Determination of genotoxic impurities of aromatic aldehydes in pharmaceutical preparations by high performance liquid chromatography after derivatization with N-Cyclohexyl-4-hydrazino-1,8-naphthalenediimide.

The detection of aromatic aldehydes, considered potential genotoxic impurities, holds significant importance during drug development and production. Current analytical methods necessitate complex pre-treatment processes and exhibit insufficient specificity and sensitivity. This study presents the utilization of naphthalenediimide as a pre-column derivatisation reagent to detect aromatic aldehyde impurities in pharmaceuticals via high-performance liquid chromatography (HPLC). We screened a series of derivatisation reagents through density functional theory (DFT) and investigated the phenomenon of photoinduced electron transfer (PET) for both the derivatisation reagents and the resulting products. Optimal experimental conditions for derivatisation were achieved at 40 °C for 60 min. This approach has been successfully applied to detect residual aromatic aldehyde genotoxic impurities in various pharmaceutical preparations, including 4-Nitrobenzaldehyde, 2-Nitrobenzaldehyde, 1,4-Benzodioxane-6-aldehyde, and 5-Hydroxymethylfurfural. The pre-column derivatisation method significantly enhanced detection sensitivity and reduced the limit of detection (LOD), which ranged from 0.002 to 0.008 µg/ml for the analytes, with relative standard deviations < 3 %. The correlation coefficient (R2) >0.998 demonstrated high quality. In chloramphenicol eye drops, the concentration of 4-Nitrobenzaldehyde was measured to be 8.6 µg/mL below the specified concentration, with recoveries ranging from 90.0 % to 119.2 %. In comparison to existing methods, our work simplifies the pretreatment process, enhances the sensitivity and specificity of the analysis, and offers comprehensive insights into impurity detection in pharmaceutical preparations.

Characterization of Volatile Organic Compounds in Kiwiberries (Actinidia arguta) Exposed to High Hydrostatic Pressure Processing by HS-SPME/GC-MS.

HS-SPME/GC-MS analysis was carried out to characterize the profile of volatile organic compounds (VOCs) in kiwiberry cultivars (Geneva and Weiki) exposed to high hydrostatic pressure (HHP) (450-550-650/5 and 15 min). The sum of individual VOCs in Geneva (6.493 mg/kg) and Weiki (11.939 mg/kg) samples was found to be significantly reduced after processing, particularly for pressurization conditions of 650 MPa/15 min (decrease of 62%) and 550 MPa/15 min (decrease of 84%), respectively. On the other hand, Geneva and Weiki exposed to 450 MPa/5 min manifested the lowest loss in the sum of the VOCs. Geneva exposure to 450 MPa/5 min led to an increase in the hexanal (r = 0.782) and linalool (r = 0.806) content. Sample pressurization (450 MPa/15 min) promoted the formation of methyl butanoate, ethyl hexanoate, and cis-geraniol, simultaneously increasing the benzaldehyde (r = 0.886) concentration. However, the treatment of Weiki at 450 MPa/5 min favored trans-2-heptenal (r = 0.999) and linalool (r = 0.970) formation, as well as the (-)-terpinen-4-ol (r = 0.848) and geraniol (r = 0.694) content. Ethyl butanoate, hexanal, and 1-octen-3-ol were highly concentrated in the HHP-treated (450 MPa/5 or 15 min) Weiki. Pressurization decreased the terpenoid contribution, but also increased the contribution of alcohols and aldehydes to the overall VOC number in both tested cultivars.

Whole-genome analysis guided molecular mechanism of cyanogenic glucoside degradation by yeast isolated from Prunus mume fruit syrup.

Consumption of fermented Prunus mume fruit (maesil) sugar syrup raise a health concern due to the presence of the cyanogenic glucoside amygdalin. The goal of the present study was to investigate the amygdalin degradation potential and genome profile of the native microbes found in maesil syrup. The microbial profile analysis revealed that yeast is the predominant microorganism native to maesil syrup and that the isolated yeast cells showed a remarkable potential for amygdalin reduction (99.7%). Moreover, the reduction in amygdalin was inversely proportional to the growth of the isolated yeast. The whole-genome analysis revealed that the isolated yeast is Zygosaccharomyces rouxii (genome size 10 Mb, 39.25% of GC content). Of the 5250 genes (64.88%) predicted in the Z. rouxii genome, 5245 (99.90%) were annotated using NCBI Non-Redundant, UniProt, and InterProScan databases. The genome of the isolated Z. ruoxii harbored 2.03% of repeats and 0.68% of non-coding RNAs. Protein prediction indicated that ß-glycosidases and hydroxynitrile lyase may play a key role in amygdalin degradation. The predicted degradation initiated by ß-glycosidases that hydrolyze α-glucosidic bonds of amygdalin results in α-hydroxy nitriles (cyanohydrins) that are subsequently converted into carbonyl compounds (benzaldehyde) and hydrogen cyanide catalyzed by hydroxynitrile lyases. Present findings provide valuable data for constructing engineered microorganisms that can degrade amygdalin. Further analysis of Z. rouxii may elucidate the exact mechanism of amygdalin reduction in the production of maesil syrup.

Volatile profiles of commercial vetch prepared via different processing methods.

Vicia sativa (Common Vetch) is currently an underutilised leguminous crop species with high protein content and superior drought tolerance. This study aimed to understand the mechanisms behind vetch flavor development following processing to facilitate its uptake as a future source of dietary protein. A total of 95 volatile compounds were identified by solid-phase microextraction gas chromatography-mass spectrometry (SPME GC-MS) for a range of vetches processed by dehulling, soaking, germination, microwaving, and fermentation.2-pentyl furan, benzyl alcohol, benzaldehyde, 1-octen-3-ol and 1-hexanol were found to be characteristic aroma compounds of V. sativa. Analysis of a V. sativa landrace demonstrated significant intraspecies variation in volatile abundance, three-fold that of commercial varieties. Both natto and tempeh fermentation produced significant quantities of alcohols, esters, and carboxylic acids with specifically natto generating significant pyrazines. Concentrations of 1-octen-3-ol significantly decreased after tempeh fermentation indicating its potential to reduce documented off flavor generating volatiles within V. sativa.

Effect-directed profiling of 32 vanilla products, characterization of multi-potent compounds and quantification of vanillin and ethylvanillin.

Food testing is of great importance to the food industry and organizations to verify the authenticity claims, to prove the quality of raw materials and products, and to ensure food safety. The market prices of vanilla differed by a factor of about 20 in the last three decades. Therefore the risk of adulteration and counterfeiting of vanilla products is high. Instead of commonly used target analyses and sum parameter assays, a complementary non-target multi-imaging effect-directed screening was developed, which provided a new perspective on the wide range of vanilla product qualities on the market. Planar chromatography was combined with effect-directed assays, and the obtained biological and biochemical profiles of 32 vanilla products from nine different categories revealed a variety of active ingredients. Depending on the region, typical vanilla product profiles and activity patterns were obtained for pods, tinctures, paste (inner part), oleoresin and powders. However, some vanilla products showed additional active compounds and a different intensity pattern. The vanilla product profiles substantially differed from those of vanilla aroma or products containing synthetic vanillin or vanilla-flavored food products. Bioactive compounds of interest were online eluted and further characterized via HPTLC-HRMS, which allowed their tentative assignment. After purchase of the standards, these were successfully confirmed by co-chromatography. Quantification of vanillin across nine different product categories revealed levels ranging from 1 µg/g to 36 mg/g with a mean repeatability of 1.9%. The synthetic ethylvanillin was not detected in the investigated samples in significant concentrations. The assessment of differences in the activity patterns pointed to highly active compounds, which were not detected at UV/Vis/FLD but first via the biological and enzymatic assays. This effect-directed profiling bridges the gap from analytical food chemistry to food toxicology, and thus, makes an important contribution to consumer safety. In the same way, it would accelerate investigations for Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) according to Regulation (EC) No. 1907/2006.

Honey Phenolic Compound Profiling and Authenticity Assessment Using HRMS Targeted and Untargeted Metabolomics.

Honey consumption is attributed to potentially advantageous effects on human health due to its antioxidant capacity as well as anti-inflammatory and antimicrobial activity, which are mainly related to phenolic compound content. Phenolic compounds are secondary metabolites of plants, and their content in honey is primarily affected by the botanical and geographical origin. In this study, a high-resolution mass spectrometry (HRMS) method was applied to determine the phenolic profile of various honey matrices and investigate authenticity markers. A fruitful sample set was collected, including honey from 10 different botanical sources (n = 51) originating from Greece and Poland. Generic liquid-liquid extraction using ethyl acetate as the extractant was used to apply targeted and non-targeted workflows simultaneously. The method was fully validated according to the Eurachem guidelines, and it demonstrated high accuracy, precision, and sensitivity resulting in the detection of 11 target analytes in the samples. Suspect screening identified 16 bioactive compounds in at least one sample, with abscisic acid isomers being the most abundant in arbutus honey. Importantly, 10 markers related to honey geographical origin were revealed through non-targeted screening and the application of advanced chemometric tools. In conclusion, authenticity markers and discrimination patterns were emerged using targeted and non-targeted workflows, indicating the impact of this study on food authenticity and metabolomic fields.

Simultaneous determination of vanillin, ethyl vanillin and methyl vanillin in Chinese infant food and other dairy products by LC-MS/MS.

An efficient and simple method for determining vanillin, methyl vanillin and ethyl vanillin in milk and dairy products was developed using a liquid-liquid extraction (LLE) procedure coupled to high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Different extraction procedures were tested and optimised by spiking three vanillin compounds into a blank matrix in which none of any food additives were detected, and the extraction with acetonitrile solution and n-hexane as cleaning sorbent allowed an efficient recovery of 87.6-101.7% with RSDs less than 5%. The limit of detection (LOD) ranged from 6.2 to 20.1 µg/kg. High sensitivity, accuracy and selectivity were found for the in-house validated method, which can eliminate the interferences from complicated matrices effectively, and fulfil the quality criteria for routine laboratory application for real samples. The developed method was then finally applied to screen the three analytes in 65 milk and dairy products including infant formula milk powders from local markets to check for compliance with Chinese Regulation. Concentrations of the total vanillin and ethyl vanillin ranged from 0.0323 to 246.3 mg/kg, which is within the limits of Chinese regulations.

Decalepis salicifolia (Bedd. ex Hook. f.) Venter: A steno-endemic and critically endangered medicinal and aromatic plant from Western Ghats, India.

Decalepis salicifolia (Bedd. ex Hook. f.) Venter is a potential medicinal and highly aromatic plant species confined to the southernmost part of the Western Ghats of India. The plant is well known for its traditional uses among the various tribal communities of south India. The tubers of the plant possess characteristic vanillin-like aroma due to the presence of the compound 2-hydroxy-4-methoxybenzaldehyde. The tubers are used to substitute Hemidesmus indicus in various herbal formulations. The plants in the wild are continuously uprooted for their roots, leading to the irreversible destruction of the whole plant. The resulting tremendous loss of populations in the wild led to the species being declared as critically endangered by IUCN. Our group is working on the various aspects of this species including population status, distribution mapping, prospection, and conservation management. In the present review, we have brought out the available information till date on D. salicifolia, including taxonomy, ethno-medicinal uses, phytochemistry, pharmacology, population status, and conservation efforts along with research gap and lacunae to provide direction for further research into this less explored medicinal and aromatic plant.

Target profiling of beer styles by their iso-α-acid and phenolic content using liquid chromatography-quadrupole time-of-flight-mass spectrometry.

Beer styles show wide variation in color, flavor, and clarity, due to differences in their chemical content. Some of the major flavor compounds in beer are isomerized alpha acids and phenolic compounds. These were investigated as potentially discerning features between beer styles. A selection of 32 American beers covering five styles was analyzed using liquid chromatography quadrupole time-of-flight mass spectrometry, which resulted in high mass accuracy chromatograms of the studied analytes. Distinctions between the presence or relative concentrations of certain compounds were observed and related back to brewing ingredients and procedures. For example, vanillin was only observed in stout beers due to the use of roasted barley malts for brewing, while chlorogenic acid isomers were found in two sours at relatively high concentrations (189 and 34 mg/L) because of the fruits used to flavor the beers. Distinctions were further confirmed using multivariate analysis techniques, which separated three of the five beer styles (India pale ales, stouts, and sours).

The responses of Salmonella enterica serovar Typhimurium to vanillin in apple juice through global transcriptomics.

Salmonella enterica serovar Typhimurium can survive some extreme environment in food processing, and vanillin generally recognized as safe is bactericidal to pathogens. Thus, we need to explore the responses of S. Typhimurium to vanillin in order to apply this antimicrobial agent in food processing. In this study, we exposed S. Typhimurium to commercial apple juice with/without vanillin (3.2 mg/mL) at 45 °C for 75 min to determine the survival rate. Subsequently, the 10-min cultures were selected for transcriptomic analysis. Using high-throughput RNA sequencing, genes related to vanillin resistance and their expression changes of S. Typhimurium were identified. The survival curve showed that S. Typhimurium treated with vanillin were inactivated by 5.5 log after 75 min, while the control group only decreased by 2.3 log. Such a discrepancy showed the significant antibacterial effect of vanillin on S. Typhimurium. As a result, 265 differentially expressed genes (DEGs) were found when coping with vanillin, among which, 225 showed up-regulation and 40 DEGs were down-regulated. Treated with vanillin, S. Typhimurium significantly up-regulated genes involved in cell membrane, acid tolerance response (ATR) and oxidative stress response, cold shock cross-protection, DNA repair, virulence factors and some key regulators. Firstly, membrane-related genes, including outer membrane (bamE, mepS, ygdI, lolB), inner membrane (yaiY, yicS) and other proteins (yciC, yjcH), were significantly up-regulated because of the damaged cell membrane. Then, up-regulated proteins associated with arginine synthesis (ArgABCDIG) and inward transportation (ArtI, ArtJ, ArtP and HisP), participated in ATR to pump out the protons inside the cell in this scenario. Next, superoxide stress response triggered by vanillin was found to have a significant up-regulation as well, which was controlled by SoxRS regulon. Besides, NADH-associated (nuoA, nuoB, nuoK, nadE, fre and STM3021), thioredoxin (trxA, trxC, tpx and bcp) and glutaredoxin (grxC and grxD) DEGs led to the increase of the oxidative stress response. Cold shock proteins such as CspA and CspC showed an up-regulation, suggesting it might play a role in cross-protecting S. Typhimurium from vanillin stress. Furthermore, DEGs in DNA repair and virulence factors, including flagellar assembly, adhesins and type III secretion system were up-regulated. Some regulators like fur, rpoE and csrA played a pivotal role in response to the stress caused by vanillin. Therefore, this study sounds an alarm for the risks caused by stress tolerance of S. Typhimurium in food industry.

Identification of a non-host semiochemical from miniature pinscher, Canis lupus familiaris, that repels Rhipicephalus sanguineus sensu lato (Acari: Ixodidae).

It is already known that the beagle breed of domestic dogs produces semiochemicals capable of repelling the brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.). With a view to discovering new non-host semiochemicals as tick repellents, we compared the semiochemicals produced by a putative tick-resistant breed of dog, miniature pinscher, with known tick-resistant (beagle) and tick-susceptible (English cocker spaniel) breeds. Two non-host compounds produced by beagles, i.e. 2-hexanone and benzaldehyde, were shown to be present in samples collected from all three breeds. Furthermore, two compounds, 6-methyl-5-hepten-2-one and 1,2,4-trimethylbenzene, were found in higher amounts in samples collected from miniature pinscher dogs. The mean amounts of benzaldehyde, 2-hexanone and 1,2,4-trimethylbenzene were similar for beagles and miniature pinschers (P > 0.05) and higher than the means observed for cocker spaniels (P < 0.05), whereas the mean amount of 6-methyl-5-hepten-2-one produced by miniature pinschers was significantly higher (P < 0.05) than for the other breeds of dogs. In Petri-dish assays with adult R. sanguineus s.l., 6-methyl-5-hepten-2-one was repellent for all observation periods evaluated for the two highest concentrations (0.100 and 0.200 mg.cm-2, P < 0.01). The obtained results support our hypothesis that miniature pinschers are a tick-resistant dog breed and agree with previous observations of miniature pinschers being the breed least parasitized by ticks. Furthermore, the non-host semiochemical 6-methyl-5-hepten-2-one has potential to be developed for use as a repellent for the protection of susceptible dogs from R. sanguineus s.l. ticks.

Core-satellite surface imprinting polymer-based pipette tip solid-phase extraction for the colorimetric determination of pyrethroid metabolite.

A core-satellite-structured surface molecularly imprinted polymer has been synthesized for the enrichment of 3-phenoxybenzaldehyde by pipette tip solid-phase extraction (SPE). In a typical sol-gel process, two silane reagents as functional monomers and 3-phenoxybenzoic acid as the dummy template, the surface imprinting layer was coated on the core-satellite silica microsphere, which formed the core-satellite-structured molecularly imprinted polymer (CSMIP). Compared to the silica-based core-shell ones, this CS-MIP exhibits a stunning surface area (142 m2 g-1) in micrometer size and also overcomes the aggregation trends of core-shell structure in nanoscale. Taking potassium permanganate solution as oxidizer and indicator, the adsorbed 3-phenoxybenzaldehyde can be a quantitatively determined through redox reaction after elution. The value of maximum adsorption capacity and imprinting factor of CS-MIP were calculated to be 87.5 µg mg-1 and 2.13, respectively. These CS-MIPs were packed into commercial pipette tip as the sorbent to concentrate 3-phenoxybenzaldehyde. Under the optimum condition, a liner relationship was achieved in the range 0.200 to 1.00 µg mL-1 and the limit of detection was 81 ng mL-1. Moreover, this customized SPE device exhibits good adsorption capability after six sequential adsorption-desorption cycles, and the high recovery range of 92.2~99.7% of spiked tap water assay demonstrated its potential application for real sample analysis. Graphical abstract Schematic presentation of core-satellite molecularly imprinted polymer preparation strategy and customized pipette tip solid-phase extraction device.

Voltammetric determination and electrochemical behavior of vanillin based on 1H-1,2,4-triazole-3-thiol polymer film modified gold electrode.

Poly(1H-1,2,4-triazole-3-thiol) (poly(T3T)) conductive film was coated successfully on the gold electrode (Au). The electrochemical behavior of vanillin (VAN) was studied on the 1H-1,2,4-triazole-3-thiol-Au (T3T-Au) electrode. The determination of VAN was performed on the T3T-Au electrode using a differential pulse voltammetry (DPV) technique. In order to detect the concentration of VAN, suitable supporting electrolyte solution and pH value were determined. At pH 3 in HClO4 solution, the anodic peak current of VAN obtained with the T3T-Au electrode is 4.3 times greater than the bare Au electrode. The response oxidation peak current and concentration of VAN showed a good linear relationship in the range of 0.1-11.3 µM. The limit of detection was found as 0.04 µM. Besides, the reproducibility, repeatability, stability, and interference measurements were also assayed. This sensor was applied successfully for the detection of VAN in synthetic samples and various food samples.

Stability and Extraction of Vanillin and Coumarin under Subcritical Water Conditions.

In order to facilitate the development of the green subcritical water chromatography technique for vanillin and coumarin, the stability of the compounds under subcritical water conditions was investigated in this work. In addition, their extraction from natural products was also studied. The stability experiments were carried out by heating the mixtures of vanillin and water or coumarin and water at temperatures ranging from 100 °C to 250 °C, while subcritical water extractions (SBWE) of both analytes from vanilla beans and whole tonka beans were conducted at 100 °C to 200 °C. Analyte quantification for both stability and extraction studies was carried out by HPLC. After heating for 60 min, vanillin was found to be stable in water at temperatures up to 250 °C. While coumarin is also stable at lower temperatures such as 100 °C and 150 °C, it undergoes partial degradation after heating for 60 min at 200 °C and higher. The results of this stability study support green subcritical water chromatographic separation and extraction of vanillin and coumarin at temperatures up to 150 °C. The SBWE results revealed that the extraction efficiency of both analytes from vanilla beans and tonka beans is significantly improved with increasing temperature.

Biosynthesis of Benzylic Derivatives in the Fermentation Broth of the Edible Mushroom, Ischnoderma resinosum.

Employing isotope incubation studies, the biosynthetic pathway leading to a series of benzylic derivatives was elucidated in the fermentation broth of the edible mushroom Ischnoderma resinosum (P. Karst). Twenty-six hydroxy- and methoxy- benzylic derivatives were screened by gas chromatography-mass spectrometry (GC-MS) of which 13 were detected in the culture media. Results from the isotope incubation studies showed the transformation of both benzyl alcohol and benzoic acid into benzaldehyde. Benzaldehyde was then converted into 4-methoxybenzaldehyde via hydroxylation and subsequent methylation of the 4-C position. The resulting 4-methoxybenzaldehyde was then hydroxylated in the 3-C position followed by methylation into 3,4-dimethoxybenzaldehyde. Based on these findings, a novel metabolic scheme for the biosynthesis of benzylic derivatives in I. resinosum was proposed. The knowledge of the biosynthetic pathway was utilized to produce 4-hydroxy-3-methoxybenzaldehyde (vanillin) from 4-hydroxy-3-methoxybenzoic acid (vanillic acid). This is the first report to elucidate the biosynthetic pathway of benzyl derivatives and production of vanillin from I. resinosum.

Aroma perceptual interactions of benzaldehyde, furfural, and vanillin and their effects on the descriptor intensities of Huangjiu.

Aldehydes are important in the aroma of Huangjiu and contribute the almond and sweet aromas to Huangjiu. The perceptual interactions of 3 important aldehyde compounds were investigated using S-curves. Three volatiles, benzaldehyde, furfural, and vanillin, reduced the "olfactory threshold" of an aromatic reconstitution (AR) from 24.2 mL/L to 11.0, 14.8 and 9.00 mL/L (AR/matrix, mL/L), respectively. Furthermore, synergistic effects were observed in a benzaldehyde and furfural mixture (71:29, m/m) wherein the overall olfactory threshold value was reduced from 17.0 mL/L to 2.60 mL/L. In addition, these compounds could increase or decrease the intensity of sensory descriptors even at subthreshold concentrations, and the profiles confirmed that they had synergistic effects with other compounds in Huangjiu. In particular, when benzaldehyde and furfural were present in the actual concentration ratio determined in Huangjiu (71:29, m/m), the enhancement of the Qu and sweet aromas became significant, which indirectly indicated synergy between them.

Chemical profiling and cytotoxic activity of 150-year old original sample of Jerusalem Balsam.

Herbal formulations have been used in ethnomedicine and pharmacy around the world for thousands of years. One of them is Jerusalem Balsam (JB), which came into use in the seventeenth century. Today, people still produce and use it regularly as prophylactic supplement. JB has been widely used in Europe since the nineteenth century, as a remedy possessing antibacterial, antifungal and anti-inflammatory activities. The composition of the product was not known, although possible formulations were reported. In this study the original sample, which dated back to 1870, was investigated for chemical composition and cytotoxic activity. The obtained results were compared with results from more recently produced samples. Several tests were carried out, namely GC-MS, UPLC-PDA-Q-TOF-MS and MTT. Only the 150-year old sample showed a significant cytotoxic activity on cancer cell lines. At a concentration of 125 µg/mL after 72 h of incubation, the original sample inhibited almost 90% of cell metabolic activity, while contemporary samples showed none or little activity. None of the tested samples showed a significant impact on normal cells. These results may be attributed to the activities of benzoic acid and its derivatives, cinnamic acid derivatives, vanillin, group of sesquiterpenes and cembrene.

Dispersive solid-phase extraction and dispersive liquid-liquid microextraction for the determination of flavor enhancers in ready-to-eat seafood by HPLC-PDA.

The dispersion solid-phase microextraction (DSPE) combined with dispersion liquid-liquid microextraction (DLLME) was developed as a rapid, simple and effective pretreatment method for the determination of flavor enhancers (maltol, ethyl maltol, vanillin, methyl vanillin, ethyl vanillin) of ready-to-eat seafood products (dried squid, baked squid, fried fish, steamed abalone). Under the optimized DSPE-DLLME method, the developed method exhibited low limits of quantitation (0.20-0.50 µg g-1) and excellent linearity (R2 ≥ 0.995). The recoveries of flavor enhancers in the actual samples were 83.7%-114.9%. Compared with traditional pretreatment methods, the developed DSPE-DLLME method was rapid (17 min) and easy to determine the flavor enhancers by high performance liquid chromatography with photodiode array detector (HPLC-PDA). In the actual samples, creamy compounds such as vanillin, methyl vanillin and ethyl vanillin were hardly found. However, the flavor compounds produced by thermal reactions such as maltol (except for dried squid 3) and ethyl maltol were present in all samples.

Ketjen black/ferrocene dual-doped MOFs and aptamer-coupling gold nanoparticles used as a novel ratiometric electrochemical aptasensor for vanillin detection.

In this work, a facile ratiometric electrochemical aptasensor was developed towards sensitive and selective detection of vanillin, based on Ketjen black/ferrocene dual-doped zeolite-like MOFs (Fc-KB/ZIF-8) and electrodeposited gold nanoparticles (AuNPs) coupling with DNA aptamer. Fc-KB/ZIF-8 composites were prepared via one-pot solvothermal reaction and drop-coated on glassy carbon electrode (GCE) surface to form Fc-KB/ZIF-8@GCE. AuNPs were in-situ electro-deposited on the modified GCE. 5'-SH terminated aptamer of vanillin was combined with AuNPs via Au-S coupling to form aptamer-AuNPs/Fc-KB/ZIF-8@GCE as a new sensing platform. Under optimal conditions, electrochemical (square wave voltammetry) curves of this sensing platform were measured in electrolyte solutions containing vanillin. With increase of vanillin concentration (Cvan), vanillin had an increased peak current intensity (Ivan, as response signal). Fc doped into ZIF-8 had slight changes in its peak current intensity (IFc, as reference signal). There is a well plotting linear relationship between Ivan/IFc and the logarithm of Cvan ranging from 10 nM to 0.2 mM, with a low limit of detection of 3 nM. The aptamer-AuNPs/Fc-KB/ZIF-8@GCE was applied as a ratiometric electrochemical aptasensor of vanillin. This aptasensor had sensitive and selective electrochemical signal responses on vanillin, over potential interferents. This aptasensor enabled vanillin detection in real food samples, showing high detection performance. Experimental results testified that this aptasensor had high reliability and practicability for vanillin determination in real samples.

Detection of Exhaled Volatile Organic Compounds Improved by Hollow Nanocages of Layered Double Hydroxide on Ag Nanowires.

To detect biomarkers from human exhalation, air flow dynamics on the nanoparticle surface were explored by a surface-enhanced Raman scattering (SERS) sensor. A hollow Co-Ni layered double hydroxide (LDH) nanocage on Ag nanowires (Ag@LDH) was prepared. Ag nanowires provided amplified Raman signals for trace determination; hollow LDH nanocages served as the gaseous confinement cavity to improve capture and adsorption of gaseous analytes. The Raman intensity and logarithmic analyte concentration exhibit an approximately linear relationship; the detection limit of SERS sensors for aldehyde is 1.9×10-9 v/v (1.9 ppb). Various aldehydes in mixed mimetic gas are distinguished by Raman spectra statistical analysis assisted by multivariate methods, including principal component analysis and hierarchical cluster analysis. The information was recorded in a barcode, which can be used for the design and development of a desktop SERS sensor analysis system for large-scale lung cancer detection.