Metal Ion–Zeolite Materials against Resistant Bacteria, MRSA

Machine Learning-Assisted Optimization of Drug Combinations in Zeolite-Based Delivery Systems for Melanoma Therapy

Two independent artificial neural network (ANN) models were used to determine the optimal drug combination of zeolite-based delivery systems (ZDS) for cancer therapy. The systems were based on the NaY zeolite using silver (Ag+) and 5-fluorouracil (5-FU) as antimicrobial and antineoplastic agents. Different ZDS samples were prepared, and their characterization indicates the successful incorporation of both pharmacologically active species without any relevant changes to the zeolite structure. Silver acts as a counterion of the negative framework, and 5-FU retains its molecular integrity. The data from the A375 cell viability assays, involving ZDS samples (solid phase), 5-FU, and Ag+ aqueous solutions (liquid phase), were used to train two independent machine learning (ML) models. Both models exhibited a high level of accuracy in predicting the experimental cell viability results, allowing the development of a novel protocol for virtual cell viability assays. The findings suggest that the incorporation of both Ag and 5-FU into the zeolite structure significantly potentiates their anticancer activity when compared to that of the liquid phase. Additionally, two optimal AgY/5-FU@Y ratios were proposed to achieve the best cell viability outcomes. The ZDS also exhibited significant efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus); the predicted combination ratio is also effective against S. aureus, underscoring the potential of this approach as a therapeutic option for cancer-associated bacterial infections.

Research of Zeolite and Zeolite Water from Rhodope Mountains, Bulgaria

The physicochemical composition and antibacterial effect of aqueous zeolite infusion (spring zeolite water Sevtopolis with zeolite from deposit Beli plast, Bulgaria) obtained for 12 and 36 hours was tested. Ordinance No. 9/2001, Official State Gazette, issue 30, and Decree No.178/23.07.2004 regarding the quality of water intended for drinking and household purposes were applied to study the physicochemical composition. Staphylococcus aureus-ATCC and TSA-MRSA and Escherichia coli ATCC were used in the studies. Both tested zeolite waters reduced the amount of viable E. coli and S. aureus cells even when they were in high concentrations (106 cells/ml). The effect of the 36-hour infusion was better, under the influence of which after 60 minutes the number of live bacteria of both tested species decreases by almost half compared to the initial amounts. Slightly higher sensitivity to two zeolite waters was shown by E. coli, whose cells were reduced to about 35% after two hours of exposure zeolite water tested. However, about 20% of the cells of the tested bacteria survived even after 96 hours of exposure to these waters. Only in E. coli no growth was found after 96 hours of exposure to 12 hours zeolite water. These results show the effectiveness of zeolite for water purification from Gram-positive and Gram-negative bacteria, as well as prospects for the use of zeolite water as a prophylactic and auxiliary treatment for bacterial infections.

Rational Design and Characterisation of Novel Mono- and Bimetallic Antibacterial Linde Type A Zeolite Materials

The development of antimicrobial devices and surfaces requires the setup of suitable materials, able to store and release active principles. In this context, zeolites, which are microporous aluminosilicate minerals, hold great promise, since they are able to serve as a reservoir for metal-ions with antimicrobial properties. Here, we report on the preparation of Linde Type A zeolites, partially exchanged with combinations of metal-ions (Ag⁺, Cu²⁺, Zn²⁺) at different loadings (0.1–11.9 wt.%). We combine X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction to monitor the metal-ion contents, distribution, and conservation of the zeolite structure after exchange. Then, we evaluate their antimicrobial activity, using agar dilution and optical-density monitoring of Escherichia coli cultures. The results indicate that silver-loaded materials are at least 70-fold more active than the copper-, zinc-, and non-exchanged ones. Moreover, zeolites loaded with lower Ag⁺ concentrations remain active down to 0.1 wt.%, and their activities are directly proportional to the total Ag content. Sequential exchanges with two metal ions (Ag⁺ and either Cu²⁺, Zn²⁺) display synergetic or antagonist effects, depending on the quantity of the second metal. Altogether, this work shows that, by combining analytical and quantitative methods, it is possible to fine-tune the composition of bi-metal-exchanged zeolites, in order to maximise their antimicrobial potential, opening new ways for the development of next-generation composite zeolite-containing antimicrobial materials, with potential applications for the design of dental or bone implants, as well as biomedical devices and pharmaceutical products.

Zeolite-Supported Aggregate as Potential Antimicrobial Agents in Gypsum Composites

Relatively easy treatment of glass aggregates can lead to the formation of a highly porous zeolite aggregate. This study focuses on the possibility of using such an aggregate as an active additive to a gypsum binder. The physical properties of hardened gypsum composites with zeolite fillers doped with various metal ions (Ni²⁺, Cu²⁺, and Zn²⁺) have been compared. In addition to studies of the basic physical properties of the composites, structural and microstructural studies as well as antimicrobial tests were performed. It was found that the parameters of the composites with the addition of various ions do not differ significantly from the reference but modifies the microstructure. Among other things, the ions analyzed reduce the microporosity of gypsum composites. Using all aggregates, a product with adequate strength (above 2 MPa) and thermal conductivity (about 0.35 W/m·K) appropriate for typical lightweight gypsum composites can be obtained. The bacteriostatic effect of formulations with copper and zinc against Escherichia coli and with copper against Staphylococcus aureus was found.

Advances in Nanostructures for Antimicrobial Therapy

Microbial infections caused by a variety of drug-resistant microorganisms are more common, but there are fewer and fewer approved new antimicrobial chemotherapeutics for systemic administration capable of acting against these resistant infectious pathogens. Formulation innovations of existing drugs are gaining prominence, while the application of nanotechnologies is a useful alternative for improving/increasing the effect of existing antimicrobial drugs. Nanomaterials represent one of the possible strategies to address this unfortunate situation. This review aims to summarize the most current results of nanoformulations of antibiotics and antibacterial active nanomaterials. Nanoformulations of antimicrobial peptides, synergistic combinations of antimicrobial-active agents with nitric oxide donors or combinations of small organic molecules or polymers with metals, metal oxides or metalloids are discussed as well. The mechanisms of actions of selected nanoformulations, including systems with magnetic, photothermal or photodynamic effects, are briefly described.

Waste Glass-Derived Tobermorite Carriers for Ag+ and Zn2+ Ions

In this study, the layer-lattice calcium silicate hydrate mineral, tobermorite, was synthesized from waste green or amber container glass and separately ion-exchanged with Ag+ or Zn2+ ions under batch conditions. Hydrothermal treatment of stoichiometrically adjusted mixtures of waste glass and calcium oxide in 4 M NaOH(aq) at 125 °C yielded tobermorite products of ~75% crystallinity with mean silicate chain lengths of 17 units after one week. Maximum uptake of Zn2+ ions, ~0.55 mmol g−1, occurred after 72 h, and maximum uptake of Ag+ ions, ~0.59 mmol g−1, was established within 6 h. No significant differences in structure or ion-exchange behavior were observed between the tobermorites derived from either green or amber glass. Composite membranes of the biopolymer, chitosan, incorporating the original or ion-exchanged tobermorite phases were prepared by solvent casting, and their antimicrobial activities against S. aureus and E. coli were evaluated using the Kirby–Bauer assay. S. aureus and E. coli formed biofilms on pure chitosan and chitosan surfaces blended with the original tobermorites, whereas the composites containing Zn2+-substituted tobermorites defended against bacterial colonization. Distinct, clear zones were observed around the composites containing Ag+-substituted tobermorites which arose from the migration of the labile Ag+ ions from the lattices. This research has indicated that waste glass-derived tobermorites are functional carriers for antimicrobial ions with potential applications as fillers in polymeric composites to defend against the proliferation and transmission of pathogenic bacteria.