In Vitro Evaluation of the Biological Responses of Canine Macrophages Challenged with PLGA Nanoparticles Containing Monophosphoryl Lipid A.

Poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) have been considerably studied as a promising biodegradable delivery system to induce effective immune responses and to improve stability, safety, and cost effectiveness of vaccines. The study aimed at evaluating early inflammatory effects and cellular safety of PLGA NPs, co-encapsulating ovalbumin (PLGA/OVA NPs), as a model antigen and the adjuvant monophosphoryl lipid A (PLGA/MPLA NPs) as an adjuvant, on primary canine macrophages. The PLGA NPs constructs were prepared following the emulsion-solvent evaporation technique and further physic-chemically characterized. Peripheral blood mononuclear cells were isolated from canine whole blood by magnetic sorting and further cultured to generate macrophages. The uptake of PLGA NP constructs by macrophages was demonstrated by flow cytometry, transmission electron microscopy and confocal microscopy. Macrophage viability and morphology were evaluated by trypan blue exclusion and light microscopy. Macrophages were immunophenotyped for the expression of MHC-I and MHC-II and gene expression of Interleukin-10 (IL-10), Interleukin-12 (IL-12p40), and tumor necrosis factor alpha (TNF-α) were measured. The results showed that incubation of PLGA NP constructs with macrophages revealed effective early uptake of the PLGA NPs without altering the viability of macrophages. PLGA/OVA/MPLA NPs strongly induced TNF-α and IL-12p40 expression by macrophages as well as increase relative expression of MHC-I but not MHC-II molecules. Taken together, these results indicated that PLGA NPs with addition of MPLA represent a good model, when used as antigen carrier, for further, in vivo, work aiming to evaluate their potential to induce strong, specific, immune responses in dogs.

Tailored polymer-metal fractal nanocomposites: an approach to highly active surface enhanced Raman scattering substrates.

An important design approach for sensitive and robust surface enhanced Raman scattering (SERS) substrates is the use of metal nanoparticle aggregates with nanometer tailored interstitial distances between their surfaces, in order to confine the electromagnetic energy. The nanostructural instability of the aggregates to agglomeration due to their strong van der Waals force poses a challenge for the preparation of large-scale, reliable SERS substrates. We present a novel route for preparing stable and highly active SERS substrates using polymer-metal fractal nanocomposites. This methodology is based on the unique morphology of fractal nanocomposite structures formed just below the percolation threshold that consists of extremely narrow (approximately 0.8 nm) interstitial polymer junctions between the Ag nanoparticle aggregates along with the appropriate nanoscale (<100 nm) surface roughness. Such nanomorphology allows the formation of well-defined and large numbers of hot spots where the localization of electromagnetic energy can result in very large enhancement of the Raman signal. We applied a simple plasma etching process to remove the polymer structures that allowed the formation of Ag structures with very uniform and controllable inter-particle gaps that were proved to provide significant SERS enhancement of typical biological systems such as double-stranded deoxyribonucleic acid (dsDNA). These advanced nanocomposite films could be used for the development of large-scale spectroscopy-based sensors for direct detection and analysis of various biological and chemical samples.

Interaction of hybrid nanowire-nanoparticle structures with carbon monoxide.

A gas-phase sensor based on a GaN nanowire mat decorated with Au nanoparticles was studied both experimentally and theoretically. The sensor is responsive to CO and H(2) and could be used to study the water-gas-shift reaction, which involves combining CO and H(2)O to produce H(2). It was shown that for catalyzing this reaction using support Au nanoparticles, the sequence in which the reactants are exposed to the catalyst surface is critical. To quantitatively evaluate the sensor response to gas exposure a depletion model was developed that considered the Au nanoparticle-semiconductor interface as a nano-Schottky barrier where variation in the depletion region caused changes in the electrical conductivity of the nanowires.

Preparation of ultrafine chalcopyrite nanoparticles via the photochemical decomposition of molecular single-source precursors.

The synthesis and characterization of ultrafine CuInS2 nanoparticles are described. Ultraviolet irradiation was used to decompose a molecular single source precursor, yielding organic soluble approximately 2 nm sized nanoparticles with a narrow size distribution. UV-vis absorption, 1H and 31P{1H} NMR, and fluorescence spectroscopies and mass spectrometry were used to characterize decomposition of the precursors and nanoparticle formation. The nanoparticles were characterized by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy energy dispersive X-ray spectroscopy, powder X-ray diffraction (XRD), electron diffraction, inductively coupled plasma analysis, UV-vis absorption spectroscopy, and fluorescence spectroscopy. They have a wurzite-type crystal structure with a copper-rich composition. The hypsochromic shift in their emission band due to quantum confinement effects is consistent with the size of the nanocrystals indicated in the HRTEM and XRD analyses.