Recyclable Decoration of Amine-Functionalized Magnetic Nanoparticles with Ni2+ for Determination of Histidine by Photochemical Vapor Generation Atomic Spectrometry

BSA Capped gold Nanoclusters Modulated by Copper ion for Sensitive and Selective Detection of Histidine in Biological Fluid

This research proposed a sample and environmentally sustainable technique for the synthesis of bovine serum albumin capped gold nanoclusters (BSA-AuNCs) with outstanding fluorescence. The synthesized BSA-AuNCs were investigated using various ways before being combined with Cu2+ to produce a fluorescent switch probe (BSA-AuNCs-Cu2+) for histidine determination. After adding Cu2+, the fluorescence of the BSA-AuNCs was quenched, the fluorescence intensity was enhanced after adding histidine due to good coordination between Cu2+ and histidine. The significant chelation of histidine with Cu2+ demonstrated the viability of developing a selective "switch on" probe for histidine detecting over other amino acids. Unlike existing fluorescent nanomaterial-based approaches for detecting histidine, this study promises good selectivity, high efficiency, and the avoiding of chemical solvents. The designed BSA-AuNCs-Cu2+ fluorescent probe demonstrated an acceptable linear detection range of 0 to 240 µM under optimum circumstances, with a detection limit of 0.9 µM. The BSA-AuNCs-Cu2+ system was investigated in rat serum and human urine, with recoveries ranging from 97.2 to 108.2%, demonstrating its potential applicability for histidine detection with favorable results.

Development of an equipment free paper based fluorimetric method for the selective determination of histidine in human urine samples

A direct fluorimetric method, employing μicro-analytical paper-based devices (μ-PADs) for the selective determination of histidine (HIS) is described. The suggested method exploits the fluorescence emission of histidine after its rapid reaction with o-phthalaldehyde (OPA) at a basic medium (pH = 10) on the surface of a paper device with the application of a UV lamp at 354 nm. The devices are inexpensive and are composed of chromatographic paper and wax barriers. The analytical protocol is easily applicable with minimal technical expertise and without the need of expensive experimental apparatus. The user has to add a test sample, illuminate the device with a UV lamp, and read the fluorescence of the sensing area using a simple imaging device such as a cell-phone camera. The method is free from common interferences likely to affect the measurement of histidine and is selective among all other amino acids. This analytical procedure was optimized and validated, paying special attention to its intended application. The detection limits are as low as 1.8 μM with very satisfactory precision ranging from 6.4% (intra-day) to 8.9% (inter-day). Random urine samples from adult volunteers (n = 5) were successfully analyzed and HIS content ranged between 260 and 1114 μmol L^-1 with percentage recoveries in the range of 78.2 and 124.6%.

Turn-on and blue-shift fluorescence sensor toward L-histidine based on stable CdII metal-organic framework with tetranuclear cluster units

A novel Cd^II-based two-fold interpenetrated metal-organic framework (MOF), namely {[Cd₂(BTDB)₂(4,4-bpy)]·DMF}_n (JXUST-14), (H2BTDB = 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid and 4,4-bpy = 4,4-bipyridine), has been prepared and characterized. Single-crystal structure determination reveals that JXUST-14 has a tetranuclear cluster based 6-connected pcu topological network with Schlafli symbol {4¹²·6³}. When soaked in common organic solvents and aqueous solutions with diverse pH values of 2-12 for 48 h, JXUST-14 remains stable. JXUST-14 is a highly selective and sensitive luminescent sensor for L-histidine (His) with a detection limit of 11.1 ppm. JXUST-14 is the first Cd^II-based MOF for the detection of His via turn-on and fluorescence blue-shift effects. Experimental study and theoretical calculation suggest that the sensing process can be mainly attributed to a charge transfer and energy transfer mechanism. More interestingly, LED lamps of JXUST-14 and JXUST-14@His were successfully developed, which endowed efficient sensitivity for His detection and thus provide great potential for future applications.

A Convenient and Label-Free Colorimetric Detection for L-Histidine Based on Inhibition of Oxidation of 3,3',5,5'-Tetramethylbenzidine-H2O2 System Triggered by Copper Ions

L-Histidine (L-His) is an essential amino acid, which is used to synthesize proteins and enzymes. The concentration of L-His in the body is controlled to regulate tissue growth and repair of tissues. In this study, a rapid and sensitive method was developed for colorimetric L-his detection using Cu²⁺ ions to inhibit the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB)-H₂O₂ system. H₂O₂ can oxidize TMB to oxTMB in the presence of copper, and the change in color from colorless (TMB) to blue (oxTMB) is similar to that observed in the presence of peroxidase. However, because the imidazole ring and carboxyl group of L-His can coordinate with Cu²⁺ ions to form stable L-His-Cu²⁺ complexes, the color of the TMB-H₂O₂ solution remains unchanged after the addition of L-His. Therefore, because L-His effectively hinders the colorimetric reaction of TMB with H₂O₂, this assay can be used to quantitatively determine the concentration of L-His in samples. Under optimized conditions, our colorimetric sensor exhibited two linear ranges of 60 nM to 1 μM and 1 μM to 1 mM for L-His detection and a detection limit of 50 nM (S/N = 3); furthermore, the assay can be performed within 20 min. Moreover, the proposed assay was used to determine the concentration of L-His in urine samples, suggesting that this convenient and label-free colorimetric method presents promising applications in bioanalytical chemistry and clinical diagnosis.

Weak-emission iridium(III) complexes as fluorescent turn-on probes for ultrasensitive and selective imaging histidine in living cells and rat tissues

Visualizing endogenous histidine (His) in living systems is an important and challenging work in life science field. Herein, two weak-emission iridium(III) complexes (IrL1 and IrL2) with solvent ligands (CH₃CN) were designed and synthesized. It was found that IrL2 showed a better performance for detecting His with more remarkable fluorescence enhancement and lower limit of detection (LOD = 35 nM). Moreover, the recognitionmechanism was confirmed to be a substitution of solvent ligands by His. Importantly, probe IrL2 was applicable to visualize endogenous His in living cells and rat tissue slices via an energy-dependent endocytotic pathway. We hope that this probe can serve as a useful tool for the diagnosis of His-related diseases.

Intriguing pH-modulated Luminescence Chameleon System based on Postsynthetic Modified Dual-emitting Eu3+@Mn-MOF and Its Application for Histidine Chemosensor

Due to the disruption by other nonanalyte factors, single-emission probes have been limited in complicated detecting systems. In this work, a pH-modulated luminescence chameleon system based on lanthanide-based MOF (Eu³⁺@Mn-MOF), with stable structure and miraculous dual-emitting fluorescent properties, was synthesized by a postsynthetic modification (PSM) strategy of a simple hydrothermal and agitation method. Amazingly, not only can the Eu³⁺@Mn-MOF emit a broad emission at 500 nm attributed to the ligand-based fluorescence emission but it can also exhibit the characteristic emission of Eu³⁺ ions responding to the antenna effect. Moreover, the Eu³⁺@Mn-MOF displays an interesting luminescence color transition between acidic and basic solutions. Inspired by this phenomenon, a pH-modulated luminescence chameleon system was first constructed and employed to detect histidine, a kind of basic amino acid for a variety of biological matters, causing a unique fluorescence signal of the ratio-dependent color to change from yellow to light pink which differs from the color change of other water-soluble amino acids. Therefore, Eu³⁺@Mn-MOF can be as a practical pH-modulated luminescence chameleon system chemsensor for sensing histidine with low detection limit, high sensitivity, and rapid sensing time. In conclusion, the postsynthetic modified Eu³⁺@Mn-MOF has outstanding applications in the fields of chemical detection and human health.

Histidine-triggered turning-on of gold/copper nanocluster fluorescence for the sensitive and selective detection of histidine

Gold/copper nanoclusters with histidine-triggered turn-on fluorescence for sensing histidine sensitively and selectively.

A highly selective "turn-on" electroanalysis strategy with reduced copper metal-organic frameworks for sensing histamine and histidine

A highly selective and sensitive electroanalysis strategy has been developed for sensing histamine (HTA) and histidine (His) with "turn-on" signal outputs using copper nanocomposites (Cu NCs) of reduced copper metal-organic frameworks (Cu MOFs). It was discovered that the Cu NC-modified electrodes could display the sharp and stable oxidation peaks of solid-state CuCl electrochemistry at a low potential (about -0.10 V). More interestingly, once HTA or His was introduced, the peaking currents of the electrodes would increase due to the specific interaction between Cu²⁺ and imidazole groups of HTA or His. A highly selective electroanalysis method was thereby developed for the detection of both HTA and His in the concentration range of 0.010-100 μM. Besides, the application feasibility of the developed electroanalysis strategy was demonstrated for the evaluation of HTA and His separately in red wine and urine samples. Such an electroanalysis candidate for HTA and His holds great potential for wide applications in the fields of food analysis and clinical disease diagnosis.

Cadmium Assisted Photochemical Vapor Generation of Tungsten for Detection by Inductively Coupled Plasma Mass Spectrometry

Efficient photochemical vapor generation (PVG) of tungsten has been achieved for the first time using a 19 W thin film flow-through photoreactor. The volatile product (most probably tungsten hexacarbonyl) was generated using a flow injection mode and 40% (v/v) formic acid as the reaction medium. An inductively coupled plasma mass spectrometer was utilized for ultrasensitive detection. The addition of Cd²⁺ as a sensitizer was critical, enhancing the overall PVG efficiency some 30 000-fold. At an optimal irradiation time of 19 s, a 6.1-fold enhancement factor and an overall PVG efficiency of 43% were determined from a comparison of the response to direct solution nebulization when using a sample flow rate of 2 mL min^-1 and 500 mg L^-1 Cd²⁺ as a sensitizer. A limit of detection of 0.9 ng L^-1 and repeatability (RSD) of 2% at 100 ng L^-1 were achieved. Interference from inorganic acids (HNO₃, HCl, H₂SO₄, and HF) was investigated with respect to analytical application to real samples. The accuracy and practical feasibility of this ultrasensitive methodology was successfully verified by analysis of Certified Reference Material CTA-FFA-1 (Fine Fly Ash) and six natural water samples with low W concentrations.

A sensitive and selective electroanalysis strategy for histidine using the wettable well electrodes modified with graphene quantum dot-scaffolded melamine and copper nanocomposites

A wettable well was fabricated on an electrode, which was further modified with carbon quantum dot-scaffolded nanocomposites of melamine and copper for probing histidine through a unique displacement reaction route. The developed electrode with wettable well enables the condensing enrichment of analytes from the sample droplets, improving the electroanalytical sensitivity.

A novel label-free colorimetric detection of l-histidine using Cu2+-modulated G-quadruplex-based DNAzymes

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.

Optical sensing at the nanobiointerface of metal ion-optically-active nanocrystals

Optically-active nanocrystals (such as quantum dots and plasmonic noble metal nanoparticles) have received great attention due to their size-tunable optical properties. The indicator displacement assay (IDA) with optically-active nanocrystals has become a common practice for optical sensor development, since no sophisticated surface functionalization of nanoparticles is required. Among the IDA-based optical sensors, the use of metal ions as receptors seems to be attractive. Therefore, in this review, the research progress of optical sensing at the nanobiointerface of metal ion-optically-active nanocrystals has been summarized. In particular, metal ion-mediated selective recognition has been summarized here based on the classical Hard-Soft-Acid-Base (HSAB) principle, which has been seldom mentioned before. Most of the references were therefore categorized according to their located place based on the HSAB theory. Besides, several metal ion modulation strategies that were not related to the HSAB theory (e.g., redox modulation) were also included. Finally, due to the cross-talk of metal ions in selective recognition, we have also summarized sensor array development based on multiple metal ion receptors in IDA sensing with optically-active nanocrystals. Several interesting applications of the IDA sensing with metal ions as receptors and optically-active nanocrystals as indicators are presented, with specific emphasis on the design principles and photophysical mechanisms of these probes.

Silica-coated triangular gold nanoprisms as distance-dependent plasmon-enhanced fluorescence-based probes for biochemical applications

Plasmon-enhanced fluorescence (PEF)-based anisotropic nanostructures are considered extremely promising tools for improving the inherent problems of traditional fluorophores and for detecting important biomolecules with high sensitivity. Herein, a novel triangular gold nanoprism (AuNPR)-based fluorescence probe, AuNPR@SiO₂@12,17-tetramethyl-3-dihydro-(2s-trans)-thyl-7(Ce6), was developed for PEF by virtue of multiple "hot spots" of AuNPRs. Fluorescence enhancement of fluorophores can be realized owing to the larger and stronger electromagnetic fields located at the sharp tips of AuNPRs than those on spherical particles and nanorods. A silica shell was employed as a rigid spacer to precisely adjust the distance between the AuNPR and Ce6 for optimal PEF. Owing to the improved fluorescence signal, core-shell PEF-based AuNPRs can be applied as a turn-on probe for highly selective and sensitive detection of pyrophosphate (PPi) with a desirable detection limit of 0.2 μM using a displacement approach. Meanwhile, we demonstrated that these nanomaterials have great potential for real-time monitoring of polymerase chain reaction (PCR) products, successfully revealing an approximately 240 times higher detectable fluorescence response than that of traditional gel electrophoresis. Furthermore, cell imaging indicates the potential applications of PEF-based probes in living cells.

Nitrogen-doped carbon nanoparticle modulated turn-on fluorescent probes for histidine detection and its imaging in living cells

In this work, nitrogen-doped carbon nanoparticle (N-CNP) modulated turn-on fluorescent probes were developed for rapid and selective detection of histidine. The as synthesized N-CNPs exhibited high fluorescence quantum yield and excellent biocompatibility. The fluorescence of N-CNPs can be quenched selectively by Cu(II) ions with high efficiency, and restored by the addition of histidine owing to the competitive binding of Cu(II) ions and histidine that removes Cu(II) ions from the surface of the N-CNPs. Under the optimal conditions, a linear relationship between the increased fluorescence intensity of N-CNP/Cu(II) ion conjugates and the concentration of histidine was established in the range from 0.5 to 60 μM. The detection limit was as low as 150 nM (signal-to-noise ratio of 3). In addition, the as-prepared N-CNP/Cu(II) ion nanoprobes showed excellent biocompatibility and were applied for a histidine imaging assay in living cells, which presented great potential in the bio-labeling assay and clinical diagnostic applications.

Heterogeneous Cu(ii)/l-His@Fe3O4 nanocatalyst: a novel, efficient and magnetically-recoverable catalyst for organic transformations in green solvents

A novel, efficient and green Cu(ii)/l-His@Fe₃O₄ catalyst has been applied successfully in the synthesis of heterocyclic compounds.

Ferric ion induced enhancement of ultraviolet vapour generation coupled with atomic fluorescence spectrometry for the determination of ultratrace inorganic arsenic in surface water

A novel method of ultraviolet vapour generation (UVG) coupled with atomic fluorescence spectrometry (AFS) was developed for the determination of ultratrace inorganic arsenic (iAs) in surface water.

Determination of Hg, Fe, Ni, and Co by Miniaturized Optical Emission Spectrometry Integrated with Flow Injection Photochemical Vapor Generation and Point Discharge

A compact and robust OES technique was developed for the sensitive determination of Hg, Fe, Ni, and Co by utilizing photochemical vapor generation and point discharge as the sampling technique and the excitation source, respectively. Mercury cold vapor and the volatile species of Fe, Ni, and Co were generated when standard or sample solutions containing formic acid were exposed to a UV photochemical reactor and subsequently separated from the liquid phase for transport to the microplasma and detection of their atomic emission. Limits of detection (LODs) of 0.10, 10, 0.20, and 4.5 μg L(-1) were obtained for Hg, Fe, Ni and Co, respectively. Compared to conventional microplasma OES, this method not only broadens the scope of elements amenable to determination, but also provides 2- and 7-fold improvement in the LODs for Hg and Ni, respectively. Method validation was demonstrated by analysis of three Certified Reference Materials (GBW08607, DORM-3, and DORM-4) with satisfactory results, and by good spike recoveries (93-111%) from three real water samples.

Synthesis of hierarchical nickel anchored on Fe3O4@SiO2 and its successful utilization to remove the abundant proteins (BHb) in bovine blood

The synthesis of hierarchical nickel anchored on Fe₃O₄@SiO₂ and their successful utilization to remove the abundant proteins (BHb) in bovine blood have been demonstrated.

A highly selective phosphorescence probe for histidine in living bodies

A heterobimetallic ruthenium(ii)–nickel(ii) complex has been developed for phosphorescence imaging of histidine in live cells and bodies.

A DNA–scaffolded silver nanocluster/Cu2+ ensemble as a turn-on fluorescent probe for histidine

A new type of rapid, sensitive, and selective fluorescence turn-on assay was developed for detection of histidine using a DNA–scaffolded silver nanocluster/Cu²⁺ ensemble (DNA–AgNC/Cu²⁺).