We have fabricated ecocompatible Pickering emulsions based on halloysite nanotubes and ionic biopolymers (chitosan and pectin) from renewable resources. The effect of pectin and chitosan on the Pickering emulsion was investigated by direct visualization of the oil droplets and by the thermodynamic characterization at the interface. Pectin enhances the Pickering emulsion stability, while a phase separation and nonhomogeneous gel was observed in the presence of chitosan. We have demonstrated that the Pickering emulsion in a pectin based gel phase is suitable for wax layer removal from a marble surface. A controlled cleaning is achieved by tuning the contact time between the gel and the marble surface. Due to its nonhomogeneous structure, chitosan-based gel does not show proper wax removal ability. This work opens up a new sustainable approach in preparing cleaning formulations for conservation of cultural heritage.
Prodigiosin, a bioactive secondary metabolite produced by Serratia marcescens, is an effective proapoptotic agent against various cancer cell lines, with little or no toxicity toward normal cells. The hydrophobicity of prodigiosin limits its use for medical and biotechnological applications, these limitations, however, can be overcome by using nanoscale drug carriers, resulting in promising formulations for target delivery systems with great potential for anticancer therapy. Here we report on prodigiosinloaded halloysite-based nanoformulation and its effects on viability of malignant and non-malignant cells. We have found that prodigiosin-loaded halloysite nanotubes inhibit human epithelial colorectal adenocarcinoma (Caco-2) and human colon carcinoma (HCT116) cells proliferative activity. After treatment of Caco-2 cells with prodigiosinloaded halloysite nanotubes, we have observed a disorganization of the F-actin structure. Comparison of this effects on malignant (Caco-2, HCT116) and nonmalignant (MSC, HSF) cells suggests the selective cytotoxic and genotoxic activity of prodigiosin-HNTs nanoformulation.
Tannic acid-stabilized silver nanoparticles were synthesized in situ on halloysite clay nanotubes. The synthesis strategy included simple steps of tannic acid adsorption on clay nanotubes and further particle formation from silver salt solution. Pristine halloysite nanotubes as well as amino-modified clays were used for silver stabilization in water or ethanol. The materials were tested for antibacterial performance using three different methods. All of the materials produced showed antimicrobial activity. The pristine halloysite-based material with ~5 nm particles produced using ethanol as the solvent and tannic acid as the reducing agent showed the greatest antibacterial activity against Serratia marcescens. The materials were tested in vivo on Caenorhabditis elegans nematodes to ensure their safety, and they showed no negative effects on nematode growth and life expectancy.
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