Dendritic Nanoparticles Research Articles

Aggregation Phenomena of Host and Guest upon the Loading of Dendritic Core-Multishell Nanoparticles with Solvatochromic Dyes

We systematically assessed the loading behavior of core-multishell nanoparticles (CMS NPs) for the solvatochromic dyes Coumarin 153 and Nile Red and studied the influence of the guest and its concentration on CMS NP aggregation using steady state absorption and fluorescence spectroscopy and dynamic light scattering (DLS). These measurements revealed the strong fluorescence of dye-loaded CMS NPs and formation of nonemissive dye aggregates in the outer CMS layer at higher loading concentrations of Nile Red, whereas in the case of Coumarin 153, a new species with red-shifted absorption and blue-shifted emission appeared. Moreover, dye loading triggers an aggregation of CMS NPs which have a hydrodynamic radius of 8 nm, thereby leading to CMS aggregates with a radius of 100–120 nm. These results underline the need for systematic studies of the influence of the guest and its loading concentration on CMS NP size for cellular uptake and in vivo imaging studies and the rational design of CMS NPs with improved transport and targeting abilities.

Autonomous Movement of Controllable Assembled Janus Capsule Motors

We demonstrate the first example of a self-propelled Janus polyelectrolyte multilayer hollow capsule that can serve as both autonomous motor and smart cargo. This new autonomous Janus capsule motor composed of partially coated dendritic platinum nanoparticles (Pt NPs) was fabricated by using a template-assisted layer-by-layer (LbL) self-assembly combined with a microcontact printing method. The resulting Janus capsule motors still retain outstanding delivery capacities and can respond to external stimuli for controllable encapsulation and triggered release of model drugs. The Pt NPs on the one side of the Janus capsule motors catalytically decompose hydrogen peroxide fuel, generating oxygen bubbles which then recoil the movement of the capsule motors in solution or at an interface. They could autonomously move at a maximum speed of above 1 mm/s (over 125 body lengths/s), while exerting large forces exceeding 75 pN. Also, these asymmetric hollow capsules can be controlled by an external magnetic field to achieve directed movement. This LbL-assembled Janus capsule motor system has potential in making smart self-propelling delivery systems.

Electrochemical DNA biosensor for the detection of Listeria monocytogenes with dendritic nanogold and electrochemical reduced graphene modified carbon ionic liquid electrode

A new electrochemical DNA biosensor was fabricated by using a dendritic gold nanoparticles and electrochemical reduced graphene (GR) composite modified carbon ionic liquid electrode (CILE) as the platform. Ionic liquid 1-butylpyridinium hexafluorophosphate was used as the binder for the preparation of CILE and GR film was further decorated on the CILE surface by electrochemical reduction. Then the dendritic nanogold was electrodeposited on the surface of GR/CILE to get a modified electrode as Au/GR/CILE, which was further used for the formation of mercaptoacetic acid self-assembling film. The amino modified ssDNA probe sequence was covalently linked with mercaptoacetic acid to get the ssDNA modified electrode for the further hybridization. Methylene blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction after hybridized with the target ssDNA. Under the optimal conditions the specific Listeria monocytogenes hly ssDNA sequences could be detected by measuring the differential pulse voltammetric responses of the accumulated MB molecules on dsDNA molecules. The linear concentration range was achieved from 1.0×10−12 to 1.0×10−6mol/L with the detection limit as 2.9×10−13mol/L (3σ). This electrochemical DNA sensor exhibited excellent selectivity with the good discrimination ability of one-base and three-base mismatched ssDNA sequences. The polymerase chain reaction product of L. monocytogenes hly gene that extracted from deteriorated fish was successfully detected, which indicated that this electrochemical DNA sensor could be further used for the detection of specific ssDNA sequence in real biological samples.

Dendritic Nanoparticles: the Next Generation of nanocarriers?

Dendritic polymers have attracted a great deal of scientific interest due to their well-defined unique structure and capability to be multifunctionalized. Here we present a comprehensive overview of various dendrimer-based nanomaterials that are currently being investigated for therapeutic delivery and diagnostic applications. Through a critical review of the old and new dendritic designs, we highlight the advantages and disadvantages of these systems and their structure-biological property relationships. This article also focuses on the major challenges facing the clinical translation of these nanomaterials and how these challenges are being (or should be) addressed, which will greatly benefit the overall progress of dendritic materials for theranostics.

Dendritic PtCo alloy nanoparticles as high performance oxygen reduction catalysts

We proposed a facile route to one-step synthesis of well-dispersed PtCo alloy nanoparticles with dendritic morphology. Platinum acetylacetonate [Pt(acac)2] and cobalt acetylacetone [Co(acac)2] were chosen as the precursors to prepare PtCo alloy nanoparticles under a relatively mild condition with anhydrous ethylenediamine and poly(vinyl pyrrolidone) (PVP) as solvent and surfactant, respectively, in the presence of NaBH4. Structural characterizations with transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) revealed that PtCo nanoparticles possess an interesting dendritic morphology with excellent structural continuity and integrity. As an alternative cathodic electrocatalyst, PtCo nanodendrites (NDs) showed very high activity for oxygen reduction reaction (ORR) with half-wave potential at ∼0.877V (versus RHE), which is nearly 50mV more positive as compared with that of the commercial Pt/C catalyst (0.828V). The Pt mass activity and specific activity were 0.11A/mgPt and 0.68mA/cm2, respectively (∼1.5 and ∼4.5 times higher than the corresponding values for the commercial Pt catalysts), at 0.9V.

Optoelectronic properties of RNA–polyaniline–dendritic gold nanobiocomposite

The in situ reduction of Au+++ by aniline in the presence of RNA produces dendritic Au nanoparticles (AuNP) with the concomitant formation of doped polyaniline (PANI). FT-IR spectra indicate that the dendritic AuNPs are stabilized from the complexation of nitrogen atoms of quinonoid structure of PANI with the adsorbed Au+++ on it. CD spectrum indicates a small distortion of RNA ‘A’ helix toward ‘B’ helix. RNA–PANI–Au nanocomposite shows emission peak at 408nm with an additional peak at 579nm for the Forster resonance energy transfer (FRET) of PANI excitons to surface plasmon band of Au nanocrystals. The dendritic RNA–PANI–Au nanocomposite has three orders higher dc-conductivity compared to the spherical PANI–Au composite. Impedance data suggest that the system behaves as an equivalent parallel resistance–capacitance (R–C) circuit. The frequency dependency of ac-conductivity indicates three regions of conduction: at low frequency predominantly intrachain conduction by polarons of doped PANI, at medium frequency hopping of polarons through RNA and AuNP along with the intra-chain conduction and at very high frequency the conductivity is predominantly interchain due to localized hopping.

Abstract 1947: Self-reporting dendritic nanoparticles (nanodendrons) for drug delivery targeted to the tumor microenvironment and with reduced neurotoxicity

Abstract Proteinases, including matrix metalloproteinases (MMPs), contribute to cancer progression and other pathologies. Selective MMP expression can be used to distinguish benign from malignant tumors and identify aggressive tumors associated with poor outcome. MMP9, a basement membrane-degrading type-IV collagenase/gelatinase, is associated with tumor invasion and metastasis. In this project, we describe a new class of dendritic nanoparticles, nanodendrons (NDs), with MMP molecular recognition and targeting capabilities. These NDs can be studied as individual dendrons tuned for specific functions such as enhanced imaging or targeted drug treatments. Additionally, the NDs can be coupled to facilitate multifunctional purposes such as in NDs that can self-report drug delivery to tumors. The prototypical system presented here describes NDs that are activated by MMP9: 1) ND-PB, a near infrared imaging beacon; 2) ND-PXL, a therapeutic that delivers paclitaxel (PXL) and 3) NDPB-NDPXL, a bi-functional agent. In vivo studies in two orthotopic models of breast cancer demonstrate efficacy of these NDs to image and treat breast cancer. The proteinase-activated prodrug, NDPXL, delivers PXL to breast cancer through release of the drug in the tumor microenvironment and increases therapeutic efficacy while reducing systemic toxicity (including peripheral neuropathy). The delivery of PXL using the proteolytically activated ND-PXL is effective in inhibiting tumor growth in two orthotopic models of breast cancer (PyVT-R221A and MDA-MB231). Daily treatment of MDA-MB231 tumors with 12.5 mg/kg PXL as either ND-PXL or Abraxane® (Abx), showed similar reduction in tumor growth as compared with vehicle-treated animals. Further investigation of the NDPXL in a fully immunocompetent mouse model (PyVT-R221A) with treatments given on alternate days at a dose of 12.5 mg/kg (ND-PXL or Abx) yielded similar results: an average reduction in tumor growth of 58% and 53% in ND-PXL and Abx cohorts, respectively. Peripheral nerve toxicity, a debilitating, long term side effect of Abx therapy, was assessed in both tumor and non-tumor mice through monitoring behavior indicative of peripheral nerve damage before, during and after administration of each drug. Peripheral neurotoxicity is markedly reduced in the ND-PXL-treated versus Abraxane®-treated mice as evident in a number of behavioral assessments. The development of this novel class of NDs expands upon the current capabilities of modern proteinase-based optical beacons and prodrugs and is a step forward in treatment of both primary and metastatic cancer. [Supported in part by Susan G. Komen for the Cure®] Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1947. doi:1538-7445.AM2012-1947

Synthesis of polymer-supported dendritic palladium nanoparticle catalysts for Suzuki coupling reaction

New bead-shaped heterogeneous nanoparticle catalysts viz., amino-terminated poly(amidoamine) (PAMAM) grafted on poly(styrene)-co-Poly(vinylbenzylchloride) (PS-Poly(VBC)) matrices immobilized/stabilized with palladium nanoparticle were prepared by simplified procedure. The first step is the preparation of PS-Poly(VBC) beads by suspension polymerization method. Second, the PAMAM G(0) G(1) and G(2) dendrimers were grafted individually onto the PS-Poly(VBC) matrices via divergent method by repeating two reactions, i.e., Michael addition of methyl acrylate to surface amino groups of aminomethylated PS-Poly(VBC) matrixes followed by amidation of the resulting esters with ethylene diamine. The resulting three types of PAMAM G(0), G(1) and G(2) grafted on PS-Poly(VBC) matrices were complexed individually with PdCl2 and thus yielded the corresponding new bead-shaped heterogeneous nanoparticle catalyst immobilized with PdNPs. The appearance of surface plasmon resonance band noticed at 547 nm in UV confirms the formation of PdNPs. The SEM result shows that the intensity of white patches due to immobilization of PdNPs increases with generation number and XRD reveals that the crystalline nature was decreased against generation number of the PAMAM. The catalytic efficiency of PS-Poly(VBC)-NH2-PdNPs-G(0), G(1) and G(2) catalysts were examined by Suzuki coupling reaction performed in mixture of water/ethanol. The observed reaction yield reveals that the activity was proportional to the generation number of PAMAM grafted onto the PS-Poly(VBC) matrices. The percentage of reaction yield (biphenyl) is sustained to ≈70 % even up to five cycles and this in turn confirms the stability of the catalysts. These catalysts can be used to conduct the Suzuki-coupling reaction in continuous mode operation in industrial scale.

In vivo tumor imaging using a novel RNAi-based detection mechanism

A new concept of tumor imaging is introduced using a siRNA-based probe that is capable of amplifying a specific endogenous fluorescence emission in cancerous tissue. In previous studies, we demonstrated a significant downregulation of Ferrochelatase (FECH) mRNA-expression in colorectal carcinomas leading to the accumulation of protoporphyrin IX (PpIX), a fluorescent metabolite of the heme synthesis. In this article, we report on first in vivo experiments in xenografted nude mice using folate-coupled liposomes or dendritic polyglycerolamine nanoparticles carrying ferrochelatase-siRNA to enhance PpIX-derived fluorescence in the tumor tissue. Tiny tumor foci could be monitored by the emission of PpIX fluorescence in vivo. Due to the omnipresence of the heme synthesis pathway, targeted application of ferrochelatase-siRNA may provide a general means for molecular imaging. From the Clinical EditorA new concept of tumor imaging is presented in this paper using a siRNA-based probe detecting protoporphyrin IX (PpIX), a fluorescent metabolite of the heme synthesis previously demonstrated to accumulate in cancer tissue.

Highly Active Nanoreactors: Nanomaterial Encapsulation Based on Confined Catalysis

It happens inside: highly active nanoreactors are prepared by encapsulating dendritic Pt nanoparticles (NPs) grown on a polystyrene template inside hollow porous silica capsules. The catalytic activity of these Pt NPs is preserved after encapsulation and template removal. Different metals, such as Ni, can thus be reduced inside the capsules, thereby leading to the formation of composites with tunable magnetic properties.

Construction of dsDNA biosensor based on dendritic SiO2 nanoparticle and investigation on its interaction with benzo[a]pyrene

In this work, a new dsDNA biosensor was constructed to monitor the interaction of DNA and benzo[a]pyrene (BaP). Firstly, dendritic SiO2 nanoparticles were synthesized by silanization of SiO2 nanoparticles with (γ-(methacryloyloxy)propyl) trimethoxysilane and polymerization with acrylic acid. Then, due to the rich carboxyl groups of these nanoparticles, they were associated with the amino groups of a self-assembly membrane formed on the gold electrode by a sulfur-containing compound, 5-amino-3-mercapto-1,2,4-triazole. Finally, dsDNA was immobilized on the electrode surface by static adsorption with the aid of metallic ion. The whole immobilization steps were characterized by cyclic voltammogram and electrochemical impedance spectrum. After that, using methylene blue as a probe, the interaction of BaP with dsDNA was investigated. A linear relationship between the percentages of current decrease with the logarithm of BaP concentrations was found in the range from 0.33 to 133 μM.

One-step and rapid synthesis of “clean” and monodisperse dendritic Pt nanoparticles and their high performance toward methanol oxidation and p-nitrophenol reduction

Well-defined and monodisperse dendritic platinum nanoparticles (DPNs) are successfully prepared by a rapid, one-step, and efficient route with high yield in aqueous solution, wherein neither organic solvents nor surfactants are employed, ensuring the as-made DPNs definitely have "clean" surfaces, allowing them to exhibit high activity for both methanol oxidation and p-nitrophenol reduction. This proposed strategy for simple and facile preparation of "clean" metal nanocatalysts paves the way for accurately evaluating and further improving their intrinsic catalytic activity.

Transbuccal Delivery of CNS Therapeutic Nanoparticles: Synthesis, Characterization, and In Vitro Permeation Studies

This work utilized polyamidoamine (PAMAM) dendrimer G4.5 as the underlying carrier to construct CNS therapeutic nanoparticles and explored the buccal mucosa as an alternative absorption site for administration of the dendritic nanoparticles. Opioid peptide DPDPE was chosen as a model CNS drug. It was coupled to PAMAM dendrimer G4.5 with polyethylene glycol (PEG) or with PEG and transferrin receptor monoclonal antibody OX26 (i.e., PEG-G4.5-DPDPE and OX26-PEG-G4.5-DPDPE). The therapeutic dendritic nanoparticles labeled with 5-(aminoacetamido) fluorescein (AAF) were studied for transbuccal transport using a vertical Franz diffusion cell system mounted with porcine buccal mucosa. For comparison, AAF-labeled PAMAM dendrimers G3.5 and G4.5, and fluorescein isothiocynate (FITC)-labeled G3.0 and G4.0 were also tested for transbuccal delivery. The permeability of PEG-G4.5 (AAF)-DPDPE and OX26-PEG-G4.5(AAF)-DPDPE were on the order of 10(-7) - 10(-6) cm/s. Coadministration of bile salt sodium glycodeoxycholate (NaGDC) enhanced the permeability of dendritic nanoparticles by multiple folds. Similarly, a multifold increase of permeability of dendritic nanoparticles across the porcine buccal mucosal resulted from the application of mucoadhesive gelatin/PEG semi-interpenetrating network (sIPN). These results indicate that transbuccal delivery is a possible route for administration of CNS therapeutic nanoparticles.

Size and surface charge significantly influence the toxicity of silica and dendritic nanoparticles

The influence of size, surface charge and surface functionality of poly(amido amine) dendrimers and silica nanoparticles (SNPs) on their toxicity was studied in immunocompetent mice. After systematic characterization of nanoparticles, they were administered to CD-1 (caesarean derived-1) mice to evaluate acute toxicity. A distinct trend in nanotoxicity based on surface charge and functional group was observed with dendrimers regardless of their size. Amine-terminated dendrimers were fatal at doses >10 mg/kg causing haematological complications such as disseminated intravascular coagulation-like manifestations whereas carboxyl- and hydroxyl-terminated dendrimers of similar sizes were tolerated at 50-fold higher doses. In contrast, larger SNPs were less tolerated than smaller SNPs irrespective of their surface functionality. These findings have important implications in the use of these nanoparticles for various biomedical applications.

Structural Characterization and Catalytic Activity of Pt Dendrimer Encapsulated Nanoparticles Supported Over Al<SUB>2</SUB>O<SUB>3</SUB> for SCR of NO<SUB><I>x</I></SUB>

Pt/Al2O3 and Pt-Mg/Al2O3 nano composites were successfully prepared by dendrimer templated synthesis route. The obtained dendritic nanoparticles were dispersed in alumina support and they were evaluated for SCR of NOx using methane as reductant. Thermal analysis results of uncalcined samples revealed that the oxygen can accelerate the rate of dendrimer shell decomposition. X-ray diffractograms of 500 degrees C calcined samples disclosed the amorphous nature of materials, whereas 1000 degrees C air calcined samples showed enhanced crystallinity as well as diffraction pattern corresponding to Pt and PtO. HRTEM images of Pt40-G4OH dendritic nanoparticles showed uniform particulate distribution with average particle size of 2.4 nm. The STEM results of 0.5 Pt/Al2O3 sample calcined at 500 degrees C exhibited a wide range of particles between 2 and 20 nm. This indicates the huge segregation of platinum metal particles during impregnation and subsequent calcination. Among the synthesized materials 0.5 wt% Pt/Al2O3 sample showed excellent conversion and selectivity for SCR of NOx.

Self-assembled synthesis of Ag nanodendrites and their applications to SERS

In this paper, SiO 2 nanoparticles were synthesized using self-assembly for their fabrication. The SiO 2 particles as a micro reactor were soaked into silver nitrate (AgNO 3) aqueous solution. The dendritic Ag nanoparticles were prepared by a reaction of AgNO 3 with template agent (CTAB) and AgBr decomposed into elemental Ag nanoparticles under visible light irradiation on the SiO 2 micro reactor. The morphology and structure of synthesized Ag dendrites were determined by employing following techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV–vis). The correlated surface-enhanced Raman scattering (SERS) effects have been investigated when 2-Mercaptobenzothiazole (2-MBT) was used as a Raman probe. Especially, the possible growth process was proposed by arresting the growth at a series of intermediate morphology stages during the shape evolution of Ag dendrites based on TEM observations. The results clearly showed that the dendritic Ag nanostructures could be obtained through oriented attachment of nanoparticles along a crystallographically special direction and the morphology of the dendrites was dependent on the reaction duration. Moreover, the investigation of the SERS revealed that the Ag nanodendrites were an excellent substrate with significant enhancement effect.

In Vitro Cytotoxicity and Intracellular Bioimaging of Dendritic Platinum Nanoparticles by Differential Interference Contrast (DIC)

Abstract We demonstrated the excellent biocompatibility of dendritic platinum nanoparticles (DPNs) in vitro using a cancer cell line (BT-20) and MTT assay. In addition, a successful observation of DPNs within live cells using differential interference contrast (DIC) microscopy without labelling fluorescent dyes has been achieved.

Concomitant synthesis of polyaniline and highly branched gold nanoparticles in the presence of DNA

The reduction of chloroauric acid using aniline adsorbed on DNA produces highly branched dendritic gold nanoparticles with concomitant formation of polyaniline (PANI) in contrast to the formation of spherical Au nanoparticles in the absence of DNA. The conformation of DNA remains intact in the process as evident from circular dichroism (CD) spectra. The UV–Vis spectrum exhibits a broad absorption peak at 520–900 nm, for a combined effect of the gold surface plasmon and π band to localized polaron band transition of DNA-doped PANI. Both the dendritic Au–PANI–DNA and the spherical Au–PANI systems emit two peaks for excitation with radiation of 300 nm and the intensity ratio of the emission and FRET peak is higher in the dendritic Au–PANI than that in the spherical Au–PANI system. The dc-conductivity values of spherical Au–PANI and dendritic Au–PANI–DNA systems are 1.2 × 10 −10 and 1.7 × 10 −8 S/cm at 30 °C, respectively.

A dendritic nanosilica-functionalized electrochemical immunosensor with sensitive enhancement for the rapid screening of benzo[a]pyrene

A novel electrochemical immunosensor has been fabricated for the detection of benzo[a]pyrene using dendritic SiO2 nanoparticles for biomolecule immobilization. Initially, carboxyl-terminated dendritic SiO2 nanoparticles were synthesized, characterized by TEM, contact angle and thermogravimetric analyses, and then immobilized onto an ethylenediamine-modified electrode. Aminopyrene–BSA was captured with the carboxyl groups of dendritic SiO2 nanoparticles, followed by the corresponding antibody and HRP-labeled secondary antibody. Finally, with the aid of H2O2 and hydroquinone, the changes in the cathodic current were recorded. Based on a competitive immunoassay, benzo[a]pyrene, which can compete with the immobilized aminopyrene–BSA in the association ability of the antibody, was successfully detected. The results showed that the cathodic currents were linearly dependent on the logarithm of benzo[a]pyrene concentrations between 0.01 and 10μM with a detection limit of 8nM. The proposed electrochemical immunosensor provided a new alternative to the application of other antigens or other bioactive molecules.

One‐Pot Synthesis of Carbon‐Supported Dendritic Pd‐Au Nanoalloys for Electrocatalytic Ethanol Oxidation

One-pot synthesis of carbon-supported Pd-Au alloy nanoparticles with well-defined dendritic shape (Pd-Au(den)/C) was achieved by co-reduction of K(2)PdCl(4)/HAuCl(4) mixtures in a molar ratio of 1:1 with hydrazine in the presence of Vulcan XC-72R. The prepared Pd-Au(den)/C exhibited significantly enhanced performance in the electrocatalytic oxidation of ethanol compared with dendritic Pd nanoparticles and a commercial Pd/C catalyst. Pd-Au(den)/C even showed higher durability in electro-oxidation of ethanol than the supported catalyst prepared by the deposition of presynthesized dendritic Pd-Au nanoparticles on the carbon support. The experimental results clearly indicate that enhanced interaction between nanoparticle catalysts and carbon support through the one-pot synthesis protocol can improve the durability of the electrocatalysts.