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In this study, we developed an in-package colorimetric paper to monitor the ripeness of kiwifruit by detecting the release of aldehydes. Strongly hydrophobic composite films were prepared using chitosan as the matrix and beeswax as an additive. A piece of cellulose paper containing methyl red and bromocresol violet as color indicators was heat-sealed between two hydrophobic films to protect the indicators from the effects of fruit respiration and transpiration. The nucleophilic addition reaction between aldehydes and OH - (Cannizzaro reaction) changes the pH in the paper and triggers a color change in the indicators. As the kiwifruit ripens, the colorimetric paper changes from bluish-purple to dark red and then gradually to red. A mobile phone application was further used to measure the RGB values and link them to kiwifruit ripeness. This intelligent paper can be used for the accurate and convenient monitoring of produce in real time., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Accurate, sensitive, and selective on-spot screening of volatile aldehydes as lung cancer biomarkers is of vital significance for preclinical diagnosis and treatment guidance of cancers. However, the common methods of sensing biomarkers are limited by the fact that they are time-consuming, require professional personnel, and have complex matrixes. Here, we developed a smart vapor generation paper-based thin-film microextraction system capable of both sensitive on-field fluorescence detection and accurate surface-enhanced Raman spectroscopy (SERS) quantification of volatile benzaldehyde (BA) by utilizing stimuli-responsive core-shell gold nanorod (GNR) quantum dot (QD)-embedded metal-organic framework (MOF) structures. The amino-modified GNRs and carboxyl-capped QDs can directly assemble with each other by electrostatic interaction, which leads to an almost complete emission quenching of QDs. The addition of BA molecules destroys the GNRs-QD assemblies due to the Schiff base reactions between the amine group of 4-mercaptonoaniline and the aldehyde moiety of BA, resulting in the increase of the fluorescence and Raman signal of hybrid systems, which enables the visualization of BA with the naked eye. Moreover, the "cavity-diffusion" effect of porous MOF shells validates the selective concentration of gaseous BA molecules on the GNR surface, allowing the discrimination of BA in exhaled breath rapidly and precisely even at the sub-ppb level with excellent specificity against other volatile organic compounds. This study not only offers a versatile sensing platform for accurate discrimination of lung cancer from controls but also opens an avenue for the design of smart sensors for point-of-care applications.

A low cost, disposable and easy to use microfluidic paper-based analytical device (μPAD) was developed for simple and non-invasive determination of total aldehydes in saliva with a potential to be used in epidemiological studies to assess oral cancer risk. The μPAD is based on the colour reaction between aldehydes (e.g. acetaldehyde, formaldehyde), 3-methyl-2-benzothiazolinone hydrazone (MBTH) and iron(III) to form an intense blue coloured formazan dye. The newly developed μPAD has a 3D design with two overlapping paper layers. The first layer comprises 15 circular detection zones (8 mm in diameter), each impregnated with 8 μL of MBTH, while the second layer contains 15 reagent zones (4 mm in diameter). Two μL of iron(III) chloride are added to each one of the second layer zones after the addition of sample to the detection zones in the first layer. All hydrophilic zones of the μPAD are defined by wax printing using a commercial wax printer. Due to the 2-step nature of the analytical reaction, the two paper layers are separated by a cellulose acetate interleaving sheet to allow for the reaction between the aldehydes in the saliva sample with MBTH to proceed first with the formation of an azine, followed by a blue coloured reaction between the azine and the oxidized by iron(III) form of MBTH, produced after the removal of the interleaving sheet. After obtaining a high resolution image of the detection side zone of the device using a flatbed scanner, the intensity of the blue colour within each detection zone is measured with Image J software. Under optimal conditions, the μPAD is characterised by a working range of 20.4-114.0 μM, limit of detection of 6.1 μM, and repeatability, expressed as RSD, of less than 12.7% (n = 5). There is no statistically significant difference at the 95% confidence level between the results obtained by the μPAD and the reference method (Student's t-test: 0.090 < 0.38). The optimized μPAD is stable for more than 41 days when stored in a freezer (≤-20 °C)., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This paper reports the continuous reductive amination of different molecules, including biomass-related compounds, over carbon-supported FeNi nanoparticles obtained on the basis of inexpensive and abundant metal precursors and cellulose. A biorefinery case study for the preparation of pyrrolidones via acid-catalyzed hydrolysis of glucose followed by reductive amination of the obtained levulinic acid is described., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this study, effect of two chemical compounds (i.e., 1-octanol and hexanal) respectively from the alcohol and aldehyde groups on thermophilic (55±2 °C) anaerobic process digesting the waste produced at a paper industry was investigated. In this scope, possible inhibition was monitored by the cumulative methane (CH4) yields in the batch reactors digesting the paper waste as the feedstock at concentrations of 0.005%, 0.05%, and 0.5% for each compound. Comparing the effects of the two different groups with the control reactor having only the paper waste as the substrate, the results revealed that adding 1-octanol and hexanal up to 0.05% concentrations had some synergistic effect on biogas yield (i.e., from 3% to 12% enhancement). Accordingly, the highest methane yields were 550 and 567 mL/g-VSfed, respectively on average in the presence of 1-octanol and hexanal at a concentration of 0.05% while the cumulative methane yield was observed as 490 mL/g-VSfed for the control reactor. With the exception of 1-octanol at 0.5%, adding both compounds at each investigated concentration was beneficial for the digestion in the batch process. Therefore, the selected alcohol and aldehyde sources did not cause the expected detrimental effect on the methanogens even at the maximum amounts added in this study. Nevertheless, since the effect of the chemical compounds on methane generation has been generally concentration-dependent, the toxic effects of 1-octanol and hexanal would be better observed at higher concentrations (>0.5%), especially when their threshold levels are exceeded in anaerobic reactors digesting paper wastes. [ABSTRACT FROM AUTHOR]

An ammonium chloride–Congo red (NH4Cl-CR) solution is presented as a potential sensing solution for aldehydes. Monofunctional aldehydes such as formaldehyde, acetaldehyde, benzaldehyde, and isobutyraldehyde caused changes in the pH of the sensing solution, producing a color transition from red-orange to violet to blue. This distinguished them from the other compounds, thereby acting as a qualitative test for the functional group. The NH4Cl-CR solution was also employed in making filter paper-based and silica gel-based sensors for formaldehyde and acetaldehyde vapors. These sensors responded positively towards the aldehyde gases through a color transition from pink to blue. The NH4Cl-CR mixture provides a simple and easy-to-handle reagent for the detection of both liquid and gaseous aldehydes which has potential applications in environmental monitoring.

[Display omitted] • Gentle power of laser was used to do surface modification of paper substrates. • Effects of different types of lasers including CWL, NS, and FS were studies. • Physical and chemical changes of laser-ablated paper were investigated. • Aldehydes were produced by laser ablation and raised the paper's chemical reactivity. • Aldehydes-related color chemical reactions were performed with acoustofluidic PADs. Paper-based analytical devices (PADs) have rapidly thrived in the last decade for their easy operation and rapid response. However, because of its low chemical reactivity, it's still challenging to endow the paper substrate with more functions and expand its application field. Here, this work leverages lasers to do surface modifications of paper to raise its chemical reactivity. A gentle power of laser was utilized to ablate a part thickness of the paper. The effect of laser types was studied, including continuous-wave, nanosecond, and femtosecond lasers. Continuous-wave laser caused severe photothermal effects and produced more pyrolytic oil. The physical changes including mechanical strength and fluid wicking were studied. The chemical changes were analyzed by XPS and FTIR. Because of the produced aldehydes by laser ablation, the laser-modified papers were endowed with more functions and we experimented with aldehyde-related color reactions on them, which might promote the color printing industry. In addition, to fully exploit the produced aldehydes, our recently developed acoustofluidic PADs were employed for flow intensification and homogeneous mixing. This work demonstrates an economical and effective method for a new type of functional paper substrates which holds potential for various fields. [ABSTRACT FROM AUTHOR]

It is commonly known that aldehyde dehydrogenases (ALDHs) are a promising therapeutic target in many diseases. Bui et al.--the authors of the paper I am discussing here (Biosci Rep (2021) 41(5): BSR20210491 https://doi.org/10.1042/BSR20210491)--point that there is a lack of research on the use of spices and herbs as the sources of naturally occurring modulators of ALDH activity. In order to carry out this type of research, the authors prepared ethanolic extracts of 22 spices and herbs. The main objective of the study was to investigate retinaldehyde dehydrogenases (RALDHs), of which retinal is the main substrate and ALDH2, the mitochondrial isoform, having acetaldehyde as the main substrate. The obtained results indicated that the tested extracts exhibited differential regulatory effects on RALDHs/ALDH2 and some of them showed a potential selective inhibition of the activity of RALDHs. [ABSTRACT FROM AUTHOR]

We have been able to demonstrate that glutaraldehyde fixation of tumor cells or tumor cell membrane fragments protect syngeneic mice against the subsequent challenge with viable cells. To date we have not been able to detect any antibody against the tumor cells in animals so immunized. The specificity of the response is not complete, although a major component of the protective effect of glutaraldehyde-treated tumor cells is immunologically specific.

A simple method to increase the overall sensitivity of immunoblot assays is described. The method is based on fixation of the primary monoclonal antibody-antigen complex on nitrocellulose paper by a divalent crosslinker, glutaraldehyde. The fixation of the antibody-antigen complex significantly increases the sensitivity of the assay. Unexpectedly, the glutaraldehyde treatment also improves the signal/noise ratio by decreasing non-specific binding of secondary antibodies and/or tertiary reagents. Thus, a significant overall improvement of immunoblot assays is achieved by this method.

The development of mild, efficient, and enantioselective methods for preparing chiral building blocks from simple, renewable carbon units has been a long-term goal of the sustainable chemical industry. Mandelate derivatives are valuable pharmaceutical intermediates and chiral resolving agents, but their manufacture relies heavily on highly toxic cyanide. Herein, we report (S)-4-hydroxymandelate synthase (HmaS)-centered biocatalytic cascades for the synthesis of mandelates from benzaldehydes and glycine. We show that HmaS can be engineered to perform R-selective hydroxylation by single-point mutation, empowering the stereodivergent synthesis of both (S)- and (R)-mandelate derivatives. These biocatalytic cascades enabled the production of various mandelate derivatives with high atom economy as well as excellent yields (up to 98 %) and ee values (up to >99 %). This methodology offers an effective cyanide-free technology for greener and sustainable production of mandelate derivatives., (© 2023 Wiley-VCH GmbH.)

Endodontic paper points were tested for antibacterial activity after the accidental finding that bacterial cultures were inhibited by one variety. Of five types tested, two, from the same supplier, were found to exhibit diffusible antibacterial activity against salivary and subgingival plaque micro-organisms. The identity of the agent responsible for this activity has not been determined, but preliminary tests indicate that it is an aldehyde. [ABSTRACT FROM AUTHOR]

Currently, the production of furan aldehydes from raw biomass suffers from low furfural yield and high energy consumption. In this study, a recyclable and practical method was explored for the preparation of furfural from corn stover by the one-pot reaction by acidic lithium bromide solution (ALBS) without pretreatment and enzymolysis. In the ALBS reaction, the furan aldehydes were generated by the degradation of lignocellulose; however, the products were unstable and were further dehydrated to form humins. So, dehydration reaction was inhibited in this study, and the high yield of furan aldehydes was obtained, in which 2.94 g/L of furfural and 2.78 g/L of 5-hydroxymethyl furfural (5-HMF) were generated with high solid loading (10 wt%), the presence of commercial catalyst ZSM-5 and co-solvent tetrahydrofuran (THF) at 140 °C for 200 min. Via this method, almost 100% of hemicellulose was transformed to furfural, and 40.71% of cellulose was transformed to 5-HMF, which was based on the theoretical yield of HMF (8.35 g) from glucose (29.30 g) produced from cellulose. After the reaction, the catalyst ZSM-5 was the main component in the solid residue and kept a suitable performance. THF azeotrope was easily separated from the slurry by evaporation. During the removal of THF, lignin was precipitated from the liquid phase and showed lower molecular weight and abundant active groups, which was a potential feedstock for producing valuable aromatics and polymers. Thus, in a one-pot reaction, the ideal yield of furan aldehydes from raw biomass was obtained on a lab scale, and the catalyst, THF, and LiBr were easily recycled, which provided an option to realize the economical production of sustainable furan aldehydes from raw biomass., Competing Interests: All authors declare no conflict of interest and have approved the manuscript.

Asymmetric catalytic cascade processes offer direct access to complex chiral molecules from simple substrates and in a single step. In biocatalysis, cascades are generally designed by combining multiple enzymes, each catalyzing individual steps of a sequence. Herein, we report a different strategy for biocascades based on a single multifunctional enzyme that can promote multiple stereoselective steps of a domino process by mastering distinct catalytic mechanisms of substrate activation in a sequential way. Specifically, we have used an engineered 4-oxalocrotonate tautomerase (4-OT) enzyme with the ability to form both enamines and iminium ions and combine their mechanisms of catalysis in a complex sequence. This approach allowed us to activate aldehydes and enals toward the synthesis of enantiopure cyclohexene carbaldehydes. The multifunctional 4-OT enzymes could promote both a two-component reaction and a triple cascade characterized by different mechanisms and activation sequences., (© 2022 Wiley-VCH GmbH.)

Due to endogenous existence and hazardous properties, the quantification of fatty and aromatic aldehydes in food matrices is indispensable to food safety. Current analytical methodologies for aldehydes in food suffer from several drawbacks (typically complicated pretreatment, long analysis time and low analytical throughput, low sensitivity, etc.). In this work, a highly sensitive, high-throughput and sample pretreatment-free method for aldehyde analysis was developed to address the above problems, where in situ extraction and derivatization of aldehydes with hydrazines to hydrazones were integrated into reactive paper spray ionization mass spectrometry (reactive PSI-MS) considering weakly ionizable properties of aldehydes. Four aldehydes, formaldehyde, acetaldehyde, propionaldehyde and benzaldehyde were reacted with dansyl hydrazine in 1.5 % v/v HAc acidified methanol on the qualitative fast-speed filter paper for 5 min, and then a voltage (+4 kV) was applied to initiate paper spray for mass spectrometry detection with internal calibration by dansyl amide. Once the completion of MS analysis, the glass plate was moved to introduce the second triangular tip towards the MS inlet (5 mm apart) for next trial, achieving high-throughput reactive PSI-MS analysis (60 h−1). The four aldehydes showed good linearity in the concentration range from 2 to 150 μM with low detection limits of 0.03–0.15 μM. The method was applied to direct quantification of four aldehydes in 15 kinds of foods such as vegetables, fruits and meat products. The proposed method has the advantages of simple operation, high efficiency and high sensitivity, making it attractive to routine analysis of aldehydes in food, environmental and biological samples. • FA, AA, PA and BA were simultaneously quantified by reactive PSI-MS. • Four aldehydes were derivatized by dansyl hydrazine without sample preparation. • A high throughput of 60 h−1 was achieved by array-tip PSI-MS. • Quantification of four aldehydes at the sub μM levels in food was accomplished. [ABSTRACT FROM AUTHOR]

In this study, a fluorescent reagent, 4-((aminooxy)methyl)-7-hydroxycoumarin (AOHC), was for the first time applied to label the low-molecular-mass aldehydes (LMMAs) through reductive oxyamination reaction to afford single N,O-substituted oxyamine derivatives at room temperatures with derivatization efficiencies as high as 96.8%. In the following high-performance liquid chromatography with fluorescence detection analysis, 12 LMMAs, including furfurals, aromatic aldehydes, and aliphatic aldehydes, were baseline-separated on an ODS column and detected with low limits of detection (LODs) (0.2-50 nM), and good precisions (intraday relative standard deviations [RSDs] were 2.40-4.68%, and interday RSDs were 4.65-8.91%). This approach was then adopted to analyze six alcoholic beverages and five dairy products, and nine LMMAs with concentrations in the 0.28-798.16 μM range were successfully detected with excellent accuracies (recoveries were 92.2-106.2%). Finally, the results were statistically analyzed and discussed. The proposed method has several advantages, including high sensitivity, room-temperature labeling, and the avoidance of further extraction and/or enrichment procedures, demonstrating its great utility for monitoring LMMAs in various complex matrices., (© 2022. Springer-Verlag GmbH Germany, part of Springer Nature.)