Browsing by Author "Mitra, Somenath"

Now showing 1 - 4 of 4
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    Comparative Proteomics and Biological Effects of Functionalized Carbon Nanotubes in Intestinal Cell Co-culture
    (Office of the Vice Chancellor for Research, 2011-04-08) Lai, Xianyin; Fang, Meixian; Fears, Sharry; Mitra, Somenath; Ringham, Heather; Witzmann, Frank A.
    “Carbon nanotubes (CNTs) possess unique electrical, mechanical, and thermal properties, with potential applications in the electronics, catalysts, polymer composites, aerospace, and other industries. CNTs are also being developed for a broad range of applications in biomedicine, including oral drug delivery. Functionalized, water dispersible CNTs (fCNTS) can be expected to enter the digestive tract and exert biological effects on its barrier epithelial cells. To characterize these effects, we developed an in vitro model of the large intestinal tract using a coculture of Caco-2 (75%) and HT29-MTX (25%, mucus secreting) cells, and exposed these cells to functionalized single-walled (SWNT) and multi-walled (MWNT) carbon nanotubes at realistic concentrations (500 pg/mL and 10 µg/mL; 48 h). Protein expression was analyzed using our recently developed label-free quantitative mass spectrometry (LFQMS) platform, IdentiQuantXL™, while typical toxicological endpoint assays were used to characterize various cellular responses. LFQMS identified 5,007 unique protein database entries, from which 4,200 proteins were considered qualified for quantitation. These proteins represented 1,978 protein groups (containing isoforms, splice-variants, etc). Differences in expression were calculated by ANOVA (P<0.001) and post hoc Holm Sidak comparisons (P<0.05). fCNT significantly altered protein expression in a moderate number of proteins, the extent and type of which were fCNT specific. Only 13 proteins were universally altered by all exposures (except 500 pg/mL COOHSWNT which had no effect), and these represent a broad range of cellular functions. Bioinformatic analysis using the Gene Ontology Database and Ingenuity Pathway Analysis revealed statistically significant protein associations with a broad range of functional networks and signaling/metabolic pathways. Again, little overlap between fCNT was observed. None of the exposures was associated with overt toxicity or proinflammatory response. The results suggest that significant biological effects result from fCNT exposure, responses that are specific to CNT-type and dose, but occurring in the absence of toxicity or irritation. Supported by NIEHS RC2ES018810.”
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    Comparison of Nanotube–Protein Corona Composition in Cell Culture Media
    (Wiley, 2013) Shannahan, Jonathan H.; Brown, Jared M.; Chen, Ran; Ke, Pu Chun; Lai, Xianyin; Mitra, Somenath; Witzmann, Frank A.; Cellular and Integrative Physiology, School of Medicine
    In biological environments, nanomaterials associate with proteins forming a protein corona (PC). The PC may alter the nanomaterial's pharmacokinetics and pharmacodynamics, thereby influencing toxicity. Using a label-free mass spectrometry-based proteomics approach, the composition of the PC is examined for a set of nanotubes (NTs) including unmodified and carboxylated single- (SWCNT) and multi-walled carbon nanotubes (MWCNT), polyvinylpyrrolidone (PVP)-coated MWCNT (MWCNT-PVP), and nanoclay. NTs are incubated for 1 h in simulated cell culture conditions, then washed, resuspended in PBS, and assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) for their associated PC. To determine those attributes that influence PC formation, the NTs are extensively characterized. NTs had negative zeta potentials in water (SWCNT-COOH < MWCNT-COOH < unmodified NTs) while carboxylation increases their hydrodynamic sizes. All NTs are also found to associate a common subset of proteins including albumin, titin, and apolipoproteins. SWCNT-COOH and MWCNT-COOH are found to bind the greatest number of proteins (181 and 133 respectively) compared to unmodified NTs (<100), suggesting covalent binding to protein amines. Modified NTs bind a number of unique proteins compared to unmodified NTs, implying hydrogen bonding and electrostatic interactions are involved in PC formation. PVP-coating of MWCNT did not influence PC composition, further reinforcing the possibility of hydrogen bonding and electrostatic interactions. No relationships are found between PC composition and corresponding isoelectric point, hydropathy, or aliphatic index, implying minimal roles of hydrophobic interaction and pi-stacking.
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    Protein expression profiles of intestinal epithelial co-cultures: effect of functionalised carbon nanotube exposure
    (Inderscience, 2013) Lai, Xianyin; Blazer-Yost, Bonnie L.; Clack, James W.; Fears, Sharry L.; Mitra, Somenath; Ntim, Susana Addo; Ringham, Heather N.; Witzmann, Frank A.; Cellular and Integrative Physiology, School of Medicine
    To assess the biological effects of low level, water dispersible, functionalised carbon nanotube (f-CNT) exposure in an in vitro model simulating the digestive tract, cellular protein expression was quantified and compared using label-free quantitative mass spectrometry (LFQMS). Co-cultured cells were exposed to well-characterised SWCNT-COOH, MWCNT-COOH, and MWCNT-PVP. The relative expression of 2,282 unique proteins was compared across the dose groups. 428 proteins were found to be differentially expressed. At the high dose, the extent of differential protein expression was CNT-specific and directly related to CNT colloidal stability. Cells responded to low level MWCNT-PVP exposure with three-fold greater differential expression. Bioinformatic analysis indicated significant and f-CNT-specific effects on relevant molecular and cellular functions and canonical pathways, with little overlap across f-CNT type and in the absence of overt toxicity.
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    Size dependent aqueous dispersibility of carboxylated multiwall carbon nanotubes
    (Royal Society of Chemistry, 2012) Ntim, Susana Addo; Sae-Khow, Ornthida; Desai, Chintal; Witzmann, Frank A.; Mitra, Somenath; Cellular and Integrative Physiology, School of Medicine
    The size dependent colloidal behavior of aqueous dispersions of carboxylated multiwall carbon nanotubes (c-MWCNTs) is presented. The presence of carboxylic groups provided electrostatic stabilization in water, where the size affected agglomeration. While aspect ratio did not show any definite correlation, the hydrophobicity indices (HI), zeta potential and aggregation kinetics showed dependence on the length of the c-MWCNTs where the shorter c-MWCNTs showed significantly lower HI values, smaller particle aggregates, higher zeta potential values and higher critical coagulation concentrations (ccc) in the presence of electrolytes. Although the diameter of the short c-MWCNTs did not appear to influence their aggregation behavior, the longer c-MWCNTs showed a dependence on diameter where stability decreased with increasing CNT diameter.