With their bright, photostable fluorescence, semiconductor quantum dots show promise as alternatives to organic dyes for biological labeling. Questions about their potential cytotoxicity, however, remain unanswered. While cytotoxicity of bulk cadmium selenide (CdSe) is well documented, a number of groups have suggested that CdSe QDs are cytocompatible, at least with some immortalized cell lines. Using primary hepatocytes as a liver model, we found that CdSe-core QDs were indeed acutely toxic under certain conditions. Specifically, we found that the cytotoxicity of QDs was modulated by processing parameters during synthesis, exposure to ultraviolet light, and surface coatings. Our data further suggests that cytotoxicity correlates with the liberation of free Cd ions due to deterioration of the CdSe lattice. When appropriately coated, CdSe-core QDs can be rendered non-toxic and used to track cell migration and reorganization . Our results inform design criteria for the use of QDs in vitro and especially in vivo where deterioration over time may occur.

time. This might be a promising antimicrobial coating for a wide range of materials for biomedical or daily-life applications. ExperimentalPEI (MW 5000 g/mol) was purchased from Hyperpolymers (Freiburg, Germany). All other chemicals, if not stated otherwise, were from Fluka and used without further purification. One gram of PEI was suspended in 50 mL acetone and the mixture was cooled to 0 C . Methacryloyl chloride (0.83 mL dissolved in 35 mL acetone) was added dropwise to the stirred suspension within 20 min. After 30 min at 0 C, 150 mL of methanol and 20.4 mL of HEA were added to give a clear solution. The solvents were removed under reduced pressure, the PEI-MA/HEA stock solution was further diluted with HEA to control the PEI content, and 1 mg of the photoinitiator Irgacure 651 (Ciba) was dissolved in 1 mL of the solution. 20 lL of the this mixture was spread on a commercial glass slide previously modified with methacryloyloxy-propyltrimethoxysilane using a standard procedure [20]. The slide was then covered with another glass slide, previously coated with a polypropylene film. The liquid layer between the two slides was UV cured in the UV reactor Heraflash from Heraeus-Kulzer (Hanau, Germany) for 180 s to give a transparent film. The films were then washed with water/methanol/triethylamine (TEA) (1:1:1 v/v/v), water/methanol (1:1 v/v), and water, than immersed in a solution of 250 mg AgNO 3 in 8 mL water for 30 s, washed with water, and finally added to 50 mL of an aqueous solution of ascorbic acid (10 mg mL ±1 ). The modification of the films with PEG was performed as follows: The samples were washed with the water/methanol/TEA mixture, methanol, and acetone, then immersed into a solution of 2 g cyanuric chloride in 10 mL acetone at room temperature overnight, rinsed with acetone and chloroform, and finally left in a solution of 2 g O-2-aminoethyl-O¢-methoxy polyethylene glycol (MW 5000 g/ mol) in 10 mL chloroform for 24 h at room temperature. Prior to use the films were thoroughly rinsed with chloroform and immersed in a large amount of water for at least 24 h.UV-vis measurements were carried out with the photospectrometer Lambda 11 from Perkin Elmer. AFM images were recorded with a Nanoscope III scanning probe microscope using Si cantilevers with a fundamental resonance frequency of around 200 kHz. TEM measurements were carried out using a LEO 912 transmission electron microscope applying an acceleration voltage of 120 kV. The silver content was determined using the flame-atom absorption spectrometer Vario 6 from Analytik-Jena-AG (Jena, Germany).The bacterial susceptibility measurement was carried out according to a modified procedure described earlier [21]. S. aureus (ATCC 25123) cells were cultivated by adding 100 lL of a suspension of the bacterial cells in PBS (10 11 cells/mL) to 50 mL of a standard growth medium from Merck and incubating it under shaking at 37 C for 6 h. The bacterial suspension was then centrifuged at 2750 rpm for 10 min, the cells were washed twice with PBS, pH 7.0, re-suspended in...

Nanoparticle-based diagnostics and therapeutics hold great promise because multiple functions can be built into the particles. One such function is an ability to home to specific sites in the body. We describe here biomimetic particles that not only home to tumors, but also amplify their own homing. The system is based on a peptide that recognizes clotted plasma proteins and selectively homes to tumors, where it binds to vessel walls and tumor stroma. Iron oxide nanoparticles and liposomes coated with this tumorhoming peptide accumulate in tumor vessels, where they induce additional local clotting, thereby producing new binding sites for more particles. The system mimics platelets, which also circulate freely but accumulate at a diseased site and amplify their own accumulation at that site. The self-amplifying homing is a novel function for nanoparticles. The clotting-based amplification greatly enhances tumor imaging, and the addition of a drug carrier function to the particles is envisioned.clotting ͉ liver ͉ peptide ͉ tumor targeting ͉ iron oxide

Treatment of human diseases such as cancer generally involves the sequential use of diagnostic tools and therapeutic modalities. Multifunctional platforms combining therapeutic and diagnostic imaging functions in a single vehicle promise to change this paradigm. in particular, nanoparticle-based multifunctional platforms offer the potential to improve the pharmacokinetics of drug formulations, while providing attachment sites for diagnostic imaging and disease targeting features. We have applied these principles to the delivery of small interfering RNA (siRNA) therapeutics, where systemic delivery is hampered by rapid excretion and nontargeted tissue distribution. Using a PEGlyated quantum dot (QD) core as a scaffold, siRNA and tumor-homing peptides (F3) were conjugated to functional groups on the particle's surface. We found that the homing peptide was required for targeted internalization by tumor cells, and that siRNA cargo could be coattached without affecting the function of the peptide. Using an EGFP model system, the role of conjugation chemistry was investigated, with siRNA attached to the particle by disulfide cross-linkers showing greater silencing efficiency than when attached by a nonreducible thioether linkage. Since each particle contains a limited number of attachment sites, we further explored the tradeoff between number of F3 peptides and the number of siRNA per particle, leading to an optimized formulation. Delivery of these F3/siRNA-QDs to EGFP-transfected HeLa cells and release from their endosomal entrapment led to significant knockdown of EGFP signal. By designing the siRNA sequence against a therapeutic target (e.g., oncogene) instead of EGFP, this technology may be ultimately adapted to simultaneously treat and image metastatic cancer.

In the design of nanoparticles that can target disease tissue in vivo, parameters such as targeting ligand density, type of target receptor, and nanoparticle shape can play an important role in determining the extent of accumulation. Herein, a systematic study of these parameters for the targeting of mouse xenograft tumors is performed using superparamagnetic iron oxide as a model nanoparticle system. The type of targeting peptide (recognizing cell surface versus extracellular matrix), the surface coverage of the peptide, its attachment chemistry, and the shape of the nanomaterial [elongated (nanoworm, NW) versus spherical (nanosphere, NS)] are varied. Nanoparticle circulation times and in vivo tumor-targeting efficiencies are quantified in two xenograft models of human tumors (MDA-MB-435 human carcinoma and HT1080 human fibrosarcoma). It is found that the in vivo tumor-targeting ability of the NW is superior to that of the NS, that the smaller, neutral CREKA targeting group is more effective than the larger, positively charged F3 molecule, that a maximum in tumor-targeting efficiency and blood half-life is observed with ≈60 CREKA peptides per NW for either the HT1080 or theMDA-MB-435 tumor types, and that incorporation of a 5-kDa polyethylene glycol linker improves targeting to both tumor types relative to a short linker. It is concluded that the blood half-life of a targeting molecule–nanomaterial ensemble is a key consideration when selecting the appropriate ligand and nanoparticle chemistry for tumor targeting.

The controlled manipulation of small volumes of liquids is a challenging problem in microfluidics, and it is a key requirement for many high-throughput analyses and microassays. One-dimensional photonic crystals made from porous silicon have been constructed with amphiphilic properties. When prepared in the form of micrometre-sized particles and placed in a two-phase liquid such as dichloromethane/water, these materials will accumulate and spontaneously align at the interface. Here we show that superparamagnetic nanoparticles of Fe(3)O(4) can be incorporated into the porous nanostructure, allowing the materials to chaperone microlitre-scale liquid droplets when an external magnetic field is applied. The optical reflectivity spectrum of the photonic crystal displays a peak that serves to identify the droplet. Two simple microfluidics applications are demonstrated: filling and draining a chaperoned droplet, and combining two different droplets to perform a chemical reaction. The method provides a general means for manipulating and monitoring small volumes of liquids without the use of pumps, valves or a microfluidic container.

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Enabled by their size and supramolecular structures, nanoparticles (that is, particles of approximately 10 to 100 nanometers) promise to be particularly capable agents in the detection, diagnosis, and treatment of cancer. When loaded with chemotherapeutic agents, nanoparticle delivery to cancerous tissues relative to healthy tissues may be favorably biased by size and through the attachment of targeting ligands to the surface of the particle. Nanoparticles may be made from a variety of materials, and in addition to chemotherapeutic payloads, nanoparticles can incorporate non-bioactive elements useful as diagnostic and device agents. For example, the inclusion of iron oxide colloids enables nanoparticle use as magnetic resonance imaging (MRI) contrast agents, and also, through the application of an alternating magnetic field (AMF), enables the particle to generate enough heat to be used for hyperthermic therapeutic applications. In this report, we also introduce novel Magnetic Nanoparticle Hydro-Gel (MagNaGel TM ) materials comprised of chemotherapeutic agents, iron oxide colloids, and targeting ligands. MagNaGel particles were fabricated in the 20-to 40-nm size range with very narrow size dispersion. These particles demonstrate high (410 wt %) chemotherapeutic loading, tumor-associated biomolecular binding, good magnetic susceptibility, and attractive toxicity and circulation profiles in mouse models. Looking forward, the convergence of drug and device on the nano-scale promises treatment modalities that cannot be practiced through traditionally distinct drug and device combinations. MagNaGel nanoparticles are drug-device hybrids that, when used in conjunction with diagnostic MRI and inductive heating, may play a key role in new and powerful cancer treatment regimens. Drug Dev. Res. 67:70-93, 2006.