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A boronic acid-based fluorescent hydrogel for monosaccharide detection

  • Suying Xu 1,2 ,
  • Adam C. Sedgwick 2,3 ,
  • Souad A. Elfeky 2,4,5,6 ,
  • Wenbo Chen 2,4,7 ,
  • Ashley S. Jones 2 ,
  • George T. Williams 2 ,
  • A. Toby A. Jenkins 2 ,
  • Steven D. Bull 2 ,
  • John S. Fossey , 4 ,
  • Tony D. James , 2
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  • 1. Department of Biochemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, China
  • 2. Department of Chemistry, University of Bath, Bath BA2 7AY, UK
  • 3. Department of Chemistry, University of Texas at Austin, TX 78712-1224, USA
  • 4. School of Chemistry, University of Birmingham, Birmingham B15 2TT, UK
  • 5. National Institute of Laser Enhanced Sciences, Cairo University, Giza 12613, Egypt
  • 6. Higher Institute for Optics Technology, Sheraton, Cairo 17361, Egypt
  • 7. Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, Shanghai University of Electric Power, Shanghai 200090, China

Received date: 10 Oct 2018

Accepted date: 06 Jan 2019

Published date: 15 Feb 2020

Copyright

2019 The Author(s) 2019. This article is published with open access at link.springer.com and journal.hep.com.cn

Abstract

A boronic acid-based anthracene fluorescent probe was functionalised with an acrylamide unit to incorporate into a hydrogel system for monosaccharide detection. In solution, the fluorescent probe displayed a strong fluorescence turn-on response upon exposure to fructose, and an expected trend in apparent binding constants, as judged by a fluorescence response where D-fructose>D-galactose>D-mannose>D-glucose. The hydrogel incorporating the boronic acid monomer demonstrated the ability to detect monosaccharides by fluorescence with the same overall trend as the monomer in solution with the addition of D-fructose resulting in a 10-fold enhancement (≤0.25 mol/L).

Cite this article

Suying Xu , Adam C. Sedgwick , Souad A. Elfeky , Wenbo Chen , Ashley S. Jones , George T. Williams , A. Toby A. Jenkins , Steven D. Bull , John S. Fossey , Tony D. James . A boronic acid-based fluorescent hydrogel for monosaccharide detection[J]. Frontiers of Chemical Science and Engineering, 2020 , 14(1) : 112 -116 . DOI: 10.1007/s11705-019-1812-5

Introduction

Monosaccharides are among the basic building blocks of life and play an essential role in the function of several physiological processes, including metabolism and cellular recognition [1]. The monosaccharide glucose serves as the main form of energy for tissues and cells [2]. Due to their biological importance, there has been extensive effort in the development of methods and techniques for monosaccharide detection [34].
Lorand and Edwards reported the ability of boronic acids to form complexes with 1,2- and 1,3- diols. In addition it was discovered that D-fructose formed a 1:1 fructose-boronic acid complex and D-glucose formed a 1:2 glucose-boronic acid complex [5]. The strength of the boronic acid binding to monosaccharides is determined by the orientation and relative position of hydroxyl groups. In aqueous solution fructose predominates in the furanose form with a syn-periplanar pair of hydroxyl groups resulting in a strong binding constant with boronic acids [4]. As a result, a number of aryl boronic acid-based sensors have been developed for the detection of monosaccharides which exploit the difference in binding stoichiometry and inherent binding affinity to achieve either D-fructose or D-glucose selectivity [4,68]. More specifically, in 1994, James et al. developed an anthracene-containing mono boronic acid derivative as a photoinduced electron transfer (PET) fluorescence probe for the detection of fructose (Fig. 1) [9]. In this system, it was discovered that ortho-aminomethylphenylboronic acid functionality facilitated the detection of fructose in neutral aqueous solution. This pioneering work has led to the development of other ortho-aminomethylphenylboronic acid-containing fluorescence sensors improving selectivity, increasing excitation/emission profile and binding affinities [1012]. While there was never any doubt that the ortho-aminomethylphenylboronic acid group was important to improve saccharide binding at neutral pH the mechanism of action had been under debate for a number of years [1315]. Recently, the debate was concluded and the fluorescence enhancement on saccharide binding is caused by modulation of internal conversion resulting in different levels of quenching. Initially, before saccharide binding the free -B(OH)2 groups quench the fluorescence by internal conversion, then when saccharides bind the -B(OR)2 groups formed have reduced internal conversion and less quenching resulting in an enhanced fluorescence [16].
Fig.1 Shinkai et al. anthracene-based boronic acid PET fluorescence probe for the detection of fructose

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The saccharide-binding properties of aryl boronic acid derivatives have been exploited as recognition motifs across a number of different domains including polymer hydrogels [6,17,18]. Hydrogels are three dimensionally cross-linked hydrophilic polymers, with a high (~90 wt-%) water content [19]. The modification of hydrogels to contain boronic-acid binding motifs enables the physical properties of the hydrogel to be reversibly modulated through exposure to saccharide-containing stimuli, i.e., glucose responsivity [2023]. Co-authors of this report have developed stimuli responsive hydrogels and fluorescent sensors [2430], and as a result, we were motivated to translate a Shinkai-like anthracene-containing boronic acid sensor unit into a hydrogel sensor by linking to an acrylamide functionality, thus generating a fluorescence-on sensor hydrogel for monosaccharide detection.

Results and discussion

Whilst solution-based fluorescent sensors offer a significant advantage in terms of binding-kinetics over analogous heterogenous sensors [31]. Heterogenous immobilisation of a fluorescent sensor is preferential as it avoids contamination of the sensor in a practical situtation, i.e., in vivo [32,33]. The near-solvated nature of a hydrogel is thus an attractive alternative as they offer heterogeneity without the disadvantages associated with a solution-based system. By integrating the Shinkai et al. anthracene PET fluorescent probe into a hydrogel, we hoped to develop a fluorescence responsive boronic acid hydrogel, which could eliminate the need for an additional competitive optical reporter [33]. The desired boronic acid monomer AM-5 is shown below in Fig. 2.
Fig.2 Anthracene-based fluorescent monomer (A-M5) for the development of a hydrogel for the detection of monosacharides

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AM-5 was synthesised over five steps (Scheme 1). In brief, 1,6- hexanediamine was mono-Boc protected through the dropwise addition of di-tert-butyl dicarbonate ((Boc)2O) to an excess of 1,6-hexanediamine, which afforded tert-butyl (6-aminohexyl)carbamate (1) in 74% yield. To attach the desired anthracene fluorophore, 1 was stirred with anthracene-9-carbaldehyde at room temperature overnight to form an imine intermediate. NaBH4 was then added portion-wise to produce the desired secondary amine tert-butyl (6-((anthracen-9-ylmethyl)amino)hexyl)carbamate (2) in reasonable yield (48%). Compound 2 was subsequently alkylated with 2-bromomethylphenylboronic acid pinacol ester to afford 3 in good yield (89%). Compound 3 was then Boc-deprotected using trifluoroacetic acid, which also resulted in the partial hydrolysis of the boronate ester to form boronic acid 4, this intermediate was taken onto the next step without purification. Methacryloyl chloride was then used to afford AM-5, which was confirmed by mass spectrometry. Compound AM-5 proved difficult to characterise by NMR techniques and exhibited a broad and complex 1H NMR due to the formation of “oligomeric boronic acid anhydrides” [3435].
Fig.3 Scheme 1 Synthesis of boronic acid fluorescent probes 3 and AM-5

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With 3 in hand, the fluorescence properties and responses to a panel of monosaccharides were evaluated to demonstrate its sensing ability before incorporation into a hydrogel. As shown in Fig. 3(b), 3 was more sensitive towards fructose over other monosaccharides (as expected) and the binding stability constants between mono-boronic acids and saccharides followed: D-fructose>D-galactose>D-mannose>D-glucose (Table S1, cf. Electronic Supplementary Material (ESM)). From these results, we turned our attention towards the incorporation of 3 into a hydrogel.
Fig.4 (a) Fluorescent spectral changes of 3 (0.6 µmol/L) with different concentrations of D-fructose in pH 8.21 aqueous methanolic buffer solution (52.1 wt-% methanol (KCl, 10 mmol/L; KH2PO4, 2.73 mmol/L and Na2HPO4, 2.78 mmol/L)); (b) Fluorescence intensity changes (F/F0) at 419 nm versus increasing saccharide concentration. lex = 370 nm

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Hydrogels containing AM-5 were formed by co-polymerisation of acrylamide and methylene bisacrylamide in water through free radical polymerisation using ammonium persulfate (APS) and tetramethylethylenediamine (TMEDA) (cf. ESM for full detailed procedure). For the evaluation of the fluorescence response of the hydrogel towards different monosaccharides, each hydrogel was placed into a monosaccharide solution for 2 h (Note: 2 h was chosen since at this time point no further increase in fluorescence intensity was observed after addition of monosaccharides).
Acrylamide-based hydrogels consisting of AM-5 were exposed to increasing concentrations of fructose and a significant fluorescence enhancement was observed (~16-fold) as shown in Fig. 4, the selectivity order for the detection of monosaccharides was consistent with the solution titration data of 3 (Fig. 2, Table S1 and Table S2), D-fructose>D-galactose>D-mannose>D-glucose. However, the observed binding constants for each monosaccharide were much lower than in the solution phase, which is believed to be due to the binding event being a diffusion-based process ((1381.7±41.80) versus (52.6±5.3) dm3/mol for D-fructose). The response towards D-glucose in the hydrogel was too low for the binding constant to be determined.
Fig.5 Fluorescence intensity ratios of AM-5 (F/F0) at 409 nm versus monosaccharide concentration in a (1:1) 0.1 mol/L KH2PO4/0.1 mol/L NaOH, pH 8.00 buffer solution and λex = 370 nm

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Conclusions

A fluorescent monosaccharide responsive hydrogel was developed by functionalising the proven ortho-aminomethylphenylboronic acid anthracene PET sensor with an acrylamide unit to incorporate into a hydrogel backbone. The boronic acid-containing hydrogel produced a significant fluorescent enhancement (~16 fold) with the addition of fructose and the binding stability constants followed the well-established order for binding between mono-boronic acids and saccharides: D-fructose>D-galactose>D-mannose>D-glucose.

Acknowledgements

The University of Bath are thanked for support. ACS thanks the EPSRC for a PhD studentship. TDJ and JSF are grateful for the support of the EPSRC and DTI (DT/F00267X/1). Preliminary results of this project stemmed from another project pump-primed by the University of Bath Enterprise Development Fund (EDF award to investigators including JSF, ATAJ and TDJ). TDJ wishes to thank the Royal Society for a Wolfson Research Merit Award. JSF and WC thanks the Leverhulme Trust for support (F00094BC). JSF thanks the JDRF (2-SRA-2016-267-A-N) for support. Spectroscopy facilities were provided through the Material and Chemical Characterisation Facility (MC2) at the University of Bath. The investigators are grateful to the CASE consortium for providing knowledge transfer and networking opportunities [36,37].

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-019-1812-5 and is accessible for authorized users.
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1
Levine R. Monosaccharides in health and disease. Annual Review of Nutrition, 1986, 6(1): 211–224

DOI

2
Mergenthaler P, Lindauer U, Dienel G A, Meisel A. Sugar for the brain: The role of glucose in physiological and pathological brain function. Trends in Neurosciences, 2013, 36(10): 587–597

DOI

3
Pickup J C, Hussain F, Evans N D, Rolinski O J, Birch D J S. Fluorescence-based glucose sensors. Biosensors & Bioelectronics, 2005, 20(12): 2555–2565

DOI

4
Wu X, Li Z, Chen X X, Fossey J S, James T D, Jiang Y B. Selective sensing of saccharides using simple boronic acids and their aggregates. Chemical Society Reviews, 2013, 42(20): 8032–8048

DOI

5
Lorand J P, Edwards J O. Polyol complex and structure of the benzene boronate ion. Journal of Organic Chemistry, 1959, 24(6): 769–774

DOI

6
Sun X, James T D. Glucose sensing in supramolecular chemistry. Chemical Reviews, 2015, 115(15): 8001–8037

DOI

7
Huang Y J, Ouyang W J, Wu X, Li Z, Fossey J S, James T D, Jiang Y B. Glucose sensing via aggregation and the use of “knock-out” binding to improve selectivity. Journal of the American Chemical Society, 2013, 135(5): 1700–1703

DOI

8
Cao H S, Heagy M D. Fluorescent chemosensors for carbohydrates: A decade’s worth of bright spies for saccharides in review. Journal of Fluorescence, 2004, 14(5): 569–584

DOI

9
James T D, Sandanayake K, Shinkai S. Novel photoinduced electron-transfer sensor for saccharides based on the interaction of boronic acid and amine. Journal of the Chemical Society. Chemical Communications, 1994, 0(4): 477–478

DOI

10
Zhang X T, Liu G J, Ning Z W, Xing G W. Boronic acid-based chemical sensors for saccharides. Carbohydrate Research, 2017, 452: 129–148

DOI

11
James T D, Sandanayake K R A S, Shinkai S. A glucose-selective molecular fluorescence sensor. Angewvandte Chemie International Edition, 1994, 33: 2207–2209

12
James T D, Sandanayake K R A S, Iguchi R, Shinkai S. Novel saccharide-photoinduced electron transfer sensors based on the interaction of boronic acid and amine. Journal of the American Chemical Society, 1995, 117(35): 8982–8987

DOI

13
Franzen S, Ni W, Wang B. Study of the mechanism of electron-transfer quenching by boron-nitrogen adducts in fluorescent sensors. Journal of Physical Chemistry B, 2003, 107(47): 12942–12948

DOI

14
Ni W, Kaur G, Springsteen G, Wang B, Franzen S. Regulating the fluorescence intensity of an anthracene boronic acid system: A B–N bond or a hydrolysis mechanism? Bioorganic Chemistry, 2004, 32(6): 571–581

DOI

15
Chapin B M, Metola P, Vankayala S L, Woodcock H L, Mooibroek T J, Lynch V M, Larkin J D, Anslyn E V. Disaggregation is a mechanism for emission turn-on of ortho-aminomethylphenylboronic acid-based saccharide sensors. Journal of the American Chemical Society, 2017, 139(15): 5568–5578

DOI

16
Sun X, James T D, Anslyn E V. Arresting “loose bolt” internal conversion from -B(OH)2 groups is the mechanism for emission turn-on in ortho-aminomethylphenylboronic acid-based saccharide sensors. Journal of the American Chemical Society, 2018, 140(6): 2348–2354

DOI

17
Zhao L, Huang Q W, Liu Y, Wang Q, Wang L Y, Xiao S S, Bi F, Ding J X. Boronic acid as glucose-sensitive agent regulates drug delivery for diabetes treatment. Materials, 2017, 10 (2): 170

18
Guan Y, Zhang Y J. Boronic acid-containing hydrogels: Synthesis and their applications. Chemical Society Reviews, 2013, 42(20): 8106–8121

DOI

19
Ahmed E M. Hydrogel: Preparation, characterization, and applications: A review. Journal of Advanced Research, 2015, 6(2): 105–121

DOI

20
Li Y Y, Zhou S Q. A simple method to fabricate fluorescent glucose sensor based on dye-complexed microgels. Sensors and Actuators. B, Chemical, 2013, 177: 792–799

DOI

21
Matsumoto A, Tanaka M, Matsumoto H, Ochi K, Moro-oka Y, Kuwata H, Yamada H, Shirakawa I, Miyazawa T, Ishii H. Synthetic “smart gel” provides glucose-responsive insulin delivery in diabetic mice. Science Advances, 2017, 3, eaaq0723

22
Matsumoto A, Kataoka K, Miyahara Y. New directions in the design of phenylboronate-functionalized polymers for diagnostic and therapeutic applications. Polymer Journal, 2014, 46(8): 483–491

DOI

23
Sanjoh M, Miyahara Y, Kataoka K, Matsumoto A. Phenylboronic acids-based diagnostic and therapeutic applications. Analytical Sciences, 2014, 30(1): 111–117

DOI

24
Sedgwick A C, Chapman R S L, Gardiner J E, Peacock L R, Kim G, Yoon J, Bull S D, James T D. A bodipy based hydroxylamine sensor. Chemical Communications, 2017, 53(75): 10441–10443

DOI

25
Sedgwick A C, Sun X L, Kim G, Yoon J, Bull S D, James T D. Boronate based fluorescence (ESIPT) probe for peroxynitrite. Chemical Communications, 2016, 52(83): 12350–12352

DOI

26
Sun X L, Odyniec M L, Sedgwick A C, Lacina K, Xu S Y, Qiang T T, Bull S D, Marken F, James T D. Reaction-based indicator displacement assay (RIA) for the colorimetric and fluorometric detection of hydrogen peroxide. Organic Chemistry Frontiers: An International Journal of Organic Chemistry, 2017, 4(6): 1058–1062

DOI

27
Sedgwick A C, Han H H, Gardiner J E, Bull S D, He X P, James T D. Long-wavelength fluorescent boronate probes for the detection and intracellular imaging of peroxynitrite. Chemical Communications, 2017, 53(95): 12822–12825

DOI

28
Wu D, Sedgwick A C, Gunnlaugsson T, Akkaya E U, Yoon J, James T D. Fluorescent chemosensors: The past, present and future. Chemical Society Reviews, 2017, 46(23): 7105–7123

DOI

29
Sedgwick A C, Han H H, Gardiner J E, Bull S D, He X P, James T D. The development of a novel AND logic based fluorescence probe for the detection of peroxynitrite and GSH. Chemical Science (Cambridge), 2018, 9(15): 3672–3676

DOI

30
Lampard E V, Sedgwick A C, Sombuttan T, Williams G T, Wannalerse B, Jenkins A T A, Bull S D, James T D. Dye displacement assay for saccharides using benzoxaborole hydrogels. ChemistryOpen, 2018, 7(3): 266–268

DOI

31
Kreisig T, Hoffmann R, Zuchner T. Homogeneous fluorescence-based immunoassay detects antigens within 90 seconds. Analytical Chemistry, 2011, 83(11): 4281–4287

DOI

32
Grabchev I, Qian X H, Xiao Y, Zhang R. Novel heterogeneous PET fluorescent sensors selective for transition metal ions or protons: Polymers regularly labelled with naphthalimide. New Journal of Chemistry, 2002, 26(7): 920–925

DOI

33
Basabe-Desmonts L, Reinhoudt D N, Crego-Calama M. Design of fluorescent materials for chemical sensing. Chemical Society Reviews, 2007, 36(6): 993–1017

DOI

34
Li M, Liu Z J, Wang H C, Sedgwick A C, Gardiner J E, Bull S D, Xiao H N, James T D. Dual-function cellulose composites for fluorescence detection and removal of fluoride. Dyes and Pigments, 2018, 149: 669–675

DOI

35
Hall D G. Boronic acids: Preparation and applications in organic synthesis, medicine and materials.Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA, 2005, 1–550

36
Fossey J S, Brittain W D G. The CASE 2014 symposium: Catalysis and sensing for our environment, Xiamen 7th‒9th November 2014. Organic Chemistry Frontiers: An International Journal of Organic Chemistry, 2015, 2(2): 101–105

DOI

37
Payne D T, Fossey J S, Elmes R B P. Catalysis and Sensing for our Environment (CASE2015) and the Supramolecular Chemistry Ireland Meeting (SCI 2015): Dublin and Maynooth, Ireland. 8th‒11th July. Supramolecular Chemistry, 2016, 28(11-12): 921–931

DOI

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