Polymer functionalization and solubilization of carbon nanosheets.

Few-layer graphene materials or "carbon nanosheets" were covalently functionalized with poly(vinyl alcohol) via ester linkages, and the resulting functionalized sample became soluble, allowing solution-phase processing for various purposes such as the fabrication of polymer-carbon nanosheets composites containing no dispersion agents or any other foreign substances.

Acute and long-term effects after single loading of functionalized multi-walled carbon nanotubes into zebrafish (Danio rerio).

Carbon nanotubes (CNTs) are widely explored for biomedical applications, but there is very limited information regarding their in vivo biodistribution and biocompatibility. Here, we report the in vivo biodistribution and long-term effects of functionalized multi-walled carbon nanotubes (MWCNTs) in developing zebrafish. The fluorescent-labeled MWCNTs were introduced into zebrafish embryos at 1-cell stage and at 72 h post fertilization through microinjection. After single injection, both acute and long-term interactions between zebrafish and functionalized MWCNTs were studied. The injected FITC-BSA-MWCNTs (at 1-cell stage) were allocated to all blastoderm cells of the embryos through proliferation, and were distinctively excluded from the yolk cell. When introduced into the circulation system, FITC-BSA-MWCNTs moved easily in the compartments and finally were cleaned out by the body at 96 h after the loading. At early stages, the treated zebrafish embryos generated immune response by accumulating circulating white blood cells at the trunk region. Under transmission electron microscope, many lysosome-like vesicles were observed in the blastoderm cells of the treated embryos. The zebrafish loaded with MWCNTs had normal primordial germ cells at early stage and produced second generation later on. However, the larvae of the second generation had obviously lower survival rates as compared to the untreated groups, suggesting a negative effect on the reproduction potential. These results suggest that extensive purification and functionalization processes can help improve the biocompatibility of CNTs. This study also indicates that purified CNTs may have long-term toxicity effects when they were delivered into the body.

Enhancing antimicrobial activity of lysozyme against Listeria monocytogenes using immunonanoparticles.

The antimicrobial efficacy of lysozyme may be reduced by undesirable interactions with food components and nontarget bacteria. Immunonanoparticles, i.e., nanoparticles functionalized with pathogen-specific antibodies, may serve as an antimicrobial carrier for improving the stability and activity of antimicrobials in foods. The objective of this research was to study the antimicrobial activity of lysozyme-carrying immunonanoparticles against Listeria monocytogenes. Polystyrene nanoparticles with active carboxyl groups were conjugated with anti-L. monocytogenes antibody through covalent bonding. Enhanced antimicrobial activity of lysozyme-carrying immunonanoparticles was achieved when 0.04 microg/ml anti-L. monocytogenes antibody was used for coating nanoparticles and the resulting immunonanoparticles were then coated with lysozyme for 6 h. Lysozyme-carrying immunonanoparticles with a final concentration of 35 microg/ml reduced L. monocytogenes Scott A populations from ca. 5 log CFU/ml to below the detection limit (< 1 log CFU/ml) within 3 h. However, when 500 microg/ml lysozyme was used, ca. 2 log CFU/ml concentration of L. monocytogenes cells remained culturable after 5 h of treatment. The addition of lysozyme-carrying immunonanoparticles (37 microg/ml) to an L. monocytogenes solution of ca. 7 log CFU/ml for 6 h resulted in 0.9-, 1.0-, and 2.3-log greater reductions of L. monocytogenes cells than that achieved with lysozyme-carrying nanoparticles and lysozyme solutions of 500 and 50 microg/ml, respectively. Overall, lysozyme-carrying immunonanoparticles had significantly more anti-L. monocytogenes activity (P < 0.05) than did lysozyme-carrying nanoparticles and lysozyme solutions at higher concentrations (500 and 50 microg/ml). Our study revealed that the use of lysozyme-carrying immunonanoparticles is more effective than direct addition of lysozyme for inactivating L. monocytogenes in nutrient broth.

Rapid detection of Listeria monocytogenes by nanoparticle-based immunomagnetic separation and real-time PCR.

The objective of this study was to develop a method combining nanoparticle-based immunomagnetic separation (IMS) with real-time PCR for a rapid and quantitative detection of Listeria monocytogenes. Carboxyl modified magnetic nanoparticles were covalently bound with rabbit anti-L. monocytogenes via the amine groups. Several factors, such as the amount of immunomagnetic nanoparticles (IMNPs), reaction and collection times, and washing step, were optimized, and the nanoparticle-based IMS in combination with real-time PCR was further evaluated for detecting L. monocytogenes from artificially contaminated milk. The cell numbers calculated from the means of threshold cycles (CT) of PCR amplification curves were compared to those from plate counts in order to determine the correspondence degree of quantitative data. The capture efficiency (CE) by plating from IMNP-based IMS was 1.4 to 26 times higher than those of Dynabeads-based IMS depending on the initial cell concentrations inoculated into milk samples. When combined with real-time PCR, L. monocytogenes DNA was detected in milk samples with L. monocytogenes >or=10(2) CFU/0.5 ml. In the range of 10(3) to 10(7)L. monocytogenes CFU/0.5 ml, cell numbers calculated from CT values were 1.5 to 7 times higher than those derived from plate counts. Our results demonstrated that both the use of nanoparticles and the choice of anti-L. monocytogenes in our IMNP-based IMS in combination with real-time PCR has improved the sensitivity of L. monocytogenes detection from both nutrient broth and milk samples.

NMR detection of single-walled carbon nanotubes in solution.

The detection of nanotube carbons in solution by (13)C NMR is reported. The highly soluble sample was from the functionalization of (13)C-enriched single-walled carbon nanotubes (SWNTs) with diamine-terminated oligomeric poly(ethylene glycol) (PEG(1500N)). The ferromagnetic impurities due to the residual metal catalysts were removed from the sample via repeated magnetic separation. The nanotube carbon signals are broad but partially resolved into two overlapping peaks, which are tentatively assigned to nanotube carbons on semiconducting (upfield) and metallic (downfield) SWNTs. The solid-state NMR signals of the same sample are similarly resolved. Mechanistic and practical implications of the results are discussed.

Visualizing adhesion-induced agglutination of Escherichia coli with mannosylated nanoparticles.

Polymeric nanoparticles covalently functionalized with derivatized D-mannose molecules were synthesized and characterized. These nanoparticles have an average size of approximately 160 nm in diameter, thus bearing a large number of surface-tethered mannose moieties for multivalent interactions with adhesins on bacterial cells. Specifically, the mannosylated nanoparticles bind strongly with Escherichia coli, allowing the convenient visualization of adhesion interactions under a conventional electron microscope. Since a single nanoparticle is capable of binding more than one cell, the adhesion interactions result in significant nanoparticle-mediated cell agglutination according to electron microscopy imaging. Potential applications of the mannosylated nanoparticles in the inhibition of enteropathogenic infections are discussed.

Single-walled carbon nanotubes displaying multivalent ligands for capturing pathogens.

A single-walled carbon nanotube was exploited for its semi-flexible pseudo-one-dimensional nanostructure as a unique scaffold to display multivalent carbohydrate ligands, with a specific demonstration showing that galactosylated carbon nanotubes were effective in the capturing of pathogenic Escherichia coli in solution.

Polymeric nanoparticles from rapid expansion of supercritical fluid solution.

In this concept paper we highlight applications of supercritical fluid technology in particle formation and production, especially some recent advances in the rapid expansion of supercritical solutions (RESS) processing technique. We also highlight the simple but significant modification to the traditional RESS by using a liquid solvent or solution at the receiving end of the supercritical solution expansion, or the rapid expansion of a supercritical solution into a liquid solvent (RESOLV), and applications of the technique to the preparation of nanoparticles. In particular, successes and challenges in the use of RESOLV for nanoscale (<100 nm) polymeric particles and the subsequent protection of the suspended nanoparticles from agglomeration are discussed.