Microfluidics in gas sensing and artificial olfaction

SCENT-ERC-2014-STG-639123 (2015-2020) UIDB/04378/2020 PTDC/BII-BIO/28878/2017Rapid, real-time, and non-invasive identification of volatile organic compounds (VOCs) and gases is an increasingly relevant field, with applications in areas such as healthcare, agriculture, or industry. Ideal characteristics of VOC and gas sensing devices used for artificial olfaction include portability and affordability, low power consumption, fast response, high selectivity, and sensitivity. Microfluidics meets all these requirements and allows for in situ operation and small sample amounts, providing many advantages compared to conventional methods using sophisticated apparatus such as gas chromatography and mass spectrometry. This review covers the work accomplished so far regarding microfluidic devices for gas sensing and artificial olfaction. Systems utilizing electrical and optical transduction, as well as several system designs engineered throughout the years are summarized, and future perspectives in the field are discussed.publishersversionpublishe

Stable and oriented liquid crystal droplets stabilized by imidazolium ionic liquids

SCENT-ERC-2014-STG-639123(2015-2022) UIDP/04378/2020 UIDB/04378/2020 LA/P/0140/2020Liquid crystals represent a fascinating intermediate state of matter, with dynamic yet or-ganized molecular features and untapped opportunities in sensing. Several works report the use of liquid crystal droplets formed by microfluidics and stabilized by surfactants such as sodium do-decyl sulfate (SDS). In this work, we explore, for the first time, the potential of surface-active ionic liquids of the imidazolium family as surfactants to generate in high yield, stable and oriented liquid crystal droplets. Our results show that [C12MIM][Cl], in particular, yields stable, uniform and mon-odisperse droplets (diameter 74 ± 6 µm; PDI = 8%) with the liquid crystal in a radial configuration, even when compared with the standard SDS surfactant. These findings reveal an additional application for ionic liquids in the field of soft matter.publishersversionpublishe

Optical gas sensing with liquid crystal droplets and convolutional neural networks

UIDB/50009/2020 UIDB/ 04378/2020 SCENT-ERC-2014-STG-639123, 2015-2022Liquid crystal (LC)-based materials are promising platforms to develop rapid, miniaturised and low-cost gas sensor devices. In hybrid gel films containing LC droplets, characteristic optical texture variations are observed due to orientational transitions of LC molecules in the presence of distinct volatile organic compounds (VOC). Here, we investigate the use of deep convolutional neural networks (CNN) as pattern recognition systems to analyse optical textures dynamics in LC droplets exposed to a set of different VOCs. LC droplets responses to VOCs were video recorded under polarised optical microscopy (POM). CNNs were then used to extract features from the responses and, in separate tasks, to recognise and quantify the vapours exposed to the films. The impact of droplet diameter on the results was also analysed. With our classification models, we show that a single individual droplet can recognise 11 VOCs with small structural and functional differences (F1-score above 93%). The optical texture variation pattern of a droplet also reflects VOC concentration changes, as suggested by applying a regression model to acetone at 0.9–4.0% (v/v) (mean absolute errors below 0.25% (v/v)). The CNN-based methodology is thus a promising approach for VOC sensing using responses from individual LC-droplets.publishersversionpublishe

Ionogels based on a single ionic liquid for electronic nose application

165186/2015-1 307501/2019-1 424027/2018-6 grant reference SCENT-ERC-2014-STG-639123 (2015-2020) UIDB/04378/2020 POCI-01-0145-FEDER-007728Ionogel are versatile materials, as they present the electrical properties of ionic liquids and also dimensional stability, since they are trapped in a solid matrix, allowing application in electronic devices such as gas sensors and electronic noses. In this work, ionogels were designed to act as a sensitive layer for the detection of volatiles in a custom-made electronic nose. Ionogels composed of gelatin and a single imidazolium ionic liquid were doped with bare and functionalized iron oxide nanoparticles, producing ionogels with adjustable target selectivity. After exposing an array of four ionogels to 12 distinct volatile organic compounds, the collected signals were analyzed by principal component analysis (PCA) and by several supervised classification methods, in order to assess the ability of the electronic nose to distinguish different volatiles, which showed accuracy above 98%.publishersversionpublishe

Dextran-Coated Magnetic Supports Modified with a Biomimetic Ligand for IgG Purification

The authors thank the financial support from Fundacao para a Ciencia e a Tecnologia through Grant PEst-C/EQB/LA0006/2011 and contracts no. PTDC/EBB-BIO/102163/2008, PTDC/EBB-BIO/098961/2008, PTDC/EBB-BIO/118317/2010, SFRH/BD/72650/2010 for V.L.D, and Santander Totta Bank - Universidade Nova de Lisboa for the Scientific Award 2009/2010. The authors are grateful to Dr. Abid Hussain and M. Telma Barroso (REQUIMTE, FCT-UNL, Portugal) for the preparation of the synthetic affinity ligands, to Lonza Biologics, U.K. (Dr. Richard Alldread), and the Animal Cell Technology Unit of ITQB-UNL/IBET (Dr. Paula M Alves and Dr. Ana Teixeira) for providing the cells and the culture bulks and to Mr. Filipe Cardoso and Prof. Paulo Freitas (INESC-MN, Lisbon, Portugal) for the help with the VSM measurements.Dextran-coated iron oxide magnetic particles modified with ligand 22/8, a protein A mimetic ligand, were prepared and assessed for IgG purification. Dextran was chosen as the agent to modify the surface of magnetic particles by presenting a negligible level of nonspecific adsorption. For the functionalization of the particles with the affinity ligand toward antibodies, three methods have been explored. The optimum coupling method yielded a theoretical maximum capacity for human IgG calculated as 568 ± 33 mg/g and a binding affinity constant of 7.7 × 10⁴ M⁻¹. Regeneration, recycle and reuse of particles was also highly successful for five cycles with minor loss of capacity. Moreover, this support presented specificity and effectiveness for IgG adsorption and elution at pH 11 directly from crude extracts with a final purity of 95% in the eluted fraction.proofpublishe

An odorant-binding protein based electrical sensor to detect volatile organic compounds

This work was funded by the European Research Council (ERC) under the EU Horizon 2020 research and innovation program [SCENTERC-2014-STG-639123, (2015–2022) and Grant Agreement No. 101069405-ENSURE-ERC-2022-POC1], and by national funds from FCT – Fundação para a Ciência e a Tecnologia, I.P., Portugal, for the project PROTEIOS (PTDC/CTM-CTM/3389/2021), for the Research Unit on Applied Molecular Biosciences the Associate Laboratory Institute for Health and Bioeconomy – i4HB (LA/P/0140/2020) and Associated Laboratory for Green Chemistry (LAQV) of the Network of Chemistry and Technology (REQUIMTE) – LAQV/REQUIMTE (UIDP/ 50006/2020). Stimulus, DOI: 10.54499/2022.07088.CEECIND/CP1725/CT0002 (CE).Artificial olfaction systems, such as electronic nose devices (ENs), can be used in various fields, from healthcare to food industry and the environmental sector. ENs consist of an array of sensors composed of different sensing materials. Incorporating Odorant Binding Proteins (OBPs) into gas-sensing materials can increase volatile organic compounds (VOCs) recognition and selectivity. OBPs are small soluble proteins found in vertebrates and insects, responsible for VOCs solubilization and transportation. In this work, OBP3 from Rattus norvegicus was selected to develop an OBP-based electrical VOC sensor, by optimizing protein production and immobilization on sensors surface. OBP3 was successfully produced in E. coli host cells (94 mg/L) and purified with high purity (88% purification yield, 96% purity). The protein folding and thermal stability were assessed by circular dichroism (Tm=71±1ºC) whereas ligand binding activity was verified in solution by fluorescence displacement against diisopropylphenol (Kd=0.24 µM). For the immobilization of OBP3 on gold interdigitated electrodes modified with reduced graphene oxide, we explored two strategies (covalent and non-covalent), establishing a reproducible and cost-effective methodology to develop OBP3-based electrical sensors. The non-covalent immobilization of a linker to the graphene-modified surface showed improved outcomes compared to the carbodiimide crosslinking chemistry. OBP3-sensors presented selectivity towards distinct model compounds in the gas phase (diisopropylphenol, dimethylpyrazine, menthone and decanol), in correlation with the dissociation constants measured by fluorescence displacement assays in solution. As a result, this study expands the practical applications of OBPs for gas-phase sensors, showcasing their potential for enhancing VOC detection.publishersversionpublishe

Effect of conventional and organic fertilizers on volatile compounds of raspberry fruit

Raspberries are widely consumed; the taste of the fruit is determined by the interaction between sugars, organic acids and a set of volatile compounds. Meanwhile, organic agriculture has developed rapidly as an alternative to conventional system and has been driven by the demand for pesticide-free food that brings greater benefits to human health. However, this system can alter the integral quality of the fruit, including the aroma, which has been little studied. Therefore, the objective of this study was to evaluate the effect of the application of organic and conventional fertilizers, in the presence of volatile compounds synthesized in the cv. ‘Heritage’ raspberry, during two crop cycles. The qualitative profile of volatile compounds was analysed by mass gas chromatography, obtaining as a result that fertilization treatments significantly affected the emission of volatile compounds in the most abundant functional group (C13 norisoprenoids) 48.5 vs. 25.8% and 56.9 vs. 29.1% in conventional and organic, in 2017 and 2018, respectively (p ≤ 0.05). The crop cycle affected the concentration of aldehydes (11.2 vs. 30.6% in organic, in 2017 and 2018, respectively (p ≤ 0.05). Impact compounds such as α-ionone (13.92 vs. 9.08% and 25.34 vs. 9.17% in conventional and organic in 2017 and 2018, respectively) and β-ionone (24.93 vs. 14.10% and 22.66 vs. 15.94% in conventional and organic in 2017 and 2018, respectively), presented greater abundance in conventional fertilization (p ≤ 0.05). Since there were changes in the volatile compounds, it is recommended to study whether the consumer perceives these changes

Causas directas de muerte en pacientes diabéticos en el Perú, 2017-2020

Background: Diabetes Mellitus type 2 (DM2) constitutes a global public health problem with high morbidity and mortality rate. Studies reported cardiovascular disease as the main direct cause of death in diabetics, while others attributed it to respiratory diseases. However, in our setting, it is still a question. The objective of our study was to determine the main direct causes of death in diabetic patients of Peru. Material and Methods: Observational, descriptive study. We collected the data from the registry of the “Sistema Informático Nacional de Defunciones” (SINADEF) of Peru from 2017 to 2020. We selected the registries whose ICD-10 corresponds to DM2 to describe the characteristics of the deceased, the direct causes of death and the annual trend of the first five causes. Results: The main direct causes of death in diabetic patients were diseases of the respiratory system (28,0%), diseases of the circulatory system (25,4%) and certain infectious and parasitic diseases (15,0%). In addition, the most affected population was males (50,3%), older adults (76,4%) from the coast region (63,6%). The trend was increasing in the first five causes of death, with the greatest slope between 2019 and 2020 for diseases of the respiratory system (rate 1.40 and 2.96) and diseases of the circulatory system (rate 0.98 and 2.86). Conclusions: The main direct causes of death were diseases of the respiratory and circulatory system. The region with the highest number of deaths was the coast. The trend of the top five causes of death was increasing, with a greater slope between 2019 and 2020.Introducción: La Diabetes Mellitus tipo 2 (DM2) constituye un problema de salud pública mundial con elevada tasa de morbimortalidad. Estudios reportaron como principal causa directa de muerte en diabéticos a las enfermedades cardiovasculares, mientras otros atribuyen a las enfermedades respiratorias. Empero, en nuestro medio aún es una interrogante. El objetivo de nuestro estudio fue determinar las principales causas directas de muerte en pacientes diabéticos en Perú. Materiales y métodos: Se realizó un estudio observacional, descriptivo. Recopilamos los datos del registro del Sistema Informático Nacional de Defunciones (SINADEF) de Perú del año 2017 al 2020, seleccionamos los registros cuyo CIE-10 correspondiera a DM2 para describir las características de los fallecidos, las causas directas de defunción y la tendencia anual de las cinco primeras causas. Resultados: Las principales causas directas de muerte en pacientes diabéticos fueron enfermedades del sistema respiratorio (28,0%), enfermedades del sistema circulatorio (25,4%) y ciertas enfermedades infecciosas y parasitarias (15,0%). Además, se evidenció como población más afectada al sexo masculino (50,3%), adultos mayores (76,4%) y la región costa (63,6%). La tendencia fue creciente en las cinco primeras causas de muerte, con mayor pendiente entre 2019 y 2020 para enfermedades del sistema respiratorio (tasa 1,40 y 2,96) y enfermedades del sistema circulatorio (tasa 0,98 y 2,86). Conclusiones: Las principales causas directas de muerte fueron las enfermedades del sistema respiratorio y circulatorio. La región con mayor cantidad de fallecidos fue la costa. La tendencia de las cinco primeras causas de muerte fue creciente, con mayor pendiente entre 2019 y 2020

Assessing the role of compound drought and heatwave events on unprecedented 2020 wildfires in the Pantanal

The year 2020 had the most catastrophic fire season over the last two decades in the Pantanal, which led to outstanding environmental impacts. Indeed, much of the Pantanal has been affected by severe dry conditions since 2019, with evidence of the 2020's drought being the most extreme and widespread ever recorded in the last 70 years. Although it is unquestionable that this mega-drought contributed significantly to the increase of fire risk, so far, the 2020's fire season has been analyzed at the univariate level of a single climate event, not considering the co-occurrence of extreme and persistent temperatures with soil dryness conditions. Here, we show that similarly to other areas of the globe, the influence of land-atmosphere feedbacks contributed decisively to the simultaneous occurrence of dry and hot spells (HPs), exacerbating fire risk. The ideal synoptic conditions for strong atmospheric heating and large evaporation rates were present, in particular during the HPs, when the maximum temperature was, on average, 6 °C above the normal. The short span of the period during those compound drought-heatwave (CDHW) events accounted for 55% of the burned area of 2020. The vulnerability in the northern forested areas was higher than in the other areas, revealing a synergistic effect between fuel availability and weather-hydrological conditions. Accordingly, where fuel is not a limiting factor, fire activity tends to be more modelled by CDHW events. Our work advances beyond an isolated event-level basis towards a compound and cascading natural hazards approach, simultaneously estimating the contribution of drought and heatwaves to fuelling extreme fire outbreaks in the Pantanal such as those in 2020. Thus, these findings are relevant within a broader context, as the driving mechanisms apply across other ecosystems, implying higher flammability conditions and further efforts for monitoring and predicting such extreme events

Sustainable plant polyesters as substrates for optical gas sensors

UIDB/04378/2020 PTDC/BII-BIO/28878/2017 PTDC/SAU-SER/30388/2017 SFRH-BD-110467-2015The fast and non-invasive detection of odors and volatile organic compounds (VOCs) by gas sensors and electronic noses is a growing field of interest, mostly due to a large scope of potential applications. Additional drivers for the expansion of the field include the development of alternative and sustainable sensing materials. The discovery that isolated cross-linked polymeric structures of suberin spontaneously self-assemble as a film inspired us to develop new sensing composite materials consisting of suberin and a liquid crystal (LC). Due to their stimuli-responsive and optically active nature, liquid crystals are interesting probes in gas sensing. Herein, we report the isolation and the chemical characterization of two suberin types (from cork and from potato peels) resorting to analyses of gas chromatography–mass spectrometry (GC-MS), solution nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS). The collected data highlighted their compositional and structural differences. Cork suberin showed a higher proportion of longer aliphatic constituents and is more esterified than potato suberin. Accordingly, when casted it formed films with larger surface irregularities and a higher C/O ratio. When either type of suberin was combined with the liquid crystal 5CB, the ensuing hybrid materials showed distinctive morphological and sensing properties towards a set of 12 VOCs (comprising heptane, hexane, chloroform, toluene, dichlormethane, diethylether, ethyl acetate, acetonitrile, acetone, ethanol, methanol, and acetic acid). The optical responses generated by the materials are reversible and reproducible, showing stability for 3 weeks. The individual VOC-sensing responses of the two hybrid materials are discussed taking as basis the chemistry of each suberin type. A support vector machines (SVM) algorithm based on the features of the optical responses was implemented to assess the VOC identification ability of the materials, revealing that the two distinct suberin-based sensors complement each other, since they selectively identify distinct VOCs or VOC groups. It is expected that such new environmentally-friendly gas sensing materials derived from natural diversity can be combined in arrays to enlarge selectivity and sensing capacity.publishersversionpublishe