Etching Of Gold Nanorods Research Articles

Rainbow-inspired multicolor lateral flow immunoassay using multibranched platinum–rhodium-cobalt nanoparticles

Traditional lateral flow immunoassay (LFIA) using single-color labels has limitations in indistinct color change and restriction to the single-mode readout, which can hardly meet the demands of high-performance detection. Inspired by the multiple colors of the rainbow, we outline a multicolor LFIA using multibranched trimetallic platinum–rhodium-cobalt nanoparticles (PRCNPs) as signal labels to initiate multicolor conversion for diverse and multicolor readouts. The intrinsic properties of PRCNPs including their trimetallic composition, multibranched morphology, and strong absorption in the visible spectrum, confer advantages in catalytic activity, antibody utilization, and signal readout. Through the synergistic integration of the catalytic PRCNPs with the etching of gold nanorods, PRCNPs-LFIA enables multicolor readouts in a rainbow-like manner. PRCNPs-LFIA allows for qualitative analysis of acetamiprid, a widely-used neonicotinoid insecticide, at 2 ng mL−1. It also provides semi-quantitative analysis based on the discrimination of at least 10 colors. Furthermore, quantitative analysis can be conducted across multiple color spaces within the range of 0.01-10 ng mL−1, achieving a lowest detection result of 0.006 ng mL−1. The recoveries of acetamiprid in food samples detected by PRCNPs-LFIA in grayscale and multiple color space modes are 87.35%-103.59%, 85.56%-114.33%, 86.14%-114.77%, and 87.81%-112.01%, respectively, with all coefficients of variation below 15%. These results demonstrate the feasibility and accuracy of PRCNPs-LFIA in practical applications. Overall, this study illustrates the potential of multifunctional PRCNPs in the development of multicolor LFIA and broadens the biosensing strategies for point-of-care testing.

Colorimetric sensing of lead ion using gold nanorod with enhanced sensitivity via catalytic etching

AbstractLead, a prevalent heavy metal, poses significant risks to human health through various exposure pathways. Herein, we propose an extremely sensitive assay toward lead ion (Pb2+) using gold nanorods (GNRs) as probes based on its catalytic activity on etching gold in the presence of 2‐mercaptoethanol and sodium thiosulfate. In the presence of Pb2+, etching predominantly occurs at the two ends of GNRs, leading to the reduction of aspect ratio and the corresponding blueshift of the localized surface plasmon resonance (LSPR). With increasing Pb2+ concentration over the range of 0–50 μM, the color of GNR solution lightens, ultimately becoming colorless. The wavelength shift (Δλ) of LSPR is highly dependent on Pb2+ concentration, with a linear regression equation of Δλ = 10.05ln[Pb2+] + 9.59 and an R2 = 0.995. The assay demonstrates high selectivity for Pb2+ over other potentially interfering ions such as Cu2+ because of its special catalytic activity in the etching of GNRs and the complexing ability of 2‐mercaptoethanol and sodium thiosulfate. Validation of the assay was accomplished by analyzing several forest‐derived food samples, affirming the accuracy in real‐world scenarios. The assay we developed holds promise for many applications in environmental protection and food safety.

Multicolor biosensor for hyaluronidase based on target-responsive hydrogel and etching of gold nanorods by H2O2

Hyaluronidase (HAase) is a potential tumor biomarker for diseases of the digestive tract and nervous system, the development of simple and sensitive techniques for HAase determination is urgent needed. Gold nanorods (Au NRs) can be etched by H2O2 with high efficiency and display color changing. In this work, a HAase-responsive hydrogel system had been designed and the amount of H2O2 spilled from the system had a close relationship with the amount of HAase, then the spilled H2O2 had been applied to etch Au NRs. The color change of the solution was used to realize semi-quantitative determination of HAase. Furthermore, the longitudinal peak shift of Au NRs had a linear correlation with the concentration of HAase in the range of 10–60 U/mL (within 40 min) and the limit of detection (LOD) was 3.8 U/mL (S/N = 3), which can be used to realize accurate quantitative analysis of HAase. The proposed method has been applied to monitor HAase in serum of pancreatic cancer patients with satisfied results.

A multicolor biosensor for alkaline phosphatase activity detection based on the peroxidase activity of copper nanoclusters and etching of gold nanorods.

Alkaline phosphatase (ALP) plays a vital role in clinical diagnoses and biomedical research. It is important to develop some convenient but sensitive methods for ALP activity detection. In this study, a multicolor biosensor for ALP activity has been developed based on the peroxidase activity of copper nanoclusters (CuNCs) and etching of gold nanorods (AuNRs). The presence of CuNCs can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue TMB+. In acid solution, TMB+ can cause the etching of AuNRs accompanied by a significant color change of the system. The presence of sodium pyrophosphate (PPi) can inhibit the peroxidase activity of CuNCs, which can be recovered after the addition of ALP. Different ALP added results in the recovery of the catalytic activity of CuNCs to different degrees and generates different amounts of TMB+. This consequently affected the morphology of the AuNRs in the system and results in the output of a vivid color change, which can be recognized with the naked eyes easily without any complicated instruments. The biosensor has a linear relationship with ALP activity in the range of 10.0-80.0 U L-1, and the detection limit is 4.6 U L-1. The proposed method has been applied to detect ALP activity in human serum samples with satisfactory results.

Microcapillary-based multicolor assay for quantitative and sensitive point-of-care testing of proteins

A microcapillary-based multicolor assay was developed for proteins quantification in serum sample with the assistance of manual centrifugal platform. The proposed assay only required the operation of “one suction and one extrusion” to realize the target detection. Myoglobin (Myo), a biomarker in the early stage of acute myocardial infarction (AMI), was chosen as the model target. The microcapillary was first modified with polydopamine (PDA), then Myo aptamer was immobilized on the PDA modified microcapillary and hybridized with glucose oxidase (Gox) functionalized DNA probe (DNA-Gox). The step “one suction” referred to the inhalation of the sample into the functionalized microcapillary. Then the target Myo in the sample could bind to the Myo aptamer on the microcapillary so that DNA-Gox complexes were released from the microcapillary into solution. Through the step “one extrusion”, the DNA-Gox complexes in the solution could catalyze glucose to generate hydrogen peroxide, and then the etching of gold nanorods (AuNRs) was initiated, causing a color change from brown to yellow. According to the color change based on the etching of AuNRs, as low as 0.1 nM Myo was detected with naked eyes. Combined with the manual centrifugal platform, even the Myo in the serum samples could be detected without power supply. It was expected to build a universal and adaptable sensing platform for different targets more quickly and efficiently.

Multicolorimetric ELISA biosensors on a paper/polymer hybrid analytical device for visual point-of-care detection of infection diseases.

Enzyme-linked immunosorbent assay (ELISA) is widely used for the detection of disease biomarkers. However, it utilizes time-consuming procedures and expensive instruments, making it infeasible for point-of-care (POC) analysis especially in resource-limited settings. In this work, a multicolorimetric ELISA biosensor integrated on a paper/polymer hybrid microfluidic device was developed for rapid visual detection of disease biomarkers at point of care, without using costly equipment. This multicolormetric ELISA platform was built on multiple distinct color variants resulted from the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and the etching of gold nanorods (AuNRs). The vivid color changes could be easily distinguished by the naked eye, and their red mean values allowed quantitative biomarker detection, without using any sophisticated instruments. When this multicolorimetric ELISA was integrated on a paper/polymer hybrid analytical device, it not only provided integrated processing and high portability but also enabled fast assays in about 50 min due to the unique advantages of paper/polymer hybrid devices. The limit of detection of 9.1 ng/μL of the hepatitis C virus core antigen, a biomarker for hepatitis C, was achieved using this multicolorimetric ELISA platform. This multicolor ELISA analytical device provides a new versatile, user-friendly, affordable, and portable immunosensing platform with high potential for on-site detections of various viruses, proteins, and biomarkers for low-resource settings such as at home, public venues, rural areas, and developing nations.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s00216-021-03359-8.

Gold nanorods-based multicolor immunosensor for visual detection of enterovirus 71 infection.

Based on the etching of gold nanorods (GNRs) and enzyme-linked immunosorbent assay (ELISA), a multicolor immunosensor for visual detection of enterovirus 71 infection is proposed. Once the immunocomplex is formed, the horseradish peroxidase bound to the ELISA plate oxidizes 3,3',5,5'-tetramethylbenzidine (TMB) into TMB2+ in the presence of hydrogen peroxide. Subsequently, TMB2+ quantitatively etches GNRs to the short GNRs, leading to a blue shift of longitudinal localized surface plasmon resonance and corresponding color responses. This change is used to develop two types of cut-off standards, which respondto the human anti-enterovirus at a concentration of71 IgM antibody. The method has been validated with clinical serum samplesand showed high sensitivity and specificity . This visual immunosensor has an important application value for point-of-care detection of EV71, especially in areas lacking detection equipment. Graphical abstract.

Etching of gold nanorods: The effects of diameter on analytical performances

Gold nanorods (GNRs) have been well employed for sensing/bio-sensing based on analytes modulated morphology or self-assembly states. Herein, we employed H2O2 based etching system (H2O2 molecules themselves and H2O2-Fe2+ Fenton reagents) as an example to study the diameters of GNRs on the analytical performances, for the colorimetric platforms using GNRs as reporters. We have found that the thinner GNRs possess a higher sensitivity; while the thicker ones bring more abound color presentation during the etching processes, which is especially for naked eye detection. In addition, a red shift of the plasmonic bands is observed for three kinds of thinner GNRs at the initial stage of the etching reaction, and the mechanism is also discussed.

Colorimetric enzymatic determination of glucose based on etching of gold nanorods by iodine and using carbon quantum dots as peroxidase mimics.

Carbon quantum dots (CQDs) with peroxidase-mimicking activity were successfully prepared from litchi rind. A colorimetric method for glucose determination was developed based on etching of gold nanorods (GNRs) using CQDs as peroxidase mimetic. The glucose oxidase-catalyzed oxidation of glucose leads to the generation of H2O2 which oxidizes added iodide under formation of elemental iodine under the catalytic action of CQDs. Iodine then etches the GNRs along the longitudinal direction due to the higher reaction activities at the tips of GNRs. This results in a stepwise decrease in the maximum absorption wavelength of the GNRs, from initially 953nm to finally 645nm. Under the optimized conditions, the shift in the maximum absorption wavelength decreases linearly in the 0.01-2.0mM glucose concentration range, and the detection limit is 3.0μM. Importantly, this method was applied to the determination of glucose in human serum. It is perceived that the CQDs are valuable peroxidase mimics due to their ease of preparation, low costs and stable catalytic activity. Graphical abstract Carbon quantum dots were prepared from litchi rind. They can induce the oxidation of gold nanorods in the presence of I- ions and H2O2. This finding was applied to design a colorimetric assay for glucose.

Rapid detection of dibutyl phthalate in liquor by a semi-quantitative multicolor immunosensor with naked eyes as readout

A multicolor competitive immunosensor for DBP detection has been proposed based on the etching of gold nanorods (GNRs) using naked eyes as readout.

A multicolorimetric assay for rapid detection of Listeria monocytogenes based on the etching of gold nanorods

Listeria monocytogenes (L. monocytogenes) is one of the most common food-borne pathogens. The authors describe a sensitive and reliable multicolorimetric assay for L. monocytogenes using a sensing system based on TMB2+ etching of gold nanorods. Apt-MNP was used as the capture probe, and IgY-BSA-MnO2 NPs was chosen as an oxidase-like nano-artificial enzyme to oxidize TMB to generate TMB2+. Under the optimized conditions, the longitudinal shift of localized surface plasmon resonances had a linear correlation with the L. monocytogenes concentration in the range between 10 to 106 cfu mL−1. Meanwhile, the sensing system can generate vivid color responses as colorful as a rainbow, and the limit of detection is as low as 10 cfu mL−1 at a glance. Recoveries ranging from 97.4 to 101.3% are found when analyzing spiked food samples without pre-enrichment. In our perception, it shows promise in rapid instrumental and on-site visual detection of L. monocytogenes.

Target-Induced Horseradish Peroxidase Deactivation for Multicolor Colorimetric Assay of Hydrogen Sulfide in Rat Brain Microdialysis.

Hydrogen sulfide (H2S) is important for normal neural functions, which involves protecting neurons from oxidative stress and neuronal transmission modulation in brain. The detection of H2S is significant for revealing its role in the diagnosis of various disease. In this study, a novel multicolor colorimetric assay based on the etching of gold nanorods (Au NRs) is proposed to evaluate H2S level with the naked eye. This measurement relies on the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) via horseradish peroxidase (HRP) to produce TMB2+, which could etch the Au NRs quickly and accompany with a distinct color change. The vivid colors can be easily distinguished with the naked eye without any sophisticated instruments. The presence of H2S can cause the deactivation of HRP, which affects the amount of TMB2+ produced and consequently affects the color changing of the system. Based on this mechanism, a simple but sensitive multicolor colorimetric assay is developed for H2S detection with a linear range of 0.05-50 μM. The proposed method is demonstrated for monitoring extracellular H2S in rat brain coupled with microdialysate.

Multicolor biosensor for fish freshness assessment with the naked eye

Fish product is one of the main seafood with the disadvantage of easy to perish. Various indexes and diverse methods have been developed to evaluate the fish freshness, but most of them are complex and cannot be applied for on-field detection. In this study, we reported a simple, visual and economical multicolor biosensor based on the etching of gold nanorods (GNRs) to evaluate the fish freshness with the naked eye. Hypoxanthine (Hx) is chosen as the index of fish freshness and it react with the dissolved oxygen to produce H2O2 at the presence of xanthine oxidase (XOD). Then GNRs are etched quickly by the H2O2 in the presence of Fe2+. Correspondingly, the GNRs surface plasmon resonance (SPR) is regulated and results in a distinctly color change of the system, which can be easily distinguished with the naked eye. Therefore, the concentration of Hx in the fish samples can be semi-quantitatively analyzed with the naked eye. The proposed multicolor Hx sensor has been successfully applied to the detection of Hx in fish samples.

Multicolor Colormetric Biosensor for the Determination of Glucose based on the Etching of Gold Nanorods.

In this work, 3,3′,5,5′-tetramethylbenzidine(II) (TMB2+), derived from H2O2-horseradish peroxidase (HRP)-3,3′,5,5′-tetramethylbenzidine (H2O2-HRP-TMB) reaction system, was used to etch AuNRs to generate different colors of solution. Many enzyme reactions are involved in the production of H2O2 (e.g., glucose can react with the dissolved oxygen in the presence of glucose oxidase (GOx) to produce H2O2). Given this information, a simple visual biosensor was developed in this study, with glucose as the example target. The detection range of the proposed system varied with the experimental conditions, such as the concentration of GOx and HRP, and enzymatic reaction time. Under the optimized conditions, the longitudinal shift of localized surface plasmon resonances (LSPR) had a linear correlation with the glucose concentration in the range of 0.1~1.0 mM. Meanwhile, the solution displayed a specific color in response to the glucose concentration, thus enabling the visual quantitative detection of glucose at a glance. Compared with the traditional monochromic colorimetry, this multicolor glucose sensor generates various vivid colors, which can be easily distinguished by naked eyes without any sophisticated instrument. Notably, the proposed method has been successfully applied to detect glucose in serum samples with satisfied results.

Successive detection of glucose and bio-copper in human serum based on a multiplex biosensor of gold nanorods

A promising combined assay for the successive detection of blood glucose and sera copper levels based on etching of gold nanorods (GNRs) was developed.

Gold nanorod-templated synthesis of polymetallic hollow nanostructures with enhanced electrocatalytic performance.

Anisotropic polymetallic hollow nanostructures are highly desired for many applications because of their unique morphology, large specific surface areas and attractive electronic effects. Here, a simple method using gold nanorods as a self-sacrificed template has been developed for the fabrication of hollow dumbbell-like nanorods of Au@PtAg. The formation of the hollow structures involves the growth of another metallic shell first, and then the etching of gold nanorods, which is induced by oxygen and ascorbic acid. The lattice mismatch and cohesive energy of the shell, along with its surface passivation, greatly affect the subsequent etching and the resulting products, as has been demonstrated by a positive control in the case of Rh and a negative control in the case of Pd. Hollow dumbbell-like nanorods of Au@PtAg show great enhancement for the dehydrogenation pathway in the oxidation of formic acid, as compared to solid Au@PtAg nanorods, PtAu nanotubes and commercial Pt/C.