Purification and structure elucidation of three naturally bioactive molecules from the new terrestrial Streptomyces sp. TN17 strain

Thirty litres of fermentation broth was extracted from the newly isolated Streptomyces sp. strain TN17 and various separation and purification steps led to the isolation of three pure bioactive compounds (1–3). Compound 1: cyclo (L-Leu-L-Arg), a diketopiperazine ‘DKP’ derivative; 2: di-(2-ethylhexyl) phthalate, a phthalate derivative; and 3: cyclo 1-[2-(cyclopentanecarbonyl-3-phenyl-propionyl]-pyrrolidine-2-carboxylic acid (1-carbamoyl-propyl)-amide, a cyclic tetrapeptide derivative. The chemical structure of these three active compounds was established on the basis of spectroscopic studies (MS and NMR) and by comparison with data from the literature. According to our biological studies, the pure compounds (1–3) possess antibacterial and antifungal activities

Taxonomy, purification and chemical characterization of four bioactive compounds from new Streptomyces sp. TN256 strain

A new actinomycete strain designated TN256, producing antimicrobial activity against pathogenic bacteria and fungi, was isolated from a Tunisian Saharan soil. Morphological and chemical studies indicated that strain TN256 belonged to the genus Streptomyces. Analysis of the 16S rDNA sequence of strain TN256 showed a similarity level ranging between 99.79 and 97.8% within Streptomyces microflavus DSM 40331T and Streptomyces griseorubiginosus DSM 40469T respectively. The comparison of its physiological characteristics showed significant differences with the nearest species. Combined analysis of the 16 S rRNA gene sequences (FN687758), fatty acids profile, and results of physiological and biochemical tests indicated that there were genotypic and phenotypic differentiations of that isolate from other Streptomyces species neighbours. These date strongly suggest that strain TN256 represents a novel species with the type strain Streptomyces TN256 (=CTM50228T). Experimental validation by DNA–DNA hybridization would be required for conclusive confirmation. Four active products (1–4) were isolated from the culture broth of Streptomyces TN256 using various separation and purification steps and procedures. 1: N-[2-(1H-indol-3-yl)-2 oxo-ethyl] acetamide ‘alkaloid’ derivative; 2: di-(2-ethylhexyl) phthalate, a phthalate derivative; 3: 1-Nonadecene and 4: Cyclo (l-Pro-l-Tyr) a diketopiperazine ‘DKP’ derivative. The chemical structure of these four active compounds was established on the basis of spectroscopic studies NMR and by comparing with data from the literature. According to our biological studies, we showed in this work that the pure compounds (1–4) possess antibacterial and antifungal activities

Ibuprofen loading into mesoporous silica nanoparticles using Co-Spray drying: A multi-scale study

Mesoporous Silica Nanoparticles (MSN) are used in an increasing number of applications in nanomedicine. Their synthesis and external/internal functionalization have been extensively studied as well as their biological properties. Nevertheless, the conventional drug loading processes of MSN (such as impregnation), do not enable sufficient efficiency and are difficult to consider on an industrial scale. To overcome these limitations, we implemented an innovative co-spray-drying process, using a nano spray-dryer, to load MSN with ibuprofen molecules. In this contribution, complementary techniques were used to perform a multi-scale characterization of the loaded particles. Spray-dried powders have been analysed from aggregates size and morphology to pore loading and ibuprofen conformation. This study demonstrates that ibuprofen/silica weight ratio in the initial suspension strongly affects the location (into mesopores or external) and the conformation (crystallized, amorphous or liquid-like) of ibuprofen. The quantification of each phase has allowed calculating precise loading rates and demonstrate tunable pore filling

Oligomeric and polymeric surfactants for the transfer of luminescent ZnO nanocrystals to water

International audienceThe water dispersion of luminescent nanocrystals (NCs) synthesized in organic solvent by encapsulation in a surfactant bilayer is a promising strategy for preserving the optical properties of NCs. The phase transfer of highly monodispersed ZnO NCs using the monomer, dimer, trimer and polymer of a series of alkyl ammonium surfactants is compared. Transfer yields over 60% could be obtained with the oligomers and the polymer. In contrast, we observed no measurable transfer using the single chain surfactant. NMR spectroscopy, including DOSY and NOESY, demonstrated that increasing the oligomerization number ameliorates the stability within the coating bilayer. The NCs exhibit a strong luminescence in water and show long term chemical and photo-chemical stability

Saccharothrix algeriensis NRRL B-24137, the first non-Streptomyces actinobacterium, produces holomycin after cystine feeding

Saccharothrix algeriensis NRRL B-24137 is an actinobacterium isolated from Algerian Saharan soil. This strain has the ability to produce several dithiolopyrrolone antibiotic derivatives depending on the precursors added to the culture medium. This group of antibiotics is known for their potent antimicrobial and anticancer activities. Holomycin is a member of the dithiolopyrrolone group of antibiotics, and has already been isolated from several species of actinobacteria belonging to the genus Streptomyces and also from some Gram-negative bacteria. In this study, holomycin was produced for the first time in the culture broth of a non-Streptomyces actinobacteria. This antibiotic was induced by adding 5 mM of L-cystine as precursor to the semi-synthetic fermentation broth of Sa. algeriensis NRRL B-24137 and then fully identified after HPLC purification. The minimum inhibitory concentrations (MIC) of holomycin were determined against several pathogenic microorganisms, including Escherichia coli ATCC 10536 Klebsiella pneumoniae CIP 82.91, Listeria monocytogenes CIP 82110, Staphylococcus aureus CIP 7625, Aspergillus carbonarius M333, Fusarium culmorum FC1, Candida albicans IPA 200. This antibiotic showed a broad-spectrum antimicrobial activity, inhibiting a variety of Gram-positive and Gram-negative bacteria, and micro-fungi

A Novel Method for the Metallization of 3D Silicon Induced by Metastable Copper Nanoparticles

The development of efficient copper deposition processes in high-aspect-ratio silicon structures is still a key technological issue for the microelectronic industry. We describe here a new process for the deposition of copper thin films in three-dimensional (3D) structures induced by the decomposition of a copper amidinate precursor in solution under a moderate H2 pressure. The reduction of a metal precursor under soft conditions (3 bar, 110 °C) affords the preparation of a high-purity, conformal metallic layer. We unveil a novel deposition mechanism driven by colloidal copper nanoparticles (NPs) in solution that behave as a reservoir of metastable metallic NPs that eventually condense as a solid film on all immersed surfaces. The film growth process is characterized by time-resolved analyses of the NPs in the colloidal state (nuclear magnetic resonance NMR and UV–vis spectra) and of the NPs and metallic layer on substrates (transmission electron microscopy TEM, and scanning electron microscopy SEM). Major deposition stages of this process are proposed and the conformal metallization of 3D silicon substrates is successfully achieved. This method is transposable to other metallic layers such as silver or nickel

Consolidation of Spray-Dried Amorphous Calcium Phosphate by Ultrafast Compression: Chemical and Structural Overview

A large amount of research in orthopedic and maxillofacial domains is dedicated to the development of bioactive 3D scaffolds. This includes the search for highly resorbable compounds, capable of triggering cell activity and favoring bone regeneration. Considering the phosphocalcic nature of bone mineral, these aims can be achieved by the choice of amorphous calcium phosphates (ACPs). Because of their metastable property, these compounds are however to-date seldom used in bulk form. In this work, we used a non-conventional “cold sintering” approach based on ultrafast low-pressure RT compaction to successfully consolidate ACP pellets while preserving their amorphous nature (XRD). Complementary spectroscopic analyses (FTIR, Raman, solid-state NMR) and thermal analyses showed that the starting powder underwent slight physicochemical modifications, with a partial loss of water and local change in the HPO42- ion environment. The creation of an open porous structure, which is especially adapted for non-load bearing bone defects, was also observed. Moreover, the pellets obtained exhibited sufficient mechanical resistance allowing for manipulation, surgical placement and eventual cutting/reshaping in the operation room. Three-dimensional porous scaffolds of cold-sintered reactive ACP, fabricated through this low-energy, ultrafast consolidation process, show promise toward the development of highly bioactive and tailorable biomaterials for bone regeneration, also permitting combinations with various thermosensitive drugs

Bidimensional lamellar assembly by coordination of peptidic homopolymers to platinum nanoparticles

A key challenge for designing hybrid materials is the development of chemical tools to control the organization of inorganic nanoobjects at low scales, from mesoscopic (~µm) to nanometric (~nm). So far, the most efficient strategy to align assemblies of nanoparticles consists in a bottom-up approach by decorating block copolymer lamellae with nanoobjects. This well accomplished procedure is nonetheless limited by the thermodynamic constraints that govern copolymer assembly, the entropy of mixing as described by the Flory–Huggins solution theory supplemented by the critical influence of the volume fraction of the block components. Here we show that a completely different approach can lead to tunable 2D lamellar organization of nanoparticles with homopolymers only, on condition that few elementary rules are respected: 1) the polymer spontaneously allows a structural preorganization, 2) the polymer owns functional groups that interact with the nanoparticle surface, 3) the nanoparticles show a surface accessible for coordination

A new dithiolopyrrolone antibiotic triggered by a long fermentation of Saccharothrix algeriensis NRRL B‐24137 in sorbic acid‐amended medium

Saccharothrix algeriensis NRRL B‐24137 is an actinobacterium isolated from Algerian Saharan soil. It produces bioactive compounds belonging to the dithiolopyrrolone class of antibiotics, which are characterized by the possession of a unique pyrrolinonodithiole nucleus. Dithiolopyrrolones are known for their strong antibacterial and antifungal activities. This class of antibiotics generated great interest after the discovery of their anticancer properties. In this study, an antibiotic named PR11, produced after a long bacterial fermentation (11 days) in sorbic acid‐containing culture broth, was characterized as a new dithiolopyrrolone derivative. After HPLC analysis and purification, the chemical structure of this antibiotic was determined by 1H‐ and 13C‐nuclear magnetic resonance, mass and UV‐visible data. PR11 was thus characterized as an iso‐hexanoyl‐pyrrothine, a novel dithiolopyrrolone derivative. The minimum inhibitory concentrations of the new induced antibiotic were determined against several pathogenic micro‐organisms. A moderate to strong activity was noted against all Gram‐positive bacteria, filamentous fungi and yeasts tested