Straightforward Way to Provide Antibacterial Properties to Healthcare Textiles through N-2-Hydroxypropyltrimethylammonium Chloride Chitosan Crosslinking.

A straightforward and cost-effective way to coat polypropylene fibers, designed for healthcare textiles, was developed through chitosan crosslinking for antibacterial purposes. As polypropylene is an inert material, the goal was to physically trap the inert fibers through a network of crosslinked chitosan or a quaternized derivative (to enhance the antibacterial action). First, chitosan or its quaternized derivative was physically deposited by impregnation or spraying. Then, chitosan was crosslinked in glutaraldehyde solution followed by its quaternized derivative with a diisocyanate. Coated fabrics were characterized by infrared spectroscopy (IR), weight gain measurements, and scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX). This led us to conclude that spraying provides uniform deposition while maintaining the fabric's porosity. Acidic washing allowed us to prove that chitosan and its quaternized derivative were successfully immobilized on the fabric. Biological assays were conducted against two major strains of bacteria responsible for nosocomial infections: Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). Chitosan-crosslinked samples did not show significant antibacterial activity, but the quaternized derivative allowed a significant decrease in S. aureus colonization. This study presents a simple and scalable process to coat inert fabrics with a polymer containing reactive functions potentially available to graft various additional antimicrobial agents.

Green Physical Modification of Polypropylene Fabrics by Cross-Linking Chitosan with Tannic Acid and Postmodification by Quaternary Ammonium Grafting to Improve Antibacterial Activity.

A green cross-linking and straightforward method to physically trap inert fibers in a network of chitosan was implemented. The cross-linking reaction involved a biosourced and biocompatible cross-linker [tannic acid (TA)] and mild conditions in water (pH = 8.5, O2 bubbling, 60 °C, 3 h). The steric hindrance of TA led to a low but effective cross-linking rate leaving parts of primary amines of chitosan available for postmodification such as the grafting of quaternary ammoniums for antibacterial purposes. Fabric's coatings were characterized by scanning electron microscopy coupled with energy-dispersive X-ray, infrared spectroscopy, and weight gain measurements. This allowed the optimization of process conditions. No significant antioxidant activity was observed on fabrics coated with chitosan cross-linked with TA, confirming the low cross-linking rate. This low cross-linking rate allowed grafting of quaternary ammoniums for antibacterial purposes, but it is possible to consider grafting other active molecules. Biological assays were conducted on this coating to assess its antibacterial properties. Reduction of bacterial colonization on both Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), two of the major strains responsible for nosocomial infections, confirmed the potential of the coating for antibacterial purposes. This study displays a simple and ecofriendly process to coat inert fabrics with a chitosan network containing reactive functions (primary amines) available for grafting active molecules for various purposes.

Electrochemically Deposited Zinc (Tetraamino)phthalocyanine as a Light-activated Antimicrobial Coating Effective against S. aureus.

Light-activated antimicrobial coatings are currently considered to be a promising approach for the prevention of nosocomial infections. In this work, we present a straightforward strategy for the deposition of a photoactive biocidal organic layer of zinc (tetraamino)phthalocyanine (ZnPcNH2) in an electrochemical oxidative process. The chemical structure and morphology of the resulting layer are widely characterized by microscopic and spectroscopic techniques, while its ability to photogenerate reactive oxygen species (ROS) is investigated in situ by UV-Vis spectroscopy with α-terpinene or 1,3-diphenylisobenzofuran as a chemical trap. It is shown that the ZnPcNH2 photosensitizer retained its photoactivity after immobilization, and that the reported light-activated coating exhibits promising antimicrobial properties towards Staphyloccocus aureus (S. aureus).

Evaluation of trace metal accumulation in six vegetable crops intercropped with phytostabilizing plant species, in a French urban wasteland.

The extensive development of agriculture in urban and peri-urban wastelands polluted with several trace elements (TE) poses risks to human health through contaminated food products. The objective was to explore the accumulation of TE in the various parts of vegetable crop plants (tomato, French bean, radish, potato, spinach, and leek) intercropped with phytostabilizing plant species (ryegrass and white clover, respectively). Field studies were conducted in a multicontaminated French urban wasteland with Cd, Cu, Pb and Zn, and an alkaline soil pH. Analyses of the respective non-edible parts of monocultured vegetable crops showed accumulation of all TE, mostly Zn, then Pb and Cu, and finally Cd. The corresponding TE accumulation factors (soil to plant) were all below 0.25. In the edible parts, average concentrations for TE were above the limit values, according to European and Chinese standards. TE contents in the phytostabilizing species chosen were in the same orders of magnitude and the same ranking as described for vegetable crops and most accumulation was in the roots. Unexpectedly, the presence of the phytostabilizing plants had a very strong positive impact on the soil to plant accumulation factor. Moreover, the edible plant parts were poorly impacted by the co-cropping with phytostabilizing plants.

Highly Virulent Bactericidal Effects of Curcumin-Based µ-Cages Fabricated by Two-Photon Polymerization.

A new antibacterial strategy is reported based on two-photon fabrication of three-dimensional curcumin-embedded µ-cages. Such devices were designed to entrap and kill Staphylococcus aureus bacteria upon visible light irradiation. The proposed concept mainly relies on the pivotal role of curcumin, which is sequentially used as a two-photon active free radical initiator and as a photogenerator of reactive oxygen species within the cage µ-volumes. We show that these µ-cages exhibit extremely high antimicrobial properties, leading to 95% bacteria mortality after only 10 min visible irradiation. A preconcentration mechanism of photogenerated oxygen species is proposed to account for this highly performing bactericidal effect whose virulence can be strikingly switched on by increasing the light exposure time from 5 to 10 min.

Photoinitiating Systems Based on Anthraquinone Derivatives: Synthesis of Antifouling and Biocide Coatings.

Photoinitiating systems combining 2,6-diaminoanthraquinone (AQD), iodonium salt (Iod), and benzyl alcohol derivatives have been developed to efficiently initiate the cationic polymerization of epoxy monomers upon light exposure. Electron spin resonance spin-trapping (ESR ST) experiments, fluorescence investigations, and steady-state photolysis have demonstrated that a dye-sensitized reaction occurs between AQD and the benzyl alcohol derivatives through a hydrogen abstraction mechanism upon light illumination, followed by reduction of Iod. The in situ liberation of protic acids promotes the cationic photopolymerization of epoxy monomers concomitantly with hydrolysis and condensation of the reactive methoxysilanes of an organic-inorganic precursor, for example, 3-glycidyloxypropyltrimethoxysilane (GPTMS). Nanoindentation experiments and scratch resistance tests proved that the resulting GPTMS coatings exhibit very good resistance to brittle fracture and excellent adherence to stainless-steel substrates. Interestingly, antibacterial tests of the GPTMS coatings showed efficient antifouling and biocide properties against E. coli and S. aureus.

Relation between bacterial strain resistance to solvents and biodesulfurization activity in organic medium.

Microorganisms used in biodesulfurization of petroleum products have to withstand high concentrations of hydrocarbons. The capacities of seven desulfurizing strains of Rhodococcus to be active in the presence of solvents were evaluated. Octanol and toluene (log P=2.9) were selected as toxic solvents. The effect of the solvents was determined by measuring either inhibition of growth or the decrease in respiratory activity of the cells. Differences among strains in their resistance to solvent responses were observed, but these variations were dependent on the test used. Resistance to solvents was then compared to the capacity of the different strains to retain biodesulfurization activity in the presence of hexadecane. Inhibition of desulfurization by high concentrations of hexadecane was found to be well correlated to the sensitivity of the strains to respiration inhibition by toluene, but not to growth inhibition. This result also showed that the respirometric test was a rapid and reliable test to select solvent-resistant strains for use as resting cells in biocatalysis processes, such as biodesulfurization, in organic media.