Role Of Surface Modification Research Articles

Role of surface modification on physicochemical properties of luminescent YPO4:Tb nanorods

Highly crystalline, luminescent YPO4:Tb (core), YPO4:Tb@LaPO4 (core/shell) nanorods (NRs) were prepared by urea based co-precipitation process at low temperature. The synthesis method involves important advantages such as its simplicity, low-cost precursor, eco-friendly, rapidness and high reaction yields. X-ray diffraction, transmission electron microscopy, energy dispersive-x-ray analysis, FTIR, UV/vis, excitation and emission spectral techniques were employed to investigate the crystals structure, crystallinity, morphology, surface chemistry, optical and photoluminescence properties of the as-prepared samples. The silica surface coating was verified from EDX and FTIR spectral studies. TEM micrograph indicates the well crystalline, irregular size rod-shaped nanostructures, which were covered with a porous thin silica layer. The emission spectra were dominated by a 5D4→7F5 transition in all three samples, but the core/shell nanostructured shows strongest emission intensity because of reduction in nonradiative transition rate. Silica-modified core/shell/Si NRs exhibits high solubility with good colloidal stability in respect to core/shell NRs due to the influence of optically active silica. The morphological, nanostructural, high solubility in an aqueous solvent along with strong green photoluminescence makes them a suitable candidate for biomedical applications.

Photochemical studies of monodispersed YPO 4 :Eu microspheres: The role of surface modification on structural and luminescence properties

Abstract Well-aqueous soluble, monodispersed, luminescent YPO 4 :Eu (core), YPO 4 :Eu@LaPO 4 (core/shell) and YPO 4 :Eu@LaPO 4 @SiO 2 (core/shell/Si) microspheres (MSs) were fabricated at low temperature with a facile synthesis process. TEM micrographs demonstrate the monodispersed, spherical shaped MSs were effectively covered with rough, porous silica surface, which is average grain size around 223 nm. Energy dispersive X-ray analysis and FTIR spectral studies verified the silica surface modification. High absorbance of silica modified core/shell/Si MSs in the ultraviolet region suggests the good solubility and colloidal stability in an aqueous environment. Photoluminescence intensity of the electric-dipole ( 5 D 0 → 7 F 2 ) transition was dramatically decreased and magnetic-dipole ( 5 D 0 → 7 F 1 ) transition was increased in core/shell MSs regardless core MSs, it could be due to the formation of the undoped LaPO 4 shell surrounding the luminescent seed core-MSs. The formation of silica layer over the core/shell MSs not only increase the particle size but also improve the solubility character, however silica layer greatly quenched the luminescence intensity because of enhancement in multiphonon relaxation rate. Our finding suggests that monodispersed, spherical shaped luminescent MSs could be suitable materials for future use in photonic based bioapplications.

Role of surface modification of SiO2 with bio-safe citric acid on the morphological and thermal properties of nanocomposites based on N-trimellitylimido-l-methionine diacid and 4,4′-diaminodiphenyl ether: using ultrasound irradiation and ionic liquid

In this work, the surface of SiO2 NPs was modified with citric acid (CA) to prevent agglomeration of SiO2 nanoparticles (NP)s in the poly(amide-imide) (PAI) matrix. The PAI was synthesized from polymerization reaction of N-trimellitylimido-l-methionine with 4,4′-diaminodiphenyl ether using molten tetra-n-butylammonium bromide and triphenyl phosphite. PAI–SiO2/CA nanocomposites (PSCN)s were prepared via a fast ultrasonic irradiation process. The PSCNs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis.

β-Cristobalite (001) surface as 4-formaminoantipyrine adsorbent: First principle study of the effect on adsorption of surface modification

Silica based materials find applications as excipients and particularly as drug delivery agents for pharmaceutical drugs. Their performance can be crucially affected by surface treatments, as it can modify the adsorption (and release) of these formulations. The role of surface modification on the features of 4-formaminoantipyrine (FAA) adsorbed on β-cristobalite (001) surface is studied by means of simulations based on the Density Functional Theory (DFT). Starting from the results of FAA in interaction with a dehydroxylated surface; a fully hydroxylated surface and a functionalized surface with benzalkonium chloride (BC) surfactant have been added to study the configurational landscape. Calculations suggest that the trend for FAA preferential adsorption on silica surfaces is: dehydroxylated>hydroxylated>BC-functionalized. The potential for hydrogen bonding causes the main contribution to the bonding while dispersion forces present an additional contribution independently of whether the drug is hydrogen-bonded or BC-bonded to the surface. Adsorption takes mainly place through nitrogen atoms in the heterocyclic ring, the carbonyl and amine functional groups. Associated mode’s shifts and concurrent changes in bond length are also observed showing accordance between electronic and geometrical structure results. BC surfactant reduces the number of formed H-bonds and lowers the attractive molecule-surface interaction being it useful to prevent particle agglomeration and could favor drug release in therapies that requires faster but controlled delivery.

Rheology of fibrillated cellulose suspensions after surface modification by organic nanoparticle deposits

The role of surface modification on rheological properties of fibrillated cellulose suspensions has been evaluated under creep, oscillatory, and rotational testing conditions. Two types of fibrillated cellulose were produced by mechanical homogenization, followed by the deposition of poly(styrene-co-maleimide) or SMI nanoparticles containing encapsulated palm oil on the fibril surfaces. During static creep testing, the modified fibrils changed into fully viscous properties, while native fibrils showed viscoelastic behavior at low stresses. A lower viscosity and reduction in hysteresis effects were experienced during steady-state rotational flow testing, together with a reduction in yield stress after modification. A study of viscoelastic properties by oscillatory testing illustrated that the cross-over point between storage and loss moduli was shifted towards lower strains by surface modification as an indication for the enhancement of liquid-like properties observed for SMI/oil nanoparticle dispersions, while the transition point was hardly affected by fibrillation. The variations in rheological properties were overruled by surface modification and reduction in hydrogen bonding interactions of modified fibrillated cellulose, whereas rheological properties of a physical mixture of native fibrillated cellulose suspension and nanoparticle dispersion remained dominated by the fibrillated cellulose.

Improved Performance for Lithium Rich Layered Oxides Via High Throughput Technologies

The design of high voltage and high capacity cathode materials for lithium ion batteries is important for the pressing demands of both electric vehicles and portable devices. Lithium excess layered oxides, where the lithium-to-transition metal ratio is greater than 1, have been widely explored due to the possibility of utilizing more than 1 lithium in the chemical formula unit to significantly increase the capacity. Despite much research, commercial application of the lithium excess material has been impeded due to low initial coulombic efficiency, poor cycle life, voltage fade, and poor rate performance. These deficiencies have mainly been attributed to the complicated structural evolution and the formation of a cathode solid electrolyte interface (SEI) layer at higher voltages (>4.5V). Therefore, the role of surface modification on improving the electrochemical properties has been investigated by Wildcat. The use of chemical treatments and post-annealing steps to induce the formation of a surface spinel structure prior to electrochemical cycling can improve the first cycle coulombic efficiency and rate performance. However, further improvements in the first cycle coulombic efficiency and cycle life of these materials are still required. This work investigates several families of surface coatings and compositional dopants in lithium rich layered oxides. Modification of the surface coating and addition of dopants can greatly enhance the first cycle coulombic efficiency while also maintaining or improving cycle stability, voltage fade, and rate performance of the lithium excess material. Wildcat evaluation of the performance of hundreds of surface coatings and dopants shows that certain families tend to improve all metrics. In addition we have demonstrated that certain families, such as metal phosphate and metal fluoride coatings, reduce gas generation during the first cycle as well as subsequent cycles relative to the pristine lithium excess material.

The role of surface functionalization on the pulmonary inflammogenicity and translocation into mediastinal lymph nodes of graphene nanoplatelets in rats.

Graphene, a two-dimensional monocrystalline layer of carbon atoms, has potential in many applications not only in material sciences, but also in the biomedical fields, but there is little information about the role of surface modification on the toxicity of graphene-based nanomaterials. Here, we evaluated the role of surface functionalization of the graphene nanoplatelets (GNPs) on the pulmonary inflammogenicity and translocation into mediastinal lymph nodes using a rat intratracheal instillation model. Six types of GNPs were used: All types of GNPs were based on the pristine GNPs (GNPdot), and different functional groups were conjugated onto them including a COOH (GNPCOOH), COH [Formula: see text], N-H [Formula: see text], F x (GNPF), and N=H [Formula: see text]. All types of GNPs showed very high potential for the generation of reactive oxygen species (ROS) in a dose-dependent manner when measured by a 2'7'-dichlorofluorescin diacetate assay. GNPs were instilled into the lungs of rats at 0.3 and 1mg/rat for the evaluation of acute (24h) inflammation and at 3mg/rat for chronic (1 and 4weeks) inflammation. At 24h after instillation, all types of GNPs showed good dose-dependent increases in polymorphonuclear leukocytes with a clear dose-dependency although significant increases compared to vehicle control were found only in positively charged GNPs [Formula: see text]. While the acute inflammation in all treatment groups was returned to control levels at 1 and 4weeks after instillation, GNPs showed similar patterns of translocation into the mediastinal lymph nodes with a higher degree over time. This study implies that the main factors of GNPs for producing lung inflammation are the potential for ROS generation and surface charge. In addition, functional groups on the GNPs might not play an important role in the extrapulmonary translocation into the mediastinal lymph nodes.

Nanosuspensions as delivery system for gambogenic acid: characterization and in vitro/in vivo evaluation

Nanosuspensions (NS) can enhance the saturation solubility and dissolution velocity of poorly soluble drugs. PEG as a non-ionic surfactant plays an important role in surface modification of nanoparticles for prolonging in vivo circulation. In this study, anti-solvent precipitation method was introduced to prepare gambogenic acid nanosuspensions (GNA-NS) with PVPK30 and PEG2000 as stabilizers to settle the disadvantages of GNA. The obtained nanoparticles were spherical with a mean particle size of 183.7 nm and a zeta potential of −22.8 mV. The entrapment efficiency and drug loading of the resultant formulation were 97.3 and 29.73%. X-ray diffraction analysis confirmed the amorphous phase of GNA in NS. Fourier transform infrared indicated there may be hydrogen bond interaction between the drug and excipients. After lyophilization of GNA-NS, the freeze-dried powder displayed sufficient long-term physical stability at 4 and 25 °C. In comparison to GNA solution, in vitro studies of GNA-NS showed much slower release and higher cytotoxicity in HepG2 cells. What’s more, the pharmacokinetic study in rats revealed that the AUC0–∞ and t1/2 of GNA-NS were increased 2.63- and 1.77-fold than that of the reference formulation. Taken together, in vitro/in vivo evaluations showed NS would be an effectively strategy to change the poor aqueous solubility and prolong the half-life for GNA. The GNA-NS with enhanced bioavailability and drug efficacy provided a promising delivery system for the application of GNA.

Surface modifications induced by high fluxes of low energy helium ions.

Several metal surfaces, such as titanium, aluminum and copper, were exposed to high fluxes (in the range of 1023 m−2s−1) of low energy (<100 eV) Helium (He) ions. The surfaces were analyzed by scanning electron microscopy and to get a better understanding on morphology changes both top view and cross sectional images were taken. Different surface modifications, such as voids and nano pillars, are observed on these metals. The differences and similarities in the development of surface morphologies are discussed in terms of the material properties and compared with the results of similar experimental studies. The results show that He ions induced void growth and physical sputtering play a significant role in surface modification using high fluxes of low energy He ions.

Role of surface modification and mechanical orientation on property enhancement of cellulose nanocrystals/polymer nanocomposites

Cellulose nanocrystals (CNCs), surface-modified by grafting long alkyl chain amine onto carboxylated CNCs, have been applied as novel nanofillers to prepare nanocomposite films of poly(ethylene-co-vinylacetate) (EVA) through solution casting technique. The robust amide linkages imparted hydrophobicity to the nanocrystal surface and allowed for a better dispersion of CNCs within the EVA matrix. Atomic force microscopy (AFM) surface images and polarized optical micrographs showed that the nanocrystals were randomly oriented in the plane of the EVA film. To achieve the alignment of anisotropic nanofillers, we carried out mechanical shear experiments at an elevated temperature well above the glass-transition temperature of matrix polymer. Hot-pressing and hot-stretching resulted in preferential reorientation of nanocrystals, but not along the shear direction, which is related to the combined actions between the external tension and intermolecular interaction of amide-modified CNC during shear processing. As a result, external mechanical stress transferred from the matrix to the particles, leading to a preferential orientation of the latter. Mechanical and water vapor barrier properties were found to be drastically enhanced. The amide-based CNC/EVA showed high level of elongation at break (up to 85% retention of the initial values). These enhancements were tentatively attributed to the strong interaction occurring at the interface between CNC amide and the EVA polymer.

Microchemical and structural evidence for space weathering in soils from asteroid Itokawa

Here we report microchemical and microstructural features indicative of space weathering in a particle returned from the surface of asteroid Itokawa by the Hayabusa mission. Space weathering features include partially and completely amorphous rims, chemically and structurally heterogeneous multilayer rims, amorphous surface islands, vesiculated rim textures, and nanophase iron particles. Solar-wind irradiation is likely responsible for the amorphization as well as the associated vesiculation of grain rims. The multilayer rims contain a nanocrystalline outer layer that is underlain by an amorphous inner layer, and both have compositions that are distinct from the underlying, crystalline orthopyroxene grain. The multilayer rim features could be derived from either radiation-induced sputter deposition or vapor deposition from micrometeorite impact events. The amorphous islands on grain surfaces have a distinctive morphology and composition suggesting that they represent surface deposits of melt derived from micrometeorite impact events. These observations indicate that both irradiation damage and micrometeorite impacts play a role in surface modification and space weathering on asteroid Itokawa.

Role of surface modification in zinc oxide nanoparticles and its toxicity assessment toward human dermal fibroblast cells.

The wide-scale applications of zinc oxide (ZnO) nanoparticles (NPs) in photocatalysts, gas sensors, and cosmetics may cause toxicity to humans and environments. Therefore, the aim of the present study was to reduce the toxicity of ZnO NPs by coating them with a silica (SiO2) layer, which could be used in human applications, such as cosmetic preparations. The sol–gel method was used to synthesize core ZnO with SiO2-shelled NPs (SiO2/ZnO NPs) with varying degrees of coating. Diverse studies were performed to analyze the toxicity of NPs against cells in a dose- and time-dependent manner. To ensure the decreased toxicity of the produced SiO2/ZnO NPs, cytotoxicity in membrane damage and/or intracellular reactive oxygen species (ROS) were assessed by employing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, lactate dehydrogenase, 2′,7′-dichlorofluorescin, and lipid peroxide estimations. The cores of ZnO NPs exhibited cytotoxicity over time, regardless of shell thickness. Nevertheless, the thicker SiO2/ZnO NPs revealed reduced enzyme leakage, decreased peroxide production, and less oxidative stress than their bare ZnO NPs or thinner SiO2/ZnO NPs. Therefore, thicker SiO2/ZnO NPs moderated the toxicity of ZnO NPs by restricting free radical formation and the release of zinc ions, and decreasing surface contact with cells.

Investigating role of sulphur specific carbon adsorbents in deep desulphurization

Adsorptive desulphurization of model fuel (thiophene in isooctane) was studied by using sulphur specific carbon based adsorbents, SHIRASAGI GH2x 4/6 and SRCx 4/6, in an attempt to obtain insight into the adsorptive behaviour of sulphur moiety on the modified surfaces. Both adsorption equilibria and adsorption kinetics have been reported. Characterization of the modified adsorbents was carried out using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction (XRD) and surface area analyser. Adsorption experiments along with characterization results highlight potential for higher sulphur adsorption on the modified adsorbents. Substantially higher capacities for adsorption of thiophene were obtained, ∼5.5 and ∼20mgg−1 of sulphur for SHIRASAGI GH2x 4/6 and SRCx 4/6 respectively. Experimental investigations reveal possible influence of Al/Si ratio, 12.46 and 9.35 in GH2x and SRCx respectively that can have implication in adsorption behaviour. It was found that surface modification plays important role in enhancing sulphur removal capacity as compared to conventional carbon adsorbents. A plausible mechanism to account for surface interactions and role of surface modification has been proposed. The higher mesopore volume along with higher oxygen content is believed to influence preferential adsorption of thiophenic sulphur by SRCx. The work also indicated specific role of Al and Si content in the carbon matrix. The utility of these adsorbents and higher sulphur removal capacity has also been confirmed using synthetic mixture of refractory sulphur compounds such as benzothiophene, dibenzothiophene along with thiophene.

Microhardness homogeneity analysis of thick amorphous composite coating prepared by TIG cladding

Amorphous coatings play an important role in surface modification owing to their inherent properties of high strength and abrasion resistance. A ∼4 mm thick layer of Fe based amorphous composite coating was deposited on the surface of a boiler waterwall tube by tungsten inert gas cladding. Microstructure analysis demonstrated that the coating consisted of amorphous and nanocrystallised phases. The longitudinal and transverse microhardness measurements were evaluated systematically by Vickers. The results showed that the microhardness up to 1400 HV0·3 varied under different loads and the more obvious microhardness fluctuations were observed under smaller loads. On the basis of the Hall–Petch rule, the uneven distribution of amorphous and nanocrystalline phases in the small indentation area may be responsible for the microhardness fluctuations. A careful study was undertaken of the reason for the high hardness of the coating and the microhardness fluctuation phenomenon, which may lay solid foundations for achieving a nearly three-dimensional homogeneity in the amorphous composite coating, with a large thickness.

Direct Carbon Fuel Cells - Wetting Behavior of Carbon in Molten Carbonate

The Direct Carbon Fuel Cell (DCFC), which uses solid carbon as fuel and molten carbonate as electrolyte, has had resurgence of interest due to very high electrochemical conversion efficiency, nearly 100%, no requirement of fuel reforming, and potential for CO2capture and sequestration. At the cathode, carbon dioxide is converted into carbonate ions. The main reaction at the anode is generation of carbon dioxide from carbon and carbonate, the net cell reaction being oxidation of carbon to carbon dioxide. Additional reactions that may be occur at the anode are a two-electron reaction resulting in co-generation of carbon dioxide and carbon monoxide and the Boudouard reaction leading to conversion of carbon and carbon dioxide to carbon monoxide, the so-called “carbon corrosion”. The performance of DCFC can be appreciably limited by this reaction. The reverse Boudouard reaction has not been studied in solid-melt-gas systems. It is important to study this reaction in conjunction with wetting behavior of carbon in molten carbonate.With this in mind, the wetting behavior of carbon electrode in molten carbonate, comprised of a Li-K eutectic mixture, was studied in this study at different temperatures. The wetting behavior is complicated due to reactions occurring at the carbon surface before or after the start of wetting. Before wetting, carbon rods were exposed to a gas atmosphere with varying partial pressures of carbon dioxide to examine the extent of Boudouard reaction and the resulting structural changes in carbon rods. This reaction modifies the lateral surface of carbon electrode due to carbon corrosion, which leads to reduction in interfacial tension between solid carbon and molten carbonate after dipping carbon rods in molten carbonate.Wetting behavior of carbon rods was studied for a period of 24 hours. The effects of temperature and pre-exposure to varying levels of carbon dioxide on speed of formation of liquid (molten carbonate) meniscus, propagation of liquid film thereafter, and the ultimate length of liquid film were studied. During the wetting process, bubble evolution occurred at the surface of carbon electrode not only below the meniscus, but also above the meniscus. This indicates that wetting of carbon electrode in molten carbonate is influenced not only by capillary forces but also by the reverse Boudouard reaction. The reverse Boudouard reaction is promoted at higher temperature, leading to changes to greater extent in the surface structure and therefore solid-liquid and solid-vapor interfacial tensions.The lateral surfaces of graphite rods before wetting and after wetting, liquid films formed on the graphite rods, and cross-sections of cylindrical carbon rods above and below the meniscus were analyzed using SEM. The liquid films and circular cross-sections of carbon rods were also analyzed using energy-dispersive X-ray spectroscopy (EDX) and distributions and variations in oxygen and potassium were examined. Oxide ions are generated prior to and during wetting of carbon rods and play an important role in surface modification of these prior to and during wetting.A reaction mechanism based on the experimental observations is proposed. The roles of Boudouard reaction, including equilibrium characteristics, and oxide ions on surface modification of carbon rods before and after wetting and the implications thereof on wetting behavior of carbon rods are explained satisfactorily by the reaction mechanism.

Comparison of cytotoxic and inflammatory responses of pristine and functionalized multi-walled carbon nanotubes in RAW 264.7 mouse macrophages

The increased application of carbon nanotubes (CNTs) has raised the level of public concern regarding possible toxicities. Using in vitro cellular assays, we were able to assess the immunotoxicity of pristine multi-wall carbon nanotubes (MWCNTs) and their derivatives, covalently functionalized with carboxyl (COOH) or polyethylene glycol (PEG), in rodent macrophage cells. Moreover, special focus was placed on the role of surface modification and nanotubes aggregation on toxicity. Results showed that pristine MWCNTs reduce cell viability compared with functionalized MWCNTs in RAW 264.7 macrophages when incubated at concentrations of 25, 50, 100, 200, 400, and 800μg/mL. However, in addition to causing cytotoxicity, functionalized MWCNTs induce serious inflammatory responses, as indicated by the production of inflammatory cytokines including TNF-α, IL-1β and IL-6 at various MWCNTs concentrations (25, 50, 100, and 200μg/mL). Particle surface modification and dispersion status in biological medium were key factors in determining cytotoxicity. These findings imply that MWCNTs-induced inflammatory responses in macrophages may be associated with surface modification and aggregation of MWCNTs, which is reflected by alteration of inflammatory cytokine expression.

Role of Surface Modifications in Ovalbumin Interacting with Lipid Membranes

Recent electrophysiology studies in our laboratory suggest that some proteins from the Serine Protease Inhibitor (SERPIN) family cross cell membranes without regulated uptake mechanisms. Since these proteins do not structurally resemble typical membrane proteins, questions arise about the factors governing interactions between lipid and protein of this family. Previous studies of ovalbumin_a chicken protein of the SERPIN family_indicate that both glycosylation and phosphorylation play vital regulatory roles. Combining UV-visible and phosphorus NMR spectroscopy offers information on these posttranslational modifications. Proteins crossing the cell membrane must enter the central region of lipid tails. This hydrophobic environment causes the proteins to change conformation and altering the absorbance and resonance spectra. In UV-spectroscopy, environmental hydrophobicity cause phenylalanine, tyrosine, and tryptophan peaks to shift. In P31 NMR, the hydrophobic interactions lead to changes in phosphorus chemical shifts. Combining information from both these methods reveals the interactions of phosphorylated glycoproteins and lipid bilayers.

A special issue on nanotoxicology

It is a great pleasure to introduce this special issue on nanotoxicology. This novel discipline of toxicology addresses potential adverse effects of manufactured nanomaterials in biological systems. As the number of manufactured nanomaterials is ever growing, a huge variety of materials needs to be tested for safety now and in the future. Therefore, toxicological research in this area is of utmost importance and reemphasizes the relevance of toxicology in general. The attractiveness of nanotoxicology for researchers lies in all the basic research questions immanent to a young and emerging area in science. As is in general true for toxicology, nanotoxicology in particular is a highly interdisciplinary field, which brings together scientists from totally different backgrounds such as physics, chemistry, biology, engineering, medicine and toxicology, to name a few. Nanotoxicology is not only relevant to assess the risk of unintended nanomaterial exposure but will also help to support the development of nanomedicine by prevention of side effects of pharmaceutical nanoproducts such as those intended for drug delivery, diagnostics or cancer treatment. The goal of this special issue was to compile the most recent views and work of leading experts in nanotoxicology by a series of timely reviews followed by original research articles. The first review summarizes our knowledge on the toxicity of quantum dots (QDs) with a special interest in the role of surface modifications (Hoshino et al. 2011, this issue). As QDs are superior for labelling biomolecules as well as cells, such as stem and cancer cells, they are promising tools for basic research and nanomedicine, provided that their inherent toxicity is prevented. The advantage of QDs is their traceability and the possibility to quantify their dose, an issue which is a major problem for most other, non-labelled nanomaterials. The next review addresses this very important aspect of labelling nanomaterials with radioisotopes, which hopefully will allow for the proper quantification of nanomaterials in different biological environments and pave the way for the proper dosimetry of nanomaterials (Gibson et al. 2011, this issue). Similarly, the choice of model systems for risk assessment is an ongoing debate. Naturally, in vitro systems are currently explored due to their simplicity, higher throughput and as an alternative to animal experiments. However, whether in vitro models are really predictive for the in vivo situation is discussed in the review by Clift and colleagues (Clift et al. 2010, this issue). The series of reviews is finished by an overview of an even less understood topic in nanotoxicology namely mechanisms (Marano et al. 2010, this issue). The so far known cellular targets and signal transduction pathways affected by nanomaterials are reviewed, and this is certainly just the beginning of a fascinating journey to unravel mechanisms of actions in nanotoxicology. Finally, a series of original research articles conclude this issue. Due to their industrial and potential biomedical relevance, mostly inorganic nanomaterials are studied with the exception of one paper on the toxicity of carbon nanotubes. The first contribution investigates the sizedependent localization and uptake of labelled silica particles (Al-Rawi et al. 2011, this issue) followed by three studies on the cytoand genotoxicity of silver nanoparticles (Foldbjerg et al. 2010, this issue), platinum nanoparticles (Gehrke et al. 2011, this issue) and carbon C. Weiss (&) S. Diabate Karlsruhe Institute of Technology (KIT), Campus North Institute of Toxicology and Genetics, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany e-mail: carsten.weiss@kit.edu

Role of PLLA plasma surface modification in the interaction with human marrow stromal cells

AbstractThe effects of oxygen‐based radio frequency plasma enhanced chemical vapor deposition (rf PECVD) on the surface of poly(L‐lactide) (PLLA) polymers and the influence thereof on protein adsorption and on bone–cell behavior have been studied. Thin films and porous scaffolds based on PLLA polymer were developed, and the role of surface modifications were investigated extensively. PECVD surface treatments were used to alter surface functionality and modulate protein adsorption on the PLLA polymer matrix. In particular, Bovine Serum Albumine fluorescein isothiocyanate (fitc‐BSA) conjugate adsorption on patterned surfaces of treated PLLA was analyzed by fluorescence microscopy. Human marrow stromal cells (MSCs) were cultured on scaffolds and cell adhesion and morphology were assessed using fluorescence microscopy. The results indicated that the PLLA surface became hydrophilic and its roughness increased with the treatment time and it had a dominant influence on the adsorption process of the protein. The outcome of the plasma treatment of various PLLA surfaces has been shown to be the up‐regulator of the cell‐adhesive proteins expression and consequently the improvement of cell adhesion and growth. Oxygen‐treated PLLA promoted higher adhesion and proliferation of the MSCs in comparison to the untreated samples. It can be concluded that following plasma treatment, PLLA samples show enhanced affinity for osteoprogenitor cells. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Organic complementary inverters with polyimide films as the surface modification of dielectrics

The organic complementary metal oxide semiconductor (O-CMOS) inverters were integrated with the p-type pentacene-based transistors and n-type N, N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI–C 8H 17)-based transistors. Polyimide (PI) films were inserted between the active layers and dielectrics as the role of surface modification. The performances of the O-CMOS including the mobility, on/off ratio, subthreshold slope, threshold voltage, gains, delay time, and leakage current suppression were dramatically enhanced when PI layer was introduced. An ideal O-CMOS inverter with the propagation delay time of 52 μs at 1 kHz was achieved for the device with PI modification layer. The detail mechanism for performance improvement was discussed.