The differences of the impact of a lipid and protein corona on the colloidal stability, toxicity, and degradation behavior of iron oxide nanoparticles.

AIM: In this study, the influence of a serum albumin (SA) and human plasma (HP) derived protein- and lipid molecule corona on the toxicity and biodegradability of different iron oxide nanoparticles (IONP) was investigated. METHODS: IONP were synthesized and physicochemically characterized regarding size, charge, and colloidal stability. The adsorbed proteins were quantified and separated by gel electrophoresis. Adsorbed lipids were profiled by ultraperformance liquid chromatography-ESI-tandem mass spectrometry. The biocompatibility was investigated using isolated erythrocytes and a shell-less hen's egg model. The biodegradability was assessed by iron release studies in artificial body fluids. RESULTS: The adsorption patterns of proteins and lipids varied depending on the surface characteristics of the IONP like charge and hydrophobicity. The biomolecule corona modified IONP displayed favorable colloidal stability and toxicological profile compared to IONP without biomolecule coronas, reducing erythrocyte aggregation and hemolysis in vitro as well as the corresponding effects ex ovo/in vivo. The coronas decreased the degradation speed of all tested IONP compared to bare particles, but, whereas all IONP degraded at the same rate for the SA corona, substantial differences were evident for IONP with HP-derived corona depending on the lipid adsorption profile. CONCLUSION: In this study the impact of the proteins and lipids in the biomolecule corona on the entire IONP application cycle from the injection process to the degradation was demonstrated.

A shell-less hen's egg test as infection model to determine the biocompatibility and antimicrobial efficacy of drugs and drug formulations against Pseudomonas aeruginosa.

A shell-less hen's egg based infection test with Pseudomonas aeruginosa was established to investigate the antimicrobial efficacy of drugs and drug formulations close to the in vivo situation. The test system using preincubated fertilized chicken eggs transferred in petri dishes was optimized with respect to the controlled local application of liquid materials and bacteria as well as the bacterial cultivation conditions. The applicability of the ex ovo infection model was confirmed with antimicrobial susceptibility tests using tobramycin, ciprofloxacin and meropenem. The validity of the ex ovo data was demonstrated by correlation with in vitro data of the CellTiter®-Blue and the microplate laser nephelometry assay. Real-time imaging of the progress of infection and the efficacy of the treatment could be realized by the MolecuLight i:X™ technique. Furthermore, in a proof-of-concept efficacy, biocompatibility and even the presence of irritants were determined side-by-side using commercial ophthalmics. In conclusion, this egg based infection model could bridge the gap between in vitro and in vivo models for the evaluation of antimicrobial susceptibility to reduce animal tests according to the 3R concept.

Polysaccharide Nanoparticles Bearing HDAC Inhibitor as Nontoxic Nanocarrier for Drug Delivery.

The histone deacetylase inhibitors (HDACi) are potent drugs in the treatment of inflammatory diseases and defined cancer types. However, major drawbacks of HDACi, such as valproic acid (VPA), are limited serum half-life, side effects and the short circulation time. Thus, the immobilization of VPA in a polysaccharide matrix is used to circumvent these problems and to design a suitable nanocarrier system. Therefore, VPA is covalently attached to cellulose and dextran via esterification with degree of substitution (DS) values of up to 2.20. The resulting hydrophobic polymers are shaped to spherical nanoparticles (NPs) with hydrodynamic diameter between 138 to 221 nm and polydispersity indices from 0.064 to 0.094 by nanoprecipitation and emulsification technique. Lipase treatment of the NPs leads to in vitro release of VPA and hence to an inhibition of HDAC2 activity in a HDAC2 assay. NPs are rapidly taken up by HeLa cells and mainly localize in the cytoplasm. The NPs are hemocompatible and nontoxic as revealed by the shell-less hen's egg model.

Fungal Biosurfactants from Mortierella alpina.

The zygomycete Mortierella alpina is a well-known producer of polyunsaturated fatty acids in the food industry. Two series of its secondary metabolites are reported: Malpinins, a family of amphiphilic acetylated hexapeptides, were chemically characterized and serve as natural emulsifiers during lipid secretion. Additionally, hydrophobic cyclopentapeptides, malpibaldins, were structurally elucidated by NMR experiments, and their absolute stereochemistry was elucidated through chemical derivatization and synthesis. This work highlights lower fungi as a novel reservoir for natural products.

4-Methylcatechol, a Flavonoid Metabolite with Potent Antiplatelet Effects.

SCOPE: Intake of flavonoids from the diet can be substantial, and epidemiological studies suggest that these compounds can decrease the incidence of cardiovascular diseases by involvement with increased platelet aggregation. Although parent flavonoids possess antiplatelet effects, the clinical importance is disputable due to their very low bioavailability. Most of them are metabolized by human colon bacteria to smaller phenolic compounds, which reach higher plasma concentrations than the parent flavonoids. In this study, a series of 29 known flavonoid metabolites is tested for antiplatelet potential. METHODS AND RESULTS: Four compounds appear to have a biologically relevant antiplatelet effect using whole human blood. 4-Methylcatechol (4-MC) is clearly the most efficient being about 10× times more active than clinically used acetylsalicylic acid. This ex vivo effect is also confirmed using a potentially novel in-vivo-like ex ovo hen's egg model of thrombosis, where 4-MC significantly increases the survival of the eggs. The mechanism of action is studied and it seems that it is mainly based on the influence on intracellular calcium signaling. CONCLUSION: This study shows that some flavonoid metabolites formed by human microflora have a strong antiplatelet effect. This information can help to explain the antiplatelet potential of orally given flavonoids.

Simulation of the long-term fate of superparamagnetic iron oxide-based nanoparticles using simulated biological fluids.

Aim: To simulate the stability and degradation of superparamagnetic iron oxide nanoparticles (MNP) in vitro as part of their life cycle using complex simulated biological fluids. Materials & methods: A set of 13 MNP with different polymeric or inorganic shell materials was synthesized and characterized regarding stability and degradation of core and shell in simulated biological fluids. Results: All MNP formulations showed excellent stability during storage and in simulated body fluid. In endosomal/lysosomal media the degradation behavior depended on shell characteristics (e.g., charge, acid-base character) and temperature enabling the development of an accelerated stress test protocol. Conclusion: Kinetics of transformations depending on the MNP type could be established to define structure-activity relationships as prediction model for rational particle design.

Improving colloidal stability of silica nanoparticles when stored in responsive gel: application and toxicity study.

When silica nanoparticles (SiNP) are stored in aqueous solution, even for few hours, they have a tendency to form agglomerates and therefore adapt inhomogeneous structures. Here we present a very practical method to store SiNP in responsive hydrogel. We have confirmed that SiNP kept in the responsive hydrogel do not undergo through undesirable morphological changes and while in storage they maintain their excellent colloidal stability. The effect of SiNP hollowing (i.e. dissolution of the core of the particles that leaves empty cavity inside) was significantly inhibited in the hydrogel, which is a critical feature for any nano-medical applications (e.g. controlled drug release). To demonstrate the applicability of the hydrogel-storing concept within a biologically relevant context, in this work we have evaluated the toxicological effects of the responsive SiNP-gel formulation in a model in vitro (human cell line U87GM and hemocompatibility using red blood cells) and ex ovo (hen's egg test) experiments. Particles stored in the gel as well as the pure gel did not affect the hemocompatibility (hemolysis and erythrocyte aggregation) up to a concentration of 100 µg/mL. Furthermore, systemic injections into the blood circulation of the chick area vasculosa confirmed the biocompatibility in a more complex biological environment. All evaluated toxicological values (hemorrhage, thrombosis, vascular lysis, and lethality) were comparable with the negative control, and no differences in toxicological response could be observed between the SiNP stored in hydrogel and the control nanoparticles stored in the solution.

Luminomagnetic Eu3+- and Dy3+-doped hydroxyapatite for multimodal imaging.

Multimodal imaging has recently attracted much attention due to the advantageous combination of different imaging modalities, like photoluminescence (PL) and magnetic resonance imaging (MRI). In the present study, luminescent and magnetic hydroxyapatites (HAp) were prepared via doping with europium (Eu3+) and dysprosium (Dy3+), respectively. Co-doping of Eu3+ and Dy3+ was used to combine the desired physical properties. Both lanthanide ions were successfully incorporated in the HAp crystal lattice, where they preferentially occupied calcium(I) sites. While Eu-doped HAp (Eu:HAp) exhibits dopant concentration dependent persistent PL properties, Dy-doped HAp (Dy:HAp) shows paramagnetic behavior due to the high magnetic moment of Dy3+. Co-doped HAp (Eu:Dy:HAp) nanoparticles combine both properties in one single crystal. Remarkably, multimodal co-doped HAp features enhanced PL properties due to an energy transfer from Dy3+ sensitizer to Eu3+ activator ions. Eu:Dy:HAp exhibits strong transverse relaxation effects with a maximum transverse relaxivity of 83.3L/(mmol·s). Due to their tunable PL, magnetic properties and cytocompatibility Eu:-, Dy:- and Eu:Dy:HAp represent promising biocompatible ceramic materials for luminescence imaging that simultaneously may serve as a contrast agent for MRI in permanent implants or functional coatings.

Evaluation of Homobivalent Carbolines as Designed Multiple Ligands for the Treatment of Neurodegenerative Disorders.

Neurodegenerative diseases represent a challenge for biomedical research due to their high prevalence and lack of mechanism-based treatments. Because of the complex pathology of neurodegenerative disorders, multifunctional drugs have been increasingly recognized as potential treatments. We identified homobivalent γ-carbolinium salts as potent inihitors of both cholinesterases, N-methyl-D-aspartate receptors, and monoamine oxidases. Homobivalent γ-carbolines displayed similar structure-activity relationships on all tested targets and may present promising designed multiple ligands for the treatment of neurodegenerative disorders.