Intense charge transfer plasmons in golden nanoparticle dimers connected by conductive molecular linkers.

Golden nanoparticle dimers connected by conjugated molecular linkers 1,2-bis(2-pyridyl)ethylene are produced. The formation of stable dimers with 22 nm diameter nanoparticles is confirmed by transmission electron microphotography. The possibility of charge transfer through the linkers between the particles in the dimers is shown by the density functional theory calculations. In addition to localized plasmon resonance of solitary nanoparticles with a wavelength of 530 nm, the optical spectra exhibit a new intense absorption peak in the near-infrared range with a wavelength of ∼780 nm. The emergent absorption peak is attributed to the charge-transfer plasmon (CTP) mode; the spectra simulated within the CTP developed model agree with the experimental ones. This resonant absorption may be of interest to biomedical applications due to its position in the so-called transmission window of biological tissues. The in vitro heating of CTP dimer solution by a laser diode with a wavelength of 792 nm proved the efficiency of CTP dimers for achieving a temperature increase of ΔT = 6 °C, which is sufficient for hyperthermia treatment of malignant tumors. This indicates the possibility of using hyperthermia to treat malignant tumors using the material we synthesized.

A hybrid quantum-classical theory for predicting terahertz charge-transfer plasmons in metal nanoparticles on graphene.

Metal nanoparticle (NP) complexes lying on a single-layer graphene surface are studied with a developed original hybrid quantum-classical theory using the Finite Element Method (FEM) that is computationally cheap. Our theory is based on the motivated assumption that the carrier charge density in the doped graphene does not vary significantly during the plasmon oscillations. Charge transfer plasmon (CTP) frequencies, eigenvectors, quality factors, energy loss in the NPs and in graphene, and the absorption power are aspects that are theoretically studied and numerically calculated. It is shown the CTP frequencies reside in the terahertz range and can be represented as a product of two factors: the Fermi level of graphene and the geometry of the NP complex. The energy losses in the NPs are predicted to be inversely dependent on the radius R of the nanoparticle, while the loss in graphene is proportional to R and the interparticle distance. The CTP quality factors are predicted to be in the range ∼10-100. The absorption power under CTP excitation is proportional to the scalar product of the CTP dipole moment and the external electromagnetic field. The developed theory makes it possible to simulate different properties of CTPs 3-4 orders of magnitude faster compared to the original FEM or the finite-difference time domain method, providing possibilities for predicting the plasmonic properties of very large systems for different applications.

Infrared bound states in the continuum: random forest method.

In this Letter, we consider optical bound states in the continuum (BICs) in the infrared range supported by an all-dielectric metasurface in the form of subwavelength dielectric grating. We apply the random forest machine learning method to predict the frequency of the BICs as dependent on the optical and geometric parameters of the metasurface. It is found that the machine learning approach outperforms the standard least square method at the size of the dataset of ≈4000 specimens. It is shown that the random forest approach can be applied for predicting the subband in the infrared spectrum into which the BIC falls. The important feature parameters that affect the BIC wavelength are identified.

[Early progression of glioblastoma before radiotherapy]. / Rannee progressirovanie do luchevoi terapii pri glioblastome.

OBJECTIVE: To analyze the influence of continued growth of glioblastoma between surgery and radiotherapy on subsequent survival. MATERIAL AND METHODS: Fractionation with a prescribed dose of 2 and 3 Gy was alternately applied using a pairwise modeling strategy in 140 patients with morphologically confirmed glioblastoma (grade 4). Early progression of disease between microsurgery and radiotherapy was diagnosed in 60 patients, and no tumor growth was noted in 80 patients. RESULTS: The minimum period of early progression was 0.33 months, maximum - 4.27 months (median 1.1 (95.0% CI: 0.9-1.3)). The most significant predictors of early progression were resection quality (p<0.0001), large residual tumor (p=0.003) and no MGMT promoter methylation (p=0.001). IDH1 status did not affect early progression. In residual tumor ≥1.2 cm3, the median period of early progression was 1.9 months (n=70; 95% Cl: 1.3-2.5), <1.2 cm3 - 3.5 months (n=70; p=0.019). After resection of less than 76% of tumor, this value was 1.1 months (n=28), ≥76% - 3.1 months (n=112; p=0.006). Without tumor growth, the median overall survival was 33.41 months (n=80; 95% Cl: 27.1-39.7), with early progression - 16.03 months (n=60; 95% Cl: 13.5-18.6; p<0.0001). This predictor was significant for fractionation with a prescribed dose of 3 Gy (p<0.0001) and standard radiotherapy (2 Gy; p=0.028). By December 2022, 26 out of 40 patients without early progression survived two years after treatment (3 Gy) (65%, median not reached). In case of fractionation with a prescribed dose of 2 Gy, 20 patients survived this period (50%, median reached). CONCLUSION: Almost half of patients with newly diagnosed glioblastoma develop early progression between microsurgery and radiotherapy. Therefore, patients with and without early progression should be probably assigned to different prognostic groups regarding overall survival.

Possibilities of transmission electron microscopy in assessing the quality of bacterial cells and microbial population.

Determination of changes in the morphostructure of microorganisms under the influence of antibiotics, disinfectants, biocins, physical and chemical agents is carried out using the method of visualization of ultrathin sections in a transmission electron microscope. The aim is to develop methodological techniques for express preparation and visualization of the ultrastructure of bacteria in a transmission electron microscope to detect structural damage to cells and assess the quality of the microbial population. A technique of accelerated sample preparation for visualization of the fine structure of bacteria and diagnosis of structural damage to cells in a transmission electron microscope has been developed. The use of this method will make it possible to more effectively investigate the mechanisms of inactivation of microorganisms at different stages of contact with antibiotics, disinfectants, biocines, including various stressful, damaging and lethal physical and chemical effects.

Peculiarities of the ultrastructure of mixed biofilms of the causing agent of diphtheria and conditionally pathogenic microorganisms isolated from the human respiratory tract.

In the post-epidemic period, the circulation of the causative agent of diphtheria in the population is maintained due to the carrier of bacteria. Entering an organism with a high level of antitoxic immunity, the pathogen enters into intermicrobial interactions with representatives of the opportunistic microflora inhabiting the respiratory tract and forms a biofilm. MATERIALS AND METHODS: Modeling of the biofilm formation process was carried out using the strains C.diphtheriae gravis tox+№. 665, C.pseudodiphtheriticum, S.aureus. Biofilm samples were placed on the stage of a scanning electron microscope and gold-sputtered in an EicoIB-3 ioncoater vacuum deposition unit (Eico, Japan) at an ion current of 6-8 mA. The samples obtained were examined in a JEOL 6510LB scanning electronmicroscope. («JEOL¼ company, Japan) at an accelerating voltage of 30 kV. RESULTS: Electron microscopic examination of samples of biofilms C. diphtheriae gravis tox+ № 665 and opportunistic microorganisms shows groups of 2-7 young bacterial cells packed into a single microcapsule. Much more voluminous accumulations of bacterial cells (more than 10-12) are typical for biofilm samples represented by C. diphtheriae gravis tox+№ 665 and S. aureus cells. On the surface of the biofilm, young bacterial cells with an intact structure are located at various stages of active division. The conglomerates of bacterial cells, covered with a common intermicrobial matrix, adhere tightly to each other and form a multilayer biofilm. CONCLUSION: Features of the ultrastructure of biofilms containing strains of C. diphtheriae and opportunistic bacteria, especially antibiotic-resistant bacteria inhabiting the respiratory tract, can contribute to long-term persistence of the pathogen of diphtheria in the body. They not only significantly complicate the access of antibacterial drugs, but also interfere with the isolation of C.diphtheriae during bacteriological research.

Charge transfer plasmons in the arrays of nanoparticles connected by conductive linkers.

Charge transfer plasmons (CTPs) that occur in different topology and dimensionality arrays of metallic nanoparticles (NPs) linked by narrow molecular bridges are studied. The occurrence of CTPs in such arrays is related to the ballistic motion of electrons in thin linkers with the conductivity that is purely imaginary, in contrast to the case of conventional CTPs, where metallic NPs are linked by thick bridges with the real optical conductivity caused by carrier scattering. An original hybrid model for describing the CTPs with such linkers has been further developed. For different NP arrays, either a general analytical expression or a numerical solution has been obtained for the CTP frequencies. It has been shown that the CTP frequencies lie in the IR spectral range and depend on both the linker conductivity and the system geometry. It is found that the electron currents of plasmon oscillations correspond to minor charge displacements of only few electrons. It has been established that the interaction of the CTPs with an external electromagnetic field strongly depends on the symmetry of the electron currents in the linkers, which, in turn, are fully governed by the symmetry of the investigated system. The extended model and the analytical expressions for the CTPs frequencies have been compared with the conventional finite difference time domain simulations. It is argued that applications of this novel type of plasmon may have wide ramifications in the area of chemical sensing.

[Short-term survival prediction scale in patients with metastatic brain disease caused by lung and breast cancer]. / Shkala prognoza kratkosrochnoi vyzhivaemosti pri metastaticheskom porazhenii golovnogo mozga u bol'nykh rakom legkogo i molochnoi zhelezy.

OBJECTIVE: To develop a prognostic scale suitable for distinguishing a group of poor prognosis with low survival prior to deciding on the appropriateness of radiotherapy. MATERIAL AND METHODS: We analyzed only those patients with reliably known date of death after previous WBRT to determine objective criteria allowing WBRT abandonment. WBRT was carried out in 100 patients with non-small cell lung cancer (n=49) and breast cancer (n=51) and confirmed metastatic brain disease. All procedures have been conducted at the radiotherapy department of the Herzen Moscow Oncology Research Institute since January 2014. The prescribed dose of 3 Gy was ensured in all patients. Total focal dose of 30 Gy delivered in 10 fractions was achieved in 77 cases, 36 Gy delivered in 12 fractions - in 23 cases. RESULTS: Death date was recorded in all patients (n=100) by January 2020. In the electronic SPSS database, death information was digitized for each patient up to 2-24 months, respectively. We identified eight the most significant factors by using of correlation analysis: primary tumor (controlled (0), uncontrolled (1)), number of brain metastases (<17 (0), ≥17 (1)), volume of brain metastases (<48 cm3 (0) ≥48 cm3 (1)), extracranial control (no metastases (0), metastases with positive dynamics after chemotherapy (1), continued growth after chemotherapy (2)), metastatic lesion of liver and lungs, respectively (no (0), yes (1)), functional status (≥ 70% (0), ≤ 60% (1)), carcinomatosis of the meninges (no (0), yes (1)). A simple summation of digital variables for factors 1-8 in each patient resulted a prognostic scale. Low risk of early mortality after WBRT was determined by 0-3 scores, intermediate risk - 4-5 scores, high risk - 6-9 scores. According to univariate analysis (log-rank 0.000), median survival rate varied in these groups: low risk - 15.5 months (11.4-19.7), intermediate risk - 5.26 months (4.6-6.0), high risk - only 1.35 months (0.9-1.8). Only 1 out of 15 high-risk patients (6-9 scores) survived 3 months (3.25 months). Inclusion of all eight factors into multivariate analysis revealed significant impact of only risk group on short-term survival. A 3-month survival in the high-risk group was 20.6 times lower (p=0.002) compared to the low and intermediate risk groups. CONCLUSION: High significance of prognostic model and low informative value of each of the included factors emphasize the advisability of determining risk groups for short-term survival according to the suggested scale for each patient scheduled for WBRT. A simple assessment of separate predictors is pointless to decide whether WBRT is necessary.

Engineering novel tunable optical high-Q nanoparticle array filters for a wide range of wavelengths.

The interaction of non-monochromatic radiation with arrays comprising plasmonic and dielectric nanoparticles has been studied using the finite-difference time-domain electrodynamics method. It is shown that LiNbO3, TiO2, GaAs, Si, and Ge all-dielectric nanoparticle arrays can provide a complete selective reflection of an incident plane wave within a narrow spectral line of collective lattice resonance with a Q-factor of 103 or larger at various spectral ranges, while plasmonic refractory TiN and chemically stable Au nanoparticle arrays provide high-Q resonances with moderate reflectivity. Arrays with fixed dimensional parameters make it possible to fine-tune the position of a selected resonant spectral line by tilting the array relative to the direction of the incident radiation. These effects provide grounds for engineering novel selective tunable optical high-Q filters in a wide range of wavelengths, from visible to middle-IR.

Collective lattice resonances in arrays of dielectric nanoparticles: a matter of size.

Collective lattice resonances (CLRs) in finite-sized $ 2D $2D arrays of dielectric nanospheres have been studied via the coupled dipole approximation. We show that even for sufficiently large arrays, up to $ 100 \times 100 $100×100 nanoparticles (NPs), electric or magnetic dipole CLRs may differ significantly from the ones calculated for infinite arrays with the same NP sizes and interparticle distances. The discrepancy is explained by the existence of a sufficiently strong cross-interaction between electric and magnetic dipoles induced at NPs in finite-sized lattices, which is ignored for infinite arrays. We support this claim numerically and propose an analytic model to estimate a spectral width of CLRs for finite-sized arrays. Given that most of the current theoretical and numerical researches on collective effects in arrays of dielectric NPs rely on modeling infinite structures, the reported findings may contribute to thoughtful and optimal design of inherently finite-sized photonic devices.

Identification and characterization of lumpy skin disease virus isolated from cattle in the Republic of North Ossetia-Alania in 2015.

The first notifications of the unknown disease of cattle appeared in September-October 2015 in North Caucasus region of Russia (Republic of North Ossetia-Alania). The clinical signs included watery discharge from eyes, apathy, loss of appetite, salivation, lameness and nodular skin lesions. Capripoxvirus genome was detected by real-time PCR in the tissue samples of sick animals. The aetiological agent was isolated in the primary cell cultures of lamb testis and goat testis, as well as in the continuous MDBK cell culture. Further sequencing of the GPCR gene and phylogenetic analysis showed the close genetic relationship of isolated capripoxvirus with a group of lumpy skin disease virus. Koch's postulates were fulfilled by the experimental infection of four calves with a suspension of tissue samples from sick animals.

Target Cell Glycosylation Determines the Biodistribution of Plant Lectin Viscumin.

We studied the possibility of using viscumin lectin (MLI) for targeted delivery of antitumor drugs. Affinity of MLI for more than 600 oligosaccharide structures was determined and the glycosylation profiles of cell surface in various mouse tissues were analyzed. It was found that biodistribution of MLI was determined by not only expression of oligosaccharides specifically recognized by the lectin in tissue cells, but also by the structure of glycan in general.

[Hypofractionated radiotherapy for glioblastoma: changing the radiation treatment paradigm]. / Gipofraktsionirovanie pri glioblastomakh: izmenenie paradigmy luchevogo lecheniia.

Hypofractionation has the dual advantage of increased cell death with a higher dose per fraction and a reduced effect of accelerated tumor cell repopulation due to a shorter overall treatment time. However, the potential advantage may be offset by increased toxicity in the late-responding neural tissues. Recently, investigators have attempted delivering radical doses of HFRT by escalating the dose in the immediate vicinity of the enhancing tumor and postoperative surgical cavity and reported reasonable outcomes with acceptable toxicity levels. Three different studies of high-dose HFRT have reported on the paradoxical phenomenon of improved survival in patients developing radiation necrosis at the primary tumor site. The toxicity criteria of RTOG and EORTC have defined clinically or radiographically suspected radionecrosis as Grade 4 toxicity. However, most patients diagnosed with radiation necrosis in the above studies remained asymptomatic. Furthermore, the probable association with improved survival would strongly argue against adopting a blind approach for classifying radiation necrosis as Grade 4 toxicity. The data emerging from the above studies is encouraging and strongly argues for further research. However, the majority of these studies are predominantly retrospective or relatively small single-arm prospective series that add little to the overall quality of evidence. Notwithstanding the above limitations, HFRT appears to be a safe and feasible strategy for glioblastoma patients.

Suppression of surface plasmon resonance in Au nanoparticles upon transition to the liquid state.

Significant suppression of resonant properties of single gold nanoparticles at the surface plasmon frequency during heating and subsequent transition to the liquid state has been demonstrated experimentally and explained for the first time. The results for plasmonic absorption of the nanoparticles have been analyzed by means of Mie theory using experimental values of the optical constants for the liquid and solid metal. The good qualitative agreement between calculated and experimental spectra support the idea that the process of melting is accompanied by an abrupt increase of the relaxation constants, which depends, beside electron-phonon coupling, on electron scattering at a rising number of lattice defects in a particle upon growth of its temperature, and subsequent melting as a major cause for the observed plasmonic suppression. It is emphasized that observed effect is fully reversible and may underlie nonlinear optical responses of nanocolloids and composite materials containing plasmonic nanoparticles and their aggregates in conditions of local heating and in general, manifest itself in a wide range of plasmonics phenomena associated with strong heating of nanoparticles.

Preparation of Viscumin-Ferromagnetic Particles Conjugate and Study of Its Internalization by Human Glioblastoma A172 Cells.

Magnetite particles modified by polyethylene glycol with a molecular weight of 3 kDa and hydrodynamic diameter of ~60 nm were used. Plant lectin viscumin covalently immobilized on these nanoparticles retained its binding activity. Immunochemical characteristics of conjugated viscumin were evaluated using monoclonal antibodies. The resultant conjugate with a hydrodynamic diameter of 70 nm was used for studies of binding and internalization by target cells. Binding of viscumin and its conjugate was determined by receptors containing terminal galactose, while intracellular distribution varied. The model system presented in this study can be used for creation of drugs for target therapy.

[Features of biofilm morphology, formed by Corynebacterium diphtheriae gravis tox+ strains].

AIM: Study the structure of homogenous microbial communities of Corynebacterium diphtheriae gravis tox+ strains during formation of biofilms in vitro. MATERIALS AND METHODS: Object of study--typical and biofilm cultures of C. diphtheriae gravis tox+ museum and circulating strains. Intensity of biofilm formation was evaluated by OD on microplate reader at 540 nm wave length studying 120 and 720 hour cultures. S-450 (Hitachi, Japan) scanning electron microscope was used. RESULTS: The peak of exopolysaccharide matrix (EPS) formation, that is formed in the process of biofilm formation, by museum strain takes place at earlier terms of cultivation (120 hours) than circulating (720 hours). An inverse correlation was established during analysis of bacterial cells of museum and circulating strains of C. diphtheriae during biofilm formation between them and intensity of EPS formation. At maximum EPS content, that took place at various terms of cultivation of the 2 studied strains of diphtheria causative agent, a reduction of corynebacteria cells was observed. CONCLUSION: Bacterial biofilms of museum and circulating strains of C. diphtheriae and patterns of dynamics of EPS reflect, probably, adaptive abilities of the causative agent, that determine its competitiveness in the fight for adhesion sites, resistance to factors of natural immunity and as a result--prolonged persistence in the organism of bacterial carriers.

Experimental investigations into capability of terahertz surface plasmons to bridge macroscopic air gaps.

Results of experimental and theoretical studies of the capability of terahertz surface plasmons (SPs) to cross macroscopic air gaps in a substrate (or between substrates) with admissible losses are presented. SPs were launched with quasi-cw free-electron laser radiation with 130 µm wavelength (λ). We managed to detect SPs passing across gaps as wide as 100 mm (or about 10(3)⋅λ), which is very promising for development of terahertz SP circuitry. The phenomenon was harnessed for splitting an SP beam into two new ones, guided by their own individual plane-surface substrates.

Resonant angular conversion in a Fabry-Perot resonator holding a dielectric cylinder.

Light transmission through a Fabry-Perot resonator (FPR) holding a dielectric cylinder rod is considered. For the cylinder parallel to mirrors of the FPR and the mirrors mimicked by the δ functions we present an exact analytical theory. It is shown that light transmits only for resonant incident angles, α(m), similar to the empty FPR. However after transmission the light scatters into different resonant angles, α(m'), performing resonant angular conversion. We compare the theory with experiment in the FPR, exploring multilayer films as the mirrors and glass cylinder with diameter coincided with the distance between the FPR mirrors. The measured values of angular light conversion agree qualitatively with the theoretical results.