Gene silencing by double-stranded RNA, denoted RNA interference, represents a new paradigm for rational drug design1. However, the transformative therapeutic potential of short interfering RNA (siRNA) has been stymied by a key obstacle—safe delivery to specified target cells in vivo2. Macrophages are particularly attractive targets for RNA interference therapy because they promote pathogenic inflammatory responses in diseases such as rheumatoid arthritis, atherosclerosis, inflammatory bowel disease and diabetes3. Here we report the engineering of β1,3-d-glucan-encapsulated siRNA particles (GeRPs) as efficient oral delivery vehicles that potently silence genes in mouse macrophages in vitro and in vivo. Oral gavage of mice with GeRPs containing as little as 20 µg kg−1 siRNA directed against tumour necrosis factor α (Tnf-α)depleted its messenger RNA in macrophages recovered from the peritoneum, spleen, liver and lung, and lowered serum Tnf-α levels. Screening with GeRPs for inflammation genes revealed that the mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) is a previously unknown mediator of cytokine expression. Importantly, silencing Map4k4 in macrophages in vivo protected mice from lipopolysaccharide-induced lethality by inhibiting Tnf-α and interleukin-1β production. This technology defines a new strategy for oral delivery of siRNA to attenuate inflammatory responses in human disease.

Nonviral gene delivery technologies have been developed using layer-by-layer self-assembly of nanomaterials held together by electrostatic interactions in order to provide nanoparticulate materials that protect and deliver DNA to cells. Here we report a new DNA delivery technology based on the in situ layer-by-layer synthesis of DNA nanoparticles caged within hollow yeast cell wall particles (YCWP). YCWP provide protection and facilitate oral and systemic receptor-targeted delivery of DNA payloads to phagocytic cells. The nanoparticles inside YCWP consist of a core of tRNA/polyethylenimine (PEI) followed by a DNA layer that is finally coated with a protective outer layer of PEI. Using fluorescein and rhodamine labeling of tRNA, PEI, and DNA, the layer-by-layer formation of the nanoparticles was visualized by fluorescent microscopy and quantitated by fluorescence spectroscopy and flow cytometry. Optimal conditions (tRNA:YCWP, PEI:YCWP ratios and DNA load levels) to synthesize YCWP encapsulated nanoparticles were determined from these results. The high in vitro transfection efficiency of this encapsulated DNA delivery technology was demonstrated by the transfection of NIH3T3-D1 cells with YCWP-tRNA/PEI/gWizGFP/PEI formulations containing low amounts of the plasmid gWizGFP per particle to maximally express green fluorescent protein (GFP).

Phagocytic macrophages and dendritic cells are desirable targets for potential RNAi (RNA interference) therapeutics because they often mediate pathogenic inflammation and autoimmune responses. We recently engineered a complex 5 component glucan-based encapsulation system for siRNA (small interfering RNA) delivery to phagocytes. In experiments designed to simplify this original formulation, we discovered that the amphipathic peptide Endo-Porter forms stable nanocomplexes with siRNA that can mediate potent gene silencing in multiple cell types. In order to restrict such gene silencing to phagocytes, a method was developed to entrap siRNA-Endo-Porter complexes in glucan shells of 2-4 μm diameter in the absence of other components. The resulting glucan particles containing fluorescently labelled siRNA were readily internalized by macrophages, but not other cell types, and released the labelled siRNA into the macrophage cytoplasm. Intraperitoneal administration of such glucan particles containing siRNA-Endo-Porter complexes to mice caused gene silencing specifically in macrophages that internalized the particles. These results from the present study indicate that specific targeting to phagocytes is mediated by the glucan, whereas Endo-Porter peptide serves both to anchor siRNA within glucan particles and to catalyse escape of siRNA from phagosomes. Thus we have developed a simplified siRNA delivery system that effectively and specifically targets phagocytes in culture or in intact mice.

Glucan particles (GPs) are hollow, porous 2–4 μm microspheres derived from the cell walls of Baker's yeast (Saccharomyces cerevisiae). The 1,3-β-glucan outer shell provides for receptor-mediated uptake by phagocytic cells expressing β-glucan receptors. GPs have been used for macrophage-targeted delivery of soluble payloads (DNA, siRNA, protein, and small molecules) encapsulated inside the hollow GPs via core polyplex and layer-by-layer (LbL) synthetic strategies. In this communication, we report the incorporation of nanoparticles as cores inside GPs (GP-NP) or electrostatically bound to the surface of chemically derivatized GPs (NP-GP). GP nanoparticle formulations benefit from the drug encapsulation properties of NPs and the macrophage-targeting properties of GPs. GP nanoparticle formulations were synthesized using fluorescent anionic polystyrene nanoparticles allowing visualization and quantitation of NP binding and encapsulation. Mesoporous silica nanoparticles (MSNs) containing the chemotherapeutic doxorubicin (Dox) were bound to cationic GPs. Dox-MSN-GPs efficiently delivered Dox into GP phagocytic cells resulting in enhanced Dox-mediated growth arrest.

Staphylococcus epidermidis is among the most commonly isolated microbes from medical implant infections, particularly in the colonization of blood-contacting devices. We explored the relationships between surface wettability and root-mean-square roughness (Rq) on microbial adhesive strength to a substrate. Molecular-level interactions between S. epidermidis and a variety of chemically and texturally distinct model substrata were characterized using a cellular probe and atomic force microscopy (AFM). Substrata included gold, aliphatic and aromatic self-assembled monolayers, and polymeric and proteinaceous materials. Substrate hydrophobicity, described in terms of the water contact angle, was an insufficient parameter to explain the adhesive force of the bacterium for any of the surfaces. Correlations between adhesion forces and Rq showed weak relationships for most surfaces. We used an alternate methodology to characterize the texture of the surface that is based on a fractal tiling algorithm applied to images of each surface. The relative area as a function of the scale of observation was calculated. The discrete bonding model (DBM) was applied, which describes the area available for bonding interactions over the full range of observational scales contained in the measured substrate texture. Weak negative correlations were obtained between the adhesion forces and the area available for interaction, suggesting that increased roughness decreases bacterial adhesion when nano- to micrometer scales are considered. We suggest that modification of the DBM is needed in order to include discontinuous bonding. The adhesive strength is still related to the area available for bonding on a particular scale, but on some very fine scales, the bacteria may not be able to conform to the valleys or pits of the substrate. Therefore, the bonding between the bacterium and substrate becomes discontinuous, occurring only on the tops of ridges or asperities.

Glucan particles (GPs) are 2-4 m spherical, hollow, porous shells extracted from Baker's yeast, Saccharomyces cerevisae. The surface of the GPs is composed primarily of 1,3--glucan and the particles are efficiently phagocytosed via receptor-mediated cell uptake by macrophages, phagocytic cells expressing glucan receptors. The hollow cavity of the GPs allows for efficient absorption and encapsulation of payload molecules. Rifampicin (Rif), a drug used in tuberculosis treatment, was encapsulated by precipitation in GPs and trapped using a calcium alginate or chitosan hydrogel to seal the pores of GPs and slow Rif release. Unplugged GP formulations immediately released Rif following particle resuspension in aqueous buffer. Alginate and chitosan sealing of GPs loaded with Rif was able to extend drug release for 24-72 h. GP-Rif formulations containing 10% w/w Rif/GP plugged with a calcium alginate hydrogel were effective at reducing colony forming units of M. tuberculosis strain mc 2 6020 in infected bone marrow macrophages ~80-90% at 24 and 72 hours. The amount of Rif delivered in the GP formulations was below the free Rif minimal inhibitory concentration demonstrating that GP targeted Rif delivery to macrophages enhances Rif antimicrobial effects. OPEN ACCESSPolymers 2010, 2 682

Glucan particles (GPs) are spherical hollow particles derived from Saccharomyces cerevisiae cell walls and mainly consist of β-1, 3-D-glucans. The inner hollow cavity of glucan particles can be loaded with different compounds, including protein antigens, and delivered to macrophages and dendritic cells. Moreover, the GP delivery system possesses β-glucan's intrinsic immunostimulatory properties. Therefore, GPs serve as both an antigen-presenting cell-targeted delivery system and an adjuvant.Here, we describe the production of GPs from S. cerevisiae using hot alkaline and solvent extraction and characterization of these particles for morphology, particle density, and hydrodynamic volume. A detailed protocol for loading and entrapping a model antigen, ovalbumin (OVA), into these particles using yeast RNA is presented. Similar methods are used to load pathogen-specific antigens (peptides, proteins, soluble extracts) which then can be tested in in vivo vaccination models.

Three photocurrent-generating thin films were assembled on gold surfaces. SAM I was constructed from molecules consisting of an alkyl disulfide group linked covalently to a 12-residue helical peptide and terminated with an alanine residue containing a pyrene chromophore. SAM I served as a benchmark for multilayered films II and III in photocurrent generation experiments. Films II and III were assembled from several components that were linked noncovalently by metal-ligand complexation. Cyclic voltammetry and contact angle measurements suggest that the films consist of ordered layers with relatively few defects. Photoexcitation of SAM I by the output of a 350 nm lamp ( approximately 0.2 mW power incident on the sample) results in current generation in the range 5-10 nA/cm2. Photoexcitation of II and III yields higher current in the range 10-30 nA/cm2, representing a quantum efficiency of approximately 1%. The observation of comparable or higher current from noncovalently assembled multicomponent films indicates that this method of assembly may obviate the problems associated with the covalent assembly of devices from large molecules.