Thallium(I) Oxidation by Permanganate and Chlorine: Kinetics and Manganese Dioxide Catalysis.

The oxidation of the toxic heavy metal thallium(I) (Tl(I)) is an efficient way to enhance Tl removal from water and wastewater. However, few studies have focused on the kinetics of Tl(I) oxidation in water, especially at environmentally relevant pH values. Therefore, the kinetics and mechanisms of Tl(I) oxidation by the common agents KMnO4 and HOCl under environmentally relevant pH condition were explored in the present study. The results indicated that the pH-dependent oxidation of Tl(I) by KMnO4 exhibited second-order kinetics under alkaline conditions (pH 8-10) with the main active species being TlOH, while the reaction could be characterized by autocatalysis at pH 4-6, and Mn(III) might also play an essential role in the MnO2 catalysis. Furthermore, a two-electron transfer mechanism under alkaline conditions was preliminarily proposed by using linear free energy relationships and X-ray photoelectron spectroscopy (XPS) analysis. Distinctively, the reaction rate of Tl(I) oxidation by HOCl decreased with increasing pH, and protonated chlorine might be the main active species. Moreover, the Tl(I)-HOCl reaction could be regarded as first order with respect to Tl(I), but the order with respect to HOCl was variable. Significant catalysis by MnO2 could also be observed in the oxidation of Tl(I) by HOCl, mainly due to the vacancies on MnO2 as active sites for sorbing Tl. This study elucidates the oxidation characteristics of thallium and establishes a theoretical foundation for the oxidation processes in thallium removal.

Retention of thallium(I) on goethite, hematite, and manganite: Quantitative insights and mechanistic study.

The reversibility of monovalent thallium (Tl) absorption on widely distributed iron/manganese secondary minerals may affect environmental Tl migration and global cycling. Nevertheless, quantitative and mechanistic studies on the interfacial retention and release reactions involving Tl(I) are limited. In this study, batch and stirred-flow experiments, unified kinetics modeling, spectral detection, and theoretical calculations were used to elucidate the retention behaviors of Tl(I) on goethite, hematite, and manganite with different solution pH values and Tl loading concentrations. Sustained Tl(I) retention (kd, MeOHTl=0.005∼0.018 min-1) was induced by hydration of the surface hydroxyl groups. Rapid Tl(I) retention (kd,MeOTlOH=1.232∼2.917 min-1) was enhanced by the abundant hydroxide ions and deprotonated hydroxyl groups, which increased the Tl(I) binding ability. Compared to the ambient Tl concentration, pH had a more substantial effect on the formation and distribution of surface Tl(I) binding species. In alkaline environments, the large adsorption energy for Tl(I) binding to surface species (Eads=-6.14 eV) induced fast Tl(I) binding response on the surfaces of iron/manganese secondary minerals. This study provides new insights into the heterogeneous surface complexation and retention behaviors of Tl(I) and contributes to an in-depth understanding of the environmental fate of Tl and the remediation of Tl contamination.

Thermodynamic and kinetic coupling modeling for thallium(I) sorption at a heterogeneous titanium dioxide interface.

The transformations of monovalent thallium (Tl) in an aqueous environment may be affected significantly by Tl(I) partitioning at the solid-water interface during sorption. Models used to quantify the kinetics of Tl(I) adsorption on heterogeneous adsorbents and formation of multiple complexes under a wide range of water chemistry conditions can accurately predict the environmental fate of thallium. In this study, Tl(I) sorption on representative titanium dioxide at different solution pH values and loading concentrations was investigated with two unified adsorption models, diffuse layer modeling and kinetics modeling. Three Tl(I) surface complexes, TiOTl, TiOHTl+, and TiOTlOH-, were used in the diffuse layer model and successfully described batch adsorption and the results of spectroscopic analyses. The contribution of TiOHTl+ to the adsorption capacity was much higher than those of TiOTl and TiOTlOH- under neutral and weakly alkaline conditions, while the species TiOTlOH- predominated among Tl(I) complexes in strongly alkaline environments. The adsorption and desorption rate coefficients derived from thermodynamics and kinetics coupling modeling suggested the influence of different complex characteristics on adsorption and desorption of Tl(I). Our results provide a comprehensive model for predicting the dynamic binding behavior of Tl at heterogeneous solid-water interfaces.

[Evaluation of in vivo labeled cytotoxic T lymphocytes and cytokine-induced killer cells migration and distribution of subcutaneous gastric tumor model in nude mice].

OBJECTIVE: To investigate the migration and distribution of CTL (cytotoxic T lymphocyte) and CIK (cytokine-induced killer) cells in gastric tumor model. METHODS: Subcutaneous gastric tumor model was established by BGC-823 cancer cells in nude mice. Both CTL and CIK cells were labeled with 99Tc(m) directly and then inoculated into nude mice with subcutaneous tumor by intravenous injection separately. Three mice of each group were evaluated by single-photon emission computerized tomography (SPECT) at 1 h, 6 h and 24 h post-inoculation. After SPECT imaging, 3 mice in each group were sacrificed and got samples of the tumor, liver, spleen, kidney, lung, intestine, etc. The tissue samples were weighed and radioactivity was determined with a well-type scintillation counter. The accumulation of labeled CTL and CIK cells in tissues were expressed as %ID/g (percentage activity of injection dose per gram of tissue) and T/NT (tumor/non-tumor) values were analyzed. RESULTS: The tracing of both cells in SPECT showed a clear migration path away from the injection point to solid tumor, and can be detected in all organs and tissues such as liver, spleen, kidney, lung and intestine, etc not long after injection. The %ID/g peak values of CTL in organs from the highest to the lowest were as follows: tumor (7.79 +/- 0.46), liver (4.12 +/- 0.51), intestine (2.71 +/- 0.16), kidney (1.44 +/- 0.25), spleen (1.24 +/- 0.12), kidney (1.12 +/- 0.11), and all the T/NTs were above 1. The %ID/g peak values of CIK cells in organs from the highest to the lowest were as follows: liver (6.64 +/- 0.67), tumor (5.47 +/- 0.87), intestine (3.55 +/- 0.23), kidney (2.34 +/- 0.41), spleen (1.45 +/- 0.17), lung (1.27 +/- 0.21), and T/NTs > 1 except for liver. After injection, the %ID/g values of tumor in CTL group were 2.35 +/- 0.28 (1 h), 4.58 +/- 0.52 (6 h) and 7.79 +/- 0.46 (24 h) respectively while the %ID/g values of tumor in CIK group 2.23 +/- 0.46 (1 h), 3.25 +/- 0.70 (6 h) and 5.47 +/- 0.87 (24 h) respectively. At 24 h point, the %ID/g of CTL in tumor was much higher than CIK cells (P < 0.05). CONCLUSION: The definite directional tumor-targeting capacity of CTL and CIK cells in tumor-bearing nude mice is promising.

Transport of Tl(I) in water-saturated porous media: Role of carbonate, phosphate and macromolecular organic matter.

Understanding the transport behaviors of thallium (Tl) in porous media is of considerable interest for both natural soils and artificial filtration removal of Tl. In this context, the transport behaviors of Tl(I) in water-saturated sand columns under different conditions were systematically investigated. It was found that, in addition to the effects of pH and ionic strength (IS), the transport of Tl(I) depended on the carbonate, phosphate and macromolecular organic matter as well. Tl(I) broken the columns more difficultly under higher pH and lower IS conditions. Moreover, the adsorption of carbonate and phosphate on sand surfaces may increase the retention of Tl(I) in columns. As for macromolecular organic matter, humic acid (HA) facilitated Tl(I) transport, especially under neutral and alkaline conditions (7.0 and 9.8), which was possibly associated with Tl-complexes formation and competed adsorption between Tl(I) and HA. However, bovine serum albumin (BSA) impeded Tl(I) transport for the reason that deposited BSA might provide more adsorption sites for Tl(I), though Tl(I) had a slight effect on BSA transport. In order to evaluate the mechanisms of transport, a dual-sites non-equilibrium model was applied to fit the breakthrough curves of Tl(I). Retardation factor (R) values of individual Tl(I) transport from model calculations were found to be higher than that of Tl(I) transport with HA and lower than that of Tl(I) transport with BSA. The fraction of instantaneous sorption sites (ß) was found to decrease with increasing pH, implying nonequilibrium sorption is a main sorption mechanism of Tl(I) with pH increasing. The fundamental data obtained herein demonstrated that carbonate, phosphate and macromolecular organic matter significantly influenced the Tl(I) migration and could lead to the leaking or bindings of Tl(I) at Tl-occurring sites.

[Experimental study of implantable engineered liver tissue using type I collagen gel as scaffold].

OBJECTIVE: To construct implantable engineered liver tissue (ELT) using type I collagen gel as scaffold. METHODS: Type I collagen was obtained from the tail of a rat. Hepatocytes were collected from a Sprague-Dawley rat, mixed with liquid type I collagen and Dulbecco's modified Eagle's medium to create hepatocyte/collagen gel construct. The construct was inoculated in a 96-well plate. 0, 3, 5, 7, 9, 11, 13, and 15 days after the inoculation the viability of hepatocytes in vitro was measured by MTT assay. Phase contrast microscopy was used to observe the morphology of the hepatocyte/collagen gel construct. Three SD rats underwent injection of the hepatocyte/collagen gel construct into the subcutaneous space. One week later the implant was taken out. The morphology was conducted by routine H.E. staining and immunohistochemical staining. The morphology and function of hepatocytes was investigated by inverted microscopy, routine H.E. staining and immunohistochemical staining. The constructs were also implanted into subcutaneous space, and the differentiation of hepatocytes and the formation of engineered liver tissue were observed by routine H.E. staining and immunohistochemical staining. RESULTS: Phase contrast microscopy showed that the hepatocytes were distributed evenly in the construct and remained round-shape throughout the in vitro culture. MTT assay demonstrated that the high viability of hepatocytes (87%) was maintained up to 7 days, and then decreased gradually. Albumin, the specific marker of hepatocytes remained positive by immunohistochemical staining after 15-day culture. One week after implantation into subcutaneous space, the implanted hepatocytes retained its hepatocyte-specific morphology, i.e. round shape, large nuclear/cytoplasm ratio as well as binuclear cells, and formed small engineered liver tissue containing blood vessels within and surrounding the tissue. CONCLUSION: A novel approach to construct implantable engineered liver tissue using collagen gel as scaffold for growth and differentiation of hepatocytes has been dev eloped. This technique is an attractive tool for the development of liver tissue engineering.

Protective effects of lidocaine injected into the hepatoduodenal ligament on warm ischemia-reperfusion injury to the rat liver.

BACKGROUND: Ischemia-reperfusion (IR) injury to the liver is still a critical and daunting problem in the field of hepatobiliary surgery. Ischemic preconditioning (IP) of the liver serves as an effective approach against IR injury. This study was to develop a novel procedure that could mimic IP, but might be more feasible than IP during surgery. METHODS: Eighty-two SD rats were randomly divided into 5 groups. L group (n = 21): 0.4% lidocaine (10 mg/kg) was injected into the hepatoduodenal ligament 10 minutes before a 40-minute hepatic IR. IP group (n = 16): a 5-minute ischemia was followed by a 10-minute reperfusion prior to a 40-minute hepatic IR. ILR group (n = 15): after a 40-minute ischemia of the liver, 0.4% lidocaine (10 mg/kg) was injected into the hepatoduodenal ligament 10 minutes prior to a 40-minute reperfusion of the liver. IR group (n = 15): the liver of the rat was subjected to a 40-minute IR. Control group (n = 15): 0.9% sodium chloride was injected into the hepatoduodenal ligament without other treatments. The levels of plasma alanine transaminase (ALT) and aspartate transaminase (AST) were determined for each group after treatment. RESULTS: The mean concentrations of ALT and AST were (379.80 +/- 141.69) U/L and (606.05 +/- 220.26) U/L for the L group, (334.64 +/- 141.94) U/L and (625.68 +/- 267.06) U/L for the IP group, (523.36 +/- 170.35) U/L and (765.47 +/- 238.45) U/L for the ILP group, (524.29 +/- 163.59) U/L and (764.63 +/- 246.79) U/L for the IR group, and (150.90 +/- 27.05) U/L and (298.15 +/- 47.68) U/L for the control group (standard error of the mean). CONCLUSION: A significant decrease in ALT and AST levels was observed in the L and IP groups when compared to the ILR and IR groups (P < 0.05), but no significant difference in ALT and AST levels was observed in the L group when compared to the IP group (P > 0.05). These results suggest that pretreatment with lidocaine injected into the hepatoduodenal ligament prior to IR provides effective protection against subsequent IR injury to the liver. The novel approach of blocking innervation with lidocaine mimics hepatic IP, but is more convenient than IP at the time of liver surgery.

[Analysis of the early and late gene expression of lipopolysaccharide activated macrophages by cDNA microarray].

OBJECTIVE: To study the early and late changes in mRNA expression in macrophages in response to lipopolysaccharide (LPS) with a cDNA microarray approach using the Clontech Atlas microarray. METHODS: mRNA was isolated from unstimulated control and LPS stimulated murine peritoneal macrophages at 2 hours and 24 hours poststimulation, converted to (33)P radiolabeled cDNA, and hybridized to mouse array membranes. RESULTS: In macrophages being stimulated for 2 hours, 69 out of 1 176 genes were found to differ by over 3-fold compared with the control. Among them 44 genes were up-regulated and 25 genes were down-regulated. In macrophages stimulated for 24 hours, 11 genes were up-regulated and 26 genes were down-regulated compared with the control. Only 8 genes were identified both at 2 hours and at 24 hours poststimulation. The expressions of many genes encoding transcription factor, cytokines, cell signaling modulators and apoptosis associated proteins were found to have changed. Some genes that were not previously linked to this model, such as bric-a-brac (BTB) and cap-n-collar(CNC) homology 1(BACH1), early growth response protein 2 (EGR2), E47 interaction protein 1 (EIP1), Ngfi-A binding protein 2 (NAB2), myeloblastosis oncogene-like protein (MYBL2), neurofibromatosis 1 (NF1), ciliarry neurotropic factor (CNTF) and semaphorin 4A (Sema4A). CONCLUSION: This study has allowed us to identify genes that may potentially be regulated by LPS at early and late phase in macrophages. These may contribute to better understanding of the mechanism underlying LPS or bacteria induced inflammatory and immune response following infection and trauma.

In vivo distribution and antitumor effect of infused immune cells in a gastric cancer model.

Adoptive cellular transfer has been employed for cancer immunotherapy, including patients with gastric cancer. However, little is known about the distribution of effector cells after their injection via different pathways. In this study, we used human gastric cancer cells (BGC823) tagged with enhanced green fluorescent protein (EGPF) to establish a subcutaneous gastric cancer model in nude mice. Cytokine-induced killer (CIK) cells and cytotoxic T lymphocytes (CTLs) were generated from human peripheral blood and labeled with red fluorescent PKH26. A portion of CIK cells was armed with CEA/CD3-bispecific single-chain antibody. When CIK cells were injected into nude mice with established subcutaneous gastric cancer via peritumoral (p.t.), intravenous (i.v.) and intraperitoneal (i.p.) infusion respectively, the distribution of cells was observed using a live fluorescence imaging system. We found that only a very small number of CIK cells could travel to the tumor site after i.p. or i.v. infusion, and they inhibited subcutaneous tumor growth in vivo only immediately following injection. In contrast, p.t. injection resulted in a significantly higher accumulation of CIK cells at the tumor site for 48 hours and mediated the greatest tumor inhibition compared with the other two injection methods. In addition, we compared the antitumor activity of CIK, CEA/CD3-bscAb-CIK and CTL cells in vitro and in vivo after p.t. injection. Among the three types of immune cells, CTLs demonstrated the strongest antitumor activity both in vitro and in vivo. CEA/CD3-bispecific single chain antibody could effectively link T lymphocytes and tumor cells expressing CEA, and resulted in significantly higher accumulation of CIK cells at the tumor site compared with the parental CIK cells. This study indicates that peritumoral injection of immune effector cells by minimally invasive surgical procedures represents an effective delivery method of adoptive cellular immunotherapy. Tumor-specific immune cells, such as CTLs, are a better choice of effector cells than CIKs in cellular immunotherapy. Furthermore, CD3+ immune cells armed with the CEA/CD3-bispecific single chain antibody could more effectively travel to and accumulate at the site of tumors expressing CEA, such as gastric cancer.

Dynamic tracing of immune cells in an orthotopic gastric carcinoma mouse model using near-infrared fluorescence live imaging.

Adoptive cellular immunotherapy (ACI) has been demonstrated to be a promising cancer therapeutic, however, the distribution of immune cells injected into a tumor-bearing body is unclear. In this study, we investigated the tumor-targeting capacity of cytokine-induced killer (CIK) cells and cytotoxic T lymphocytes (CTLs) in a human gastric carcinoma orthotopic mouse model using a near-infrared fluorescence imaging system. CIK cells and tumor-specific CTLs were prepared with the near-infrared fluorescent dye DiR. As expected, no significant change in the proliferation rate or antitumor activity of CIK cells and CTLs was noted after labeling with DiR. Furthermore, a gastric carcinoma orthotopic model was established using a fibrinogen-thrombin method in nude mice followed by intraperitoneal infusion of the labeled immune cells into nude mice with established gastric carcinoma. Dynamic tracing of the immune cells was performed using a fluorescence-based live imaging system. Concentrated fluorescence signals were observed for a minimum of two weeks at the tumor site in mice infused with either CIK cells or CTLs with a peak signal at 48 h. Notably, CTLs were more persistent at the tumor site and exhibited a more intense antitumor activity than CIK cells following infusion. These results provided visual evidence of the tumor-targeting capacity of immune cells in live animals.