Facile synthesis of stable, water soluble, dendron-coated gold nanoparticles

Targeted Doxorubicin-Loaded Dendronized Gold Nanoparticles

Dendronized nanoparticles, also called nanoparticle-cored dendrimers, combine the advantages of nanoparticles and dendrimers. These very stable and polyvalent nanoparticles can be used for diverse applications. One such application is drug delivery, because the dendrons can enhance the density of the payload. In this report, we describe the design of multifunctional gold nanoparticles (AuNPs) coated with poly(propylene imine) (PPI) dendrons that contain both prostate cancer active targeting and chemotherapeutic drugs. The PPI dendron is a good candidate for the design of drug delivery vehicles because of its ability to induce a proton sponge effect that will enhance lysosomal escape and intracellular therapeutic delivery. The chemotherapeutic drug used is doxorubicin (DOX), and it was linked to the dendron through a hydrazone acid-sensitive bond. Subsequent acidification of the AuNP system to a pH of 4-5 resulted in the release of 140 DOX drugs per nanoparticles. In addition, the PPI dendron was conjugated via "click" chemistry to an EphA2-targeting antibody fragment that has been shown to target prostate cancer cells. In vitro cell viability assays revealed an IC50 of 0.9 nM for the targeted DOX-bearing AuNPs after 48 h incubation with PC3 cells. These results are very promising upon optimization of the system.

Properties and Bioapplications of Amphiphilic Janus Dendrimers: A Review

Amphiphilic Janus dendrimers are arrangements containing both hydrophilic and hydrophobic units, capable of forming ordered aggregates by intermolecular noncovalent interactions between the dendrimer units. Compared to conventional dendrimers, these molecular self-assemblies possess particular and effective attributes i.e., the presence of different terminal groups, essential to design new elaborated materials. The present review will focus on the pharmaceutical and biomedical application of amphiphilic Janus dendrimers. Important information for the development of novel optimized pharmaceutical formulations, such as structural classification, synthetic pathways, properties and applications, will offer the complete characterization of this type of Janus dendrimers. This work will constitute an up-to-date background for dendrimer specialists involved in designing amphiphilic Janus dendrimer-based nanomaterials for future innovations in this promising field.

Gold Nanoparticles Modification with Liquid Crystalline Polybenzylic Dendrons via 1,3-Dipolar Cycloaddition

A series of six polybenzylic dendrons with an alkynyl focal point were synthesized for their incorporation to gold nanoparticles. Five of these compounds showed columnar mesomorphism in a wide range of temperatures. These dendrons were reacted with gold nanoparticles stabilized with a combination of a dodecanethiol and 11-azidoundecane-1-thiol. The azido group of the last compound allowed the functionalization of the nanoparticles with the six polybenzylic dendrons by 1,3-dipolar cycloaddition between their alkynyl groups and the terminal azido groups of the thiols. A high efficiency of the cycloaddition process (47-69%) was confirmed by several experimental techniques and no decomposition or aggregation phenomena were detected in the dendron-coated nanoparticles. The involved mechanism and the resulting percentage composition of the final materials are discussed. The results of the ulterior growth of the nanoparticles by thermal treatment are influenced by the size and the shape of the dendron and the temperature of the process. The structures of the final nanoparticles were investigated by TEM, DSC, TGA, NMR and UV-Vis spectroscopy. These nanoparticles do not show liquid crystal properties. However, a melting process between a crystalline and a fluid phase is observed. In the solid phase, the nanomaterials prepared show a short-range interaction between nanoparticles with a 2D local hexagonal order. A near-field effect was observed in the UV-vis spectra by coupling of different surface plasmon resonance bands (SPR) probably due to the short-range interactions. The main novelty of this work lies in the scarcity of previous studies of gold nanoparticles coated with dendrons forming themselves columnar mesophases. Most of the studies reported in the literature deal with gold nanoparticles coated with calamitic mesogens. Additionally, the effect of the thermal treatment, which in a previous paper was shown to increase the mean size of the nanoparticles without increasing their size polydispersity, has been studied in these materials.

Arylated gold nanoparticles have no effect on the adipogenic differentiation of MG-63 cells nor regulate any key signaling pathway during the differentiation

OBJECTIVE

MG-63 cells that have osteoblastic and adipogenic differentiation potential were evaluated for internalization, and adipogenic differentiation in the presence and absence of the covalently functionalized aryl gold nanoparticles (AuNPs-C6H4-4-COOH).

RESULTS

Inductively coupled plasma, flow cytometry and confocal microscopy analyses confirmed that gold nanoparticles were easily internalized by MG-63 cells. The MG-63 cells were differentiated into adipocytes without gold-aryl nanoparticles and with the gold-aryl nanoparticles at 5 µM concentration in both induction and maintenance media. The lipid content assay and the relative expressions of PPAR-γ, ADR1, GLUT1 and GLUT4 genes showed no significant variation with and without the gold nanoparticles treatment. Differential phosphorylation levels of 43 kinases phosphorylation sites were evaluated using the human phospho-kinase array to assess the effect of the gold nanoparticles on the signaling pathways during the differentiation. No kinase phosphorylation site was differentially phosphorylated with two or more folds after the nanoparticles treatment after the first day as well as at the end of MG-63 cells differentiation. The gold-aryl nanoparticles do not affect MG-63 cells differentiation into adipocytes neither do they affect any key signaling pathway. These properties make these gold nanoparticles suitable for future drug delivery and medical applications.

Engineered non-invasive functionalized dendrimer/dendron-entrapped/complexed gold nanoparticles as a novel class of theranostic (radio)pharmaceuticals in cancer therapy

Nanomedicine represents a very significant contribution in current cancer treatment; in addition to surgical intervention, radiation and chemotherapeutic agents that unfortunately also kill healthy cells, inducing highly deleterious and often life-threatening side effects in the patient. Of the numerous nanoparticles used against cancer, gold nanoparticles had been developed for therapeutic applications. Inter alia, a large variety of dendrimers, i.e. soft artificial macromolecules, have turned up as non-viral functional nanocarriers for entrapping drugs, imaging agents, and targeting molecules. This review will provide insights into the design, synthesis, functionalization, and development in biomedicine of engineered functionalized hybrid dendrimer-tangled gold nanoparticles in the domain of cancer theranostic. Several aspects are highlighted and discussed such as 1) dendrimer-entrapped gold(0) hybrid nanoparticles for the targeted imaging and treatment of cancer cells, 2) dendrimer encapsulating gold(0) nanoparticles (Au DENPs) for the delivery of genes, 3) Au DENPs for drug delivery applications, 4) dendrimer encapsulating gold radioactive nanoparticles for radiotherapy, and 5) dendrimer/dendron-complexed gold(III) nanoparticles as technologies to take down cancer cells.

Efficient synthesis of amino acids capped gold nanoparticles from easily reducible aryldiazonium tetrachloroaurate(III) salts for cellular uptake study

Biomimetic synthesis of gold nanoparticles (GNPs) is critical in biomedical applications. Gold bioconjugates were fabricated by capping the water-dispersible gold-carbon nanoparticles with tyrosine, tryptophan and cysteine amino acids. Incubation of the water-soluble and easily reducible aryldiazonium gold(III) salt [HOOC-4-C₆H₄N≡N]AuCl₄ with amino acids at room temperature formed a purple color over a few minutes with tryptophan and tyrosine and over two hours with cysteine. Rarely that cysteine is capable of reducing gold(III) precursors; however, a cysteine capped gold bioconjugate was synthesized and characterized in this study. Capping GNPs with amino acids was confirmed by high resolution transmission electron microscopy (TEM) and agarose gel electrophoresis. Depending on the amino acid, synthesized particles size was 27.2 ± 5.4 nm, 14.6 ± 7.7 nm and 8.6 ± 2.6 nm for tyrosine, tryptophan and cysteine, respectively. The amino acids capped GNPs showed negligible cytotoxicity to human dermal normal fibroblast cell lines. The highly water dispersible bioconjugates were studied for in vitro cellular uptake by HeLa cancer cells using confocal laser scan microscopy (CLSM) after being labelled with FITC (GNPs-COOH-FITC) and the nuclei were counter stained with DAPI fluorescent dyes. The biomimetic route for the synthesis of the amino acids reduced gold-carbon nanoparticles will benefit the applications in biomedical devices and biosensors.

Diazonium Gold Salts as Novel Surface Modifiers: What Have We Learned So Far?

The challenges of diazonium salts stabilization have been overcome by their isolation as metal salts such as tetrachloroaurate(III). The cleavage of molecular nitrogen from diazonium salts even at very low potential or on reducing surfaces by fine tuning the substituents on the phenyl ring expanded their applications as surface modifiers in forensic science, nanomedicine engineering, catalysis and energy. The robustness of the metal–carbon bonding produced from diazonium salts reduction has already opened an era for further applications. The integration of experimental and calculations in this field catalyzed its speedy progress. This review provides a narrative of the progress in this chemistry with stress on our recent contribution, identifies potential applications, and highlights the needs in this emerging field. For these reasons, we hope that this review paper serves as motivation for others to enter this developing field of surface modification originating from diazonium salts.

Denatured proteins as a novel template for the synthesis of well-defined, ultra-stable and water-soluble metal nanostructures for catalytic applications

Abstract

The templated synthesis of noble metal nanoparticles using biomass, such as proteins and polysaccharides, has generated great interest in recent years. In this work, we report on denatured proteins as a novel template for the preparation of water-soluble metal nanoparticles with excellent stability even after high speed centrifugation or storage at room temperature for one year. Different noble metal nanoparticles including spherical gold and platinum nanoparticles as well as gold nanoflowers are obtained using sodium borohydride or ascorbic acid as the reducing agent. The particle size can be controlled by the concentration of the template. These metal nanoparticles are further used as catalysts for the hydrogenation reaction of p-nitrophenol to p-aminophenol. Especially, spherical gold nanoparticles with an average size of 2 nm show remarkable catalytic performance with a rate constant of 1.026 × 10− 2 L s− 1 mg− 1. These metal nanoparticles with tunable size and shape have great potential for various applications such as catalysis, energy, sensing, and biomedicine.

Graphical abstract

Set of Highly Stable Amine- and Carboxylate-Terminated Dendronized Au Nanoparticles with Dense Coating and Nontoxic Mixed-Dendronized Form

The synthesis of a novel poly(propyleneimine) (PPI) dendron in gram scale as well as its use in the formation of a highly stable, dendronized gold nanoparticle (AuNP)-based drug delivery platform is described herein. The AuNP-based platform is composed of three complementary parts: (i) a 15 nm AuNP core, (ii) a heterofunctional thioctic acid-terminated tetraethylene glycol spacer, and (iii) a third-generation PPI dendron with a unique protonation profile and diverse end-group functionalization that allows for further derivatization. The prepared dendronized AuNPs are able to withstand several rounds of lyophilization cycles with no sign of aggregation, are stable in phosphate-buffered saline and Hanks' buffer as well as in serum, and are resistant to degradation by glutathione exchange reactions. This nanocarrier platform displays a dense coating, with >1400 dendrons/AuNPs, which will enable very high payload. Furthermore, while amine-terminated AuNPs expectedly showed cytotoxicity against the MCF-7 breast cancer cell line from a NP concentration of 1 nM, the mixed monolayer AuNPs (coated with 40/60 amine/carboxylate dendrons) interestingly did not exhibit any sign of toxicity at concentrations as high as 15 nM, similar to the carboxylate-terminated AuNPs. The described dendronized AuNPs address the current practical need for a stable NP-based drug delivery platform which is scalable and easily conjugable, has long-term stability in solution, and can be conveniently formulated as a powder and redispersed in desired buffer or serum.