Functionalized Gold Nanoparticles Research Articles

SERS-Based Microneedle Biosensor for In Situ and Sensitive Detection of Tyrosinase.

Tyrosinase (TYR) emerges as a key enzyme that exerts a regulatory influence on the synthesis of melanin, thereby assuming the role of a critical biomarker for the detection of melanoma. Detecting the authentic concentration of TYR in the skin remains a primary challenge. Distinguished from ex vivo detection methods, this study introduces a novel sensor platform that integrates a microneedle (MN) biosensor with surface-enhanced Raman spectroscopy (SERS) technology for the in situ detection of TYR in human skin. The platform utilized dopamine (DA)-functionalized gold nanoparticles (Au NPs) as the capturing substrate and 4-mercaptophenylboronic acid (4-MPBA)-modified silver nanoparticles (Ag NPs) acting as the SERS probe. Here, the Au NPs were functionalized with mercaptosuccinic acid (MSA) for DA capture. In the presence of TYR, DA immobilized on the MN is preferentially oxidized to dopamine quinone (DQ), a process that results in a decreased density of SERS probes on the platform. TYR concentration was detected through variations in the signal intensity emitted by the phenylboronic acid. The detection system was able to evaluate TYR concentrations within a linear range of 0.05 U/mL to 200 U/mL and showed robust anti-interference capabilities. The proposed platform, integrating MN-based in situ sensing, SERS technology, and TYR responsiveness, holds significant importance for diagnosing cutaneous melanoma.

Functionalized gold nanoparticle enhanced nanorod hyperbolic metamaterial biosensor for highly sensitive detection of carcinoembryonic antigen

Hyperbolic metamaterial (HMM) biosensors based on metals have superior performance in comparison with conventional plasmonic biosensors in the detection of low concentrations of molecules. In this study, a nanorod HMM (NHMM) biosensor based on refractive index changes for carcinoembryonic antigen (CEA) detection is developed using secondary antibody modified gold nanoparticle (AuNP-Ab2) nanocomposites as signal amplification element for the first time. Numerical analysis based on finite element method is conducted to simulate the perturbation of the electric field of bulk plasmon polariton (BPP) supported by a NHMM in the presence of a AuNP. The simulation reveals an enhancement of the localized electric field, which arises from the resonant coupling of BPP to the localized surface plasmon resonance supported by AuNPs and is beneficial for the detection of changes of the refractive index. Furthermore, the AuNP-Ab2 nanocomposites-based NHMM (AuNP/Ab2-NHMM) biosensor enables CEA detection in the visible and near-infrared regions simultaneously. The highly sensitive detection of CEA with a wide linear range of 1–500 ng/mL is achieved in the near-infrared region. The detectable concentration of the AuNP/Ab2-NHMM biosensor has a 50-fold decrease in comparison with a NHMM biosensor. A low detection limit of 0.25 ng/mL (1.25 pM) is estimated when considering a noise level of 0.05 nm as the minimum detectable wavelength shift. The proposed method achieves high sensitivity and good reproducibility for CEA detection, which makes it a novel and viable approach for biomedical research and early clinical diagnostics.

Rapid visual dual-mode detection of Zr(IV) based on L-histidine functionalized gold nanoparticles.

Heavy metal pollution has always been a great threat to human health and safety. Compared with other heavy metals, although zirconium ion (Zr(IV)) is equally harmful, due to the lack of research on Zr(IV) in the biological systems and environment, its detection does not seem to have received the attention it deserves. Herein, a rapid visual dual-mode detection (colorimetric and chrominance method) of Zr(IV) based on L-histidine functionalized gold nanoparticles (HIS-AuNPs) has been reported. AuNPs and HIS-AuNPs before and after adding Zr(IV) were characterized by UV-Vis, TEM, DLS, Zeta potential, EDS and FT-IR, etc. These results showed that L-histidine was successfully modified on the surface of AuNPs by forming a stable Au-N bond, and its modification had little effect on the dispersion degree of AuNPs. After the addition of Zr(IV), interaction of this metal ion with the imidazolyl group on L-histidine can obviously cause the aggregation of HIS-AuNPs within 12min, and the dispersion state and particle size of HIS-AuNPs can be significantly changed. These two detection modes were established by means of absorbance and color change of solution, and being used in addition and recovery experiments of Zr(IV) in natural water. Under the optimal conditions, these two modes exhibited good linearity within 15-70 and 20-100μmolL-1, and limit of detection of 2.62 and 6.25μmolL-1. The proposed method was highly sensitive and selective, which provided a new convenient way to realize the detection of Zr(IV).

Visual and quantitative lateral flow immunoassay based on Au@PS SERS tags for multiplex cardiac biomarkers

Rapid and sensitive detection of multiple biomarkers by lateral flow immunoassay (LFIA) remains challenging for signal amplification for commonly used nanotags. Herein, we report a novel LFIA strip for visual and highly sensitive analysis of two cardiac biomarkers based on functionalized gold nanoparticles @ polystyrene microsphere (Au@PS）microcavity as surface-enhanced Raman scattering (SERS) tags. Antibody-modified Au@PS was designed as a SERS label. The evanescent waves propagating along the surface of the PS microcavity and the localized surface plasmons of the gold nanoparticles were coupled to enhance the light-matter interaction synergistically for Raman signal enhancement. In this strategy, the proposed Au@PS SERS tags-based LFIA was carried out to quantify the content of the heart failure and infarct biomarkers synchronously within 15 min and get the limits of detection of 1 pg/mL and 10 pg/mL for cardiac troponin I (cTnI) and N-terminal natriuretic peptide precursor (NT-proBNP), respectively. The results demonstrated 10–20 folds more sensitivity than that of the standard colloidal gold strip and fluorescent strip for the same biomarkers. This novel quantitative LFIA shows promise as a high-sensitive and visual sensing method for relevant clinical and forensic analysis.

A bacterial biosensor based on gold nanoparticles functionalized by a hydrophobin-chimera and combined with machine learning for user-friendly detection

A chimeric protein, in which a cationic antimicrobial peptide was fused to the adhesive self-assembling moiety of a fungal class I hydrophobin, was produced and used to easily functionalize gold nanoparticles (f-AuNPs). f-AuNPs are able to bind Escherichia coli and Staphylococcus epidermidis bacteria, tested as model organisms. A reverse colorimetric assay was then set up based on the induced aggregation of the free f-AuNPs. This leads to changes in optical properties of the solution, visible even by naked eyes. This approach allows detection of 10 CFU mL−1 of E. coli within 15 min and can be applicable to detect bacterial contamination in real matrices. Notably, the colorimetric variation was combined to machine-learning methodologies inferring data from photos of the colored solutions, acquired by smartphones. This fast, highly practical and flexible system, would enable on-site measurements and, therefore, help to prevent significant contaminations.

A review on gold nanoparticles as an innovative therapeutic cue in bone tissue engineering: Prospects and future clinical applications

Bone damage is a complex orthopedic problem primarily caused by trauma, cancer, or bacterial infection of bone tissue. Clinical care management for bone damage remains a significant clinical challenge and there is a growing need for more advanced bone therapy options. Nanotechnology has been widely explored in the field of orthopedic therapy for the treatment of a severe bone disease. Among nanomaterials, gold nanoparticles (GNPs) along with other biomaterials are emerging as a new paradigm for treatment with excellent potential for bone tissue engineering and regenerative medicine applications. In recent years, a great deal of research has focused on demonstrating the potential for GNPs to provide for enhancement of osteogenesis, reduction of osteoclastogenesis/osteomyelitis, and treatment of bone cancer. This review details the latest understandings in regards to GNPs based therapeutic systems, mechanisms, and the applications of GNPs against various bone disorders. The present review aims to summarize i) the mechanisms of GNPs in bone tissue remodeling, ii) preparation methods of GNPs, and iii) functionalization of GNPs and its decoration on biomaterials as a delivery vehicle in a specific bone tissue engineering for future clinical application.

Terahertz Lattice enhanced Quasi-Anapole Immunosensor assisted by protein antibody and AuNPs

Terahertz (THz) metasurface immunosensor has the characteristics of label-free detection, good biocompatibility and high specificity because the antibody-modified of biomarkers has the ability to specifically recognize corresponding biomarkers and increase the detection sensitivity to the concentration of the recognized antigen. The limit of detection (LoD) of THz metasurface immunosensor is highly dependent on resonant field enhancement of metasurface. The anapole mode shows a radiationless state with nontrivial oscillating current configuration. To observe such mode in farfield, in this work, the concept of quasi-anapole (QA) mode is presented which is induced when the electric and toroidal dipoles with identical intensity radiate in antiphase on the metasurface with the unit cell of two split ring resonators (SRRs) on both sides of the central cut-wire. In addition, by coupling the first-order lattice mode to the QA mode, lattice-enhanced QA mode (LQA) was investigated and observed to further enhance field confinement and decrease radiative loss. As a practical application, immunosensor was designed and fabricated by functionalized gold nanoparticles conjugated with the specific monoclonal antibody onto the LQA metasurface to detect the cell concentration of SARS-CoV-2 spike protein. The experimental results indicate that the response of LQA immunosensor depends heavily on the concentration of the Anti-S modified on its surface. When the concentration of Anti-S is 50 pg/ml, the LoD reaches to 3 pg/ml (39 fmol). Such THz LQA immunosensor also shows good specific identification and validates its effectiveness in biomedical sensing.

A low-cost paper and solution based colorimetric detection of bacteria using glucose-functionalized gold nanoparticles

Colorimetric bacterial detection based on functionalized gold nanoparticles (AuNPs) is simple, fast, and highly sensitive, and has been applied in real-time on-site monitoring and rapid testing. In this study, a paper- and solution-based colorimetric sensor for the direct detection of bacteria was developed using glucose-functionalized phyto-synthesized AuNPs (Glu-AuNPs) as a transducer. The proposed paper-based colorimetric assay was investigated for six different bacterial strains, three gram-negative bacteria namely E. coli (ATCC 11229), Pseudomonas aeruginosa (ATCC 10231), and Klebsiella pneumonia (ATCC 13884) and three gram-positive bacterial pathogens namely Staphylococcus aureus (ATCC 25923), Streptococcus pneumoniae (ATCC 49619), and Bacillus subtilis (ATCC 21332). The color intensity variation and color shifts in the affordable paper-based and solution-based sensors respectively could be observed with the naked eye. The sensing performance was evaluated using Adobe Photoshop, which exhibited an increase in color intensity with increasing bacterial concentration, with a recovery of 96 % for E.coli. Solution-based sensor exhibiting blue-shifted absorbance relies on the mechanism of repulsive interactions between negatively charged bacteria and negatively charged Glu-AuNPs. This assay is suitable for the detection of bacteria in the real sample. The direct detection of bacteria by simple colorimetric assay utilizing functionalized AuNPs has tremendous potential for bacterial detection in contaminated water.

Functionalized Gold Nanoparticles for Facile Pattern-Controlled Surface Coatings.

Gold nanoparticles (AuNPs) have been widely investigated as surface modifiers; nevertheless, most methods still require the pretreatment of surfaces and several steps to control coating efficiency and patterns for improved functionality. We developed functionalized AuNPs through borate-protected dopamine (B-AuNPs). The simple activation of B-AuNPs with a strong acid to remove the protected borate groups produces adhesive dopamine AuNPs (D-AuNPs). D-AuNP-coated surfaces with varied but controlled features and properties such as coating density and surface pattern were achieved using D-AuNPs with a precisely controlled dopamine density and coating conditions. Such adhesive and easily manipulated AuNPs provide a facile and time-saving technology to achieve sophisticated surface coatings using AuNPs.

Application of a Biomimetic Nanoparticle-Based Mock Virus to Determine SARS-CoV-2 Neutralizing Antibody Levels in Blood Samples Using a Lateral Flow Assay.

The presence of neutralizing antibodies against SARS-CoV-2 in blood, acquired through previous infection or vaccination, is known to prevent the (re)occurrence of outbreaks unless the virus mutates. Therefore, the measurement of neutralizing antibodies constitutes an indispensable tool in assessing an individual's and a population's immunity against SARS-CoV-2. For this reason, we have developed an innovative lateral flow assay (LFA) capable of detecting blood-derived neutralizing antibodies using a biomimetic SARS-CoV-2 mock virus system. Here, functionalized gold nanoparticles (AuNPs) featuring the trimeric spike (S) protein at its surface imitate the virus's structure and are applied to monitor the presence and efficacy of neutralizing antibodies in blood samples. The detection principle relies on the interaction between mock virus and the immobilized angiotensin-converting enzyme 2 (ACE2) receptor, which is inhibited when neutralizing antibodies are present. To further enhance the sensitivity of our competitive assay and identify low titers of neutralizing antibodies, an additional mixing pad is embedded into the device to increase the interaction time between mock virus and neutralizing antibodies. The developed LFA is benchmarked against the WHO International Standard (21/338) and demonstrated reliable quantification of neutralizing antibodies that inhibit ACE2 binding events down to a detection limit of an antibody titer of 59 IU/mL. Additional validation using whole blood and plasma samples showed reproducible results and good comparability to a laboratory-based reference test, thus highlighting its applicability for point-of-care testing.

Functionalized gold nanoparticles coated with bacterial alginate and their antibacterial and anticancer activities

Abstract Gold nanoparticles (Au-NPs) have several uses for nanobiotechnologists because of their beneficial biomedical properties. Alginates have various biomedical and industrial applications. The aim of this study is to extract alginate from Azotobacter chroococcum, synthesize chemical Au-NPs (Ch/Au-NPs), and load the NPs with the extracted alginate to form Azotobacter alginate gold nanocomposites (Azto/Alg-Au-NCMs). The Ch/Au-NPs and Azto/Alg-Au-NCMs were characterized by UV-spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), zeta potential, and transmission electron microscopy (TEM). The anticancer activities were determined using the breast cancer cell line MCF-7, human lung cancer cell line H1299, and Vero cell line. The results obtained by UV-spectroscopy exhibited a surface plasmon resonance that was clearly noticeable at 530 nm, and the EDS analysis proved that gold was present in percentages of 50.11 and 28.08 in the Ch/Au-NPs and Azto/Alg-Au-NCMs, respectively. There were several similarities between the alginic acid and the alginate extracted from A. chroococcum, and small modifications were proved by FT-IR spectroscopy. Negative charges were shown by the zeta potential. Crystalline and cubic NPs were shown by XRD analysis and TEM. TGA demonstrated the purity of the Ch/Au-NPs and the existence of organic compounds in the Azto/Alg-Au-NCMs. Both the Ch/Au-NPs and Azto/Alg-Au-NCMs had antibacterial activities against Staphylococcus aureus ATCC 25923, Proteus mirabilis, Enterobacter sp., and Pseudomonas aeruginosa and possessed anticancer activities against MCF-7 and H1299.

Screening Method for the Visual Discrimination of Olive Oil from Other Vegetable Oils by a Multispecies DNA Sensor.

Olive oil is a prominent agricultural product which, in addition to its nutritional value and unique organoleptic characteristics, offers a variety of health benefits protecting against cardiovascular disease, cancer, and neurodegenerative diseases. The assessment of olive oil authenticity is an extremely important and challenging process aimed at protecting consumers and producers. The most frequent adulteration involves blending with less expensive and readily available vegetable/seed oils. The methods for adulteration detection, whether based on changes in metabolite profiles or based on DNA markers, require advanced and expensive instrumentation combined with powerful chemometric and statistical tools. To this end, we present a simple, multiplex, and inexpensive screening method based on the development of a multispecies DNA sensor for sample interrogation with the naked eye. It is the first report of a DNA sensor for olive oil adulteration detection with other plant oils. The sensor meets the 2-fold challenge of adulteration detection, i.e., determining whether the olive oil sample is adulterated and identifying the added vegetable oil. We have identified unique, nucleotide variations, which enable the discrimination of seven plant species (olive, corn, sesame, soy, sunflower, almond, and hazelnut). Following a single PCR step, a 20 min multiplex plant-discrimination reaction is performed, and the products are applied directly to the sensing device. The plant species are visualized as red spots using functionalized gold nanoparticles as reporters. The spot position reveals the identity of the plant species. As low as <5-10% of adulterant was detected with particularly good reproducibility and specificity.

Detection of Femtomolar Amyloid-β Peptides for Early-Stage Identification of Alzheimer's Amyloid-β Aggregation with Functionalized Gold Nanoparticles.

Progressive amyloid-β (Aβ) fibrillar aggregates have long been considered as the pathogenesis of Alzheimer's disease (AD). Biocompatible and stable cysteine-Aβ peptide-conjugated gold nanoparticles (Cys-Aβ@AuNP) are demonstrated as suitable materials for detecting subfemtomolar Aβ peptides in human plasma. Incubation with Aβ peptides causes the Cys-Aβ@AuNP to aggregate and changes its absorption spectra. The spectral change is especially apparent and noticeable when detecting subfemtomolar Aβ peptides, and the aggregates contain only two or three AuNPs. Cys-Aβ@AuNP can also be used to identify early-stage Aβ oligomerization, which is not possible using the conventional method, in which the fluorescence of thioflavin-T is measured. The ability to detect Aβ oligomerization can facilitate therapeutics for AD. In addition, the binding of Aβ peptides by Cys-Aβ@AuNP in combination with centrifugation redirects the conventional Aβ aggregation pathway and can effectively inhibit the formation of toxic Aβ oligomers or fibrils. Therefore, the proposed Cys-Aβ@AuNP can also be used to develop effective therapeutic agents to inhibit Aβ aggregation. The results obtained in this study are expected to open revolutionary ways to both detect and inhibit Aβ aggregation at an early stage.

Integrated Electrochemical Carbon Capture and Utilization by Redox‐Active Amine Grafted Gold Nanoparticles

AbstractElectrochemical carbon capture and utilization (eCCU) from flue gas CO2 could avoid high energy consumption and capital input in conventional capture, storage, and utilization, which is a promising approach for achieving negative emissions and producing “e‐chemicals.” However, low CO2 concentration and leftover O2 in the flue gas presumably lowers the eCCU performance. Herein, redox‐active 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole (AMT) functionalized gold nanoparticles are synthesized to achieve integrated electrochemical capture and reduction of CO2 in simulated flue gas (SFG, 15% CO2, 4% O2, balanced with N2), achieving maximum CO Faradaic efficiency of 80.2% at −0.45 V versus RHE in H‐type cell, and 66.0% at voltage of 2.7 V in a full cell, respectively. The AMT ligand can capture CO2 by strong interaction with CO2 in the reduced state and serve as a selective layer to suppress O2 reduction, which provides the ability of electrochemical carbon capture from SFG and significantly decreases energy required for CO2 electro‐reduction.

Differential local ordering of mixed crowders determines effective size and stability of ss-DNA capped gold nanoparticle.

Understanding the influence of a crowded intracellular environment on the structure and solvation of DNA functionalized gold nanoparticles (ss-DNA AuNP) is necessary for designing applications in nanomedicine. In this study, the effect of single (Gly, Ser, Lys) and mixture of amino acids (Gly+Ser, Gly+Lys, Ser+Lys) at crowded concentrations is examined on the structure of the ss-DNA AuNP using molecular dynamics simulations. Using the structural estimators such as pair correlation functions and ligand shell positional fluctuations, the solvation entropy is estimated. Combining the AuNP-solvent interaction energy with the solvation entropy estimates, the free energy of solvation of the AuNP in crowded solutions is computed. The solvation entropy favours the solvation free energy which becomes more favourable for larger effective size of AuNP in crowded solutions relative to that in water. The effective size of AuNP depends on the different propensity of the crowders to adsorb on Au surface, with the smallest crowder (Gly) having the highest propensity inducing the least effective AuNP size as compared to other single crowder solutions. In mixed crowded solutions of amino acids of variable size and chemistry, distinctive local adsorption of the crowders on the gold surface is observed that controls the additive or non-additive crowding effects which govern an increase (in Gly+Ser) or decrease (in Gly+Lys) in nanoparticle effective size respectively. The results shed light into the fundamental understanding of the influence of intracellular crowding on structure of ss-DNA AuNP and plausible employability of crowding as a tool to design programmable self-assembly of functionalized nanoparticles.

Harnessing the power of gold: advancements in anticancer gold complexes and their functionalized nanoparticles.

Cancer poses a formidable challenge, necessitating improved treatment strategies. Metal-based drugs and nanotechnology offer new hope in this battle. Versatile gold complexes and functionalized gold nanoparticles exhibit unique properties like biologically inert behaviour, outstanding light absorption, and heat-conversion abilities. These nanoparticles can be finely tuned for drug delivery, enabling precise and targeted cancer therapy. Their exceptional drug-loading capacity and low toxicity, stemming from excellent stability, biocompatibility, and customizable shapes, make them a promising option for enhancing cancer treatment outcomes and improving diagnostic imaging. Leveraging these attributes, researchers can design more effective and targeted cancer therapeutics. The potential of functionalized gold nanoparticles to advance cancer treatment and diagnostics holds a promising avenue for further exploration and development in the fight against cancer. This review article delves into the finely tuned attributes of functionalized gold nanoparticles, unveiling their potential for application in drug delivery for precise and targeted cancer therapy.

Antibody-labeled gold nanoparticle based resonance Rayleigh scattering detection of S100B.

Traumatic brain injury (TBI) is a sudden brain injury due to an external force that causes a large number of deaths and permanent disabilities every year. S100B has been recognized as a potential objective quantitative biomarker for screening the prognosis of TBI and severe head injury. In this article, an anti-S100B monoclonal antibody was immobilized on cysteamine (Cy) functionalized gold nanoparticles (AuNPs) by EDC-NHS chemistry, which enabled S100B resonance Rayleigh scattering (RRS) detection based on antibody-labeled gold nanoparticles. The prepared conjugates were characterized by ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Based on the specific binding of the antibody and antigen, the RRS intensities at 381 nm and 541 nm wavelengths were significantly enhanced, and thus a dual wavelength overlapping resonance Rayleigh scattering (DWO-RRS) method was established. The scattering intensity of the two overlapping peaks was proportional to the concentration of S100B in the range of 0.05-4.5 ng mL-1 with a detection limit of 0.002 ng mL-1. The proposed DWO-RRS method is time-saving, simple, sensitive, and can be used to determine the concentration of S100B in human serum with satisfactory results, which has a promising application in the early diagnosis of TBI.

Colorimetric detection of oral bacteria using functionalized gold nanoparticles as a plasmonic biosensor array.

Early detection of specific oral bacterial species would enable timely treatment and prevention of certain oral diseases. In this work, we investigated the sensitivity and specificity of functionalized gold nanoparticles for plasmonic sensing of oral bacteria. This approach is based on the aggregation of positively charged gold nanoparticles on the negatively charged bacteria surface and the corresponding localized surface plasmon resonance (LSPR) shift. Gold nanoparticles were synthesized in different sizes, shapes and functionalization. A biosensor array was developed consisting of spherical- and anisotropic-shaped (1-hexadecyl) trimethylammonium bromide (CTAB) and spherical mercaptoethylamine (MEA) gold nanoparticles. It was used to detect four oral bacterial species (Aggregatibacter actinomycetemcomitans, Actinomyces naeslundii, Porphyromonas gingivalis and Streptococcus oralis). The plasmonic response was measured and analysed using RGB and UV-vis absorbance values. Both methods successfully detected the individual bacterial species based on their unique responses to the biosensor array. We present an in-depth study relating the bacteria zeta potential and AuNP aggregation to plasmonic response. The sensitivity depends on multiple parameters, such as bacterial species and concentration as well as gold nanoparticle shape, concentration and functionalization.

Highly specific colorimetric detection based on aggregation of l-cysteine functionalized gold nanoparticles for cypermethrin in water samples.

A fast, simple, and selective colorimetric assay for quantifying cypermethrin in water samples is proposed using l-cysteine functionalized gold nanoparticles (AuNPs@Cyst). Cypermethrin is hydrolyzed by potassium hydroxide to obtain hydrolyzed cypermethrin in the form of 3-phenoxybenzaldehyde by-product (HCy). The detection strategy is based on the aggregation of AuNPs@Cyst caused by hydrogen-bonding recognition between the aldehyde group of HCy and the amine group of l-cysteine on the surface of AuNPs@Cyst. As a result, in the presence of HCy under optimal pH 7, AuNPs@Cyst aggregates within 7 min, exhibiting a distinct color change from red to blue-gray, which can be evaluated with the naked eye and UV-visible spectrophotometry. From FE-TEM image, the stable and spherical AuNPs@Cyst had an average size of 13.8 ± 1.6 nm, and from zeta potential analysis, the charge of AuNPs@Cyst was -25.04 ± 1.66 mV. The surface plasmon resonance band of dispersed AuNPs@Cyst was red shifted from 525 nm to 634 nm when AuNPs@Cyst was aggregated. The absorbance ratio (A634/A525) was linearly related to cypermethrin concentrations from 0.5 to 13.0 mg L-1. The limit of detection was 0.2 mg L-1 and precision, expressed as relative standard deviations (RSDs), ranged from 1.9 to 7.3%. In the presence of interfering pesticides (carbaryl, ethion, profenofos and abamectin), only cypermethrin produced a significantly different response, confirming the selectivity of AuNPs@Cyst. Finally, AuNPs@Cyst was applied to determine cypermethrin in water samples, achieving very satisfied recoveries (>98.6%) and RSDs lower than 6.1%.

Emerging sensing platforms based on Cucurbit[n]uril functionalized gold nanoparticles and electrodes.

Cucurbit[n]urils (CB[n]s, n = 5-8, 10, and 14), synthetic macrocycles with unique host-guest properties, have triggered increasing research interest in recent years. Gold nanoparticles (Au NPs) and electrodes stand out as exceptional substrates for sensing due to their remarkable physicochemical characteristics. Coupling the CB[n]s with Au NPs and electrodes has enabled the development of emerging sensing platforms for various promising applications. However, monitoring the behavior of analytes at the single-molecule level is currently one of the most challenging topics in the field of CB[n]-based sensing. Constructing supramolecular junctions in a sensing platform provides an ideal structure for single-molecule analysis, which can provide insights for a fundamental understanding of supramolecular interactions and chemical reactions and guide the design of sensing applications. This feature article outlines the progress in the preparation of the CB[n] functionalized Au NPs and Au electrodes, as well as the construction and application of supramolecular junctions in sensing platforms, based on the methods of recognition tunneling (RT), surface-enhanced Raman spectroscopy (SERS), single-molecule force spectroscopy (SMFS), and electrochemical sensing (ECS). A brief perspective on the future development of and challenges in CB[n] mediated sensing platforms is also covered.