Carefully designed micro-and nanocarriers can provide significant advantages over conventional macroscopic counterparts in biomedical applications. The set of requirements including a high loading capacity, triggered release mechanisms, biocompatibility, and biodegradability should be considered for the successful delivery realization. Porous calcium carbonate (CaCO3) is one of the most promising platforms, which can encompass all the beforehand mentioned requirements. Here, we study both the particles formation and biological applicability of CaCO3. In particular, anisotropic differently shaped CaCO3 particles were synthesized using green sustainable approach based on co-precipitation of calcium chloride and sodium carbonate/bicarbonate at different ratios in the presence of organic additives. The impact of salts concentrations, reaction time, as well as organic additives was systematically researched to achieve controllable and reliable design of CaCO3 particles. It has been demonstrated that the crystallinity (vaterite or calcite phase) of particles depends on the initial salts' concentrations. The loading capacity of prepared CaCO3 particles is determined by their surface properties such as specific surface area, pore size and zetapotential. Differently shaped CaCO3 particles (spheroids, ellipsoids, toroids) were used to evaluate their uptake efficiency on the example of C6 glioma cells. The results show that the ellipsoidal particles possess a higher probability for internalization by cancer cells. All tested particles were also found to have a good biocompatibility. The capability to design physicochemical properties of CaCO3 particles has a significant impact on drug delivery applications, since the particles geometry substantially affects cell behavior (internalization, toxicity) and allows outperforming standard spherical counterparts.

mostly based on fluorescent (FL) agents of high brightness and combines exceptional optical properties with biocompatibility, biodegradability, and precise targeting both in vivo and in vitro. This includes inorganic semiconductor quantum dots, [2] carbon nanodots, [3] organic molecular dyes, [4] and genetically encoded universal FL proteins. [5] Additional specific class of extrinsic FL nanoprobes is amyloidbinding small molecule ligands (thioflavin T, Congo red and more) employed for tracking the kinetics of amyloid fibrils growth. [6] Each of the imaging agents has its inherent mechanism of photon emission, which defines its figures of merit for bioimaging: FL spectral region, quantum yield (QY), and photobleaching. [7,8] For instance, quantum dots and organic dye molecules exhibit FL in the visible range and have very high QY exceeding 90%. However, the organic molecular dyes are limited for long-term bioimaging applications because of photobleaching issues. The biocompatibility is another basic parameter of any biolabels, which is especially critical for some organic dyes and inorganic semiconductor quantum dots, containing heavy metals. Recently found FL carbon nanodots are biocompatible but have a low QY. [9] The green fluorescence protein (GFP) and its homologues are the only molecules, known until today, having biological origin FL and providing unique biocompatibility. These proteins exhibit pronounced FL with QY reaching 90% covering the entire visible spectrum, which makes them unique FL tags [10] among unlimited number of nonfluorescent peptide and protein biomolecules. [1,2,5,7] Alternative composition-insensitive visible FL was recently found in biological and bioinspired nanostructures characterized by specific ordering of biomolecules into antiparallel β-sheets structures. This includes a wide variety of diverse biomolecular compositions, such as amyloidogenic proteins, [11,12] PEGylated peptides, [13,14] nonaromatic biogenic, and synthetic peptides [15] and recently natural silk fibrils. [16] The basic features of these FL nanostructures are similar fibrillar morphology, original β-sheets secondary structure, and identical visible FL optical spectrum. These common structural and optical properties enable to relate all of them to a wide class of thermodynamically stable disease-and nondiseased-related amyloid structures. [17][18][19] Such β-sheet structures and visible FL can also Nanoscale bioimaging is a highly important scientific and technological tool, where fluorescent (FL) proteins, organic molecular dyes, inorganic quantum dots, and lately carbon dots are widely used as light emitting biolabels. In this work, a new class of visible FL bioorganic nanodots, self-assembled from short peptides of different composition and origin, is introduced. It is shown that the electronic energy spectrum of native nonfluorescent peptide nanodots (PNDs) is deeply modified upon thermally mediated refolding of their biological secondary structure from native metastable to stable β-sheet rich structure. This ...

We study modulational instability in nonlinear arrays of subwavelength metallic nanoparticles and analyze numerically nonlinear scenarios of the instability development. We demonstrate that modulational instability can lead to the formation of regular periodic or quasiperiodic modulations of the polarization. We reveal that such nonlinear nanoparticle arrays can support long-lived standing and moving oscillating nonlinear localized modes--plasmon oscillons.

We introduce a novel hybrid metal-dielectric nanoantenna composed of dielectric (crystalline silicon) and metal (silver) nanoparticles. In such a nanoantenna, the phase shift between the dipole moments of the nanoparticles, caused by differences in the polarizabilities, allows for directional light scattering; while the nonlinearity of the metal nanoparticle helps to control the radiation direction. We show that the radiation pattern of this nanoantenna can be switched between the forward and backward directions by varying only the light intensity around the level of 6 MW cm −2 , with a characteristic switching time of 40 fs.

It is interesting to pose the question: How best to design an optomechanical device, with no electronics, optical cavity, or laser gain, that will self-oscillate when pumped in a single pass with only a few mW of single-frequency laser power? One might begin with a mechanically resonant and highly compliant system offering very high optomechanical gain. Such a system, when pumped by single-frequency light, might self-oscillate at its resonant frequency. It is well-known, however, that this will occur only if the group velocity dispersion of the light is high enough so that phonons causing pump-to-Stokes conversion are sufficiently dissimilar to those causing pump-to-anti-Stokes conversion. Recently it was reported that two light-guiding membranes 20 μm wide, ∼500 nm thick and spaced by ∼500 nm, suspended inside a glass fiber capillary, oscillated spontaneously at its mechanical resonant frequency (∼6 MHz) when pumped with only a few mW of single-frequency light. This was surprising, since perfect Raman gain suppression would be expected. In detailed measurements, using an interferometric side-probing technique capable of resolving nanoweb movements as small as 10 pm, we map out the vibrations along the fiber and show that stimulated intermodal scattering to a higher-order optical mode frustrates gain suppression, permitting the structure to self-oscillate. A detailed theoretical analysis confirms this picture. This novel mechanism makes possible the design of single-pass optomechanical oscillators that require only a few mW of optical power, no electronics nor any optical resonator. The design could also be implemented in silicon or any other suitable material.

Recent experiments in the field of strong optomechanical interactions have focused on either structures that are simultaneously optically and mechanically resonant, or photonic crystal fibers pumped by a laser intensity modulated at a mechanical resonant frequency of the glass core. Here, we report continuous-wave (CW) pumped self-oscillations of a fiber nanostructure that is only mechanically resonant. Since the mechanism has close similarities to stimulated Raman scattering by molecules, it has been named stimulated Raman-like scattering. The structure consists of two submicrometer thick glass membranes (nanowebs), spaced by a few hundred nanometers and supported inside a 12-cm-long capillary fiber. It is driven into oscillation by a CW pump laser at powers as low as a few milliwatts. As the pump power is increased above threshold, a comb of Stokes and anti-Stokes lines is generated, spaced by the oscillator frequency of similar to 6 MHz. An unprecedentedly high Raman-like gain of similar to 4 x 10(6) m(-1) W-1 is inferred after analysis of the experimental data. Resonant frequencies as high as a few hundred megahertz are possible through the use of thicker and less-wide webs, suggesting that the structure can find application in passive mode-locking of fiber lasers, optical frequency metrology, and spectroscopy. (C) 2014 Optical Society of Americ

For centuries mankind has been modifying the optical properties of materials: first, by elaborating the geometry and composition of structures made of materials found in nature, later by structuring the existing materials at a scale smaller than the operating wavelength. Here we suggest an original approach to introduce optical activity in nanostructured materials, by theoretically demonstrating that conventional achiral semiconducting nanocrystals become optically active in the presence of screw dislocations, which can naturally develop during the nanocrystal growth. We show the new properties to emerge due to the dislocation-induced distortion of the crystal lattice and the associated alteration of the nanocrystal’s electronic subsystem, which essentially modifies its interaction with external optical fields. The g-factors of intraband transitions in our nanocrystals are found comparable with dissymmetry factors of chiral plasmonic complexes, and exceeding the typical g-factors of chiral molecules by a factor of 1000. Optically active semiconducting nanocrystals—with chiral properties controllable by the nanocrystal dimensions, morphology, composition and blending ratio—will greatly benefit chemistry, biology and medicine by advancing enantiomeric recognition, sensing and resolution of chiral molecules.

We analyze nonlinear effects in optically driven arrays of nonlinear metallic nanoparticles. We demonstrate that such plasmonic systems are characterized by a bistable response, and they can support the propagation of dissipative switching waves (or plasmonic kinks) connecting the states with different polarization. We study numerically the properties of such plasmonic kinks which are characterized by a subwavelength extent and a tunable velocity.