Copper foam in situ loaded with precious metal nanoparticles as transmission SEIRAS substrate for rapid detection of dithiocarbamate pesticides

Tailoring Infrared Light-Molecule Coupling for Highly Sensitive Cortisol Detection Employing Aptamer-Conjugated Gold Nanonails

Chemically synthesized gold nanoantennas possess easy processability, low cost, and suitability for large-area fabrication, making them advantageous for surface-enhanced infrared (SEIRA) biosensing. Nevertheless, current gold nanoantennas face challenges with limited enhancement of biomolecular signals that hinder their practical applications. Here, we demonstrate that the coupling rate between antennas and molecules critically impacts the enhancement of molecular signals based on temporal coupled mode theory. To improve this coupling rate, we synthesized gold nanonails with sharp tips, significantly amplifying the localized electric fields of antenna resonance modes. Modulating the nanonail aspect ratio allows us to tailor antenna resonance frequencies to match molecular vibrational frequencies. Additionally, we introduced specific aptamers on antenna surfaces through solution exchange methods to control the antenna-molecule distances. These combined strategies enabled noninvasive, label-free detection with high sensitivity for the biomarker cortisol. Experiments revealed 3 orders of magnitude enhancement in cortisol detection levels upon increasing coupling efficiency, achieving a detection limit of 0.1 ng/mL, notably lower than the normal cortisol concentration in human saliva (0.398 ng/mL). In addition to demonstrating a novel strategy for cortisol detection, this study provides a viable approach to biomarker detection for future applications in disease diagnosis and human health monitoring.

Effect of Gold Nanoparticles on Luminescence Enhancement in Antibodies for TORCH Detection

PURPOSES

To explore the optimization method and application of Au-NP-enhanced luminol--H2O2 luminescence system in TORCH (TOX, RV, CMV, HSVI, and HSVII) detection.

METHOD

4.5 × 10-5 mmol/L gold nano solution was prepared with chloroauric acid as the reducing agent and trisodium citrate as the stabilizer. After curing for 3 days, Au NPs participate in the luminal-H2O2 luminescence system to detect TORCH antibodies and establish the cut off value. SPSS 18.0 software was used to analyze the TORCH antibodies detected by the nano-gold-enhanced luminol luminescence method and TORCH kit. Additionally, its detection performance is studied.

RESULTS

The results of a paired t-test for the absorbance values of samples with and without gold nanoparticles showed that there were statistically significant differences (p < 0.001) between the two methods in the detection of TOX, RV, CMV, HSVI, and HSVII. The luminescence values with the addition of gold nanoparticles were significantly higher than those without gold nanoparticles. Using the Au NP-luminol-H2O2 chemiluminescence method, 127 serum samples were tested for TORCH antibodies. The sensitivities were 84.6%, 83.3%, 90.9%, 85.7%, and 84.6%, while the specificities were 94.7%, 96.5%, 96.6%, 97.3%, and 95.6%, respectively. The sensitivity and specificity of the chemiluminescence method enhanced by gold nanoparticles are significantly improved compared to the chemiluminescence method without enhancers.

CONCLUSIONS

Au NPs participate in the luminal-H2O2 luminescent system. The absorbance, sensitivity, and specificity of TORCH antibodies show that Au NPs can enhance the luminol-H2O2 luminescent system. Au NP-luminol-H2O2 luminescence system has broad application prospects in the detection of eugenics.

CoMnOx Nanoflower-Based Smartphone Sensing Platform and Virtual Reality Display for Colorimetric Detection of Ziram and Cu2

Transition metal doping is an ideal strategy to construct multifunctional and efficient nanozymes for biosensing. In this work, a metal-doped CoMnOx nanozyme was designed and synthesized by hydrothermal reaction and high-temperature calcination. Based on its oxidase activity, an "on-off-on" smartphone sensing platform was established to detect ziram and Cu2+. The obtained flower-shaped CoMnOx could exhibit oxidase-, catalase-, and laccase-like activities. The oxidase activity mechanism of CoMnOx was deeply explored. O2 molecules adsorbed on the surface of CoMnOx were activated to produce a large amount of O2·-, and then, O2·- could extract acidic hydrogen from TMB to produce blue oxTMB. Meanwhile, TMB was oxidized directly to the blue product oxTMB via the high redox ability of Co species. According to the excellent oxidase-like activity of CoMnOx, a versatile colorimetric detection platform for ziram and Cu2+ was successfully constructed. The linear detection ranges for ziram and Cu2+ were 5~280 μM and 80~360 μM, and the detection limits were 1.475 μM and 3.906 μM, respectively. In addition, a portable smartphone platform for ziram and Cu2+ sensing was established for instant analysis, showing great application promise in the detection of real samples including environmental soil and water.

Hyphenated liquid electrode glow discharge-dielectric barrier discharge molecular emission spectrometry for determination of dithiocarbamates

A hyphenated liquid electrode glow discharge (LEGD)-dielectric barrier discharge (DBD) molecular emission spectrometer was constructed and used as a novel liquid chromatography (LC) detector for dithiocarbamates (DTC) determination. The LEGD was used as an acidolysis reactor for the in-situ transformation of DTCs into CS2 with high efficiencies of 74.11-97.98%. The DBD was used to excite CS2 gas to generate a specific molecular emission at 257.94 nm. The linear correlation coefficient of the method was > 0.99 from 1 to 200 μg mL-1. The detection limits ranged from 0.1 to 0.3 μg mL-1 with 76-119% recovery and relative standard deviations of 0.2-8.5%. Moreover, the hyphenated microplasma spectrometer achieved low power consumption, low temperature, immediate acidolysis, and high transformational efficiency, and can detect each DTC when combined with LC.

Deep eutectic solvent-based adhesive tape extraction combined with enzyme inhibition assay for the determination and distinction of dithiocarbamate pesticides in food samples

A simple, green extraction method of dithiocarbamate (DTC) pesticides in food samples was developed using adhesive tapes and a green deep eutectic solvent (DES). A rapid and convenient determination and distinction method of DTC pesticides was established using tyrosinase inhibition assay. First, DTC pesticides were extracted by pasting and peeling off the adhesive tape, then eluted by the DES synthesized from xylitol and ethylene glycol. Second, determination of DTC pesticides was conducted by inhibiting the activity of tyrosinase which can catalyze the oxidation of catechol. Less colored products were generated in the reaction system (tyrosinase, catechol, and 4-aminoantipyrine), leading to weak absorbance. In addition, different DTC pesticides (ziram, propineb, zineb, mancozeb, thiram, metiram, and ferbam) were successfully distinguished by sensor arrays (tyrosinase, phenolic compounds, and 4-aminoantipyrine) through principal component analysis. The limit of detection was found to be 0.2 μg kg^-1, and the limit of quantification was 0.6 μg kg^-1. The recoveries ranging from 89.4% to 103.8% were obtained in vegetable, fruit, and cereal, with a relative standard deviation of less than 4.2%. The method is simple, rapid, and convenient and shows good application prospects in the determination of pesticides in a variety of food samples.

Ameliorating SERS Sensitivity for Pesticide Malathion Detection with Synergistic Boosting Effect by Hydrogen Cations and Chloride Anions

Although SERS has been widely recognized as one of the highly sensitive analytical methods that can be deployed in the field with high sensitivity and short analysis time, reports regarding the fast determination of malathion at low concentrations are still scarce. Here, in this work, the solution pH and various halogen co-adsorbates were explored to promote the SERS signal of malathion using the citrate-reduced Ag NPs. It was found that chloride anions were the most efficient signal booster among the three halogen ions screened. Further examination of the SERS profile of the malathion in the presence of different halogen species found that the stretching mode of the P-S bond shifted to a lower frequency with Cl^-, which may imply closer (and stronger) binding of malathion to the Ag NPs. This concurs with literature reports that halogen ions could facilitate the adsorption of a certain analyte onto the SERS substrate. In addition, hydrogen ions showed a synergistic effect on SERS signal enhancement when combined with chloride anions. At optimum conditions, the malathion could be detected with a limit of detection (LOD) of 3 ppb. Malathion-spiked cherry tomatoes and oranges were analyzed, and the recovery rates were found to be within 85-100%.

Identification of milk quality and adulteration by surface-enhanced infrared absorption spectroscopy coupled to artificial neural networks using citrate-capped silver nanoislands

Milk is one of the most important multicomponent superfoods owing to its rich macronutrient composition. It requires quality control at all the production stages from the farm to the finished products. A localized surface plasmon resonance optical sensor based on a citrate-capped silver nanoparticle (Cit-AgNP)–coated glass substrate was developed. The fabrication of such sensors involved a single-step synthesis of Cit-AgNPs followed by surface modification of glass slides to be coated with the nanoparticles. The scanning electron microscope micrographs demonstrated that the nanoparticles formed monolayer islands on glass slides. The developed surface-enhanced infrared absorption spectroscopy (SEIRA) sensor was coupled to artificial neural networking (ANN) for the qualitative differentiation between cow, camel, goat, buffalo, and infants’ formula powdered milk types. Moreover, it can be used for the quantitative determination of the main milk components such as fat, casein, urea, and lactose in each milk type. The qualitative results showed that the obtained FTIR spectra of cow and buffalo milk have high similarity, whereas camel milk resembled infant formula powdered milk. The most difference in FTIR characteristics was evidenced in the case of goat milk. The developed sensor adds several advantages over the traditional techniques of milk analysis using MilkoScan™ such as less generated waste, elimination of pre-treatment steps, minimal sample volume, low operation time, and on-site analysis.