Analysis of Electric Field Distribution for SOI-FET Sensors with Dielectrophoretic Control.

Silicon-on-insulator (SOI) nanowire or nanoribbon field-effect transistor (FET) biosensors are versatile platforms of electronic detectors for the real-time, label-free, and highly sensitive detection of a wide range of bioparticles. At a low analyte concentration in samples, the target particle diffusion transport to sensor elements is one of the main limitations in their detection. The dielectrophoretic (DEP) manipulation of bioparticles is one of the most successful techniques to overcome this limitation. In this study, TCAD modeling was used to analyze the distribution of the gradient of the electric fields E for the SOI-FET sensors with embedded DEP electrodes to optimize the conditions of the dielectrophoretic delivery of the analyte. Cases with asymmetrical and symmetrical rectangular electrodes with different heights, widths, and distances to the sensor, and with different sensor operation modes were considered. The results showed that the grad E2 factor, which determines the DEP force and affects the bioparticle movement, strongly depended on the position of the DEP electrodes and the sensor operation point. The sensor operation point allows one to change the bioparticle movement direction and, as a result, change the efficiency of the delivery of the target particles to the sensor.

Effect of local UV radiation on the morphofunctional state of the skin of guinea pigs in early and remote periods after irradiation.

OBJECTIVE: The aim is to establish the features of morphological and morphometric changes in the skin of guinea pigs in erythemal, early post-erythemal and late post-erythemic periods after local ultraviolet irradiation. PATIENTS AND METHODS: Materials and methods: Studies were conducted on 54 albino guinea pigs weighing 400-500 g. Ultraviolet erythema was caused by irradiation in 1 minimum erythemal dose. The control group included intact guinea pigs. After 2, 4 hours, on the 3rd, 8th, 15th, 21st, 28th day, the fragments of the irradiated skin were investigated using histochemical and morphometric methods. RESULTS: Results: After 2, 4 hours after irradiation, dyscirculatory changes in the skin develop. By the 3rd day of the experiment a morphological picture of acute inflammation in the epidermis and dermis develops, apoptotic keratinocytes appear (sunburn cells), which is accompanied by thickening of the epidermis and an increase in the density of fibroblasts. By the 8th day proliferative-hyperplastic and degenerative changes begin to prevail, including dystrophic nature, the thickness of the epidermis and the density of fibroblasts reach a maximum. In the long term, on the 15-28th day, dystrophic changes of the epidermis, dyskeratosis, changes in the number and structure of elastic fibers with an increase in uneven fibrosis, collagenization processes and the development of sclerotic changes, as well as a significant thickening of the epidermis, an increase in the density of fibroblasts are observed. CONCLUSION: Conclusions: The data obtained indicate pronounced morphofunctional changes in the skin in the zone of local ultraviolet irradiation observed throughout the entire observation period.

1,2,3,4-Tetrafluorobiphenylene: A Prototype Janus-Headed Scaffold for Ambipolar Materials.

The title compound was synthesized by Ullmann cross-coupling in low yield as the first representative of [n]phenylene containing hydrocarbon and fluorocarbon rings. Stille/Suzuki-Miyaura cross-coupling reactions, as well as substitution of fluorine in suitable starting compounds, failed to give the same product. The geometric and electronic structures of the title compound were studied by X-ray diffraction, cyclic voltammetry and density functional theory calculations, together with Hirshfeld surface and reduced density gradient analyses. The crystal structure features head-to-tail π-stacking and other fluorine-related secondary bonding interactions. From the nucleus-independent chemical shifts descriptor, the four-membered ring of the title compound is antiaromatic, and the six-membered rings are aromatic. The Janus molecule is highly polarized; and the six-membered fluoro- and hydrocarbon rings are Lewis π-acidic and π-basic, respectively. The electrochemically-generated radical cation of the title compound is long-lived as characterized by electron paramagnetic resonance, whereas the radical anion is unstable in solution. The title compound reveals electrical properties of an insulator. On expanding its molecular scaffold towards partially fluorinated [n]phenylenes (n≥2), the properties presumably can be transformed into those of semiconductors. In this context, the title compound is suggested as a prototype scaffold for ambipolar materials for organic electronics and spintronics.

SOI nanowire for the high-sensitive detection of HBsAg and α-fetoprotein.

Silicon-on-isolator-nanowires (SOI-NWs) were used for the label-free, real-time biospecific detection of the hepatitis B marker HBsAg and cancer marker α-fetoprotein (AFP). Specific protein-protein recognition was carried out using individual NWs that were functionalized with antibodies. To solve the problem of non-specific binding of target protein molecules to the sensor element the use of a reference NW with immobilized antibodies against non-target proteins was proposed. Using individual SOI-NW surface functionalization allowed the fabrication of a NW array, containing working NWs and reference NWs within one chip. It was shown that this approach allows us to reach a detection limit up to 10(-14) and 10(-15) M for HBsAg and AFP, respectively. Our investigations also allowed us to reveal the influence of the charged state of the target protein molecules and antibodies in solutions with various pH values on the target protein detection limit. A high sensitivity NW-detector is of interest for the creation of diagnosticums for hepatitis B and for the early stages of cancer diseases.