102 research outputs found

    Maltoheptaose Promotes Nanoparticle Internalization by Escherichia coli

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    Nanoparticles conjugated with D-maltoheptaose (G7) showed a striking increase in the surface adherence and internalization by E. coli. This applies to silica nanoparticles (SNP), magnetic nanoparticles (MNP), silica-coated magnetic nanoparticles (SMNP) and silica-coated quantum dots (SQDs) ranging from a few to over a hundred nanometers in size, as well as wild type E. coli ATCC 33456, ORN 178, ORN 208 with the maltodextrin transport channel and the LamB mutant JW 3392-1 (Fig. 1). TEM images including the thin section samples revealed the uptake of nanoparticles in cell walls and inside the cytoplasm (Fig. 2). Unfunctionalized nanoparticles and nanoparticles functionalized with β-cyclodextrin (CD) showed little or no binding to the E. coli cell surface, and no obvious internalization of the nanoparticles was observed. D-Mannose-functionalized nanoparticles bound to the pili of E. coli ORN 178 through the well-known Man-binding lectin (FimH) rather than cell internalization. Surface ligands that can improve the uptake of nanomaterials to bacterial cells should provide a powerful means of targeting a payload delivery to a potential disease causing strain. Work is underway to develop nanomaterial delivery systems for multidrug resistance bacteria

    Interactions of Carbohydrate-conjugated Nanoparticles with Mycobacterium Smegmatis

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    Mycobacterium smegmatis is a non-pathogenic microorganism and has been widely used as a model organism to study infections caused by M. tuberculosis and other mycobacterial pathogens. We report that nanoparticles conjugated with selected carbohydrate show a striking increase in the surface adherence by M. smegmatis. This applies to silica nanoparticles and magnetic nanoparticles ranging from 100 nm to 5 nm. Under the same experimental conditions, minimum adhesion was observed for unfunctionalized nanoparticles. The synthesis and characterization of the glyconanoparticles will be presented. The finding is applied to imaging M. smegmatis infected lung epithelial cells, and the results will be discussed

    Glyconanoparticle Uptake Profile in Lung Carcinoma Cells

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    Non-small cell lung carcinoma (NSCLC) is responsible for nearly 85% of lung cancer, and early diagnosis and treatment of lung cancer can circumvent possible death. We focus on glyconanoparticles with a magnetic or a fluorescent core that act as multivalent glyco-scaffold to study cell surface interaction and internalization. The glyconanoparticles were synthesized by conjugating various carbohydrates on magnetic nanoparticles and fluorescent silica nanoparticles by a photocoupling technique developed in our laboratory. The size of nanoparticles used varies from 6 nm to 60 nm. The resulting glyconanoparticles were treated with human adenocarcinoma non-small lung epithelial cells (A549) and the primary small airway epithelial cells (PCS-301-010). The cellular uptake was studied and quantified by confocal fluorescence microscopy, flow cytometry, thin section TEM, and prussian blue staining. We found that the extent of cellular uptake was dependent on the type of carbohydrate ligands and the nature of the nanoparticles used. Experiments were conducted to investigate the mechanism of the uptake, and results will be discussed

    Enhancing Antibiotic Activity Using Nanomaterial-Antibiotic Conjugates

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    We demonstrate that streptomycin conjugated on silica nanoparticles (SNP-Str) can be used to effectively target streptomycin-resistant Escherichia coli (E. coli) bacteria by lowering the minimum inhibitory concentration (MIC) of streptomycin up to 2 log folds. Silica nanoparticles were synthesized with an average diameter of 80, 50 and 30 nm, respectively. Streptomycin was then covalently conjugated to SNP using efficient photocoupling chemistry. The MIC for free streptomycin sulfate was recorded as a high 2.0 mg/mL for an engineered Strr mutant E. coli ORN 208. Conjugating the streptomycin to SNP resulted in the decrease in MIC to 161 μg/mL, 63 μg/mL, and 19 μg/mL for SNP of 80, 50 and 30 nm, respectively. In this poster, the synthesis, characterization, and evaluation of SNP-Str will be presented and discussed

    Analysis of the Surface Density and Reactivity of Perfluorophenylazide and the Impact on Ligand Immobilization

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    Perfluorophenylazide (PFPA) chemistry is a novel method for tailoring the surface properties of solid surfaces and nanoparticles. It is general and versatile, and has proven to be an efficient way to immobilize graphene, proteins, carbohydrates, and synthetic polymers. The main thrust of this work is to provide a detailed investigation on the chemical composition and surface density of the PFPA tailored surface. Specifically, gold surfaces were treated with PFPA-derivatized (11-mercaptoundecyl) tetra(ethylene glycol) (PFPA-MUTEG) mixed with 2-[2-(2-mercaptoethoxy)ethoxy]ethanol (MDEG) at varying solution mole ratios. Complementary analytical techniques were employed to characterize the resulting films including Fourier transform infrared spectroscopy to detect fingerprints of the PFPA group, x-ray photoelectron spectroscopy and ellipsometry to study the homogeneity and uniformity of the films, and near edge x-ray absorption fine structures to study the electronic and chemical structure of the PFPA groups. Results from these studies show that the films prepared from 90:10 and 80:20 PFPA-MUTEG/MDEG mixed solutions exhibited the highest surface density of PFPA and the most homogeneous coverage on the surface. A functional assay using surface plasmon resonance with carbohydrates covalently immobilized onto the PFPAmodified surfaces showed the highest binding affinity for lectin on the PFPA-MUTEG/MDEG film prepared from a 90:10 solution

    Dynamic Modeling and Vibration Analysis for the Vehicles with Rigid Wheels Based on Wheel-Terrain Interaction Mechanics

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    The contact mechanics for a rigid wheel and deformable terrain are complicated owing to the rigid flexible coupling characteristics. Bekker's equations are used as the basis to establish the equations of the sinking rolling wheel, to vertical load pressure relationship. Since vehicle movement on the Moon is a complex and on-going problem, the researcher is poised to simplify this problem of vertical loading of the wheel. In this paper, the quarter kinetic models of a manned lunar rover, which are both based on the rigid road and deformable lunar terrain, are used as the simulation models. With these kinetic models, the vibration simulations were conducted. The simulation results indicate that the quarter kinetic model based on the deformable lunar terrain accurately reflects the deformable terrain's influence on the vibration characteristics of a manned lunar rover. Additionally, with the quarter kinetic model of the deformable terrain, the vibration simulations of a manned lunar rover were conducted, which include a parametric analysis of the wheel parameters, vehicle speed, and suspension parameters. The results show that a manned lunar rover requires a lower damping value and stiffness to achieve better vibration performance

    The sialic acid-dependent nematocyst discharge process in relation to its physical-chemical properties is a role model for nanomedical diagnostic and therapeutic tools

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    Formulas derived from theoretical physics provide important insights about the nematocyst discharge process of Cnidaria (Hydra, jellyfishes, box-jellyfishes and sea-anemones). Our model description of the fastest process in living nature raises and answers questions related to the material properties of the cell- and tubule-walls of nematocysts including their polysialic acid (polySia) dependent target function. Since a number of tumor-cells, especially brain-tumor cells such as neuroblastoma tissues carry the polysaccharide chain polySia in similar concentration as fish eggs or fish skin, it makes sense to use these findings for new diagnostic and therapeutic approaches in the field of nanomedicine. Therefore, the nematocyst discharge process can be considered as a bionic blue-print for future nanomedical devices in cancer diagnostics and therapies. This approach is promising because the physical background of this process can be described in a sufficient way with formulas presented here. Additionally, we discuss biophysical and biochemical experiments which will allow us to define proper boundary conditions in order to support our theoretical model approach. PolySia glycans occur in a similar density on malignant tumor cells than on the cell surfaces of Cnidarian predators and preys. The knowledge of the polySia-dependent initiation of the nematocyst discharge process in an intact nematocyte is an essential prerequisite regarding the further development of target-directed nanomedical devices for diagnostic and therapeutic purposes. The theoretical description as well as the computationally and experimentally derived results about the biophysical and biochemical parameters can contribute to a proper design of anti-tumor drug ejecting vessels which use a stylet-tubule system. Especially, the role of nematogalectins is of interest because these bridging proteins contribute as well as special collagen fibers to the elastic band properties. The basic concepts of the nematocyst discharge process inside the tubule cell walls of nematocysts were studied in jellyfishes and in Hydra which are ideal model organisms. Hydra has already been chosen by Alan Turing in order to figure out how the chemical basis of morphogenesis can be described in a fundamental way. This encouraged us to discuss the action of nematocysts in relation to morphological aspects and material requirements. Using these insights, it is now possible to discuss natural and artificial nematocyst-like vessels with optimized properties for a diagnostic and therapeutic use, e.g., in neurooncology. We show here that crucial physical parameters such as pressure thresholds and elasticity properties during the nematocyst discharge process can be described in a consistent and satisfactory way with an impact on the construction of new nanomedical devices

    Glyconanomaterials for biosensing applications

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    A Photochemically Initiated Chemistry for Coupling Underivatized Carbohydrates to Gold Nanoparticles

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    The sensitive optoelectronic properties of metal nanoparticles make nanoparticle-based materials a powerful tool to study fundamental biorecognition processes. Here we present a new and versatile method for coupling underivatized carbohydrates to gold nanoparticles (Au NPs) via the photochemically induced reaction of perfluorophenylazide (PFPA). A one-pot procedure was developed where Au NPs were synthesized and functionalized with PFPA by a ligand-exchange reaction. Carbohydrates were subsequently immobilized on the NPs by a fast light activation. The coupling reaction was efficient, resulting in high coupling yield as well as high ligand surface coverage. A colorimetric system based on the carbohydrate-modified Au NPs was used for the sensitive detection of carbohydrate-protein interactions. Binding and cross-reactivity studies were carried out between carbohydrate-functionalized Au NPs and lectins. Results showed that the surfacebound carbohydrates not only retained their binding affinities towards the corresponding lectin, but also exhibited affinity ranking consistent with that of the free ligands in solution
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