Synthesis and antibacterial activity of iron-hexacyanocobaltate nanoparticles

Mesoporous Oxidized Mn-Ca Nanoparticles as Potential Antimicrobial Agents for Wound Healing

Managing chronic non-healing wounds presents a significant clinical challenge due to their frequent bacterial infections. Mesoporous silica-based materials possess robust wound-healing capabilities attributed to their renowned antimicrobial properties. The current study details the advancement of mesoporous silicon-loaded MnO and CaO molecules (HMn-Ca) against bacterial infections and chronic non-healing wounds. HMn-Ca was synthesized by reducing manganese chloride and calcium chloride by urotropine solution with mesoporous silicon as the template, thereby transforming the manganese and calcium ions on the framework of mesoporous silicon. The developed HMn-Ca was investigated using scanning electron microscopy (SEM), transmission electron microscope (TEM), ultraviolet-visible (UV-visible), and visible spectrophotometry, followed by the determination of Zeta potential. The production of reactive oxygen species (ROS) was determined by using the 3,3,5,5-tetramethylbenzidine (TMB) oxidation reaction. The wound healing effectiveness of the synthesized HMn-Ca is evaluated in a bacterial-infected mouse model. The loading of MnO and CaO inside mesoporous silicon enhanced the generation of ROS and the capacity of bacterial capture, subsequently decomposing the bacterial membrane, leading to the puncturing of the bacterial membrane, followed by cellular demise. As a result, treatment with HMn-Ca could improve the healing of the bacterial-infected wound, illustrating a straightforward yet potent method for engineering nanozymes tailored for antibacterial therapy.

Antimicrobial sensitisers: Gatekeepers to avoid the development of multidrug-resistant bacteria

The resistance of multidrug-resistant bacteria to existing antibiotics forces the continued development of new antibiotics and antibacterial agents, but the high costs and long timeframe involved in the development of new agents renders the hope that existing antibiotics may again play a part. The "antibiotic adjuvant" is an indirect antibacterial strategy, but its vague concept has, in the past, limited the development speed of related drugs. In this review article, we put forward an accurate concept of a "non-self-antimicrobial sensitisers (NSAS)", to distinguish it from an "antibiotic adjuvant", and then discuss several scientific methods to restore bacterial sensitivity to antibiotics, and the sources and action mechanism of existing NSAS, in order to guide the development and further research of NSAS.

Mononuclear Perfluoroalkyl-Heterocyclic Complexes of Pd(II): Synthesis, Structural Characterization and Antimicrobial Activity

Two mononuclear Pd(II) complexes [PdCl₂(pfptp)] (1) and [PdCl₂(pfhtp)] (2), with ligands 2-(3-perfluoropropyl-1-methyl-1,2,4-triazole-5yl)-pyridine (pfptp) and 2-(3-perfluoroheptyl-1-methyl-1,2,4-triazole-5yl)-pyridine (pfhtp), were synthesized and structurally characterized. The two complexes showed a bidentate coordination of the ligand occurring through N atom of pyridine ring and N4 atom of 1,2,4-triazole. Both complexes showed antimicrobial activity when tested against both Gram-negative and Gram-positive bacterial strains.

A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains

Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobials against Gram-negative and -positive bacteria. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similar to commercial pectin, lemon IntegroPectin determined ca. 3-log reduction in Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL⁻¹. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL⁻¹ biopolymer concentration affording complete killing of the bacterial cells. Insights into the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance since citrus IntegroPectin biomaterials are also devoid of cytotoxic activity, as already shown for lemon IntegroPectin, opening the route to the development of new medical treatments of polymicrobial infections unlikely to develop drug resistance.

Formulation of Mesoporous Silica Nanoparticles for Controlled Release of Antimicrobials for Stone Preventive Conservation

The biotic deterioration of artifacts of archaeological and artistic interest mostly relies on the action of microorganisms capable of thriving under the most disparate environmental conditions. Thus, to attenuate biodeterioration phenomena, biocides can be used by the restorers to prevent or slow down the microbial growth. However, several factors such as biocide half-life, its wash-out because of environmental conditions, and its limited time of action make necessary its application repeatedly, leading to negative economic implications. Sound and successful treatments are represented by controlled release systems (CRSs) based on porous materials. Here, we report on the design and development of a CRS system based on mesoporous silica nanoparticles (MSNs), as a carrier, and loaded with a biocide. MSNs, with a diameter of 55 nm and cylindrical pores of ca. 3-8 nm arranged as parallel arrays concerning the NP diameter, and with 422 m²/g of specific surface area were synthesized by the sol-gel method assisted by oil in water emulsion. Biocide loading and release were carried out in water and monitored by UV-Vis Spectroscopy; in addition, microbiological assay was performed using as control the MCM-41 mesoporous silica loaded with the same biocide. The role of specific supramolecular interaction in regulating the release is discussed. Further, we demonstrated that this innovative formulation was useful in inhibiting the in vitro growth of Kocuria rhizophila, an environmental Gram-positive bacterial strain. Besides, the CRS here prepared reduced the bacterial biomass contaminating a real case study (i.e., stone derived from the Santa Margherita cave located in Sicily, Italy), after several months of treatment thus opening for innovative treatments of deteriorated stone artifacts.

New Synthetic Nitro-Pyrrolomycins as Promising Antibacterial and Anticancer Agents

Pyrrolomycins (PMs) are polyhalogenated antibiotics known as powerful biologically active compounds, yet featuring high cytotoxicity. The present study reports the antibacterial and antitumoral properties of new chemically synthesized PMs, where the three positions of the pyrrolic nucleus were replaced by nitro groups, aiming to reduce their cytotoxicity while maintaining or even enhancing the biological activity. Indeed, the presence of the nitro substituent in diverse positions of the pyrrole determined an improvement of the minimal bactericidal concentration (MBC) against Gram-positive (i.e., Staphylococcus aureus) or -negative (i.e., Pseudomonas aeruginosa) pathogen strains as compared to the natural PM-C. Moreover, some new nitro-PMs were as active as or more than PM-C in inhibiting the proliferation of colon (HCT116) and breast (MCF 7) cancer cell lines and were less toxic towards normal epithelial (hTERT RPE-1) cells. Altogether, our findings contribute to increase the knowledge of the mode of action of these promising molecules and provide a basis for their rationale chemical or biological manipulation.

Graphene Oxide Carboxymethylcellulose Nanocomposite for Dressing Materials

Sore, infected wounds are a major clinical issue, and there is thus an urgent need for novel biomaterials as multifunctional constituents for dressings. A set of biocomposites was prepared by solvent casting using different concentrations of carboxymethylcellulose (CMC) and exfoliated graphene oxide (Exf-GO) as a filler. Exf-GO was first obtained by the strong oxidation and exfoliation of graphite. The structural, morphological and mechanical properties of the composites (CMCx/Exf-GO) were evaluated, and the obtained composites were homogenous, transparent and brownish in color. The results confirmed that Exf-GO may be homogeneously dispersed in CMC. It was found that the composite has an inhibitory activity against the Gram-positive Staphylococcus aureus, but not against Gram-negative Pseudomonas aeruginosa. At the same time, it does not exhibit any cytotoxic effect on normal fibroblasts.

Effect of Water and Alkali-Ion Content on the Structure of Manganese(II) Hexacyanoferrate(II) by a Joint Operando X-ray Absorption Spectroscopy and Chemometric Approach

Manganese hexacyanoferrate (MnHCF) is made of earth-abundant elements by a safe and easy synthesis. The material features a higher specific capacity at a higher potential than other Prussian blue analogs. However, the effect of hydration is critical to determine the electrochemical performance as both the electrochemical behavior and the reaction dynamics are affected by interstitial/structural water and adsorbed water. In this study, the electrochemical activity of MnHCF is investigated by varying the interstitial ion content through a joint operando X-ray absorption spectroscopy and chemometric approach, with the intent to assess the structural and electronic modifications that occur during Na release and Li insertion, as well as the overall dynamic evolution of the system. In MnHCF, both the Fe and Mn centers are electrochemically active and undergo reversible oxidation during the interstitial ion extraction (Fe2+ /Fe3+ and Mn2+ /Mn3+ ). The adsorption of water results in irreversible capacity during charge but only on the Fe site, which is suggested by our chemometric analysis. The local environment of Mn experiences a substantial yet reversible Jahn-Teller effect upon interstitial ion removal because of the formation of trivalent Mn, which is associated with a decrease of the equatorial Mn-N bond lengths by 10 %.

Essential Oil Composition of Alluaudia procera and in Vitro Biological Activity on Two Drug-Resistant Models

Drug resistance is a major obstacle in antibiotic and antitumor chemotherapy. In response to the necessity to find new therapeutic strategies, plant secondary metabolites including essential oils (EOs) may represent one of the best sources. EOs in plants act as constitutive defenses against biotic and abiotic stress, and they play an important role in the pharmacology for their low toxicity, good pharmacokinetic and multitarget activity. In this context, natural products such as EOs are one of the most important sources of drugs used in pharmaceutical therapeutics. The aim of this paper was to identify the chemical composition of the essential oil of Alluaudia procera leaves, obtained by hydrodistillation and analysed by gas chromatography-mass spectrometry, and to verify its biological activities on acute myeloid leukemia cancer cell HL60 and its multidrugresistant variant HL60R and the Gram-positive Staphylococcus aureus exhibiting multi-antibiotic resistance. We speculate that cytotoxic and antibiotic effects observed in the tested resistant models may be due to the coordinate activities of forty compounds detected or to the C₁₆ macrocyclic lactones which are the major ones (30%). Our data confirm the possibility of using EOs as therapeutic strategies in resistant models is due to the heterogeneous composition of the oils themselves.

Operando XAFS and XRD Study of a Prussian Blue Analogue Cathode Material: Iron Hexacyanocobaltate

The reversible electrochemical lithiation of potassium iron hexacyanocobaltate (FeCo) was studied by operando X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) assisted by chemometric techniques. In this way, it was possible to follow the system dynamics and retrieve structural and electronic transformations along cycling at both Fe and Co sites. These analyses confirmed that FeCo features iron as the main electroactive site. Even though the release of potassium ions causes a local disorder around the iron site, the material exhibits an excellent structural stability during the alkali ion deinsertion/insertion processes. An independent but interrelated analysis approach offers a good strategy for data treatment and provides a time-resolved picture of the studied system.

Recent Developments in Food Packaging Based on Nanomaterials

The increasing demand for high food quality and safety, and concerns of environment sustainable development have been encouraging researchers in the food industry to exploit the robust and green biodegradable nanocomposites, which provide new opportunities and challenges for the development of nanomaterials in the food industry. This review paper aims at summarizing the recent three years of research findings on the new development of nanomaterials for food packaging. Two categories of nanomaterials (i.e., inorganic and organic) are included. The synthetic methods, physical and chemical properties, biological activity, and applications in food systems and safety assessments of each nanomaterial are presented. This review also highlights the possible mechanisms of antimicrobial activity against bacteria of certain active nanomaterials and their health concerns. It concludes with an outlook of the nanomaterials functionalized in food packaging.