Search

Introduction: Acanthamoeba spp. are free-living parasites increasingly implicated in causing Acanthamoeba keratitis (AK). AK is diagnosed by demonstration of parasites in corneal samples by direct microscopy, culture, and nucleic acid amplification. Most commonly, corneal scrapings are sent to the laboratory smeared between two glass slides. These scrapings are suitable for direct microscopy but less suitable for culture and polymerase chain reaction (PCR) which, in turn, are more sensitive for the diagnosis of AK. Aim: The aim of the study was to explore better alternatives for transporting corneal scrapings from the point-of-care eye center to the concerned laboratories. Materials and Methods: The study used small Parafilm (Bemis Company Inc., USA) squares (PSs) of 1 cm each prepared by cutting Parafilm using a surgical blade under sterile conditions. Each of the four different dilutions of Acanthamoeba suspension (15, 30, 60, and 120 cells) was used in this study. Each dilution was added onto the surface of 36 PSs and kept at room temperature for 24-h, 48-h, and 72-h incubation. The PSs for one particular time point and dilution were used for calcofluor white staining, its inoculation onto the surface of nonnutrient agar having a lawn of Escherichia coli, and Acanthamoeba-specific PCR amplification. In addition, two PSs inoculated with 30 cells and incubated for 24 h and 72 h were used for scanning electron microscopy (SEM). Results and Conclusion: All three diagnostic techniques, i.e. microscopy, culture, and PCR, detected the presence of Acanthamoeba at all the tested concentrations and time points. However, the growth pattern on culture changed directly in proportion to increased incubation periods and increased concentration of inoculum. In addition, the adherence of Acanthamoeba to the Parafilm was confirmed by SEM; these results suggest the use of these PSs as a suitable matrix for the transport of corneal scrapings. [ABSTRACT FROM AUTHOR]

[Display omitted] Evaporation of surfactant droplets on leaves is complicated due to the complex physical and chemical properties of the leaf surfaces. However, for certain leaf surfaces for which the evaporation process appears to follow the standard constant-contact-radius or constant-contact-angle modes, it should be possible to mimic the droplet evaporation with both a well-chosen synthetic surface and a relatively simple mathematical model. Surfactant droplet evaporation experiments were performed on two commercial crop species, wheat and capsicum, along with two synthetic surfaces, up to a 90° incline. The time-dependence of the droplets' contact angles, height, volume and contact radius was measured throughout the evaporation experiments. Mathematical models were developed to simulate the experiments. With one clear exception, for all combinations of surfaces, surfactant concentrations and angles, the experiments appear to follow the standard evaporation modes and are well described by the mathematical models (modified Popov and Young–Laplace-Popov). The exception is wheat with a high surfactant concentration, for which droplet evaporation appears nonstandard and deviates from the diffusion limited models, perhaps due to additional mechanisms such as the adsorption of surfactant, stomatal density or an elongated shape in the direction of the grooves in the wheat surface. [ABSTRACT FROM AUTHOR]

We have been able to maintain a continuous culture of Myzus persicae (Sulzer) (Hemiptera: Aphididae) on a fully defined artificial diet at Reading, UK, for over 30 years, without any return to plants. Following multiple requests from aphid researchers, here we provide the details of our culturing method. Detailed instructions are given for rearing M. persicae on the diet. An improved recipe is included as well as the construction and changing of diet sachets. [ABSTRACT FROM AUTHOR]

Objective: Parafilm M® is a moisture-resistant thermoplastic commonly used to seal Nematode Growth Media (NGM) agar plates on which the nematode Caenorhabditis elegans is cultured. This practice reduces media dehydration and microbial contamination. However, the effects on C. elegans individuals of placing this barrier between the external environment and the interior of the NGM plate are currently unknown. Our research aims to determine if this common practice engenders developmental changes, such as growth, that could subsequently and unintentionally alter experimental data. We compared the larval growth over 48 h of animals cultured on Parafilm-wrapped and unwrapped control NGM plates. Results: Wrapping culture plates with Parafilm significantly accelerated and increased larval growth, with a 0.87 μm/h increase in growth rate (~ 6%) and a 37.90 μm increase in the change in growth (Δgrowth; ~ 5%) over 48 h. Therefore, C. elegans investigators should be aware that wrapping their experimental cultures with Parafilm may result in statistically detectable changes in worm growth and possibly other developmental processes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel approach for the fabrication of free-standing graphene oxide (GO) films. • Green reduction of GO films into reduced graphene oxide (RGO) films. • Approach for the preparation of highly conductive RGO films. • Application of RGO films in oil/water separation. Abstract Free-standing films of graphene oxide (GO) are regarded as potential materials for numerous applications in different fields. However, fabricating macroscopic free-standing GO films with high throughput is a bottleneck in large-scale application of these films. Here we introduce a method suitable for the mass-scale fabrication of free-standing GO films by exploring paraffin film (Parafilm M®) as a sacrificial substrate. The method involves deposition of GO on a paraffin film and peeling of the paraffin film after swelling it with toluene to obtain free-standing film of GO. Furthermore, the GO films were reduced into highly conductive RGO films using a green reducing agent ascorbic acid. A strategy of treating GO films with CuSO 4 solution prior to reduction is also designed to avoid the possible disintegration of GO films in ascorbic acid solution. A detailed comparative study on the properties of RGO films prepared via thermal and chemical treatment and through the combination of both is also reported. An investigation of the variation in the electrical conductivity of the RGO films based on the reduction method is also carried out. The hydrophobic nature of the thermally reduced RGO films is explored for the oil/water separation. [ABSTRACT FROM AUTHOR]

Herein, we evaluated the use of paper towel, waxed paper, and Parafilm M® (Heathrow Scientific, Vernon Hills, IL, USA) as alternative substrates for screen-printed sensor manufacturing. Morphological study was performed to evaluate the adhesion of the ink on these uncommon substrates, as well as the morphology of the working electrode. The electrochemical characterization was carried out using ferricyanide/ferrocyanide as redox couple. To enhance the electrochemical properties of the developed sensors, the nanomaterial carbon black was used as nanomodifier. The modification by drop casting of the working electrode surface, using a stable dispersion of carbon black, allows to obtain a sensor with improved electrochemical behavior in terms of peak-to-peak separation, current intensity, and the resistance of charge transfer. The results achieved confirm the possibility of printing the electrode on several cost-effective paper-based materials and the improvement of the electrochemical behavior by using carbon black as sustainable nanomaterial. [ABSTRACT FROM AUTHOR]

In this article, we first report a simple fabrication technique to create Parafilm®-laminated microfluidic paper-based analytical devices (µPADs) with a high resolution and then introduce novel engineered detection zones (D-zones) to enhance color uniformity without any chemical modifications. The Parafilm®-heating-laser cutting fabrication method comprises of three steps: 1) flattening a Parafilm® layer on paper, 2) heating in an oven at 90 °C for 30 min, and 3) CO 2 laser ablation of the patterns. This method enabled laminated µPADs with a minimum barrier width of 172 ± 15 µm, with resistance to various organic solvents and surfactant solutions. Using this technique, µPADs with two types of engineered D-zones were fabricated. The multi-inlet D-zone had four micro-inlets (<500 µm width), enabling sample entrance into the D-zone from four directions simultaneously towards the center. The segmented D-zone had four segments each with its own micro-inlet allowing for separate reactions to occur in miniaturized segments simultaneously. Using an enzymatic glucose assay for the colorimetric reaction, the multi-inlet and segmented D-zones significantly decreased color gradient from 28.77 ± 1.49 to 12.35 ± 1.18 and 8.95 ± 0.98 %, respectively, compared to the conventional devices. We further used the µPADs with segmented D-zones for the detection of glucose in artificial urine in the clinically relevant range of 2–50 mM, where R2 > 0.99 of the fitted curve showed an excellent correlation between the generated signals and the glucose concentrations. Also, compared to the conventional devices, the engineered D-zones showed improved precision and reproducibility and a better linear range. Finally, spiked real human urine samples were tested, demonstrating the applicability of the engineered devices for real-world applications. Overall, with a simple fabrication method and a novel design for color uniformity, this paper contributes to the advancement of µPADs and paves the way towards commercialization. [Display omitted] • A simple method to fabricate Parafilm®-laminated µPADs is explained. • Small computer-designed channels can be created with resistance against different chemicals. • Two engineered detection zones are introduced: multi-inlet and segmented. • The novel detection zones enhanced color uniformity of glucose assay significantly. • The devices were able to detect glucose in complex matrices, i.e., real urine samples. [ABSTRACT FROM AUTHOR]

Abstract: The roles that the impact velocity (Vi ) and the drop size (D 0) play for water drops impinging on parafilm surfaces were systematically investigated for systems of entrapped air bubbles. Entrapped bubbles were successfully observed by using a high-speed video camera system from a 45-degree top view. A half-closed region on the Vi –D 0 plot was identified for the formation of the entrapped bubble. The upper and lower boundaries of Vi tended to decrease as D 0 increased. The entrapped bubble generally took the shape of a hemispherical bubble after settling down on the parafilm surface. Bubble sizes became smaller when Vi approached the upper and lower limits. A monotonically increasing correlation between Re and We at a fixed drop size has been reported in the literature. This monotonic relationship was shown to be dependent on the drop size. Moreover, two main different mechanisms for the formation of entrapped air bubbles were proposed for water on parafilm systems. [Copyright &y& Elsevier]

Abstract: A variety of materials has been applied to neuronal cell culture substrates to improve the efficiency of the culture and to provide pertinent cell growth environment. Here we report the application of Parafilm® M (‘Parafilm’) as a novel substrate for neuronal culture and patterning. Cell culture results show that elastic Parafilm had effects on cell viability, length and number of neurites, and soma spreading. Parafilm was also an effective substrate to obtain patterned neuronal cultures using a conventional micro-contract printing (μCP) technique. Polylysine micropatterns in line or grid forms were readily transferred from PDMS stamp to bare Parafilm surfaces and spatially confined neuronal cultures were successfully maintained for over three weeks. We also demonstrate that batch-processing cell culture substrates can be easily fabricated using a piece of Parafilm. The softness, plasticity, and hydrophobicity were main features that made it attractive for Parafilm to be considered as a practical cell culture platform. The results can be extended to develop an inexpensive and practical neuronal culture substrates in tissue engineering and biochip applications. [Copyright &y& Elsevier]

Abstract: A study on the initial wetting velocity (V w0) for a water droplet impinging on glass and parafilm surfaces was performed using a fast-speed video camera system. The silhouette images were recorded sequentially from the moment the droplet made contact with the solid surface. The profile of the droplet during spreading revealed the droplet-wetting diameter (especially in the first millisecond), then the wetting velocity was determined. The relaxation of the wetting velocity, V w(t), was investigated at five different impact velocities (V i). The value of V w0 was found to be a few meters per second; V w then decreased dramatically in a few ms to approximately 1/10 of V w0. Moreover, the V w for water on parafilm became negative (i.e., retraction started) at approximately 2–3ms (dimensionless time t*∼1). A general phenomenon was observed: (i) a higher V i results in a larger V w0; (ii) at the first millisecond, the wetting velocity was dominated primarily by V i and was nearly independent of the surface hydrophobicity; (iii) for t >2ms, the V w depends mainly on the surface hydrophobicity; and (iv) for t =1–3ms, the V w for the droplet with higher V i became smaller for both solid substrates while the droplet continued spreading. [Copyright &y& Elsevier]

In the present study, using a high-fidelity digital microscope, we observed the sequence of appressorial development on the germ tubes of a powdery mildew fungus isolated from red clover leaves. Based on its morphological characteristics and rDNA internal transcribed spacer (ITS) sequences, the fungus was identified as Erysiphe trifoliorum, and one of its isolates, designated as KRCP-4N, was used in this work. The conidial germination of isolate KRCP-4N was studied on host (red clover) and non-host (barley) leaves, as well as on an artificial hydrophobic membrane (Parafilm). More than 90% of conidia germinated synchronously and developed dichotomous appressoria (symmetrical double-headed appressoria) on all substrata used. On host leaves, all appressorium-forming conidia developed hyphae (colony-forming hyphae) from conidial bodies without extending germ tubes from the tips of the appressoria. On non-host leaves and on Parafilm-covered glass slides, however, all conidia extended germ tubes from one side of dichotomous appressoria (two-step germination). In addition to the dichotomous appressoria, we detected a few conidia that produced hooked appressoria and extended germ tubes from the tip of the appressorium. Penetration attempts by KRCP-4N conidia on barley leaves were impeded by papillae formed at penetration sites beneath these two types of appressorium. From these results, we conclude that the 'two-step germination' of E. trifoliorum KRCP-4N conidia is the result of an unsuccessful penetration attempt, causing diversity in appressorial shape. [ABSTRACT FROM AUTHOR]

Plant parts are commonly used as oviposition substrates for mass rearing of Orius spp., but this system does not permit the isolation of clean intact eggs for use as standards in a yolk protein enzyme-linked immunosorbent assay (ELISA). An oviposition substrate was devised for O. insidiosus by forming water-filled domes from Parafilm-M. Eggs were deposited through the Parafilm skin into water where they remained viable for at least 24 h. Eggs were extracted from the domes mad collected onto black filter paper and then used to prepare lyophilized yolk protein as a quantitative standard in ELISA tests. In no-choice tests, O. insidiosus females oviposited 5.86 eggs per female per d into 'Blue Lake' green beans, Phaseohts vulgaris L., and 3.06 eggs into water-filled domes. Hatch rates did not significantly differ, although optimal moisture was critical. In a choice test. O. insidiosus females preferred beans to domes (4.02 versus 0.03 eggs per female per 18 h). Females preferred to oviposit into the wails of the major groove of green beans and often oviposited around the lower perimeter of water-filled domes, Lyophilized protein from eggs collected in water-filled domes was successfully and replicably used in the yolk protein ELISA after compensating for reduced immunological activity with a correction factor. Parafilm-covered water-filled domes are therefore useful for collection of eggs for use in the yolk protein ELISA and for other applications that require viable eggs. These domes also may lead to discovery of the phytochemical and physical factors that are responsible for choice of a host plant and its parts for oviposition. [ABSTRACT FROM AUTHOR]