A newly synthesized boronic acid-functionalized sulfur-doped carbon dot chemosensor as a molecular probe for glucose sensing

https://doi.org/10.1016/j.microc.2021.105919Get rights and content

Highlights

  • Synthetization of newly boronic acid-CDs in one step.

  • Effect of variables such as pH, incubation time and several organic and inorganic as interferences were studied.

  • A highly luminescence CDs was obtained with less than 10 nm in size and highly quantum yield 22.65%.

  • Glucose in saliva sample was detected via the static quenching mechanism of fluorescent light.

Abstract

The drawbacks of using an enzymatic assay as a traditional protocol for glucose include cost, time consumption, instability, and denaturation of glucose oxidase. Recently, glucose sensing with the aid of boronic acid-based molecules and their derivatives has been developed as an alternative tool to commonly used methods. In this work, a simple single-step hydrothermal method was effectively applied to synthetized boronic acid-functionalized sulfur-doped carbon nanodots (BS-CDs) using 3-thiophenylboronic acid as the starting material. In comparison with the common two-step synthetization of nanoparticle-based sensors, this synthesis procedure is less demanding and equally as effective in terms of nanofabrication and quantum yield 22.63%. The present sensing method arises from the assembly and fluorescence quenching of fluorescence nanoparticles (BS-CDs) when the glucose solution was added. The fluorescence intensity was recorded and applied to selectively estimate glucose in the concentration range of 1–250 μM with a detection limit of 0.57 μM. Fluorescence nanoparticles with boronic acid had excellent selectivity and strongly resisted interference from several biomolecules. The developed chemosensor was successfully applied in the measurement of glucose in human saliva.

Introduction

The principle source of energy in cellular metabolism is glucose, which plays a critical role in normal cell growth. Cellular functions are dangerously affected by the lack or excessive intake of glucose [1]. The World Health Organization (WHO) has illustrated that diabetes causes heart infections, kidney failure and intense immune disorders and has predicted that diabetes will be the 7th leading cause of death in the 2030s [2]. The most important step in treating diabetes is to control blood sugar levels [3]. Thus, a daily blood glucose level check and detection are essential for diabetes care and a necessary part of disease therapy [4]. Constant monitoring of glucose levels in the blood instructs the patient to know the amount of insulin to be injected according to the level of severity of the disease [5], [6], [7].

The enzyme immobilization strategy for glucose sensing is still a widely utilized method, although it suffers some challenges, including enzyme denaturation, thermal instability, and high variation of results caused by the oxygen concentration in the blood [8], [9], [10], [11]. With the increased incidence rate of diabetes, it is important to develop appropriate methods for glucose estimation in terms of cost, speed, efficiency, easy, stability and availability. This situation has encouraged researchers to seek and develop a nonenzymatic-based sensor. New substances and methods not only significantly improve the categories of glucose sensor probes but also efficiently reduce the uncertainty of enzyme-based sensors [12].

Detection of an analyte in the blood usually suffers from some limitations; therefore, great attention has been paid to the use of other biologic fluids for disease diagnosis. Saliva is a fluid that offers several considerable advantages, including ease of sample collection without hurting the person, lack of need of specialized tools, economic favourability, and potential value for children and older adults since the collection of saliva is associated with fewer compliance problems than the collection of blood [13].

Monosaccharide molecules can be detected sensitively and selectively by boronic acid organic compound derivatives as they can covalently bind to a cis-diol fraction in a basic medium. The formation of the cis-diol structure complex depends on the thermodynamic characteristics of the boronic acid derivatives [14]. Boronic acid derivatives provide a beneficial method for the development of sensing probes for monosaccharaides [15], [16]. The conjugation of boronic acid to any fluorophore causes significant fluorescence intensity changes upon binding to glucose in the form of changes in quenching time, intensity, and polarization [17], [18], [19], [20]. Recently, researchers have given attention to carbon nanodots, which are novel members of the carbon nanofamily, mainly due to their strong fluorescence, tunable excitation and emission, water solubility, attractive photostability, and biocompatibility characteristics [21], [22], [23], [24], [25], [26]. Carbon nanodots are encouraging candidates in sensing [27], [28], [29], [30], [31], [32], catalysis [33], [34], bioimaging [35], [36], [37] and light-emitting devices [38]. Moreover, carbon nanodots can easily be prepared via numerous simple, green, and low-cost procedures and are appropriate for various biosensing applications [39].

In this study, we describe an easy nonenzymatic fabrication strategy for sensing glucose in saliva. The chemosensor for this particular study was designed using a single-step synthesis procedure of boron, sulfur-doped carbon dots BS-CDs. 3-thiophenylboronic acid was chosen as the precursor due to its great harmony towards the π-electron cloud-rich carbon dot core. More emissive sites with strong selectivity for glucose sensing were created after functionalization of the sulfur-doped carbon dots with boronic acid due to the interaction between boronic acids and the cis-diol-group of glucose (Fig. 1) [40], [41]. This fluorescence nanosensing method was sensitive, making it possible to differentiate glucose completely from both its analogue and other potential saliva interferences. No costly enzymes or complicated methods for modifying the surface are required. The fabricated chemosensor has a strong ability to measure glucose levels in saliva.

Section snippets

Materials

3-Thiophenylboronic acid (95%), Glucose, fructose, sucrose, lactose, and glutathione were purchased from Sigma-Aldrich. All reagents were of analytical grade and used without further purification, and deionized water was used throughout the experiments.

Instruments

Absorbance spectra were recorded using a Lambda 25-UV–Vis spectrophotometer (PerkinElmer, US). Fluorescence measurements were carried out by a Perkin Elmer LS- 45 fluorescence spectrometer (Buckinghamshire, UK). Characterization of the

Characterization of BS-CDs

The size and morphology of the synthesized BS-CDs were observed using HR-TEM. The image showed that the BS-CDs were well dispersed and spherical, with an average diameter of 4.5 nm and a lattice spacing distance of 0.23 nm. The lattice spacing explain both crystalline graphite and amorphous phases, which agrees with that of in-plane lattice spacing of graphene (1 0 0). The standard deviation was 1.05 and the number of nanoparticles that used was 100 [46], [47] (Fig. 2a) while the inset graph

Conclusion

A new boron-sulfur-doped carbon dot chemosensor was fabricated and developed for glucose detection in saliva samples via the static quenching mechanism of fluorescent light. Additionally, one of the known limitations of glucose sensing procedures is the usually low LOD, which do not allow its use for blood glucose direct sensing. To compensate for this limitation we propose this sensing methodology for the analysis of glucose in saliva where the concentration of glucose is much higher. The

Funding

No funding was received for this work.

Intellectual property

We confirm that we have given due consideration to the protection of intellectual property associated with this work and that there are no impediments to publication, including the timing of publication, with respect to intellectual property. In so doing we confirm that we have followed the regulations of our institutions concerning intellectual property.

Research ethics

  • We further confirm that any aspect of the work covered in this manuscript that has involved human patients has been conducted with the ethical approval of all relevant bodies and that such approvals are acknowledged within the manuscript.

  • IRB approval was obtained (required for studies and series of 3 or more cases.

  • Written consent to publish potentially identifying information, such as details or the case, was obtained from the patient(s) or their legal guardian(s).

Authorship

The International Committee of Medical Journal Editors (ICMJE) recommends that authorship be based on the following four criteria:

1. Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND

2. Drafting the work or revising it critically for important intellectual content; AND

3. Final approval of the version to be published; AND

4. Agreement to be accountable for all aspects of the work in ensuring that questions

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (74)

  • S. Hamd-Ghadareh et al.

    Simultaneous biosensing of CA125 and CA15-3 tumor markers and imaging of OVCAR-3 and MCF-7 cells lines via bi-color FRET phenomenon using dual blue-green luminescent carbon dots with single excitation wavelength

    Int. J. Biol. Macromol.

    (2018)
  • Y. Shi et al.

    Synthesis of N-doped carbon quantum dots from bio-waste lignin for selective irons detection and cellular imaging

    Int. J. Biol. Macromol.

    (2019)
  • P. Das et al.

    A simplistic approach to green future with eco-friendly luminescent carbon dots and their application to fluorescent nano-sensor ‘turn-off’ probe for selective sensing of copper ions

    Mater. Sci. Eng., C

    (2017)
  • P. Das et al.

    Heteroatom doped photoluminescent carbon dots for sensitive detection of acetone in human fluids

    Sens. Actuators, B

    (2018)
  • P. Das et al.

    Zinc and nitrogen ornamented bluish white luminescent carbon dots for engrossing bacteriostatic activity and Fenton based bio-sensor

    Mater. Sci. Eng., C

    (2018)
  • T. Sarkar et al.

    Carbon dots-modified chitosan based electrochemical biosensing platform for detection of vitamin D

    Int. J. Biol. Macromol.

    (2018)
  • R. Xie et al.

    Construction of up-converting fluorescent carbon quantum dots/Bi20TiO32 composites with enhanced photocatalytic properties under visible light

    Chem. Eng. J.

    (2017)
  • B. Xue et al.

    Photoluminescent lignin hybridized carbon quantum dots composites for bioimaging applications

    Int. J. Biol. Macromol.

    (2019)
  • W. Zhang et al.

    Noninvasive glucose monitoring using saliva nano-biosensor

    Sens. Bio-Sens. Res.

    (2015)
  • P. Das et al.

    Biocompatible carbon dots derived from κ-carrageenan and phenyl boronic acid for dual modality sensing platform of sugar and its anti-diabetic drug release behavior

    Int. J. Biol. Macromol.

    (2019)
  • L.I. Bosch et al.

    Binary and ternary phenylboronic acid complexes with saccharides and Lewis bases

    Tetrahedron

    (2004)
  • M.H. Gehlen

    The centenary of the Stern-Volmer equation of fluorescence quenching: From the single line plot to the SV quenching map

    J. Photochem. Photobiol., C

    (2020)
  • G. Springsteen et al.

    A detailed examination of boronic acid–diol complexation

    Tetrahedron

    (2002)
  • Q. Liu et al.

    One-step synthesis of uniform nanoparticles of porphyrin functionalized ceria with promising peroxidase mimetics for H2O2 and glucose colorimetric detection

    Sens. Actuators, B

    (2017)
  • W.-S. Zou et al.

    A hybrid ratiometric probe for glucose detection based on synchronous responses to fluorescence quenching and resonance light scattering enhancement of boronic acid functionalized carbon dots

    Sens. Actuators, B

    (2018)
  • L.B. Hoeks et al.

    Real-time continuous glucose monitoring system for treatment of diabetes: a systematic review

    Diabet. Med.

    (2011)
  • The Diabetes Control and Complications Trial Research Group

    The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus

    New Engl. J. Med.

    (1993)
  • The UK Prospective Diabetes Study (UKPDS) Group

    Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33)

    Lancet

    (1998)
  • G.P.C. Mello et al.

    Glucose sensing by fluorescent nanomaterials

    Crit. Rev. Anal. Chem.

    (2019)
  • D. Li et al.

    Boronate affinity materials for separation and molecular recognition: structure, properties and applications

    Chem. Soc. Rev.

    (2015)
  • E. Kaufman et al.

    The diagnostic applications of saliva— a review

    Crit. Rev. Oral Biol. Med.

    (2002)
  • E. Shoji et al.

    Potentiometric saccharide detection based on the p Ka changes of poly(aniline boronic acid)

    J. Am. Chem. Soc.

    (2002)
  • S.D. Bull et al.

    Exploiting the reversible covalent bonding of boronic acids: recognition, sensing, and assembly

    Acc. Chem. Res.

    (2013)
  • X. Wu et al.

    Selective sensing of saccharides using simple boronic acids and their aggregates

    Chem. Soc. Rev.

    (2013)
  • H. Fang et al.

    Progress in boronic acid-based fluorescent glucose sensors

    J. Fluorescence

    (2004)
  • S. Baker et al.

    Luminescent carbon nanodots: emergent nanolights

    Angew. Chem. Int. Ed.

    (2010)
  • S. Kiran, R.D.K. Misra, Mechanism of intracellular detection of glucose through nonenzymatic and boronic acid...
  • Cited by (15)

    • New europium-doped carbon nanoparticles showing long-lifetime photoluminescence: Synthesis, characterization and application to the determination of tetracycline in waters

      2023, Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
      Citation Excerpt :

      These materials combine interesting properties such as photoluminescence, chemo- and photostability, high solubility in water, ease of synthesis, and surface functionalization with some biologically compelling properties like biodegradability, low toxicity, and scarce environmental impact [5-7]. Particularly, the unique optic and spectroscopic characteristics offered by these materials make them a powerful alternative in many applications such as optoelectronic labelling [8,9], bioimaging [6,10] or chemosensor development [11,12], among others. On the other hand, it is well known that photoluminescent complexes of lanthanoids have been widely used as fluorescent probes in technological and bioanalytical applications [13].

    • Current and future prospective of biosensing molecules for point-of-care sensors for diabetes biomarker

      2022, Sensors and Actuators B: Chemical
      Citation Excerpt :

      The system showed to measure glucose concentration ranging from 1 to 250 µM, with a detection limit of 0.57 µM. The sensor was then tested against several competing saccharides and interference demonstrating the specificity towards glucose and was demonstrated in vivo using human saliva [56]. Latif et al., developed a MIP based synthetic ligand for detection of glucose.

    View all citing articles on Scopus
    View full text