LASU: An efficient and stable phthalocyanine dye with tolerable safety profile for self-disinfecting anti-COVID textiles activated by ambient light.

BACKGROUND: Recent COVID crisis has demonstrated that modern society urgently needs an accessible protection against mass infections, especially viruses, as the new strains are appearing at an ever-increasing pace and cause severe harm to the population and the world economy. METHODS: We have developed an efficient phthalocyanine photosensitizer LASU, that is suitable for dyeing textiles and allows to prepare reusable self-disinfecting fabrics with strong antiviral properties. The safety profile of LASU was evaluated in accredited laboratories by several in vitro assays according to the OECD-guidelines. RESULTS: The textiles impregnated with LASU phthalocyanine showed a significant antiviral photodynamic effect even under moderate indoor and outdoor light. The dye did not show any genotoxic potential in human lymphocyte micronucleus assay. It showed a possible indication for eye irritation in human EpiOcular™ model and was phototoxic when tested in mouse BALB/c 3T3 cell test in the presence and absence of UVA-irradiation. CONCLUSION: Novel phthalocyanine-dyed textiles are suitable for general use as self-disinfecting antiviral barriers and materials in hospitals, households, and public places. The safety profile of LASU is the phototoxic effect which is related to LASU´s mode of action.

Coating gold nanorods with silica prevents the generation of reactive oxygen species under laser light irradiation for safe biomedical applications.

Gold nanoparticles can produce reactive oxygen species (ROS) under the action of ultrashort pulsed light. While beneficial for photodynamic therapy, this phenomenon is prohibitive for other biomedical applications such as imaging, photo-thermal drug release, or targeted gene delivery. Here, ROS are produced in water by irradiating gold nanorods and silica-coated gold nanorods with near-infrared femtosecond laser pulses and are detected using two fluorescent probes. Our results demonstrate that a dense silica shell around gold nanorods inhibits the formation of singlet oxygen (1O2) and hydroxyl radical (˙OH) efficiently. The silica coating prevents the Dexter energy transfer between the nanoparticles and 3O2, stopping thus the generation of 1O2. In addition, numerical simulations accounting for the use of ultrashort laser pulses show that the plasmonic field enhancement at the nanoparticle vicinity is lessened once adding the silica layer. With the multiphotonic ejection of electrons being also blocked, all the possible pathways for ROS production are hindered by adding the silica shell around gold nanorods, making them safer for a range of biomedical developments.

Contraction behaviors of Vorticella sp. stalk investigated using high-speed video camera. I: Nucleation and growth model.

The contraction process of living Vorticella sp. has been investigated by image processing using a high-speed video camera. In order to express the temporal change in the stalk length resulting from the contraction, a damped spring model and a nucleation and growth model are applied. A double exponential is deduced from a conventional damped spring model, while a stretched exponential is newly proposed from a nucleation and growth model. The stretched exponential function is more suitable for the curve fitting and suggests a more particular contraction mechanism in which the contraction of the stalk begins near the cell body and spreads downwards along the stalk. The index value of the stretched exponential is evaluated in the range from 1 to 2 in accordance with the model in which the contraction undergoes through nucleation and growth in a one-dimensional space.

Contraction behaviors of Vorticella sp. stalk investigated using high-speed video camera. II: Viscosity effect of several types of polymer additives.

The contraction process of living Vorticella sp. in polymer solutions with various viscosities has been investigated by image processing using a high-speed video camera. The viscosity of the external fluid ranges from 1 to 5mPa·s for different polymer additives such as hydroxypropyl cellulose, polyethylene oxide, and Ficoll. The temporal change in the contraction length of Vorticella sp. in various macromolecular solutions is fitted well by a stretched exponential function based on the nucleation and growth model. The maximum speed of the contractile process monotonically decreases with an increase in the external viscosity, in accordance with power law behavior. The index values approximate to 0.5 and this suggests that the viscous energy dissipated by the contraction of Vorticella sp. is constant in a macromolecular environment.

Fluorescence microscopy coupled to electrochemistry: a powerful tool for the controlled electrochemical switch of fluorescent molecules.

The first-time coupling of fluorescence microscopy with a three-electrode electrochemical cell is described and applied to the investigation of a controlled-potential redox switch of organic fluorophores such as tetrazine derivatives.