Combination of the electronic nose with microbiology as a tool for rapid detection of Salmonella.

Salmonella is one of the most important foodborne pathogens and its analysis in raw and processed products is mandatory in the food industry. Although microbiological analysis is the standard practice for Salmonella determination, these assays are commonly laborious and time-consuming, thus, alternative techniques based on easy operation, few manipulation steps, low cost, and reduced time are desirable. In this paper, we demonstrate the use of an e-nose based on ionogel composites (ionic liquid + gelatine + Fe3O4 particles) as a complementary tool for the conventional microbiological detection of Salmonella. We used the proposed methodology for differentiating Salmonella from Escherichia coli, Pseudomonas fluorescens, Pseudomonas aeruginosa, and Staphylococcus aureus in nonselective medium: pre-enrichment in brain heart infusion (BHI) (incubation at 35 °C, 24 h) and enrichment in tryptone soy agar (TSA) (incubation at 35 °C, 24 h), whereas Salmonella differentiation from E. coli and P. fluorescens was also evaluated in selective media, bismuth sulfite agar (BSA), xylose lysine deoxycholate agar (XLD), and brilliant green agar (BGA) (incubation at 35 °C, 24 h). The obtained data were compared by principal component analysis (PCA) and different machine learning algorithms: multilayer perceptron (MLP), linear discriminant analysis (LDA), instance-based (IBk), and Logistic Model Trees (LMT). For the nonselective media, under optimized conditions, taking merged data of BHI + TSA (total incubation time of 48 h), an accuracy of 85% was obtained with MLP, LDA, and LMT, while five separated clusters were presented in PCA, each cluster corresponding to a bacterium. In addition, for evaluation of the e-nose for discrimination of Salmonella using selective media, considering the combination of BSA + XLD and total incubation of 72 h, the PCA showed three separated and well-defined clusters corresponding to Salmonella, E. coli, and P. fluorescens, and an accuracy of 100% was obtained for all classifiers.

A Highly Sensitive Molecularly Imprinted Polymer (MIP)-Coated Microwave Glucose Sensor.

A novel, low-cost, sensitive microwave microfluidic glucose detecting biosensor incorporating molecularly imprinted polymer (MIP) is presented. The sensing device is based on a stub resonator to characterize water glucose solutions. The tip of one of the stubs is coated with MIP to increase the selectivity of the sensor and hence the sensitivity compared to the uncoated or to the coated with non-imprinted polymer (NIP) sensor. The sensor was fabricated on a FR4 substrate for low-cost purposes. In the presence of the MIP, the sensor loaded with a glucose solution ranging from 50 mg/dL to 400 mg/dL is observed to experience an absorption frequency shift of 73 MHz when the solutions flow in a microfluidic channel passing sensing area, while the lower limit of detection (LLD) of the sensor is discovered to be 2.4 ng/dL. The experimental results show a high sensitivity of 1.3 MHz/(mg/dL) in terms of absorption frequency.

Influence of design and material characteristics on 3D printed flow-cells for heat transfer-based analytical devices.

Redesigning 3D-printed flow cells is reported used for heat transfer based detection of biomolecules from a flow-through system to an addition-type measurement cell. The aim of this study is to assess the performance of this new measurement design and critically analyse the influence of material properties and 3D printing approach on thermal analysis. Particular attention is paid to reduce the time to stabilisation, the sample volume in order to make the technique suitable for clinical applications, and improving the sensitivity of the platform by decreasing the noise and interference of air bubbles. The three different approaches that were studied included a filament polylactic acid cell using only fused filament fabrication (FFF), a resin cell printed using stereolitography (SLA), and finally a design made of copper, which was manufactured by combining metal injection moulding (MIM) with fused filament fabrication (FFF). Computational fluid dynamic (CFD) modelling was undertaken using ANSYS Fluent V18.1 to provide insight into the flow of heat within the measurement cell, facilitating optimisation of the system and theoretical response speed.It was shown that the measurement cells using SLA had the lowest noise (~ 0.6%) and shortest measurement time (15 min), whereas measurement cells produced using other approaches had lower specificity or suffered from voiding issues. Finally, we assessed the potential of these new designs for detection of biomolecules and amoxicillin, a commonly used beta lactam antibiotic, to demonstrate the proof of concept. It can be concluded that the resin addition-type measurement cells produced with SLA are an interesting affordable alternative, which were able to detect amoxicillin with high sensitivity and have great promise for clinical applications due to the disposable nature of the measurement cells in addition to small sample volumes.

iPSC culture expansion selects against putatively actionable mutations in the mitochondrial genome.

Therapeutic application of induced pluripotent stem cell (iPSC) derivatives requires comprehensive assessment of the integrity of their nuclear and mitochondrial DNA (mtDNA) to exclude oncogenic potential and functional deficits. It is unknown, to which extent mtDNA variants originate from their parental cells or from de novo mutagenesis, and whether dynamics in heteroplasmy levels are caused by inter- and intracellular selection or genetic drift. Sequencing of mtDNA of 26 iPSC clones did not reveal evidence for de novo mutagenesis, or for any selection processes during reprogramming or differentiation. Culture expansion, however, selected against putatively actionable mtDNA mutations. Altogether, our findings point toward a scenario in which intracellular selection of mtDNA variants during culture expansion shapes the mutational landscape of the mitochondrial genome. Our results suggest that intercellular selection and genetic drift exert minor impact and that the bottleneck effect in context of the mtDNA genetic pool might have been overestimated.

Ionogels Based on a Single Ionic Liquid for Electronic Nose Application.

Ionogel 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%.

Enhanced Gas Sensing with Soft Functional Materials.

The materials described in this work result from the self-assembly of liquid crystals and ionic liquids into droplets, stabilized within a biopolymeric matrix. These systems are extremely versatile gels, in terms of composition, and offer potential for fine tuning of both structure and function, as each individual component can be varied. Here, the characterization and application of these gels as sensing thin films in gas sensor devices is presented. The unique supramolecular structure of the gels is explored for molecular recognition of volatile organic compounds (VOCs) by employing gels with distinct formulations to yield combinatorial optical and electrical responses used in the distinction and identification of VOCs.

Design and Evolution of an Opto-electronic Device for VOCs Detection.

Electronic noses (E-noses) are devices capable of detecting and identifying Volatile Organic Compounds (VOCs) in a simple and fast method. In this work, we present the development process of an opto-electronic device based on sensing films that have unique stimuli-responsive properties, altering their optical and electrical properties, when interacting with VOCs. This interaction results in optical and electrical signals that can be collected, and further processed and analysed. Two versions of the device were designed and assembled. E-nose V1 is an optical device, and E-nose V2 is a hybrid opto-electronic device. Both E-noses architectures include a delivery system, a detection chamber, and a transduction system. After the validation of the E-nose V1 prototype, the E-nose V2 was implemented, resulting in an easy-to-handle, miniaturized and stable device. Results from E-nose V2 indicated optical signals reproducibility, and the possibility of coupling the electrical signals to the optical response for VOCs sensing.

Identification of Tobacco Types and Cigarette Brands Using an Electronic Nose Based on Conductive Polymer/Porphyrin Composite Sensors.

Three tobacco types (Burley, Flue Cured, and Oriental) and eight cigarette brands were unequivocally identified using an electronic nose formed by only three sensors based on a single novel conducting polymer (PF-BTB) doped with different porphyrins (H2TPP, H2TPFP, and H2BTBOP). The synthesis and characterization of the polymer are also discussed. Small changes in the porphyrin structure caused significant changes in the electrical conductance response patterns of the sensors upon exposure to complex chemical matrixes, representing a novel approach for tuning the selectivity of chemiresistive sensors for e-nose application. This e-nose is fast, cheap, reliable, can be easily operated, and could be a valuable tool for border agents fighting cigarette smuggling around the world, helping them prevent losses of millions in tax revenues and sales.

Tilapia fish microbial spoilage monitored by a single optical gas sensor.

As consumption of fish and fish-based foods increases, non-destructive monitoring of fish freshness also becomes more prominent. Fish products are very perishable and prone to microbiological growth, not always easily detected by organoleptic evaluation. The analysis of the headspace of fish specimens through gas sensing is an interesting approach to monitor fish freshness. Here we report a gas sensing method for monitoring Tilapia fish spoilage based on the application of a single gas sensitive gel material coupled to an optical electronic nose. The optical signals of the sensor and the extent of bacterial growth were followed over time, and results indicated good correlation between the two determinations, which suggests the potential application of this simple and low cost system for Tilapia fish freshness monitoring.

Determination of neutral diols and carboxylic acids formed during glycerol electrooxidation by capillary electrophoresis with dual C4D.

Methods for determination of glycerol and its electrooxidation products (neutral diols and carboxylates) by capillary electrophoresis (CE) with dual capacitively coupled contactless conductivity detectors (C4D) are presented. Glycerol, dihydroxyacetone and glyceraldehyde were detected as anionic borate complexes in less than 3min under counter Electroosmotic Flow (EOF) mode (resolution of the critical pair of 1.8). Limits of detection (LODs) of 15, 15 and 10µmolL-1 were obtained for glycerol, dihydroxyacetone and glyceraldehyde, respectively. Two methods of separation were used for the separation of carboxylates. The first one used the same Back Ground Electrolyte (BGE) containing borate, and the second used a BGE (pH 6.1) composed by 2-(N-morpholino)ethanesulfonic acid (MES), L-Histidine and a flow modifier. Better separation and LODs for carboxylates were obtained using Mes/Histidine as BGE. However, along with the non-applicability of this BGE to the determination of neutral diols, observation of the C4D signals at two different points of the capillary (10 and 50cm apart from the injection tip) revealed interaction of the flow modifier with some species (mesoxalate and glyoxylate). The electrooxidation of a glycerol sample in alkaline media on an 8cm2 gold working electrode was evaluated by the developed methods. After 16h of electrolysis, 87% of the glycerol had been oxidized and formate, glycolate, hydroxypyruvate and glycerate were detected as the main products.

Tunable Gas Sensing Gels by Cooperative Assembly.

The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels' structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli.

A conductive polymer based electronic nose for early detection of Penicillium digitatum in post-harvest oranges.

We describe the construction of an electronic nose, comprising four chemiresistive sensors formed by the deposition of thin conductive polymer films onto interdigitated electrodes, attached to a personal computer via a data acquisition board. This e-nose was used to detect biodeterioration of oranges colonized by Penicillium digitatum. Significant responses were obtained after only 24 h of incubation i.e. at an early stage of biodeterioration, enabling remedial measures to be taken in storage facilities and efficiently distinguishing between good and poor quality fruits. The instrument has a very low analysis time of 40 s.

Investigation of the conformational changes of a conducting polymer in gas sensor active layers by means of polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS).

Polarization-Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS) was employed to observe the changes in the molecular conformation of poly(2-phenyl-1,4-xylylene) (PPPX) films that occurred after exposure to organic solvent vapors. The PPPX films were supported on solid matrixes by casting, spin-coating, and Langmuir-Blodgett (LB) techniques. The results show that the polymer is sensitive to the solvent vapors, which affect some of the vibration dipole moments, as detected by PM-IRRAS. The sensitivity depends on the method employed to immobilize the polymer, with more significant changes in films formed using techniques that result in a less systematically organized conformation. This feature enables the use of surface vibration spectroscopy to detect organic solvent vapors and may be applied in an artificial nose.

O papel da radiologia em odontologia legal / The role of radiology in forensic dentistry

Vários métodos säo empregados na identificaçäo de restos humanos, sendo que a maioria é baseada na comparaçäo entre dados ante-mortem e post-mortem disponíveis. Embora a técnica da impressäo digital seja considerada a mais precisa, em muitos casos ela näo pode ser utilizada, especialmente quando os corpos foram mutilados, decompostos, queimados ou fragmentados. Nestas situaçöes, os métodos empregados pela Odontologia Legal tornam-se extremamente valiosos, uma vez que os dentes e as restauraçöes säo muito resistentes à destruiçäo pelo fogo, preservando numerosas características individuais. Assim, oferecem a possibilidade de uma identificaçäo acurada e aceita pelas autoridades legais. Este breve artigo de revisäo descreve os principais avanços alcançados pela Odontologia Legal, nos últimos 25 anos, quanto ao emprego de radiografias ante-e post-mortem no processo de identificaçäo. Dentre os diversos assuntos tratados, destacam-se: suportes especialmente confeccionados para facilitar o posicionamento e a fixaçäo de filmes radiológicos intra-orais em falecidos com rigor mortis; dispositivos para facilitar a reproduçäo da geometria de imagens com as de ante-mortem; métodos envolvendo radiografias digitalizadas, as quais podem ser facilmente manipuladas por métodos computacionais, armazenadas e transmitidas por "modem" aos locais de desastre em massa; procedimentos para determinaçäo de idade, identificaçäo de indivíduos desdentados por meio da comparaçäo de radiografias oclusais do maxilar e estudos de validaçäo de radiografias tiradas com intervalos ante-e port-mortem de até 30 anos