Effect of pH on the adsorption and interactions of Bovine Serum Albumin with functionalized silicon nitride surface.

Force-distance curves between atomic force microscopy (AFM) tip (Si3N4 non-functionalized) and bovine serum Albumin (BSA) immobilized on Si3N4 substrates have been performed with the purpose to understand how multiple interactions between the protein and the tip were favored in different pHs (4, 6 and 10). In this work, 100 silicon wafer samples were used to deposit a layer of Si3N4. Protein immobilization consisted of the silanization of the substrates with 3-aminopropyltriethoxysilane (APTES) and crosslinking with glutaraldehyde (GA). All functionalization steps were evaluated by contact angle, X-Ray electron spectroscopy (XPS) and AFM. AFM images showed increase of roughness following functionalization. At pH 4, it was possible to note that small forces (49.1 ±â€¯2.4 pN) were needed to stretch BSA, with a contour length of CL = (30.0 ±â€¯1.1 nm). At pH 6, the force applied was higher (101.5 ±â€¯5.0 pN) with a higher molecule stretch CL = (75.6 ±â€¯3.8 nm) because the pH is close to the BSA isoelectric point where the folding of the protein is favored as surfaces charges are minimized leading to lower attractive intramolecular forces. Young's Modulus were also calculated and the lowest value (265 kPa) was observed at pH 10.

Fast, asymmetric and nonhomogeneous clearance of SiC nanoaerosol assessed by micro-particle-induced x-ray emission.

AIM: To study the biopersistence of a silicon carbide (SiC) nanoaerosol in rat lungs, as time-dependent clearance and spatial distribution. MATERIALS & METHODS: Sprague-Dawley rats were exposed 6 h/day during 5 days to a SiC nanoaerosol at 4.91 mg SiC/l. SiC biopersistence in rat lungs sections was assessed over 28 days by micro-particle-induced x-ray emission (µPIXE) as 2D maps and by particle-induced x-ray emission (PIXE) for whole-lung quantification. 2D maps were analyzed for SiC spatial distribution as skewness and kurtosis. RESULTS: Half-time clearance was 10.9 ± 0.9 days, agreeing with PIXE measurements. Spatial-temporal analysis of SiC indicated decreased symmetry and homogeneity. CONCLUSION: Fast SiC clearance points that current nanoaerosol exposure may not be enough to trigger lung overload. Spatial distribution shows an asymmetric and nonhomogeneous SiC clearance.

In vitro treatment with concentrated growth factors (CGF) and sodium orthosilicate positively affects cell renewal in three different human cell lines.

The aim of this study was to investigate the in vitro effect of Silicon, in the soluble form of sodium orthosilicate, combined and not with the concentrated growth factors (CGF), a platelet-rich preparation, on three different human cell lines of fibroblasts (NHDF), endothelial cells (HUVEC), and osteoblasts (HOBs). Each cell type was treated with sodium orthosilicate at the final concentration of 0.5 mM and 1 mM, CGF, and sodium orthosilicate combined with CGF, for 72 h. At the end of the experimental period, the in vitro effect on cell growth, proliferation, and metabolic activity was evaluated by performing a simple cell count, using an automated cell counter and by evaluating the expression of the intracellular proliferation marker Ki-67, using Fluorescence-activated cell sorting (FACS) analysis. Moreover, the expression of other cell markers and active molecules, such as Collagen type I, Osteopontin, Vascular Endothelial Growth Factor, and endothelial Nitric Oxide Synthase, was evaluated, through immunohistochemistry. Results obtained showed that the combined use of CGF and sodium orthosilicate stimulates cell growth, proliferation, and metabolic activity, suggesting that this treatment could be effective in tissue regeneration.

Peptide engineered microcantilevers for selective chemical force microscopy and monitoring of nanoparticle capture.

Engineered peptides capable of binding to silica have been used to provide contrast in chemical force microscopy and tested for their capacity to selectively capture silica nanoparticles (NPs). Gold coated atomic force microscopy (AFM) microcantilevers with integrated tips and colloidal probes were functionalized with engineered peptides through a thiol group of a terminal cysteine which was linked via a glycine trimer to a 12-mer binding sequence. The functionalized probes demonstrated a significantly increased binding force on silicon oxide areas of a gold-patterned silicon wafer, whereas plain gold probes, and those functionalized with a random permutation of the silica binding peptide motif or an all-histidine sequence displayed similar adhesion forces to gold and silicon oxide. As the functionalized probes also allowed contact mode imaging subsequently to the adhesion mapping, also the associated friction contrast was measured and found to be similar to the adhesion contrast. Furthermore, the adsorption of silica NPs onto planar gold surfaces functionalized in the same manner was observed to be selective. Notably, the surface coverage with silica NPs was found to decrease with increasing pH, implying the importance of electrostatic interactions between the peptide and the NPs. Finally, the adsorption of silica NPs was monitored via the decrease in fundamental resonance frequency of an AFM microcantilever functionalized with silica binding peptides.

Evaluations of the Carcinogenicity of Carbon Nanotubes, Fluoro-Edinite, and Silicon Carbide by the International Agency for Research on Cancer (IARC).

We reported the evaluations of the carcinogenicity of fluoro-edinite, silicon carbide, and carbon nanotubes performed by IARC working group in October 2014. For carbon nanotubes (CNTs), multi-walled carbon nanotube (MWCNT)-7 was classified as Group 2B, and MWCNTs without MWCNT-7 and single-walled carbon nanotubes (SWCNTs) were classified as not classifiable in terms of their carcinogenicity to humans. There is sufficient evidence of carcinogenicity for MWCNT-7 in experimental animals, limited evidence for other MWCNTs, and inadequate evidence for SWCNTs. The mechanic evidence for CNTs was not strong. Fluoro-edinite was classified as carcinogenic to humans (Group 1) on the basis of sufficient evidence of carcinogenicity to humans and experimental animals. Silicon carbide was classified into silicon carbide fibers and whiskers. Silicon carbide fibers were evaluated as possibly carcinogenic to humans (Group 2B) on the basis of limited evidence of carcinogenicity to humans. Silicon carbide whiskers were evaluated as probably carcinogenic to humans (Group 2A) on the basis of sufficient evidence of carcinogenicity to experimental animals and the similarity of their physicochemical properties to those of asbestos in terms of the mechanism of carcinogenicity. We report the process of progression in meeting and discuss how to determine the evidence and the evaluation of the carcinogenicity of the three materials.

Multisite silicon neural probes with integrated silicon nitride waveguides and gratings for optogenetic applications.

Optimal optogenetic perturbation of brain circuit activity often requires light delivery in a precise spatial pattern that cannot be achieved with conventional optical fibers. We demonstrate an implantable silicon-based probe with a compact light delivery system, consisting of silicon nitride waveguides and grating couplers for out-of-plane light emission with high spatial resolution. 473 nm light is coupled into and guided in cm-long waveguide and emitted at the output grating coupler. Using the direct cut-back and out-scattering measurement techniques, the propagation optical loss of the waveguide is measured to be below 3 dB/cm. The grating couplers provide collimated light emission with sufficient irradiance for neural stimulation. Finally, a probe with multisite light delivery with three output grating emitters from a single laser input is demonstrated.

An evaluation of zinc bearing palygorskite inclusion on the growth performance, mineral content, meat quality, and antioxidant status of broilers.

The current study was conducted to investigate the effect of zinc (Zn) bearing palygorskite (ZnPal) inclusion on the growth performance, mineral content, meat quality, and antioxidant status of broilers. A total of 240 one-day-old Arbor Acres broiler chicks were randomly allocated into 5 dietary treatments with 6 replicates of 8 chicks. Broilers in the 5 treatments were fed a basal diet supplemented with 0, 20, 40, 60, and 80 mg/kg Zn diet in the form of ZnPal for 42 d, respectively. Birds exhibited similar average daily gain (ADG), average daily feed intake (ADFI), and feed/gain ratio (F:G) among groups during the 42-day study (P>0.05). ZnPal supplementation linearly increased iron (Fe) (P=0.031) and magnesium (Mg) (P=0.002) content in the pectoralis major muscle. Similarly, the inclusion of ZnPal tended to increase Zn content in the thigh (P=0.072) and linearly increase Zn content in the pectoralis major muscle (P=0.055). The concentration of copper (Cu) in the thigh was linearly decreased by ZnPal inclusion (P=0.011). Meanwhile, a quadratic trend for reduced Cu content was observed in the pectoralis major muscle (P=0.074) and thigh (P=0.082), respectively. The supplementation of ZnPal linearly reduced cooking loss in the pectoralis major muscle (P=0.013), and linearly (P=0.029) and quadratically (P=0.034) decreased cooking loss in the thigh. Malondialdehyde (MDA) concentration in the thigh was linearly (P=0.020) and quadratically (P=0.017) reduced by ZnPal inclusion. Additionally, ZnPal supplementation tended to linearly enhance total antioxidant capacity (T-AOC) activity of the pectoralis major muscle (P=0.083). The results obtained in the current study indicated that ZnPal inclusion could alter muscular mineral accumulation, improve meat quality, and enhance the muscular antioxidant capacity of broilers, and Zn supplementation in the form of ZnPal at the dosage of 20 mg/kg would be sufficient in improving meat quality and muscular oxidative status.

Synthesis of boronic-acid-functionalized magnetic attapulgite for selective enrichment of nucleosides.

2,4-Difluoro-3-formyl-phenylboronic acid (DFFPBA)-modified magnetic attapulgite (ATP-Fe3O4-NH2-DFFPBA) was synthesized and employed to capture and enrich cis-diol-containing biomolecules. The resulting material exhibited a high saturation magnetization value of 20.71 emu/g, allowing the absorbent to be conveniently magnetically separated. Combining the Fe3O4 nanoparticles with the high specific surface area of attapulgite yielded a material with a high capture capacity (13.78 mg/g) for adenosine. Furthermore, ATP-Fe3O4-NH2-DFFPBA was found to possess remarkable selectivity for adenosine at a low molar ratio of adenosine/2-deoxyadenosine (1:500). The potential applications of this material were explored by using it to extract five nucleosides from urine samples, and the results demonstrate that it can decrease matrix interference and selectively enrich analytes.

In situ probing of intracellular pH by fluorescence from inorganic nanoparticles.

Intracellular pH (pHi) plays a critical role in the physiological processes of cells. Nanoscale sensors based on pH-sensitive fluorescent proteins attached on nanoparticles (NPs) have been designed but inorganic NP-dependent fluorescent nanosensors have not yet been explored. Herein we describe a pH sensitive inorganic semiconductor fluorescent probe based on ultrathin 3C-SiC NPs which can effectively monitor pH in the range of 5.6-7.4 by taking advantage of the linear dependence between the fluorescent intensity ratio of the surface OH(-) and H(+) bonding states to band-to-band recombination and pH. Detection of pHi is demonstrated in living HeLa cells. In particular, pHi measurements during apoptosis confirm the validity and sensitivity of this technique in monitoring real-time changes in the intracellular environment. Toxicity assessment and confocal laser scanning microscopy indicate that the 3C-SiC NPs have low cytotoxicity and are compatible with living cells.

Origin and status of homologous proteins of biomineralization (biosilicification) in the taxonomy of phylogenetic domains.

The taxonomic affiliation (in the systematisation of viruses, and biological domains) of known peptides and proteins of biomineralization (silicateins, silaffins, silacidins and silicase) and their primary structure homologues were analyzed (methods in silico; using Uniprot database). The total number of known peptides and proteins of biosilicification was counted. The data of the quantitative distribution of the detected homologues found in nature are presented. The similarity of the primary structures of silaffins, silacidins, silicateins, silicase, and their homologues was 21-94%, 45-98%, 39-50%, and 28-40%, respectively. These homologues are found in many organisms, from the Protista to the higher plants and animals, including humans, as well as in bacteria and extracellular agents, and they perform a variety of biological functions, such as biologically controlled mineralisation. The provisional classification of these biomineralization proteins is presented. The interrelation of the origin of the first organic polymers and biomineralization is discussed.

Impact of cell division on intracellular uptake and nuclear targeting with fluorescent SiC-based nanoparticles.

Semiconductor nanoparticles (NPs) became important and wide-used tool for cell imaging because of their unique remarkable properties. Nevertheless, all previous investigations in this area were done on proliferating cells. For the first time, this work demonstrates strong influence of cell active proliferation/contact inhibition of proliferation on uptake of NPs. In addition, we show that cell division plays key-role in penetration of silicon carbide based NPs (SiC NPs) inside the cell nucleus. This may very likely concern other types of NPs able to reach the cell nuclei. In particular, observed effect of cell division gives perspectives for future selective cancer treatment with NPs.

Protein immobilization on 3C-SiC (100) as a substrate for detecting the onset of acute myocardial infarction (AMI).

Silicon Carbide (SiC), has been shown to be a bio- and hema-compatible substrate that could potentially be used in biosensor applications. The development of a viable biorecognition interface using SiC as the substrate material for bio-detection is described. Surface modification with 3-aminopropyltriethoxysilane (APTES) and immobilization via covalent conjugation of antimyoglobin (anti-Myo) on the modified surfaces is achieved, which are initial steps for immunosensing based devices. Successful formation of APTES layers and antibody immobilization were identified with surface water contact angle (SWCA), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).

Interactions of amines with silicon species in undersaturated solutions leads to dissolution and/or precipitation of silica.

The biogeochemical silicon cycle is the focus for many researchers studying the dissolution of silicon species from quartz, amorphous, and biogenic silica. Furthermore, the precipitation of biogenic silica by diatoms, radiolarian, sponges, and plants is also a popular focus for research. The ornate silica structures created by these species has attracted interest from biomaterial scientists and biochemists who have studied mineral formation in an attempt to understand how biogenic silica is formed, often in the presence of proteins and long chain polyamines. This article is at the interface of these seemingly distinct research areas. Here we investigate the effect of a range of amines in globally undersaturated silicon environments. Results are presented on the effect of amine-containing molecules on the formation of silica from undersaturated solutions of orthosilicic acid and globally undersaturated silicon environments. We sought to address two questions: can silica be precipitated/harvested from undersaturated solutions, and can we identify the silicon species that are most active in silica formation? We demonstrate that none of the bioinspired additives investigated here (e.g., poly(allylamine hydrochloride), pentaethylenehexamine, and propylamines) have any influence on orthosilicic acid at undersaturated concentrations. However, under globally undersaturated silicon concentrations, small molecules and polymers containing amine groups were able to interact with oligomers of silicic acid to either generate aggregated materials that can be isolated from solution or increase rates of oligomer dissolution back to orthosilicic acid. Additional outcomes of this study include an extended understanding of how polyelectrolytes and small molecules can promote and/or inhibit silica dissolution and a new method to explore how (bio)organic molecules interact with a forming mineral phase.

A comprehensive biological evaluation of ceramic nanoparticles as wear debris.

Patients are exposed internally to nanoparticles (NPs) by wear mechanisms associated with total joint arthroplasty. This tissue-specific retention implies that the biological evaluation of NPs shall be integrative and niche targeting. Here, we report that ceramic zirconia and silicon nitride NPs interfere with MG63 cells' function and remarkably stimulate the secretion of TNF-α in RAW264.7 cells. However, alumina NPs significantly promote the alkaline phosphatase (ALP) activity of MG63 cells at low concentration and do not show irritation to macrophages. In this study, we prove that ceramic materials at nanoscale are bioactive to cells. These findings also suggest that a more rational paradigm for the biosafety evaluation of NPs than is currently in place is needed before their clinical applications. FROM THE CLINICAL EDITOR: In this study, the authors demonstrate that ceramic nano materials associated with normal wear-and-tear of joint prostheses at nanoscale are bioactive to cells.

Atomic force microscopy investigations of heterogeneities in the adhesion energies measured between pathogenic and non-pathogenic Listeria species and silicon nitride as they correlate to virulence and adherence.

Atomic force microscopy (AFM) was used to probe heterogeneities in adhesion energies measured between pathogenic and non-pathogenic species of Listeria and silicon nitride in water at four levels. Adhesion energies were quantified on individual bacterial cells (cell level), bacterial cells that belonged to an individual Listeria strain but varied in their cultures (strain level), bacterial cells that belonged to an individual Listeria species but varied in their strain type (species level) and on bacterial cells that belonged to the Listeria genus but varied in their species type (genus level). To quantify heterogeneities in the adhesion energies, a heterogeneity index (HI) was defined based on quantified standard errors of mean. At the cell level, spatial variations in the adhesion energies were not observed. For the strain, species, and genus levels, the HI increased with increased adhesion energies. At the species level, the HI increased with strain virulence.

Remediation of copper polluted red soils with clay materials.

Attapulgite and montmorillonite were utilized to remediate heavy metal polluted red soils in Guixi City, Jiangxi Province, China. The effects of clay minerals on availability, chemical distribution, and biotoxicity of Cu and Zn were evaluated. The results provided a reference for the rational application of clay materials to remediate heavy metal contaminated soils. From the sorption experiment, the maximum adsorbed Cu2+ by attapulgite and montmorillonite was 1501 and 3741 mg/kg, respectively. After polluted red soil was amended with attapulgite or montmorillonite and cultured at 30 and 60 days, soil pH increased significantly compared to the control. An 8% increase in the amount of montmorillonite in soil and 30 days incubation decreased acid exchangeable Cu by 24.7% compared to the control red soil. Acid exchangeable Cu decreased with increasing amounts of attapulgite and montmorillonite, with best remediation effect reached at a dose of 8%. Results also showed that the Cu poisoning effect on earthworms was reduced with the addition of attapulgite and montmorillonite. Montmorillonite showed the best effect, with the addition of a 2% dose the mortality of earthworms decreased from 60% to zero compared to the control. Our results indicated that the bioavailability of Cu in soils was reduced more effectively with the application of montmorillonite than attapulgite.

Development of a high temperature-atmospheric pressure environmental cell for high-resolution TEM.

An environmental cell for high-temperature, high-resolution transmission electron microscopy of nanomaterials in near atmospheric pressures is developed. The developed environmental cell is a side-entry type with built-in specimen-heating element and micropressure gauge. The relationship between the cell condition and the quality of the transmission electron microscopic (TEM) image and the diffraction pattern was examined experimentally and theoretically. By using the cell consisting of two electron-transparent silicon nitride thin films as the window material, the gas pressure inside the environmental cell is continuously controlled from 10(-5) Pa to the atmospheric pressure in a high-vacuum TEM specimen chamber. TEM image resolutions of 0.23 and 0.31 nm were obtained using 15-nm-thick silicon nitride film windows with the pressure inside the cell being around 5 × 10(-5) and 1 × 10(4) Pa, respectively.

Effectiveness of serum megakaryocyte potentiating factor in evaluating the effects of chrysotile and its heated products on respiratory organs.

Chrysotile (CH), the most common form of asbestos, is rendered less toxic by heating it at 1000°C and converting it to forsterite (FO-1000). However, further safety tests are needed to evaluate human health risk of these materials. It has been reported that serum concentrations of megakaryocyte potentiating factor N-ERC/mesothelin become elevated in patients with mesotheliomas caused by asbestos exposure. In this study, a single 2mg dose of CH or FO-1000 was intratracheally administered to rats. Within 180days after the administrations, serum N-ERC/mesothelin concentrations, levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in lung tissues and pathological changes in respiratory organs were determined. In the CH group, a significant increase in serum N-ERC/mesothelin concentrations was observed immediately after intratracheal administration, and the elevation lasted for 30days. In lung tissues, positive staining for 8-OHdG in bronchioles, alveolar epithelium, inflammatory cells, and granulomas was evidence of a marked DNA oxidative damage. Furthermore, measurements of 8-OHdG in lung tissues based on the HPLC-ECD method suggested that serum N-ERC/mesothelin concentrations tended to increase when there are significant DNA damages in lung tissues. In contrast, in the FO-1000 group, a marked rise in serum N-ERC/mesothelin concentrations occurred only in the early phase (1-7days) after intratracheal administration. Similarly, FO-1000 induced elevation of 8-OHdG in lung tissues was transient and modest compared with those of the CH-treated animals. In both the CH and FO-1000 groups, we observed significant correlations between serum N-ERC/mesothelin concentrations and lung 8-OHdG concentrations (r=0.559, p=0.001 for the CH group; r=0.516, p=0.01 for the FO-1000 group). In summary, we demonstrated the possibility of using serum N-ERC/mesothelin concentrations as a useful biomarker for early phase exposure to either CH or FO-1000.

Recent advances in plant transformation.

Plant genetic engineering has become one of the most important molecular tools in the modern molecular breeding of crops. Over the last decade, significant progress has been made in the development of new and efficient transformation methods in plants. Despite a variety of available DNA delivery methods, Agrobacterium- and biolistic-mediated transformation remain the two predominantly employed approaches. In particular, progress in Agrobacterium-mediated transformation of cereals and other recalcitrant dicot species has been quite remarkable. In the meantime, other transgenic-enabling technologies have emerged, including generation of marker-free transgenics, gene targeting, and chromosomal engineering. Although transformation of some plant species or elite germplasm remains a challenge, further advancement in transformation technology is expected because the mechanisms of governing the regeneration and transformation processes are now better understood and are being creatively applied to designing improved transformation methods or to developing new enabling technologies.

[Response of applying palygorskite and fertilization on growth rules of Radix Hedysari].

OBJECTIVE: Study on the growth development and fertilizer requirement regularity of Radix Hedysari. METHODS: Adopted the field experiment, investigate the influence of Radix Hedysari by applying different amount of palygorskite and fertilization. RESULTS: The growth process of plant height and branch height of Radix Hedysari were divided into two stages, the stage from emergence to late July was fast growth phase, and the stage from late July was slow growth stage. The dry matter accumulation center of Radix Hedysari transferred from aerial part to underground part in late July. Single application of palygorskite (1500 kg/hm2) and single application of palygorskite (2250 kg/hm2) increased plant height, promoted dry matter accumulation in aerial part and root of Radix Hedysari. Combined application of palygorskite (1500 kg/hm2) and NPK fertilizer and combined application of palygorskite (2250 kg/hm2) and NPK fertilizer improved growth indexes of Radix Hedysari compared with single application of NPK fertilize. CONCLUSION: The yield of Radix Hedysari was improved by applying palygorskite and fertilization.