsive polymers and surface imprinting, the developed strategy provides great application potentials for convenient, rapid targeting identification/enrichment and separation of proteins and thereby contributing to targeting drug delivery and protein research

A molecular imprinting-based turn-on Ratiometric fluorescence sensor for highly selective and sensitive detection of 2,4-dichlorophenoxyacetic acid (2,4-D)

A novel molecular imprinting-based turn-on ratiometric fluorescence sensor was constructed via a facile sol-gel polymerization for detection of 2,4-dichlorophenoxyacetic acid (2,4-D) on the basis of photo induced electron transfer (PET) by using nitrobenzoxadiazole (NBD) as detection signal source and quantum dots (QDs) as reference signal source. With the presence and increase of 2,4-D, the amine groups on the surface of QDs@SiO2 could bind with 2,4-D and thereby the NBD fluorescence intensities could be significantly enhanced since the PET process was inhibited, while the QDs maintained constant intensities. Accordingly, the ratio of the dual-emission intensities of green NBD and red QDs could be utilized for turn-on fluorescent detection of 2,4-D, along with continuous color changes from orange-red to green readily observed by the naked eye. The as-prepared fluorescence sensor obtained high sensitivity with a low detection limit of 0.14 mu M within 5 min, and distinguished recognition selectivity for 2,4-D over its analogs. Moreover, the sensor was successfully applied to determine 2,4-D in real water samples, and high recoveries at three spiking levels of 2,4-D ranged from 95.0% to 110.1% with precisions below 4.5%. The simple, rapid and reliable visual sensing strategy would not only provide potential applications for high selective ultratrace analysis of complicated matrices, but also greatly enrich the research connotations of molecularly imprinted sensors. (C) 2016 Elsevier B.V. All rights reserved

Colorimetric Detection of Mercury Species Based on Functionalized Gold Nanoparticles

The speciation analysis of heavy metal pollutants is very important because different species induce different toxicological effects. Nanomaterial-assisted optical sensors have achieved rapid developments, displaying wide applications to heavy metal ions but few to metal speciation analysis. In this work, a novel colorimetric nanosensor strategy for mercury speciation was proposed for the first time, based on the analyte-induced aggregation of gold nanoparticles (Au NPs) with the assistance of a thiol-containing ligand of diethyldithiocarbannate (DDTC). Upon the addition of mercury species, because Hg-DDTC was more stable than Cu-DDTC, a place-displacement between Hg species and Cu2+ would occur, and thereby the fiinctionalized Au NPs would aggregate, resulting in a color change. Moreover, by virtue of the masking effect of ethylenediaminetetraacetic acid (EDTA), the nanosensor could readily discriminate organic mercury and inorganic mercury (Hg2+), and it is thus anticipated to shed some light on the colorimetric sensing of organic mercury. So, a direct, simple colorimetric assay for selective determination of Hg species was obtained, presenting high detectability, such as up to 10 nM for Hg2+ and IS nM for methylmercury. Meanwhile, the strategy offered excellent selectivity toward mercury species against other metal ions. The simple, rapid, and sensitive label-free colorimetric sensor for the determination of Hg species provided an attractive alternative to conventional methods, which usually involve sophisticated instruments, complicated processes, and long periods of time. More importantly, by using mercury as a model, an excellent nanomaterial-based optical sensing platform can be developed for speciation analysis of trace heavy metals, which can lead to nanomaterials stability change through smart functionalization and reasonable interactions.The speciation analysis of heavy metal pollutants is very important because different species induce different toxicological effects. Nanomaterial-assisted optical sensors have achieved rapid developments, displaying wide applications to heavy metal ions but few to metal speciation analysis. In this work, a novel colorimetric nanosensor strategy for mercury speciation was proposed for the first time, based on the analyte-induced aggregation of gold nanoparticles (Au NPs) with the assistance of a thiol-containing ligand of diethyldithiocarbannate (DDTC). Upon the addition of mercury species, because Hg-DDTC was more stable than Cu-DDTC, a place-displacement between Hg species and Cu2+ would occur, and thereby the fiinctionalized Au NPs would aggregate, resulting in a color change. Moreover, by virtue of the masking effect of ethylenediaminetetraacetic acid (EDTA), the nanosensor could readily discriminate organic mercury and inorganic mercury (Hg2+), and it is thus anticipated to shed some light on the colorimetric sensing of organic mercury. So, a direct, simple colorimetric assay for selective determination of Hg species was obtained, presenting high detectability, such as up to 10 nM for Hg2+ and IS nM for methylmercury. Meanwhile, the strategy offered excellent selectivity toward mercury species against other metal ions. The simple, rapid, and sensitive label-free colorimetric sensor for the determination of Hg species provided an attractive alternative to conventional methods, which usually involve sophisticated instruments, complicated processes, and long periods of time. More importantly, by using mercury as a model, an excellent nanomaterial-based optical sensing platform can be developed for speciation analysis of trace heavy metals, which can lead to nanomaterials stability change through smart functionalization and reasonable interactions

Naked-eye sensitive ELISA-like assay based on gold-enhanced peroxidase-like immunogold activity

A naked-eye sensitive ELISA-like assay was developed based on gold-enhanced peroxidase-like activity of gold nanoparticles (AuNPs). Using human IgG (H-IgG) as an analytical model, goat anti-human IgG antibody (anti-IgG) adsorbed on microtiter plate and AuNPs-labeled anti-IgG acted as capture antibody and detection antibody, respectively. Because the surfaces of AuNPs were blocked by protein molecules, the peroxidase-like activity of AuNPs was almost inhibited, evaluated by the catalytic oxidation of peroxidase enzyme substrate 3,3',5,5'-tetramethylbenzidine (TMB), which could produce a bright blue color in the presence of H2O2. Fortunately, the catalytic ability of AuNPs was dramatically increased by the deposition of gold due to the formation of a new gold shell on immunogold. Under optimal reaction conditions, the colorimetric immunoassay presented a good linear relationship in the range of 0.7-100 ng/mL and the limit of detection (LOD) of 0.3 ng/mL calculated by 3 sigma/S for UV-vis detection, and obtained LOD of 5 ng/mL for naked-eye detection. The obtained results were competitive with conventional sandwich ELISA with the LOD of 1.6 ng/mL. Furthermore, this developed colorimetric immunoassay was successfully applied to diluted human serum and fetal bovine serum samples, and predicted a broad prospect for the use of peroxidase-like activity involving nanomaterials in bioassay and diagnostics

A sensitive fluorescent biosensor for the detection of copper ion inspired by biological recognition element pyoverdine

The environmental copper pollution seriously threatens the health of organisms and the safety of ecosystem. Therefore, the development of a simple and sensitive method to detect copper ion is very important. In this study, we have developed a fluorescent biosensor based on biological recognition element pyoverdine to selectively detect copper ion. The fluorescence of pyoverdine is quenched obviously after binding with copper ion. A good linearity within the range of 0.2-10 mu M (R= 0.997) is attained and the detection limit is 50 nM. The biosensor has been successfully utilized for the detection of copper ion in drinking water, seawater and bio-samples and the results agree well with those obtained by the inductively coupled plasma mass spectrometry. Therefore, the established biosensor is a creditable method to detect copper ion with high sensitivity and selectivity, which can be utilized as a powerful tool to monitor copper pollution in the environment. (C) 2016 Elsevier B.V. All rights reserved

Current status and challenges of ion imprinting

Ion imprinting technology (IIT) aims to recognize ions while retaining the unique virtues of molecular imprinting technology (MIT), namely structure predictability, recognition specificity and application universality. Owing to special coordination or electrostatic interactions, ion imprinted polymers (IIPs) are generally compatible with aqueous media and have advantages over most molecularly imprinted polymers (MIPs). IIPs can achieve effective identification of water-soluble ions, especially heavy metals and radioactive elements that cause increasing concerns. The purpose of this review is to summarize recent advances of ion imprinting, focusing on the current status and challenges in fundamentals and applications that involve almost all types of ions and ion-related molecular imprinting. In addition, various smart strategies are highlighted, such as surface imprinting, stimuli-responsive imprinting, dual/multiple components imprinting, click chemistry, and microwave-assisted heating. In this review, the elemental periodic table is first utilized as a template to introduce ion classification standards for various IIPs, including main groups, transition elements, actinides, rare earths, metalloids, anion imprinting and secondary imprinting. Finally, the challenges and possible solution strategies plus future trends are also proposed (302 references)

Quantification of cysteine hydropersulfide with a ratiometric near-infrared fluorescent probe based on selenium-sulfur exchange reaction

Cysteine hydropersulfide (Cys-SSH) plays primary roles in the synthesis of sulfur-containing cofactors, regulation of cellular signaling, activation or inactivation of enzyme activities, and modulation of cellular redox milieu. However, its biofunctions need to be further addressed due to the fact that many issues remain to be clarified. Herein, we conceive a novel ratiometric near-infrared fluorescent probe Cy-Dise for the sensitive and selective detection of Cys-SSH in living cells and in vivo for the first time. Cy-Dise is composed of three moieties: bis(2-hydroxyethyl) diselenide, heptamethine cyanine, and D-galactose. Cy-Dise exhibits a satisfactory linear ratio response to Cys-SSH via a selenium-sulfur exchange reaction in the range of 0-12 mu M Cys-SSH. The experimental detection limit is determined to be 0.12 mu M. The results of ratio imaging analyses confirm the qualitative and quantitative detection capabilities of Cy-Dise in HepG2 cells, HL-7702 cells, and primary hepatocytes. The level changes of Cys-SSH in cells stimulated by some related reagents are also observed. The probe is also suitable for deep tissue ratio imaging. Organ targeting tests with Cy-Dise in normal Spraque-Dawley (SD) rats and Walker-256 tumor SD rats verify its predominant localization in the liver. The probe is promising for revealing the roles of Cys-SSH in physiological and pathological processes

Highly sensitive fluorescence detection of copper ion based on its catalytic oxidation to cysteine indicated by fluorescein isothiocyanate functionalized gold nanoparticles

An innovative fluorescence method for sensitive detection of copper ion (Cu2+) was developed based on fluorescein isothiocyanate functionalized gold nanoparticles (FITC-AuNPs). Due to the stronger binding affinity of isothiocyanate functional group to gold, FITC molecules could adsorb on the surface of AuNPs, forming a simple fluorescence resonance energy transfer (FRET) system, and the fluorescence intensity of FITC was remarkably quenched. Upon adding cysteine, FITC could be displaced from the surface of AuNPs because the formation constant (K-f) of Au-S linkage (K-f(AuS-) = 4 x 10(35)) was much higher than AuSCN linkage (K-f(Au(SCN)(2-)) = 10(23)), leading to the recovery of fluorescence intensity. However, Cu2+ could catalyze O-2 oxidation of cysteine, and the generated disulfide cystine could not remove FITC from AuNPs' surface. Therefore, the recovery of fluorescence intensity was much weaker when compared with that of in the absence of Cu2+. And on the basis of this principle the concentration of Cu2+ could be detected quantitatively. Under optimal conditions, our method exhibited high selectivity toward Cu2+ and provided a good linear relationship in the range of 1.0-17.0 nM with the detection limit of 0.37 nM calculated by 3 sigma/S. Furthermore, complicated synthetic procedures and poor water solubility could be ignored in this proposed fluorescent sensor. (C) 2015 Elsevier B. V. All rights reserved.An innovative fluorescence method for sensitive detection of copper ion (Cu2+) was developed based on fluorescein isothiocyanate functionalized gold nanoparticles (FITC-AuNPs). Due to the stronger binding affinity of isothiocyanate functional group to gold, FITC molecules could adsorb on the surface of AuNPs, forming a simple fluorescence resonance energy transfer (FRET) system, and the fluorescence intensity of FITC was remarkably quenched. Upon adding cysteine, FITC could be displaced from the surface of AuNPs because the formation constant (K-f) of Au-S linkage (K-f(AuS-) = 4 x 10(35)) was much higher than AuSCN linkage (K-f(Au(SCN)(2-)) = 10(23)), leading to the recovery of fluorescence intensity. However, Cu2+ could catalyze O-2 oxidation of cysteine, and the generated disulfide cystine could not remove FITC from AuNPs' surface. Therefore, the recovery of fluorescence intensity was much weaker when compared with that of in the absence of Cu2+. And on the basis of this principle the concentration of Cu2+ could be detected quantitatively. Under optimal conditions, our method exhibited high selectivity toward Cu2+ and provided a good linear relationship in the range of 1.0-17.0 nM with the detection limit of 0.37 nM calculated by 3 sigma/S. Furthermore, complicated synthetic procedures and poor water solubility could be ignored in this proposed fluorescent sensor. (C) 2015 Elsevier B. V. All rights reserved

Graphene oxide-based microspheres for the dispersive solid-phase extraction of non-steroidal estrogens from water samples

A modified Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method based on the dispersive solid-phase extraction (dSPE) combined with high performance liquid chromatography (HPLC) was developed for the determination of non-steroidal estrogens in water samples. In this study, graphene oxide-based silica microspheres (SiO2@GO) were used as dSPE material for the preconcentration of analytes. HPLC was used for the separation and detection. This was the first time that the synthesized SiO2@GO microspheres were used as stationary phases for the off-line preconcentration of the non-steroidal estrogens in dSPE. dSPE parameters, such as sample pH, volume and type of eluent were optimized. Application of the developed method to analyze spiked lake, reservoir and tap water samples resulted in good recoveries values ranging from 70 to 106% with relative standard deviation values lower than 7.0% in all cases. Limits of detection were in the range of 0.2-6.1 mu g/L. The combined data obtained in this study recommended that the proposed method is very fast, simple, repeatable and accurate for the detection of non-steroidal estrogens. Furthermore, the SiO2@GO microspheres application could potentially be expanded to extract and pre-concentrate other compounds in various matrices. (C) 2014 Elsevier B.V. All rights reserved.A modified Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method based on the dispersive solid-phase extraction (dSPE) combined with high performance liquid chromatography (HPLC) was developed for the determination of non-steroidal estrogens in water samples. In this study, graphene oxide-based silica microspheres (SiO2@GO) were used as dSPE material for the preconcentration of analytes. HPLC was used for the separation and detection. This was the first time that the synthesized SiO2@GO microspheres were used as stationary phases for the off-line preconcentration of the non-steroidal estrogens in dSPE. dSPE parameters, such as sample pH, volume and type of eluent were optimized. Application of the developed method to analyze spiked lake, reservoir and tap water samples resulted in good recoveries values ranging from 70 to 106% with relative standard deviation values lower than 7.0% in all cases. Limits of detection were in the range of 0.2-6.1 mu g/L. The combined data obtained in this study recommended that the proposed method is very fast, simple, repeatable and accurate for the detection of non-steroidal estrogens. Furthermore, the SiO2@GO microspheres application could potentially be expanded to extract and pre-concentrate other compounds in various matrices. (C) 2014 Elsevier B.V. All rights reserved

Cyanine-based colorimetric and fluorescent probe for the selective detection of diethylstilbestrol in seawater, shrimp and fish samples

The synthetic estrogen drug diethylstilbestrol (DES) plays important roles in the treatment of estrogen deficiency disorders for human beings. The excessive intakes of DES can lead to physiological dysfunction and raise the risk of ovarian cancer, breast cancer and other diseases. However, it is still abused for improving the fat deposition or sex reversal procedure in aquatic economic creatures for pursuit of huge interests. DES can exist in aquatic products or polluted aquacultural seawater, which seriously threatens human health. Therefore, it is desirable to establish simple and sensitive methods for the detection of DES. In this work, we have developed a new colorimetric and fluorescent probe Cy-DES for the detection of DES with high sensitivity and selectivity. As a near-infrared probe, Cy-DES is able to avoid autofluorescence of dissolved organic compounds and maximize signal-to-background contrast. Taking advantage of the strong electrostatic interaction between the probe Cy-DES and DES, the spectroscopic properties of probe Cy-DES can be obviously changed in presence of DES. Under testing conditions, there is an excellent linearity within the range of 1-8 mu M (r = 0.9997) and the detection limit is 0.2 mu M. The probe Cy-DES is successfully applied for the detection of DES in spiked seawater, shrimp and fish samples. Additionally, the detection of DES can be directly achieved by naked eyes with the utilizing of probe Cy-DES. The developed method is of great potential for application in the on-site detection of DES. (C) 2015 Elsevier B.V. All rights reserved