Gold-doxorubicin nanoconjugates for overcoming multidrug resistance.

Multidrug resistance (MDR) is a major clinical obstacle to the success of cancer chemotherapy. Here we developed a gold-doxorubicin (DOX) nanoconjugates system to overcome MDR. Gold nanoparticles (AuNPs) were first PEGylated as Au-PEG-NH(2), and DOX was then grafted onto AuNPs via a cleavable disulfide linkage (Au-PEG-SS-DOX). Confocal images revealed that the extent of intracellular uptake of Au-PEG-SS-DOX was greater than that of free DOX in the MDR cells, and inductively coupled plasma mass spectroscopy analysis further confirmed that AuNPs significantly increased the level of drug accumulation in MDR cells at a nanoparticles dose greater than 15 µM. The cytotoxicity study demonstrated that the Au-PEG-SS-DOX nanoconjugates system efficiently released the anticancer drug DOX and enhanced its cytotoxicity against MDR cancer cells. This study highlights the potential of using AuNPs for overcoming of MDR in cancer chemotherapy. FROM THE CLINICAL EDITOR: This study demonstrates that gold nanoparticles can be successfully applied to overcome MDR in cancer chemotherapy.

MSOT-Guided Nanotheranostics for Synergistic Mild Photothermal Therapy and Chemotherapy to Boost Necroptosis/Apoptosis.

The development of nanotheranostics for precision imaging-guided regulated cell death-mediated synergistic tumor therapy is still challenging. Herein, a novel multifunctional nanotheranostic agent, iRGD-coated maleimide-poly(ethylene glycol)-poly(lactic acid/glycolic acid)-encapsulated hydrophobic gold nanocages (AuNCs) and hydrophilic epigallocatechin gallate (EGCG) (PAuE) is developed for multispectral optoacoustic tomography (MSOT)-guided photothermal therapy (PTT) and chemotherapy. The portions of necroptotic and apoptotic tumor cells were 52.9 and 5.4%, respectively, at 6 h post-incubation after the AuNC-induced mild PTT treatment, whereas they became 14.0 and 46.1% after 24 h, suggesting that the switch of the cell death pathway is a time-dependent process. Mild PTT facilitated the release of EGCG which induces the downregulation of hypoxia-inducible factor-1 (HIF-1α) expression to enhance apoptosis at a later stage, realizing a remarkable tumor growth inhibition in vivo. Moreover, RNA sequence analyses provided insights into the significant changes in genes related to the cross-talk between necroptosis and apoptosis pathways via PAuE upon laser irradiation. In addition, the biodistribution and metabolic pathways of PAuE have been successfully revealed by 3D MSOT. Taken together, this strategy of first combination of EGCG and AuNC-based photothermal agent via triggering necroptosis/apoptosis to downregulate HIF-1α expression in a tumor environment provides a new insight into anti-cancer therapy.

pH-Triggered Poly(ethylene glycol)-Poly(lactic acid/glycolic acid)/Croconaine Nanoparticles-Assisted Multiplexed Photoacoustic Imaging and Enhanced Photothermal Cancer Therapy.

The most advantageous and attractive property of photoacoustic imaging is its capability to visualize and differentiate multiple species according to their unique absorbance profiles simultaneously in a single mixture. We here report the pH-sensitive near-infrared (NIR) croconaine (Croc) dyes-loaded copolymeric PEG-PLGA nanoparticles (NPs) for in vivo multiplexed PA imaging and pH-responsive photothermal therapy (PTT) in an orthotopic xenograft model. PEG chains on the polymeric NPs shell were conjugated with iRGD in another set of NPs to realize efficient tumor targeting. The distribution and the intensity of two sets of iRGD-targeted and nontargeted NPs inside tumors are simultaneously imaged and monitored in vivo. Meanwhile, the utilization of iRGD-targeted PPC815 NPs as a pH-active photothermal agent with promising tumor-inhibition efficacy was demonstrated. As a result, this nanoplatform is capable of assisting multiwavelength unmixing of PA imaging as well as providing remarkable photothermal ablation for anticancer treatment.

Nuclear penetration of surface functionalized gold nanoparticles.

Free gold nanoparticles easily aggregate when the environment conditions change. Here, gold nanoparticles (AuNPs) with average diameter of 3.7 nm were prepared and then modified with poly(ethylene glycol) (PEG) to improve stability. The gold nanoparticles were first surface-modified with 3-mercaptopropionic acid (MPA) to form a self-assembled monolayer and subsequently conjugated with NH(2)-PEG-NH(2) through amidation between the amine end groups on PEG and the carboxylic acid groups on the particles. The biocompatibility and intracellular fate of PEG-modified gold nanoparticles (AuNP@MPA-PEG) were then studied in human cervical cancer (HeLa) cells. Cell viability test showed that AuNP@MPA-PEG did not induce obvious cytotoxicity. Both confocal laser scanning microscopy and transmission electron microscopy demonstrated that AuNP@MPA-PEG entered into mammalian cells and the cellular uptake of AuNP@MPA-PEG was time-dependent. Inductively coupled plasma mass spectrometry and confocal microscopy imaging further demonstrated that AuNP@MPA-PEG penetrated into the nucleus of mammalian cells upon exposure for 24 h. These results suggest that surface modification can enhance the stability and improve the biocompatibility. This study also indicates that AuNP@MPA-PEG can be used as potential nuclear targeted drug delivery carrier.

Encapsulation of Pt nanoparticles inside carbon nanotubes.

The encapsulation of Pt nanoparticles into the cavities of MWNTs was prepared by pyrolysis of a mixture of Pt acetylacetonate and MWNTs under vacuum at 500 degrees C and subsequent thermal heating to form high surface area Pt nanostructure. Pat nanoparticles with an average size of 3.0 nm were found to be highly dispersed on the outside surface of the MWNTs and encapsulated in them. For comparison, Pd and Ru nanoparticles were also investigated using the same synthetic process to further explore the filling mechanism of metal nanoparticles inside carbon nanotubes. The presence of metal nanoparticles that were attached to the MWNTs was characterized by TEM, HRTEM, and FT-IR. The filling mechanism was also proposed.

pH-responsive targeted gold nanoparticles for in vivo photoacoustic imaging of tumor microenvironments.

The acidic microenvironment of tumor tissues has been proven to be a major characteristic for differentiation from normal tissues, thereby providing a desirable target for both disease diagnosis and functional imaging. We herein introduce a way to endow gold nanoparticles with aggregation behaviour induced by pH tuning. The nanoparticle surface was modified with two thiol conjugate molecules, which could smartly stabilize it at the pH of blood and normal tissues but induce aggregation in response to the acidic extracellular pH in tumor. The surface conjugate molecule composition effect was studied systematically, and at the optimal surface conjugate molecule composition, a pH-responsive active tumor-targeting c(RGDyk)-MHDA/LSC@AuNP nanoprobe was successfully obtained and showed a significantly enhanced contrast effect for both in vitro and in vivo photoacoustic (PA) imaging. Intravenous administration of our nanoprobe to U87MG tumor-bearing nude mice showed PA imaging contrasts almost 3-fold higher than those for the blocking group. Quantitative biodistribution data revealed that 9.7 µg g-1 of nanoprobe accumulated in the U87MG tumor 4 h post-injection. These findings might provide an effective strategy for developing new classes of intelligent and biocompatible contrast agents with a high efficiency for PA imaging and PA imaging-guided cancer therapy.

Study of the Aggregation of DNA-Capped Gold Nanoparticles: A Smart and Flexible Aptasensor for Spermine Sensing.

A smart gold nanoparticle based aptasensor is developed for the sensing of this biomarker in a convenient and fast manner. A comprehensive study was performed to elucidate the driving force of DNA adsorption, different factors' effects, such as gold nanoparticle size, DNA length, concentration, and working pH towards spermine sensing by using UV/Vis absorption spectroscopy and isothermal titration calorimetry. It was found that the developed aptasensor could detect spermine by two different sensing mechanisms simply by adjusting the DNA concentration without complicated procedures. Good performance in complicated matrices was proven by the satisfactory results obtained in the spike analysis of both artificial urine and clinical urine samples. Such a flexible and smart approach described here would provide a useful tool for the fast sensing of spermine and prostate cancer screening.

PET imaging with multimodal upconversion nanoparticles.

A series of new upconversion nanoparticles have been functionalised with tumour-targeting molecules and metal chelates, prepared following standard peptidic and thiol chemistry. The targeting strategy has been delivered via the αvß3 integrin, which is a heterodimeric cell surface receptor that is up-regulated in a variety of cancers, such as melanoma and breast cancer. The well-known DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) motif allows coordination to the radionuclide (68)Ga. Radiolabelling experiments were optimised under relatively mild conditions, and are rare amongst nanoparticulate materials. In vivo application of these probes in mouse tumour models revealed their potential as specific cancer contrast agents for PET imaging.

Surface functionalized gold nanoparticles for drug delivery.

Gold nanoparticles have been widely explored as cancer therapeutics and diagnostic agents in recent years. With their unique subcellular size and good biocompatibility, gold nanoparticles are a promising drug delivery vehicle. In this study, folic acid-coated gold nanoparticles conjugated with fluorophore FITC through amine terminated poly(ethylene glycol) were prepared and confocal microscopy together with bright-field differential interference contrast imaging data showed that folic acid-coated gold nanoparticles accumulated mainly in cytoplasm of primary human fibroblasts, without causing any observable cytotoxicity upon exposure for 48 hours. Through the further development of a drug delivery system that conjugates doxorubicin onto the surface of gold nanoparticles with a poly(ethylene glycol) spacer via an SMCC linker, we demonstrated that multidrug resistance in cancer cells can be significantly overcome by a combination of highly efficient cellular entry and enhanced cytotoxicity of Au-SMCC-DOX nanoconjugates, as revealed both by confocal microscopy imaging and cytotoxicity assay. The prepared Au-SMCC-DOX nanoconjugates demonstrated enhanced drug accumulation and retention in multidrug resistant hepG2-R cancer cells when it was compared with free doxorubicin, with a cytoplasm accumulation profile. The results indicated that gold nanoparticles are a kind of promising drug delivery vehicle with good biocompatibility and suitable for further applications in drug delivery for improved chemotherapy, especially for overcoming multidrug resistance.

Upconversion nanoparticles conjugated with Gd(3+) -DOTA and RGD for targeted dual-modality imaging of brain tumor xenografts.

Glioblastoma multiforme (GBM) is the most common and malignant form of primary brain tumors in human. Small molecular magnetic resonance imaging (MRI) contrast agents are used for GBM diagnosis. However, conventional contrast agents have several limitations, such as low T1 relaxivity, short circulation half lives and absence of tumor targeting. Herein, we develop an upconversion nanoprobe labeled with Gd(3+) -DOTA and RGD (UCNP-Gd-RGD) for dual-modality imaging of glioblastoma. The preparation of UCNP-Gd-RGD starts with amine-functional upconversion nanoparticle core, followed by PEGylation, Gd(3+) DOTA conjugation and RGD labeling. The obtained UCNP-Gd-RGD has improved colloidal stability and reduced cytotoxicity compared with the UCNP core counterpart. Meanwhile, UCNP-Gd-RGD shows strong upconversion luminescence in deep-red region and three times enhancement of T1 relaxivity over Gd(3+) DOTA. Due to the recognition between UCNP-Gd-RGD and integrin αv ß3 receptors, the nanoprobe specifically binds to U87MG cells, as evidenced by confocal microscopy and quantified by ICP-MS. Furthermore, UCNP-Gd-RGD demonstrates a preferential retention in subcutaneous U87MG tumor xenograft as shown in both in vivo upconversion fluorescence/MR imaging studies and ex vivo analysis. UCNP-Gd-RGD, conjugated with numerous RGD peptide and T1 contrast enhancing molecules, is promising for MR imaging of glioblastoma and delineating the tumor boundary before surgery. In addition, NIR-to-red upconversion characteristic of UCNP-Gd-RGD facilitates its potential intra-operative use for fluorescence-guided tumor resection.

Nanotherapeutics in angiogenesis: synthesis and in vivo assessment of drug efficacy and biocompatibility in zebrafish embryos.

BACKGROUND: Carbon nanotubes have shown broad potential in biomedical applications, given their unique mechanical, optical, and chemical properties. In this pilot study, carbon nanotubes have been explored as multimodal drug delivery vectors that facilitate antiangiogenic therapy in zebrafish embryos. METHODS: Three different agents, ie, an antiangiogenic binding site (cyclic arginine-glycin-easpartic acid), an antiangiogenic drug (thalidomide), and a tracking dye (rhodamine), were conjugated onto single-walled carbon nanotubes (SWCNT). The biodistribution, efficacy, and biocompatibility of these triple functionalized SWCNT were tested in mammalian cells and validated in transparent zebrafish embryos. RESULTS: Accumulation of SWCNT-associated nanoconjugates in blastoderm cells facilitated drug delivery applications. Mammalian cell xenograft assays demonstrated that these antiangiogenic SWCNT nanoconjugates specifically inhibited ectopic angiogenesis in the engrafted zebrafish embryos. CONCLUSION: This study highlights the potential of using SWCNT for generating efficient nanotherapeutics.

Development and evaluation of pH-responsive single-walled carbon nanotube-doxorubicin complexes in cancer cells.

Single-walled carbon nanotubes (SWNTs) have been identified as an efficient drug carrier. Here a controlled drug-delivery system based on SWNTs coated with doxorubicin (DOX) through hydrazone bonds was developed, because the hydrazone bond is more sensitive to tumor microenvironments than other covalent linkers. The SWNTs were firstly stabilized with polyethylene glycol (H(2)N-PEG-NH(2)). Hydrazinobenzoic acid (HBA) was then covalently attached on SWNTs via carbodiimide-activated coupling reaction to form hydrazine-modified SWNTs. The anticancer drug DOX was conjugated to the HBA segments of SWNT using hydrazine as the linker. The resulting hydrazone bonds formed between the DOX molecules and the HBA segments of SWNTs are acid cleavable, thereby providing a strong pH-responsive drug release, which may facilitate effective DOX release near the acidic tumor microenvironment and thus reduce its overall systemic toxicity. The DOX-loaded SWNTs were efficiently taken up by HepG2 tumor cells, and DOX was released intracellularly, as revealed by MTT assay and confocal microscope observations. Compared with SWNT-DOX conjugate formed by supramolecular interaction, the SWNT-HBA-DOX featured high weight loading and prolonged release of DOX, and thus improved its cytotoxicity against cancer cells. This study suggests that while SWNTs have great potential as a drug carrier, the efficient formulation strategy requires further study.

Polymer-coated NaYF4:Yb³âº, Er³âº upconversion nanoparticles for charge-dependent cellular imaging.

Lanthanide-doped upconversion nanoparticles (UCNPs) are considered promising novel near-infrared (NIR) bioimaging agents with the characteristics of high contrast and high penetration depth. However, the interactions between charged UCNPs and mammalian cells have not been thoroughly studied, and the corresponding intracellular uptake pathways remain unclear. Herein, our research work involved the use of a hydrothermal method to synthesize polyvinylpyrrolidone-coated UCNPs (UCNP-PVP), and then a ligand exchange reaction was performed on UCNP-PVP, with the help of polyethylenimine (PEI) and poly(acrylic acid) (PAA), to generate UCNP-PEI and UCNP-PAA. These polymer-coated UCNPs demonstrated good dispersibility in aqueous medium, had the same elemental composition and crystal phase, shared similar TEM and dynamic light scattering (DLS) size distribution, and exhibited similar upconversion luminescence efficiency. However, the positively charged UCNP-PEI evinced greatly enhanced cellular uptake in comparison with its neutral or negative counterparts, as shown by multiphoton confocal microscopy and inductively coupled plasma mass spectrometry (ICP-MS) measurements. Meanwhile, we found that cationic UCNP-PEI can be effectively internalized mainly through the clathrin endocytic mechanism, as revealed by colocalization, chemical, and genetic inhibitor studies. This study elucidates the role of the surface polymer coatings in governing UCNP-cell interactions, and it is the first report on the endocytic mechanism of positively charged lanthanide-doped UCNPs. Furthermore, this study provides important guidance for the development of UCNPs as specific intracellular nanoprobes, allowing us to control the UCNP-cell interactions by tuning surface properties.

Nanostructure PtRu/MWNTs as anode catalysts prepared in a vacuum for direct methanol oxidation.

Platinum and ruthenium nanoparticles that are uniformly dispersed on multiwalled carbon nanotubes (MWNTs) were synthesized by vacuum pyrolysis using Pt(acac)2 and Ru(acac)3 as the metal precursors. The resulting nanocomposites were characterized by transmission electron microscopy and X-ray diffraction. The Pt, Pt45Ru55, and Ru nanoparticles had mean diameters of 3.0 +/- 0.6, 2.7 +/- 0.6, and 2.5 +/- 0.4 nm and the same mole number as their metal precursors at 500 degrees C. The electrocatalytic activity of the Pt/MWNTs and PtRu/MWNTs was investigated at room temperature by cyclic voltammetry and chronoamperometry. All of the electrochemical results showed that the PtRu/MWNTs exhibited a high level of catalytic activity for methanol oxidation as a result of the large surface area of the supporting carbon nanotubes and the wide dispersion of the Pt and Ru nanoparticles. Compared with the Pt/MWNTs, the onset potential for methanol oxidation of the PtRu/MWNTs was significantly lower, and the ratio of the forward anodic peak current to the reverse anodic peak current during methanol oxidation was somewhat higher. The Pt45Ru55/MWNTs displayed the best electrocatalytic activity of all of the carbon-nanotube-supported Pt and PtRu catalysts.