Marine Polysaccharides Carrageenans Enhance Eryptosis and Alter Lipid Order of Cell Membranes in Erythrocytes.

Aim In the current study, hemocompatibility of three major commercially available types of carrageenans (ι, κ and λ) was investigated focusing on eryptosis. MATERIALS AND METHODS: Carrageenans of ι-, κ- and λ-types were incubated with washed erythrocytes (hematocrit 0.4%) at 0-1-5-10 g/L for either 24 h or 48 h. Incubation was followed by flow cytometry-based quantitative analysis of eryptosis parameters, including cell volume, cell membrane scrambling and reactive oxygen species (ROS) production, lipid peroxidation markers and confocal microscopy-based evaluation of intracellular Ca2+ levels, assessment of lipid order in cell membranes and the glutathione antioxidant system. Confocal microscopy was used to assess carrageenan cellular internalization using rhodamine B isothiocyanate-conjugated carrageenans. RESULTS: All three types of carrageenans were found to trigger eryptosis. Pro-eryptotic properties were type-dependent and λ-carrageenan had the strongest impact inducing phosphatidylserine membrane asymmetry, changes in cell volume, Ca2+ signaling and oxidative stress characterized by ROS overproduction, activation of lipid peroxidation and severe glutathione system depletion. Eryptosis induction by carrageenans does not require their uptake by erythrocytes. Changes in physicochemical properties of cell membrane were also type-dependent. No carrageenan-induced generation of superoxide and hydroxyl radicals was observed in cell-free milieu. CONCLUSIONS: Our findings suggest that ι-, κ- and λ-types trigger eryptosis in a type-dependent manner and indicate that carrageenans can be further investigated as potential eryptosis-regulating therapeutic agents.

Rare-earth orthovanadate nanoparticles trigger Ca2+-dependent eryptosis.

Introduction. Rare-earth orthovanadate nanoparticles (ReVO4:Eu3+, Re = Gd, Y or La) are promising agents for photodynamic therapy of cancer due to their modifiable redox properties. However, their toxicity limits their application.Objective. The aim of this research was to elucidate pro-eryptotic effects of GdVO4:Eu3+and LaVO4:Eu3+nanoparticles with identification of underlying mechanisms of eryptosis induction and to determine their pharmacological potential in eryptosis-related diseases.Methods. Blood samples (n= 9) were incubated for 24 h with 0-10-20-40-80 mg l-1GdVO4:Eu3+or LaVO4:Eu3+nanoparticles, washed and used to prepare erythrocyte suspensions to analyze the cell membrane scrambling (annexin-V-FITC staining), cell shrinkage (forward scatter signaling), reactive oxygen species (ROS) generation through 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) staining and intracellular Ca2+levels via FLUO4 AM staining by flow cytometry. Internalization of europium-enabled luminescent GdVO4:Eu3+and LaVO4:Eu3+nanoparticles was assessed by confocal laser scanning microscopy.Results.Both nanoparticles triggered eryptosis at concentrations of 80 mg l-1. ROS-mediated mechanisms were not involved in rare-earth orthovanadate nanoparticles-induced eryptosis. Elevated cytosolic Ca2+concentrations were revealed even at subtoxic concentrations of nanoparticles. LaVO4:Eu3+nanoparticles increased intracellular calcium levels in a more pronounced way compared with GdVO4:Eu3+nanoparticles. Our data disclose that the small-sized (15 nm) GdVO4:Eu3+nanoparticles were internalized after a 24 h incubation, while the large-sized (∼30 nm) LaVO4:Eu3+nanoparticles were localized preferentially around erythrocytes.Conclusions.Both internalized GdVO4:Eu3+and non-internalized LaVO4:Eu3+nanoparticles (80 mg l-1) promote eryptosis of erythrocytes after a 24 h exposurein vitrovia Ca2+signaling without involvement of oxidative stress. Eryptosis is a promising model for assessing nanotoxicity.

Assessing the Cytotoxicity of TiO2-x Nanoparticles with a Different Ti3+(Ti2+)/Ti4+ Ratio.

Titanium dioxide (TiO2) nanoparticles are promising biomedical agents characterized by good biocompatibility. In this study, we explored the cytotoxicity of TiO2-x nanoparticles with a different Ti3+(Ti2+)/Ti4+ ratio and analyzed the efficiency of eryptosis indices as a tool in nanotoxicology. Two types of TiO2-x nanoparticles (NPs) were synthesized by the hydrolysis of titanium alkoxide varying the nitric acid content in the hydrolysis mixture. Transmission electron microscopy (TEM) images show that 1-TiO2-x and 2-TiO2-x NPs are 5 nm in size, whereas X-ray photoelectron spectroscopy (XPS) reveals different Ti3+ (Ti2+)/Ti4+ ratios in the crystal lattices of synthesized NPs. 1-TiO2-x nanoparticles contained 54% Ti4+, 38% Ti3+, and 8% Ti2+, while the relative amount of Ti4+ and Ti3+ in the crystal lattice of 2-TiO2-x nanoparticles was 63% and 37%, respectively. Cell viability and cell motility induced by TiO2-x nanoparticles were investigated on primary fibroblast cultures. Eryptosis modulation by the nanoparticles along with cell death mechanisms was studied on rat erythrocytes. We report that both TiO2-x nanoparticles do not decrease the viability of fibroblasts simultaneously stimulating cell migration. Data from in vitro studies on erythrocytes indicate that TiO2-x nanoparticles trigger eryptosis via ROS- (1-TiO2-x) and Ca2+-mediated mechanisms (both TiO2-x nanoparticles) suggesting that evaluation of eryptosis parameters is a more sensitive nanotoxicological approach for TiO2-x nanoparticles than cultured fibroblast assays. TiO2-x nanoparticles are characterized by low toxicity against fibroblasts, but they induce eryptosis, which is shown to be a promising tool for nanotoxicity screening. The Ti3+ (Ti2+)/Ti4+ ratio at least partly determines the cytotoxicity mechanisms for TiO2-x nanoparticles.

Antimicrobial Effects of Nanostructured Rare-Earth-Based Orthovanadates.

The search for novel antimicrobial agents is of huge importance. Nanomaterials can come to the rescue in this case. The aim of this study was to assess the cytotoxicity and antimicrobial effects of rare-earth-based orthovanadate nanoparticles. The cytotoxicity against host cells and antimicrobial activity of LaVO4:Eu3+ and GdVO4:Eu3+ nanoparticles were analyzed. Effects of nanomaterials on fibroblasts were assessed by MTT, neutral red uptake and scratch assays. The antimicrobial effects were evaluated by the micro-dilution method estimating the minimum inhibitory concentration (MIC) of nanoparticles against various strains of microorganisms, DNA cleavage and biofilm inhibition. GdVO4:Eu3+ nanoparticles were found to be less toxic against eukaryotic cells compared with LaVO4:Eu3+. Both nanoparticles exhibited antimicrobial activity and the highest MIC values were 64 mg/L for E. hirae, E. faecalis and S. aureus shown by GdVO4:Eu3+ nanoparticles. Nanoparticles demonstrated good DNA cleavage activity and induction of double-strand breaks in supercoiled plasmid DNA even at the lowest concentrations used. Both nanoparticles showed the biofilm inhibition activity against S. aureus at 500 mg/L and reduced the microbial cell viability. Taken the results of host toxicity and antimicrobial activity studies, it can be assumed that GdVO4:Eu3+ nanoparticles are more promising antibacterial agents compared with LaVO4:Eu3+ nanoparticles.

UV Light-Activated GdYVO4:Eu3+ Nanoparticles Induce Reactive Oxygen Species Generation in Leukocytes Without Affecting Erythrocytes In Vitro.

Nanoparticles (NPs) have been reported to be promising enhancement agents for radiation therapy. The aim of the study was to assess the cytotoxicity of UV non-treated and UV pretreated GdYVO4:Eu3+ nanoparticles against erythrocytes and leukocytes by detecting eryptosis and reactive oxygen species (ROS) generation. Levels of intracellular ROS in erythrocytes and leukocytes using a ROS-sensitive dye 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), as well as eryptosis rate utilizing annexin V staining, following direct exposure to UV-activated and nonactivated NPs were detected by flow cytometry. Blood cells were collected from 9 intact WAG rats. Neither the UV light-untreated GdYVO4:Eu3+ NPs nor the treated ones promoted eryptosis and ROS generation in erythrocytes. Low concentrations of UV light-untreated NPs did not induce oxidative stress in leukocytes, evidenced by unaffected intracellular ROS levels. UV light treatment grants prooxidant properties to NPs, confirmed by NP-induced ROS overproduction in leukocytes. High concentrations of both UV light-treated and untreated NPs altered the redox state of leukocytes. UV light treatment imparts prooxidant properties to GdYVO4:Eu3+ NPs, making them promising radiosensitizing agents in cancer radiation therapy.

Experimental confirmation of antimicrobial effects of GdYVO4:Eu3+ nanoparticles.

Nanotechnology can be applied to design antibacterial agents to combat antibiotic resistance. The aim of the present study was to assess the antimicrobial effects and cytotoxicity of GdYVO4:Eu3+ nanoparticles (NPs). Biofilm inhibition activity, antimicrobial activity, bacterial viability inhibition and DNA cleavage activity of GdYVO4:Eu3+ NPs were studied. In addition, the impact of GdYVO4:Eu3+ NPs on the mitochondrial membrane potential (ΔΨM) of host immune cells and, hence, their apoptosis was analyzed by JC-1 staining using flow cytometry. GdYVO4:Eu3+ NPs demonstrated good antimicrobial, cell viability inhibition and DNA cleavage activities. In addition, GdYVO4:Eu3+ NPs showed good biofilm inhibition activity against S. aureus and P. aeruginosa and inhibition percentages were 89.15% and 79.54%, respectively. However, GdYVO4:Eu3+ NPs promoted mitochondrial depolarization and apoptosis of leukocytes at high concentrations. GdYVO4:Eu3+ nanoparticles are promising antibacterial agents. However, more efforts should be exerted to ensure their safety.

Insight into the mechanism of the photoluminescence of carbon nanoparticles derived from cryogenic studies.

The unexpected discovery of the photoluminescence of carbon nanoparticles attracted the attention of many researchers and resulted in their use in a variety of applications. However, the origin of their emission is still obscure, and the majority of the discussions on the subject focus on their molecular and/or excitonic emissive states. We performed cryogenic studies down to 10 K and did not observe any signatures of suppressed molecular relaxation - the spectra remained broad, showing large unaltered Stokes shifts and temperature-independent emission intensities and lifetimes below 80 K with a weak dependence above this value. We demonstrated that the most general features of carbon nanoparticles, the very large Stokes shifts and considerable differences between the absorption and excitation spectra, are the result of the formation of a dynamic defect, the self-trapped Frenkel exciton. It looks like the distorted domain of the H-aggregate due to the exciton-lattice interaction and the local overheating caused by the exciton relaxation. In addition, at low temperatures the long-lifetime spectral component was found and was attributed to phosphorescence. The obtained results strongly support the excitonic nature of the fluorescence of nanocarbon materials.

Reactive oxygen species generation in aqueous solutions containing GdVO4:Eu3+ nanoparticles and their complexes with methylene blue.

It this letter, we report the study of free radicals and reactive oxygen species (ROS) generation in water solutions containing gadolinium orthovanadate GdVO4:Eu3+ nanoparticles (VNPs) and their complexes with methylene blue (MB) photosensitizer. The catalytic activity was studied under UV-Vis and X-ray irradiation by three methods (conjugated dienes test, OH· radical, and singlet oxygen detection). It has been shown that the VNPs-MB complexes reveal high efficiency of ROS generation under UV-Vis irradiation associated with both high efficiency of OH· radicals generation by VNPs and singlet oxygen generation by MB due to nonradiative excitation energy transfer from VNPs to MB molecules. Contrary to that under X-ray irradiation, the strong OH . radicals scavenging by VNPs has been observed.

Oscillations of Cerium Oxidation State Driven by Oxygen Diffusion in Colloidal Nanoceria (CeO2 - x ).

The redox performance of CeO2 - x nanocrystals (nanoceria) is always accompanied by the switching of cerium oxidation state between Ce3+ and Ce4+. We monitored Ce3+ â†’ Ce4+ oxidation of nanoceria stimulated by oxidant in aqueous colloidal solutions controlling the luminescence of Ce3+ ions located at different distances from nanoceria surface. The observed Ce3+ luminescence changes indicate that Ce3+ â†’ Ce4+ reaction develops inside nanoceria being triggered by the diffusing oxygen originated from the water splitting on oxidized nanoceria surface. We present the first observation of the pronounced oscillations of Ce3+ luminescence intensity arising from Ce3+ â†” Ce4+ reversible switching. This threshold effect is to be driven by uptaking and releasing oxygen by nanoceria, when the concentration of oxygen vacancies in nanoceria lattice, oxidant concentration in colloidal solution, and temperature reach certain critical values. So, the ability of nanoceria to uptake and release oxygen depending on the environmental redox conditions really makes it the self-sufficient eternal antioxidant.