Acid-functionalized Single-walled Carbon Nanotubes Research Articles

Polydispersed Acid-Functionalized Single-Walled Carbon Nanotubes Induced the Integrin-Associated Protein (CD47) and Basigin (CD147) Expression and Modulated the Antioxidant Gene Expression in Erythroid Cells in Mice

Polydispersed Acid-Functionalized Single-Walled Carbon Nanotubes Induced the Integrin-Associated Protein (CD47) and Basigin (CD147) Expression and Modulated the Antioxidant Gene Expression in Erythroid Cells in Mice

Poly-dispersed Acid-Functionalized Single-Walled Carbon Nanotubes (AF-SWCNTs) Are Potent Inhibitor of BCG Induced Inflammatory Response in Macrophages.

The present study is focused on the modulation of Mycobacterium bovis BCG-induced inflammatory response by poly-dispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs) in macrophages. Flow cytometric and confocal microscopy studies indicated that both BCG and AF-SWCNTs were efficiently internalized by RAW 264.7 and MH-S macrophage cell lines and were essentially localized in the cytoplasmic area. BCG-induced production of reactive oxygen species (ROS) and nitric oxide by the two cell lines was significantly inhibited by AF-SWCNTs. Using RT-PCR technique, a marked decline was observed in the expression of BCG-induced pro-inflammatory genes COX-2, iNOS, TNF-α, IL-6, and IL-1β upon treatment with AF-SWCNTs. Results of gelatin zymography indicated that the AF-SWCNTs treatment also induced a marked decline in BCG-induced release of matrix metalloproteinases MMP-2 and MMP-9 by the two macrophage cell lines. The anti-inflammatory effect of AF-SWCNTs in downregulating BCG-induced inflammatory response was further validated in murine peritoneal macrophages. Treatment with AF-SWCNTs led to a steep decline in BCG-induced NO production in murine peritoneal macrophages in vitro as well as in vivo. Peritoneal macrophages isolated from mice treated with BCG and AF-SWCNTs had a significantly lower intracellular expression of COX-2 as compared to the peritoneal macrophages derived from mice treated with BCG alone. Taken together, our results demonstrate a potent anti-inflammatory effect of AF-SWCNTs in alleviating BCG-induced inflammatory responses in macrophages in vitro and in vivo.

Toxicity of poly-dispersed single-walled carbon nanotubes on bone marrow derived Hematopoietic Stem and Progenitor Cells

This study has explored the effect of acid-functionalized single-walled carbon nanotubes (AF-SWCNTs) on Hematopoietic Stem and Progenitor Cell (HSPCs) in mouse bone marrow. Administration of AF-SWCNTs induced a significant decline in the live-cell recovery from bone marrow. Lin-negative Stem cell enriched HSPCs internalized AF-SWCNTs that remained localized in cytoplasmic areas. Incubation of HSPCs with AF-SWCNTs resulted in induction of cell death, inhibition of cell cycle, and induction of reactive oxygen species (ROS) as well as the expression of Caspase 3, 7 and 9 enzymes. In vitro culture with a cytokine cocktail (SCF, GM-CSF, IL3, IL6, IL7) induced differentiation of HSPCs into lymphocytes and myeloid cells, that was inhibited in presence of AF-SWCNTs. Relative recoveries of lymphocytes specifically B lymphocytes, was significantly reduced by AF-SWCNT-treatment, whereas the relative recovery of myeloid cells remained unaltered. These results suggest that AF-SWCNTs have significant toxic effects on HSPCs and differentially suppress the ontogeny of lymphoid and myeloid cells.

Poly dispersed acid-functionalized single walled carbon nanotubes target activated T and B cells to suppress acute and chronic GVHD in mouse model

Graft versus host disease (GVHD) results from hyper-activation of transplanted lymphocytes against the host antigens. Bone marrow transplantation in humans as well as some cases of blood transfusion and organ transplantation are associated with a strong GVH reaction resulting in GVHD that in many cases may be fatal. We had previously shown that poly-dispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs) specifically target activated T and B lymphocytes and kill them. In the present study, efficacy of AF-SWCNTs to suppress the GVH reaction was tested in the mouse model. Acute GVHD was induced in mice by administering intravenously 30 or 60 million spleen cells from a parental strain (C57bl/6 mouse, MHC haplotype H-2b) to host (C57bl/6 x Balb/c) F1 mice (MHC haplotype H-2b/d)and waiting for 8–10 days. Chronic GVHD was similarly induced by administration of 30 million parent spleen cells to F1 mice and waiting for a period of 60 days. Our results demonstrate a marked decline in splenomegaly and recovery of spleen T (both CD4 and CD8) and B cells in GVHD mice treated with AF-SWCNTs. AF-SWCNTs treatment also limited T and B cell proliferation by restricting S-phage of cell cycle. Generation of anti-host cytotoxic T cells (CTLs) was also markedly suppressed by AF-SWCNT treatment of acute GVHD mice, and a significant reduction in the generation of anti-host antibodies could also be demonstrated. Taken together, our results suggest that the AF-SWCNTs can be considered as a potential therapeutic agent for treating GVHD.

In vitro and in vivo modulation of Hematopoietic Stem Cell (HSCs) differentiation into T and B cells by poly dispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs)

Abstract Background AF-SWCNTs are known to have significant effect on the immune function. There is not much information available on the effect of carbon nanotubes (CNTs) on the differentiation of the HSCs. In the present study we have focused on studying the modulatory effects of AF-SWCNTs on the differentiation of HSCs into T & B cells. Methods Single-walled CNTs were acid-functionalized by treating with concentrated sulfuric & nitric acid; thus, tagged with Alexa Fluor 633 to get fluorescent AF-SWCNTs (FAF-SWCNTs). To study internalization, magnetic beads enriched C57bl/6 mouse bone marrow (BM) HSCs (Lin− Sca1+cKit+) were incubated with FAF-SWCNTs & studied using flow cytometry & confocal microscopy. HSCs were cultured with a cocktail of cytokines to induce differentiation to T & B cells, in (+/−) AF-SWCNTs & monitored by live cell imaging. For in vivo ontogenesis study, mice were lethally irradiated (gamma irradiation) & reconstituted using syngeneic BM cells pretreated (+/−) AF-SWCNTs. At different time points, appearance of T & B cells in the spleen was monitored. Results Our results indicate that HSCs internalized significant amounts of FAF-SWCNTs in vitro that remained essentially localized in cytoplasm. Differentiation of cytokines stimulated HSCs to T & B cell was significantly suppressed by AF-SWCNTs. Results of our in vivo experiments indicated that after 17th day of BM transplantation, significant numbers of T & B cells appeared in the reconstituted mouse spleen. However, when AF-SWCNTs pretreated BM cells used to reconstitute irradiated mice, significant decline in both of their percentage & absolute recovery was noted. These results indicate that CNTs may significantly modulate the differentiation of HSCs into lymphocytes.

Acid-functionalized single-walled carbon nanotubes alter epithelial tight junctions and enhance paracellular permeability

Due to their unique properties, carbon nanotubes (CNTs) are being widely explored for industrial and medical applications. This has necessitated a thorough assessment of the effect of CNTs on human and animal physiology and health. Impact of CNTs on epithelial tight junctions has not been evaluated in the context of their toxic effects in many biological systems. In the present study, we examined the effect of acid functionalized single-walled carbon nanotubes (AF-SWCNTs) on the function and expression of two tight junction proteins (ZO-1 and occludin) in the Madin-Darby canine kidney (MDCK) cell line. Treatment of MDCK cells with AF-SWCNT resulted in a downregulation of tight junction proteins, decreased trans-epithelial electrical resistance (TER), increased paracellular permeability, and disruption of tight junctions. Taken together, our data demonstrate that AF-SWCNT disrupts tight junction barrier by downregulating tight junction proteins in MDCK epithelial cells.

Enhanced antibody response to ovalbumin coupled to poly-dispersed acid functionalized single walled carbon nanotubes

Activated mouse B cells as compared to the resting B cells are known to internalize substantially more acid-functionalized single walled carbon nanotubes (AF-SWCNTs). It was hypothesized that the antigens coupled to AF-SWCNTs would also be taken up more efficiently by B cells. Further the enhanced uptake of the antigen by B cells may facilitate antigen presentation by B cells resulting in a better antibody response. Aim of this study was to test this hypothesis. Ovalbumin was chemically coupled to AF-SWCNTs that yielded a coupled product that had 0.08% of all carbon atoms in AF-SWCNTs occupied by ovalbumin. Coupling of ovalbumin to AF-SWCNTs was confirmed by staining the product with anti-ovalbumin antibodies. B cells incubated with ovalbumin-AF-SWCNT internalized more ovalbumin than the B cells incubated with free ovalbumin. Groups of mice were immunized subcutaneously with (a) free ovalbumin, (b) free ovalbumin and AF-SWCNTs at two different subcutaneous sites respectively on mice, and (c) ovalbumin-AF-SWCNT coupled product. In each case a primary immunization was followed by three weekly booster doses. It was found that the anti-ovalbumin antibody response assessed by ELISA, was highest in the group where ovalbumin coupled to AF-SWCNTs was used for immunization (p < 0.001). Antibody response in ovalbumin-AF-SWCNT group was comparable to the group where ovalbumin was used for immunization using complete and incomplete Freund’s adjuvant (primary and secondary immunizations respectively). We propose that AF-SWCNTs could be explored as an adjuvant to improve the antibody response especially in vaccine development.

Elevated internalization and cytotoxicity of polydispersed single-walled carbon nanotubes in activated B cells can be basis for preferential depletion of activated B cells in vivo

Uptake of polydispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs) in resting and LPS-activated B cells was studied using fluorescence-tagged AF-SWCNTs (FAF-SWCNTs). Activated B cells internalized substantially higher amounts of FAF-SWCNTs [76.5% AF-SWCNT+ B cells, mean fluorescence intensity (MFI) 720.6] as compared to the resting B cells [39.5% AF-SWCNT+ B cells, MFI 198.5]. B cells in S and G2/M phases were found to have significantly higher uptake of FAF-SWCNTs as compared to cells in G0/G1 phase. Confocal microscopy indicated that AF-SWCNTs were essentially localized on cell membrane in resting B cells, whereas in activated B cells, AF-SWCNTs were distributed throughout the cytoplasm. Targeting of AF-SWCNTs specifically to activated B cells in vivo was examined by first administering intravenously LPS-activated B cells tagged with fluorescence tracer (CFSE) in mice, followed by FAF-SWCNTs through the same route. It was found that FAF-SWCNTs were specifically taken up by CFSE+CD19+-activated B cells (95% FAF-SWCNT+ B cells, MFI 3725) as compared to CFSE− CD19+ resting B cells (31.1% FAF-SWCNT+ B cells, MFI 428). Administration (i.v.) of LPS resulted in a significant increase in the proportion of B cell in mouse spleen that was reduced by 68% by administering AF-SWCNTs. In control mice, the corresponding decrease in B cell proportion was 49%, which was significantly lower (p < 0.005) than the decline in LPS-treated mice. These results indicate that AF-SWCNTs may have the potential as an agent for depleting activated B cells in vivo.

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method.

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination.

Uptake of poly-dispersed single-walled carbon nanotubes and decline of functions in mouse NK cells undergoing activation

The interaction of poly-dispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNT) with NK cells undergoing activation was examined. Exposure to AF-SWCNT during NK activation in vitro by interleukin (IL)-2, and in vivo by Poly(I:C) significantly lowered cytotoxic activity generated against YAC-1 tumor cells. Recoveries of spleen NK1.1+ cells as well as the activated subset of NK cells (NK1.1+CD69+ cells) were significantly reduced by the AF-SWCNT exposure. The proportion of apoptotic NK cells (NK1.1+ phosphatidylserine+) in the spleen cell preparations activated in vitro was also significantly elevated. Expression levels of CD107a [for assessing NK cell degranulation] as well as of FasL marker [mediating non-secretory pathway of NK cell killing] were significantly lower in cells exposed to AF-SWCNT during the activation phase. Intracellular levels of interferon (IFN)-γ and tumor necrosis factor (TNF)-α in the cells were also significantly reduced. Fluorescent AF-SWCNT (FAF-SWCNT) were internalized by the NK cells and uptake was significantly greater in activated cells. Confocal microscopy indicated the internalized FAF-SWCNT were localized to the cytoplasm of the NK cells. These results indicated that AF-SWCNT were internalized by NK cells and caused a general down-regulation of a variety of parameters associated with NK cell cytotoxicity and other cellular functions.

Hyaluronic acid-functionalized single-walled carbon nanotubes as tumor-targeting MRI contrast agent.

A tumor-targeting carrier, hyaluronic acid (HA)-functionalized single-walled carbon nanotubes (SWCNTs), was explored to deliver magnetic resonance imaging (MRI) contrast agents (CAs) targeting to the tumor cells specifically. In this system, HA surface modification for SWCNTs was simply accomplished by amidation process and could make this nanomaterial highly hydrophilic. Cellular uptake was performed to evaluate the intracellular transport capabilities of HA-SWCNTs for tumor cells and the uptake rank was HA-SWCNTs> SWCNTs owing to the presence of HA, which was also evidenced by flow cytometry. The safety evaluation of this MRI CAs was investigated in vitro and in vivo. It revealed that HA-SWCNTs could stand as a biocompatible nanocarrier and gadolinium (Gd)/HA-SWCNTs demonstrated almost no toxicity compared with free GdCl3. Moreover, GdCl3 bearing HA-SWCNTs could significantly increase the circulation time for MRI. Finally, to investigate the MRI contrast enhancing capabilities of Gd/HA-SWCNTs, T1-weighted MR images of tumor-bearing mice were acquired. The results suggested Gd/HA-SWCNTs had the highest tumor-targeting efficiency and T1-relaxivity enhancement, indicating HA-SWCNTs could be developed as a tumor-targeting carrier to deliver the CAs, GdCl3, for the identifiable diagnosis of tumor.

Selective loss of younger erythrocytes from blood circulation and changes in erythropoietic patterns in bone marrow and spleen in mouse anemia induced by poly-dispersed single-walled carbon nanotubes

Administration of poly-dispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs, 10 µg intravenously on alternate days) induced a sustained anemia in mice. Using a modified double in vivo biotinylation (DIB) technique, blood counts of reticulocytes and erythrocytes of different age groups were simultaneously enumerated in control and AF-SWCNT treated mice. A sustained reticulocytosis was observed in AF-SWCNT treated mice. Young erythrocytes (up to 7 days old) that are normally resistant to elimination in control mice were eliminated at a significant rate in AF-SWCNT treated mice. Old erythrocytes, however, accumulated in circulation indicating that younger erythrocytes were selectively eliminated from the blood circulation of AF-SWCNT treated mice. Cells representing various stages of erythroid differentiation in bone marrow and spleen were enumerated flow cytometrically by double staining with anti-Ter119 and anti-transferrin receptor (CD71) monoclonal antibodies. Proportion of erythroid cells was significantly reduced (up to 27%) in bone marrow (BM) indicating a fall in erythropoietic activity. A concomitant increase in the spleen erythroid population was however observed that could be a compensatory response. Changes in erythroid populations in bone marrow and spleen correlated with changes in erythroblast-A population in these organs that represent an early stage of erythroid differentiation. Uptake of intravenously administered fluorescence tagged AF-SWCNTs (FAF-SWCNTs) was relatively low (3–4%) in erythroid cells in bone marrow and spleen. A significantly higher proportion of pro-erythroblasts and erythroblast-A (early stages of erythroid differentiation) took-up FAF-SWCNTs. Uptake of AF-SWCNTs by early precursors of erythroid differentiation with toxic consequences may be a contributing factor in AF-SWCNT induced anemia.

Lipid antigen presentation through CD1d pathway in mouse lung epithelial cells, macrophages and dendritic cells and its suppression by poly-dispersed single-walled carbon nanotubes

Effect of poly-dispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs) was examined on lipid antigen presentation through CD1d pathway on three cell lines, LA4, MHS, and JAWSII used as prototype antigen presenting cells (APCs). CD1d molecule was expressed on 80–90% MHS (prototype macrophages) and JAWSII (prototype dendritic cells) cells whereas <5% LA4 cells (lung epithelial cells, non-classical APCs) expressed CD1d. Treatment with AF-SWCNTs but not with pristine SWCNTs resulted in a significant decline in the level of CD1d mRNA as well as mRNA levels of some other intracellular proteins involved in lipid antigen presentation pathway (MTP, ApoE, prosaposin, SR-BI and LDLr). Lipid antigen presentation was assessed by first incubating the cells with a prototype lipid antigen (α-Glactosylceramide or αGC) and then staining with L363 monoclonal antibody that detects αGC bound to CD1d molecule. While 100% MHS and JAWSII cells presented αGC, only 20% LA4 cells presented the CD1d antigen. Treatment with AF-SWCNTs resulted in a 30–40% decrease in αGC antigen presentation in all three cell lines. These results show that AF-SWCNT treatment down regulated the lipid antigen presentation pathway in all three cell lines and significantly lowered the ability of these cell lines to present αGC antigen.

Modulation of erythropoiesis and erythrocytes turnover in mice in response to acid functionalized single walled carbon nanotubes (AF-SWCNTS) treatments

Carbon nanotubes (CNTs) have wide applications in cosmetics, sunscreens and for systemic delivery of drugs and gene delivery (Aitken et al., 2006. Occup. Med. 56, 300). The toxic effects of acid functionalized single walled carbon nanotubes (AF-SWCNTs) on LA4 lung epithelial cell line (Saxena et al., 2007. Nanotoxicology 1, 291) and erythrocytes (Sachar and Saxena, 2011. PLOS ONE 6(7), e22032) have been reported. The aim of present study was to study the effect of AF-SWCNTs treatment on different aged erythrocytes and erythropoietic responses in bone marrow and spleen in C57Bl/6 mice. A newly developed double in vivo biotinylation (DIB) technique was used to assess the effect of AF-SWCNTs on different aged erythrocytes (Khandelwal and Saxena, 2006. Exp. Gerontol. 41, 855). Various stages of erythrocyte differentiation in bone marrow and spleen were enumerated by using double staining of bone marrow cells with Ter119 (Glycophorin) and CD71 (Transferrin) monoclonal antibodies followed by flow cytometric analysis (Marinkovic et al., 2007. J. Clin. Investig. 117, 2133). Mice were repeatedly treatedwith 10 gAF-SWCNTs intravenously. Our results show that AF-SWCNTs treatment induced a sustained anemia and reticulocyte production in mice. An accelerated loss of young (ranges 4–15%) and intermediate aged erythrocytes young (upto 22%) occurred at different time points. Erythroid populations in bone marrow in AF-SWCNTs treated mice show a steep fall in (upto 27%) of erythroid cells in bone marrow. Contrary to bone marrow, the proportion of erythroid cells increased significantly (upto 26%) in spleens of AF-SWCNTs treated mice.

Inhibition of CD1d pathways of antigen presentation by acid functionalized single-walled carbon nanotubes (AF-SWCNTS) in professional and non-professional antigen presenting cells

Inhibition of CD1d pathways of antigen presentation by acid functionalized single-walled carbon nanotubes (AF-SWCNTS) in professional and non-professional antigen presenting cells

Assembly of Acid-Functionalized Single-Walled Carbon Nanotubes at Oil/Water Interfaces

The efficient segregation of water-soluble, acid-functionalized, single-walled carbon nanotubes (SWCNTs) at the oil/water interface was induced by dissolving low-molecular-weight amine-terminated polystyrene (PS-NH2) in the oil phase. Salt-bridge interactions between carboxylic acid groups of SWCNTs and amine groups of PS drove the assembly of SWCNTs at the interface, monitored by pendant drop tensiometry and laser scanning confocal microscopy. The impact of PS end-group functionality, PS and SWCNT concentrations, and the degree of SWCNT acid modification on the interfacial activity was assessed, and a sharp drop in interfacial tension was observed above a critical SWCNT concentration. Interfacial tensions were low enough to support stable oil/water emulsions. Further experiments, including potentiometric titrations and the replacement of SWCNTs by other carboxyl-containing species, demonstrated that the interfacial tension drop reflects the loss of SWCNT charge as the pH falls near/below the intrinsic carboxyl dissociation constant; species lacking multivalent carboxylic acid groups are inactive. The trapped SWCNTs appear to be neither ordered nor oriented.

Rapid and sensitive stripping voltammetric analysis of methyl parathion in vegetable samples at carboxylic acid-functionalized SWCNTs–β-cyclodextrin modified electrode

A rapid, sensitive and enzymeless methyl parathion (MP) electrochemical sensor based on carboxylic acid-functionalized single-walled carbon nanotubes–β-cyclodextrin modified glassy carbon electrode (ƒ-SWCNT–β-CD/GCE) was successfully constructed for the trace analysis of MP in vegetable samples. Cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy were utilized to characterize the properties of the modified electrode. Experimental parameters such as preconcentration time, pH value, and the concentration of ƒ-SWCNT and β-CD were optimized. The proposed electrode displayed excellent electrocatalytic activity towards MP. The calibration curve for MP was obtained in both ranges of 0.002–0.02μgmL−1 and 0.02–17.5μgmL−1, with a low detection limit (S/N=3) of 0.4ngmL−1 after a very short preconcentration time for 80s. The modified electrode exhibited fast current response, high sensitivity, good reproducibility, and satisfactory anti-interference ability, and also successfully employed for the trace analysis of MP in vegetables samples. Satisfactory results revealed that this proposed electrochemical sensor can provide a promising candidate for the trace analysis of MP in agricultural and environmental samples.

Voltammetric sensing of bisphenol A based on a single-walled carbon nanotubes/poly{3-butyl-1-[3-(N-pyrrolyl)propyl] imidazolium ionic liquid} composite film modified electrode

Using carboxylic acid-functionalized single walled carbon nanotubes (SWCNTs-COO−) as an anion and 3-butyl-1-[3-(N-pyrrolyl)propyl]imidazolium as a cation, a novel SWCNTs-COO-ionic liquid (SWCNTs-COO-IL) nanocomposite was fabricated successfully. The as-prepared SWCNTs-COO-IL nanocomposite was confirmed with transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis, FTIR and Raman spectroscopy. The SWCNTs-COO-IL nanocomposite was coated onto a glassy carbon electrode surface followed by cyclic voltammetric scanning to fabricate a SWCNTs/poly{3-butyl-1-[3-(N-pyrrolyl)propyl] imidazolium ionic liquid} composite film modified electrode (SWCNTs/Poly-IL/GCE). Scanning electron microscope and electrochemical impedance spectroscopy were used to characterize SWCNTs/Poly-IL/GCE. Electrochemical behaviors of bisphenol A (BPA) at the SWCNTs/Poly-IL/GCE were investigated thoroughly. It was found that an obvious oxidation peak appeared without reduction peak in the reverse scanning, indicating an irreversible electrochemical process. The oxidation peak currents of BPA were linearly related to scan rate in the range of 20–300mVs−1, suggesting an adsorption controlled process rather than a diffusion controlled process. Differential pulse voltammetry was employed for the voltammetric sensing of BPA. Experimental conditions such as film thickness, pH value, accumulation potential and time that influence the analytical performance of the SWCNTs/Poly-IL/GCE were optimized. Under optimal conditions, the oxidation peak current was linearly related to BPA concentration in the range of 5.0×10−9 to 3.0×10−5molL−1 with a detection limit of 1.0×10−9molL−1 (S/N=3). The developed method was successfully employed for the determination of BPA leaching from plastic drinking bottle.

Single-walled carbon nanotubes and graphene oxides induce autophagosome accumulation and lysosome impairment in primarily cultured murine peritoneal macrophages

The wide application of carbon nanomaterials in various fields urges in-depth understanding of the toxic effects and underlying mechanisms of these materials on biological systems. Cell autophagy was recently recognized as an important lysosome-based pathway of cell death, and autophagosome accumulation has been found to be associated with the exposure of various nanoparticles, but the underlying mechanisms are still uncertain due to the fact that autophagosome accumulation can result from autophagy induction and/or autophagy blockade. In this study, we first evaluated the toxicity of acid-functionalized single-walled carbon nanotubes and graphene oxides, and found that both carbon nanomaterials induced adverse effects in murine peritoneal macrophages, and GOs were more potent than AF-SWCNTs. Both carbon nanomaterials induced autophagosome accumulation and the conversion of LC3-I to LC3-II. However, degradation of the autophagic substrate p62 protein was also inhibited by both nanomaterials. Further analyses on lysosomes revealed that both carbon nanomaterials accumulated in macrophage lysosomes, leading to lysosome membrane destabilization, which indicates reduced autophagic degradation. The effects of AF-SWCNTs and GOs on cell autophagy revealed by this study may shed light on the potential toxic mechanism and suggest caution on their utilization.

Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) composite electrode as sensing platform for the simultaneous electrochemical determination of dihydroxybenzene isomers

Dihydroxybenzene isomers catechol (CC), resorcinol (RC), and hydroquinone (HQ) were simultaneously determined using a simple, inexpensive, water-stable, and conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite sensing electrode by linear sweep voltammetry. The sensing electrode was prepared by dip-coating a mixture of PEDOT:PSS, Nafion, and carboxylic acid-functionalized single-walled carbon nanotubes on a gold electrode, then modifying by electrochemical doping in a hydrophobic ionic liquid. Nafion was selected as a binding agent to improve the adhesion and binding force between films and electrode interface, and ionic liquid was employed to improve the conductivity and water resistance of the composite electrode. The as-proposed sensing electrode displayed excellent electrochemical catalytic activities towards CC, RC, and HQ. Large peak separations were obtained between HQ and CC as well as CC and RC, i.e., up to 109 and 496 mV, respectively. The calibration curves for CC, RC, and HQ were obtained in the ranges of 0.56–70, 0.18–50, and 0.56–50 μM, with detection limits (S/N = 3) of 0.19, 0.08, and 0.20 μM, respectively. Finally, the sensing electrode was applied to river water sample analysis with reliable recovery. Satisfactory results revealed that the PEDOT:PSS composite can provide a promising platform for the design and application of sensing devices.