The critical size of gold nanoparticles for overcoming P-gp mediated multidrug resistance.

Multidrug resistance (MDR) remains a huge obstacle during cancer treatment. One of the most studied MDR mechanisms is P-glycoprotein (P-gp) mediated drug efflux. Based on the three-dimensional structural characteristics of P-gp, gold nanoparticles (AuNPs) with average sizes of 4.1 nm and 5.4 nm were designed for the construction of nanodrug delivery systems (NanoDDSs), with the anticancer molecules 2-(9-anthracenylmethylene)-hydrazinecarbothioamide (ANS) and 6-mercaptopurine (6-MP) modified on the AuNP surfaces through the thiol group. In vitro cytotoxicity results suggested that the larger sized AuNPs can effectively decrease the drug resistance index of MCF-7/ADR cells to ∼2. Verapamil and P-gp antibody competitive experiments, combined with the cellular uptake of AuNPs, indicated that larger NanoDDSs were more conducive to intracellular drug accumulation and thus had improved anticancer activities, due to a size mismatch between the nanoparticles and the active site of P-gp, and, therefore, reduced drug efflux was seen. Measurements of ATPase activity and intracellular ATP levels indicated that the larger nanoparticles do not bind well to P-gp, thus avoiding effective recognition by P-gp. This was further evidenced by the observation that 4.1 nm and 5.4 nm NanoDDS-treated MCF-7/ADR cells showed remarkable differences in energy-related metabolic pathways. Therefore, the critical size of AuNPs for overcoming MDR was identified to be between 4.1 nm and 5.4 nm. This provides a more accurate description of the composite dimension requirements for NanoDDSs that are designed to overcome MDR.

Gold Nanorods Functionalized with Cathepsin B Targeting Peptide and Doxorubicin for Combinatorial Therapy against Multidrug Resistance.

Multidrug resistance (MDR) and adverse effects of chemotherapeutic agents are severe issues in clinical cancer treatment. Due to the dysregulation of enzymes in the cancer cells, enzyme-responsive drug delivery systems (DDSs) have been considered as a viable technology for cancer chemotherapy. In the present work, doxorubicin (DOX) is visible after leaving from AuNR-LAX. After treatment with AuNR-LAX, the drug resistance index of DOX-resistant MCF-7/ADR cells was reduced from extremely high 955.0 to 1.7, implying high potential of AuNR-LAX in the MDR phenotype cancer treatment. In addition, the cellular viability of both MCF-7 and MCF-7/ADR cells decreased from 50% to 80% after treatment with AuNR-LAX along (equivalent DOX concentration = 2.3 µg/mL, Au concentration = 30 µg/mL) to below 10% after AuNR-LAX treatment plus radiation of 808 nm, due to the NIR photothermal effect of AuNRs. Human bronchial epithelial cell line 16HBE was chosen to evaluate the adverse effect of AuNR-LAX on the normal cells. At the low concentration, the cytotoxicity of LAX and AuNR-LAX is comparable for breast cancer cell MCF-7 and normal cell 16HBE. It is noted that, at high concentration (with equivalent DOX concentration = 13.1 µg/mL, Au concentration = 167.7 µg/mL), the cellular viability of 16HBE cells is over 50%, whereas that of MCF-7 cancer cells is close to 0, implying the potential of AuNR-LAX in reducing the adverse effects of DOX against normal cells/tissues. Overall, AuNR-LAX showed high potential in overcoming MDR and alleviating adverse effect on normal cells.

Synthesis of a Novel Fluorescent Ruthenium Complex with an Appended Ac4GlcNAc Moiety by Click Reaction.

The O-linked ß-N-acetylglucosamine (O-GlcNAc) modification is an abundant post-translational modification in eukaryotic cells, which plays a fundamental role in the activity of many cells and is associated with pathologies like type II diabetes, Alzheimer's disease or some cancers. However, the precise connexion between O-GlcNAc-modified proteins and their function in cells is largely undefined for most cases. Confocal microscopy is a powerful and effective tool for in-cell elucidation of the function of biological molecules. Chemical labeling of non-ultraviolet or non-fluorescent carbohydrates with fluorescent tag is an essential step that makes intra-cellular microscopic inspection possible. Here we report a strategy based on the 1,3-dipolar cycloaddition, called click chemistry, between unnatural N-acetylglucosamine (GlcNAc) analogues Ac4GlcNAc (substituted with an azido group) and the corresponding fluorescent tag Ru(bpy)2(Phen-alkyne)Cl2 (4) to synthesize the fluorescent dye Ru(bpy)2(Phen-Ac4GlcNAc)Cl2 (5) under mild and neutral reaction conditions. Moreover, 5 showed good stability, desirable fluorescence characteristics, and exhibited rather low levels of cytotoxicity against sensitive MCF-7 cells. Additionally, we have achieved successful fluorescent imaging of 5 transported in living MCF-7 cells. Cell images displayed that proteins are potentially labelled with 5 in the cytoplasm.

Schiff base derived from thiosemicarbazone and anthracene showed high potential in overcoming multidrug resistance in vitro with low drug resistance index.

Multidrug resistance (MDR) is a huge obstacle in cancer chemotherapeutics. Overcoming MDR is a great challenge for anticancer drug discovery. Here, DNA binding and cytotoxicity of Schiff base L1 and L2 were explored to assess their efficiency in fighting cancer and overcoming the MDR. L1 and L2 could treat extremely chemoresistant MCF-7/ADR cell as drug-sensitive cell, with drug resistance index (DRI) <2.13, showing high potential in overcoming the MDR. The apoptotic ratio induced by L1 and L2 was low for both MCF-7 and MCF-7/ADR cells. L1 and L2 induced an impairment of cell cycle progression of MCF-7 and MCF-7/ADR cell lines and suppressed cell growth by perturbing progress through the G0/G1 phase, with L2 causing more profound effect, which might account for lower drug resistance after L2 treatment. The molecular docking revealed weak interaction between L1/L2 and P-glycoprotein (P-gp), the most important drug efflux pump and intracellular Rhodamine 123 accumulation indicated that the activity of P-gp was not inhibited by L1 and L2. Combined with the cellular uptake results, it implied that L1 and L2 could bypass P-gp efflux to exert anticancer activity.

TAT-Modified Gold Nanoparticle Carrier with Enhanced Anticancer Activity and Size Effect on Overcoming Multidrug Resistance.

Highly efficient targeted delivery is crucial for successful anticancer chemotherapy. In this study, we developed a drug delivery system ANS-TAT-AuNP that loads anticancer molecule 2-(9-anthracenylmethylene)-hydrazinecarbothioamide (ANS) via conjugation with cell-penetrating peptide TAT modified AuNPs. The in vitro study showed that the IC50 value of ANS-TAT-AuNPs3.8 nm reduced by 11.28- (24 h) and 12.64-fold (48 h) after incubation with liver hepatocellular carcinoma HepG2 cells compared to that of free ANS, suggesting that TAT modified AuNPs could enhance the antiproliferative activity of ANS. Also, ANS-TAT-AuNPs showed a size effect on overcoming multidrug resistance (MDR). The potential of ANS-TAT-AuNPs in overcoming MDR was assessed with MCF-7/ADR drug-resistant cell line, the drug resistance index (DRI) of which was extremely high (>190). The DRI of ANS-TAT-AuNPs22.1 nm decreased dramatically to 1.48 (24 h) and 2.20 (48 h), while that of ANS-TAT-AuNPs3.8 nm decreased to 7.64 (24 h) and 7.77 (48 h), indicating that ANS-TAT-AuNPs22.1 nm could treat extremely resistant MCF-7/ADR cancer cells as drug sensitive ones. The data suggest that the larger AuNPs had more profound effect on overcoming MDR, which could effectively prevent drug efflux due to their size being much larger than that of the p-glycoprotein channel (9-25 Å).

Evaluating p97 inhibitor analogues for their domain selectivity and potency against the p97-p47 complex.

We previously found that p97 ATPase inhibitors 2-(2-amino-1H-benzo[d]imidazol-1-yl)-N-benzyl-8-methoxyquinazolin-4-amine (ML240) and 2-(2H-benzo[b][1,4]oxazin-4(3H)-yl)-N-benzyl-5,6,7,8-tetrahydroquinazolin-4-amine (ML241) specifically target the D2 domain of wild-type p97. In addition, one of the major p97 cofactors, p47, decreases their potencies by ∼50-fold. In contrast, N(2) ,N(4) -dibenzylquinazoline-2,4-diamine (DBeQ) targets both the D1 and D2 domains and shows only a four- to sixfold decrease in potency against the p97-p47 complex. To elucidate structure-activity relationships for the inhibitors, we screened 200 p97 inhibitor analogues for their ability to inhibit the ATPase activity of either or both of the D1 or D2 domains, as well for their effects on p47 potency. The selectivity of 29 of these compounds was further examined by eight-dose titrations. Four compounds showed modest selectivity for inhibiting the ATPase activity of D1. Eleven compounds inhibited D2 with greater potencies, and four showed similar potencies against D1 and D2. p47 decreased the potencies of the majority of the compounds and increased the potencies of five compounds. These results highlight the possibility of developing domain-selective and complex-specific p97 inhibitors in order to further elucidate the physiological roles of p97 and its cofactors.

The intracellular controlled release from bioresponsive mesoporous silica with folate as both targeting and capping agent.

A smart mesoporous silica nanocarrier with intracellular controlled release is fabricated, with folic acid as dual-functional targeting and capping agent. The folate not only improves the efficiency of the nanocarrier internalized by the cancer cells, but also blocks the pores of the mesoporous silica to eliminate premature leakage of the drug. With disulfide bonds as linkers to attach the dual-functional folate within the surface of mesoporous silica, the controlled release can be triggered in the presence of reductant dithiothreitol (DTT) or glutathione (GSH). The cellular internalization via folate-receptor-mediated endocytosis and the intracellular controlled release of highly toxic anticancer drug DOX were demonstrated with an in vitro HeLa cell culture, indicating an efficient cancer-targeted drug delivery.

Spectroscopic and theoretical studies on nickel(II) complex of maleonitriledithiolate and 2,2'-bipyridine.

The complete IR spectra of the title complex Ni(mnt)(bpy) (mnt=maleonitriledithiolate, bpy=2,2'-bipyridine) and a new method to analyze vibrational spectra for such a complicated metal complex are reported in this paper. The molecular geometry, binding, electronic structure and spectroscopic property of it have been studied in detail by theoretical calculations. The geometry optimization from PM3 calculations give that this molecule is of a planar structure with the symmetry point group C(2v) and its ground state is the spin triplet state. The vibrational and electronic spectra were calculated by PM3 and ZINDO/S methods, respectively. The scientific method of analyzing vibrational spectra is established herein by giving main fixed points and pivotal vibrational units. Besides the regular symbols, the new defined symbols eta and M play an important role in describing the vibration modes accurately and vividly.