Growth, spectroscopy and SESAM mode-locking of a "mixed" Yb:Ca(Gd,Y)AlO4 disordered crystal.

We present the growth, spectroscopy, continuous-wave (CW) and passively mode-locked (ML) operation of a novel "mixed" tetragonal calcium rare-earth aluminate crystal, Yb3+:Ca(Gd,Y)AlO4. The absorption, stimulated-emission, and gain cross-sections are derived for π and σ polarizations. The laser performance of a c-cut Yb:Ca(Gd,Y)AlO4 crystal is studied using a spatially single-mode, 976-nm fiber-coupled laser diode as a pump source. A maximum output power of 347 mW is obtained in the CW regime with a slope efficiency of 48.9%. The emission wavelength is continuously tunable across 90 nm (1010 - 1100 nm) using a quartz-based Lyot filter. With a commercial SEmiconductor Saturable Absorber Mirror to initiate and maintain ML operation, soliton pulses as short as 35 fs are generated at 1059.8 nm with an average output power of 51 mW at ∼65.95 MHz. The average output power can be scaled to 105 mW for slightly longer pulses of 42 fs at 1063.5 nm.

Continuous-wave and SESAM mode-locked operation of a Yb:YSr3(PO4)3 laser.

We report on the continuous-wave (CW) and, for what we believe to be the first time, passively mode-locked (ML) laser operation of an Yb3+-doped YSr3(PO4)3 crystal. Utilizing a 976-nm spatially single-mode, fiber-coupled laser diode as pump source, the Yb:YSr3(PO4)3 laser delivers a maximum CW output power of 333 mW at 1045.8 nm with an optical efficiency of 55.7% and a slope efficiency of 60.9%. Employing a quartz-based Lyot filter, an impressive wavelength tuning range of 97 nm at the zero level was achieved in the CW regime, spanning from 1007 nm to 1104 nm. In the ML regime, incorporating a commercially available semiconductor saturable absorber mirror (SESAM) to initiate and maintain soliton-like pulse shaping, the Yb:YSr3(PO4)3 laser generated pulses as short as 61 fs at 1062.7 nm, with an average output power of 38 mW at a repetition rate of ∼66.7 MHz.

Role of Thylakoid Lipids in Protochlorophyllide Oxidoreductase Activation: Allosteric Mechanism Elucidated by a Computational Study.

Light-dependent protochlorophyllide oxidoreductase (LPOR) is a chlorophyll synthetase that catalyzes the reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide) with indispensable roles in regulating photosynthesis processes. A recent study confirmed that thylakoid lipids (TL) were able to allosterically enhance modulator-induced LPOR activation. However, the allosteric modulation mechanism of LPOR by these compounds remains unclear. Herein, we integrated multiple computational approaches to explore the potential cavities in the Arabidopsis thaliana LPOR and an allosteric site around the helix-G region where high affinity for phosphatidyl glycerol (PG) was identified. Adopting accelerated molecular dynamics simulation for different LPOR states, we rigorously analyzed binary LPOR/PG and ternary LPOR/NADPH/PG complexes in terms of their dynamics, energetics, and attainable allosteric regulation. Our findings clarify the experimental observation of increased NADPH binding affinity for LPOR with PGs. Moreover, the simulations indicated that allosteric regulators targeting LPOR favor a mechanism involving lid opening upon binding to an allosteric hinge pocket mechanism. This understanding paves the way for designing novel LPOR activators and expanding the applications of LPOR.

Optimization and mechanism studies on cell disruption and phosphorus recovery from microalgae with magnesium modified hydrochar in assisted hydrothermal system.

Considering the phosphorus (P) reserve state and its value, recovery of P from microalgae has become a popular topic. In this study, an integrated system of a hydrothermal process for microalgae cell disruption to release P and magnesium modified hydrochar adsorption to capture P was set up. Emission scanning electron microscopy with Energy Dispersive X-ray spectroscopy and Three-Dimensional Excitation Emission matrix spectroscopy with parallel factor analysis were applied to evaluate the P release process from microalgae and found the optimal breaking-wall condition (P release 90.5%, hydrothermal digestion mixture of H2O2 and NaOH at 348 K). Parallel factor analysis showed there was a close relationship between P and humic-like substance. Hydrochar loaded with magnesium exhibited a strong affinity for P, with maximum capacity 89.61 mg/g at 318 K. The P adsorption fitted pseudo-second-order kinetic and Langmuir models. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were applied to reveal the mechanism of hydrochar modification and adsorption. It showed that Mg is loaded on the surface of hydrochar by electrostatic attraction and electron transfer with the carboxylic acid. P absorption was reached through anion exchange.

Phosphorus recovery from biogas fermentation liquid by Ca-Mg loaded biochar.

Shortage in phosphorus (P) resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar (Ca-Mg/biochar) application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600>Ca-Mg/B450>Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment.

Epithelial-mesenchymal transition involved in pulmonary fibrosis induced by multi-walled carbon nanotubes via TGF-beta/Smad signaling pathway.

Multi-walled carbon nanotubes (MWCNT) are a typical nanomaterial with a wide spectrum of commercial applications. Inhalation exposure to MWCNT has been linked with lung fibrosis and mesothelioma-like lesions commonly seen with asbestos. In this study, we examined the pulmonary fibrosis response to different length of MWCNT including short MWCNT (S-MWCNT, length=350-700nm) and long MWCNT (L-MWCNT, length=5-15µm) and investigated whether the epithelial-mesenchymal transition (EMT) occurred during MWCNT-induced pulmonary fibrosis. C57Bl/6J male mice were intratracheally instilled with S-MWCNT or L-WCNT by a single dose of 60µg per mouse, and the progress of pulmonary fibrosis was evaluated at 7, 28 and 56 days post-exposure. The in vivo data showed that only L-MWCNT increased collagen deposition and pulmonary fibrosis significantly, and approximately 20% of pro-surfactant protein-C positive epithelial cells transdifferentiated to fibroblasts at 56 days, suggesting the occurrence of EMT. In order to understand the mechanism, we used human pulmonary epithelial cell line A549 to investigate the role of TGF-ß/p-Smad2 signaling pathway in EMT. Our results showed that L-MWCNT downregulated E-cadherin and upregulated α-smooth muscle actin (α-SMA) protein expression in A549 cells. Taken together, both in vivo and in vitro study demonstrated that respiratory exposure to MWCNT induced length dependent pulmonary fibrosis and epithelial-derived fibroblasts via TGF-ß/Smad pathway.

[Comparative analysis for the cytotoxicity and genotoxicity of multi-walled carbon nanotubes with different lengths and surface modifications in A549 cells].

OBJECTIVE: To compare the cytotoxicity and DNA strand breakage induced by multi-walled carbon nanotubes (MWCNTs) with different lengths and different surface modifications in human alveolar type II cells (A549 cells). METHODS: Two different lengths (5-15 µm, 350-700 nm) of MWCNTs and three different kinds of surface modified MWCNTs (COOH-MWCNTs, NH2-MWCNTs, and Tau-MWCNTs) were used in the experiments. The short MWCNTs were used as pristine MWCNTs to compare with the 3 surface modified MWCNTs. The cytotoxicity was determined by cell counting kit-8 (CCK-8) assay at the concentrations of 2, 8, and 32 mg/L at hours 12, 24, 36, and 48 respectively. Single cell gel electrophoresis (SCGE) assay was performed to evaluate DNA strand breakage in A549 cells after 24 h treatment of 8 mg/L of each tested material. RESULTS: Long multi-walled carbon nanotubes (Long-MWCNTs) and short multi-walled carbon nanotubes (Short-MWCNTs) showed a dose-dependent cytotoxicity within the exposure time 12-48 h. Especially, Long-MWCNTs showed greater cytotoxicity than Short-MWCNTs from 24 to 48 h at the same concentration. The relative cell viability of the 3 surface modified MWCNTs was higher than that of the pristine MWCNTs at h 12 at the concentration of 32 mg/L [COOH-MWCNTs (86.55±1.80)%, NH2-MWCNTs (84.67±1.32)%, Tau-MWCNTs (80.15±3.53)% and Pristine-MWCNTs (71.44±5.58)%], at h 24 at the concentration of 8 mg/L [COOH-MWCNTs (96.74±1.00)%, NH2-MWCNTs (96.74±3.35)%, Tau-MWCNTs (106.39±3.83)% and Pristine-MWCNTs (91.02±2.53)%], at h 24 at the concentration of 32 mg/L [COOH-MWCNTs (80.88±2.67)%, NH2-MWCNTs (82.90±3.25)%, Tau-MWCNTs (82.55±3.32)% and Pristine-MWCNTs (76.08±4.27)%] and at h 36 at the concentration of 8 mg/L [COOH-MWCNTs (96.87±1.05)%, NH2-MWCNTs (96.66±4.76)%, Tau-MWCNTs (100.23± 2.84)% and Pristine-MWCNTs (89.61±3.78)%], and the differences were statistically significant (P<0.05). Compared with the Pristine-MWCNTs, the relative cell viability of the 3 surface modified MWCNTs didn't demonstrate a statistically significant difference (P>0.05) at other observation time and exposure concentrations. The DNA strand breakage of the 3 surface modified MWCNTs: the Olive tail moment of COOH-MWCNTs was 1.56±0.22, the Olive tail moment of NH2-MWCNTs 2.25±1.62 and the Olive tail moment of Tau-MWCNTs 2.23±0.94; the tail DNA% of COOH-MWCNTs was (3.96± 0.60)%, the tail DNA% of NH2-MWCNTs (6.16±4.68)% and the tail DNA% of Tau-MWCNTs (6.05±2.31)%, which were lower than that of the pristine MWCNTs (P<0.05), whose Olive tail moment was 3.00±0.64 and tail DNA% (8.23±2.27)%. Moreover, the COOH-MWCNTs induced the lowest DNA damage among the three modified MWCNTs. CONCLUSION: Long-MWCNTs compared with Short-MWCNTs demonstrated a greater cytotoxicity and lower DNA strand breakage damage. The surface modifications of MWCNTs can reduce the cytotoxicity and DNA strand breakage in A549 cells.

[Effect of titanium dioxide nanoparticles on hemogram in rats with gastric ulcer].

OBJECTIVE: To explore the effect of titanium dioxide (TiO2) nanoparticles on hemogram in rats with gastric ulcer. METHODS: Physicochemical properties of TiO2 nanoparticles were characterized. Twenty-four clear class SD male rats, aging 8 week-old, were randomly divided into 4 groups, 6 rats for each group. 20% acetic acid were injected into the rats' stomach on the border of gastric body and pyloric antrum, and hereby established the gastric ulcer model. The rats in 4 groups were exposed to TiO2 nanoparticles through intragastric administration at 0, 10, 50 and 200 mg/kg body weight respectively for 30 days. Afterwards, the rats were conducted blood routine test and blood coagulation test for analysis. RESULTS: TiO2 nanoparticles were anatase crystals, closely spherical shape, whose average grain diameter was (75 ± 15) nm. The levels of white blood cell (WBC) count ((8.48 ± 3.28)×109/L), lymphocyte (LYM) ((6.85 ± 2.53)×109/L), monocyte (MOD) ((0.27 ± 0.12)×109/L), granulocyte (GRN) ((1.37 ± 0.86)×109/L), red blood cell (RBC) ((8.20 ± 0.49)×109/L) and hematocrit (HCT) ((45.3 ± 1.4)%) in the 200 mg/kg dose group were significantly higher than those in the control group ((2.63 ± 0.34)×109/L, (2.25 ± 0.26)×109/L, (0.05 ± 0.06)×109/L, (0.33 ± 0.26)× 109/L, (4.87 ± 2.37)×109/L and (27.2 ± 13.3)%, respectively; t values were -3.449, -3.825, -3.554, -3.097, -2.972 and -2.936 respectively, P values all < 0.05). The levels of WBC ((6.88 ± 3.06)×109/L), MOD ((0.20 ± 0.07)×109/L), RBC ((7.79 ± 0.48)×109/L) and HCT ((42.7 ± 2.8)%) in 50 mg/kg dose group were also statistically higher than those in the control group (t values were -2.507, -2.367, -2.605 and -2.511 respectively, all P values < 0.05). There was no statistically difference found in other blood routine index and coagulation index between the three experimental groups and control group. CONCLUSION: The long term intake of TiO2 nanoparticles caused a statistically increase in the amount of WBC and RBC in rats with gastric ulcer; however, there was no obvious changes found in blood platelet and coagulation index.

Multi-walled carbon nanotubes induce apoptosis via mitochondrial pathway and scavenger receptor.

We have demonstrated previously that the acid-treated multi-walled carbon nanotubes (aci-MWCNTs) and taurine functionalized MWCNTs (tau-MWCNTs) induced differential pulmonary toxicity in mice after instillation exposure. In order to compare differences of cytotoxicity between the aci- and tau-MWCNTs, RAW 264.7 cells (a murine macrophage cell line) were chosen to be exposed to the aci- and tau-MWCNTs at concentrations of 0, 5, 20, 40, and 80µg/ml for 12 or 24h respectively. The results showed that although the aci- and tau-MWCNTs induced only mild decrease in cell viability to RAW 264.7 cells, the two types of MWCNTs elicited significant increase in apoptosis and decreased ability in cellular phagocytosis. Moreover, by using the specific inhibitors, we found that the scavenger receptors (SR) and caspase-9 were actively involved in the apoptosis induced by the aci- and tau-MWCNTs. The taurine functionalized MWCNTs (tau-MWCNTs) showed less cytotoxicity and apoptotic effect to RAW 264.7 cells than those of aci-MWCNTs. Taken together, the results indicated the important role of scavenger receptors and mitochondria in the apoptosis induced by MWCNTs.

Water-soluble taurine-functionalized multi-walled carbon nanotubes induce less damage to mitochondria of RAW 264.7 cells.

Multi-walled carbon nanotubes (MWCNTs) are increasingly used and many studies have already showed their cytotoxicity in different kinds of cell lines, while their mechanism is not fully understood. Mitochondria are the relatively sensitive organelle in response to the stress challenged by the exogenous chemicals. The study aimed to evaluate mitochondrial injury and cytotoxicity in mouse peritoneal macrophage cell line (RAW 264.7) induced by the water-soluble taurine functionalized MWCNTs (tau-MWCNTs) and pristine raw MWCNTs (raw-MWCNTs). The different concentrations including 0, 5, 20, 40 and 80 microg/ml for both kinds of MWCNTs were adopted. The cytotoxicity and the mitochondrial function were assessed after 12 h and 24 h treatment. The results revealed that both MWCNTs could produce significantly dose-dependent cytotoxicity and mitochondrial injury including the decrease of mitochondrial membrane potential, the release of cytochrome c from mitochondria and the increase of cytoplasm Ca2+ content. The activities of adenosine triphosphatases (ATPase) and succinodehydrogenase (SDH) of mitochondria were all inhibited after MWCNTs treatment. In conclusion, MWCNTs could lead to mitochondrial injury, which might be one possible pathway of apoptotic cell induction. The findings that tau-MWCNTs exhibited less toxicity compared with raw-MWCNTs support a useful approach to reduce the toxicity of MWCNTs by surface-functionization with taurine.

Toxicity of nano gamma alumina to neural stem cells.

Nano alumina, one of the most important nanomaterials, is widely used in diverse areas. It was reported that nano alumina could cross the blood brain barrier to enter the brain. Considering aluminum accumulation in brain is closely related to many neural diseases. We studied the neural toxicity of four nano gamma-alumina samples by using neural stem cells (NSCs) C17.2 as a model. We find that the toxicity of nano gamma-alumina is pretty low, though these alumina particles are easily internalized by cells. The loss of cell viability and membrane integrity are dose-dependent and sample-dependent after alumina exposure. At concentrations lower than 100 microg/mL, no significant toxicity is observed for all alumina samples. When the concentration reaches 200 microg/mL, alumina treated cells begin to loss their activities. No culture period effect (up to 3 days) is observed. Very tiny soluble aluminum and the absorption of culture medium ingredients onto alumina particles do not affect the cell viability. Intracellular reactive oxygen species generation may contribute to the cytotoxicity of alumina particles at high concentration, but it does not induce the apoptosis of NSCs.

[The cytotoxicity and expression changes of endoplasmic reticulum related genes induced by MWCNTs with different surface modifications].

OBJECTIVE: To compare the cytotoxicity of RAW264.7 cells induced by two types of multi-walled carbon nanotubes (MWCNTs) with different surface modifications (MWCNTs modified by taurine and MWCNTs treated by acid), and explore the role of endoplasmic reticulum (ER) in MWCNTs-induced apoptosis. METHODS: RAW264.7 cells were exposed to tau-MWCNTs or c-MWCNTs, of which the diameters and impurity contents were the same, at the dose of 0, 1.56, 3.12, 6.25, 12.50, 25.00 µg/cm(2) for 3, 6, 12 and 24 h, respectively. Then the cytotoxicity of MWCNTs was determined by WST-1 assay, and the percentages of apoptosis were analyzed via flow cytometry with AnnexinV-FITC/PI label. Real-time PCR was used to detect mRNA expression levels of CRT, GRP78 and CHOP genes which were related to ER calcium regulation, stress and apoptosis. RESULTS: Compared with the c-MWCNTs groups, the cytotoxicity of tau-MWCNTs was lower at the same dose and treatment time. Both the two types of MWCNTs could induce cytotoxicity apparently and statistically, when the cells were treated for only 3 h at the doses of more than 12.50 µg/cm(2) or treated for more than 12 h at the lower dose of 3.12 µg/cm(2) (P<0.05). The results of flow cytometry showed that the two MWCNTs could induce apoptosis of RAW264.7 cells in the dose- and time-dependently manner. The apoptosis rate of the cells treated for 24 h was higher than that for 12 h. And at each dose, the apoptosis rate induced by c-MWCNTs was also higher than that of the water soluble tau-MWCNTs within our study design. However, in this study, the mRNA expression levels of CRT, GRP78 and CHOP mRNA treated with both types of MWCNTs did not show any significant differences compared with the control groups. CONCLUSION: The cytotoxicity of tau-MWCNTs was much lower than that of c-MWCNTs. Unfortunately, we found the expression of genes related to ER had little effects on the apoptosis of RAW264.7 treated with MWCNTs, indicating that the ER pathway might not be the mechanism of MWCNTs-induced apoptosis.

Diameter-selective dispersion of double-walled carbon nanotubes by lysozyme.

We have utilized lysozyme to non-covalently functionalize and disperse double-walled carbon nanotubes (DWNTs) in aqueous solution. Lysozyme preferentially binds and disperses DWNTs with larger diameters. This is a facile and effective method to fractionalize and enrich DWNTs with certain diameters.

Removal of carbon nanotubes from aqueous environment with filter paper.

The potential health and environmental hazards of carbon nanotubes (CNTs) have been a concerned issue. However, in contrast to the wide recognition of the toxicity of CNTs, little attention has been paid to the decontamination/remediation of CNT pollution. In this study, we report that CNTs can be removed from aqueous environment. In the presence of Ca²(+), CNTs aggregate quickly to micron size and then enable easy and effective removal via normal filtration. After filtration, CNT suspension becomes colorless with the remnant CNT concentration less than 0.5 µg mL⁻¹, a safe dose based on the published data. The filtration approach also works well in the presence of typical surfactant and dissolved organic matter. The removal efficiency is Ca²(+) concentration-dependent and regulated by the initial pH value and ionic strength. Our study is helpful for future decontamination of CNTs from aqueous environment.

[Two types of MWNTs with different surface modifications induce differential expression of proteins in RAW264.7 cells].

OBJECTIVE: To compare the different expression of protein in RAW264.7 macrophage cells induced by two types of MWNTs (multi-walled carbon nanotubes) with different surface modifications (acid-treated MWNTs and tau-MWNTs modified by taurine). METHODS: Treating cells with both types of MWNTs in 20 mg/L and 24 h, with a blank-control group set. Cells are lysed by using urea and by ultrasonicating in ice bath, then total proteins of cells are extracted. Using two-dimensional gel electrophoresis to separate total proteins of cells, searching for the differential expressed protein spots on the images of the gels with silver staining. Identifying the differentially expressed proteins via mass spectrometry, and studying the mechanism of effects on cells imposed by two types of MWNTs at protein level. RESULTS: There are 13 spots of protein with notably differential expression among three treated groups (including blank controls). Their functions involve apoptosis-related, calcium-binding, cell-cycle related, DNA synthesis, folding of proteins, and energy metabolism, etc. The results are consistent with our previous studies about the cytotoxicity of Both types of MWNTs including induction of apoptosis and mitochodira damage. CONCLUSION: Both two types of MWNTs could induce alteration of protein expression in RAW264.7 cells. With different surface modifications, they imposed different effects. High throughout proteomics could be applied in toxicity assessment and mechanism investigation about carbon nanotubes.

Long-term accumulation and low toxicity of single-walled carbon nanotubes in intravenously exposed mice.

The biomedical application of single-walled carbon nanotubes (SWCNTs), such as drug delivery and cancer treatment, requires a clear understanding of their fate and toxicological profile after intravenous administration. In this study, the long-term accumulation and toxicity of intravenously injected SWCNTs in the main organs (such as liver, lung and spleen) in mice were carefully studied. Although SWCNTs stayed in mice over 3 months, they showed low toxicity to mice. The long-term accumulation of SWCNTs in the main organs was evidenced by using Raman spectroscopy and TEM technique. Statistically significant changes in organ indices and serum biochemical parameters (LDH, ALT and AST) were observed. The histological observations demonstrate that slight inflammation and inflammatory cell infiltration occurred in lung, but the serum immunological indicators (CH 50 level and TNF-alpha level) remained unchanged. No apoptosis was induced in the main organs. The decreasing glutathione (GSH) level and increasing malondialdehyde (MDA) level suggest that the toxicity of SWCNTs might be due to the oxidative stress.

A generally adoptable radiotracing method for tracking carbon nanotubes in animals.

Carbon nanotube (CNT) mediated drug delivery systems have currently aroused a great deal of interest. Such delivery systems for drugs, proteins and genes have been preliminarily studied using cellular and animal models. For the further study of the pharmacokinetics and related biological behaviours of CNTs in vivo, a fast and convenient tracing method is particularly demanded. In this paper, we developed a generally adoptable tracing method for the biodistribution study of functionalized CNTs in vivo. Taurine covalently functionalized multi-walled carbon nanotubes (tau-MWNTs) and Tween-80 wrapped MWNTs (Tween-MWNTs) were labelled with (125)I, and then their distribution in mice was determined. It is interesting that Tween-80 can reduce the RES uptake of MWNTs remarkably. The resulting distribution of (125)I-tau-MWNTs was very consistent with that using (14)C-taurine-MWNTs as the CNTs tracer, which means the easy (125)I labelling method is reliable and effective.