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Rapid, yet accurate and sensitive testing has been shown to be critical in the control of spreading pandemic diseases such as COVID-19. Current methods which are highly sensitive and can differentiate different strains are slow and cannot be conveniently applied at the point of care. Rapid tests, meanwhile, require a high titer and are not sufficiently sensitive to discriminate between strains. Here, we report a rapid and facile potentiometric detection method based on nanoscale, three-dimensional molecular imprints of analytes on a self-assembled monolayer (SAM), which can deliver analyte-specific detection of both whole virions and isolated proteins in microliter amounts of bodily fluids within minutes. The detection substrate with nanoscale inverse surface patterns of analytes formed by a SAM identifies a target analyte by recognizing its surface nano- and molecular structures, which can be monitored by temporal measurement of the change in substrate open-circuit potential. The sensor unambiguously detected and differentiated H1N1 and H3N2 influenza A virions as well as the spike proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Middle-East respiratory syndrome (MERS) coronavirus in human saliva with limits of detection reaching 200 PFU/mL and 100 pg/mL for the viral particles and spike proteins, respectively. The demonstrated speed and specificity of detection, combined with a low required sample volume, high sensitivity, ease of potentiometric measurement, and simple sample collection and preparation, suggest that the technique can be used as a highly effective point-of-care diagnostic platform for a fast, accurate, and specific detection of various viral pathogens and their variants. [ABSTRACT FROM AUTHOR]

Despite successful applications of solution-processed organic–inorganic hybrid perovskites (OIHPs) such as archetypical methylammonium lead iodide (MAPI) in high-performance optoelectronic devices including solar cells and light emitting diodes, their application in field-effect transistors (FETs) remains relatively limited due to the unresolved issues caused by ion migration in OIHPs, such as screening of gate electric fields, lowered device on-off ratios and field-effect mobility, and large hysteresis in the FET transfer characteristics. Here, we report improved performances of the MAPI-based FET via a polymer-additive-based grain boundary (GB) passivation approach that suppresses the ion migration. Polycaprolactone (PCL) was incorporated into the MAPI FET as a GB-passivation additive as confirmed by scanning electron and atomic force microscopies. Unlike the typical n-type behavior and large transfer hysteresis in the starting, pristine MAPI FETs, the GB passivation by PCL led to a drastically reduced hysteresis in FET transfer characteristics, while hinting at an ambipolar transport and slight improvement in mobility, indicating a reduced ion migration in the PCL-incorporated MAPI FET. The effect of PCL GB passivation in suppressing ion migration was directly confirmed by the measured, increased activation energy for ion migration in the PCL-incorporated MAPI. The results not only represent the first report of the polymer-additive-based mitigation of the ion migration in the MAPI FET but also suggest potential utilities of the approach for enabling high-performance OIHP FETs and electronic devices in general. [ABSTRACT FROM AUTHOR]

Metacomposites are an interesting field of research. This research is regarding tunable magnetic metacomposite formed using graphene and polyethylene (PE). Dielectric measurements show that as the concentration of graphene was increased in PE–graphene nanocomposites, the separation between graphene sheets decreased and negative dielectric constant was observed at low frequencies while high dielectric constant was observed at high frequencies of the applied field. The switching frequency could be controlled by changing the graphene concentrations. Small angle neutron scattering (SANS) analysis showed that the graphene assembled as fractals in the nanocomposites. As more graphene was incorporated into the nanocomposites, the fractals gave rise to percolation. We propose that the fractals are the building blocks for percolation phenomenon in the PE–graphene nanocomposites. Also, we observed ferromagnetism in the PE–graphene nanocomposites till 30% graphene. At 40% graphene the nanocomposite becomes a diamagnet. We attribute this to the topological defects induced in graphene by PE. Theses PE–graphene magnetic meta composites can have potential applications in battery technology. [ABSTRACT FROM AUTHOR]

This work focuses on dielectric measurements and small-angle neutron scattering (SANS) analysis of polyurethane–graphene nanocomposite that is conducting and of low density. In this research graphene nanoplatelets were used. Polyurethane and graphene were mixed in appropriate weight proportions to make polyurethane–graphene (PU–graphene) nanocomposites. The porosity is decreased with an increase in graphene concentration. The dielectric characteristics such as dielectric constant, dielectric loss, loss tangent, and electric modulus were influenced by the graphene concentration. The conductivity (S/cm) increased rapidly by (~ 4 × 109 times) when the graphene concentration was increased to 30% and it indicates the formation of conducting pathways at high concentrations of graphene. SANS analysis showed that polyurethane has micellar structure and graphene assembles as fractals in the foams leading to conduction pathways in the nanocomposites. This research could benefit creation of lightweight materials for electronics. [ABSTRACT FROM AUTHOR]

Bi-metallic patterns with array of Pt discs decorated by Au rings were fabricated onto the substrate by a templated-self-assembly procedure in which multi-step self-assembly processes were involved. The original pattern was established by using the breath figure method. The bi-metallic sample with Au rings exhibited rather high sensitivity as well as great reproducibility within the array in surface-enhanced Raman scattering test. [ABSTRACT FROM AUTHOR]

We report neutron reflectivity and dynamic secondary ion mass spectroscopy measurements of surface segregation from symmetric, isotopic polystyrene blends, spin coated onto oxide covered silicon wafers, as a function of film thickness. The results of this analysis show that the segments of the deuterated polymer always partition to both the air and the substrate interfaces. Furthermore, the surface segregation is affected significantly if the film thicknesses are reduced below ∼four times the correlation length in the systems, and the segregation to both surfaces decreases with decreasing thickness. These results are in good agreement with the predictions of a mean-field lattice model which incorporates composition and chain length independent values of the surface energy parameter χs at each surface. [ABSTRACT FROM AUTHOR]

Abstract: The role of a tertiary polymer‐based additive is investigated in increasing the efficiency of inverted low bandgap polymer:fullerene bulk heterojunction (BHJ) solar cells. Charge separation in polymer BHJ solar cells relies on the phase separation between electron accepting fullerene derivatives and photoactive polymers. Proper distribution of individual phases of suitable crystallinities within the active layer is a key factor for efficient charge transport/extraction and high photovoltaic performance. Here, it is demonstrated that the minor addition of a tertiary amorphous polymer, polystyrene (PS), with optimized molecular weights can increase the overall photovoltaic efficiency of poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)]:phenyl‐C61butyric acid methyl ester (PCDTBT:PCBM) inverted BHJ solar cells, through the interfacial‐tension‐driven increase in crystallinities of photoactive phases and redistribution of PCBM molecules away from the top hole‐collecting anode interface. Complementary studies correlating polymer interfacial tension, blend internal structure, charge transport, and photovoltaic characteristics show that tertiary, high molecular‐weight polymers can serve as effective additives for improving the performance of low bandgap polymer solar cells. [ABSTRACT FROM AUTHOR]

A mechanical stimulus and chemical induction by dexamethasone have been important factors in dental pulp stem cell (DPSC) differentiation and biomineralization. We have demonstrated that the enzymatically crosslinked gelatin hydrogels are extremely effective substrates for DPSC differentiation towards odontoblasts. DPSCs were seeded on the crosslinked hard (∼8 kPa) and soft (∼0.15 kPa) gelatin hydrogels for 35 days with and without dexamethasone. Odontogenic differentiation markers such as OCN, ALP and DSPP were upregulated after 35 days of culture on crosslinked hydrogels with and without dexamethasone. SEM and Alizarin red staining of the crosslinked hydrogels showed a biomineralized sheet of hydroxyapatite deposits laid by the DPSCs on the top surface and inside the hydrogel. We found that the DPSC differentiation and biomineralization were independent of the hydrogel stiffness and dexamethasone. We hypothesize that this biomineralization was indeed triggered by the surface chemistry of the crosslinked gelatin hydrogels since we did not observe any biomineralization on the uncrosslinked gelatin or mTG. We also showed that the DPSCs, when removed from hard hydrogel surfaces and re-seeded on a TCPS, retained their odontogenic lineage and showed a permanent mineralization effect. Our results show the potential of enzymatically crosslinked gelatin hydrogels as scaffolds for dentin regeneration. [ABSTRACT FROM AUTHOR]

Fibroblast migration is critical to the wound healing process. In vivo, migration occurs on fibrillar substrates, and previous observations have shown that a significant time lag exists before the onset of granulation tissue. We therefore conducted a series of experiments to understand the impact of both fibrillar morphology and migration time. Substrate topography was first shown to have a profound influence. Fibroblasts preferentially attach to fibrillar surfaces, and orient their cytoplasm for maximal contact with the fiber edge. In the case of en-mass cell migration out of an agarose droplet, fibroblasts on flat surfaces emerged with an enhanced velocity, v = 52μm/h, that decreases to the single cell value, v = 28μm/h within 24 hours and remained constant for at least four days. Fibroblasts emerging on fibrillar surfaces emerged with the single cell velocity, which remained constant for the first 24 hours and then increased reaching a plateau with more than twice the initial velocity within the next three days. The focal adhesions were distributed uniformly in cells on flat surfaces, while on the fibrillar surface they were clustered along the cell periphery. Furthermore, the number of focal adhesions for the cells on the flat surfaces remained constant, while it decreased on the fibrillar surface during the next three days. The deformation of the cell nuclei was found to be 50% larger on the fiber surfaces for the first 24 hours. While the mean deformation remained constant on the flat surface, it increased for the next three days by 24% in cells on fibers. On the fourth day, large actin/myosin fibers formed in cells on fibrillar surfaces only and coincided with a change from the standard migration mechanism involving extension of lamellipodia, and retraction of the rear, to one involving strong contractions oriented along the fibers and centered about the nucleus. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) are currently used in numerous medical applications. Herein, we describe their in vitro impact on human adipose-derived stromal cells (ADSCs) using 13 nm and 45 nm citrate-coated AuNPs. In their non-differentiated state, ADSCs were penetrated by the AuNPs and stored in vacuoles. The presence of the AuNPs in ADSCs resulted in increased population doubling times, decreased cell motility and cell-mediated collagen contraction. The degree to which the cells were impacted was a function of particle concentration, where the smaller particles required a sevenfold higher concentration to have the same effect as the larger ones. Furthermore, AuNPs reduced adipogenesis as measured by lipid droplet accumulation and adiponectin secretion. These effects correlated with transient increases in DLK1 and with relative reductions in fibronectin. Upon removal of exogenous AuNPs, cellular NP levels decreased and normal ADSC functions were restored. As adiponectin helps regulate energy metabolism, local fluctuations triggered by AuNPs can lead to systemic changes. Hence, careful choice of size, concentration and clinical application duration of AuNPs is warranted. [ABSTRACT FROM AUTHOR]

Compact fluorescent light (CFL) bulbs can provide the same amount of lumens as incandescent light bulbs, using one quarter of the energy. Recently, CFL exposure was found to exacerbate existing skin conditions; however, the effects of CFL exposure on healthy skin tissue have not been thoroughly investigated. In this study, we studied the effects of exposure to CFL illumination on healthy human skin tissue cells (fibroblasts and keratinocytes). Cells exposed to CFLs exhibited a decrease in the proliferation rate, a significant increase in the production of reactive oxygen species, and a decrease in their ability to contract collagen. Measurements of UV emissions from these bulbs found significant levels of UVC and UVA (mercury [Hg] emission lines), which appeared to originate from cracks in the phosphor coatings, present in all bulbs studied. The response of the cells to the CFLs was consistent with damage from UV radiation, which was further enhanced when low dosages of TiO2 nanoparticles (NPs), normally used for UV absorption, were added prior to exposure. No effect on cells, with or without TiO2 NPs, was observed when they were exposed to incandescent light of the same intensity. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) are used in many applications; however, their interactions with cells and potential health risk(s) are not fully known. In this manuscript, we describe the interactions of AuNPs with human dermal fibroblasts and show that they can penetrate the plasma membrane and accumulate in large vacuoles. We also demonstrate that the uptake of the AuNPs is a function of time, their size and concentration. Specifically, we demonstrate that 45 nm AuNPs penetrate cells via clathrin-mediated endocytosis, while the smaller 13 nm enter mostly via phagocytosis. Furthermore, we provide evidence of cytoskeleton filament disruption as a result of AuNPs exposure and reconstitution during recovery (following AuNP removal), despite no changes in actin or beta-tubulin protein levels. In contrast, the expression of the extracellular matrix (ECM) proteins, collagen and fibronectin, was diminished in the cells exposed to AuNPs. We also examined the proliferation rates of cells exposed to AuNPs and show that its diminution is a function of apoptosis and speculate that apoptosis results from the number of vacuoles present in the cells, which is probably the main factor that disrupts the cytoskeleton causing cell area contraction and decreases in motility. Lastly, we also present data that indicates that AuNPs' damage to cells is not permanent and that the cells can completely recover as a function of AuNPs' size, concentration and exposure time. Taken together, our data suggest that AuNPs exert detrimental effects on cell function that could reverse following AuNPs removal. [ABSTRACT FROM AUTHOR]

We used the electrospinning technique to produce fibrous scaffolds of poly(methyl methacrylate) (PMMA). Using a rotating drum, we aligned the fibers and formed multilayered structures where both the fiber spacing and pore size could be varied. We then plated adult human dermal fibroblasts and studied the effect of fiber diameter and orientation on the cell conformation, integrin receptor expression, proliferation, and migration. We found that a critical diameter minimum diameter existed, D0 5 0.97 lm for cell orientation to occur. For D < D0, no big difference in aspect ratio was observed relative to the control samples on PMMA thin film. Hence, we could fabricate substrate patterned with fibers of different diameters where different cell conformations coexisted on the same scaffold. On the other hand, staining for vinculin proteins in the cells indicated that on large diameter fibers and on flat surfaces, the integrin receptors followed the cell perimeter. On the very small diameter surfaces, the receptors were distributed uniformly along the cell. Cell dynamics studies indicated that the proliferation and migration were also affected by the fiber orientation. [ABSTRACT FROM AUTHOR]

Although microbes have been used in industrial and niche applications for several decades, successful immobilization of microbes while maintaining their usefulness for any desired application has been elusive. Such a functionally bioactive system has distinct advantages over conventional batch and continuous-flow microbial reactor systems that are used in various biotechnological processes. This article describes the use of polyethylene oxide99-polypropylene oxide67-polyethylene oxide99 triblock polymer fibers, created via electrospinning, to encapsulate microbes of 3 industrially relevant genera, namely, Pseudomonas, Zymomonas, and Escherichia. The presence of bacteria inside the fibers was confirmed by fluorescence microscopy and SEM. Although the electrospinning process typically uses harsh organic solvents and extreme conditions that generally are harmful to bacteria, we describe techniques that overcome these limitations. The encapsulated microbes were viable for several months, and their metabolic activity was not affected by immobilization; thus they could be used in various applications. Furthermore, we have engineered a microbe-encapsulated cross-linked fibrous polymeric material that is insoluble. Also, the microbe-encapsulated active matrix permits efficient exchange of nutrients and metabolic products between the microorganism and the environment. The present results demonstrate the potential of the electrospinning technique for the encapsulation and immobilization of bacteria in the form of a synthetic biofilm, while retaining their metabolic activity. This study has wide-ranging implications in the engineering and use of novel bio-hybrid materials or biological thin-film catalysts. [ABSTRACT FROM AUTHOR]

Flame-retardant Elvacite acrylic resin/Cloisite 6A nanocomposites were prepared via direct melt intercalation. Transmission electron microscopy micrographs showed that 75% of the clay platelets were completely exfoliated. This high degree of exfoliation resulted in a large improvement in thermal stability and UV absorption properties without sacrificing optical clarity. Cone calorimetry tests clearly showed that the heat release rate was far lower and more gradual in the nanocomposites than in pure resins. Thermal gravimetric analysis measurements showed that the thermal stability of nanocomposites was enhanced by almost 50°C (at 50 wt% loss) when the samples were thermally degraded under nitrogen. These results are consistent with a dramatic increase in the specific heat of the nanocomposites as verified by high precision differential scanning calorimetry measurements. Additionally, Fourier transform infrared spectroscopy results indicated that the introduction of clay did not change the chemical structure of acrylic resins. [ABSTRACT FROM AUTHOR]

A method for the measurement of Hildebrand solubility parameter has been developed. This method was based on the measurement of the sessile drop contact angle and contact base width during its evaporation. Experimental results showed that this method is accurate and insensitive to the measurement conditions. The major advantages of this method are that it is time efficient and requires a small amount of liquid (microliter) for the measurement. [ABSTRACT FROM AUTHOR]