Macrophage inflammatory response to self-assembling rosette nanotubes

Delivery of siRNA using cationic rosette nanotubes for gene silencing

The quest for new therapeutic treatments for hereditary diseases has led to many advances in RNA interference (RNAi) and gene silencing. While this technique has the potential to address many problems, the key to its continued use is the development of effective delivery strategies that would reduce cellular toxicity and increase silencing efficiency. Rosette nanotubes (RNTs) are biomimetic supramolecular nanostructures formed through the self-assembly of hybrid guanine-cytosine (G∧C) DNA bases. Here, we used bioactive RNTs for siRNA delivery and gene silencing. Fifteen lysine-functionalized twin-G∧C motifs (KnT, n = 1 to 15) were synthesized using solid phase peptide synthesis to produce building blocks that self-assembled to produce cationic RNTs under physiological conditions. The intracellular uptake of siRNA delivered by the oligo-L-lysine RNTs was examined and it was found that the complexation of siRNA was affected by the cationic charges from the lysine residues and the length of RNTs formed, with the higher charged KnT RNTs delivering siRNA to the cells at a faster rate. In addition, by protecting siRNA from serum degradation, KnT RNTs were shown to deliver their cargo to the cells effectively via the endocytic pathway. A reduction in the expression (∼70%) of the target stat3 protein was observed during gene expression analysis in HCT116 and A549 cell lines.

Enhanced antibiotic activity of ampicillin conjugated to gold nanoparticles on PEGylated rosette nanotubes

PURPOSE

This work presents the preparation of a nanocomposite of ampicillin-conjugated gold nanoparticles (AuNPs) and self-assembled rosette nanotubes (RNTs), and evaluates its antibacterial properties against two strains of drug-resistant bacteria (Staphylococcus aureus [S. aureus], methicillin-resistant S. aureus [MRSA]).

MATERIALS AND METHODS

Small, nearly monodisperse AuNPs (1.43±0.5 nm in diameter) nucleated on the surface of polyethylene glycol-functionalized RNTs in a one-pot reaction. Upon conjugation with ampicillin, their diameter increased to 1.86±0.32 nm. The antibacterial activity of the nanocomposite against S. aureus and MRSA was tested using different concentrations of ampicillin. The cytocompatibility of the nanocomposite was also tested against human dermal fibroblasts.

RESULTS

Based on bacterial inhibition studies, the nanocomposite demonstrated enhanced antibiotic activity against both bacterial strains. The minimum inhibitory concentration (MIC) of the nanocomposite against S. aureus was found to be 0.58 μg/mL, which was 18% lower than ampicillin alone. The nanocomposite also exhibited a 20 hrs MIC of 4 μg/mL against MRSA, approximately 10-20 times lower than previously reported values for ampicillin alone. In addition, at concentrations of 4 μg/mL of ampicillin (70 μg/mL of AuNPs), the nanocomposite showed negligible cytotoxic effects.

CONCLUSION

Our findings offer a new approach for the treatment of drug-resistant bacteria by potentiating inhibitory effects of existing antibiotics, and delivering them using a non-toxic formulation.

Bioactive Organic Rosette Nanotubes Support Sensory Neurite Outgrowth

Regardless of the intervention for peripheral nerve repair, slow rates of axonal regeneration often result in poor clinical outcomes. Thus, using new materials such as biologically inspired, biocompatible, organic rosette nanotubes (RNTs) could provide a tailorable scaffold to modulate neurite extension and attachment for improved nerve repair. RNTs are obtained through the spontaneous self-assembly of a synthetic DNA base analogue featuring the hydrogen bond triads of both guanine and cytosine, the G∧C base. Here, we investigated the potential of RNTs functionalized with lysine and Arg-Gly-Asp-Ser-Lys (RGDSK) peptide to support neural growth. We hypothesized that (a) due to their dimensions, the RNTs would support neuron attachment, and (b) their conjugation to the integrin-binding peptide RGDSK would further enhance neurite outgrowth compared to unfunctionalized RNT. Neurite extension was examined on a variety of RNT structures, including RNT with a lysine side chain (K1), a mixture of the K1 and a free RGDS peptide, RNT alone, an RGDSK-functionalized RNT, in addition to poly-d-lysine and laminin controls. Both whole dorsal root ganglion (DRG) and single dissociated DRG neurons were seeded onto RNT-coated substrates containing various ratios of peptides. Analysis of neuron morphometrics showed that RNT blends support DRG neuron attachment and neurite extension, with RGDS presentation increasing neurite outgrowth from whole DRG by up to 47% over a 7-day period compared to K1 alone (p < 0.013). In addition, while RNTs increased the sprouting of primary neurites extending from dissociated DRG neurons, the total neurite outgrowth per neuron remained the same. These results show that functionalized biomimetic RNTs provide a support for neurite growth and extension and have the ability to modulate neuronal morphology. These results also pave the way for the design of injectable RNT-based nanomaterials that support guided neural regeneration following traumatic injury.

Molecular and supramolecular chemistry of rosette nanotubes

Synthetic strategies used to tune the properties of a class of supramolecular 1D nanostructures, the rosette nanotubes, are reviewed herein.

Rosette Nanotubes Alter IgE-Mediated Degranulation in the Rat Basophilic Leukemia (RBL)-2H3 Cell Line

In this study, the effects of rosette nanotube (RNT) exposure on immune cell viability and function were investigated in vitro using the rat basophilic leukemia (RBL)-2H3 cell line. RBL-2H3 viability was decreased in a dose- and time-dependent manner after lysine-functionalized RNT (K-RNT) exposure. In addition, K-RNTs had a significant effect on RBL-2H3 degranulation. When K-RNT exposure was concurrent with IgE sensitization, 50 and 100 mg l(-1) K-RNTs elicited a heightened degranulatory response compared with IgE alone. Exposure to 50 and 100 mg l(-1) K-RNTs also caused degranulation in RBL-2H3 cells not sensitized with IgE (0 ng ml(-1) IgE). Furthermore, in cells preexposed to K-RNTs for 2 h and subsequently washed, sensitized, and stimulated with IgE, a potentiated degranulatory response was observed. Using confocal laser scanning microscopy and a fluorescein isothiocyanate (FITC)-functionalized RNT construct (termed FITC(1)/TBL(19)-RNT), we demonstrated a strong and direct affiliation between RNTs and RBL-2H3 cell membranes. We also demonstrated cellular internalization of RNTs after 2 h of exposure. Together, these data demonstrate that RNTs may affiliate with the cellular membrane of RBL-2H3 cells and can be internalized. These interactions can affect viability and alter the ability of these cells to elicit IgE-FcεR mediated degranulation.

RGD-tagged helical rosette nanotubes aggravate acute lipopolysaccharide-induced lung inflammation

Rosette nanotubes (RNT) are a novel class of self-assembled biocompatible nanotubes that offer a built-in strategy for engineering structure and function through covalent tagging of synthetic self-assembling modules (G∧C motif). In this report, the G∧C motif was tagged with peptide Arg-Gly-Asp-Ser-Lys (RGDSK-G∧C) and amino acid Lys (K-G∧C) which, upon co-assembly, generate RNTs featuring RGDSK and K on their surface in predefined molar ratios. These hybrid RNTs, referred to as K^x/RGDSK^y-RNT, where x and y refer to the molar ratios of K-G∧C and RGDSK–G∧C, were designed to target neutrophil integrins. A mouse model was used to investigate the effects of intravenous K^x/RGDSK^y-RNT on acute lipopolysaccharide (LPS)-induced lung inflammation. Healthy male C57BL/6 mice were treated intranasally with Escherichia coli LPS 80 μg and/or intravenously with K⁹⁰/RGDSK¹⁰-RNT. Here we provide the first evidence that intravenous administration of K⁹⁰/RGDSK¹⁰-RNT aggravates the proinflammatory effect of LPS in the mouse. LPS and K⁹⁰/RGDSK¹⁰-RNT treatment groups showed significantly increased infiltration of polymorphonuclear cells in bronchoalveolar lavage fluid at all time points compared with the saline control. The combined effect of LPS and K⁹⁰/RGDSK¹⁰-RNT was more pronounced than LPS alone, as shown by a significant increase in the expression of interleukin-1β, MCP-1, MIP-1, and KC-1 in the bronchoalveolar lavage fluid and myeloperoxidase activity in the lung tissues. We conclude that K⁹⁰/RGDSK¹⁰-RNT promotes acute lung inflammation, and when used along with LPS, leads to exaggerated immune response in the lung.

Cytotoxicity of, and innate immune response to, size-controlled polypyrrole nanoparticles in mammalian cells

Monodisperse polypyrrole (PPy) nanoparticles with five different diameters (20, 40, 60, 80, and 100 nm) were fabricated via chemical oxidation polymerization in order to evaluate size-dependent cytotoxicity. The cellular uptake of PPy nanoparticles in human lung fibroblasts (IMR90) and mouse alveolar macrophages (J774A.1) was observed by transmission electron microscopy. The nanoparticles were internalized into the IMR90 via endocytosis. In the J774A.1, the nanoparticles were entered via phagocytosis and endocytosis. Endocytosed nanoparticles were transported to lysosome via endosome-network. The cytotoxicity and innate immune response of PPy-treated cells were systematically investigated by viability assay, oxidative stress, apoptosis/necrosis, and expression of costimulatory molecules. The viability, oxidative stress, and apoptosis/necrosis of PPy-treated cells revealed size- and dose-dependency. Because of phagocytosis, PPy treatment had more adverse effects on the J774A.1 than the IMR90. Innate immune response of PPy-treated macrophages was measured by the expression of costimulatory molecules on surface of the cells. The expression of costimulatory molecules involved in Th1 response (CD40 and CD80) was lightly up-regulated and the other costimulatory molecule related in Th2 response (CD86) was less expressed than a negative control. These findings may provide better nanotoxicological information of polymer nanomaterials, and support the further development of PPy nanoparticles in bioelectronic applications.

Rosette nanotubes with 1.4 nm inner diameter from a tricyclic variant of the Lehn-Mascal G--C base

A new strategy to access rosette nanotubes with increased inner diameter is presented and demonstrated through the synthesis and self-assembly studies of a tricyclic variant of the Lehn-Mascal G--C base.