Facile Detection Research Articles

Using photo-induced p-n junction interface effect of CoMn2O4/β-MnO2 oxidase mimetics for colorimetric determination of hydroquinone in seawater

Detection of pollutants in seawater faces a great challenge of strong interference, and the facile detection method is lacked. The CoMn2O4/β-MnO2 p-n junction oxidase mimetics were successfully prepared for colorimetric detection of hydroquinone in seawater. The catalysis ability was enhanced significantly by the photo-induced p-n junction interface effect. It not only promoted the formation of H2O2 by suppressing the recombination of photon-generated carriers, but also provided the driving force for electron transport. The colorimetric detection of hydroquinone was achieved by fading and exhibited good adaptability in seawater. The obtained good recovery rate (97.23%–101.37%) in seawater makes it an inspiring method for practical application. The photo-induced p-n junction interface effect provides an opportunity for developing the application of colorimetric sensing in seawater detection.

A ‘three in one’ complexing agent enables copper desorption from polluted soil, its removal from groundwater and its detection

High groundwater concentrations of heavy metals such as copper are toxic to humans. Attenuated total reflectance – Fourier transform infrared spectroscopy (ATR-FTIR) demonstrated that the environmentally benign surfactant sodium lauryl lactylate (SLL) formed bidentate complexes with copper ions. CuSO4 increased the surface tension and the compressional rigidity of SLL films at air-water interfaces, providing additional evidence of SLL-Cu interactions. Here, we harness for the first time the formation of Cu-SLL complexes to achieve the three following objectives. First, SLL enabled the facile detection of copper in water samples, by enhancing the color of copper solutions (10−3 M copper concentrations could be detected with the naked eye). Second, SLL promoted the desorption of copper from model polluted soils. Therefore, SLL can be useful for surfactant flushing applications, in which surfactants are used to enhance the remediation of polluted aquifers through pump and treat. Third, SLL enhanced the treatment of water polluted with copper ions. Specifically, SLL favored the partitioning of Cu2+ into canola oil, purifying water. Therefore, canola oil could be used as liquid sorbent for the treatment of groundwater in SLL-enhanced pump and treat, in which polluted groundwater would be pumped and then treated at the surface. The safety of the proposed treatment can be improved by injecting fluids obtained with the biopolymer sodium alginate (Na-alginate) around the treated area. Na-alginate fluids (at 0.5 wt%) had low viscoelastic moduli before contact with Cu2+ (facilitating their injection) and gelled when intercepting Cu2+ ions (to allow their confinement inside the boundaries of the treated area).

Cloth-based closed bipolar electrochemiluminescence DNA sensors (CCBEDSs): A new class of electrochemiluminescence gene sensors

In this work, for the first time, the cloth-based closed bipolar electrochemiluminescence (CBP-ECL) DNA sensors (CCBEDSs) have been presented as a new class of electrochemiluminescence gene sensors, where the integration of magnetic immobilization/enrichment and CBP-ECL can be served for facile detection of double-stranded polymerase chain reaction (PCR) products of Salmonella enteritis (S. enteritis) invA gene. A self-made support is used to combine avidin-conjugated magnetic beads (AMBs) with the CBP-ECL cloth-based device, where the magnet adsorbs the AMBs onto the anode of closed bipolar electrode (C-BPE) to well immobilize and enrich the biotinylated PCR products. And, the Ru(bpy)32+ (TBR) molecules are cast onto the anode surface. When the tripropylamine (TPA) is applied to the sensing interface of DNA sensors, the TBR shows the excellent electro-photo properties. Under optimized conditions, the ECL intensity was found to be logarithmically related to the concentration of PCR products in range from 0.001 to 1000 pM. The limit of detection is 0.05 fM (about 29.93 copies/μL) and the relative deviations are 2.2% and 3.9% for inter- and intra-assays at 50 pM PCR products. The results show that the CCBEDSs have the relatively good sensitivity, wide linear range, high specificity and good stability, and have no any complex purification steps for amplification products. In addition, the CCBEDSs can determine S. enteritis in milk, egg white, grated tomato and beef samples. Therefore, the method may have broad application prospects in medical diagnosis and food detection.

Simple fluorescence optosensing probe for spermine based on ciprofloxacin-Tb3+ complexation.

We developed a facile detection method of spermine based on the fluorescence (FL) quenching of the ciprofloxacin-Tb3+ complex, which shows astrong green emission. Ciprofloxacin (CP) makes efficient bondings to Tb3+ ion as a linker molecule through carboxylic and ketone groups to form a kind of lanthanide coordination polymer. The addition of spermine that competes with Tb3+ ions for the interaction with CP due to its positive charge brings about weakened coordination linkage of CP and Tb3+. The probe exhibited high sensitivity, selectivity, and good linearity in the range of 2–180 μM with a low limit of detection of 0.17 μM. Moreover, we applied this method on the paper strip test (PST), along with the integration of a smartphone and Arduino-based device. The practical reliability of the developed probe was evaluated on human serum samples with acceptable analytical results.

Role of Tau Protein on Photophysical Properties of Carbon Dots

Aggregation of intrinsically disordered Tau protein is a key biomarker of the progressive neurodegenerative disorder Alzheimer's Disease [1]. Although the precise mechanism by which tau aggregates is not well understood, abnormal post-translational modifications of tau have been implicated in the formation of tau aggregates and neurofibrillary tangles. In vitro, Tau aggregation may be detected by the fluorescent Thioflavin T dye, which is limited by non-specific interactions between the dye and other additives and low fluorescence quantum yield. CDs are a highly modifiable nanomaterials with characteristic optical properties and poorly-understood protein interactions. Using the novel fluorescent nanoallotrope, Carbon dots (CDs), we examined an alternative method for facile detection of intrinsically disordered Tau protein. Through photophysical studies of tau protein with two varieties of CDs, we determined that Tau protein decreased the fluorescent intensity of dual-fluorescing CDs to a greater extent than nitrogen-doped CDs after monitoring fluorescence. Tau protein aggregation was also induced by using heparin and this process was monitored by using ThT as well as CD assays. The CDs exhibited similar properties with heparin-aggregated tau samples and non-aggregated tau protein under specific experimental conditions. Data indicate that carbon dots are viable sensors for proteins and could be further optimized for disease biomarker detection and quantification in the development of rapid, sensitive and selective diagnostic assays.

Generation and Use of Anti‐Click Product Antibodies for Diagnosis and Therapy

Click chemistry has found wide utility in basic biological research, molecular diagnostics, and drug discovery. Given this important and expanding role in molecular biology research, methods for facile detection of click reaction products have emerged as a key to the development of novel assays and therapeutics. While these reactions have previously been detected by appending molecular tags or fluorogenic elements to click reagents, an antibody directed against a minimal click reaction product structure allows for much more versatile and selective detection of click reaction sites in the absence of additional molecular tags. We describe the isolation, specificity, and uses of antibodies specific for unique structures created when azide groups react with dibenzocyclooctyne (DBCO) to assemble varied structures for diagnostic and therapeutic applications. In vitro phage display was used to select a panel of scFv molecules (from Creative Biolabs Inc) specifically recognizing and binding small peptides covalently joined together by azide-DBCO click chemistry. Subsequently, the best scFv binder was converted into a full human IgG1 antibody (IgG1-51). Importantly, neither smaller precursor in isolation is recognized by these novel binding molecules, which specifically bind the assembled product. Specificity studies showed that for recognition, IgG1-51 preferred peptide sequences flanking the azide-DBCO reaction product, but the identity of the specific residues involved was not crucial. Notably, IgG1-51 could strongly recognize the product of the original DBCO-peptide precursor when reacted with azidosugars positioned on cell surfaces by metabolic labeling, and some DBCO-peptides elicited even stronger cell-surface responses than the original peptide. Significant applications of IgG1-51 derive from the principle of ‘haplomers’, which we define as structures that are inert until brought into close proximity by molecular templating, after which haplomer assembly into biologically and immunologically functional products occurs. In situ assembly of functional haplomers, on or within a pathological cell target, can focus specific diagnostic and therapeutic applications while potentially greatly reducing deleterious background toxicities. An important extension to this technology is thus the deployment of haplomers incorporating the original azide- and DBCO-peptides whose reaction products are recognizable by IgG1-51. Additional antibody reagents against alternative click products (under development) will further extend the range of applications for these molecular tools. Antibodies that recognize cell surface markers that are known to exhibit abnormally high densities on certain tumor cells can be separately conjugated with specific azide- and DBCO-peptides. When two such antibodies bind to surface markers in molecular proximity, their azide- and DBCO-peptide tags can click-react, enabling subsequent recognition by IgG1-51. This in turn provides a means for selectively delivering therapeutic or diagnostic payloads to corresponding target cells.

Facile and efficient colorimetric detection of cadmium ions in aqueous systems using green-synthesized gold nanoparticles

Facile and efficient colorimetric detection of cadmium ions in aqueous systems using green-synthesized gold nanoparticles

Nano-scale selective and sensitive optical sensor for metronidazole based on fluorescence quenching: 1H-Phenanthro[9,10-d]imidazolyl-calix[4]arene fluorescent probe

It is crucial to determine and control the metronidazole (MET) ingredient in food and pharmaceuticals for human health and food safety. Even though many sensors have been previously reported to detect MET, there is still a need for a highly selective and sensitive, easy, fast, cost-effective sensor in this area. Herein, we report a fluorescent calix[4]arene derivative (PIMC) for highly selective and sensitive and facile and rapid MET detection based on fluorescence (FL) quenching. The highest FL quenching occurs when PIMC is exposed to MET solution at 400 nm (λex = 340). Owing to the quenching efficacy of MET linearly up to 5.5 × 104 nM was obtained a detection limit of 2.44 nM. Besides, interferences of other pharmaceuticals and ions on probe performance were investigated. The FL probe was successful in MET detection without the assistance of any separation techniques in a pharmaceutical sample (tablet) with an acceptable recovery of 101.3%. The applicability of the current probe as a paper-based sensor to MET detection has been successfully tested. As a result, the proposed probe presents a fast and suitable strategy to sensitive and selective detect MET and proves a good potential for practical applications, especially pharmaceutical preparations.

Highly Sensitive and Cost-Effective Portable Sensor for Early Gastric Carcinoma Diagnosis

Facile and efficient early detection of cancer is a major challenge in healthcare. Herein we developed a novel sensor made from a polycarbonate (PC) membrane with nanopores, followed by sequence-specific Oligo RNA modification for early gastric carcinoma diagnosis. In this design, the gastric cancer antigen CA72-4 is specifically conjugated to the Oligo RNA, thereby inhibiting the electrical current through the PC membrane in a concentration-dependent manner. The device can determine the concentration of cancer antigen CA72-4 in the range from 4 to 14 U/mL, possessing a sensitivity of 7.029 µAU−1mLcm−2 with a linear regression (R2) of 0.965 and a lower detection limit of 4 U/mL. This device has integrated advantages including high specificity and sensitivity and being simple, portable, and cost effective, which collectively enables a giant leap for cancer screening technologies towards clinical use. This is the first report to use RNA aptamers to detect CA72-4 for gastric carcinoma diagnosis.

Aptamer-Integrated Multianalyte-Detecting Paper Electrochemical Device.

On-site detection of multiple small-molecule analytes in complex sample matrixes would be highly valuable for diverse biosensing applications. Paper electrochemical devices (PEDs) offer an especially appealing sensing platform for such applications due to their low cost, portability, and ease of use. Using oligonucleotide-based aptamers as biorecognition elements, we here for the first time have developed a simple, inexpensive procedure for the fabrication of aptamer-modified multiplex PEDs (mPEDs), which can robustly and specifically detect multiple small molecules in complex samples. These devices are prepared via an ambient vacuum filtration technique using carbon and metal nanomaterials that yields precisely patterned sensing architecture featuring a silver pseudo-reference electrode, a gold counter electrode, and three gold working electrodes. The devices are user-friendly, and the fabrication procedure is highly reproducible. Each working electrode can be readily modified with different aptamers for sensitive and accurate detection of multiple small-molecule analytes in a single sample within seconds. We further demonstrate that the addition of a PDMS chamber allows us to achieve detection in microliter volumes of biological samples. We believe this approach should be highly generalizable, and given the rapid development of small-molecule aptamers, we envision that facile on-site multi-analyte detection of diverse targets in a drop of sample should be readily achievable in the near future.

Synthesis and Characterization of Konjac Gum/Polyethylene Glycol-Silver Nanoparticles and their Potential Application as a Colorimetric Sensor for Hydrogen Peroxide

Green and low-cost synthesis strategies for ultrasonic preparation of polymer blend matrix-based silver nanoparticles (Ag NPs) and the development of rapid and highly sensitive detection routes have a great attention in optical sensor applications. In this study, we investigated the hydrogen peroxide detection performance of Konjac gum/polyethylene glycol—silver nanoparticles (KG/PEG-Ag NPs). The KG/PEG-Ag NPs were synthesized via an ultrasonic process and characterized by different techniques, such as ultraviolet–visible spectroscopy (UV–Vis), Fourier-Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX), Transmission Electron Microscope (TEM), and The Xray Photoelectron Spectroscopy (XPS). Furthermore, we determined the experimental optimization on the effect of the rheological parameters of nanostructure with the highest correlation constant (R2:0.989–0.996), and the intrinsic viscosity (14.71–26.77 dl/g). To provide the miscible polymer blends and homogeneous dispersion of the nanostructure, we compared the rheological parameters with the experimental results. The response time was less than 5 s and the lower limit of detection was 0.071 μM. This novel, highly sensitive, rapid, and naked-eye colorimetric biosensor based-Ag NPs, which are prepared using an ultrasonic manufacturing approach, opens up a green approach of development facile detection of hydrogen peroxide in practical biomedical applications.

Green synthesis of stable platinum nanoclusters with enhanced peroxidase-like activity for sensitive detection of glucose and glutathione

The sensitive and facile detection of the concentration of glucose and glutathione (GSH) is important for our health. In this work, lily polysaccharide (LP) stabilized platinum nanoclusters (Ptn-LP NCs) were prepared by a facile synthetic strategy where LP was used as a reducing agent and stabilizer. The successful preparation of 1–2 nm platinum nanoclusters (Pt NCs) inside of Ptn-LP NCs was confirmed using UV–Vis spectra, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM), respectively. Furthermore, Ptn-LP NCs accelerated the catalytic oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) in the presence of hydrogen peroxide (H2O2), indicating their intrinsic peroxidase-like activity. The Vm values of TMB and H2O2 were 50.3 × 10−8 Ms−1 and 10.2 × 10−8 Ms−1, respectively, which were higher than those of other mimetic enzymes. The peroxidase-like property of Ptn-LP NCs was used to sensitively detect the concentration of glucose and glutathione (GSH). The detection limits of glucose and GSH were as low as 1.89 and 0.37 μM, the linear ranges of glucose and GSH were 2.5–1000 and 4–140 μM, respectively. The colorimetric method was successfully applied to detect GSH concentration in human serum. This method has great potential application in bio-related detection in the future.

Quinoline-2-thione-based fluorescent probes for selective and sensitive detections of mustard gas and its analogues

Sulfur mustard (SM, also called as mustard gas (HD)) is a persistent and highly toxic gas used as chemical weapon in wars and military conflicts. Moreover, owing to its simple structure and easy synthesis, it is the most likely chemical agent used by terrorists. For this reason, it is vital important to develop a facile, rapid and reliable detection system for SM. In this paper, we have developed four quinoline-2-thiones as fluorescent probes, 2a-2d, for the detection of SM and its analogues, half sulfur mustard (CEES) and a nitrogen mustard NH1. In the presence of KOH, these quinoline-2-thiones deprotonated to quinoline-2-thiophenol anions, which react with SM and its analogues rapidly to form quinoline-2-thiethers with highly efficient fluorescence, giving turn-on fluorescence response. The sensing products with CEES were isolated and fully characterized, thereby, the sensing mechanism was firmly established. The fluorescent probes with 4-trifluoromethyl group, 2b and 2d, exhibit rapid response to SM, CEES and NH1 (within 1 min at 60 °C for CEES and NH1), high sensitivity (limit of detection, 50 nM for SM and 20 nM for NH1) and high selectivity. Furthermore, polymer film test strips were fabricated with probe-embedded poly(ethylene oxide) for the detection of CEES vapor. These test strips displayed a rapid response (<4 min) to gaseous CEES with high sensitivity (0.2 ppm) and high selectivity. These results show that fluorescent probes 2b and 2d have a good application prospect in the field detection of mustard gas.

Rapid Multicomponent Bioluminescence Imaging via Substrate Unmixing.

Studies of biological function demand probes that can report on processes in real time and in physiological environments. Bioluminescent tools are uniquely suited for this purpose, as they enable sensitive imaging in cells and tissues. Bioluminescent reporters can also be monitored continuously over time without detriment, as excitation light is not required. Rather, light emission derives from luciferase-luciferin reactions. Several engineered luciferases and luciferins have expanded the scope of bioluminescence imaging in recent years. Multicomponent tracking remains challenging, though, due to a lack of streamlined methods to visualize combinations of bioluminescent reporters. Conventional approaches image one luciferase at a time. Consequently, short-term changes in cell growth or gene expression cannot be easily captured. Here, we report a strategy for rapid, multiplexed imaging with a wide range of luciferases and luciferins. Sequential addition of orthogonal luciferins, followed by substrate unmixing, enabled facile detection of multiple luciferases in vitro and in vivo. Multicomponent imaging in mice was also achieved on the minutes-to-hours time scale.

Development of an 18F-Labeled Irreversible Inhibitor of Transglutaminase 2 as Radiometric Tool for Quantitative Expression Profiling in Cells and Tissues.

The transamidase activity of transglutaminase 2 (TGase 2) is considered to be important for several pathophysiological processes including fibrotic and neoplastic tissue growth, whereas in healthy cells this enzymatic function is predominantly latent. Methods that enable the highly sensitive detection of TGase 2, such as application of radiolabeled activity-based probes, will support the exploration of the enzyme's function in various diseases. In this context, the radiosynthesis and detailed in vitro radiopharmacological evaluation of an 18F-labeled Nε-acryloyllysine piperazide are reported. Robust and facile detection of the radiotracer-TGase 2 complex by autoradiography of thin layer plates and polyacrylamide gels after chromatographic and electrophoretic separation owing to irreversible covalent bond formation was demonstrated for the isolated protein, cell lysates, and living cells. By use of this radiotracer, quantitative data on the expression profile of activatable TGase 2 in mouse organs and selected tumors were obtained for the first time by autoradiography of tissue sections.

Development of General Methods for Detection of Virus by Engineering Fluorescent Silver Nanoclusters.

Viruses have caused significant damage to the world. Effective detection is required to relieve the impact of viral infections. A biomolecule can be used as a template such as deoxyribonucleic acid (DNA), peptide, or protein, for the growth of silver nanoclusters (AgNCs) and for recognizing a virus. Both the AgNCs and the recognition elements are tunable, which is promising for the analysis of new viruses. Considering that a new virus such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) urgently requires a facile sensing strategy, various virus detection strategies based on AgNCs including fluorescence enhancement, color change, quenching, and recovery are summarized. Particular emphasis is placed on the molecular analysis of viruses using DNA stabilized AgNCs (DNA-AgNCs), which detect the virus's genetic material. The more widespread applications of AgNCs for general virus detection are also discussed. Further development of these technologies may address the challenge for facile detection of SARS-CoV-2.

A highly sensitive octopus-like azobenzene fluorescent probe for determination of abamectin B1 in apples

The development of detecting residual level of abamectin B1 in apples is of great importance to public health. Herein, we synthesized a octopus-like azobenzene fluorescent probe 1,3,5-tris (5′-[(E)-(p-phenoxyazo) diazenyl)] benzene-1,3-dicarboxylic acid) benzene (TPB) for preliminary detection of abamectin B1 in apples. The TPB molecule has been characterized by ultraviolet–visible absorption spectrometry, 1H-nuclear magnetic resonance, fourier-transform infrared (FT-IR), electrospray ionization mass spectroscopy (ESI-MS) and fluorescent spectra. A proper determination condition was optimized, with limit of detection and limit of quantification of 1.3 µg L−1 and 4.4 μg L−1, respectively. The mechanism of this probe to identify abamectin B1 was illustrated in terms of undergoing aromatic nucleophilic substitution, by comparing fluorescence changes, FT-IR and ESI-MS. Furthermore, a facile quantitative detection of the residual abamectin B1 in apples was achieved. Good reproducibility was present based on relative standard deviation of 2.2%. Six carboxyl recognition sites, three azo groups and unique fluorescence signal towards abamectin B1 of this fluorescent probe demonstrated reasonable sensitivity, specificity and selectivity. The results indicate that the octopus-like azobenzene fluorescent probe can be expected to be reliable for evaluating abamectin B1 in agricultural foods.

Co-Ni layered double hydroxides wrapped on leaf-shaped copper oxide hybrids for non-enzymatic detection of glucose

The leaf-shaped copper oxide (CuO) was first fabricated by a direct precipitation method. Then, the flake-shaped Co-Ni layered double hydroxides (CoNi-LDHs) were grown on the leaf-shaped CuO by using an electrodeposition method to form a unique nanostructured electrocatalyst. Due to the unique structural and compositional advantages, CoNi-LDHs wrapped around the leaf-shaped CuO exhibited good electrocatalytic characteristics. The optimized CuO/CoNi-LDHs exhibited improved non-enzymatic electrochemical sensing performance for glucose, with a reliable linear range (0.1 μM–0.384 mM) and a low limit of detection (0.065 µM, S/N = 3). The utilization of the CuO/CoNi-LDHs sensor for glucose detection in human serum was also corroborated, implying promising potential for glucose monitoring. Results demonstrated that the developed sensor provides new horizons for facile and sensitive glucose detection.

Enzyme-free and label-free detection of Staphylococcus aureus based on target-inhibited fluorescence signal recovery

In this work, a one-step fluorometric strategy based on nanometal surface energy transfer (NSET) between carbon dots (CDs) and gold nanoparticles (AuNPs) was developed for facile detection of Staphylococcus aureus (S. aureus). The fluorescence of CDs was quenched up to 63.5% by AuNPs due to nucleic acid hybridization in the presence of linker DNA, which contained the complementary sequences of S. aureus-specific aptamer, and the fluorescence signal was in the “off” state. Upon aptamer addition, the CDs was released from linker DNA through the strong competitiveness of aptamer, leading to the notable fluorescence recovered. Once S. aureus is introduced, aptamer preferentially bind to the bacterial surface and cannot hybridize with complementary sequences in the linker DNA, resulting in the fluorescence signal with “off” state. Based on these findings, the performance and reliability of the fluorescence-based assay were evaluated. Compared to direct hybridization of complementary DNA on the surface of CDs and AuNPs, our sensing strategy has enhanced detection limit (10 cfu⋅mL−1) and improved linear range (10 to 106 cfu⋅mL−1) for S. aureus. Therefore, our proposed enzyme-free and label-free strategy may become a promising method for ease of operation, sensitive and selective S. aureus detection.

Development of a novel RAA-based microfluidic chip for absolute quantitative detection of human norovirus

As the rapid spread of norovirus is a major public health problem, rapid diagnostic assays are essential in assisting the implementation of appropriate control measures. Here, we presented a facile sample partitioning norovirus digital isothermal detection (NoV-DID) chip that enables the application of a fast and low-cost digital nucleic acid amplification test (dNAAT) to norovirus detection. Our microfluidic chip had 3 layers, a PDMS cover layer, a functional layer, and a supporting layer, and consisted of a total of 5120 microchambers, each of which was able to contain a volume of 1.2 nL. This chamber digital reverse transcription recombinase-aid amplification (cdRT-RAA) assay achieved equal volume partition of samples within 10 min, with the signal amplification being completed in approximately 20 min at 39 °C, without the need for a thermal cycle device. The cdRT-RAA assay showed a good degree of linearity in the range of 1.02 × 100 to 2.04 × 103 copies (R2 = 0.99) with the limit of detection being 1.02 × 100 copies/μL, demonstrating that its sensitivity was comparable to that of RT-ddPCR. The digital nucleic acid detection method based on the microfluidic chip exhibited advantages of high sensitivity and high robustness, and might provide an alternative method for the early detection of norovirus and the prevention and control of epidemics.