Gold nanoparticles are intensively studied in biomedicine. Assessment of their biocompatibility is highly important. Currently there is lack of evidence, concerning nanotoxicity of ultrasmall gold nanoparticles < 5 nm. Existing data are rather contradictory. The aim of that study was to evaluate the toxicity of 2 nm colloidal gold, using microalga Dunaliella salina. Cellular barriers of that microalga are very similar to animal cells so it might be considered as a valuable model for nanotoxicity testing. Chlorophyll content as a test–function was used. Spectrophotometric method for chlorophyll determination in vivo in suspensions of D.salina cultures was applied. Calculated EC50 48h value of ionic gold was 25.8 ± 0.3 mg Au/L. EC50 value of phosphine-stabilized gold nanoclusters was 32.2 ±1.1 mg Au/L. It was not possible to calculate EC50 for 15 nm citrate gold nanoparticles, as they were non-toxic at all concentrations tested. These results are confirmed by fluorescent –microscopic monitoring of the same probes. It was shown that 10-fold growth of phosphine-stabilized gold nanoparticles (from 2.3 ± 0.9 nm to 21.1 ± 7.5 nm) led to 7-fold decrease of their toxicity.
The application of gold nanoparticles (GNPs) for laser-induced cell transfection has been studied intensively during the past decade as efficient and gentle alternative to well-established molecule delivery methods like lipid-based transfection or electroporation. The method is based on temporal increase of membrane permeability induced by laser irradiation of GNPs attached to cell membranes. Although this approach is attractive due to high throughput and easy usability, it is not free from serious drawbacks related to random adsorption of GNPs during preincubation of cells with GNPs. This stage can affect the optoporation results because of potential nanoparticle toxicity, thus leading to decreased delivery efficiency and to low reproducibility of independent optoporation runs. Herein, we suggest a novel GNP-mediated laser transfection technique based on immobilized gold nanostars (GNSs) that are adsorbed on microplate wells and act as a plasmonic surface. The HeLa cells are grown directly on the monolayer of immobilized GNSs followed by CW NIR laser irradiation. We used the propidium iodide (PI) as a model transfecting agent to monitor simultaneously the delivery of PI into HeLa cells and their viability. These proof-of-the-concept experiments demonstrated enhanced penetration of PI into irradiated cells as compared to untreated ones.
In the present work the effectiveness of antioxidants quercetine (a pure chemical) and Gratiola officinalis extract, which is obtained by a new method of extraction from plant material, is investigated on the model of photodynamic haemolysis that is a rather convenient method to monitor the rate of cell membranes oxidative destruction. The effect of these antioxidants on the rate of photodynamic haemolysis is considered as a measure of membranoprotective efficiency.
We synthesized and characterized gold nanostars and their silica-coated derivatives with 7- to 50-nm shell thicknesses as contrast agents for optical imaging. The scattering and absorption coefficients of the nanoparticles (NPs) were estimated by means of collimated transmittance and diffuse reflectance/transmittance analyses. The contrasting properties of the nanostructures were studied in optical coherence tomography glass capillary imaging. The silica-coated nanostars with the thickest shell have higher scattering ability in comparison with bare nanostars. Viability assays confirmed weak in vitro toxicity of nanostructures at up to ∼200-μg/mL concentrations. We showed real-time visualization of nanostars in both agarose and cultured cells by analyzing the backscattering signal using a conventional laser confocal microscope. The signal intensity detected from the silica-coated NPs was almost 1.5 times higher in comparison with bare nanostars. To the best of our knowledge, this is the first time that conventional laser confocal microscopy was applied in combined scattering and transmitted light modes to detect the backscattered signal of gold nanostars, which is useful for direct monitoring of the uptake, translocation, and accumulation of NPs in living cells.
In this paper, plasmon-resonant nanostructures, such as gold nanostars and their silica-coated composites, were used for enhancement of OCT image contrast of water flows in glass capillaries. The contrasting properties of the synthesized nanostars and nanocomposites with silica shell thickness of about 5 nm and 50 nm were compared in the framework of capillary stasis model. The most intensive signal was detected from the nanocomposites with the thickest silica shell. The nanocomposites were characterized by optical spectroscopy and electron microscopy. Nontoxicity of nanostars and nanocomposites up to ~ 3 mg/mL concentration was showed by MTT assay suggesting practical applications of the nanostructures for bioimaging.
In this work, two types of nanocomposites, silica-coated nano-sea-urchins and silica-coated gold nanostars, were
fabricated. CTAB-coated nano-sea-urchins with an average size of about 100 nm demonstrate an absorption peak near
600-700 nm and stability in aqueous suspension. CTAB was exchanged with m-PEG-SH by an intermediate PEG layer.
A layer of silica was synthesized on the nano-sea-urchins surface with thickness of about 20 nm. Nanostars with an
average size of about 60 nm with a number of thin sharp branches were fabricated and functionalized by PVP to improve
their stability. PVP-coated nanostars were used in optical coherence tomography experiments to show their contrasting
properties. After silica-coating, stable and monodispersed nanoparticles with silica shell thickness about 60 nm were
obtained. Nontoxicity of the silica-coated nanostars at least until the concentration of nanoparticles about 400 μg/mL was
showed by fluorescent cell viability assay using propidium iodide. Extinction coefficient of the gold nanostars and
nanocomposites was estimated by a spectrophotometer system in collimated transmission regime.
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