Different Concentrations Of Formaldehyde Research Articles

UV-activated semiconductor gas sensor response measurement for formaldehyde detection

The gas sensing characteristics of ultraviolet light-emitting diodes (UV-LEDs)-activated semiconductor sensors were investigated to detect formaldehyde (HCHO) as a model volatile organic compound (VOC). As the major drawback of formaldehyde gas sensors is the low durability of the sensing material, efforts were made to establish a suitable metal oxide semiconductor and to enhance its stability throughout the sensing process. In2O3 nanoparticles (NPs) as the sensing material showed restructuring caused by exposure to different concentrations of formaldehyde in the presence of UV radiation when its morphology and structure were analyzed. UV radiation in the presence of formaldehyde was found to play a critical role in nanoparticles agglomeration, as well as its response inconsistency and instability.The novel method of measuring UV radiation elimination in the initial stages of the response curve was deemed effective for sensing layer preservation in this study. The scanning electron microscopy (SEM) results showed that this approach prevented any notable deformation in the nanoparticles’ shape and size and resulted in reproducible responses to various formaldehyde concentrations (10–50 ppm) in the steady-state and transient (5 min exposure) phases of the response curve. Hence, a short-time UV exposure has the potential to be applied in practical gas sensing applications in which the sensor can be automatically turned off a few minutes after any target gas detection. The gas sensor response slope in the transient phase of the response curve was found to be a very good indicator of target gas concentration and to obtain fast and consistent results while preserving the sensing material from restructuring. The findings of this study can be incorporated into the development of UV-LED-activated gas sensors where stable and fast response measurements of VOCs are required.

Optimization of Formaldehyde Fixative Concentration for Individual Blood Cells to Develop a Stabilized Blood Control for Automated Hematology Analyzers.

In a modern haematology laboratory, the complete and differential counts of blood are performed using complex haematology auto analyzers. In order to ensure the accuracy and reliability of test results, various regulatory authorities have prescribed the use of stabilized blood controls. The major pitfalls of these blood controls are their short shelf life. This could be due to the fact that they are prepared by a common cocktail of fixatives which acts on the discrete cells in various ways and would result in either under-fixation or over-fixation of various cells. Thus, in the present study, we have explored and optimized fixative and buffering for individual cells to achieve stable blood control. Blood cells were isolated using the centrifugation technique and were fixed individually with different concentrations of formaldehyde. After fixation, cells were pooled. Analysis of cell count was done till six months. Cells were also analysed morphologically to see the effect of fixation and storage on cell morphology. In the present study we compared the effect of the concentration of formaldehyde fixative for individual cells in the blood and their role in enhancing the shelf life and maintaining the morphology of the cells when suspended in plasma or suitable buffers post-fixation. It was observed that WBCs can be better fixed with 3 and 3.5% formaldehyde in a buffered solution, whereas RBCs and Platelets can be optimally fixed with 2.5% formaldehyde in a buffered solution.

Effect of artificial formaldehyde treatment on textural quality of fish muscles and methods employed for formaldehyde reduction from fish muscles

The influence of treatment of three different concentrations of formaldehyde on fish muscles textural quality was determined using spectrophotometric and reverse phase high-performance liquid chromatography (RP-HPLC) methods. The experimental fish treated with 1, 5 & 10 % formaldehyde for 5 min and as a result, the residual content was enhanced to almost 7, 11 and 15 times respectively. The hardness and chewiness of fish muscles increased with increase in formaldehyde concentration and the values increased by 80 and 121 % respectively in the fish treated with 10 % formaldehyde. In order to reduce formaldehyde content in fish, formaldehyde-treated fish was washed in running tap water, saline water and tepid water separately for a period up to 30 minutes and thereby the content got reduced to the acceptable label in 20, 20, and 10 min respectively. Similarly, treated fish was fried for five minutes and content was reduced to acceptable limits. Overall, this study could establish that formaldehyde treatment not only reduced bacterial load but also improved the textural properties of the fish muscles, creating the impression that the fish is fresh. Tepid water washing and frying process were effective in reducing formaldehyde content in fish muscles.

Validation of Free Formaldehyde Determination Method in DT Vaccine and Tetanus Toxoid Antigen.

Validation is a Good Manufacturing Practice principle that proves any procedure, process, method, equipment, material, activity, or system actually leads to the expected results. This study validates the method for the determination of free formaldehyde in biological products (including the diphtheria-tetanus vaccine and tetanus toxoid antigen). The operatingprocedure of this method is based on pharmacopoeial monographs. It also does not require full validation, although its suitability under the actual condition of use should be verified. Performance characterizations, such as accuracy, intra-precision (repeatability), intermediate precision (inter-precision), linearity, range, and the limit of quantitation, were investigated and calculated. Accuracy and precision were studied at different concentration levels by spiking known amounts of formaldehyde in real samples. The accuracy and precision results were expressed as the recovery and the relative standard deviation (RSD), respectively. Precision was expressed as intra-precision (repeatability) and inter-precision. Intra-precision or repeatability was performed by one operator in one day by adding three levels of concentration to the products. The inter-precision was conducted by one operator in three individual days within the same laboratory at three concentration levels. Range and linearity were assessed by investigating the correlation coefficient of the regression line between different concentrations of formaldehyde and their response. The acceptance criteria and limits were defined for these validation parameters in these biological products. The RSD for intra-day and inter-day precision studies was less than 5% in a medium concentration of linear range. At this concentration level, accuracy was 90%-110%. The method's linearity ranged between 0.0000039%-0.01% w/v of formaldehyde with a correlation coefficient of 0.9999. The results exhibited sufficient linearity, accuracy, precision, and range. Therefore, this method can be used successfully to determine free formaldehyde for biological products.

An optical sensor for the sensitive determination of formaldehyde gas based on chromotropic acid and 4-aminoazobenzene immobilized in a hydrophilic membrane.

Formaldehyde is a common contaminant in occupational and environmental atmospheres, prolonged exposure leads to health risks, and its determination is necessary to protect health. There is a great demand for portable, rapid, and sensitive methods that can be used in resource-limited settings. In this respect, a colorimetric sensor has been developed based on the colour change from pink to purple of co-immobilized chromotropic acid and 4-aminoazobenzene in hydroxypropyl methylcellulose when it is exposed to different concentrations of formaldehyde. The concentration of formaldehyde in the gas phase was quantified by measuring the change of the appropriate colour coordinates in response to the concentration of formaldehyde. A calibration curve was obtained for formaldehyde, with a useful concentration range from 0.08 to 0.6 ppmv. The detection limit was 0.016 ppmv, which is lower than the maximum exposure concentrations recommended by both the World Health Organization (WHO) and the Occupational Safety and Health Administration (OSHA). The optical sensor was found to have good reproducibility, with a relative standard deviation of 2.3 and 1.7% at 0.08 and 0.25 ppmv, respectively. The sensor can operate at room temperature and environmental humidity, 25 °C, and 50% RH, respectively. In addition, a study of interferents (acetaldehyde, toluene, methanol, ethyl acetate, acetone, acetic acid, carbon dioxide and ammonia) showed high selectivity for formaldehyde, which indicates that this membrane is a simple, fast, and economical alternative for quantifying the concentration of formaldehyde in different environments.

Design of a microfluidic lung chip and its application in assessing the toxicity of formaldehyde

In this work, a microfluidic lung chip with membrane supporting cell growth that can produce multiple concentration gradients of gas and liquid is introduced. The chip is composed of a gas gradient layer in the upper part, a porous membrane supporting cell growth in the middle and a liquid gradient layer in the lower part. The gas-liquid interface environment of the cells on the membrane can expose the cells to the gas in the upper layer and the liquid in the lower layer at the same time. Then, the chip is applied to the toxicity testing of formaldehyde in A549 cells. The results showed that at 6 × 10−5 mol/L formaldehyde, the survival rate of the cells in four channels were 90, 87, 81, and 71%, which shows a dose-response trend under the influence of different concentrations of formaldehyde. ROS staining results also showed that formaldehyde exposure at 6 × 10−5 mol/L lead to the increase of ROS level in the cells. These results suggest that the chip based on cell growth on membrane could be used for toxicological evaluation of environmental polluting gases.

SARS-CoV-2 VIRUS: ISOLATION, GROWTH, THERMOSTABILITY, INACTIVATION AND PASSAGES

Coronaviruses are a large family of RNA-containing viruses capable of infecting humans and a number of animal species. Several species of coronaviruses are now known to circulate in the population and generally cause moderate to severe upper respiratory tract and lung disease. A new coronavirus infection, COVID-19 (SARS-CoV-2), has been added to this list. The virus has spread rapidly around the world. Recently in Kazakhstan, this infection has been observed with pronounced pneumonia among the population. In developing the vaccine, we had to work with live SARS-CoV-2 virus. It should be noted that when working with live virus, we faced some issues concerning the biological and physicochemical properties of the virus, which have remained outside the attention of scientists of the world. In this connection, in these studies we studied some physicochemical and biological properties of Kazakh strain of SARS-CoV-2 virus isolated from a patient with new coronavirus infection COVID-19, such as thermal stability (persistence), virus inactivation by different concentrations of formaldehyde at different temperature and time regimes and virus passivation in cell culture. Studies were conducted to find additional biological models sensitive to the SARS-CoV-2 virus and used in vitro. Of the 11 cell culture species tested, monkey and pig cell cultures were found to be the most sensitive to the SARS-CoV-2 virus, in which the virus was actively reproducing. We studied the effect of storage conditions of SARS-CoV-2 nucleic acid samples as well as the effect of environmental conditions on the SARS-CoV-2 virus itself. The results of our studies showed that freezing at minus 70 оС and thawing at room temperature (20-22 оС) had no appreciable effect on the qualitative character of cytopathogenicity but had a negative effect on the preservation of virus titer. Data on the effects of chemical factors when working with pathogens are necessary to create conditions of biological safety for personnel and the environment, as well as the design of technologies for the manufacture of biological products for diagnostic and prophylactic purposes. In this study, we studied the effect of formaldehyde to the virus. The results obtained show that inactivation of Sars-CoV-2 virus with formalin depends on formaldehyde concentration, reaction temperature, incubation time.

UV-Activated Formaldehyde Sensing Properties of Hollow TiO2@SnO2 Heterojunctions at Room Temperature

Introduction Formaldehyde (HCHO) is an important chemical raw material that has a wide range of applications in interior decoration materials such as adhesives, building materials and coatings. Long-term exposure to formaldehyde can cause headaches, memory loss, especially harmful for pregnant women and infants [1]. Therefore, timely and accurate detection of formaldehyde in indoor environments is very important.In this aspect, titanium dioxide (TiO2) is a typical n-type of semiconductor. Due to its good photocatalytic performance, low cost, non-toxicity and high thermal stability, it has been explored for chemical gas sensors [2]. As reported in literature [3], the construction of heterojunction structure could significantly enhance the gas-sensing performance, and the use of UV irradiation can greatly reduce the working temperature of the sensor, or even down to room temperature [4]. Therefore, the gas sensing properties of SnO2 and TiO2@SnO2 heterojunctions have investigated in this work. Experiment First, the carbon nanospheres templates were prepared by hydrothermal method. Hollow SnO2 nanospheres were obtained by using carbon nanospheres as templates via hydrothermal method at 170 °C for 36 h. Then, hollow SnO2 nanospheres were dispersed into absolute ethanol, tetrabutyl titanate (TBT) and ammonia were added into above solution. Stirred for 24 h at room temperature. Finally, the as-obtained precipitates were calcined at 500 °C for 2 h. The as-prepared hollow SnO2 nanospheres and TiO2@SnO2 heterojunctions powder were dispersed in an alcohol solution. The paste was deposited onto the alumina substrates with Au interdigital electrodes. Then, the sensors were dried at 70 °C for 12 h. Results and conclusions 1. Structure and MorphologyFig.1a shows the XRD patterns of as-synthesized hollow SnO2 nanospheres, hollow TiO2 nanospheres and hollow TiO2@SnO2 heterojuction nanospheres, All the diffraction peaks of TiO2 and SnO2 can correspond to JCPDS card No. 21-1272 and JCPDS card No. 41-1445, respectively. There are no other diffraction peaks of impurity in the XRD pattern. As Fig. 1b shows that the as-prepared SnO2 nanospheres have a distinct hollow structure and the particle size is about 200-300 nm. Fig. 1c presents that the surface of the TiO2@SnO2 nanocomposites is significantly rougher than pure SnO2, and a layer of granular TiO2 is wrapped around the hollow SnO2 nanospheres. From Fig. 1d, the thickness of hollow SnO2 nanospheres inner shell is about 50 nm. Fig. 1d exhibits the lattice fringes of hollow TiO2@SnO2 heterojunctions. The spacing of lattice fringes of TiO2 and SnO2 in the heterojunctions are measured to be 0.357 nm and 0.238 nm, respectively. They can be assigned to (101) lattice plane of anatase TiO2 structure and (200) lattice plane of rutile SnO2 consistent to the XRD results. Fig. 1f show that the element of Ti is uniformly distributed around the Sn element, and the O element is distributed in the whole region.2. Gas-Sensing PropertiesFig. 2a shows the response curves of the hollow TiO2@SnO2 nanospheres and pure TiO2 nanospheres based sensors to different concentrations of formaldehyde under UV at room temperature. The response of the sensors increases as the formaldehyde concentration increases from 0.1 ppm to 10 ppm. Even at lower formaldehyde concentrations, such as 100 ppb, the response of the TiO2@SnO2 nanocomposite based sensor still higher than that of the pure TiO2 based sensor. Fig. 2b shows the response curves of hollow TiO2@SnO2 nanospheres and pure TiO2 based sensors to 10 ppm formaldehyde under UV illumination at room temperature. The response value of TiO2@SnO2 nanocomposites based sensor is about 20, which is much higher than that of TiO2. The response time and recovery time of TiO2@SnO2 nanocomposites are 20 s and 56 s, respectively. The above results show that after incorporated with SnO2, the gas-sensing property of the TiO2 sensor is significantly improved.

Sensitive Formaldehyde Detection with QCM Sensor Based on PAAm/MWCNTs and PVAm/MWCNTs.

Two formaldehyde detection methods are proposed by applying composite film quartz crystal microbalance (QCM) sensors. QCM sensor coated with PAAm/MWCNTs and PVAm/MWCNTs shows excellent characteristics of lower limit and high sensitivity. The lower limit of PVAm/MWCNTs is 0.5 ppm, and its detection sensitivity is 0.74 ppm/Hz. Upon working at different concentrations of formaldehyde and fabricating in different proportions, the reuse performance, gas selectivity, and response at room temperature show contrasting results. The main advantages of the two sensors presented are fast reaction, low cost, and easy manufacture. Compared to other formaldehyde sensors based on QCM, the PAAm/MWCNT- and PVAm/MWCNT-coated QCM sensors are able to concurrently show excellent selectivity, reuse performance, and high sensitivity, which is of great significance to detect the environmental quality.

Regulation of Aβ40 and Aβ42 by formaldehyde exposure in a three‐dimensional (3D) human neural cell culture model for Alzheimer's Disease

Alzheimer's disease (AD), a chronic neurodegenerative disorder characterized by rapidly progressive cognitive dysfunction and behavior impairment, is the most common form of dementia which accounts for 60 to 70 percent of cases. Pathologically, AD is characterized by severe atrophy and neuronal loss, extracellular neuritic plaques composed mainly of aggregated amyloid-b (Ab), and intracellular neurofibrillary tangles consisting of hyperphosphorylated tau protein. Multilevel complex interactions between genetic, epigenetic, and environmental factors contribute to the occurrence and progression of AD. Formaldehyde (FA) is the simplest saturated aldehyde which is one of the most typical environmental and occupational aldehyde pollutants. Recent studies suggested that elevation of FA in the brain, blood or urine by endogenous and/or exogenous exposure may play important roles in AD development. A three-dimensional (3D) human neural cell culture model for AD which can recapitulate key events of AD pathology including β-amyloid plaques and neurofibrillary tangles was used to investigate the effect of FA exposure in AD development and progression in human cells. Immortalized human neural progenitor cells (ReNcell VM (ReN)) were virally transfected with AD-related mutant genes including mutant APP and/or PSEN1 and enriched based on GFP and/or mCherry signals by Fluorescence-activated cell sorting (FACS). In order to mimic the restrictive environment of human brain and allow Aβ deposition and aggregation, the FACS-sorted ReN cells were differentiated into neurons and maintained in a 3D Matrigel culture system. The AD Model and primary ReN cells were treated with different concentrations of FA as well as vehicle controls for 16 weeks. Expression of Aβ40 and Aβ42 were measured in 4, 6, 12 16 weeks by ELISA and cytotoxicity was evaluated by LDH activity assay. The results revealed that FA significantly elevates expression of Aβ40 and Aβ42 in a concentration-dependent manner both in AD model and ReN cells. It indicated that FA exposure may play a critical role in AD development and progression.

In Vitro, D-Ribose and Formaldehyde Glycating Effects on Hen Egg White Lysozyme

Background: Glycation causes severe damage to the protein structure, instigating different diseases like cataracts, nephropathy, vasculopathy, retinopathy, atherosclerosis, neurodegenerative disease, diabetes, and age-dependent complications. Formaldehyde, a pollutant present in human habitation, is produced endogenously or exogenously during cooking or incinerating wood, paints, furniture, chipboards, fabric etc. Its higher concentrations can cause cell damage that promotes the formation of DNA/Protein cross-links. The present study aimed to evaluate the glycating effects of formaldehyde on hen egg white lysozyme in comparison with known glycating agent D-ribose. Methods: In this, in-vitro study, hen egg white lysozyme (HEWL) glycation with different concentrations of formaldehyde (0.25mM, 0.5mM, 1mM and 2mM) and D-ribose (0.01mM, 0.05mM, 0.1mM and 0.5mM) was examined using two different experimental conditions: concentration and time duration. Further cross-linking of protein was also analysed using SDS-PAGE technique. Results: Glycation of HEWL treated with formaldehyde increased with increasing concentrations (0.25mM, 0.5mM, 1mM and 2mM) and time duration (1, 3, 7 and 15 days). Cross linking of HEWL showed visible glycation at 2mM concentration. Cross-linked HEWL products gave dimer at 0.25mM and 0.5mM and trimers at 1mM and 2mMat 3, 7 and 15days. However, compared to formaldehyde, D-ribose glycation at different concentrations (0.01mM, 0.05mM, 0.1mM and 0.5mM) did not show the prominent cross linking of protein. Conclusion: Formaldehyde was found to be a more potent glycating agent compared to D-ribose. Compared to D-ribose, formaldehyde can produce protein misfolding and can be used in clinical research to establish the role of formaldehyde in patients with diseases.

Portable, Disposable, Paper-Based Microbial Fuel Cell Sensor Utilizing Freeze-Dried Bacteria for In Situ Water Quality Monitoring.

Water quality monitoring is becoming an essential part of our lives as increasing human activities continue to spill unknown and unexpected contaminants into our water systems. To ensure the provision of safe and clean water to the public and the ecosystem, the development of rapid and sensitive in situ early warning systems for water toxicity monitoring is crucial. In this work, an entirely paper-based microbial fuel cell sensor utilizing freeze-dried bacteria is demonstrated as a portable and disposable water toxicity sensor. The bacterial cells were preinoculated on the anode reservoir of the device, and they were freeze-dried, making their on-site and on-demand applications possible. Upon rehydration of the bacteria with the water samples, current readings were obtained, and inhibition ratios (IRs) were calculated for different concentrations of formaldehyde as a model toxin. For 0.001, 0.01, and 0.02% of formaldehyde, IRs of 7.88, 16.08, and 23.14% were obtained, respectively. These IRs showed a very good linearity with the formaldehyde concentrations at R2 = 0.995. Additionally, the shelf life of the freeze-dried microbial fuel cell sensor was investigated. Even after 14 days of storage in the desiccator, at 4, and at −20 °C, the performance outputs compared to the new device were all at 96%.

Bacterial response to formaldehyde in an MFC toxicity sensor

Microbial fuel cells (MFCs) have been extensively studied as toxicity sensors. MFCs have potential as toxicity sensors because when their anodes are exposed to toxic substances or the concentration of the target is changed, the voltage generated by certain microorganisms with active electrical activity attached to the anode changes. However, the underlying reasons behind this phenomenon have not been deeply explored. Therefore, the activity of anodic microorganisms during voltage drops in MFCs under formaldehyde (FA) stress was studied. The composition of the microbial community structure with similar active voltage drops under different concentrations of FA was investigated. The results showed that under exposure to high concentrations (169.20 mg/L) of FA, the voltage changes in MFCs could be divided into five stages. With prolonged exposure to FA, the ratio of live/dead bacteria decreased from 4.78 to 0.65. This result indicated that voltage drops may be caused by FA causing cell membrane rupture. Analysis of the microbial community structure under treatments including inoculation and three concentrations of FA revealed that Geobacter and other electrogenic bacteria were effectively enriched in the MFCs. Low-concentration and long-term exposure to FA had a greater impact on microbial communities than high-concentration and short-term exposure. Pseudomonas and Acidovorax were more significantly affected by FA than Flavobacterium and Geobacter. This study explains the reason for the voltage drop of MFCs after exposure to toxic substances from the perspective of the microorganisms.

Highly Rapid and Sensitive Formaldehyde Detection at Room Temperature Using a ZIF-8/MWCNT Nanocomposite.

Formaldehyde is a volatile organic compound (VOC) with extensive applications, volatility, and toxicity, which have made it an important risk to human health even at low concentrations. Therefore, rapid detection of formaldehyde vapors in the environment is a necessity. Herein, we introduce a resistive gas sensor based on zeolitic imidazolate framework-8/multiwalled carbon nanotube (ZIF-8/MWCNT) for detection of formaldehyde vapors at room temperature. In this sensor, a low amount of MWCNTs was used in order to improve the electrical conductivity of the porous nanoparticles of ZIF-8. The sensor was fabricated by deposition of a thin layer of the nanocomposite onto interdigitated electrodes, and its sensing ability was investigated on exposure to formaldehyde vapors. The obtained sensor showed sensitive and fast responses to different concentrations of formaldehyde, and the sensor response to formaldehyde was higher than toward some other VOCs, including methanol, ethanol, acetone, and acetonitrile. Furthermore, because of the hydrophobic nature of ZIF-8, the effect of relative humidity on the gas-sensing performance was insignificant, which proves that this sensor is suitable for use under humid conditions.

Low concentrations of FA exhibits the Hormesis effect by affecting cell division and the Warburg effect

Formaldehyde (FA), a ubiquitous indoor environmental pollutant, has been classified as a carcinogen. There are many studies showed that low levels of FA could promote cell proliferation, however, little is known about the signal pathways. To determine the potential molecular mechanisms, human chronic myeloid leukemia cells (K562 cells) and human bronchial epithelial cells (16HBE cells) were exposed to different concentrations of FA. The data showed that FA at 0–125 μM or 0–60 μM promoted the proliferation of K562 cells or 16HBE cells respectively, indicating that FA did have the Hormesis effect. FA at 75 μM (K562 cells) and 40 μM (16HBE cells) significantly promoted cell proliferation, increased intracellular reactive oxygen species (ROS) levels, and decreased glutathione (GSH) content. At the same time, FA treatment induced a marked increase in the key molecules of cell division like CyclinD-cdk4 and E2F1. In addition, pyruvate kinase isozyme M2 (PKM2), glucose, glucose transporter 1 (GLUT1), lactic acid and lactate dehydrogenase A (LDHA) content in the Warburg effect were increased. Administering Vitamin E (VE), significantly disrupted cell division and disturbed the Warburg effect, effectively indicating the decrease of cell activity. Conclusively, these findings suggested that low concentrations of FA could promote cell proliferation by accelerating cell division process or enhancing the Warburg effect to embody the Hormesis effect.

A quantitative evaluation method for wastewater toxicity based on a microbial fuel cell

A microbial fuel cell (MFC) was successfully developed as a toxicity biomonitoring system to enable a quick response to wastewater with unknown toxicity in toxic events. The objective was to quantitatively assess the toxicity of wastewater by a rapid method. Different concentrations of formaldehyde were introduced into the anode chamber, which led to different stages of voltage change. A relationship between the linear slope of the voltage drop stage and the formaldehyde concentration was established through dose-response fitting results. This relationship makes it possible to convert an unknown toxicity of wastewater into the equivalent concentration of formaldehyde. The minimum detection limit in this study was 13 mg/L formaldehyde equivalents. As the toxicity of the wastewater increased, the test time could be reduced to as low as 921 s or even shorter, with a detection error of 3–12 mg/L. By using this evaluation method, oxidized tail gas scrubber wastewater was identified as the main toxic wastewater component in a phenol acetone production plant.

UV Light Activated SnO2/ZnO Nanofibers for Gas Sensing at Room Temperature

Hierarchical SnO2/ZnO nanofiber heterojunctions composed of SnO2 nanofiber matrix on top of which ZnO nanorods protruding 30- 90 nm long were assembled, were examined for chemiresistive-type gas sensors under UV activation at room temperature. The sensor demonstrated excellent sensitivity to different concentrations of formaldehyde and selectivity to several possible interferents such as alcohols, methanol, benzene, methylbeneze and acetone with UV LED at a wavelength of 365 nm. The fiber-like heterojunctions can facilitate the electron transfer from ZnO to SnO2 and this effect would be augmented further under UV light activation. Consequently it enhanced the oxygen adsorptions on the surface of the heterojunctions thus leading to the excellent sensing performance even at room temperature. The influence of the power density and wavelength of UV light used and ambient humidity on the sensor response was systematically investigated. Comparing to the conventional thermal activated one that instead showed preferred response to acetone at 375 oC, the enhanced sensitivity and selectivity of the same sensor at room temperature under LED UV light can be attributed to selective photo-catalytic effect induced by the UV light.

Overexpressed Hsp70 alleviated formaldehyde-induced apoptosis partly via PI3K/Akt signaling pathway in human bronchial epithelial cells.

Formaldehyde (FA) is a ubiquitous environmental pollutant, which can induce apoptosis in lung cell and is related to the pathogenesis of asthma, pneumonia, and chronic obstructive pulmonary disease. Heat shock protein 70 (Hsp70) is an ATP-dependent molecular chaperone and exhibits an anti-apoptosis ability in a variety of cells. Previous studies reported that the expression of Hsp70 was induced when organisms were exposed to FA. Whether Hsp70 plays a role in the FA-induced apoptosis and the involved cell signaling pathway remain largely unknown. In this study, human bronchial epithelial cells with overexpressed Hsp70 and the control were exposed to different concentrations of FA (0, 40, 80, and 160 μmol/L) for 24 hours. Apoptosis and the expression levels of PI3K, Akt, p-Akt, MEK, p-MEK, and GLI2 were detected by Annexin-APC/7AAD double-labeled flow cytometry and western blot. The results showed that overexpression of Hsp70 decreased the apoptosis induced by FA and alleviated the decline of PI3k and p-Akt significantly. Inhibitor (LY 294002, a specific inhibitor of PI3K-Akt) test result indicated that PI3K-Akt signaling pathway was involved in the inhibition of FA-induced apoptosis by Hsp70 overexpression and also active in the maintenance of GLI2 level. However, it also suggested that other signaling pathways activated by overexpressed Hsp70 participated in this process, which was needed to be elucidated in further research.

Synthesis of crosslinked PVA-ceramic composite membrane for phenol removal from aqueous solution

In this study, the thin-film composite membrane (TFCM) was fabricated for phenol?water separation using formaldehyde crosslinked polyvinylalcohol (PVA) coating on fly ash-fuller clay ceramic substrate. Thin film was created using 10 % PVA with different concentrations of formaldehyde (1?5 g). The characterization of synthesized membrane such as swelling and chemical stability, permeation study, molecular weight cut off (MWCO), scanning electron microscopy (SEM) and contact angle analysis was carried out to optimize the membrane. The stability of active layer increases with increase in the amount of formaldehyde, whereas the hydrophilicity, degree of swelling, flux and pore size decrease. The smallest pore (1.91 nm) was obtained in the active layer when PVA crosslinked with 3 g formaldehyde (PF3). Phenol?water separation was conducted with PF3 to optimize the process parameters, such as feed concentration, pH and operating pressure. Maximum phenol separation (85 %) was obtained at 207 kPa for 200 mg L-1 of feed phenol. High phenol removal was found at pH 6.0 and thereafter it decreased in alkaline pH. Phenol removal decreased from 80.6 to 19.8 % with the increase in pressure from 207 to 414 kPa, whereas flux increased from 5.3 to 52.38 L m-2 h-1. The results demonstrate that fabricated CM can be successfully used for phenol?water separation.

Effect of formaldehyde on some post-harvest qualities and shelf-life of selected fruits and vegetables

In Bangladesh, a lot of fruits and vegetables have been accused of having prolonged shelf-life by formaldehyde adulteration. So, an evaluation of the effect of formaldehyde was carried out by treating mango, litchi and oyster mushroom with different concentrations of formaldehyde and assessing their quality parameters. The three samples were dipped in 0%,1%, 5% and 10%formaldehyde solutions for 15 minutes and packed in a modified atmosphere package for observation. Changes in color, texture and weight loss were observed during storage at every alternate day. No significant increase in post-harvest quality and shelf-life was observed for mango and litchi treated with formaldehyde compared to control. Treated mushroom attained elastic texture and remained in this state up to the end of storage, whereas the control spoiled days after storage. Although formaldehyde-treated mushroom showed extended shelf-life, they lost their commercial freshness. The formaldehyde solutions did not have any significant effect on weight loss. So, formaldehyde is not a useful preservative to improve the post-harvest quality and shelf-life of fresh fruits and vegetables.J. Bangladesh Agril. Univ. 16(1): 151-157, April 2018