The translocation of single-walled carbon nanotubes (SWNTs) across MCF7 breast cancer cells was demonstrated with radioisotope labeling. Hybrids of SWNT−RNA polymer poly(rU) were formed through a nonspecific binding mechanism which could allow for the dissociation of the poly(rU) from the SWNTs upon delivery. The cellular uptake of the hybrids was examined by confocal fluorescence microscopy. Through cell growth and MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assays, we showed the negligible cytotoxicity of SWNTs (up to 0.5 mg/mL) to MCF7 cells.

Single-walled carbon nanotubes (SWNTs), being hydrophobic by nature, aggregate in water to form large bundles. However, isolated SWNTs possess unique physical and chemical properties that are desirable for sensing and biological applications. Conventionally isolated SWNTs can be obtained by wrapping the tubes with biopolymers or surfactants. The binding modes proposed for these solubilization schemes, however, are less than comprehensive. Here we characterize the efficacies of solubilizing SWNTs through various types of phospholipids and other amphiphilic surfactants. Specifically, we demonstrate that lysophospholipids, or single-chained phospholipids offer unprecedented solubility for SWNTs, while double-chained phospholipids are ineffective in rendering SWNTs soluble. Using transmission electron microscopy (TEM) we show that lysophospholipids wrap SWNTs as striations whose size and regularity are affected by the polarity of the lysophospholipids. We further show that wrapping is only observed when SWNTs are in the lipid phase and not the vacuum phase, suggesting that the environment has a pertinent role in the binding process. Our findings shed light on the debate over the binding mechanism of amphiphilic polymers and cylindrical nanostructures and have implications on the design of novel supramolecular complexes and nanodevices.

The specific contribution of interleukin-17/interleukin-17 receptor (IL-17/IL-17R)-mediated responses in regulating host susceptibility against obligatory intracellular Chlamydia infection was investigated in C57BL/6 and C3H/HeN mice during Chlamydia muridarum respiratory infection. We demonstrated that Chlamydia stimulated IL-17/IL-17R-associated responses in both Chlamydia-resistant C57BL/6 and Chlamydia-susceptible C3H/HeN mice. However, C3H/HeN mice developed a significantly greater IL-17/IL-17R-associated response than C57BL/6 mice did. This was reflected by an increase in IL-17 mRNA expression, a higher recall IL-17 production from splenocytes upon antigen restimulation, and higher production of Chlamydia trachomatis is an obligate intracellular gram-negative bacterium that primarily infects epithelial cells lining the ocular, respiratory, and urogenital tract surfaces and causes many human diseases including trachoma, pneumonia, and pelvic inflammatory disease (2). Although effective antibiotics are available, the incidence of C. trachomatis infections continues to increase worldwide (41). In the United States alone, it is estimated that there are approximately 2.8 million new cases of urogenital C. trachomatis infection each year (58). An effective and safe Chlamydia vaccine is needed to address the global C. trachomatis epidemic, and a comprehensive understanding of the means of protective immunity and immunopathology of C. trachomatis infection is essential for vaccine development.C. trachomatis infection results in a wide variety of clinical manifestations, ranging from asymptomatic to mild or severe symptoms, acute or chronic inflammatory responses, and a wide range of chronic complications (5,47,59). Host genetic factors appear to be important in determining the outcome of Chlamydia infections. It has been reported that the increased incidence of Chlamydia-induced chronic diseases, such as tubal infertility and scarring trachoma, is correlated with certain human leukocyte antigen (HLA) haplotypes and polymorphism of genes encoding interleukin-10 (IL-10), CD14, and tumor necrosis factor alpha (6,7,16,25,44,54). However, how these specific genes are involved in shaping the specific immune responses during Chlamydia infection in humans remains unclear. As in humans, inbred mouse strains, such as, and DBA/2J (H-2 d ) mice respond to respiratory (1,39,40,63), genital (9-12, 52), and intraperitoneal (i.p.) (36) Chlamydia infections differently. C57BL/6 mice are regarded as a resistant strain, whereas BALB/c, DBA/2, and C3H/HeN mice are reported as susceptible strains with higher mortality, more prolonged bacterial burden, more severe tissue inflammatory responses (such as neutrophil infiltration), and higher rates of infertility following Chlamydia infection. Thus, these inbred mouse strains have been used extensively for identification of specific host factors that regulate immune responses and immune mechanisms underlying the pathogenesis of Chlamydia infection.Based on animal models (5,8,38,50) and hum...

Articles you may be interested inQuantitative determination of the lateral density and intermolecular correlation between proteins anchored on the membrane surfaces using grazing incidence small-angle X-ray scattering and grazing incidence X-ray fluorescence Single-walled carbon nanotubes ͑SWNTs͒ and lysophospholipids readily assemble into supramolecular complexes in aqueous solutions. Upon light excitation the fluorescence of rhodamine-labeled lysophospholipids was redshifted and quenched due to the optical absorption of the SWNTs. Utilizing fluorescence energy transfer, the authors detected the translocation and disassembly of SWNT complexes in MCF breast cancer cells. These lipid-coated SWNT complexes enable drugs to be delivered at an effective dose and their subsequent release to be monitored in real time.

Bacteria, yeast and human cancer cells possess mechanisms of mutagenesis upregulated by stress responses. Stress-inducible mutagenesis potentially accelerates adaptation, and may provide important models for mutagenesis that drives cancers, host pathogen interactions, antibiotic resistance and possibly much of evolution generally. In Escherichia coli repair of double-strand breaks (DSBs) becomes mutagenic, using low-fidelity DNA polymerases under the control of the SOS DNA-damage response and RpoS general stress response, which upregulate and allow the action of error-prone DNA polymerases IV (DinB), II and V to make mutations during repair. Pol IV is implied to compete with and replace high-fidelity DNA polymerases at the DSB-repair replisome, causing mutagenesis. We report that up-regulated Pol IV is not sufficient for mutagenic break repair (MBR); damaged bases in the DNA are also required, and that in starvation-stressed cells, these are caused by reactive-oxygen species (ROS). First, MBR is reduced by either ROS-scavenging agents or constitutive activation of oxidative-damage responses, both of which reduce cellular ROS levels. The ROS promote MBR other than by causing DSBs, saturating mismatch repair, oxidizing proteins, or inducing the SOS response or the general stress response. We find that ROS drive MBR through oxidized guanines (8-oxo-dG) in DNA, in that overproduction of a glycosylase that removes 8-oxo-dG from DNA prevents MBR. Further, other damaged DNA bases can substitute for 8-oxo-dG because ROS-scavenged cells resume MBR if either DNA pyrimidine dimers or alkylated bases are induced. We hypothesize that damaged bases in DNA pause the replisome and allow the critical switch from high fidelity to error-prone DNA polymerases in the DSB-repair replisome, thus allowing MBR. The data imply that in addition to the indirect stress-response controlled switch to MBR, a direct cis-acting switch to MBR occurs independently of DNA breakage, caused by ROS oxidation of DNA potentially regulated by ROS regulators.

The conformational changes of a 22 base-pair double-stranded DNA, anchored via one end to a quartz substrate, have been characterized using a single-pair fluorescence resonance energy transfer technique. Base-pair mismatch, a major form of DNA damage, has been found to decrease the energy transfer between a fluorescence donor and an acceptor attached to the two ends of DNA molecules with 3 and 7 mismatches, by 4.4% and 10.4%, respectively, as compared to that for perfectly matched DNA. This result suggests that the disruption of the hydrogen bonds in damaged DNA leads to increased contour length and improved flexibility.

Copy-number variations (CNVs) constitute very common differences between individual humans and possibly all genomes and may therefore be important fuel for evolution, yet how they form remains elusive. In starving Escherichia coli, gene amplification is induced by stress, controlled by the general stress response. Amplification has been detected only encompassing genes that confer a growth advantage when amplified. We studied the structure of stress-induced gene amplification in starving cells in the Lac assay in Escherichia coli by array comparative genomic hybridization (aCGH), with polymerase chain reaction (pcr) and DNA sequencing to establish the structures generated. About 10% of 300 amplified isolates carried other chromosomal structural change in addition to amplification. Most of these were inversions and duplications associated with the amplification event. This complexity supports a mechanism similar to that seen in human non-recurrent copy number variants. We interpret these complex events in terms of repeated template switching during DNA replication. Importantly, we found a significant occurrence (6 out of 300) of chromosomal structural changes that were apparently not involved in the amplification event. These secondary changes were absent from 240 samples derived from starved cells not carrying amplification, suggesting that amplification happens in a differentiated subpopulation of stressed cells licensed for global chromosomal structural change and genomic instability. These data imply that chromosomal structural changes occur in bursts or showers of instability that may have the potential to drive rapid evolution.

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