- Email: [email protected]
A simple ratiometric fluorescent sensor for fructose based on complexation of 10-hydroxybenzo[h]quinoline with boronic acid
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
A simple ratiometric fluorescent sensor for fructose based on complexation of 10-hydroxybenzo[h]quinoline with boronic acid Huihui Li a, Cailing Yang b, Xinyue Zhu a, Haixia Zhang a,⁎ a b
State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China School of Chemistry and Environmental Engineering, Lanzhou City University, Lanzhou 730070, China
a r t i c l e
i n f o
Article history: Received 5 January 2017 Received in revised form 20 February 2017 Accepted 6 March 2017 Available online 07 March 2017 Keywords: Ratiometric fluorescence Fructose 10-Hydroxybenzo[h]quinoline Boronic acid
a b s t r a c t A simple ratiometric fluorescent sensor for fructose was presented. It consisted of 10-hydroxybenzo[h]quinoline (HBQ) which showed emission at 572 nm and 3-pyridylboronic acid (PDBA) whose complex with HBQ gave emission at 500 nm. The reaction of fructose with PDBA inhibited the complexation of HBQ with PDBA, resulting in the change of dual-emission intensity ratio. The sensor well quantified fructose in the range of 0.015–2.5 mM with detection limit of 0.005 mM. Besides, this sensor exhibited excellent selectivity and was successfully applied to fructose detection in food. This work provides a simple ratiometric sensing platform for sensitive and selective detection of fructose. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Fructose, a kind of sugar with high sweetness, is widely used as a sweetener in food chemistry. Owing to its metabolic property, high fructose consumption can cause many diseases including hyperinsulinemia, hyperglycemia, hypertension, hyperuricemia, obesity, renal disease and metabolic syndrome [1–5]. Therefore fructose detection is of great importance for quality control of food and human health. Traditional methods for fructose detection include gas chromatography [6] and liquid chromatography [7], but they are expensive and time-consuming with expensive instrumentation, well trained operator and longtime of analysis. To avoid these disadvantages, fructose sensors are developed, such as electrochemistry [8,9], fluorometry [10,11] and colorimetry [12,13], but their preparation with multi-step reactions are complicated. There is need to explore simple fructose sensors. Boronic acids have been widely used as receptors of fructose sensors [14–16].The principle is based on that boronic acid reacts with fructose to form five-membered cyclic ester. It was reported that 10-hydroxybenzo[h]quinoline (HBQ) was a ratiometric fluorescent sensor for boronic acids [17]. The response mechanism is illuminated in Fig. 1: HBQ showed emission at 572 nm, and its complex with boronic acid gave emission at 500 nm. Inspired the above work, a fructose sensor (HBQ-PDBA), consisting of HBQ and 3-pyridylboronic acid (PDBA), was proposed. The response mechanism relied on that the reaction of fructose with PDBA inhibited the complexation of HBQ with PDBA (Fig. 1). PDBA was chosen due to ⁎ Corresponding author. E-mail address: [email protected] (H. Zhang).
http://dx.doi.org/10.1016/j.saa.2017.03.017 1386-1425/© 2017 Elsevier B.V. All rights reserved.
that it had a low pKa of 4.4 [18], making the sensor had a wide applicable pH range. On one hand, requiring no synthesis as HBQ and PDBA were commercial available with low cost, HBQ-PDBA was simple and inexpensive. On the other hand, HBQ-PDBA as a ratiometric sensor exhibited high stability against environmental effects. 2. Experimental 2.1. Reagents and Instrumentations 10-Hydroxybenzo[h]quinoline (HBQ), fructose, glucose, mannose, galactose, sucrose and maltose were purchased from Aladdin Chemistry Co. Ltd. (Shanghai, China). 3-Pyridylboronic acid (PDBA) was from Energy Chemical (Shanghai, China). All other reagents were of analytical grade (Tianjin, China). The water used throughout the experiment was supplied by Milli-Q system (Millipore, Bedford, MA, USA). Stock solutions of HBQ (0.5 mM) and PDBA (0.5 mM) were prepared in DMSO and stored at 4 °C in the dark. Stock solution of fructose (100 mM) was prepared in water and stored at 4 °C in the dark. Fluorescence spectra were measured by a Fluorescence spectrometer (RF-5301pc, Japan) with Xenon lamp and 1.0-cm quartz cell at the slits of 5/10 nm. Absorption spectra were measured on a UV–visible spectrophotometer (TU-1810, China). 2.2. Procedure for Fructose Detection Different concentrations of fructose (0.2 mL), PDBA (0.5 mL, 0.5 mM) and HBQ (0.5 mL, 0.5 mM) were added to PBS buffer (3.8 mL, 10 mM, pH 7.4). The obtained solutions were incubated at
200
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
Fig. 1. Working principle for fructose detection via HBQ-PDBA.
37 °C for 10 min. Fluorescence spectra were then recorded with the excitation and emission wavelengths at 380 and 572/500 nm, respectively. Honey and beverages were purchased from local supermarket, and they did not require any pretreatment except dilution with water. 3. Results and Discussion 3.1. Response of HBQ to PDBA Response of HBQ to PDBA on solid supports has been evaluated in previous report [17]. Fructose detection was performed in aqueous solution, thereby this study focused on investigating response of HBQ to PDBA in aqueous solution. Absorption of HBQ was red-shift after its complexation with boronic acid [17]. Fig. 2A presents the absorption spectra of HBQ before and after adding PDBA. It was observed that the maximum absorption of HBQ appeared at 365 nm and decreased slightly after addition of PDBA, indicating that the complexation degree of HBQ with PDBA was very low in aqueous solution. Fig. 2B shows the fluorescence spectra of HBQ after adding different concentrations of PDBA. Without adding PDBA, HBQ showed emission at 572 nm. With adding PDBA, emissions at 500 nm and 572 nm increased in different degrees. Emission at 500 nm increased remarkably with adding PDBA, as complex of PDBA with HBQ gave emission at 500 nm [17]. Since the complexation degree of HBQ with PDBA was
very low, emission of HBQ decreased slightly after adding PDBA. However, the increased emission of the complex obscured the decreased emission of HBQ owing to spectral overlap, resulting in the slight increase of emission at 572 nm after adding PDBA. In summary, dualemission intensity ratio changed after adding PDBA, thus HBQ showed ratiometric response to PDBA in aqueous solution. Emission at 572 nm was covered by that at 500 nm when PDBA concentration was above 50 μM, thereby 50 μM PDBA was used for further study. 3.2. Factors Affecting Fructose Detection Fructose reacted with PDBA to form five-membered cyclic ester which inhibited the complexation of HBQ with PDBA, thereby HBQ and PDBA can be used for ratiometric detection of fructose. As shown in Fig. 3A, emissions at 500 nm and 572 nm decreased in different degrees after adding fructose. For better sensing performance, the experimental conditions, including pH and incubation time, were optimized. Effect of pH was investigated by varying pH value between 4.5 and 9.0 (Fig. 3B). HBQ-PDBA responded to fructose at a wide pH range (4.5–9.0), due to that PDBA had a low pKa of 4.4 [18]. Response became stronger with raising pH values from 4.5 to 7.4, and then decreased when pH value was above 7.4. The increased response was attributed to that high pH values facilitated PDBA to form five-membered cyclic ester with fructose. The reason for reduced response was that the complexation of HBQ with PDBA became weaker with increasing pH values
Fig. 2. (A) Absorption spectra of HBQ before and after addition of PDBA. (B) Fluorescence spectra of HBQ after adding different concentrations of PDBA. Experimental conditions: HBQ concentration: 50 μM (A and B), PDBA concentration: 50 μM (A), solvent: 10 mM PBS buffer/DMSO (4:1, v/v) (A and B), pH: 7.4 (A and B), incubation time: 10 min (A and B), temperature: 37 °C (A and B).
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
201
Fig. 3. (A) Fluorescence spectra of HBQ-PDBA before and after addition of fructose. (B) Effect of pH on fructose detection. (C) Effect of pH on complexation of HBQ with PDBA. (D) Effect of incubation time on fructose detection. Experimental conditions: HBQ concentration: 50 μM (A, B, C and D), PDBA concentration: 50 μM (A, B, C and D), fructose concentration: 0.20 mM (A, B and D), solvent: 10 mM PBS buffer/DMSO (4:1, v/v) (A, B, C and D), pH: 7.4 (A and D), incubation time: 10 min (A, B and C), temperature: 37 °C (A, B, C and D).
(Fig. 3C) caused by that the complexation of OH− with PDBA inhibited that of HBQ with PDBA as shown in Fig. 1. Thereby pH 7.4 was adopted in further study. Effect of incubation time was investigated over a time period of 0–60 min (Fig. 3D). It was that observed response reached equilibrium at 10 min. As a consequence, 10 min of incubation was employed in subsequent experiment.
the results were compared with those obtained from resorcinol method (Supplementary material). As shown in Table 1, the results measured by this method were consistent with those obtained from resorcinol method, indicating the feasibility of HBQ-PDBA for fructose detection in food samples. Moreover, most results obtained from resorcinol method showed slightly higher values, due to that acidic
3.3. Selectivity of HBQ-PDBA Other sugars, including glucose, galactose, mannose, sucrose and maltose, were used to investigate selectivity of HBQ-PDBA. As shown in Fig. 4, the response of HBQ-PDBA to these five sugars was negligible, indicating that HBQ-PDBA possessed excellent selectivity, which was attributed that compared with other sugars fructose exhibited higher association constant with boronic acid [16,19]. 3.4. Analytical Performance for Fructose Detection As shown in Fig. 5A, with adding fructose emissions at 500 nm and 572 nm decreased in different degrees. Dual-emission intensity ratio (I572/I500) increased linearly with fructose concentration in the range from 0.015 to 2.5 mM (R2 = 0.9945) (Fig. 5B). Limit of detection (LOD) was calculated as 0.005 mM (S/N = 3). 3.5. Fructose Detection in Food HBQ-PDBA was used for fructose detection in food samples including honey, fruit juice, carbonated drink and energy drink, and
Fig. 4. Response of HBQ-PDBA to different sugars (1.0 mM). HBQ concentration: 50 μM, PDBA concentration: 50 μM, solvent: 10 mM PBS buffer/DMSO (4:1, v/v), pH: 7.4, incubation time: 10 min, temperature: 37 °C.
202
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
Fig. 5. (A) Fluorescence spectra of HBQ-PDBA after adding different concentrations of fructose (0, 0.015, 0.060, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 1.0, 1.5, 2.0, 2.5 mM). (B) Linear correlation between dual-emission intensity ratio (I572/I500) and fructose concentration (0.015–2.5 mM). HBQ concentration: 50 μM, PDBA concentration: 50 μM, solvent: 10 mM PBS buffer/DMSO (4:1, v/v), pH: 7.4, incubation time: 10 min, temperature: 37 °C.
Table 1 Results of fructose detection in food samples.
and lower LOD. Accordingly, HBQ-PDBA exhibited the merits of simplicity, inexpensiveness and sensitivity.
Sample
[Fructose] (mM) Resorcinol method
[Fructose] (mM) This method
Honey Apple juice Cola Energy drink
3974.1 ± 182.9 478.7 ± 51.9 351.6 ± 21.7 167.0 ± 19.5
3655.6 ± 48.5 503.7 ± 32.0 326.9 ± 11.9 144.2 ± 7.8
experimental condition resulted in hydrolysis of disaccharide and polysaccharide in food samples. Table 2 presents comparison between HBQ-PDBA and reported fructose sensors [8,10–13,16,20–23] in terms of preparation step, linear range, LOD and real sample. Compared with the same type of sensors using ratiometric fluorescent method [16,20–22], HBQ-PDBA required no synthesis as HBQ and PDBA were commercial available with low cost, thereby it was simpler and more inexpensive. Compared with other types of sensors, such as fluorometry [10,11,23], electrochemistry [8] and colorimetry [12,13], HBQ-PDBA possessed less preparation steps
4. Conclusion A fluorescent fructose sensor based on complexation of HBQ with PDBA was reported. Compared with reported fructose sensors, it exhibited three advantages: (i) requiring no synthesis, it was simple and inexpensive; (ii) it as a ratiometric sensor was stable; (iii) it was sensitive with low LOD. This work provides a simple and inexpensive sensing platform for stable and sensitive detection of fructose. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (No. 21375052 and 21575055). Appendix A. Supplementary Data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.saa.2017.03.017.
Table 2 Comparison between HBQ-PDBA and reported fructose sensors. Sensor
Preparation step
Linear range (mM)
LOD (mM)
Real sample
Reference
5-DMANBAa C1-APBb and β-cyclodextrin Amphiphilic dipeptide bearing pyrene and boronic acid Polymer containing GS-MAc and Rhod-MAd Phenylboronic acid modified acrylic polymer HPTSe and m-P3BQf Fluorene-based fluorescent boronic acid FDHg modified SPFCEh APBi and GTEj modified AuNPs Self-assembled block copolymer photonic crystal HBQ-PDBA
4 1 8 9 6 1 6 1 4 2 −
− 0–10 0–2.5 0–5 0–10 0–100 0.025–0.4 0.1–1 2.8–33.3 − 0.015–2.5
− − − − 0.4 − 0.013 0.05 1.7 1 0.005
− − − − − − − Food Semen − Food
[20] [21] [16] [22] [10] [11] [23] [8] [12] [13] This work
a b c d e f g h i j
5-(Dimethylamino)naphthalene-1-boronic acid. 2-(4-Phenylboronic acid)-1-pyrenemethamide. Monomer containing boronic acid-based fructose sensor. Monomer containing rhodamine. 8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt. 1,3-Bis(pyridyl-3-boronic acid)benzyl quaternary ammonium dibromide. Fructose dehydrogenase. Screen-printed ferrocyanide/carbon electrode. 3-Aminophenyl boronic acid. L-Glutamic acid-(2,2,2)-trichloroethyl ester.
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
References [1] C.M.M.R. Barros, R.Q. Lessa, M.P. Grechi, T.L.M. Mouco, M.D.C. Souza, N. Wiernsperger, E. Bouskela, Substitution of drinking water by fructose solution induces hyperinsulinemia and hyperglycemia in hamsters, Clinics 62 (2007) 327–334. [2] G.A. Bray, S.J. Nielsen, B.M. Popkin, Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity, Am. J. Clin. Nutr. 79 (2004) 537–543. [3] M. Heinig, R.J. Johnson, Role of uric acid in hypertension, renal disease, and metabolic syndrome, Cleve. Clin. J. Med. 73 (2006) 1059–1064. [4] T. Nakagawa, K.R. Tuttle, R.A. Short, R.J. Johnson, Hypothesis: fructose-induced hyperuricemia as a causal mechanism for the epidemic of the metabolic syndrome, Nat. Clin. Pract. Nephrol. 1 (2005) 80–86. [5] T. Nakagawa, H.B. Hu, S. Zharikov, K.R. Tuttle, R.A. Short, O. Glushakova, X. Ouyang, D.I. Feig, E.R. Block, J. Herrera-Acosta, J.M. Patel, R.J. Johnson, A causal role for uric acid in fructose-induced metabolic syndrome, Am. J. Physiol. Ren. Physiol. 290 (2006) F625–F631. [6] P.N. Wahjudi, M.E. Patterson, S. Lim, J.K. Yee, C.S. Mao, W.N.P. Lee, Measurement of glucose and fructose in clinical samples using gas chromatography/mass spectrometry, Clin. Biochem. 43 (2010) 198–207. [7] C.M. Ma, Z. Sun, C.B. Chen, L.L. Zhang, S.H. Zhu, Simultaneous separation and determination of fructose, sorbitol, glucose and sucrose in fruits by HPLC-ELSD, Food Chem. 145 (2014) 784–788. [8] J. Biscay, E.C. Rama, M.B.G. Garcia, A.J. Reviejo, J.M.P. Carrazon, A.C. Gacia, Amperometric fructose sensor based on ferrocyanide modified screen-printed carbon electrode, Talanta 88 (2012) 432–438. [9] J.L. Montanez-Soto, S. Alegret, J.A. Salazar-Montoya, E.G. Ramos-Ramirez, A new amperometric biosensor for fructose determination based on epoxy-graphite-TTFTCNQ-FDH-biocomposite, Eur. Food Res. Technol. 223 (2006) 379–386. [10] J.L. Pablos, S. Vallejos, S. Ibeas, A. Munoz, F. Serna, F.C. Garcia, J.M. Garcia, Acrylic polymers with pendant phenylboronic acid moieties as “ turn-off” and “ turn-on” fluorescence solid sensors for detection of dopamine, glucose, and fructose in water, ACS Macro Lett. 4 (2015) 979–983. [11] L.H. Feng, F. Liang, Y. Wang, X.J. Wang, A facile sensor for D-fructose with fluorescence “on–off–on” switch ensemble, Sensors Actuators B 173 (2012) 575–579.
203
[12] V. Raj, A.N. Vijayan, K. Joseph, Naked eye detection of infertility using fructose blue—a novel gold nanoparticle based fructose sensor, Biosens. Bioelectron. 54 (2014) 171–174. [13] O.B. Ayyub, M.B. Ibrahim, R.M. Briber, P. Kofinas, Self-assembled block copolymer photonic crystal for selective fructose detection, Biosens. Bioelectron. 46 (2013) 124–129. [14] Z.J. Wang, H.Y. Lei, C.Y. Zhou, G.F. Wang, L.H. Feng, Highly selective ensembles for Dfructose based on fluorescent method in aqueous solution, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 91 (2012) 178–183. [15] D. Oesch, N.W. Luedtke, Fluorescent chemosensors of carbohydrate triols exhibiting TICT emissions, Chem. Commun. 51 (2015) 12641–12644. [16] L.N. Neupane, S.Y. Han, K.H. Lee, Ratiometric fluorescence sensing of sugars via a reversible disassembly and assembly of the peptide aggregates mediated by sugars, Chem. Commun. 50 (2014) 5854–5857. [17] M.R. Aronoff, B. VanVeller, R.T. Raines, Detection of boronic acids through excitedstate intramolecular proton-transfer fluorescence, Org. Lett. 15 (2013) 5382–5385. [18] D.J. Li, Q.J. Li, S.S. Wang, J. Ye, H.Y. Nie, Z. Liu, Pyridinylboronic acid-functionalized organic-silica hybrid monolithic capillary for the selective enrichment and separation of cis-diol-containing biomolecules at acidic pH, J. Chromatogr. A 1339 (2014) 103–109. [19] Y. Liu, C.M. Deng, L. Tang, A.J. Qin, R.R. Hu, J.Z. Sun, B.Z. Tang, Specific detection of Dglucose by a tetraphenylethene-based fluorescent sensor, J. Am. Chem. Soc. 133 (2011) 660–663. [20] X.M. Gao, Y.L. Zhang, B.H. Wang, Naphthalene-based water-soluble fluorescent boronic acid isomers suitable for ratiometric and off-on sensing of saccharides at physiological pH, New J. Chem. 29 (2005) 579–586. [21] R. Ozawa, T. Hashimoto, A. Yamauchi, I. Suzuki, B.D. Smith, T. Hayashita, Effect of cyclodextrins on saccharide sensing function of a fluorescent phenylboronic acid in water, Anal. Sci. 24 (2008) 207–212. [22] L.Q. Zhang, F.Y. Su, S. Buizer, X.X. Kong, F. Lee, K. Day, Y.Q. Tian, D.R. Meldrum, A polymer-based ratiometric intracellular glucose sensor, Chem. Commun. 50 (2014) 6920–6922. [23] R. Hosseinzadeh, M. Mohadjerani, M. Pooryousef, A. Eslami, S. Emami, A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 144 (2015) 53–60.
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
A simple ratiometric fluorescent sensor for fructose based on complexation of 10-hydroxybenzo[h]quinoline with boronic acid Huihui Li a, Cailing Yang b, Xinyue Zhu a, Haixia Zhang a,⁎ a b
State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China School of Chemistry and Environmental Engineering, Lanzhou City University, Lanzhou 730070, China
a r t i c l e
i n f o
Article history: Received 5 January 2017 Received in revised form 20 February 2017 Accepted 6 March 2017 Available online 07 March 2017 Keywords: Ratiometric fluorescence Fructose 10-Hydroxybenzo[h]quinoline Boronic acid
a b s t r a c t A simple ratiometric fluorescent sensor for fructose was presented. It consisted of 10-hydroxybenzo[h]quinoline (HBQ) which showed emission at 572 nm and 3-pyridylboronic acid (PDBA) whose complex with HBQ gave emission at 500 nm. The reaction of fructose with PDBA inhibited the complexation of HBQ with PDBA, resulting in the change of dual-emission intensity ratio. The sensor well quantified fructose in the range of 0.015–2.5 mM with detection limit of 0.005 mM. Besides, this sensor exhibited excellent selectivity and was successfully applied to fructose detection in food. This work provides a simple ratiometric sensing platform for sensitive and selective detection of fructose. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Fructose, a kind of sugar with high sweetness, is widely used as a sweetener in food chemistry. Owing to its metabolic property, high fructose consumption can cause many diseases including hyperinsulinemia, hyperglycemia, hypertension, hyperuricemia, obesity, renal disease and metabolic syndrome [1–5]. Therefore fructose detection is of great importance for quality control of food and human health. Traditional methods for fructose detection include gas chromatography [6] and liquid chromatography [7], but they are expensive and time-consuming with expensive instrumentation, well trained operator and longtime of analysis. To avoid these disadvantages, fructose sensors are developed, such as electrochemistry [8,9], fluorometry [10,11] and colorimetry [12,13], but their preparation with multi-step reactions are complicated. There is need to explore simple fructose sensors. Boronic acids have been widely used as receptors of fructose sensors [14–16].The principle is based on that boronic acid reacts with fructose to form five-membered cyclic ester. It was reported that 10-hydroxybenzo[h]quinoline (HBQ) was a ratiometric fluorescent sensor for boronic acids [17]. The response mechanism is illuminated in Fig. 1: HBQ showed emission at 572 nm, and its complex with boronic acid gave emission at 500 nm. Inspired the above work, a fructose sensor (HBQ-PDBA), consisting of HBQ and 3-pyridylboronic acid (PDBA), was proposed. The response mechanism relied on that the reaction of fructose with PDBA inhibited the complexation of HBQ with PDBA (Fig. 1). PDBA was chosen due to ⁎ Corresponding author. E-mail address: [email protected] (H. Zhang).
http://dx.doi.org/10.1016/j.saa.2017.03.017 1386-1425/© 2017 Elsevier B.V. All rights reserved.
that it had a low pKa of 4.4 [18], making the sensor had a wide applicable pH range. On one hand, requiring no synthesis as HBQ and PDBA were commercial available with low cost, HBQ-PDBA was simple and inexpensive. On the other hand, HBQ-PDBA as a ratiometric sensor exhibited high stability against environmental effects. 2. Experimental 2.1. Reagents and Instrumentations 10-Hydroxybenzo[h]quinoline (HBQ), fructose, glucose, mannose, galactose, sucrose and maltose were purchased from Aladdin Chemistry Co. Ltd. (Shanghai, China). 3-Pyridylboronic acid (PDBA) was from Energy Chemical (Shanghai, China). All other reagents were of analytical grade (Tianjin, China). The water used throughout the experiment was supplied by Milli-Q system (Millipore, Bedford, MA, USA). Stock solutions of HBQ (0.5 mM) and PDBA (0.5 mM) were prepared in DMSO and stored at 4 °C in the dark. Stock solution of fructose (100 mM) was prepared in water and stored at 4 °C in the dark. Fluorescence spectra were measured by a Fluorescence spectrometer (RF-5301pc, Japan) with Xenon lamp and 1.0-cm quartz cell at the slits of 5/10 nm. Absorption spectra were measured on a UV–visible spectrophotometer (TU-1810, China). 2.2. Procedure for Fructose Detection Different concentrations of fructose (0.2 mL), PDBA (0.5 mL, 0.5 mM) and HBQ (0.5 mL, 0.5 mM) were added to PBS buffer (3.8 mL, 10 mM, pH 7.4). The obtained solutions were incubated at
200
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
Fig. 1. Working principle for fructose detection via HBQ-PDBA.
37 °C for 10 min. Fluorescence spectra were then recorded with the excitation and emission wavelengths at 380 and 572/500 nm, respectively. Honey and beverages were purchased from local supermarket, and they did not require any pretreatment except dilution with water. 3. Results and Discussion 3.1. Response of HBQ to PDBA Response of HBQ to PDBA on solid supports has been evaluated in previous report [17]. Fructose detection was performed in aqueous solution, thereby this study focused on investigating response of HBQ to PDBA in aqueous solution. Absorption of HBQ was red-shift after its complexation with boronic acid [17]. Fig. 2A presents the absorption spectra of HBQ before and after adding PDBA. It was observed that the maximum absorption of HBQ appeared at 365 nm and decreased slightly after addition of PDBA, indicating that the complexation degree of HBQ with PDBA was very low in aqueous solution. Fig. 2B shows the fluorescence spectra of HBQ after adding different concentrations of PDBA. Without adding PDBA, HBQ showed emission at 572 nm. With adding PDBA, emissions at 500 nm and 572 nm increased in different degrees. Emission at 500 nm increased remarkably with adding PDBA, as complex of PDBA with HBQ gave emission at 500 nm [17]. Since the complexation degree of HBQ with PDBA was
very low, emission of HBQ decreased slightly after adding PDBA. However, the increased emission of the complex obscured the decreased emission of HBQ owing to spectral overlap, resulting in the slight increase of emission at 572 nm after adding PDBA. In summary, dualemission intensity ratio changed after adding PDBA, thus HBQ showed ratiometric response to PDBA in aqueous solution. Emission at 572 nm was covered by that at 500 nm when PDBA concentration was above 50 μM, thereby 50 μM PDBA was used for further study. 3.2. Factors Affecting Fructose Detection Fructose reacted with PDBA to form five-membered cyclic ester which inhibited the complexation of HBQ with PDBA, thereby HBQ and PDBA can be used for ratiometric detection of fructose. As shown in Fig. 3A, emissions at 500 nm and 572 nm decreased in different degrees after adding fructose. For better sensing performance, the experimental conditions, including pH and incubation time, were optimized. Effect of pH was investigated by varying pH value between 4.5 and 9.0 (Fig. 3B). HBQ-PDBA responded to fructose at a wide pH range (4.5–9.0), due to that PDBA had a low pKa of 4.4 [18]. Response became stronger with raising pH values from 4.5 to 7.4, and then decreased when pH value was above 7.4. The increased response was attributed to that high pH values facilitated PDBA to form five-membered cyclic ester with fructose. The reason for reduced response was that the complexation of HBQ with PDBA became weaker with increasing pH values
Fig. 2. (A) Absorption spectra of HBQ before and after addition of PDBA. (B) Fluorescence spectra of HBQ after adding different concentrations of PDBA. Experimental conditions: HBQ concentration: 50 μM (A and B), PDBA concentration: 50 μM (A), solvent: 10 mM PBS buffer/DMSO (4:1, v/v) (A and B), pH: 7.4 (A and B), incubation time: 10 min (A and B), temperature: 37 °C (A and B).
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
201
Fig. 3. (A) Fluorescence spectra of HBQ-PDBA before and after addition of fructose. (B) Effect of pH on fructose detection. (C) Effect of pH on complexation of HBQ with PDBA. (D) Effect of incubation time on fructose detection. Experimental conditions: HBQ concentration: 50 μM (A, B, C and D), PDBA concentration: 50 μM (A, B, C and D), fructose concentration: 0.20 mM (A, B and D), solvent: 10 mM PBS buffer/DMSO (4:1, v/v) (A, B, C and D), pH: 7.4 (A and D), incubation time: 10 min (A, B and C), temperature: 37 °C (A, B, C and D).
(Fig. 3C) caused by that the complexation of OH− with PDBA inhibited that of HBQ with PDBA as shown in Fig. 1. Thereby pH 7.4 was adopted in further study. Effect of incubation time was investigated over a time period of 0–60 min (Fig. 3D). It was that observed response reached equilibrium at 10 min. As a consequence, 10 min of incubation was employed in subsequent experiment.
the results were compared with those obtained from resorcinol method (Supplementary material). As shown in Table 1, the results measured by this method were consistent with those obtained from resorcinol method, indicating the feasibility of HBQ-PDBA for fructose detection in food samples. Moreover, most results obtained from resorcinol method showed slightly higher values, due to that acidic
3.3. Selectivity of HBQ-PDBA Other sugars, including glucose, galactose, mannose, sucrose and maltose, were used to investigate selectivity of HBQ-PDBA. As shown in Fig. 4, the response of HBQ-PDBA to these five sugars was negligible, indicating that HBQ-PDBA possessed excellent selectivity, which was attributed that compared with other sugars fructose exhibited higher association constant with boronic acid [16,19]. 3.4. Analytical Performance for Fructose Detection As shown in Fig. 5A, with adding fructose emissions at 500 nm and 572 nm decreased in different degrees. Dual-emission intensity ratio (I572/I500) increased linearly with fructose concentration in the range from 0.015 to 2.5 mM (R2 = 0.9945) (Fig. 5B). Limit of detection (LOD) was calculated as 0.005 mM (S/N = 3). 3.5. Fructose Detection in Food HBQ-PDBA was used for fructose detection in food samples including honey, fruit juice, carbonated drink and energy drink, and
Fig. 4. Response of HBQ-PDBA to different sugars (1.0 mM). HBQ concentration: 50 μM, PDBA concentration: 50 μM, solvent: 10 mM PBS buffer/DMSO (4:1, v/v), pH: 7.4, incubation time: 10 min, temperature: 37 °C.
202
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
Fig. 5. (A) Fluorescence spectra of HBQ-PDBA after adding different concentrations of fructose (0, 0.015, 0.060, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 1.0, 1.5, 2.0, 2.5 mM). (B) Linear correlation between dual-emission intensity ratio (I572/I500) and fructose concentration (0.015–2.5 mM). HBQ concentration: 50 μM, PDBA concentration: 50 μM, solvent: 10 mM PBS buffer/DMSO (4:1, v/v), pH: 7.4, incubation time: 10 min, temperature: 37 °C.
Table 1 Results of fructose detection in food samples.
and lower LOD. Accordingly, HBQ-PDBA exhibited the merits of simplicity, inexpensiveness and sensitivity.
Sample
[Fructose] (mM) Resorcinol method
[Fructose] (mM) This method
Honey Apple juice Cola Energy drink
3974.1 ± 182.9 478.7 ± 51.9 351.6 ± 21.7 167.0 ± 19.5
3655.6 ± 48.5 503.7 ± 32.0 326.9 ± 11.9 144.2 ± 7.8
experimental condition resulted in hydrolysis of disaccharide and polysaccharide in food samples. Table 2 presents comparison between HBQ-PDBA and reported fructose sensors [8,10–13,16,20–23] in terms of preparation step, linear range, LOD and real sample. Compared with the same type of sensors using ratiometric fluorescent method [16,20–22], HBQ-PDBA required no synthesis as HBQ and PDBA were commercial available with low cost, thereby it was simpler and more inexpensive. Compared with other types of sensors, such as fluorometry [10,11,23], electrochemistry [8] and colorimetry [12,13], HBQ-PDBA possessed less preparation steps
4. Conclusion A fluorescent fructose sensor based on complexation of HBQ with PDBA was reported. Compared with reported fructose sensors, it exhibited three advantages: (i) requiring no synthesis, it was simple and inexpensive; (ii) it as a ratiometric sensor was stable; (iii) it was sensitive with low LOD. This work provides a simple and inexpensive sensing platform for stable and sensitive detection of fructose. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (No. 21375052 and 21575055). Appendix A. Supplementary Data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.saa.2017.03.017.
Table 2 Comparison between HBQ-PDBA and reported fructose sensors. Sensor
Preparation step
Linear range (mM)
LOD (mM)
Real sample
Reference
5-DMANBAa C1-APBb and β-cyclodextrin Amphiphilic dipeptide bearing pyrene and boronic acid Polymer containing GS-MAc and Rhod-MAd Phenylboronic acid modified acrylic polymer HPTSe and m-P3BQf Fluorene-based fluorescent boronic acid FDHg modified SPFCEh APBi and GTEj modified AuNPs Self-assembled block copolymer photonic crystal HBQ-PDBA
4 1 8 9 6 1 6 1 4 2 −
− 0–10 0–2.5 0–5 0–10 0–100 0.025–0.4 0.1–1 2.8–33.3 − 0.015–2.5
− − − − 0.4 − 0.013 0.05 1.7 1 0.005
− − − − − − − Food Semen − Food
[20] [21] [16] [22] [10] [11] [23] [8] [12] [13] This work
a b c d e f g h i j
5-(Dimethylamino)naphthalene-1-boronic acid. 2-(4-Phenylboronic acid)-1-pyrenemethamide. Monomer containing boronic acid-based fructose sensor. Monomer containing rhodamine. 8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt. 1,3-Bis(pyridyl-3-boronic acid)benzyl quaternary ammonium dibromide. Fructose dehydrogenase. Screen-printed ferrocyanide/carbon electrode. 3-Aminophenyl boronic acid. L-Glutamic acid-(2,2,2)-trichloroethyl ester.
H. Li et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 180 (2017) 199–203
References [1] C.M.M.R. Barros, R.Q. Lessa, M.P. Grechi, T.L.M. Mouco, M.D.C. Souza, N. Wiernsperger, E. Bouskela, Substitution of drinking water by fructose solution induces hyperinsulinemia and hyperglycemia in hamsters, Clinics 62 (2007) 327–334. [2] G.A. Bray, S.J. Nielsen, B.M. Popkin, Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity, Am. J. Clin. Nutr. 79 (2004) 537–543. [3] M. Heinig, R.J. Johnson, Role of uric acid in hypertension, renal disease, and metabolic syndrome, Cleve. Clin. J. Med. 73 (2006) 1059–1064. [4] T. Nakagawa, K.R. Tuttle, R.A. Short, R.J. Johnson, Hypothesis: fructose-induced hyperuricemia as a causal mechanism for the epidemic of the metabolic syndrome, Nat. Clin. Pract. Nephrol. 1 (2005) 80–86. [5] T. Nakagawa, H.B. Hu, S. Zharikov, K.R. Tuttle, R.A. Short, O. Glushakova, X. Ouyang, D.I. Feig, E.R. Block, J. Herrera-Acosta, J.M. Patel, R.J. Johnson, A causal role for uric acid in fructose-induced metabolic syndrome, Am. J. Physiol. Ren. Physiol. 290 (2006) F625–F631. [6] P.N. Wahjudi, M.E. Patterson, S. Lim, J.K. Yee, C.S. Mao, W.N.P. Lee, Measurement of glucose and fructose in clinical samples using gas chromatography/mass spectrometry, Clin. Biochem. 43 (2010) 198–207. [7] C.M. Ma, Z. Sun, C.B. Chen, L.L. Zhang, S.H. Zhu, Simultaneous separation and determination of fructose, sorbitol, glucose and sucrose in fruits by HPLC-ELSD, Food Chem. 145 (2014) 784–788. [8] J. Biscay, E.C. Rama, M.B.G. Garcia, A.J. Reviejo, J.M.P. Carrazon, A.C. Gacia, Amperometric fructose sensor based on ferrocyanide modified screen-printed carbon electrode, Talanta 88 (2012) 432–438. [9] J.L. Montanez-Soto, S. Alegret, J.A. Salazar-Montoya, E.G. Ramos-Ramirez, A new amperometric biosensor for fructose determination based on epoxy-graphite-TTFTCNQ-FDH-biocomposite, Eur. Food Res. Technol. 223 (2006) 379–386. [10] J.L. Pablos, S. Vallejos, S. Ibeas, A. Munoz, F. Serna, F.C. Garcia, J.M. Garcia, Acrylic polymers with pendant phenylboronic acid moieties as “ turn-off” and “ turn-on” fluorescence solid sensors for detection of dopamine, glucose, and fructose in water, ACS Macro Lett. 4 (2015) 979–983. [11] L.H. Feng, F. Liang, Y. Wang, X.J. Wang, A facile sensor for D-fructose with fluorescence “on–off–on” switch ensemble, Sensors Actuators B 173 (2012) 575–579.
203
[12] V. Raj, A.N. Vijayan, K. Joseph, Naked eye detection of infertility using fructose blue—a novel gold nanoparticle based fructose sensor, Biosens. Bioelectron. 54 (2014) 171–174. [13] O.B. Ayyub, M.B. Ibrahim, R.M. Briber, P. Kofinas, Self-assembled block copolymer photonic crystal for selective fructose detection, Biosens. Bioelectron. 46 (2013) 124–129. [14] Z.J. Wang, H.Y. Lei, C.Y. Zhou, G.F. Wang, L.H. Feng, Highly selective ensembles for Dfructose based on fluorescent method in aqueous solution, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 91 (2012) 178–183. [15] D. Oesch, N.W. Luedtke, Fluorescent chemosensors of carbohydrate triols exhibiting TICT emissions, Chem. Commun. 51 (2015) 12641–12644. [16] L.N. Neupane, S.Y. Han, K.H. Lee, Ratiometric fluorescence sensing of sugars via a reversible disassembly and assembly of the peptide aggregates mediated by sugars, Chem. Commun. 50 (2014) 5854–5857. [17] M.R. Aronoff, B. VanVeller, R.T. Raines, Detection of boronic acids through excitedstate intramolecular proton-transfer fluorescence, Org. Lett. 15 (2013) 5382–5385. [18] D.J. Li, Q.J. Li, S.S. Wang, J. Ye, H.Y. Nie, Z. Liu, Pyridinylboronic acid-functionalized organic-silica hybrid monolithic capillary for the selective enrichment and separation of cis-diol-containing biomolecules at acidic pH, J. Chromatogr. A 1339 (2014) 103–109. [19] Y. Liu, C.M. Deng, L. Tang, A.J. Qin, R.R. Hu, J.Z. Sun, B.Z. Tang, Specific detection of Dglucose by a tetraphenylethene-based fluorescent sensor, J. Am. Chem. Soc. 133 (2011) 660–663. [20] X.M. Gao, Y.L. Zhang, B.H. Wang, Naphthalene-based water-soluble fluorescent boronic acid isomers suitable for ratiometric and off-on sensing of saccharides at physiological pH, New J. Chem. 29 (2005) 579–586. [21] R. Ozawa, T. Hashimoto, A. Yamauchi, I. Suzuki, B.D. Smith, T. Hayashita, Effect of cyclodextrins on saccharide sensing function of a fluorescent phenylboronic acid in water, Anal. Sci. 24 (2008) 207–212. [22] L.Q. Zhang, F.Y. Su, S. Buizer, X.X. Kong, F. Lee, K. Day, Y.Q. Tian, D.R. Meldrum, A polymer-based ratiometric intracellular glucose sensor, Chem. Commun. 50 (2014) 6920–6922. [23] R. Hosseinzadeh, M. Mohadjerani, M. Pooryousef, A. Eslami, S. Emami, A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 144 (2015) 53–60.