Controlled killing of human cervical cancer cells by combined action of blue light and C-doped TiO2 nanoparticles.

In this study, C-doped TiO2 nanoparticles (C-TiO2) were prepared and tested as a photosensitizer for visible-light-driven photodynamic therapy against cervical cancer cells (HeLa). X-ray diffraction and Transmission Electron Microscopy confirmed the anatase form of nanoparticles, spherical shape, and size distribution from 5 to 15 nm. Ultraviolet-visible light spectroscopy showed that C doping of TiO2 enhances the optical absorption in the visible light range caused by a bandgap narrowing. The photo-cytotoxic activity of C-TiO2 was investigated in vitro against HeLa cells. The lack of dark cytotoxicity indicates good biocompatibility of C-TiO2. In contrast, a combination with blue light significantly reduced the survival of HeLa cells: illumination only decreased cell viability by 30% (15 min of illumination, 120 µW power), and 60% when HeLa cells were preincubated with C-TiO2. We have also confirmed blue light-induced C-TiO2-catalyzed generation of reactive oxygen species in vitro and intracellularly. Oxidative stress triggered by C-TiO2/blue light was the leading cause of HeLa cell death. Fluorescent labeling of treated HeLa cells showed distinct morphological changes after the C-TiO2/blue light treatment. Unlike blue light illumination, which caused the appearance of large necrotic cells with deformed nuclei, cytoplasm swelling, and membrane blebbing, a combination of C-TiO2/blue light leads to controlled cell death, thus providing a better outcome of local anticancer therapy.

Synergistic Enhancement of Targeted Wound Healing by Near-Infrared Photodynamic Therapy and Silver Metal-Organic Frameworks Combined with S- or N-Doped Carbon Dots.

The literature data emphasize that nanoparticles might improve the beneficial effects of near-infrared light (NIR) on wound healing. This study investigates the mechanisms of the synergistic wound healing potential of NIR light and silver metal-organic frameworks combined with nitrogen- and sulfur-doped carbon dots (AgMOFsN-CDs and AgMOFsS-CDs, respectively), which was conducted by testing the fibroblasts viability, scratch assays, biochemical analysis, and synchrotron-based Fourier transform infrared (SR-FTIR) cell spectroscopy and imaging. Our findings reveal that the combined treatment of AgMOFsN-CDs and NIR light significantly increases cell viability to nearly 150% and promotes cell proliferation, with reduced interleukin-1 levels, suggesting an anti-inflammatory response. SR-FTIR spectroscopy shows this combined treatment results in unique protein alterations, including increased α-helix structures and reduced cross-ß. Additionally, protein synthesis was enhanced upon the combined treatment. The likely mechanism behind the observed changes is the charge-specific interaction of N-CDs from the AgMOFsN-CDs with proteins, enhanced by NIR light due to the nanocomposite's optical characteristics. Remarkably, the complete wound closure in the in vitro scratch assay was achieved exclusively with the combined NIR and AgMOFsN-CDs treatment, demonstrating the promising application of combined AgMOFsN-CDs with NIR light photodynamic therapy in regenerative nanomedicine and tissue engineering.

Lipid Status of A2780 Ovarian Cancer Cells after Treatment with Ruthenium Complex Modified with Carbon Dot Nanocarriers: A Multimodal SR-FTIR Spectroscopy and MALDI TOF Mass Spectrometry Study.

In the last decade, targeting membrane lipids in cancer cells has been a promising approach that deserves attention in the field of anticancer drug development. To get a comprehensive understanding of the effect of the drug [Ru(η5-Cp)(PPh3)2CN] (RuCN) on cell lipidic components, we combine complementary analytical approaches, matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI TOF MS) and synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectroscopy. Techniques are used for screening the effect of potential metallodrug, RuCN, without and with drug carriers (carbon dots (CDs) and nitrogen-doped carbon dots (N-CDs)) on the lipids of the human ovarian cancer cell line A2780. MALDI TOF MS results revealed that the lysis of ovarian cancer membrane lipids is promoted by RuCN and not by drug carriers (CDs and N-CDs). Furthermore, SR-FTIR results strongly suggested that the phospholipids of cancer cells undergo oxidative stress after the treatment with RuCN that was accompanied by the disordering of the fatty acid chains. On the other hand, using (N-)CDs as RuCN nanocarriers prevented the oxidative stress caused by RuCN but did not prevent the disordering of the fatty acid chain packing. Finally, we demonstrated that RuCN and RuCN/(N-)CDs alter the hydration of the membrane surface in the membrane-water interface region.

Biochemical changes in cancer cells induced by photoactive nanosystem based on carbon dots loaded with Ru-complex.

Carbon dots (CDs) and N-carbon dots (N-CDs) loaded with Ru-complex (CDs@RuCN, N-CDs@RuCN, respectively) were investigated as media imposing biochemical changes induced by UV illumination of ovarian cancer, A2780, and osteosarcoma, CAL72, cells. Synchrotron radiation-based Fourier Transform Infrared Spectroscopy was performed, and the spectra were subjected to a Principal Component Analysis. The CDs@RuCN and N-CDs@RuCN effects on cancer cells were analyzed by the theoretical modelling of the stability of the composite systems and a protein database search. Moreover, a detailed evaluation of surface and optical properties of CDs@RuCN and N-CDs@RuCN was carried out. Results demonstrated selective action of the CDs@RuCN and N-CDs@RuCN-based photodynamic therapy, with N-CDs@RuCN being the most active in inducing changes in A2780 and CDs@RuCN in CAL72 cells. We assume that different surface charges of nanoparticles led to direct interactions of N-CDs@RuCN with a Wnt signalling pathway in A2780 and those of CDs@RuCN with PI3-K/Akt in CAL72 cells and that further biochemical changes occurred upon light illumination.

Mobility of high-power solitons in saturable nonlinear photonic lattices.

We theoretically study the properties of one-dimensional nonlinear saturable photonic lattices exhibiting multiple mobility windows for stationary solutions. The effective energy barrier decreases to a minimum in those power regions where a new intermediate stationary solution appears. As an application, we investigate the dynamics of high-power Gaussian-like beams finding several regions where the light transport is enhanced.

Functional titanium dioxide nanoparticle conjugated with phthalocyanine and folic acid as a promising photosensitizer for targeted photodynamic therapy in vitro and in vivo.

Photodynamic therapy (PDT) is a promising cancer treatment that can be implemented using various agents. The conventional photosensitizer Al (III) phthalocyanine chloride tetrasulfonic acid (Pc) has limitations of selectivity in tumor targeting, low affinity to cancer cells, and low two-photon absorption. This study presents a novel photosensitizer FA-TiO2-Pc, which has the TiO2 nanoparticle conjugated with a tumor targeting agent of folic acid (FA), and Pc. FA-TiO2-Pc possessed high targeted photodynamic therapeutic activity and excellent biocompatibility. This promising photosensitizer showed high therapeutic drug efficiency in vitro at a low concentration dose and short incubation time under one-photon excitation (OPE). In vivo, when treated with a low dose of FA-TiO2-Pc and low light irradiation, the tumor growth was depressed in mice bearing HeLa xenograft tumors with minimal side effects. In addition, the two-photon absorption of FA-TiO2-Pc was also enhanced compared to Pc, proving that FA-TiO2-Pc system has a great potential to be used for the therapy of the folate receptor positive cancer cells in both OPE-PDT and two-photon excitation (TPE)-PDT agents.

Observation of linear and nonlinear strongly localized modes at phase-slip defects in one-dimensional photonic lattices.

We investigate light localization at a single phase-slip defect in one-dimensional photonic lattices, both numerically and experimentally. We demonstrate the existence of various robust linear and nonlinear localized modes in lithium niobate waveguide arrays exhibiting saturable defocusing nonlinearity.

Localized modes in a two-dimensional lattice with a pluslike geometry.

We investigate analytically and numerically the existence and dynamical stability of different localized modes in a two-dimensional photonic lattice comprising a square plaquette inscribed in the dodecagon lattices. The eigenvalue spectrum of the underlying linear lattice is characterized by a net formed of one flat band and four dispersive bands. By tailoring the intersite coupling coefficient ratio, opening of gaps between two pairs of neighboring dispersive bands can be induced, while the fully degenerate flat band characterized by compact eigenmodes stays nested between two inner dispersive bands. The nonlinearity destabilizes the compact modes and gives rise to unique families of localized modes in the newly opened gaps, as well as in the semi-infinite gaps. The governing mechanism of mode localization in that case is the light energy self-trapping effect. We have shown the stability of a few families of nonlinear modes in gaps. The suggested lattice model may serve for probing various artificial flat-band systems such as ultracold atoms in optical lattices, periodic electronic networks, and polariton condensates.

SR-FTIR spectro-microscopic interaction study of biochemical changes in HeLa cells induced by Levan-C60, Pullulan-C60, and their cholesterol-derivatives.

Objects of the present study are improved fullerene C60 drug carrier properties trough encapsulation by microbial polysaccharides, levan (LEV), pullulan (PUL), and their hydrophobized cholesterol-derivatives (CHL and CHP), that show better interaction with cancer cells. The zeta potential, polydispersity index, and the diameter of particles were determined, and their cytotoxicity against three cancer cell lines were tested. Biochemical changes in HeLa cells are analyzed by synchrotron radiation (SR) FTIR spectro-microscopy combined with the principal component analysis (PCA). The most significant changes occur in HeLa cells treated with LEV-C60 and correspond to the changes in the protein region, i.e. Amide I band, and the changes in the structure of lipid bodies and membrane fluidity are evident. The highest cytotoxicity was also induced by LEV-C60. In HeLa cells, cytotoxicity could not be strictly associated with biochemical changes in lipids, proteins and nucleic acids, but these findings are significant contribution to the study of the mechanism of interaction of C60-based nanoparticles with cellular biomolecules. In conclusion, LEV, PUL, CHL, and CHP enhanced fullerene C60 potential to be used as target drug delivery system with the ability to induce specific intracellular changes in HeLa cancer cells.

Reconfigurable optical channel waveguides in lithium niobate crystals produced by combination of low-dose O3+ ion implantation and selective white light illumination.

We report on a new method to form reconfigurable channel waveguides in lithium niobate crystals, based on a combination of low-dose O(3+) ion implantation and selective white light illumination. The fabricated structures show low loss as well as rather high resistivity against optical erasure with red or infrared light, while at the same time reconfiguration of the structures remains possible using homogeneous white light illumination. The transmission properties of the channel waveguide modes can be well simulated numerically by the beam propagation method, which allows for the fabrication of tailored optical interconnections.

Dynamics of dark breathers in lattices with saturable nonlinearity.

The problems of the existence, stability, and transversal motion of the discrete dark localized modes in the lattices with saturable nonlinearity are investigated analytically and numerically. The stability analysis shows existence of regions of the parametric space with eigenvalue spectrum branches with non-zeroth real part, which indicates possibility for the propagation of stable on-site and inter-site dark localized modes. The analysis based on the conserved system quantities reveals the existence of regions with a vanishing Peierls-Nabarro barrier which allows transverse motion of the dark breathers. Propagation of the stable on-site and inter-site dark breathers and their free transversal motion are observed numerically.

Higher-band modulational instability in photonic lattices.

Propagation of extended Floquet-Bloch modes in the first three bands of a one-dimensional photonic lattice possessing a self-defocusing saturable nonlinearity is studied experimentally and numerically on the example of waveguide arrays in lithium niobate. Discrete modulation instability is observed in all bands in the region of anomalous diffraction, whereas modes propagate stable in the normal diffraction regime.

Dark and bright blocker soliton interaction in defocusing waveguide arrays.

We experimentally demonstrate the interaction of an optical probe beam with both bright and dark blocker solitons formed with low optical light power in a saturable defocusing waveguide array in photorefractive lithium niobate. A phase insensitive interaction of the beams is achieved by means of counterpropagating light waves. Partial and full reflection (blocking) of the probe beam on the positive or negative light-induced defect is obtained, respectively, in good agreement with numerical simulations.

Formation and light guiding properties of dark solitons in one-dimensional waveguide arrays.

We report on the formation of dark discrete solitons in a nonlinear periodic system consisting of evanescently coupled channel waveguides in defocusing lithium niobate. Localized nonlinear dark modes displaying a phase jump in the center that is located either on-channel (mode A) or in-between channels (mode B) are formed, which is to our knowledge the first experimental observation of mode B. By numerical simulations we find that the saturable nature of the nonlinearity is responsible for the improved stability of mode B. The ability of the induced refractive index structures to guide light of a low-power probe beam is demonstrated.

Beam interactions in one-dimensional saturable waveguide arrays.

The interaction between two parallel beams in one-dimensional discrete saturable systems has been investigated using lithium niobate nonlinear waveguide arrays. When the beams are separated by one channel and in phase it is possible to observe soliton fusion at low power levels. This result is confirmed numerically. By increasing the power, solitonlike propagation of weakly coupled beams occurs. When the beams are out-of-phase the most interesting numerically obtained result is the existence of oscillations which resemble the recently discovered Tamm oscillations.

Discrete diffraction and spatial gap solitons in photovoltaic LiNbO3 waveguide arrays.

We investigate, experimentally and theoretically, light propagation in one-dimensional waveguide arrays exhibiting a saturable self-defocusing nonlinearity. We demonstrate low-intensity "discrete diffraction", and the high-intensity formation of spatial gap solitons arising from the first band of the transmission spectrum. The waveguide arrays are fabricated by titanium in-diffusion in a photorefractive copper-doped lithium niobate crystal, and the optical nonlinearity arises from the bulk photovoltaic effect.

One-dimensional bright discrete solitons in media with saturable nonlinearity.

A problem of pulse propagation in a homogeneous nonlinear waveguide array with saturable nonlinearity is studied. The corresponding model equation is the discretized Vinetskii-Kukhtarev equation with neglected influence of diffusion of charge carriers. For periodic boundary conditions, exact homogeneous and oscillating stationary solutions are found. A wide instability region of the homogeneous, array-independent solution is identified. An approximate analytical solution for the bright one-dimensional discrete soliton where the energy is concentrated mainly in a few waveguides is obtained. The soliton stability is investigated both analytically and numerically and a cascade nature of the saturation mechanism is revealed.

Stability of one-dimensional array solitons.

The array soliton stability in the discrete nonlinear Schrödinger equation with dispersion for periodic boundary conditions is studied. The linear growth rate dependence on the discrete wave number and soliton amplitude is calculated from the linearized eigenvalue problem using the variational method. In addition, the eigenvalue problem is solved numerically by shooting method and a good agreement with the analytical results is found. It is proved numerically that the results for the instability threshold for the circular array coincides with the quasicollapse threshold for the case of open arrays with initial pulses in a form of array solitons.

Interaction of counterpropagating discrete solitons in a nonlinear one-dimensional waveguide array.

We experimentally investigate the interaction of counterpropagating discrete solitons in a one-dimensional waveguide array in photorefractive lithium niobate. While for low input powers only weak interaction and formation of counterpropagating vector solitons are observed, for higher input powers a growing instability results in discrete lateral shifting of the formed discrete solitons. Numerical modeling shows the existence of three different regimes: stable propagation of vector solitons at low power, instability for intermediate power levels leading to discrete shifting of the two discrete solitons, and an irregular temporal dynamic behavior of the two beams for high input power.

Observation of modulational instability in discrete media with self-defocusing nonlinearity.

We report what we believe is the first observation of modulation instability in the anomalous-diffraction regions of a photonic lattice. The experiments were carried out in a 1D waveguide array fabricated in a lithium niobate crystal displaying the photovoltaic self-defocusing nonlinearity, and our results are confirmed numerically by simulating the nonlinear beam propagation.