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Colorimetric detection of L-histidine based on the target-triggered self-cleavage of swing-structured DNA duplex-induced aggregation of gold nanoparticles

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A rapid, highly sensitive and selective colorimetric assay is presented for visually detecting L-histidine. It is based on L-histidine-triggered self-cleavage of DNA duplex-induced gold nanoparticle (AuNP) aggregation. The citrate-capped AuNPs easily aggregate in a high concentration of salt environment. However, in the presence of L-histidine aptamers (DNA1 and DNA2), the partial strands of DNA1 and DNA2 hybridize to form a DNA duplex with a swing structure. The swing-like DNA duplexes are adsorbed on the surface of AuNPs to improve the stability of AuNPs, and the AuNPs also are better dispersed in high-salt media. When L-histidine is added to the solutions, it catalyzes the self-cleavage of DNA1 to form many single-stranded DNA (ssDNA) fragments. These ssDNA segments are adsorbed on the AuNPs and weaken the stability of AuNPs. Hence, the AuNPs aggregate in high-salt environment, and this results in a red-to-blue color change. Under the optimized conditions, L-histidine can be determined with a limit of detection of 3.6 nM. In addition, the sensor was successfully applied to the determination of L-histidine in spiked serum samples. Graphical abstractSchematic of a rapid and homogeneous colorimetric L-histidine assay. It combines L-histidine-triggered self-cleavage of the swing-like DNA duplexes and self-cleavage of DNA-induced AuNP aggregation.
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Colorimetric detection of L-histidine based on the target-triggered
self-cleavage of swing-structured DNA duplex-induced aggregation
of gold nanoparticles
Yunfei Jiao
&Qingyun Liu
&Hong Qiang
&Zhengbo Chen
Received: 8 August 2018 / Accepted: 29 August 2018 / Published online: 12 September 2018
#Springer-Verlag GmbH Austria, part of Springer Nature 2018
A rapid, highly sensitive and selective colorimetric assay is presented forvisuallydetecting L-histidine. It is based onL-histidine-
triggered self-cleavage of DNA duplex-induced gold nanoparticle (AuNP) aggregation. The citrate-capped AuNPs easily aggre-
gate in a high concentration of salt environment. However, in the presence of L-histidine aptamers (DNA1 and DNA2), the partial
strands of DNA1 and DNA2 hybridize to form a DNAduplex with a swing structure. The swing-like DNA duplexes are adsorbed
on the surface of AuNPs to improve the stability of AuNPs, and the AuNPs also are better dispersed in high-salt media. WhenL-
histidine is added to the solutions, it catalyzes the self-cleavage of DNA1 to form many single-stranded DNA (ssDNA) frag-
ments. These ssDNA segments are adsorbed on the AuNPs and weaken the stability of AuNPs. Hence, the AuNPs aggregate in
high-salt environment, and this results in a red-to-blue color change. Under the optimized conditions, L-histidine can be
determined with a limit of detection of 3.6 nM. In addition, the sensor was successfully applied to the determination of L-
histidine in spiked serum samples.
Keywords Self-cleavage of DNA .Colorimetric assay .L-Histidine detection .Gold nanoparticle aggregation .Swing-like
duplex .Ratiometric assay .Visible color change .Serum samples .Catalysis
L-Histidine (L-His), an essential amino acid in human and
mammal species, plays an essential role in the mammalian
central nervous system, the repair and growth of tissue, min-
imizing internal bleeding from microtrauma, and controlling
the transport of metals in biologically important bases [1,2].
An abnormal L-histidine level is an index of some diseases
including acute liver failure, rheumatoid arthritis, AIDS,
chronic kidney disorder, Alzheimers disease, and cancer
[38]. Therefore, the determination of L-histidine is extremely
important in biological fluids.
There are a number of methods for the detection of L-his-
tidine, such as including high performance liquid chromatog-
raphy (HPLC) [9], electrophoresis [10,11], mass spectrome-
try [12], fluorescence [13], and electrochemistry [14,15].
These approaches, while most successful, most of them show
poor selectivity, require time-consuming pre-treatment or so-
phisticated detection systems such as the use of organic sol-
vents. To circumvent these disadvantages, colorimetric
methods as a promising analytical technology, have been ex-
tensively used due to their simplicity, low cost, rapid/direct
readout with the bare eye, and no need to use expensive ana-
lytical instruments [1624]. Therefore, it is still necessary and
important todevelop a low-cost, highly sensitive and selective
colorimetric method for scaling L-histidine.
Previous reports have demonstrated that single-stranded
DNA (ssDNA) can be absorbed on gold nanoparticle
A colorimetric assay for detecting L-histidine based on target L-histidine-
triggered self-cleavage of DNA duplex-induced AuNP aggregation.
Electronic supplementary material The online version of this article
( contains supplementary
material, which is available to authorized users.
*Hong Qiang
*Zhengbo Chen
Department of Chemistry, Capital Normal University,
Beijing 100048, China
College of Chemical and Environmental Engineering, Shandong
University of Science and Technology, Qingdao 266590, China
Microchimica Acta (2018) 185: 452
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Numerous methods are known for the determination of His. They are based on various approaches, such as liquid chromatography [5,6], capillary electrophoresis [7,8], electrochemistry [9,10], surface-enhanced Raman scattering [11], chemiluminescence [12], colorimetry [13][14][15], fluorimetry [4,[16][17][18][19][20][21], and molecularly imprinted photonic hydrogels [22]. Among of them, fluorimetry can provide striking merits including relatively easy to operate, high sensitivity, wide linear range, low detection limit, and ability to real-time monitoring, etc., which render it superior compared to many of other conventional methods and evolves to be one of the most effective analyzing technologies [3,4]. ...
... Duing to the distinctive optical properties of innorganic nanoparticles (NPs), metal NPs such as Ag NPs [3] and Au NPs [14], metal oxide including ZnO [25,26] and carbon dots (C-dots) [19][20][21], etc. have been used as probes for bioanalytes sensing. However, the applications of noble metal NPs are limited by cost, precursor scarcity, and poor stability [27]. ...
... C [His] + 20.2301 (R 2 = 0.9924). The limit of detection (LOD) for His detecting is calculated to be 14.3 nM at a signal-to-noise ratio of 3. Besides, we compare the linear concentration range and LOD value for His of this system with other relevant previous work, including electrochemistry [9,10], colorimetry [13,14], MIPH-based optical sensor [22] and fluorimetry [3,[17][18][19][20][30][31][32]. The corresponding results are displayed in Table 1. ...
Full-text available
A fluorometric assay for histidine (His) is described. It is based on the inhibitory effect of His on nanocubes consisting of cobalt-containing Prussian Blue analog (CoFe NCbs), which have a strong oxidation effect on thiamine (THI) in the presence of NaOH. THI is nonfluorescent but the oxidized form (thiochrome; ThC) has a strong blue fluorescence, with excitation/emission maxima at 370/445 nm. His inhibits the oxidation effect of the CoFe NCbs due to the strong interaction between its imidazole side chain and the amino groups of the CoFe NCbs. This method is fast and has good sensitivity and selectivity. The lower detection limit is 14.3 nM of His, the linear range extends from 0.05 to 2.5 μM, and the relative standard deviation is calculated to be 1.5%. The method was successfully employed to quantify His in spiked serum samples. Graphical abstractSchematic representation of cobalt-containing Prussian Blue nanocubes (CoFe NCbs)-thiamine (THI)-based fluorometric assay for Histine (His). His inhibits the generation of thiochrome (ThC; the oxidized form of THI). The detection limit is 14.3 nM with the linear range of 0.05–2.5 μM.
... Interestingly, Jiao et al. investigated the opposite behavior of DNA-based detection platform while assessing L-histidine. [314] In this assay without histidine, DNA1 and DNA2 as histidine aptamers were partially hybridized to form a swing-like unique structure which helped the DNA duplex absorption on AuNPs and make them dispersed. L-histidine was determined with a LOD of 3.6 nM when sessile phosphodiester of the DNA1 was cleaved into two parts via self-cleavage due to catalytic action of histidine which disturbed the swing structure of duplex and created ssDNA segments. ...
Full-text available
Recent years have witnessed an exponential increase in the research on gold nanoparticles (AuNPs)-based colorimetric sensors to revolutionize point-of-use sensing devices. Hence, this review is compiled focused on current progress in the design and performance parameters of AuNPs-based sensors. The review begins with the characteristics of AuNPs, followed by a brief explanation of synthesis and functionalization methods. Then, the mechanisms of AuNPs-based sensors are comprehensively explained in two broad categories based on the surface plasmon resonance (SPR) characteristics of AuNPs and their peroxidase-like catalytic properties (nanozyme). SPR-based colorimetric sensors further categorize into aggregation, anti-aggregation, etching, growth-mediated, and accumulation-based methods depending on their sensing mechanisms. On the other hand, peroxidase activity-based colorimetric sensors are divided into two methods based on the expression or inhibition of peroxidase-like activity. Next, the analytes in environmental and food samples are classified as inorganic, organic, and biological pollutants, and recent progress in detection of these analytes are reviewed in detail. Finally, conclusions are provided, and future directions are highlighted. Improving the sensitivity, reproducibility, multiplexing capabilities, and cost-effectiveness for colorimetric detection of various analytes in environment and food matrices will have significant impact on fast testing of hazardous substances, hence reducing the pollution load in environment as well as rendering food contamination to ensure food safety.
... Literature review brings many analytical procedures for His determination in pure form or in pharmaceutical formulations, as well as in biological samples: colorimetry (Newman and Turnbull, 1960, Jiao et al., 2018, Razavi and Khajehsharifi, 2021, spectrophotometry (Patel Vandana et al., 2009), spectrofluorimetry (Ambrose et al., 1969, Gerber, 1970, Alevridis et al., 2020, chemiluminescence (Zhu et al., 2002, Kiba et al., 2006, Hun, 20159, voltammetry (Jaselskis, 1958, Moreira and Fogg, 1991, Farias et al., 2008, microbiology (Horn et al., 1948), kinetic spectrophotometry (Mitić et al., 2004), potentiometry (Staden andHolo, 2007, Abbaspour et al., 2004) and cation-exchange chromatography (Stampina, 2021). ...
Full-text available
The objective of this research was to develop a kinetic-spectrophotometric method for the determination of microquantities of L-histidine in pure form and dietary supplements. The method was based on the kinetics of ampicillin degradation by Ni(II) ion as a catalyst in the presence of L-histidine in a strongly alkaline medium. The rate of this reaction was monitored spectrophotometrically by measuring the increase in absorbance at 265 nm as a function of time. The same approach was used for the investigation of the reaction rate in the absence of histidine. A differential variant of the tangent method was used to process the kinetic data. Beer’s law was obeyed in the interval of histidine concentration from 1.24 μg/ml to 11.63 μg/ml with the relative standard deviation ranging from 8.1% to 0.7%. The detection limit of 0.46 μg/ml was estimated based on the 3S0 criterion. The interference effects of some metal ions, anions, and other molecules on the reaction rate were studied to assess method selectivity. Herein described method was applied for the quantification of histidine in dietary supplements. The point hypothesis test confirmed that there was no significant difference between the proposed and the reference method.
... It's over expression could cause variety of diseases including histidinemia, advanced liver cirrhosis and asthma [13]. Many analytical techniques have been employed for L-histidine assay in biological fluids such as capillary electrophoresis [14], voltammetry [15], liquid chromatography [16], colorimetry [17] and fluorimetry [18]. Among these methods, fluorimetric detection is reported to be most favourable one in the detection of histidine due to their sensitivity, stability and reliability [19]. ...
A benzimidazole derived probe [(6-(1H-indol-3-yl)-5,6-dihydrobenzo[4], [5]imidazo [1,2-c]quinazoline) (IDBIQ)] was synthesized and structurally characterized by single-crystal X-ray diffraction analysis and spectroscopic methods. The probe IDBIQ crystallizes in a monoclinic P21/c space group which is found to be highly sensitive and also selective towards the analytes HgII, F⁻ and histidine. The probe exhibits turn-off fluorescence for HgII and histidine while it is ratiometric towards F⁻ ions. These quenching and ratiometric fluorescent changes have been further explored by ¹H NMR titrations and DFT/TD-DFT calculations. The limit of detection of the probe towards the analytes was found to be in nano-molar range and the receptor was observed to bind with the analytes in 1:1 stoichiometric manner.
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Continuous monitoring of a variety of biomolecules and bio-relevant ions is of tremendous importance to maintain the physiological balance and evaluation of metabolic parameters. Therefore, development of fast, selective, sensitive...
The present study aimed to report a novel electrochemical sensor through electropolymerization of o-aminophenol (o-AP) and m-dihydroxy benzene (m-DB) as monomers on the surface of the glassy carbon electrode (GCE) for the determination of histidine (His) as a template molecule. The developed sensor exhibited satisfactory sensitivity and high selectivity, and also offered a linear range between 0.005 and 10.0 μM with a detection limit of 0.9 nM. Finally, it is worth mentioning that we also aimed at employing the proposed sensor for the detection of His in blood serum samples.
This research work aims to propose an extraction method using chitosan as the sorbent and gold nanoparticles (AuNPs) as the colorimetric sensor for the development of a simple, cost-effective, rapid, sensitive, and selective detection method for histidine. The colorimetric assay is based on the aggregation of AuNPs in the presence of Hg2+ ions and histidine. The state of AuNPs generally changes from dispersion to aggregation. The change in state is accompanied by a corresponding change in color (from red wine to blue). Therefore, the solid phase extraction (SPE) method using chitosan as the sorbent was used to extract the AuNPs to improve the sensitivity of detection. It was found that the extraction by means of a sensor system using chitosan could increase the detection signal for histidine by 10 times. The calibration curve, which is the plot of absorbance ratio (A650/A528) against the concentration of histidine, shows a linear relation in the concentration range of 100 - 800 nM. The limit of detection (LOD) and limit of quantitation (LOQ) of the method were found to be 99.88 and 107.45 nM, respectively. Good recoveries were also obtained (range: 99.75 - 104.43%) with relative standard deviations (RSDs) below 5.89% in real water samples. Moreover, this method can be used for the selective detection of histidine even in the presence of other amino acids. The proposed method has been successfully used in the determination of histidine in mineral water samples.
An extremely sensitive and highly selective sensing assay for histidine (His) in biological sample is demonstrated through the N-acetyl-cysteine (NAC) functionalized gold nanoparticles (AuNPs). To improve the detection efficiency, the external conditions of temperature and pH value are optimized. We assume that three main forces of hydrogen bond, electrostatic attraction, and hydrophobic force between His and NAC cause the formation of close crosslinking, resulting in the aggregation of AuNPs accompanied by an obvious color change. Thus, the assay is highly sensitive for His with a fast readout within 10 s and the detection limit of 176 pM which is the lowest one from what's been reported in the colorimetric detection. Furthermore, due to the special imidazole ring in His structure, the assay exhibits the high selectivity of His sensing among 18 common amino acids. Besides, the system has been successfully used for His detection in spiked urine and serum samples. This novel colorimetric sensor significantly improves the analytical merit of His sensing and applies in the biological sample detection.
Full-text available
Saxitoxin (STX) is one of the most important marine toxins which affects the safety of domestic water. Rapid, sensitive and selective recognition of STX is crucial in environment monitoring. Here, we demonstrate a facile and ultrasensitive colorimetric sensor based on gold nanoparticles (Au NPs) and aptamer (Au NPs-aptamer biosensor) for specific and quantitative detection of STX. The aptamer reacts specifically with STX, resulting in the aggregation of Au NPs and the color change of the Au NP solution. The lowest detection concentration of the colorimetric sensor is 10 fM (3 fg mL⁻¹), and a good linear relationship (R² = 0.9852) between the absorbance ratio and STX concentrations (10 fM to 0.1 μM) indicates that our Au NPs-aptamer biosensor can be used for quantitative sensing of STX. The detection time of STX is 30 minutes, and the sensor is successfully applied in the specific detection of STX in seawater. The Au NP-aptamer biosensor shows great potential in practical applications to monitor environmental pollution, marine aquaculture pollution, and seafood safety.
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The authors describe a biosensor for histidine that is based on the use of a DNAzyme catalytic beacon. The Cu(II)-dependent DNA-cleaving DNAzyme (Cu-Enzyme) was modified with a quencher (BHQ1) at its 5′ end, and the corresponding substrate strand (Cu-Sub) was modified with a quencher and the FAM fluorophore at its 5′ and 3′ ends, respectively. The green FAM emission of the system is completely quenched after the Cu-Enzyme is hybridized with Cu-Sub. The presence of Cu(II) triggers the cleavage of the Cu-Sub so that fluorescence recovers. Histidine forms a complex with Cu(II) ion. The complex is not capable of cleaving Cu-Sub effectively so that the fluorescence of the system is not restored. These findings were exploited to design a robust and sensitive assay for the determination of histidine. Fluorescence intensity is linearly related to the concentration of histidine in the range between 0.05 and 40 μM, and the detection limit is 20 nM. The method has been successfully applied to the determination of histidine in (spiked) human urine and gave satisfying results. Graphical abstractSchematic of a fluorescence biosensor for histidine based on a quencher-labeled Cu-Enzyme (Cu-Enzyme refers to Cu(II)-dependent DNA-cleaving DNAzyme; Cu-Sub refers to the corresponding substrate strand of Cu-Enzyme: Cu-Substrate; SA refers to sodium ascorbate).
A novel assay for histidine and cysteine has been constructed based on modulation of fluorescent copper nanoclusters (CuNCs) by molecular switches. In our previous work, a dumbbell DNA template with a poly-T (thymine) loop has been developed as an excellent template for the formation of strongly fluorescent CuNCs. Herein, for the first time, we established this biosensor for sensing two amino acids by using dumbbell DNA-templated CuNCs as the single probe. Among 20 natural amino acids, only histidine and cysteine can selectively quench fluorescence emission of CuNCs, because of the specific interaction of these compounds with copper ions. Furthermore, by using nickel ions (Ni2+) and N-ethylmaleimide as the masking agents for histidine and cysteine respectively, an integrated logic gate system was designed by coupling with the fluorescent CuNCs and demonstrated selective and sensitive detection of cysteine and histidine. Under optimal conditions, cysteine can be detected in the concentration ranges of 0.01–10.0 μM with the detection limit (DL) of as low as 98 pM, while histidine can be detected in the ranges of 0.05–40.0 μM with DL of 1.6 nM. In addition, histidine and cysteine can be observed with the naked eye under a hand-held UV lamp (DL, 50 nM), which can be easily adapted to automated high-throughput screening. Finally, the strategy has been successfully utilized for biological fluids. The proposed system can be conducted in homogeneous solution, eliminating the need for organic cosolvents, separation processes of nanomaterials, or any chemical modifications. Overall, the assay provides an alternative method for simultaneous detection of cysteine and histidine by taking the advantages of high speed, no label and enzyme requirement, and good sensitivity and specificity, and will satisfy the great demand for determination of amino acids in fields such as food processing, biochemistry, pharmaceuticals, and clinical analysis. Graphical abstract
We proposed a colorimetric method for l-histidine detection based on Cu2+-mediated DNAzyme and G-quadruplex-hemin complex catalyzed oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS). In this system, after the addition of l-histidine, the formation of G-quadruplex-hemin complex will be disturbed, thus the colorimetric signal intensity conversely corresponds to the concentration of histidine. In this assay, a lower detection limit of l-histidine (50 nM) is addressed comparing to previously reported colorimetric methods. The cost is extremely low as the proposed design is both label-free and enzyme-free. All the more vitally, the colorimetric detection procedure is substantially straightforward with no further modification processes. By and large, the sensor can provide a promising plan for the detection of l-histidine.
Bimetallic-based nanoparticles usually display improved catalytic performance compared to monometallic counterparts. Herein, the well-dispersed FePt nanoparticles decorated on the surface of graphene oxide (GO) nanosheets have been successfully synthesized by a simple polyol protocol method. The FePt/GO nanocomposites were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), magnetic property measurement system (MPMS), and Fourier transform infrared spectra (FT-IR), respectively. Interestingly, FePt/GO nanocomposites demonstrated the highly intrinsic peroxidase-like activity and can rapidly catalyze to oxidize the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue product oxidized TMB (oxTMB), in the presence of H2O2 only in 30 s observed by the naked eye. Electron spin resonance (ESR) revealed that the underlying catalytic mechanism of FePt/GO nanocomposites was attributed to the generation of hydroxyl radicals ([rad]OH) from decomposing of H2O2, due to the synergistic effect between FePt nanoparticles and GO nanosheets. Moreover, H2O2 can be detected over a wide linear detection range of 0.03–0.5 mM with a detection limit of 2.2 × 10⁻⁵ M. Based on the mimic enzyme FePt/GO, a colorimetric ultrasensitive H2O2 sensor was constructed with the help of TMB in buffer solution.
Since abnormal metabolism of histidine (His) is defined as an indicator of several diseases, detection of His in biological fluids becomes increasingly urgent to us. However, due to similar structures and properties of different amino acids, selective quantification of His is difficulty, and typically needs the participation of special reagents. In this work, we report for the first time that nickel ions (Ni²⁺) can induce the allostery of G-quadruplex, and is thus able to manipulate the activity of G-quadruplex DNAzyme. Experimental results indicate the interaction between Ni²⁺ and guanine is critical to the allostery. In comparison with Ni²⁺-guanine interaction, Ni²⁺-His interaction exhibits higher affinity. Therefore, a colorimetric His biosensor is fabricated, and His can be facilely discriminated by naked eyes. Relying on the high activity of DNAzyme, His in a range of 50 nM-400 μM is determined with this method, and low detection limit (36 nM) is obtained. More importantly, His can be directly distinguished in the absence of other toxic reagents. In addition, the amount of His in serum is also measured, suggesting the applicability of this biosensor in real sample detection. Overall, this work provides an alternative way to design G-quadruplex DNAzyme-based analytical approaches.
In this paper, FePt-Au ternary metallic hybrid nanaoparticles (FePt-Au HNPs) were prepared with FePt nanocubes as seeds and then the seeds were combined with Au(I) precursor through a facile hydrothermal approach. And the FePt-Au HNPs were characterized by a series of technical methods such as transmission electron microscopy (TEM), X-ray diffraction pattern (XRD) and UV–vis absorption spectra. Moreover, the as-prepared FePt-Au HNPs possessed the excellent peroxidase-like activity which could rapidly catalyze the oxidation reaction of substrate 3,3′,5,5′ −tetramethylbenzidine (TMB) to obtain a typical blue product which could be observed apparently by the naked eye only within 30 s. Notably, the color response is instant, due to the fast electron transfer between the substrate and H2O2 with the aid of FePt-Au HNPs. Based on the catalytic mechanism of fast electron transfer and the intrinsic peroxidase-like activity of FePt-Au HNPs, a visual colorimetric sensor for ultrafast detecting H2O2 was constructed with a wide linear range of 20–700 μM as well as a relative lower limit of detection (LOD) of 12.33 μM. Furthermore, the ultrafast sensor based on FePt-Au HNPs as peroxidase mimics was also successfully applied to detect H2O2 in milk samples.
A highly sensitive sensor for detection of histidine (His) based on the nitrogen-doped graphene quantum dots (N-GQDs)-Cu2 + system has been designed. The N-GQDs were synthesized by one-step hydrothermal approach according to previous report. The fluorescence of N-GQDs can be effectively quenched by Cu2 + due to the binding between Cu2 + and functional groups on the surface of N-GQDs. The high affinity of His to Cu2 + enables Cu2 + to be dissociated from the surface of N-GQDs and recovering the fluorescence. The sensor displayed a sensitive response to His in the concentration range of 0–35 μmol L− 1, with a detection limit of 72.2 nmol L− 1. The proposed method is successfully applied to detect His in samples with a recovery range of 96–102%.
In this work, we propose a strategy for the fluorescence assay of histidine (His) and cysteine (Cys) by using lanthanide coordination polymer nanoparticles (Ln-CPN) as a fluorescent probe. The Ln-CPN were prepared by self-assembly of adenosine monophosphate (AMP) with Tb(3+), i.e. AMP-Tb. The nonluminescent AMP-Tb could be efficiently sensitized by 5-sulfosalicylic acid (SSA). The fluorescence of AMP-Tb-SSA can be remarkably quenched by Cu(2+), and that of the resulting Cu/SSA/AMP-Tb can be significantly enhanced by His and Cys. Thus, a specific fluorescence "turn-on" assay for His and Cys was developed by using Cu/SSA/AMP-Tb as a sensing platform. The enhanced fluorescence intensity was proportional to the His and Cys concentration in the range from 0.2 to 150 μM and 0.5 to 200 μM, respectively, with the detection limits of 70 nM and 100 nM. Additionally, taking advantage of a masking agent for His, the differentiation of His from Cys was achieved in our system. Furthermore, the protocol can also work well for analyzing His and Cys in practical plasma samples with recovery in the range of 100.3-104.1%.
Herein, we presented a facile strategy for highly sensitive and selective detection of both Cu²⁺ and histidine (His) by combining the peroxidase-like nanozyme activity of gold nanoclusters with amino acid's ambidentate nature. The peroxidase-like catalytic ability of histidine-Au nanoclusters (His-AuNCs) can be inhibited by the addition of Cu²⁺. The sensitivity of this probe to Cu²⁺ is significant with a linear range of 1–100 nM, and a low detection limit of 0.1 nM. More interestingly, His-AuNC/Cu²⁺ undergoes recovery of the activity upon exposure to free His, because His/Cu²⁺ complex is more stable due to the participation of the imidazole ring of His. The method displays a good selectivity toward histidine over all the other amino acids, with a wide linear relationship in the range of 20 nM–2 μM, and a low detection limit of 20 nM. The feasibility of the probe for the rapid analysis of copper ion and His in human serum has been demonstrated with satisfactory results. With the merits of high sensitivity and selectivity, simplification, low cost, and visual readout with the naked eye, this novel 'turn-off/turn-on' sensing approach based on the amino acid's ambidentate nature is potentially applicable to metal ions, amino acids and peptides in biological and environmental areas.
An efficient novel colorimetric sensor for H2O2 based on peroxidase-like CeO2-montmorillonite (MMT) nanocomposites that were successfully prepared by a facile one-pot approach, was realized. In comparison with other nanomaterials as peroxidase mimics, the catalytic reaction by the well-dispersed CeO2-MMT nanocomposites was in accordance with typical Michaelis–Menten kinetics, which exhibited a higher affinity to 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, bringing about a superior peroxidase-like activity (a distinct blue color change was observed rapidly within 30 s, by the naked eye.) than that of pure CeO2 nanoparticles, MMT and their hybrid materials, respectively. Under the optimized conditions, CeO2-MMT nanocomposites were used to establish a colorimetric biosensor for the detection of H2O2 in a relative wide range of 9 × 10⁻⁶ M to 5 × 10⁻⁴ M with a lower detection limit of 7.8 × 10⁻⁶ M. The sensor was successfully applied in H2O2 detection in milk samples.