Key processes in tumor metastasis and therapeutic strategies with nanocarriers: a review.

Cancer metastasis is the leading cause of cancer-related death. Metastasis occurs at all stages of tumor development, with unexplored changes occurring at the primary site and distant colonization sites. The growing understanding of the metastatic process of tumor cells has contributed to the emergence of better treatment options and strategies. This review summarizes a range of features related to tumor cell metastasis and nanobased drug delivery systems for inhibiting tumor metastasis. The mechanisms of tumor metastasis in the ideal order of metastatic progression were summarized. We focus on the prominent role of nanocarriers in the treatment of tumor metastasis, summarizing the latest applications of nanocarriers in combination with drugs to target important components and processes of tumor metastasis and providing ideas for more effective nanodrug delivery systems.

Functional characterization and comparison of lycopene epsilon-cyclase genes in Nicotiana tabacum.

BACKGROUND: Lycopene epsilon-cyclase (ε-LCY) is a key enzyme in the carotenoid biosynthetic pathway (CBP) of higher plants. In previous work, we cloned two Ntε-LCY genes from allotetraploid tobacco (Nicotiana tabacum), Ntε-LCY2 and Ntε-LCY1, and demonstrated the overall effect of Ntε-LCY genes on carotenoid biosynthesis and stress resistance. However, their genetic and functional characteristics require further research in polyploid plants. RESULTS: Here, we used CRISPR/Cas9 to obtain Ntε-LCY2 and Ntε-LCY1 mutants in allotetraploid N.tabacum K326. Ntε-LCY2 and Ntε-LCY1 had similar promoter cis-acting elements, including light-responsive elements. The Ntε-LCY genes were expressed in roots, stems, leaves, flowers, and young fruit, and their highest expression levels were found in leaves. Ntε-LCY2 and Ntε-LCY1 genes responded differently to normal light and high light stress. Both the Ntε-LCY2 and the Ntε-LCY1 mutants had a more rapid leaf growth rate, especially ntε-lcy2-1. The expression levels of CBP genes were increased in the ntε-lcy mutants, and their total carotenoid content was higher. Under both normal light and high light stress, the ntε-lcy mutants had higher photosynthetic capacities and heat dissipation levels than the wild type, and this was especially true of ntε-lcy2-1. The reactive oxygen species content was lower in leaves of the ntε-lcy mutants. CONCLUSION: In summary, the expression patterns and biological functions of the Ntε-LCY genes Ntε-LCY1 and Ntε-LCY2 differed in several respects. The mutation of Ntε-LCY2 was associated with a greater increase in the content of chlorophyll and various carotenoid components, and it enhanced the stress resistance of tobacco plants under high light.

Facile Synthesis of CoNi Bimetallic Nanoparticle Decorated Reduced Graphene Oxide as Efficient and Low-Cost Counter Electrode for Dye-Sensitized Solar Cells.

In this paper, CoNi bimetallic nanoparticle decorated reduced graphene oxide (CoNi-RGO) was synthesized by a facile hydrothermal method. When applied this CoNi-RGO into counter electrode for dye-sensitized solar cells (DSSCs), it shows smaller charge-transfer resistance and better electrocatalytic activity than that of pure reduced graphene oxide (RGO). At the optimized conditions, the energy conversion efficiency of DSSCs based on CoNi-RGO counter electrode was 3.79%, indicating a higher photovoltaic performance of DSSCs based on CoNi-RGO counter electrode than that of DSSCs based on RGO counter electrode (1.37%), and comparable to the value of DSSCs based on Pt counter electrode as a reference (4.95%). Additionally, the photovoltaic performance of DSSCs based on CoNi-RGO counter electrode strongly depends on its composition. The molar ratio of Co/Ni and the weight ratio of CoNi/GO that used to prepare CoNi-RGO counter electrode are key factors to affect the performance of their cell devices. When both the molar ratio of Co/Ni and the weight ratio of CoNi/GO are 1:1, the CoNi-RGO counter electrode shows the best performance, indicating the potential of such bimetallic nanoparticle decorated RGO as low-cost and efficient counter electrode to replace noble metal Pt counter electrode for the practical application of DSSCs devices.

Synthesis of an Efficient Counter Electrode Material for Dye-Sensitized Solar Cells by Pyrolysis of Melamine and Graphene Oxide.

An efficient counter electrode material for dye sensitized solar cells (DSSCs) was synthesized by pyrolysis of melamine and graphene oxide. The synthesized samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electrode microscopy, which show that nitrogen doped reduced graphene oxide (NRGO) was obtained by this synthesis method. In the synthesized NRGO, graphitic structure was kept and the nitrogen was existence as pyrrolic, pyridinic, graphitic, and oxidized nitrogen species in the samples. After deposited as counter electrode films for DSSCs, it shows lower charge-transfer resistance at the electrode/electrolyte interface and higher electrocatalytic activity towards reduction of triiodide (I-3) than that of reduced graphene oxide (RGO) prepared also by this method without adding melamine. Consequently, the DSSCs based on NRGO counter electrodes achieve an energy conversion efficiency of 4.60%, which is higher than that of RGO counter electrode (2.35%). Although the photovoltaic performance of NRGO counter electrode was lower than that of Pt counter electrode (5.70%), it is still a promising counter electrode to replace noble metal Pt due to its low cost and simple synthesis process.

Effect of Graphene/TiO2 Composite Layer on the Performance of Dye-Sensitized Solar Cells.

Graphene has attracted a lot of attention because of its unique mechanical, thermal, electrical and optical properties. In this study, a double layered structured photoanode consisting of a graphene/TiO2 composite layer and a TiO2 nanoparticles (P25) underlayer was developed. The photoelectric properties of as-prepared double layer structured photoanode were studied with comparison of the anatase TiO2 photoanode. Graphene was prepared by reduction of graphene oxide (GO) under a hydrothermal conditions and graphenen/TiO2 composite semiconductor materials were prepared by mixing graphene into TiO2 paste. The effect of graphene contents in graphene/TiO2 composite layer was also investigated. After constructing double layer photoanode with proper amount of graphene, the photoanode displayed enhanced light and dye adsorption properties with higher light harvesting efficiency, lower internal resistances, faster electron transport and lower charge recombination rate, which resulted in high current density. At the optimum conditions, the DSSC exhibited a Jsc of 15.01 mA cm-2, a Voc of 0.72 V, and a FF of 0.66 with the energy conversion efficiency (η) of 7.08%, indicating a increase in Jsc and η respectively than that of DSSC based on pure TiO2 photoanode, which gives a Jsc of 13.25 mA cm-2, a Voc of 0.73 V, and a FF of 0.62 with a η of 5.94%. However, the addition of excess graphene in the composite layer led to the enhancement of charge recombination, the reduction of dye adsorption and the decrease of photoelectric conversion efficiency of DSSCs. The graphene/TiO2 composite layer in DSSCs could really enhance its efficiency after the amount of graphene was successfully optimized.

Ethylenediamine-modified graphene oxide covalently functionalized with a tetracarboxylic Zn(ii) phthalocyanine hybrid for enhanced nonlinear optical properties.

Tetracarboxylic Zn(ii) phthalocyanine-amino functionalized graphene oxide (ZnPcC4-NGO) hybrid materials have been prepared by a covalent functionalization method. The characterizations indicate that the amino-functionalization of GO has an important influence on the structure and photophysical properties of the ZnPcC4-NGO hybrid. The ZnPcC4-NGO hybrid exhibits enhanced photo-induced electron transfer or energy transfer (PET/ET), compared to the ZnPcC4 covalent functionalized GO (ZnPcC4-GO), owing to the presence of the extended sp(2) carbon configurations, along with the partial reduction of the NGO nanosheets and the introduction of electron-donating ethylenediamine. The nonlinear optical (NLO) properties of the hybrids were investigated using the Z-scan technique at 532 nm with 4 ns laser pulses. The results show that the efficient covalent functionalization and partial reduction of NGO cause the ZnPcC4-NGO hybrid to possess evidently larger NLO properties than the individual NGO, ZnPcC4 and the ZnPcC4-GO hybrid. The enhanced NLO performance can be attributed to the increased excited state absorption from the extended sp(2) carbon configurations of the NGO moiety, reverse saturable absorption arising from ZnPcC4 moiety, and the contribution of the efficient PET/ET process between the ZnPcC4 and NGO moieties in the hybrid.

The effects of central metals on the photophysical and nonlinear optical properties of reduced graphene oxide-metal(II) phthalocyanine hybrids.

Reduced graphene oxide-metal(II) phthalocyanine (RGO-MPc, M = Cu, Zn and Pb) hybrid materials have been prepared by the covalent functionalization method. The resultant RGO-MPc hybrids are characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, ultraviolet-visible absorption and fluorescence spectroscopy. The RGO-MPc hybrids exhibit strong fluorescence quenching by means of the photo-induced electron transfer or the energy transfer (PET/ET) process between the RGO and MPc moieties. The PET/ET process particularly depends on the fluorescence quantum yield of MPc molecules with different central metals. The nonlinear optical (NLO) properties of the RGO-MPc hybrids are investigated by using the Z-scan technique at 532 nm with 4 ns laser pulses. The results show that the NLO properties of MPc molecules increase in the order of Zn < Pb < Cu, but the RGO-MPc hybrids exhibit NLO performance in the inverse sequence of Zn > Pb > Cu, implying that the NLO response arising from the efficient PET/ET process between RGO and MPc may play a more important role in the NLO properties of RGO-MPc hybrids than that originating from the MPc moiety.