Effects of Silver Nanoparticles on Primary Mixed Neural Cell Cultures: Uptake, Oxidative Stress and Acute Calcium Responses

In the body, nanoparticles can be systemically distributed and then may affect secondary target organs, such as the central nervous system (CNS). Putative adverse effects on the CNS are rarely investigated to date. Here, we used a mixed primary cell model consisting mainly of neurons and astrocytes and a minor proportion of oligodendrocytes to analyze the effects of well-characterized 20 and 40 nm silver nanoparticles (SNP). Similar gold nanoparticles served as control and proved inert for all endpoints tested. SNP induced a strong size-dependent cytotoxicity. Additionally, in the low concentration range (up to 10 μg/ml of SNP), the further differentiated cultures were more sensitive to SNP treatment. For detailed studies, we used low/medium dose concentrations (up to 20 μg/ml) and found strong oxidative stress responses. Reactive oxygen species (ROS) were detected along with the formation of protein carbonyls and the induction of heme oxygenase-1. We observed an acute calcium response, which clearly preceded oxidative stress responses. ROS formation was reduced by antioxidants, whereas the calcium response could not be alleviated by antioxidants. Finally, we looked into the responses of neurons and astrocytes separately. Astrocytes were much more vulnerable to SNP treatment compared with neurons. Consistently, SNP were mainly taken up by astrocytes and not by neurons. Immunofluorescence studies of mixed cell cultures indicated stronger effects on astrocyte morphology. Altogether, we can demonstrate strong effects of SNP associated with calcium dysregulation and ROS formation in primary neural cells, which were detectable already at moderate dosage

Effects of Silver Nanoparticles on Primary Mixed Neural Cell Cultures: Uptake, Oxidative Stress and Acute Calcium Responses

In the body, nanoparticles can be systemically distributed and then may affect secondary target organs, such as the central nervous system (CNS). Putative adverse effects on the CNS are rarely investigated to date. Here, we used a mixed primary cell model consisting mainly of neurons and astrocytes and a minor proportion of oligodendrocytes to analyze the effects of well-characterized 20 and 40 nm silver nanoparticles (SNP). Similar gold nanoparticles served as control and proved inert for all endpoints tested. SNP induced a strong size-dependent cytotoxicity. Additionally, in the low concentration range (up to 10 μg/ml of SNP), the further differentiated cultures were more sensitive to SNP treatment. For detailed studies, we used low/medium dose concentrations (up to 20 μg/ml) and found strong oxidative stress responses. Reactive oxygen species (ROS) were detected along with the formation of protein carbonyls and the induction of heme oxygenase-1. We observed an acute calcium response, which clearly preceded oxidative stress responses. ROS formation was reduced by antioxidants, whereas the calcium response could not be alleviated by antioxidants. Finally, we looked into the responses of neurons and astrocytes separately. Astrocytes were much more vulnerable to SNP treatment compared with neurons. Consistently, SNP were mainly taken up by astrocytes and not by neurons. Immunofluorescence studies of mixed cell cultures indicated stronger effects on astrocyte morphology. Altogether, we can demonstrate strong effects of SNP associated with calcium dysregulation and ROS formation in primary neural cells, which were detectable already at moderate dosages

"Unus pro omnibus, omnes pro uno" : using single amino acids as templates for biomineralization, and small self assembling peptides for the preparation of metal oxides, organization of metal nanoparticles and creation of new porous materials

Introduction General concepts involved in the scope of this PhD Thesis are briefly presented. Part I: Bioinspired iron oxide mineralization Using single amino acids may be thought an over-simplification of larger proteins or peptides. However, their use as model system already enables the understanding of some crystalline phase selection processes. Some general rules about iron oxide biomineralization in the presence of amino acids and thus, as an extension, in the presence of proteins are drawn out of this study. Part II: Small self assembling peptides and the transcription of their chiral information into inorganic materials Small self assembling peptides can be tuned to self assemble in organogels. The 3D organogel self-organization scheme can be transcribed into inorganic materials using processes involving metal alkoxide (sol-gel) technologies. The peptide synthesis and the selfassembling motives, material synthesis (silica and anatase based materials) and characterization are described in this part. Part III: Using organogels to synthetize nanoparticles and to orient them on a peptide fiber Organogels prepared from two chemically and structurally similar peptides can be mixed to prepare a homogenous 3D network which will present on its surface complexing properties depending on the structure of the peptides chosen. This scaffold could be used to organize nanoparticles or to prepare silver-based nanostructures. Peptides involved, their self assembling schemes, the structures created and rationalization of this approach will be presented in this part. Part IV: Using small self assembling peptides to create new porous materials The preparation of metal-organic frameworks using a slightly modified version of the model peptide which was used througout the PhD Thesis is possible. We present here the synthesis and spectroscopic and crystallographic characterization of the materials obtained. Conclusions In this section the achievements realized during the PhD will be discussed. Some new tracks to further exploit these systems will also be introduced

Silver nanoparticle engineering via oligovaline organogels

L-Valine-based oligopeptides with the chemical structure Z–(L-Val)₃–OMe and Z–(L-Val)₂–L-Cys(S-Bzl)–OMe form stable organogels in butanol. Both peptides are efficient gelators, but Z–(L-Val)₂–L-Cys(S-Bzl)–OMe crystallizes more readily than Z–(L-Val)₃–OMe. The two peptides can form mixed fibers, which also gel butanol. The resulting organogels are very similar to oligovaline organogels reported earlier (Mantion and Taubert, Macromol. Biosci., 2007, 7, 208) as they also form highly ordered peptide fibers with a predominant β-sheet structure and diameters of ca. 100 nm. The fibers can be mineralized with silver nanoparticles using DMF as a reducing agent. The fraction of the sulfur-containing peptide Z–(L-Val)₂–L-Cys(S-Bzl)–OMe controls the shape and size of the resulting nanoparticles. At high Z–(L-Val)₂–L-Cys(S-Bzl)–OMe content, small spherical particles are distributed all over the fiber. Lower contents of Z–(L-Val)₂–L-Cys(S-Bzl)–OMe lead to a size increase of the particles and to more complex shapes like plate-like and raspberry-like silver particles. The interactions between peptide and silver ions or silver particles takes place via a complexation of the silver ions to the sulfur atom of the thioether moiety, and are shown to be the key interaction in controlling particle formation

Glycopolymer vesicles with an asymmetric membrane

Direct dissolution of glycosylated polybutadiene–poly(ethylene oxide) block copolymers can lead to the spontaneous formation of vesicles or membranes, which on the outside are coated with glucose and on the inside with poly(ethylene oxide)

Effect of Chrysin and Natural Coumarins on UGT1A1 and 1A6 Activities in Rat and Human Hepatocytes in Primary Culture

International audienc

Amino acids in iron oxide mineralization: (incomplete) crystal phase selection is achieved even with single amino acids

Iron oxides are important minerals in biology and materials science. Using biomimetic synthesis, a variety of iron oxides have been fabricated. However, it is still not clear how growth modifiers like amino acids and peptides select different crystal phases of a complex material like iron oxide. The current paper shows that already with single amino acids, (incomplete) crystal phase selection is achieved in vitro. In particular, L-histidine, L-threonine, and L-cysteine favor the formation of unstable crystal phases like ferrihydrite or lepidocrocite, although sometimes only at high amino acid concentrations. Other amino acids like L-valine have only minor effects when compared to control samples grown in the absence of amino acids. The effects of the amino acids can be rationalized via kinetic trapping and different interaction strengths of the amino acids with the growing iron oxide particles. The effects of the amino acids on the particle morphologies are less significant. The paper therefore shows that single amino acids can be a valuable tool for the materials chemist to fabricate and stabilize even unstable iron oxide crystal phases

Silsesquioxane/Polyamine Nanoparticle-Templated Formation of Star- Or Raspberry-Like Silica Nanoparticles

Silica is an important mineral in biology and technology, and many protocols have been developed for the synthesis of complex silica architectures. The current report shows that silsesquioxane nanoparticles carrying polymer arms on their surface are efficient templates for the fabrication of silica particles with a star- or raspberry-like morphology. The shape of the resulting particles depends on the chemistry of the polymer arms. With poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) arms, spherical particles with a less electron dense core form. With poly [2-(methacryloyloxy)ethyl] trimethylammonium iodide (PMETAI), star- or raspberry-like particles form. Electron microscopy, electron tomography, and small-angle X-ray scattering show that the resulting silica particles have a complex structure, where a silsequioxane nanoparticle carrying the polymer arms is in the center. Next is a region that is polymer-rich. The outermost region of the particle is a silica layer, where the outer parts of the polymer arms are embedded. Time-resolved zeta-potential and pH measurements, dynamic light scattering, and electron microscopy reveal that silica formation proceeds differently if PDMAEMA is exchanged for PMETAI