A portable chemical sensor for histidine based on the strategy of click chemistry

Bacterial Cellulose-Based MOF Hybrid as a Sensitive Switch Off-On Luminescent Sensor for the Selective Recognition of l-Histidine

In this study, a stable and luminescent UiO-66-NH2 (UN) and its derivative Cu2+@UN were prepared and utilized successfully as an Off-On luminescent sensing platform for effective, selective, as well as rapid (5 min) detection of l-Histidine (l-His). The UN reveals efficient quenching in the presence of Cu2+ ions through photoinduced electron transition (PET) mechanism as a dynamic quenching process (in the range of 0.01-1 mM) forming Cu2+@UN sensing platform. However, due to the remarkable affinity between l-His and Cu2+, the luminescence of Cu2+@UN is recovered in the presence of l-His indicating Turn-On behavior via a quencher detachment mechanism (QD). A good linear relationship between the l-His concentration and luminescence intensity was observed in the range of 0.01-40 μM (R2 = 0.9978) with a detection limit of 7 nM for l-His sensing. The suggested method was successfully utilized for l-His determination in real samples with good recoveries and satisfying consequences. Moreover, the result indicates that only l-His induces a significant luminescence restoration of Cu2+@UN and that the signal is significantly greater than that of the other amino acids. Also, the portable test paper based on bacterial cellulose (BC) as the Cu2+@UNBC sensing platform was developed to conveniently evaluate the effective detection of l-His.

Nonlinear Optical and Ion Sensor Properties of Novel Molecules Conjugated by Click Chemistry

The molecular structure, luminescence behavior, and electronic energy level of an organic optoelectronic materials are important parameters for its synthesis. The electro-optical properties can be changed by modifying the structure of the molecule to make the electronic energy level adjustable. In this article, a series of organic conjugated micro-molecules are successfully synthesized by linking small compound units. This metal-free [2 + 2] click chemistry process generates donor–acceptor chromophore substances with high yield, high solubility, and adjustable energy levels, which can be widely used for sensors and nonlinear optics in different fields. A-TCNE, A-TCNQ, and A-F4-TCNQ molecules are characterized comprehensively via UV-Vis-NIR spectra, ¹H NMR spectra, infrared spectroscopy, and mass spectrometry. The unique nonlinear optical phenomena and powerful intra-molecular charge–transfer interactions of these new materials give them fascinating potential for application as optoelectronic materials.

Single nanoparticle identification coupled with auto-identify algorithm for rapid and accurate detection of L-histidine

In this work, an auto-identify sensor was constructed for rapid and high-precision detection of L-histidine. The proposed strategy is based on the auto-identify algorithm and the aggregation of alkynyl and azide functionalized gold nanoparticles induced by the Cu⁺ catalyzed azides and alkynes cycloaddition (CuAAC) reaction. Specially, the color of scattering light spots for the aggregated gold nanoparticle (AuNPs) caused by CuAAC reaction was quite different from that of the monomers. However, L-histidine can bind to Cu²⁺ and inhibits the production of Cu⁺, hence preventing the aggregation of AuNPs. Therefore, there is a distinct change of color as the addition of L-histidine under dark-field microscopy. Then, L-histidine can be quantitatively detected by combining the color change with the Meanshift algorithm accurately and automatically. Such proposed method has been successfully applied for the detection of L-histidine in serum sample with satisfying result.

Multivalent, Stabilized Mannose-6-Phosphates for the Targeted Delivery of Toll-Like Receptor Ligands and Peptide Antigens

Mannose-6-phosphate (M6P) is recognized by the mannose-6-phosphate receptor and plays an important role in the transport of cargo to the endosomes, making it an attractive tool to improve endosomal trafficking of vaccines. We describe herein the assembly of peptide antigen conjugates carrying clusters of mannose-6-C-phosphonates (M6Po). The M6Po's are stable M6P mimics that are resistant to cleavage of the phosphate group by endogenous phosphatases. Two different strategies for the incorporation of the M6Po clusters in the conjugate have been developed: the first relies on a "post-assembly" click approach employing an M6Po bearing an alkyne functionality; the second hinges on an M6Po C-glycoside amino acid building block that can be used in solid-phase peptide synthesis. The generated conjugates were further equipped with a TLR7 ligand to stimulate dendritic cell (DC) maturation. While antigen presentation is hindered by the presence of the M6Po clusters, the incorporation of the M6Po clusters leads to increased activation of DCs, thus demonstrating their potential in improving vaccine adjuvanticity by intraendosomally active TLR ligands.

A Highly Sensitive Electrochemiluminescence Biosensor for Pyrophosphatase Detection Based on Click Chemistry-Triggered Hybridization Chain Reaction in Homogeneous Solution

The abnormal expression of pyrophosphatase (PPase) is closely related to many diseases and malignant tumors, so the detection for PPase is of great significance in clinical diagnosis, disease monitoring, and other biomedical aspects. In this study, a sensitive and specific electrochemiluminescence (ECL) biosensor combined highly specific Cu⁺-catalyzed azide-alkyne cycloaddition (CuAAC) with high efficiency of hybridization chain reaction (HCR) for the purpose of detecting pyrophosphatase has been designed. Highly efficient hybridization chain reaction amplification processed in homogeneous solution and the amplification products were connected to the electrode surface in one step, which solved the problem of low DNA amplification efficiency on the electrode surface because of the steric hindrance. Ru(phen)₃²⁺ was embedded into the dsDNA and functioned as ECL probes; the enhanced ECL intensity of the system had a linear relationship with the logarithm of PPase concentration in the range of 0.025-50 mU with a detection limit of 8 μU. The method was proved to be of good specificity, repeatability, and stability that could be used for screening and quantitatively determining pyrophosphatase inhibitor sodium fluoride. The practicability of this method in clinical application has been proved through the detection of serum from the clinical arthritis patients. Moreover, the method can be used to monitor PPase activity of arthritis patients before and after administration to provide reference for the effect of drug treatment.

DNA template-mediated click chemistry-based portable signal-on sensor for ochratoxin A detection

A novel signal-on portable sensing system has been developed for OTA detection using personal glucose meter (PGM) as signal transducer. In the study, we explore the potential of using a short dsDNA as template to trigger the "click" ligation of two DNA strands, further improve the stability of DNA strand on the magnetic beads (MBs) surface, and thereby reduce the background signal. Compared with no "click" ligation, the background signal decreases 7.5 times. Both the sensitivity and selectivity are greatly promoted. A high sensitivity with OTA detection down to 72 pg/mL is achieved, which is comparable with several existing detectors, such as fluorescence-based detectors and electrochemical detectors. The feasibility of the strategy in real samples is well verified and evaluated by detecting OTA in feed samples, indicating the potential application in the food safety field.

Copper(I)-Catalyzed Click Chemistry as a Tool for the Functionalization of Nanomaterials and the Preparation of Electrochemical (Bio)Sensors

Proper functionalization of electrode surfaces and/or nanomaterials plays a crucial role in the preparation of electrochemical (bio)sensors and their resulting performance. In this context, copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) has been demonstrated to be a powerful strategy due to the high yields achieved, absence of by-products and moderate conditions required both in aqueous medium and under physiological conditions. This particular chemistry offers great potential to functionalize a wide variety of electrode surfaces, nanomaterials, metallophthalocyanines (MPcs) and polymers, thus providing electrochemical platforms with improved electrocatalytic ability and allowing the stable, reproducible and functional integration of a wide range of nanomaterials and/or different biomolecules (enzymes, antibodies, nucleic acids and peptides). Considering the rapid progress in the field, and the potential of this technology, this review paper outlines the unique features imparted by this particular reaction in the development of electrochemical sensors through the discussion of representative examples of the methods mainly reported over the last five years. Special attention has been paid to electrochemical (bio)sensors prepared using nanomaterials and applied to the determination of relevant analytes at different molecular levels. Current challenges and future directions in this field are also briefly pointed out.

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.

Structure and dynamics of a dl-homocysteine functionalized fullerene-C60–gold nanocomposite: a femtomolar l-histidine sensor

An Au@Hcys-C₆₀ nanocomposite for l-histidine sensing.

Transforming the blood glucose meter into a general healthcare meter for in vitro diagnostics in mobile health

Recent advances in mobile network and smartphones have provided an enormous opportunity for transforming in vitro diagnostics (IVD) from central labs to home or other points of care (POC). A major challenge to achieving the goal is a long time and high costs associated with developing POC IVD devices in mobile Health (mHealth). Instead of developing a new POC device for every new IVD target, we and others are taking advantage of decades of research, development, engineering and continuous improvement of the blood glucose meter (BGM), including those already integrated with smartphones, and transforming the BGM into a general healthcare meter for POC IVDs of a wide range of biomarkers, therapeutic drugs and other analytical targets. In this review, we summarize methods to transduce and amplify selective binding of targets by antibodies, DNA/RNA aptamers, DNAzyme/ribozymes and protein enzymes into signals such as glucose or NADH that can be measured by commercially available BGM, making it possible to adapt many clinical assays performed in central labs, such as immunoassays, aptamer/DNAzyme assays, molecular diagnostic assays, and enzymatic activity assays onto BGM platform for quantification of non-glucose targets for a wide variety of IVDs in mHealth.

Highly selective ratiometric fluorescent recognition of histidine by tetraphenylethene–terpyridine–Zn(ii) complexes

Fluorescent detection of histidine is achieved with distinctive color change from yellow to blue by using the Zn(ii) complexes of the terpyridine–tetraphenylethene conjugates.

Ultra-Low Level Detection of L-Histidine Using Solution-Processed ZnO Nanorod on Flexible Substrate

This work demonstrates a novel label free and sensitive approach for the detection of L-histidine. This is a simple and reliable method for ultra-low level detection of L-histidine. All solution processed synthesizing technique was utilized to develop such type of detection scheme. Silicon substrate was replaced by normal transparent sheet to make it more facile and cost-effective detection technique. Fabricated device for L-histidine detection works upon the variation of current through the ZnO nanorod with L-histidine concentration. Operation principle strongly depends upon the electron charge transfer between metal cation and L-histidine inside the chelating complex. Morphological, structural and optical characterization of solution processed synthesized ZnO nanorod (ZnO NR) was carried out prior to sensor device fabrication. Our sensor device exhibits the sensitivity around 0.86 nA/fM and lower limit of detection (LOD) ∼ 0.1 fM(S/N=3).

Synthesis of water-compatible surface-imprinted polymer via click chemistry and RAFT precipitation polymerization for highly selective and sensitive electrochemical assay of fenitrothion

A novel water-compatible fenitrothion imprinted polymer was prepared on Au nanoparticles (AuNPs) by click chemistry and reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization (RAFTPP). The RAFT chain-transfer agent was synthesized on the surface of AuNPs using click chemistry, then an imprinted polymer with hydrophilic polymer brushes was prepared on the RAFT chain-transfer agent modified AuNPs by RAFTPP, mediated by hydrophilic polyethylene glycol macromolecular cochain-transfer agent. The obtained molecularly imprinted material showed improved accessibility to fenitrothion and recognition property in water medium. When the material was immobilized on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of fenitrothion, the resulting electrochemical sensor presented linear response in the range of 0.01-5 μM, with a sensitivity of 6.1 μA/μM mm(2). The low limit of detection was 8 nM (S/N=3). The sensor was successfully applied to the determination of real samples and the recovery for standard added was 95-108%.

Fully-drawn carbon-based chemical sensors on organic and inorganic surfaces

Mechanical abrasion is an extremely simple, rapid, and low-cost method for deposition of carbon-based materials onto a substrate. However, the method is limited in throughput, precision, and surface compatibility for drawing conductive pathways. Selective patterning of surfaces using laser-etching can facilitate substantial improvements to address these current limitations for the abrasive deposition of carbon-based materials. This study demonstrates the successful on-demand fabrication of fully-drawn chemical sensors on a wide variety of substrates (e.g., weighing paper, polymethyl methacrylate, silicon, and adhesive tape) using single-walled carbon nanotubes (SWCNTs) as sensing materials and graphite as electrodes. Mechanical mixing of SWCNTs with solid or liquid selectors yields sensors that can detect and discriminate parts-per-million (ppm) quantities of various nitrogen-containing vapors (pyridine, aniline, triethylamine).

Aptamer-based portable biosensor for platelet-derived growth factor-BB (PDGF-BB) with personal glucose meter readout

A novel portable biosensor for sensitive and selective detection of platelet-derived growth factor-BB (PDGF-BB) had been developed based on the specific recognition between aptamer and protein using a personal glucose meter (PGM) as readout. In the presence of PDGF-BB, the primary aptamer of PDGF-BB which is bound to the surface of streptavidin magnespheres paramagnetic particles (SA-PMPs) reacts quantitatively with invertase-functionalized secondary aptamer of PDGF-BB to form a stable complex, resulting in the attachment of invertase on the SA-PMPs. Subsequently, the invertase catalyzes the hydrolysis of sucrose to produce a large amount of glucose and quantitative readout by the PGM. The enhanced signal of the PGM has a relationship with the concentration of PDGF-BB in the range of 1.0 × 10(-14) M~3.16 × 10(-12) M, and the detection limit is 2.9 fM. The proposed portable biosensor had been successfully applied to assay the PDGF-BB in saliva samples.