Antimicrobial activity of anion exchangers containing cupric compounds against Enterococcus faecalis

Biocidal activity of multifunctional cuprite-doped anion exchanger - Influence of bacteria type and medium composition

The study presents unconventional, bifunctional, heterogeneous antimicrobial agents - Cu2O-loaded anion exchangers. The synergetic effect of a cuprous oxide deposit and polymeric support with trimethyl ammonium groups was studied against the reference strains of Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853. Biological testing (minimum bactericidal concentration, MBC), time- and dose-dependent bactericidal effect (under different conditions - medium composition and static/dynamic culture) demonstrated promising antimicrobial activity and confirmed its multimode character. The standard values of MBC, for all studied hybrid polymers and bacteria, were similar (64-128 mg/mL). However, depending on the medium conditions, due to the copper release into the bulk solution, bacteria were actively killed even at much lower doses of the hybrid polymer (25 mg/mL) and low Cu(II) concentrations in solution (0.01 mg/L). Simultaneously, confocal microscopic studies confirmed the effective inhibition of bacterial adhesion and biofilm formation on their surface. The studies conducted under different conditions showed also the influence of the structure and physical properties of studied materials on the biocidal efficacy and an antimicrobial action mechanism was proposed that could be significantly affected by electrostatic interactions and copper release to the solution. Although the antibacterial activity was also dependent on various strategies of bacterial cell resistance to heavy metals present in the aqueous medium, the studied hybrid polymers are versatile and efficient biocidal agents against bacteria of both types, Gram-positive and Gram-negative. Therefore, they can be a convenient alternative for point-of-use water disinfection systems providing water quality in medical devices such as dental units, spa equipment, and aesthetic devices used in the cosmetic sector.

Multifunctional Composite Materials Based on Anion Exchangers Modified with Copper Compounds-A Review of Their Synthesis Methods, Characteristics and Applications

As copper and its compounds are of fundamental importance for the development of innovative materials, the synthesis of composites intended for water purification was undertaken in which submicron copper containing particles were dispersed within the matrix of a strongly basic anion exchanger, with a macroporous and gel-like structure. Due to their trimethylammonium functional groups, the host materials alone exhibited an affinity to anionic water contaminants and antimicrobial properties. The introduction of such particles as CuO, Cu2O, metallic Cu, CuO/FeO(OH), Cu4O3, Cu(OH)2, Cu4(OH)6SO4, Cu2(OH)3Cl increased these properties and demonstrated new properties. The composites were obtained unconventionally, in ambient conditions, using eco-friendly reagents. Alternative synthesis methods were compared and optimized, as a result of which a new group of hybrid ion exchangers was created (HIXs) containing 3.5-12.5 wt% of Cu. As the arrangement of the inorganic phase in the resin matrix was atypical, i.e., close to the surface of the beads, the obtained HIXs exhibited excellent kinetic properties in the process of oxidation and adsorption of As(III), as well as catalytic properties for the synthesis of triazoles via click reaction, and also antimicrobial properties in relation to Gram-positive Enterococcus faecalis and Gram-negative Pseudomonas aeruginosa and Escherichia coli, preventing biofilm formation. Using thermogravimetry, the effect of the inorganic phase on decomposition of the polymeric phase was evaluated for the first time and comprehensively, confirming the relationship and finding numerous regularities. It was also found that, depending on the oxidation state (CuO, Cu2O, Cu), copper-containing particles affected the textural properties of the polymeric phase endowing a tighter structure, limiting the porosity and reducing the affinity for water.

Copper Rich Composite Materials Based on Carboxylic Cation Exchangers and Their Thermal Transformation

The effect of a cupric deposit (Cu2+, CuO) on the thermal decomposition of carboxylic cation exchangers (CCEs) is not known, and such studies may have practical significance. CCEs have a very high ion exchange capacity, so an exceptionally large amount of CuO (which is a catalyst) can be precipitated inside them. Two CCEs, macroreticular (Amberlite IRC50) and gel-like (Amberlite IRC86), served as a polymeric support to obtain copper-rich hybrid ion exchangers. Composites with CuO particles inside a polyacrylic matrix (up to 35.0 wt% Cu) were obtained. Thermal analyses under air and under N2 were performed for CCEs in the H+ and Cu2+ form with and without a CuO deposit. The results of sixteen experiments are discussed based on the TG/DTG curves and XRD patterns of the solid residues. Under air, the cupric deposit shifted the particular transformations and the ultimate polymeric matter decomposition (combustion) toward lower temperatures (even about 100-150 °C). Under N2, the reduction of the cupric deposit to metallic copper took place. Unique composite materials enriched in carbonaceous matter were obtained, as the products of polymeric matrix decomposition (free radicals and hydrogen) created an additional amount of carbon char due to the utilization of a certain amount of hydrogen to reduce Cu (II) to Cu0.

Size-Controlled Transformation of Cu2O into Zero Valent Copper within the Matrix of Anion Exchangers via Green Chemical Reduction

Composite materials containing zero valent copper (ZVC) dispersed in the matrix of two commercially available strongly basic anion exchangers with a macroreticular (Amberlite IRA 900Cl) and gel-like (Amberlite IRA 402OH) structure were obtained. Cu0 particles appeared in the resin phase as the product of the reduction of the precursor, i.e., copper oxide(I) particles previously deposited in the two supporting materials. As a result of a one-step transformation of preformed Cu2O particles as templates conducted using green reductant ascorbic acid and under mild conditions, macroporous and gel-type hybrid products containing ZVC were obtained with a total copper content of 7.7 and 5.3 wt%, respectively. X-ray diffraction and FTIR spectroscopy confirmed the successful transformation of the starting oxide particles into a metallic deposit. A scanning electron microscopy study showed that the morphology of the deposit is mainly influenced by the type of matrix exchanger. In turn, the drying steps were crucial to its porosity and mechanical resistance. Because both the shape and size of copper particles and the internal structure of the supporting solid materials can have a decisive impact on the potential applications of the obtained materials, the results presented here reveal a great possibility for the design and synthesis of functional nanocrystalline solids.