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.

Two-photon plasma membrane imaging in live cells by an amphiphilic, water-soluble cyctometalated platinum(II) complex.

An amphiphilic, water-soluble cyclometalated Pt(II) complex with two-photon emission properties has been developed as a molecular marker specific for in vitro plasma membrane staining.

A bioaccumulative cyclometalated platinum(II) complex with two-photon-induced emission for live cell imaging.

The cyclometalated platinum(II) complex [Pt(L)Cl], where HL is a new cyclometalating ligand 2-phenyl-6-(1H-pyrazol-3-yl)pyridine containing C(phenyl), N(pyridyl), and N(pyrazolyl) donor moieties, was found to possess two-photon-induced luminescent properties. The two-photon-absorption cross section of the complex in N,N-dimethylformamide at room temperature was measured to be 20.8 GM. Upon two-photon excitation at 730 nm from a Ti:sapphire laser, bright-green emission was observed. Besides its two-photon-induced luminescent properties, [Pt(L)Cl] was able to be rapidly accumulated in live HeLa and NIH3T3 cells. The two-photon-induced luminescence of the complex was retained after live cell internalization and can be observed by two-photon confocal microscopy. Its bioaccumulation properties enabled time-lapse imaging of the internalization process of the dye into living cells. Cytotoxicity of [Pt(L)Cl] to both tested cell lines was low, according to MTT assays, even at loadings as high as 20 times the dose concentration for imaging for 6 h.

Ginsenoside Rg1 activates ligand-independent estrogenic effects via rapid estrogen receptor signaling pathway.

BACKGROUND: Ginsenoside Rg1 was shown to exert ligand-independent activation of estrogen receptor (ER) via mitogen-activated protein kinase-mediated pathway. Our study aimed to delineate the mechanisms by which Rg1 activates the rapid ER signaling pathways. METHODS: ER-positive human breast cancer MCF-7 cells and ER-negative human embryonic kidney HEK293 cells were treated with Rg1 (10-12M, 10-8M), 17ß-estradiol (10-8M), or vehicle. Immunoprecipitation was conducted to investigate the interactions between signaling protein and ER in MCF-7 cells. To determine the roles of these signaling proteins in the actions of Rg1, small interfering RNA or their inhibitors were applied. RESULTS: Rg1 rapidly induced ERα translocation to plasma membrane via caveolin-1 and the formation of signaling complex involving linker protein (Shc), insulin-like growth factor-I receptor, modulator of nongenomic activity of ER (MNAR), ERα, and cellular nonreceptor tyrosine kinase (c-Src) in MCF-7 cells. The induction of extracellular signal-regulated protein kinase and mitogen-activated protein kinase kinase (MEK) phosphorylation in MCF-7 cells by Rg1 was suppressed by cotreatment with small interfering RNA against these signaling proteins. The stimulatory effects of Rg1 on MEK phosphorylation in these cells were suppressed by both PP2 (Src kinase inhibitor) and AG1478 [epidermal growth factor receptor (EGFR) inhibitor]. In addition, Rg1-induced estrogenic activities, EGFR and MEK phosphorylation in MCF-7 cells were abolished by cotreatment with G15 (G protein-coupled estrogen receptor-1 antagonist). The increase in intracellular cyclic AMP accumulation, but not Ca mobilization, in MCF-7 cells by Rg1 could be abolished by G15. CONCLUSION: Ginsenoside Rg1 exerted estrogenic actions by rapidly inducing the formation of ER containing signalosome in MCF-7 cells. Additionally, Rg1 could activate EGFR and c-Src ER-independently and exert estrogenic effects via rapid activation of membrane-associated ER and G protein-coupled estrogen receptor.

Emissive terbium probe for multiphoton in vitro cell imaging.

A polymeric terbium complex that can be excited by near-infrared excitation at 800 nm via multiphoton absorption processes has been synthesized. This complex has been demonstrated to show strong, observable, three-photon-induced f-f emission in cell imaging. In vitro studies carried out in three carcinoma cell lines (A549, HONE1, and HeLa) have been performed and shown to have low cytotoxicity. This complex is therefore a potential candidate for future infrared excitation imaging dyes.

Differential ERα-mediated rapid estrogenic actions of ginsenoside Rg1 and estren in human breast cancer MCF-7 cells.

Recent studies indicated that both estren and Rg1 appear to be able to activate mitogen-activated protein kinase (MAPK) pathway in estrogen responsive cells. Rg1 could lead to MAPK activation through ligand-independent activation of estrogen receptor (ER), while estren could activate the Src-MAPK pathway in an ERE-independent manner. Thus, it is important to understand the mechanistic insights on the difference in transcriptional activation between estren and Rg1. The present study also addressed the differential abilities of Rg1 and estren in terms of the ability to activate ER and the ability to induce ER translocation in MCF-7 cells. Our data indicated that Rg1 could increase pS2 gene expression, and could recruit the co-activator steroid receptor co-activator-1 (SRC-1) to the pS2 promoter. Rg1 could also induce ERα nuclear translocation as well as ERα phosphorylation at Ser118 principally in the cytoplasm in MCF-7 cells. We deduced that estren induced ERE-dependent transcriptional activity and activated ERα at Ser118 occurred in the nucleus of MCF-7 cells. However, it was found to decrease pS2 gene expression and failed to induce the recruitment of SRC-1 to the pS2 promoter in MCF-7 cells. Our results suggest that the abilities of Rg1 and estren to regulate pS2 gene expression, to recruit co-activators as well as to induce sub-cellular distribution of ERα are dramatically different.

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.

A two-photon europium complex as specific endoplasmic reticulum probe.

Highly emissive europium complexes with specific endoplasmic reticulum localization potential includes several advantages such as fast uptake, long resident lifetime, low dosage requirement, low cytotoxicity and highly emissive two-photon induced f-f emission imaging.