Evidence of residual micellar structures in a lipid nanocapsule dispersion. A multi-technique approach

Nanoemulsions are metastable emulsions in the nanometric range which can be obtained using low-energy processes. A decade ago, it was demonstrated that a non-negligible amount of residual surfactant micelles may coexist with the oil nanodroplets in a model oil/surfactant system. Those micelles were called "wasted" micelles as they did not participate in the formation of the nanodroplets. Little attention has been focused on the potential presence or effect of such secondary structures in nanoemulsions used as drug delivery systems. Here, we present an extensive characterization of lipid nanocapsules, a nanoemulsion obtained from a medium-chain triglyceride mixed with a pegylated surfactant by a process comprising a temperature-dependent phase inversion followed by a cold-water quench. Lipid nanocapsules demonstrate a very good shelf stability. First, for clarity and academic purposes, we briefly present the pros and the cons of the various diffusion-based characterization techniques used i.e., multi-angle and single-angle dynamic light scattering, nanoparticle tracking analysis, fluorescence recovery after photobleaching, and diffusometry nuclear magnetic resonance. Then, combining all these techniques, we show that up to 40 wt% of the surfactant is not involved in the lipid nanocapsule construction but forms residual micellar structures. Those micelles also contain a small quantity of medium-chain triglyceride (2 wt% of the initial amount) and encapsulate around 40 wt% of a fluorescent dye originally dispersed in the oily phase.

Syntheses and NMR and XRD studies of carbohydrate–ferrocene conjugates

Carbohydrate–ferrocene conjugates show a splitting of all the ¹H NMR signals of the substituted cyclopentadienyl. XRD of crystals seems to indicate that the R group could be responsible for the splitting of the NMR signals.

13C-NMR dereplication of Garcinia extracts: Predicted chemical shifts as reliable databases

Usually isolated from Garcinia (Clusiaceae) or Hypericum (Hypericaceae) species, some Polycyclic Polyprenylated AcylPhloroglucinols (PPAPs) have been recently reported as potential research tools for immunotherapy. Aiming at exploring the chemodiversity of PPAPs amongst Garcinia genus, a dereplication process suitable for such natural compounds has been developed. Although less sensitive than mass spectrometry, NMR spectroscopy is perfectly reproducible and allows stereoisomers distinction, justifying the development of ¹³C-NMR strategies. Dereplication requires the use of databases (DBs). To define if predicted DBs were accurate enough as dereplication tools, experimental and predicted δ_C of natural products usually isolated from Clusiaceae were compared. The ACD/Labs commercial software allowed to predict 73% of δ_C in a 1.25 ppm range around the experimental values. Consequently, with these parameters, the major PPAPs from a Garcinia bancana extract were successfully identified using a predicted DB.

Chemical Composition of Laurencia obtusa Extract and Isolation of a New C15-Acetogenin

A new C₁₅-acetogenin, sagonenyne (20), exhibiting an unusual single tetrahydropyran ring was isolated from an ethyl acetate extract of Laurencia obtusa collected on the Corsican coastline. Its structure was established by detailed NMR spectroscopic analysis, mass spectrometry, and comparison with literature data. Twenty-three known compounds were identified in the same extract by means of column chromatography steps, using a ¹³C-NMR computer aided method developed in our laboratory. In addition to sesquiterpenes, which represent the main chemical class of this extract, diterpenes, sterols, and C₁₅-acetogenins were identified. The crude extract was submitted to a cytotoxicity assay and was particularly active against THP-1 cells, a human leukemia monocytic cell line.

Synthesis and conformation of a novel fluorescein–Zn-porphyrin dyad and intramolecular energy transfer

Modulations of the optical properties of a new porphyrin–fluorescein dyad were elucidated using experimental and theoretical techniques, with conformational rearrangements being studied.

In vitro expansion of U87-MG human glioblastoma cells under hypoxic conditions affects glucose metabolism and subsequent in vivo growth

Hypoxia is a characteristic feature of solid tumors leading to the over expression of hypoxia-inducible factor (HIF)-1α protein and therefore to a specific cellular behavior. However, even though the oxygen tension in tumors is low (<5 %), most of the cell lines used in cancer studies are grown under 21 % oxygen tension. This work focuses on the impact of oxygen conditions during in vitro cell culture on glucose metabolism using 1-(13)C-glucose. Growing U87-MG glioma cells under hypoxic conditions leads to a two- to threefold reduction of labeled glutamine and an accumulation of fructose. However, under both hypoxic and normoxic conditions, glucose is used for de novo synthesis of pyrimidine since the (13)C label is found both in the uracil and ribose moieties. Labeling of the ribose ring demonstrates that U87-MG glioma cells use the reversible branch of the non-oxidative pentose phosphate pathway. Interestingly, stereotactic implantation of U87-MG cells grown under normoxia or mild hypoxia within the striatum of nude mice led to differential growth; the cells grown under hypoxia retaining an imprint of the oxygen adaptation as their development is then slowed down.

Role of mannitol metabolism in the pathogenicity of the necrotrophic fungus Alternaria brassicicola

In this study, the physiological functions of fungal mannitol metabolism in the pathogenicity and protection against environmental stresses were investigated in the necrotrophic fungus Alternaria brassicicola. Mannitol metabolism was examined during infection of Brassica oleracea leaves by sequential HPLC quantification of the major soluble carbohydrates and expression analysis of genes encoding two proteins of mannitol metabolism, i.e., a mannitol dehydrogenase (AbMdh), and a mannitol-1-phosphate dehydrogenase (AbMpd). Knockout mutants deficient for AbMdh or AbMpd and a double mutant lacking both enzyme activities were constructed. Their capacity to cope with various oxidative and drought stresses and their pathogenic behavior were evaluated. Metabolic and gene expression profiling indicated an increase in mannitol production during plant infection. Depending on the mutants, distinct pathogenic processes, such as leaf and silique colonization, sporulation, survival on seeds, were impaired by comparison to the wild-type. This pathogenic alteration could be partly explained by the differential susceptibilities of mutants to oxidative and drought stresses. These results highlight the importance of mannitol metabolism with respect to the ability of A. brassicicola to efficiently accomplish key steps of its pathogenic life cycle.

The serum growth hormone-binding protein is reduced in young patients with insulin-dependent diabetes mellitus

Despite elevated serum concentrations of GH, longitudinal growth is stunted in a considerable number of children and adolescents with insulin-dependent diabetes mellitus (IDDM). To elucidate, whether reduced peripheral action of GH contributes to this phenomenon, GH-binding protein (GH-BP) activity was measured in 117 children and adolescents with IDDM (mean age 14.6 yr, range 4.5-28 yr) and 132 healthy controls (13.1 yr, 6.3-26 yr). Serum was incubated with 125I-GH, then chromatographed on a Sephacryl S200 column (1.8.100 cm), apparent binding of 125I-GH to GH-BP was corrected for the amount of endogenous GH present in the sample. GH-BP activity was significantly lower in IDDM patients, with a corrected binding of 16.8 +/- 0.6% compared to 21.3 +/- 0.7% in control children (mean +/- SE; P < 0.0001, Wilcoxon-test). Previous studies demonstrated that GH-BP is increased in healthy overweight children. In contrast, in IDDM children, GH-BP was reduced despite a moderate degree of overweight (z-score for weight: +0.94 +/- 0.12; mean +/- SE). Reduced serum GH-BP activity in IDDM children is further accentuated when compared to healthy children with a similar degree of overweight (22.8 +/- 0.5%; n = 44). Based on this novel finding, we conclude that decreased GH receptor density may explain reduced growth velocity despite increased secretion of GH in some IDDM children.

Binding protein for human growth hormone: effects of age and weight

In human serum, a specific binding protein with high affinity for human growth hormone (GHBP) is found which is identical to the extracellular portion of the hepatic GH receptor. GHBP is assessed by incubating serum samples with [125I]-GH, followed by separation of bound and free radioactivity using gel chromatography. In newborns and children younger than 2 months, GHBP was practically absent and no 'big-big' GH could be found. GHBP values increased rapidly during the first 2 years of life, followed by a slower increase during childhood and puberty. No difference was found between male and female subjects. Apart from age, standardized weight (SDS = z score) had a major positive effect on GHBP concentration. Interestingly, SDS height correlated negatively with GHBP when weight and age were controlled for. These data may relate to two clinical findings: (1) the developmental switch between GH-independent intrauterine and GH-dependent postnatal growth mechanisms, and (2) the accelerated growth velocity encountered in adipose children.