Removal of cesium and strontium for radioactive wastewater by Prussian blue nanorods.

In this work, novel Prussian blue tetragonal nanorods were prepared by template-free solvothermal methods to remove radionuclide Cs and Sr. The as-prepared Prussian blue nanorods were identified and characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopic, thermogravimetric analysis, zeta potential, and surface analysis, and its sorption performance was tested by batch experiments. Our results suggest that Prussian blue nanorods exhibited better adsorption performance than co-precipitation PB or Prussian blue analogue composites. Thermodynamic analysis implied that the adsorption process was spontaneous and endothermic which was described well with the Langmuir isotherm and pseudo-second-order equation. The maximum adsorption capacity of PB nanorod was estimated to be 194.26 mg g-1 and 256.62 mg g-1 for Cs+ and Sr2+(adsorbate concentration at 500 mg L-1, the temperature at 298 k, pH at 7.0). Moreover, the experimental results showed that the Prussian blue nanorods have high crystallinity, few crystal defects, and good stability under alkaline conditions. The adsorption mechanism of Cs+ and Sr2+ was studied by X-ray photoelectron spectroscopy, X-ray diffraction, and 57Fe Mössbauer spectroscopy. The results revealed that Cs+ entered the PB crystal to generate a new phase, and most of Sr2+ was trapped in the internal crystal and the other exchanged Fe2+. Furthermore, the effect of co-existing ions and pH on PB adsorption process was also investigated. The results suggest that PB nanorods were an outstanding candidate for removing Cs+ and Sr2+ from radioactive wastewater.

Core-Shell Molecularly Imprinted Polymers on Magnetic Yeast for the Removal of Sulfamethoxazole from Water.

In this work, magnetic yeast (MY) was produced through an in situ one-step method. Then, MY was used as the core and the antibiotic sulfamethoxazole (SMX) as the template to produce highly selective magnetic yeast-molecularly imprinted polymers (MY@MIPs). The physicochemical properties of MY@MIPs were assessed by Fourier-transform infrared spectroscopy (FT-IR), a vibrating sample magnetometer (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), specific surface area (SBET) determination, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out to compare MY@MIPs with MY and MY@NIPs (magnetic yeast-molecularly imprinted polymers without template), with MY@MIPs showing a better performance in the removal of SMX from water. Adsorption of SMX onto MY@MIPs was described by the pseudo-second-order kinetic model and the Langmuir isotherm, with maximum adsorption capacities of 77 and 24 mg g-1 from ultrapure and wastewater, respectively. Furthermore, MY@MIPs displayed a highly selective adsorption toward SMX in the presence of other pharmaceuticals, namely diclofenac (DCF) and carbamazepine (CBZ). Finally, regeneration experiments showed that SMX adsorption decreased 21 and 34% after the first and second regeneration cycles, respectively. This work demonstrates that MY@MIPs are promising sorbent materials for the selective removal of SMX from wastewater.

Mechanisms of strontium's adsorption by Saccharomyces cerevisiae: Contribution of surface and intracellular uptakes.

The objective of this work was to explore the mechanisms participating in strontium sorption by living Saccharomyces cerevisiae (S. cerevisiae). The location of strontium adsorbed by S. cerevisiae was studied by our plasmolysis treatment. The contribution of physical and chemical mechanisms was determined quantitatively by desorption and blockage of functional groups. Moreover, our results indicated that bioaccumulation also played a major role in biosorption by living cells. Thus, supplementary methods including 2-DE (two-dimensional electrophoresis) and Matrix-Assisted Laser Desorption/Ionization Tandem Time of Flight Mass Spectrometry (MALDI-TOF-TOF) were employed to analyze the different proteins. The subsequent desorption % of Sr2+ by Distilled Water (DW), NH4NO3 and EDTA-Na2 from Sr2+ loaded sorbents indicated a minor role for physical adsorption, while ion exchange and complexation were responsible for approximately 20% and 40%. Specific blockage of functional groups revealed that carboxyl and amine groups played an important role in Sr2+ binding to the living S. cerevisiae. From our MALDI-TOF-TOF results, we concluded that 38 proteins showed up-regulated expression profiles and 11 proteins showed down-regulated after biosorption. Moreover, proteins belong to: phagocytic function (Act1p); ion channel (S-adenosylmethionine synthase); glycolysis (Tubulin) may directly involve in strontium bioaccumulation. In conclusion, the present work indicates that the strontium sorption mechanism by living S. cerevisiae is complicated including ion-exchange along with complexation as the main mechanism, whereas the other mechanisms such as physical adsorption play a minor contribution. Metabolically-dependent proteins may play an important role in bioaccumulation.

Biosorption of strontium ions from simulated high-level liquid waste by living Saccharomyces cerevisiae.

In this study, the Saccharomyces cerevisiae (S. cerevisiae) was modified by γ-ray. The RNA-seq results reflect that the high γ-ray energies could change some gene fragments, such as deletion, recombination, and mutation. The biosorption of strontium ions (Sr2+) to different types of S. cerevisiae (S. cerevisiae (K-0), modified S. cerevisiae (Y-7), and non-living S. cerevisiae (H-K)) from the simulated high-level liquid waste (S-HLLW) was assessed at different experimental conditions. The sorption experimental results show that, under an appropriate condition, γ-ray radiation can enhance its biosorption capacity slightly of Sr2+ to S. cerevisiae. The maximum metal uptake and efficiency of Y-7 under S-HLLW were 11.656 mg g-1 and 37.91% at 32 h (wet weight), respectively. They decreased to 9.46 mg g-1 and 30.76% under radiation conditions. SEM-EDX and TEM analysis indicates that Sr2+ was adsorbed both on the cellular surface and the inner parts of the cells. Our experimental results fit well to the Langmuir and Freundlich model isotherms (r2 > 0.94), and the maximum biosorption capacity values reached qmax > 24.74 mg g-1 at 32 °C. Negative values of ΔG0 and positive values of ΔH0 were observed, indicating the spontaneous and endothermic nature of Sr2+ biosorption on modified S. cerevisiae. The biosorption kinetics follow a pseudo-second-order equation at 32 °C (r2 > 0.94). The desorption efficiency of Sr2+ adsorbed onto Y-7 was 7.65 ± 0.52%, 76.51 ± 2.13%, and 65.62 ± 2.42% by deionized water, 1 M HCl, and 0.1 M EDTA-Na, respectively. However, they were lower than H-K (18.82, 83.32, and 73.32%). Our findings demonstrate that living S. cerevisiae (Y-7) is a promising sorbent material for the treatment of radioactive process streams.

Batch and fixed-bed column studies for selective removal of cesium ions by compressible Prussian blue/polyurethane sponge.

In this work, compressible Prussian blue/polyurethane sponges (PB@PUS) for selective removal of cesium ions were prepared via an in situ radiation chemical route. The characterization results indicate that uniform PB nanoparticles were successfully synthesized and well dispersed on the porous skeleton of sponge. Batch and fixed-bed column experiments were detailedly conducted to investigate their adsorption performances. Batch adsorption experiments reveal that PB@PUS exhibited good selective removal property for cesium ions in a wide range of pH, whose maximal adsorption capacity and removal efficiency reached 68.6 mg g-1 and 99%, respectively. The adsorption processes could be described by the Langmuir isotherm adsorption model and pseudo-second-order adsorption kinetic model. The fixed-bed column experiments show that the breakthrough and exhaustion time obviously increased with the decrease of flow rate and initial cesium ions concentration. The breakthrough curves could be well fitted by the Thomas model and Yoon-Nelson model. The theoretical saturated adsorption capacity of PB@PUS-3 calculated from the Thomas model was 68.2 mg g-1. The as-prepared samples were light, stable and compressible, which can be applied in radioactive wastewater treatment.

Biosorption of the strontium ion by irradiated Saccharomyces cerevisiae under culture conditions.

As a new-emerging method for strontium disposal, biosorption has shown advantages such as high sorption capacity; low cost. In this study, we investigated the potential of Saccharomyces cerevisiae (S. cerevisiae) in strontium disposal under culture conditions and the effects of irradiation on their biosorption capabilities. We found that S. cerevisiae can survive irradiation and grow. Pre-exposure to irradiation rendered S. cerevisiae resistant to further irradiation. Surprisingly, the pre-exposure to irradiation can increase the biosorption capability of S. cerevisiae. We further investigated the factors that influenced the biosorption efficiency, which were (strongest to weakest): pH > strontium concentration > time > temperature. In our orthogonal experiment, the optimal conditions for strontium biosorption by irradiated S. cerevisiae were: pH 7, 150 mg L-1 strontium at the temperature of 32 °C with 30 h. The equilibrium of strontium biosorption was analyzed by Langmuir and Freundlich models, from which the formal model is found to provide a better fit for the experimental results. The kinetics of strontium biosorption by living irradiated S. cerevisiae was found to be comprised of three phases: dramatically increased during 0-9 h, decreased during 12-24 h, and increased during 30-50 h. These results provide a systematic understanding of the biosorption capabilities of irradiated S. cerevisiae, which can contribute to the development of remediating nuclear waste water.

Magnetic nanoparticle decorated multi-walled carbon nanotubes for removing copper ammonia complex from water.

A kind of novel magnetic carbon nanotube composite was prepared and designed for wastewater treatment. Multi-walled carbon nanotubes were decorated with magnetic iron oxide nanoparticles, with an uniform distribution on the nanotube surface. The functionalized carbon nanotubes exhibit superparamagnetic behavior and can be easily and rapidly separated from the dispersion via a magnetic process. The carbon nanotube-iron oxide composites might serve as adsorbent for contaminant adsorption in water, especially for copper ammonia complex removal. The adsorption of copper ammonia complex to carbon nanotube-iron oxide composites is time dependent, and they can be quickly and efficiently removed together through a magnetic separation process. This novel magnetic composites might serve as an efficient and proper adsorbent in wastewater treatment applications.

UV-enhanced cytotoxicity of CdTe quantum dots in PANC-1 cells depend on their size distribution and surface modification.

The cytotoxicity of quantum dots (QDs) under normal conditions has received more and more attention, but their cytotoxicity under light illumination has not been fully investigated. In this study, different sized CdTe QDs coated with mercaptopropionic acid (MPA) and N-acetylcysteine (NAC) were employed to investigate the influences of size distribution and surface modification on their UV-enhanced cytotoxicity and mechanism. The results indicated that different sized MPA-CdTe QDs exhibited distinct cytotoxicity under UV illumination and the smaller-sized QDs presented more obviously damages to cells than the larger-sized QDs. Comparing with MPA-CdTe QDs, NAC-CdTe QDs had better cellular metabolizability and lower cytotoxicity. The generation of reactive oxygen species (ROS) were also investigated. The results revealed that ROS in cells containing MPA-CdTe QD538 were about 1.7 times of NAC-CdTe QD538 under UV illumination. ROS might play an important role in the UV-enhanced cytotoxicity of QDs. By selecting appropriate surface modifications and particle sizes, the cytotoxicity of QDs under UV illumination could be controlled.

Subcellular tracking of drug release from carbon nanotube vehicles in living cells.

The direct observation of drug release from carbon nanotube vehicles in living cells is realized through a unique two-dye labeling approach. Single-walled carbon nanotubes (SWNTs) are firstly marked with fluorescein isothiocyanate (FITC) to track their location and movement inside the cell. Then a fluorescent anticancer drug doxorubicin (DOX) is attached by means of π-stacking onto SWNTs. Delivered by SWNTs into cells, DOX will detach from the vehicle in an acidic environment due to the pH-dependent π-π stacking interaction between DOX and SWNTs. From observation of the two different kinds of fluorescence (green and red) that respectively represent the carrier SWNTs and drug DOX, the process of drug release inside the living cell can be monitored under a confocal microscope. Results show that the drug DOX detaches from SWNTs inside the lysosomes to yield free molecules and escape into the cytoplasm and finally into the nucleus, while the vehicle SWNTs are trapped inside the lysosomes, without entering the nucleus. The current observations confirm previously proposed mechanisms for drug/DOX release inside cells. The experimental establishment of drug-release mechanisms in living cells here might provide important insights for future design of new drug-delivery and release systems.

The combined influence of surface modification, size distribution, and interaction time on the cytotoxicity of CdTe quantum dots in PANC-1 cells.

Mercaptopropionic acid (MPA) and cysteamine (Cys) capped CdTe quantum dots (QDs) were successfully prepared and used to investigate the combined influence of surface modification, size distribution, and interaction time on their cytotoxicity in human pancreatic carcinoma (PANC-1) cells. Results indicated that the smaller the size of MPA-CdTe QDs, the higher the cytotoxicity, which could be partly due to the difference of their distribution inside cells. Comparing with MPA-CdTe QDs, Cys-CdTe QDs had better cellular metabolizability and lower cytotoxicity. These QDs' cellular distribution and cytotoxicity were closely related to their interaction time with cells. Their cytotoxicity was found to be significantly enhanced with the increase of incubation time in medium. After QD treatments, the influence of recover time on the final cell viability was also dependent on the concentration and surface modification of QDs used in pretreatment. The combined influence of these factors discussed here might provide useful information for understanding and reducing the cytotoxicity of QDs in future biomedical applications.

One-step fabrication of biocompatible chitosan-coated ZnS and ZnS:Mn2+ quantum dots via a γ-radiation route.

Biocompatible chitosan-coated ZnS quantum dots [CS-ZnS QDs] and chitosan-coated ZnS:Mn2+ quantum dots [CS-ZnS:Mn2+ QDs] were successfully fabricated via a convenient one-step γ-radiation route. The as-obtained QDs were around 5 nm in diameter with excellent water-solubility. These QDs emitting strong visible blue or orange light under UV excitation were successfully used as labels for PANC-1 cells. The cell experiments revealed that CS-ZnS and CS-ZnS:Mn2+ QDs showed low cytotoxicity and good biocompatibility, which offered possibilities for further biomedical applications. Moreover, this convenient synthesis strategy could be extended to fabricate other nanoparticles coated with chitosan.PACS: 81.07.Ta; 78.67.Hc; 82.35.Np; 87.85.Rs.

Gamma-radiation synthesis of silk fibroin coated CdSe quantum dots and their biocompatibility and photostability in living cells.

Silk fibroin coated CdSe quantum dots (SF-CdSe QDs) were successfully synthesized via a one-step gamma-radiation route in an aqueous system at room temperature. The as prepared products were characterized by transmission electron microscope (TEM), energy dispersion spectrum (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis) and photoluminescence spectrum (PL). The SF-CdSe QDs were about 5 nm in diameter and exhibited excellent water-solubility and photoluminescence properties. The cellular distribution, photostability and cytotoxicity of SF-CdSe QDs with different amount of SF coatings were also investigated by laser scanning confocal microscope (LSCM) and MTT assays in human pancreatic carcinoma (PANC-1) cells. All the results reveal that these QDs could be easily internalized by cells and localized in cytoplasm around nuclei. Moreover, SF-CdSe QDs were proved to be low cytotoxicity (the concentration of QDs < 5 microg mL(-1)) and high photostability (the illumination energy density < 2 x 10(-5) W microm(-2)) within PANC-1 cells, which was mainly due to the biocompatible silk fibroin. The resulted SF-CdSe QDs might have many potential applications in tumor imaging and therapy. And the synthesis strategy could be easily extended to fabrication of other nanoparticles coated with silk fibroin.

UV-enhanced cytotoxicity of thiol-capped CdTe quantum dots in human pancreatic carcinoma cells.

Quantum dots (QDs) have been gaining popularity due to their potential application in cellular imaging and diagnosis, but their cytotoxicity under light illumination has not been fully investigated. In this study, green and red mercaptopropionic acid capped CdTe quantum dots (MPA-CdTe QDs) were employed to investigate their cytotoxicity in human pancreatic carcinoma cells (PANC-1) under UV illumination. MPA-CdTe QDs exhibited excellent photostability under UV illumination and could be easily ingested by cells. The cytotoxicity of MPA-CdTe QDs was significantly enhanced under UV illumination, which was determined by changes in cell morphology as well as by decreases in the metabolic activity and cell counting. Our results indicated that green and red QDs had different cellular distribution and exhibited distinct UV-enhanced cytotoxicity. UV illumination enhanced the generation of reactive oxygen species (ROS) in cells containing QDs, and NAC antioxidant could reduce their damage to cells under UV illumination. Moreover, the influences of different UV illumination conditions on the viability of cells containing QDs were examined and discussed in detail.

Cancer-cell targeting and photoacoustic therapy using carbon nanotubes as "bomb" agents.

A unique approach using the large photoacoustic effect of single-walled carbon nanotubes (SWNTs) for targeting and selective destruction of cancer cells is demonstrated. SWNTs exhibit a large photoacoustic effect in suspension under the irradiation of a 1064-nm Q-switched millisecond pulsed laser and trigger a firecracker-like explosion at the nanoscale. By using such an explosion, a photoacoustic agent is developed by functionalizing the SWNTs with folate acid (FA) that can selectively bind to cancer cells overexpressing folate receptor on the surface of the cell membrane and kill them through SWNT explosion inside the cells under the excitation of millisecond pulsed laser. The uptake pathway of folate-conjugated SWNTs into cancer cells is investigated via fluorescence imaging and it is found that the FA-SWNTs can enter into cancer cells selectively with a high targeting capability of 17-28. Under the treatment of 1064-nm millisecond pulsed laser, 85% of cancer cells with SWNT uptake die within 20 s, while 90% of the normal cells remain alive due to the lack of SWNTs inside cells. Temperature changes during laser treatment are monitored and no temperature increases of more than +/- 3 degrees C are observed. With this approach, the laser power used for cancer killing is reduced 150-1500 times and the therapy efficiency is improved. The death mechanism of cancer cells caused by the photoacoustic explosion of SWNTs is also studied and discussed in detail. These discoveries provide a new way to use the photoacoustic properties of SWNTs for therapeutic applications.

Gamma-radiation synthesis and properties of superparamagnetic CS-ZnSe:Mn nanocrystals for biological labeling.

Chitosan coated ZnSe:Mn (CS-ZnSe:Mn) nanocrystals were successfully synthesized in aqueous system through a gamma-radiation route at room temperature under ambient pressure. The structure and properties of nanocrystals were investigated with transmission electron microscope (TEM), fourier transform infrared spectrometer (FT-IR), ultraviolet-visible (UV-vis) spectrometer, photoluminescence emission (PL) spectra, X-ray Diffraction (XRD) and energy dispersion spectrum (EDS). Results showed that the diameter of these nanocrystals was about 4 nm with narrow size distribution. With the increase of doped Mn2+ concentration, strong emission peak at 610 nm was observed besides the weak emission peak at 425 nm since the non-radiative transition of 4T1(4G)-6A1(6S) level, resulting the transfer of fluorescence color from blue to orange. Moreover, analysis of SQUID magnetometer indicated that the nanocrystals were superparamagnetic with a saturation magnetization of 1.7 emu/g and a Curie-Weiss temperature of 14-15 K. Hep G2 cells were incubated in solution of nanocrystals and results showed that the synthesized nanocrystals could stain cytoplasm but could not enter into nucleus.

Intracellular uptake, trafficking and subcellular distribution of folate conjugated single walled carbon nanotubes within living cells.

Herein we studied the uptake, trafficking and distribution of folate conjugated single walled carbon nanotubes (SWNTs) within living cells. SWNTs were noncovalently functionalized with chitosan and then linked with folate acid and fluorescence dye Alexa Fluor 488 (denoted FA-SWNTs). Hep G2 cells were cultured in vitro and incubated with FA-SWNTs at different levels. The FA-SWNTs exhibited a concentration-dependent uptake within Hep G2 cells, and Hep G2 cells were able to internalize FA-SWNTs via a folate receptor-mediated pathway. The distribution of nanotubes inside cells demonstrated that the FA-SWNTs only locate in the cytoplasm and not in nuclei, indicating the failure of transporting through the nuclear envelope. Transmission electron microscope (TEM) results showed the presence of FA-SWNTs in lysosomes and the discharge to extracellular space after incubation with nanotubes for 5 h. No obvious cellular death rate was observed when the concentration of nanotubes was below 50 µg ml(-1). However, cells with FA-SWNT uptake showed a concentration-dependent apoptosis. These discoveries might be helpful for understanding the interaction of SWNTs and living cells.