Research article Received: 13 February 2014,
Revised: 26 April 2014,
Accepted: 22 May 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2727
Modified Eu-doped Y2O3 nanoparticles as turnoff luminescent probes for the sensitive detection of pyridoxine Eshagh Zobeiri,a Abdolmajid Bayandori Moghaddam,b* Forugh Gudarzy,c Hadi Mohammadi,c Shahla Mozaffaric and Yadolah Ganjkhanloud ABSTRACT: Europium-doped yttrium oxide nanoparticles (Y2O3:Eu NPs) modified by captopril were prepared in aqueous solution. In this study, we report the effect of pyridoxine hydrochloride on the photoluminescence intensity of Y2O3:Eu NPs in pH 7.2 buffer solution. By increasing the pyridoxine concentration, the luminescence intensity of Y2O3:Eu NPs is quenched. The results show that this method demonstrates high sensitivity for pyridoxine determination. A linear relationship is observed between 0.0 and 62.0 μM with a correlation coefficient of 0.995 and a detection limit of 0.023 μM. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: nanoparticle; pyridoxine; photoluminescence; spectroscopy
Introduction Pyridoxine (C8H11NO3) is one of the three compounds (pyridoxine, pyridoxal and pyridoxamine) that can be called vitamin B6. It is based on a pyridine ring with hydroxyl, methyl and hydroxymethyl substituents (Fig. 1). It plays an important role in balancing of sodium and potassium, as well as promoting red blood cell production. Pyridoxine is involved in some metabolic processes such as amino acid, glucose and lipid metabolism, the synthesis of important molecules such as neurotransmitters, histamine and hemoglobin, and functions in gene expression (1,2). Thus, it is necessary to develop a simple and convenient method for the efficient detection of pyridoxine. Several methods have been used for pyridoxine detection, including spectrophotometry (2), chromatography (3) and electrochemical methods (4). Nanoparticles (NPs) have generated great fundamental and technical interest due to their superior optical and electronic properties, and have been widely used as fluorescence probes in biology and medicine (5–8). In the last 10 years, molecular diagnostics using nanomaterials has received considerable attention and has become an active field of research into assays for drugs and biomolecules. Because of their unique properties, different NPs, as well as metals, semiconductors and metal oxides, have attracted great attention in various fields (9,10). In general, they have size-related electronic, magnetic and optical properties, such as brightness, and strong photo and mechanical stability against photobleaching and blinking (11). Luminescent NPs could be used as luminescence indicators for different chemical and biological substances and drugs based on fluorescence quenching or enhancement. Analytes can affect the luminescence signal of NPs via electrostatic interactions, van der Waal’s interactions, hydrogen bonds, and hydrophobic and steric contacts within the binding site. For instance, Liu et al. used glutathione-capped CdTe/ZnS quantum dots (QDs) as fluorescence probes in the sensitive detection of rifampicin (12). Zhang et al. have realized the detection of uric
Luminescence 2014
acid in biologic medium through fluorescence quenching of positively charged CdTe QDs induced by uric acid, and applied the method to the determination of uric acid in human serum (13). Sun et al. used CdSe QDs as a proper probe for the determination of vitamin B1 based on the fluorescence quenching of CdSe QDs (14). Huang et al. proposed a new assay for urea based on measurement of the enhanced fluorescence intensity signal resulting from the interaction of CdSe/ZnS core-shell QDs (15). Ghosh et al. demonstrated that mannitol can be determined with cysteine-capped CdS QDs using optical spectroscopy (16). Also, Gao et al. suggested a nonenzymatic fluorescent sensor for glucose based on silica NPs doped with a europium coordination compound (17). Sun et al. developed a novel biosensor for bovine serum albumin based on fluorescent self-assembled sandwich bilayers (18) and Sotelo-Gonzalez et al. reported Mn-doped ZnS QDs for the determination of acetone by phosphorescence attenuation (19). In this study, we established the potential application of Y2O3: Eu NPs as fluorescence probes in a simple, rapid, sensitive and low-cost technique for the determination of pyridoxine. The fluorescence of modified Y2O3:Eu NPs can be quenched by adding pyridoxine in solution. The extent of the fluorescent intensity quenching is proportional to the concentration of
* Correspondence to: A. B. Moghaddam, Faculty of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran. E-mail: [email protected] a
Department of Chemistry, Islamic Azad University, Qeshm Branch, Iran
b
Faculty of Engineering Science, College of Engineering, University of Tehran, Tehran, Iran
c
Department of Chemistry, Payame Noor University, Tehran, Iran
d
Materials and Energy Research Center, Tehran, Iran
Copyright © 2014 John Wiley & Sons, Ltd.
E. Zobeiri et al. solution was titrated by successive addition of a freshly prepared stock solution of pyridoxine and the luminescence intensity was recorded at 612 nm with an excitation wavelength at 250 nm. Figure 1. Structure of (A) captopril as a modifier and (B) pyridoxine.
Results and discussions
pyridoxine. The obtained analytical parameters are summarized in Table 1. However, to our knowledge, modified Y2O3:Eu NPs-based fluorescent probes for pyridoxine have not been reported previously.
Experimental Instruments and chemicals All chemicals were of analytical grade and used without further purification. Pyridoxine hydrochloride (C8H11NO3, HCl) was purchased from Merck (product number 545072). Double-distilled water and pH 7.2 phosphate buffer solution (PBS) 0.25 M were used as solvents. High-resolution transmission electron microscopy (HRTEM) of the NPs was obtained using a Philips-CM200, 20–200 kV. The optical transmission/absorption spectra of the samples were recorded using a Shimadzu UV-Vis spectrophotometer. Fluorescence spectrophotometric studies were carried out using a CARY Eclipse fluorescence spectrophotometer. Synthesis of Eu-doped Y2O3 NPs Y2O3:Eu (3%) NPs were synthesized using a solution combustion method. In a typical synthesis, known stoichiometric amounts of europium and yttrium nitrates were dissolved in 25 mL of deionized water and mixed together. Urea was then added as a fuel to the solution in order to prepare an aqueous solution of urea, yttrium nitrate and europium nitrate at molar ratios of 2.5 : 0.970 : 0.03. The solution was heated in a furnace to evaporate the free water and the mixture abruptly combusted. Afterward the obtained powder was treated thermally for 1 h at 600ºC. An optimum Eu concentration of 3% was selected from our previous work (24).
The synthesized nanoparticles were analyzed by HRTEM (Fig. 2). It was found that good crystallinity was obtained using a combustion synthesis method. Furthermore, atomic planar distances, at 0.2 nm, and crystallite structure can be distinguished from this image. The NPs exhibited a broad absorption spectrum with a characteristic peak at 240 nm and a narrow emission band centered at 612 nm, which was obtained when the sample was irradiated at 250 nm wavelength. The narrow emission spectrum indicated the high degree of mono-dispersity of the NPs. The interaction between modified NPs and pyridoxine molecules needs a few minutes to become complete before the recording of fluorescence intensity.
Photoluminescence spectroscopy for the detection of pyridoxine Figure 3 shows the UV/vis absorption spectra of modified Y2O3: Eu NPs in the presence and absence of analyte. There was a weak absorption peak at 220 nm for pyridoxine (Fig. 3). So the quenching outcome of pyridoxine on the fluorescence of modified NPs was not due to an inner filter resulting from absorption of the emission wavelength by pyridoxine. The luminescence intensity of modified Y2O3:Eu NPs was examined using different concentrations of pyridoxine at pH 7.2 (Fig. 4). The quenching
Assay condition and photoluminescence measurement To determine the concentration of pyridoxine, 0.05 g Y2O3:Eu NPs were sonicated for 30 min in 100 mL of buffer solution. The remaining upper suspension was decanted from the precipitate and used in the next stage. Then, 5 mL of the suspension was transferred into a calibrated 10 mL tube and captopril was added as a modifier to the solution. Five milliliters of the mixed
Figure 2. TEM image of Y2O3:Eu NPs.
Table 1. Some analytical methods for pyridoxine assay Method Spectrophotometry Spectrophotometry HPLC Electrochemistry flow injection-solid phase spectrophotometry Photoluminescence
LR (M) 2–20 μg/mL 1–10 μg/mL 4–100 ng 10-1–7.1 × 10-4 0.5–10 mg/L 33.22–445.9 μg/mL
DL (M) 0.02 μg/mL 0.08 μg/mL 4 ng 2.5 × 10-4 0.15 mg/L 0.15 μg/mL
RSD (%) 0.84 0.65
Revised: 26 April 2014,
Accepted: 22 May 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2727
Modified Eu-doped Y2O3 nanoparticles as turnoff luminescent probes for the sensitive detection of pyridoxine Eshagh Zobeiri,a Abdolmajid Bayandori Moghaddam,b* Forugh Gudarzy,c Hadi Mohammadi,c Shahla Mozaffaric and Yadolah Ganjkhanloud ABSTRACT: Europium-doped yttrium oxide nanoparticles (Y2O3:Eu NPs) modified by captopril were prepared in aqueous solution. In this study, we report the effect of pyridoxine hydrochloride on the photoluminescence intensity of Y2O3:Eu NPs in pH 7.2 buffer solution. By increasing the pyridoxine concentration, the luminescence intensity of Y2O3:Eu NPs is quenched. The results show that this method demonstrates high sensitivity for pyridoxine determination. A linear relationship is observed between 0.0 and 62.0 μM with a correlation coefficient of 0.995 and a detection limit of 0.023 μM. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: nanoparticle; pyridoxine; photoluminescence; spectroscopy
Introduction Pyridoxine (C8H11NO3) is one of the three compounds (pyridoxine, pyridoxal and pyridoxamine) that can be called vitamin B6. It is based on a pyridine ring with hydroxyl, methyl and hydroxymethyl substituents (Fig. 1). It plays an important role in balancing of sodium and potassium, as well as promoting red blood cell production. Pyridoxine is involved in some metabolic processes such as amino acid, glucose and lipid metabolism, the synthesis of important molecules such as neurotransmitters, histamine and hemoglobin, and functions in gene expression (1,2). Thus, it is necessary to develop a simple and convenient method for the efficient detection of pyridoxine. Several methods have been used for pyridoxine detection, including spectrophotometry (2), chromatography (3) and electrochemical methods (4). Nanoparticles (NPs) have generated great fundamental and technical interest due to their superior optical and electronic properties, and have been widely used as fluorescence probes in biology and medicine (5–8). In the last 10 years, molecular diagnostics using nanomaterials has received considerable attention and has become an active field of research into assays for drugs and biomolecules. Because of their unique properties, different NPs, as well as metals, semiconductors and metal oxides, have attracted great attention in various fields (9,10). In general, they have size-related electronic, magnetic and optical properties, such as brightness, and strong photo and mechanical stability against photobleaching and blinking (11). Luminescent NPs could be used as luminescence indicators for different chemical and biological substances and drugs based on fluorescence quenching or enhancement. Analytes can affect the luminescence signal of NPs via electrostatic interactions, van der Waal’s interactions, hydrogen bonds, and hydrophobic and steric contacts within the binding site. For instance, Liu et al. used glutathione-capped CdTe/ZnS quantum dots (QDs) as fluorescence probes in the sensitive detection of rifampicin (12). Zhang et al. have realized the detection of uric
Luminescence 2014
acid in biologic medium through fluorescence quenching of positively charged CdTe QDs induced by uric acid, and applied the method to the determination of uric acid in human serum (13). Sun et al. used CdSe QDs as a proper probe for the determination of vitamin B1 based on the fluorescence quenching of CdSe QDs (14). Huang et al. proposed a new assay for urea based on measurement of the enhanced fluorescence intensity signal resulting from the interaction of CdSe/ZnS core-shell QDs (15). Ghosh et al. demonstrated that mannitol can be determined with cysteine-capped CdS QDs using optical spectroscopy (16). Also, Gao et al. suggested a nonenzymatic fluorescent sensor for glucose based on silica NPs doped with a europium coordination compound (17). Sun et al. developed a novel biosensor for bovine serum albumin based on fluorescent self-assembled sandwich bilayers (18) and Sotelo-Gonzalez et al. reported Mn-doped ZnS QDs for the determination of acetone by phosphorescence attenuation (19). In this study, we established the potential application of Y2O3: Eu NPs as fluorescence probes in a simple, rapid, sensitive and low-cost technique for the determination of pyridoxine. The fluorescence of modified Y2O3:Eu NPs can be quenched by adding pyridoxine in solution. The extent of the fluorescent intensity quenching is proportional to the concentration of
* Correspondence to: A. B. Moghaddam, Faculty of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran. E-mail: [email protected] a
Department of Chemistry, Islamic Azad University, Qeshm Branch, Iran
b
Faculty of Engineering Science, College of Engineering, University of Tehran, Tehran, Iran
c
Department of Chemistry, Payame Noor University, Tehran, Iran
d
Materials and Energy Research Center, Tehran, Iran
Copyright © 2014 John Wiley & Sons, Ltd.
E. Zobeiri et al. solution was titrated by successive addition of a freshly prepared stock solution of pyridoxine and the luminescence intensity was recorded at 612 nm with an excitation wavelength at 250 nm. Figure 1. Structure of (A) captopril as a modifier and (B) pyridoxine.
Results and discussions
pyridoxine. The obtained analytical parameters are summarized in Table 1. However, to our knowledge, modified Y2O3:Eu NPs-based fluorescent probes for pyridoxine have not been reported previously.
Experimental Instruments and chemicals All chemicals were of analytical grade and used without further purification. Pyridoxine hydrochloride (C8H11NO3, HCl) was purchased from Merck (product number 545072). Double-distilled water and pH 7.2 phosphate buffer solution (PBS) 0.25 M were used as solvents. High-resolution transmission electron microscopy (HRTEM) of the NPs was obtained using a Philips-CM200, 20–200 kV. The optical transmission/absorption spectra of the samples were recorded using a Shimadzu UV-Vis spectrophotometer. Fluorescence spectrophotometric studies were carried out using a CARY Eclipse fluorescence spectrophotometer. Synthesis of Eu-doped Y2O3 NPs Y2O3:Eu (3%) NPs were synthesized using a solution combustion method. In a typical synthesis, known stoichiometric amounts of europium and yttrium nitrates were dissolved in 25 mL of deionized water and mixed together. Urea was then added as a fuel to the solution in order to prepare an aqueous solution of urea, yttrium nitrate and europium nitrate at molar ratios of 2.5 : 0.970 : 0.03. The solution was heated in a furnace to evaporate the free water and the mixture abruptly combusted. Afterward the obtained powder was treated thermally for 1 h at 600ºC. An optimum Eu concentration of 3% was selected from our previous work (24).
The synthesized nanoparticles were analyzed by HRTEM (Fig. 2). It was found that good crystallinity was obtained using a combustion synthesis method. Furthermore, atomic planar distances, at 0.2 nm, and crystallite structure can be distinguished from this image. The NPs exhibited a broad absorption spectrum with a characteristic peak at 240 nm and a narrow emission band centered at 612 nm, which was obtained when the sample was irradiated at 250 nm wavelength. The narrow emission spectrum indicated the high degree of mono-dispersity of the NPs. The interaction between modified NPs and pyridoxine molecules needs a few minutes to become complete before the recording of fluorescence intensity.
Photoluminescence spectroscopy for the detection of pyridoxine Figure 3 shows the UV/vis absorption spectra of modified Y2O3: Eu NPs in the presence and absence of analyte. There was a weak absorption peak at 220 nm for pyridoxine (Fig. 3). So the quenching outcome of pyridoxine on the fluorescence of modified NPs was not due to an inner filter resulting from absorption of the emission wavelength by pyridoxine. The luminescence intensity of modified Y2O3:Eu NPs was examined using different concentrations of pyridoxine at pH 7.2 (Fig. 4). The quenching
Assay condition and photoluminescence measurement To determine the concentration of pyridoxine, 0.05 g Y2O3:Eu NPs were sonicated for 30 min in 100 mL of buffer solution. The remaining upper suspension was decanted from the precipitate and used in the next stage. Then, 5 mL of the suspension was transferred into a calibrated 10 mL tube and captopril was added as a modifier to the solution. Five milliliters of the mixed
Figure 2. TEM image of Y2O3:Eu NPs.
Table 1. Some analytical methods for pyridoxine assay Method Spectrophotometry Spectrophotometry HPLC Electrochemistry flow injection-solid phase spectrophotometry Photoluminescence
LR (M) 2–20 μg/mL 1–10 μg/mL 4–100 ng 10-1–7.1 × 10-4 0.5–10 mg/L 33.22–445.9 μg/mL
DL (M) 0.02 μg/mL 0.08 μg/mL 4 ng 2.5 × 10-4 0.15 mg/L 0.15 μg/mL
RSD (%) 0.84 0.65
