A high-performance electrochemical sensor for biologically meaningful l-cysteine based on a new nanostructured l-cysteine electrocatalyst
Graphical abstract
Introduction
l-cysteine (CySH) is an important amino acid present in natural proteins and also plays key roles in biological systems. For example, it could be used as a potential radiation protector and cancer indicator [1,2]. Therefore, the deficiency of CySH in a physiological sample provides insight into the diagnosis of the disease [3,4]. Consequently the determination of CySH is of paramount importance in physiological and clinical diagnosis [5,6]. In the past decades, many techniques have been developed to detect CySH, including flow injection, high performance liquid chromatography, spectrophotometry, colorimetry, gas chromatography, chemiluminescence, and mass spectrometry [[7], [8], [9], [10], [11], [12]]. However, their application is greatly limited due to the high cost, tedious procedures, and the requirement of skilled personnel. On the other hand, l-cysteine can be oxidized to form l-cystine (CyssyC), thus the couple of l-cysteine/l-cystine (CySH/CyssyC) have been widely applied as a model system to study the role of the disulfide bond and thiol group in proteins in a variety of biological media [13]. Accordingly it provides the possibility to electrochemically detect CySH if an appropriate electrocatalyst for CySH oxidation can be identified [[14], [15], [16], [17]]. Compared to aforementioned methods, the electrochemical sensor offers many potential advantages, such as cost effectiveness, high sensitivity, easy operation, miniaturization, and user friendliness [[18], [19], [20], [21], [22]].
To discover suitable electron transfer mediators for fast and low potential determination of CySH is critical and challenging in the pursuit of CySH electrochemical determination, since the direct oxidation of thiols at solid electrodes is typically slow and generally requires high over-potential [23]. A variety of substances including polymers [21,24], metal nanomaterials [18,20], carbon materials [25,26], and enzymes [27] have been explored for the electrochemical detection of CySH. Although those modifiers enhance the performance for the determination of CySH, there are still disadvantages, such as poor detection limit and sensitivity, narrow detection range, and/or high over-potential [28]. Therefore, to identify new sensing materials for electrochemical detection of biologically meaningful CySH has been a continuous effort, which has been recently shifted to widely used metal oxides (e.g. iron oxide, zinc oxide and manganese oxide, etc.) [26,[29], [30], [31], [32]], because of their easy accessibility, low cost, and good chemical and thermal stability.
CeO2 is one of the rare earth metal oxide materials which possesses many impressive properties, such as good oxygen ion conductivity, superior chemical and thermal stability, high specific capacitance and non-toxicity. More interestingly, the unique redox property of CeO2 enables dual oxidation states (Ce(IV)/Ce(III)) to co-exist in cerium oxide, thus acting as an ideal oxidant for biomolecules to trigger the reaction of Ce4+ + BioRed → Ce3+ + BioOx [33,34]. Accordingly, CeO2 based materials have been explored to electrochemically detect various molecules, such as acetaminophen, acetaldehyde, nitrobenzene, hydrogen peroxide, xanthine, hypoxanthine, uric acid, and dopamine [[35], [36], [37], [38], [39], [40], [41]]. Recently, CeO2 has been seminally explored in the development of a fluorescent sensor for CySH detection. In this fluorescence sensing scenario, CeO2 oxidizes CySH to form fluorescent Ce(III)-CyssyC complex through following reaction: 2Ce(IV) + 2CysH→ 2Ce(III) + CyssyC + 2H+ [34]. We hypothesize that in conjunction with electrochemistry, this reaction could be exploited for electrochemical determination of CySH with high performance. Moreover, due to the intrinsic strong interaction between Au with SH- group and electro-oxidation of CySH on Au, doping Au into CeO2 could result in an excellent electrocatalyst for CySH due to the synergistic effects of Au and CeO2 through the enrichment of CySH on the surface of catalyst and the enhanced electron transfer from doped Au. To the best of our knowledge, there is no report based on the application of Au/CeO2 for the determination of l-cysteine.
Therefore, our interest in this paper is to explore an electrochemical sensor toward CySH determination based on electrospun Au/CeO2 composite nanofibers (Au/CeO2 CNFs) modified screen printed carbon electrode (SPCE), in which Au/CeO2 CNFs were employed as a new class of CySH electrocatalyst. The results from electrochemical measurements demonstrated that the resulting Au/CeO2 CNFs possess highly enhanced electrocatalytic activity toward CySH oxidation, compared with pure CeO2 nanofibers. The as-prepared CySH electrochemical sensor showed an ultra-sensitivity of 321 μA mM−1 cm−2 (2.7 times higher than that of pure CeO2 nanofibers), which can be attributed to three factors: (1) the presence of Au effectively enhanced the conductivity of CeO2 NFs; (2) the enrichment of CySH on the surface of Au/CeO2 due to strong interaction between Au and CySH; and (3) the synergistic catalytic effect of Au and CeO2 on CySH oxidation. Moreover, a low detection limit of 10 nM (S/N = 3), a wide linear range up to 200 μM and an excellent selectivity have been obtained, which are among the best values reported in literature. All these features indicate that the Au/CeO2 composite nanofiber is a promising candidate as a new class of l-cysteine electrocatalyst in the development of highly sensitive and selective CySH electrochemical sensor.
Section snippets
Materials and methods
Cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O), hydrogen tetrachloroaurate trihydrate (HAuCl4·3H2O), ascorbic acid (AA), and uric acid (UA) were purchased from Acros Organics. l-cysteine, tryptophan (Trp), tyrosine (Tyr), methionine (Met), poly(vinyl pyrrolidone) (PVP, MW = 1,300,000), human serum (from male AB clotted whole blood) and Nafion® perfluorinated resin solution (20 wt% in lower aliphatic alcohols and water, contains 34% water) were obtained from Sigma–Aldrich. All aqueous solutions
Morphological and structure characterization of Au/CeO2 CNFs
The typical SEM morphology of the as-prepared Au/CeO2 CNFs was shown in Fig. 1b. It can be seen that the calcined Au/CeO2 displays a randomly orientated fiber structure with an average diameter of 100–200 nm. Such nanofibrous structure possesses large electroactive surface and many electron transport channels which are beneficial to electrocatalytic applications. As a comparison, pure CeO2 NFs show similar nanofibrous morphology (Fig. 1a), indicating that the doping of Au into CeO2 NFs has
Conclusions
In this contribution, a high-performance CySH electrochemical sensor was developed using a new class of CySH electrocatalyst (electrospun Au/CeO2 CNFs) modified screen printed three-electrode test strip. The as-prepared electrochemical sensor was investigated by cyclic voltammetry and amperometric techniques to evaluate its performance in electrochemical oxidation and determination of biologically meaningful CySH. Compared to the results from pure CeO2 nanofibers, the presence of Au in CeO2 NFs
Acknowledgement
F.C greatly appreciate the funding from Natural Science Foundation of Jiangsu Province of China (No.BK20150692), National Natural Science Foundation of China (No. U1537102). Y.L thanks the partial support from NSF and USGS and Y.K. Huang acknowledges the partial support from GE Fellowship.
References (53)
- et al.
Chemically modified electrodes for the determination of sulphydryl compounds
Anal. Chim. Acta
(1991) Electrochemical response of new carbon electrodes bulk modified with cobalt phthalocyanine to some thiols in the presence of heptane or human urine
Anal. Chim. Acta
(1999)- et al.
A very low potential electrochemical detection of L-cysteine based on a glassy carbon electrode modified with multi-walled carbon nanotubes/gold nanorods
Biosens. Bioelectron.
(2013) - et al.
Sensor for cysteine based on oxovanadium(IV) complex of Salen modified carbon paste electrode
Sens. Actuators. B
(2005) - et al.
Electrochemical behavior of l-cysteine and its detection at carbon nanotube electrode modified with platinum
Anal. Biochem.
(2005) - et al.
Fine steps of electrocatalytic oxidation and sensitive detection of some amino acids on copper nanoparticles
Anal. Biochem.
(2009) - et al.
Electrochemical determination of cysteine based on conducting polymers/gold nanoparticles hybrid nanocomposites
Electrochim. Acta
(2011) - et al.
Electrochemical detection of cysteine in a flow system based on reductive desorption of thiols from gold
Anal. Chim. Acta
(2006) - et al.
Electrochemical sensor for determination of L-cysteine based on carbon electrodes modified with Ru(III) schiff base complex, carbon nanotubes and nafion
Int. J. Electrochem. Sci.
(2016) - et al.
Nanostructured electropolymerized film of 5-amino-2-mercapto-1,3,4-thiadiazole on glassy carbon electrode for the selective determination of l-cysteine
Electrochem. Commun.
(2009)
Electrochemical determination of L-Tryptophan, L-Tyrosine and L-Cysteine using electrospun carbon nanofibers modified electrode
Talanta
Electrodeposition of guanine oxidation product onto zinc oxide nanoparticles: application to nanomolar detection of l-cysteine
Sens. Actuators B
Selective sensing of cysteine on manganese dioxide nanowires and chitosan modified glassy carbon electrodes
Biosens. Bioelectron.
An electrocatalytic transducer for l-cysteine detection based on cobalt hexacyanoferrate nanoparticles with a core–shell structure
Anal. Biochem.
A novel electrochemical sensor based on B doped CeO2 nanocubes modified glassy carbon microspheres paste electrode for individual and simultaneous determination of xanthine and hypoxanthine
Sens. Actuators B
Electrochemical determination of dopamine based on electrospun CeO2/Au composite nanofibers
Electrochim. Acta
Spectroscopic identification of S_Au interaction in cysteine capped gold nanoparticles
Spectrochim. Acta Mol. Biomol. Spectrosc.
Electrode processes of the sulfhydryldisulfide system: III. Cysteine at platinum and gold electrodes
J. Electroanal. Chem.
Oxidation of cysteine, cysteinesulfinic acid and cysteic acid on a polycrystalline gold electrode
J. Electroanal. Chem.
The electrochemistry of l-cystine and l-cysteine: Part 1: thermodynamic and kinetic studies
J. Electroanal. Chem.
Electrochemical investigations of amino acids at solid electrodes: Part I. Sulfur components: cystine, cysteine, methionine
J. Electroanal. Chem.
Nickel oxide microfibers immobilized onto electrode by electrospinning and calcination for nonenzymatic glucose sensor and effect of calcination temperature on the performance
Biosens. Bioelectron.
Nonenzymatic glucose sensor based on CuO microfibers composed of CuO nanoparticles
Anal. Chim. Acta
Detection of homocysteine and cysteine
J. Am. Chem. Soc.
Lead phthalocyanine as a selective Carrier for preparation of a cysteine-selective electrode
Anal. Chem.
Fluorescent and colorimetric probes for detection of thiols
Chem. Soc. Rev.
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