Prokaryotic and eukaryotic toxicity of halloysite decorated with photoactive nanoparticles.

The development of new approaches to treat the growing antibiotic resistance of pathogenic bacterial species is an important task to ensure the future safety of society. Utilization of irradiation of different wavelengths together with nanostructured materials based on metal containing nanoparticles may result in synergetic antibacterial effects. In this paper we aim to show the main conceptions of light-assisted bacteria deactivation techniques and prospects of application of natural clay nanotubes as a carrier for scalable photoactive antibacterial nanomaterials. Halloysite aluminosilicate nanotubes (ca 50 nm diameter, ca. 1.0 µm length) are safe and biocompatible natural materials produced in tons. Their application as a template or a carrier for metal nanoparticles, QDs and organic compounds has already found application in biomedical research, cosmetics, polymers, coatings, catalysis and related applications. Here, we show the toxicity of halloysite decorated with photoactive nanoparticles on prokaryotic and eukaryotic cells. The formation of light active nanostructured materials with this clay as the base is a promising tool for solving the problem of the antibiotic resistance of microorganisms.

Photoinduced Antibacterial Activity and Cytotoxicity of CdS Stabilized on Mesoporous Aluminosilicates and Silicates.

Inactivation of bacteria under the influence of visible light in presence of nanostructured materials is an alternative approach to overcome the serious problem of the growing resistance of pathogenic bacteria to antibiotics. Cadmium sulfide quantum dots are superefficient photocatalytic material suitable for visible light transformation. In this work, CdS nanoparticles with size of less than 10 nm (QDs) were synthesized on the surface of natural and synthetic mesoporous aluminosilicates and silicates (halloysite nanotubes, MCM-41, MCM-41/Halloysite, SBA-15). Materials containing 5-7 wt.% of CdS were characterized and tested as agents for photocatalytic bacteria degradation of Gram-positive S. aureus and Gram-negative E. coli with multiple antibiotic resistance. Eukaryotic cell viability tests were also conducted on the model cancer cells A 459. We found that the carrier affects prokaryotic and eukaryotic toxicity of CdS quantum dots. CdS/MCM-41/HNTs were assumed to be less toxic to eukaryotic cells and possess the most prominent photocatalytic antibacterial efficiency. Under visible light irradiation, it induced 100% bacterial growth inhibition at the concentration of 125 µg/mL and the bacteriostatic effect at the concentration of 63 µg/mL. CdS/MCM-41/HNTs showed 100% E. coli growth inhibition in the concentration of 1000 µg/mL under visible light irradiation.

Biodistribution of Quantum Dots-Labelled Halloysite Nanotubes: A Caenorhabditis elegans In Vivo Study.

Halloysite is a promising building block in nanoarchitectonics of functional materials, especially in the development of novel biomaterials and smart coatings. Understanding the behavior of materials produced using halloysite nanotubes within living organisms is essential for their safe applications. In this study, quantum dots of different compositions were synthesized on the surface of modified clay nanotubes, and the biodistribution of this hybrid material was monitored within Caenorhabditis elegans nematodes. The influence of the modification agent as well as the particles' composition on physicochemical properties of hybrid nanomaterials was investigated. Several microscopy techniques, such as fluorescence and dark-field microscopy, were compared in monitoring the distribution of nanomaterials in nematodes' organisms. The effects of QDs-halloysite composites on the nematodes' life cycle were investigated in vivo. Our fluorescent hybrid probes induced no acute toxic effects in model organisms. The stable fluorescence and low toxicity towards the organisms suggest that the proposed synthesis procedure yields safe nanoarchitectonic materials that will be helpful in monitoring the behavior of nanomaterials inside living cells and organisms.