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The paper discusses schemes for implementing magneto-mechanical anticancer therapy and the most probable scenarios of damaging mechanical effects on the membranes of malignant cells by targeted magnetic nanoparticles (MNPs) selectively bound to membrane mechanoreceptors employing aptamers. The conditions for the selective triggering of the malignant cell apoptosis in a low-frequency non-heating alternating magnetic field, corresponding to the exceeding threshold value of the force acting on the membrane and its mechanoreceptors, are established using a nanoparticle dynamic simulation. The requirements for the functionality of MNPs and their suitability for biomedical applications are analyzed. Attention is paid to the possibility of the formation of magnetite nanoparticle aggregates in an external magnetic field and their localization near tumor cell membranes. It is shown that the scenario involving the process of aggregation of magnetite nanoparticles provides a sufficient magneto-mechanical impact to achieve a therapeutic effect. A possible explanation for the experimentally established fact of successful application of magneto-mechanical therapy using magnetite nanoparticles is presented, in which complete suppression of the Ehrlich carcinoma in an alternating magnetic field as a response to a magneto-mechanical stimulus was demonstrated. This result confirmed the possibility of using the method for high efficiency treatment of malignant neoplasms. The paper provides an extensive review of key publications and the state of the art in this area.

The Brownian dynamics method is employed to study the formation of an electrical double layer (EDL) on the metal nanoparticle (NP) surface in hydrosols during adsorption of electrolyte ions from the interparticle medium. Also studied is the charge accumulation by NPs in the Stern layer. To simulate the process of the formation of EDL, we took into account the effect of image forces and specific adsorption, dissipative and random forces, and the degree of hydration of adsorbed ions on the EDL structure. The employed model makes it possible to determine the charge of NPs and the structure of EDL. For the first time, the charge of both the diffuse part of EDL and the dense Stern layer has been determined. A decrease in the electrolyte concentration (below c

Mostly forsaken, but revived after the emergence of all-dielectric nanophotonics, the Kerker effect can be observed in a variety of nanostructures from high-index constituents with strong electric and magnetic Mie resonances. A necessary requirement for the existence of a magnetic response limits the use of generally nonmagnetic conventional plasmonic nanostructures for the Kerker effect. In spite of this, we demonstrate here the emergence of the lattice Kerker effect in regular plasmonic Al nanostructures. Collective lattice oscillations emerging from the delicate interplay between Rayleigh anomalies and localized surface plasmon resonances both of electric and magnetic dipoles, and electric and magnetic quadrupoles result in suppression of the backscattering in a broad spectral range. Variation of geometrical parameters of Al arrays allows for tailoring the lattice Kerker effect throughout UV and visible wavelength ranges, which is close to impossible to achieve using other plasmonic or all-dielectric materials. It is argued that our results set the ground for wide ramifications in the plasmonics and further application of the Kerker effect.

We have established numerically the physical pattern and conditions for formation of nanosized bubbles in aqueous medium around biocompatible plasmonic nanoparticles (NPs) selectively bound to the membrane of the malignant cells by means of DNA-aptamers under the action of picosecond laser radiation. The results obtained are based on the finite volume method and hydrodynamic models underlying the ANSYS Fluent package with extended capabilities. We have found the main features and previously unknown dominant factors of the damage effect on the cell membrane at the moment of the bubble nucleation around the plasmonic NPs of different types taking into account the influence of the closely located membrane. Information on the kinetics of spatial distribution of pressure, temperature and the relative proportion of vapor in the ‘nanoparticle-membrane-medium’ system have been obtained. The attention is drawn to the advantages of using biocompatible, perfectly absorbing core–shell plasmonic NPs for anti-tumor therapy characterized by an increased mechanical effect on malignant cell membranes at lower laser radiation intensity and the spectral position of their plasmon resonance (λ = 700 nm) in the hemoglobin transparency range. This ensures penetration of laser radiation deep into tissues. The paper is provided with an extensive review of key publications and the state-of-art in this area.

We numerically investigate the conditions for the laser-induced formation of nanobubbles in aqueous medium around plasmonic nanoparticles (NPs) bound to the malignant cell membranes that is considered as the method of their irreversible damage. We proposed employing the versatile and accessible simulation software as a research tool based on the finite volume method underlying the ANSYS Fluent package and supplemented with our user-defined functions that adapt it to solution of the stated problems. This adaptation allows to verify the model using experimental data for the same conditions. We determined the conditions for the pressure growth on the cell membrane at the initial moment of bubble formation significantly exceeding the threshold of irreversible damage. The model can be used for investigation of hydrodynamic effects accompanying irradiation of plasmonic NPs using both different types of pulsed lasers and ideally absorbing NPs with resonance in the hemoglobin spectral transparency range, as well as to uncover previously unknown effects. They include the conditions for localization of a damaging factor non-affecting the normal cells, the conditions for generation of ultrahigh pressure pulse that enables to damage the cell membrane and precedes formation of thin vapor shell around NPs, which, unlike large bubbles, requires registration using highly sensitive experimental measurements. An extensive overview of key publications summarizing the state-of-art in this area is presented.

We have studied the dynamic and static processes occurring in disordered multiparticle colloidal Ag aggregates with natural structure and affecting their plasmonic absorption spectra under pico- and nanosecond pulsed laser radiations, as well as the physical origin responsible for these processes. We have shown that depending on the duration of the laser pulse, the mechanisms of laser modification of such aggregates can be associated both with changes in the resonant properties of the particles due to their heating and melting (picosecond irradiation mode) and with the particle shifts in the resonant domains of the aggregates (nanosecond pulses) which depend on the wavelength, intensity, and polarization of the radiation. These mechanisms result in formation of a narrow dip in the plasmonic absorption spectrum of the aggregates near the laser radiation wavelength and affect the shape and position of the dip. The effect of polydispersity of nanoparticle aggregates on laser photochromic reaction has been studied.

Laser cooling of ions of electron – ion plasma is studied under the action of spontaneous radiation pressure forces. It is shown that the use of a constant detuning of the laser frequency from the quantum transition frequency w0 in ions significantly limits the conditions under which the ions are cooled. To extend the range of initial temperatures of possible cooling of ions and to increase the cooling efficiency we suggest scanning the laser frequency detuning so that the cooling rate remained maximal in the process of changing the temperature of ions. In the case of an optimal detuning, we have found an asymptotic expression for the cooling rate and identified intervals of electron concentrations and temperatures, where cooling of ions is possible.

Variations in the extinction spectra of aggregates of plasmon-resonant nanoparticles are studied at different stages of their planar deformation during interaction with dielectric substrates. Deformation and extinction spectra are calculated by the Brownian dynamics and coupled dipole methods, respectively. The effect of planar deformation of the aggregates on the pattern of the extinction contour in the range of the plasmon absorption band is analyzed by the example of aggregated silver hydrosols. It is shown that the extinction spectra of three-dimensional nanoparticle aggregates formed in bulk and those deformed upon deposition onto a substrate are markedly different. The calculation results are confirmed by experimental data.

The effect of defects such as vacancies, dislocations, and interstices on the extinction spectra of colloidal crystals consisting of plasmon resonance silver nanoparticles is investigated. The possibility of using extinction spectra for the express monitoring of individual and combined defects is discussed.

The effect of the temperature of a silver sol on its extinction spectra during formation of aggregates of plasmon resonance nanoparticles with varying degree of order and the effect exerted on these spectra by changes in the structure of a colloidal crystal during its heating, which lowers elastic properties of a polymer adsorption layer of particles are studied.

Changes in extinction spectra of nanostructured colloids of plasmon resonance particles are studied at different stages of their crystallization. The spontaneous crystallization is calculated by the method of Brownian dynamics, and the extinction spectra are calculated by the method of coupled dipoles. Based on the example of silver sols, we analyzed how separate parameters of the crystallizing disperse system affect the shape of the extinction contour in the plasmon absorption band.

Reasons for the appearance of defects of various types in crystalline colloidal structures formed during the self-organization of the ensembles of spherical nanoparticles are analyzed using lyosols of metal nanoparticles stabilized with polymers as examples. Quantitative characteristic of the degree of imperfection of colloidal crystals is proposed and the procedures for the minimization of the degree of imperfection are discussed. Order-disorder phase transitions of colloidal crystals are studied.

The kinetics of the formation of crystalline colloidal structures upon the self-organization of ensembles of spherical nanoparticles in model metal lyosols is studied by the Brownian dynamics using realistic potentials of interparticle interaction. The effect of single factors (parameters of dispersed phase particles and characteristics of dispersion medium), as well as their set and arbitrary combinations on the rate of crystallization of sols and regularities of this process are analyzed.

Regularities of the self-organization of ensembles of nanoparticles into crystalline structures in metal lyosols are studied by the Brownian dynamics. Van der Waals, elastic, and electrostatic interparticle interactions, as well as the action of dissipative and fluctuation forces are taken into account in the model. Pair interaction potentials for the polydisperse ensembles of particles are analyzed and the correlations between the pattern of potential curves and the type of formed structures (from crystalline to fractal) are revealed. The effect of interparticle tangential friction on the degree of ordering of formed structures is studied. It is demonstrated that this factor can determine the degree of ordering of nanoparticle aggregates. An essentially new approach to describing elastic interactions of nanoparticles of polymer-containing sols is implemented.

Regularities of the self-organization of bimodal ensembles of nanoparticles into crystalline structures in metal lyosols are studied by the Brownian dynamics method. Differences in the thicknesses of adsorption layers, van der Waals, elastic, and electrostatic interactions, and random and dissipative forces, as well as variations in interparticle electrostatic interactions due to electron tunneling are taken into account in the model. Pair potentials for polydisperse ensembles of particles are analyzed and the correlation between the pattern of potential curves and the type of forming structures is revealed. The possibility of the selective coagulation of particles with different sizes by virtue of dissimilar charging at the moment of their approach is demonstrated. The kinetics of this process is investigated. Specific features of the crystallization of bimodal sols are discussed using real gold organosols as examples.

Experimental data testifying in favor of the correlation between electrodynamic characteristics of fractal aggregates and the structure of the local environment of particles are discussed. One of the possible variants of the control of local structure of disordered silver nanoparticle aggregates placed into a polymer matrix via a significant decrease in its volume is proposed and realized. An indirect method for the detection of the variations in the local structure with the use of plasmon absorption spectra is proposed and substantiated. The evolution of local anisotropy of the environment of the particles of loose aggregates during their compaction is studied. Differences in the absorption spectra of silver nanoaggregates in hydrosols with various concentrations of water-soluble polymer that determine the properties of the local structure of aggregates are discussed, these differences being manifested upon the formation of fragments with quasi-ordered arrangement of particles and in the absence of such fragments.

It is shown that the anisotropy of the environment of metal nanoparticles with plasmon absorption in fractal aggregates is the most important and universal characteristic underlying their unique electrodynamic properties. It is noted that it is this morphological feature, but not the fractal distribution of particles in aggregates as such, that plays the dominant role in the manifestation of the enhancement of a local field. In this case, fractal aggregates possess the ability to enhance local electromagnetic fields only owing to their inherent local anisotropy; macroscopic characteristics of aggregates do not markedly influence their electrodynamic interactions with the external field. The quantitative characteristic of local anisotropy is introduced. Statistical correlation between the factor of local anisotropy and fractal dimension D of aggregates is established within the range 1.6 2.5 corresponding to aggregates with close-packed particles where the factor of local anisotropy tends toward zero. Strong correlation in the spatial arrangement of particles with the largest local anisotropy of the environment in aggregates and the strength of the local electromagnetic field is established using aggregates of silver nanoparticles as an example for the spectrum in the visible range; a polarization dependence of this correlation is revealed. It is noted that parameters of local anisotropy can be used to determine the degree of imperfection of colloidal crystals via optical methods.

A three-dimensional continuum model of the generation of aggregates of spherical particles is developed that allows us to reproduce natural conditions of structure formation in real disperse systems with an arbitrary viscosity of a dispersion medium. The exchange between translational and rotational degrees of freedom for aggregates, subaggregates, and single particles at an arbitrary interparticle interaction potential, as well as at the preset functions of the distribution over particle sizes and thicknesses of the adsorption layer, is taken into account in the model. The interaction potential of the particles includes electrostatic (among them, screened), elastic, and van der Waals interactions and allows for the effect of external electric, magnetic, and gravitational fields. Structural and statistical characteristics of aggregates formed at different stages of particle coagulation are studied, and the quasi-ordering of single subaggregates in the elastic adsorption layer of particles is revealed. The model can be applied to the study of optical absorption by large aggregates of nanoparticles with natural structure and the kinetics of sol aggregation as functions of the properties of the adsorption layer of particles and the action of external physical factors.

The method of molecular dynamics is used to study behavior of a ultracold non-ideal ion-electron Be plasma in a uniform magnetic field. Our simulations yield an estimate for the rate of electron-ion collisions which is non-monotonicallydependent on the magnetic field magnitude. Also they explicitly show that there are two types of diffusion: classical one, corresponding to Brownian motion of particles, and Bohm diffusion when the trajectory of particles (guiding centers) includes substantial lengths of drift motion., Comment: 7 pages; 6 figures

Alexander E. Ershov,1,2 Ivan L. Isaev,1 Polina N. Semina,1 Vadim A. Markel,3 and Sergei V. Karpov1,2 1L. V. Kirenskiy Institute of Physics, Russian Academy of Sciences, Kransoyarsk, 660036, Russian Federation 2Siberian Federal University, Krasnoyarsk, 660041, Russian Federation 3Department of Radiology, Department of Bioengineering, and the Graduate Group in Applied Mathematics and Computational Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA (Received 2 June 2011; revised manuscript received 23 December 2011; published 12 January 2012)

Laser cooling and crystallization of electron-ion plasma is studied using the Brownian dynamics simulation technique and taking into consideration the interaction of ions with the electron subsystem. It has been shown that the nonlinear dependence of laser friction force on the velocity of ions has to be taken into account in order to simulate in an adequate manner the cooling dynamics and obtain a correct estimate for minimum temperatures. It has been found that times required for formation of an ordered ionic structure can be much longer than the typical plasma cooling time.

We present an experimental spectroscopic study of large random colloidal aggregates of silver nanoparticles undergoing local restructuring. We argue that such well-known phenomena as strong fluctuation of local electromagnetic fields, appearance of "hot spots" and enhancement of nonlinear optical responses depend on the local structure on the scales of several nanosphere diameters, rather that the large-scale fractal geometry of the sample., 3.5 pages, submitted to J. Chem. Phys

We have shown within the quasistatic approximation that the giant fluctuations of local electromagnetic field in random fractal aggregates of silver nanospheres are strongly correlated with a local anisotropy factor S which is defined in this paper. The latter is a purely geometrical parameter which characterizes the deviation of local environment of a given nanosphere in an aggregate from spherical symmetry. Therefore, it is possible to predict the sites with anomalously large local fields in an aggregate without explicitly solving the electromagnetic problem. We have also demonstrated that the average (over nanospheres) value of S does not depend noticeably on the fractal dimension D, except when D approaches the trivial limit D=3. In this case, as one can expect, the average local environment becomes spherically symmetrical and S approaches zero. This corresponds to the well-known fact that in trivial aggregates fluctuations of local electromagnetic fields are much weaker than in fractal aggregates. Thus, we find that, within the quasistatics, the large-scale geometry does not have a significant impact on local electromagnetic responses in nanoaggregates in a wide range of fractal dimensions. However, this prediction is expected to be not correct in aggregates which are sufficiently large for the intermediate- and radiation-zone interaction of individual nanospheres to become important., 9 pages 9 figures. No revisions from previous version; only figure layout is changed

We calculate the quasistatic electromagnetic density of states for aggregates of touching spheres, in particular, linear chains and computer-generated random fractal aggregates. Multipole moments with orders of up to $L=64$ are taken into account for random aggregates with the number of particles of up to $N=100$ and up to $L=8000$ for linear chains. Extensive comparisons with the dipole approximation and geometrical cluster renormalization method are performed. Extinction spectra are calculated for several metals and black carbon. Long wavelength electromagnetic properties of fractal aggregates are considered in details.