A one step synthesis and functionalization of robust, hydrophilic monolayer protected clusters of gold (Au-MPCs) containing a nitrilotriacetic acid (NTA) is described. The 14 nm Au-MPCs were prepared by the attachment of two bifunctional thioalkylated-poly(ethylene glycol) ligands on the nanoparticles, one containing a nitrilotriacetic acid (NTA) terminal group, while the second hydroxyl (OH) terminated ligand was used as a co-stabilizer to promote the stability of the MPCs. The resulting PEGylated NTA functionalized Au MPCs, which are characterized by TEM, UV-vis and agarose gel electrophoresis are attractive probes for many target species e.g. hexahistidine-tagged proteins. Importantly, the NTA functionality on MPCs ligand shell can be varied.

Quantum dots (QDs) are now used extensively for labeling in biomedical research due to their unique photoluminescence behavior, involving size-tunable emission color, a narrow and symmetric emission profile and a broad excitation range [1]. Uncoated QDs made of CdTe core are toxic to cells because of release of Cd2+ ions into the cellular environment. This problem can be partially solved by encapsulating QDs with polymers, like poly(N-isopropylacrylamide) (PNIPAM) or poly(ethylene glycol) (PEG). Based on biological compatibility, fast response as well as pH, temperature and magnetic field dependent swelling properties, hydrogel nanospheres has become carriers of drugs, fluorescence labels, magnetic particles for hyperthermia applications and particles that have strong optical absorption profiles for optical excitation. The toxicity of uncoated QDs are known; however, there have been a very limited number of studies specially designed to assess thoroughly the toxicity of nanosphere encapsulated QDs against QD density and dosing level.

In this work, we present preliminary studies of biological effects of a novel QD based nanomaterial system on Escherichia coli (E. coli) bacteria. Cadmium chalcogenide QDs provide the most attractive fluorescence labels in comparison with routine dyes or metal complexes. Nanospheres on the other hand are the most commonly used carriers of fluorescence labels for fluorescence detection. The integration of fluorescent QDs in nanospheres therefore provides a new generation of fluorescence markers for biological assays. Hydrogels based on PNIPAM is a well known thermoresponsive polymer that undergoes a volume phase transition across the low critical solution (LCST) [2]. Therefore, the inherent temperature-sensitive swelling properties of PNIPAM offer the potentiality to control QD density within the nanospheres. In the present work, E. coli growth was monitored as E. coli served as a representation of how cells might respond in the presence of hydrogel encapsulated QDs in their growth environment. The present work describes the successful encapsulation of CdTe QDs in PNIPAM gel network. Microgel encapsulated QDs were synthesized by first preparing PNIPAM microspheres with cystaminebisacrylamide as a crosslinker and CdTe QDs capped with a stabilizer. The CdTe QDs were bonded into PNIPAM microgels through the replacement of CdTe's stabilizer inside PNIPAM microspheres. Growth curves were generated for E. coli growing in 20 mL of LB media containing hydrogel encapsulated QD nanospheres (400 nm diameter) at relatively higher (0.5mg/mL) and lower (0.01mg/mL) concentration of solution. From the growth curves, there was no evidence at lower concentration (0.01mg/mL) that the hydrogel encapsulated QDs prevent the microbial cells from growing but at higher concentration (0.5mg/mL), microbial growth was inhibited. Transmission Electron Microscopy (TEM) was used to characterize QD size and density inside the hydrogel nanospheres. Scanning Electron Microscopy (SEM) was used to observe size and morphology of the hydrogel particles. Further investigation is going on cell growth response at different QD density and to evaluate the limiting hydrogel concentration for different QD densities.

Due to their small size, high diffusivity, and chemically active surfaces, nanoparticles share much in common with water-soluble proteins. These similarities have generated great interest in using biofunctional nanoparticles as a route to deliver targeted therapeutics. Already nanoparticles have found applications in the hyperthermia of tumors, personal care lotions, and tissue scaffolding. Our study focuses on the targeting of such nanoparticles to specific biological sites. It therefore seeks to identify the factors that control the migration and capture of nanoparticles within living systems. In particular, we examine the affinity of anti-collagen coated magnetite nanoparticles for collagen IV-coated surfaces under flow stress. The studies are performed within microfluidic devices that are designed to mimic various fluid flow patterns within the body. We find, in this case, a large background signal due to nonspecific binding. Further examination shows a correlation between chemical functionality (e.g., surface charge, hydrophilicity) that suggests that a balanced approach between biological functionality and chemical functionality may reduce the background from nonspecific binding to acceptable levels.

Yb3+ doped Y3Al5O12 (YAG:Yb3+) nanoparticles are prepared from yttrium acetate tetrahydrate, ytterbium acetate tetrahydrate and aluminum isopropoxide in 1,4-butanediol by autoclave treatment at 300 °C for 2 h. Moreover, Gd-YAG:Yb3+ nanoparticles are prepared from the mixture of YAG:Yb3+ colloidal solution and gadolinium acetate tetrahydrate by the same autoclave treatment as YAG:Yb3+. Properties of structure, near infrared photoluminescence and magnetic resonance contrast enhancement are characterized for as-prepared and calcined YAG:Yb3+ and Gd-YAG:Yb3+ nanoparticles.

Rare-earth doped oxides as bulk materials are well known for their numerous applications in light emitting devices. Emission properties of nanoparticles, in association with their small size, open the way to new applications such as the elaboration of transparent luminescent devices or new biological labels. The key issue for such applications is the control of the surface state of the particles in order to preserve their dispersion state, to guarantee a strong emission and/or ensure strong interactions with specific target sites. Our work in this field mainly concerns yttrium vanadate particles (YVO4:Ln with Ln=Eu, Dy and Yb/Er) that are obtained as aqueous suspensions through a simple reaction of coprecipitation [1]. As compared to the bulk material, these particles (10-40 nm in diameter) exhibit the characteristic emission from the lanthanide dopant but with a lower efficiency (quantum yield of 15% and emission lifetime of 0.7 ms). The first part of our work is devoted to the improvement of the emission properties of particles. Our results show that the emission process is altered either by surface hydroxyl groups or by the poor cristallinity of the particles. We show that large improvement can be obtained following an original process which allows recovering the particles as colloidal dispersions after their thermal treatment at 1000°C. In the case of Eu3+ doped particles, quantum yield and emission lifetime were increased up to 40% and 0.8 ms respectively without notable increase of particle size. Moreover, the emission spectrum, either from colloidal suspensions or from single particles fits almost perfectly to the one from the bulk material. The second part of our work is devoted to the surface derivatization of the particles for applications as biological probes [2]. We chose a general scheme involving the coating of the nanoparticles with a thin layer of amino-silane. This process was chosen in order to allow further versatile grafting reactions trough the surface amino groups. This strategy will be detailed in the case of the coupling between our particles and a protein through the use of a homo-bifunctional cross-linker. The quantification of the number of attached proteins was achieved using dual-color microscopy and fluorescently-tagged proteins, by observing the step-like photobleaching of the organic fluorescent tag. The observation of labelled toxins interacting with living cells shows the high potentiality of rare-earth-doped oxide particles as new biological probes.

We synthesized dendrimer composite nanoparticles and investigated their potential for traditional X-ray imaging and Computed Tomography (CT). These new X-ray contrast agents show better contrast compared to traditional iodine-based contrast agents, and are expected to clear from the blood much slower than commercial agents, permitting longer imaging times. We have also investigated their safety profile in terms of viscosity and osmotic pressure.

Composite nanoparticles consisting of gold and iron-oxide were radiochemically synthesized in aqueous solution systems by using polyethylene glycols. The gold particles with average diameter of 3 nm were firmly immobilized on the surface of the support iron-oxide nanoparticles. The composite nanoparticles specifically adsorbed sulfur-containing amino acids by a Au-S bonding.

We demonstrate the design of novel sensor particles that display fluorescence in the presence of elastase, an enzyme that is present at elevated levels in chronic (non-healing) wounds. Poly(ethyleneglycol acrylamide) hydrogel particles, approximately 200μm in diameter are used as a polymeric matrix, to which a peptide based sensing element is attached. This sensing element consists of a Förster resonance energy transfer (FRET) pair separated by an enzyme cleavable linker. In addition, negatively charged Glutamic acid (Glu) residues are incorporated into the hydrogel structure to facilitate diffusion of the positively charged enzyme into the hydrogel matrix. Enzymatic hydrolysis of the enzyme cleavable linker results in fluorescence of the donor molecule being switched on. We have shown that these particles can detect elastase to a concentration of 100ng/ml, a concentration found in chronic wound fluids. These particles simultaneously detect and address balances in elastase levels and may therefore find applications as smart wound dressings.

Carbon nanostructures, e.g., nanotubes, fullerenes, carbon blacks, etc., are being extensively explored for numerous biomedical applications. The most of such studies, however, deal with carbon nanotubes, and comparatively less is known on the biomedical potential of other nanosize carbon particles. In the present work, carbon and metal/carbon core/shell spherical nanoparticles have been prepared using the decomposition of monosaccharide-based compositions under hydrothermal conditions with or without the presence of metal seed particles. The effects of different process conditions on the particle size, structure, and composition have been examined using TEM, XRD, UV-Vis, FTIR and Raman spectroscopies. The nearly perfect spherical particles with the dimensions in the range of 20 – 100 nm have been obtained depending on the process parameters such as precursor concentration, presence of seed particles and polymeric additives, process temperature and time. The particles prepared with 5 – 20 nm gold seeds clearly showed the core/shell structure with the thickness of carbon shell in the range of 10 – 50 nm. The FTIR experiments have indicated a strong effect of the processing conditions on the chemical activity of nanoparticle surfaces in the attachment of the additional surface functional groups and organic molecules. It has been found that the both hydrothermally prepared carbon and metal/carbon core/shell nanoparticles possess very good dispersibility and stability in the both water and simulated body fluids in the most of experiments. The particles have been successfully functionalized with several molecules such as polyethyleneglucol and biotin. Selected samples of well-dispersed carbon nanospheres with different concentrations have been tested for their interaction with several cultured cell lines including epidermal keratinocytes, fibroblasts, and dog macrophages.

Signal transduction for purposes of biomolecular sensing can be enhanced through miniaturization (nanoscale sensors such as nanowires, cantilevers, etc), but this may impose insurmountable limitations on transport of analyte molecules to the surface. In order to improve biomolecular detection sensitivity, this study aims to develop electrodeless dielectrophoresis (EDEP) methods for the selective transport and trapping of analytes in close proximity to the sensor surface. A device design based on microscale dielectric constrictions of the fluidic channel and nanoscale metal electrode edges was used to locally enhance electric field gradients and trap biomolecules. The resulting electric field focusing effect was enhanced as a result of miniaturization and an instantaneous ten-fold EDEP preconcentration was obtained in high-salt buffers (50 mM NaCl) that enabled an equivalent improvement in DNA hybridization kinetics.

CuInS2 (CIS) fluorescent nanocrystals (NCs) were obtained by heating organic metal complex. The photoluminescence (PL) originated from the donor-acceptor, and the quantum yield (QY) was achieved at 6%. Furthermore, we doped some metal ions (Zn2+, Cd2+ or Ag+) by the post heat-treatment in the organic coordinating solvent in order to tune the band gap of NCs. By this post treatment, the alteration of NCs structure was suggested, such as changing into an alloying and composite structure. In Zn-doping, the PL wavelength was widely tuned from 535 to 650 nm by alloying between CIS and ZnS. Moreover, PL intensity was increased with these structure alterations. In particular, the materials doped with Zn or Cd achieved respective QY of 25% and 40%.