Bochu Wang

DNA binding, cytotoxicity, apoptotic inducing activity, and molecular modeling study of quercetin zinc(II) complex

DNA cleavage activity of quercetin zinc(II) complex has been studied, but little attention has been devoted to the relationship between antitumor activity of this complex and DNA-binding properties. DNA-binding properties of quercetin zinc(II) complex were studied using UV-vis spectra, fluorescence measurements, and viscosity measurements. The results obtained indicate that quercetin zinc(II) complex can intercalate into the stacked base pairs of DNA, and compete with the strong intercalator ethidium bromide for the intercalative binding sites with Stern-Volmer quenching constant, K(sq)=1.24. The complex was subjected to biological tests in vitro using three tumor cell lines (HepG2, SMMC7721, and A549), which showed significant cytotoxicity against three tumor cell lines. Moreover, Hoechst33258 staining showed HepG2 cells underwent the typical morphologic changes of apoptosis characterized by nuclear shrinkage, chromatin condensation, or fragmentation after exposure to the complex. In addition, Molecular modeling was performed to learn the complex could be preferentially bound to DNA in GC region. Our results suggest that antitumor activity of quercetin zinc(II) complex might be related to its intercalation into DNA.

DNA binding and oxidative DNA damage induced by a quercetin copper(II) complex: potential mechanism of its antitumor properties.

The interaction of a quercetin copper(II) complex with DNA was investigated using UV–vis spectra, fluorescence measurement, viscosity measurement, agarose gel electrophoresis, and thiobarbituric acid reactive substances assay. The results indicate that the quercetin copper(II) complex can promote the cleavage of plasmid DNA, producing single and double DNA strand breaks, and intercalate into the stacked base pairs of DNA. Moreover, the complex can induce oxidative DNA damage involving generation of reactive oxygen species such as H2O2 and Cu(I)OOH. In addition, the cytotoxicity experiments carried out with A549 cells confirmed its apoptosis-inducing activity. And we also demonstrate that the levels of survivin protein expression in A549 cells decreased, and that relative activity of caspase-3 increased significantly after treatment with the complex. So our results suggest that the antitumor mechanism of the quercetin copper(II) complex involves not only its oxidative DNA damage with generation of reactive oxygen species but also its specific interaction with DNA.

Electrospun nanofiber meshes with tailored architectures and patterns as potential tissue-engineering scaffolds

Using a stainless steel mesh as a template collector, electrospun nanofiber meshes with well-tailored architectures and patterns were successfully prepared from biodegradable poly (epsilon-caprolactone) (PCL). It was found that the resulting PCL nanofiber (NF) meshes had similar topological structures to that of the template stainless steel mesh. Such PCL nanofiber meshes (NF meshes) had improved the tensile strength with Youngs modulus of 62.7 +/- 5.3 MPa, which is >40% higher than the modulus of 44 +/- 5.7 MPa as measured with the corresponding randomly oriented PCL nanofiber mats (RNF mat). On the other hand, the ultimate strain (87.30%) of the PCL NF meshes was distinctly lower than that of the PCL RNF mats (146.46%). To the best of our knowledge, this is the first time that the mechanical properties of nanofiber meshes with tailored architectures and patterns were studied and reported. When cultured with a mouse osteoblastic cell line (MC3T3-E1), the electrospun PCL NF meshes gave a much higher proliferation rate as compared with the randomly oriented PCL RNF mats. More importantly, it was found that the cells grew and elongated along the fiber orientation directions, and the resulted cellular organization and distribution mimicked the topological structures of the PCL NF meshes. These results indicated that the electrospun nanofiber scaffolds with tailored architectures and patterns hold potential for engineering functional tissues or organs, where an ordered cellular organization is essential.

The screening toolbox of bioactive substances from natural products: a review.

Hunting lead compounds from natural products plays a vital role in finding successful drug candidates. The efficiency of screening campaigns is mainly determined by the validity of selected screening models. To screen desired lead compounds, researchers have developed a plethora of experimental screening models. However, the considerable diversity of screening models from animal models, tissue models, to cell models and so on, may cause some trouble in choosing the suitable one. This review provides a toolbox of experimental screening models that have been used to discover new drug candidates from natural products. Two screening indexes are designed for different research directions in this screening toolbox. Index I is proposed from the direction of screening different objective substance populations, including plant extracts, active fractions and pure compounds; index Π is according to screening different drug properties, including pharmacological properties, pharmacokinetic properties and affinity binding properties. We hope that the abbreviated bibliographies will help readers to quickly retrieve useful information by two screening indexes and provide certain reference value for choosing more appropriate screening models. Finally, we discuss ways of improving model systems, as well as future directions.

Influence of ultrasonic stimulation on the growth and proliferation of Oryza sativa Nipponbare callus cells

Ultrasound acts as an alternative stress on cells or tissues. In this study it is aimed to investigate the effect of ultrasonic stimulation on the growth and proliferation of Oryza sativa Nipponbare cells (rice callus) in suspension culture. After the samples were stimulated by ultrasound at 28 kHz, we measured their growth and proliferation by using a colorimetric MTT ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay as well as fresh weights of the cells. Growth curves were obtained by fresh weights in the suspension culture after ultrasonic agitation for different time from 2 to 120 s. In MTT method, the optical density was determined at 570 nm in the cell suspension on 10 days after the ultrasonic agitation. Up to 5 s agitation OD570 increased; it decreased for more prolonged stimulation. We found that ultrasonic stimulation could promote the growth and proliferation of O. sativa Nipponbare cells in suspension culture with the optimal stimulation of 5 s, while with longer agitation, its growth and proliferation was inhibited. The mechanism may be that the ultrasound activated or destroyed the cellular structure, such as cell membrane, cytoskeleton and mitochondria in which many enzymes and ion channels are affected. In addition, the enhancement of cell wall and cell membrane fluidity might be one of the factors to promote the cell growth in 5-s ultrasonic stimulation.

Effects of ultrasound on the growth and vacuolar H+-ATPase activity of aloe arborescens callus cells

Abstract Effects of ultrasound on the growth and vacuolar H+-ATPase (V-ATPase) activity of aloe arborescens callus cells were investigated. The callus cells cultured in suspension were agitated by an ultrasonic bath at 28 kHz from the exposure time ts=2–60 s, and the cell growth was the highest at ts=5 s as measured by the fresh weight of the callus. The callus cells cultured in solid were exposed by a digital sonifier at 20 kHz in 2 s

Preparation of Eudragit L 100-55 enteric nanoparticles by a novel emulsion diffusion method.

In this study, a novel emulsion diffusion method was used to prepare enteric Eudragit L100-55 nanoparticles by ultrasonic dispersion and diffusion solidification. Omeprazole was selected as the model drug. The prepared nanoparticles were in spherical shape and exhibited negative zeta potential. The Fourier transform infrared spectroscopy results indicated that no molecular interaction occurred between the drug molecule and polymer chain. In addition, the nanoparticles showed a strong pH-sensitive release in vitro. A mild cytotoxicity of nanoparticle was observed in the subsequent studies, and the particle cellular uptake study showed that the nanoparticles could be taken up by Caco-2 cells after 0.5h incubation. Our results indicated that the enteric Eudragit L 100-55 nanoparticle could be synthesized successfully via this ultrasonic solidification method, which also could be applied to prepare other pH-sensitive polymer nanoparticles.

Simultaneous determination of nine flavonoids in Polygonum hydropiper L. samples using nanomagnetic powder three-phase hollow fibre-based liquid-phase microextraction combined with ultrahigh performance liquid chromatography–mass spectrometry

A simple, inexpensive, and efficient nanomagnetic powder three-phase hollow fibre-based liquid-phase microextraction (HF-LPME) technique combined with ultrahigh performance liquid chromatography-mass spectrometry (UPLC-MS) was developed for the simultaneous analysis of nine flavonoids in Polygonum hydropiper L. samples. The final, optimised extraction conditions were as follows: an organic solvent of ethyl acetate, a donor phase of aqueous KH₂PO₄ at pH 3.0, an acceptor phase of aqueous NaHCO₃ at pH 8.5, a stirring rate of 1000 rpm, and an extraction time of 50 min. Under these conditions, analyte calibration curves were all linear, with correlation coefficients ≥ 0.9994. The relative standard deviation for all analytes in intra-day (0.8-2.2%) and inter-day (1.7-3.5%) precision tests was well within the acceptable ranges, as were the limits of quantitation (LOQ < 0.054 μg/L) and detection (LOD < 0.170 μg/L). Recoveries for all standard compounds were between 95.17% and 99.82%, with a RSD of no more than 2.3%. Correlative analyses demonstrated that the physicochemical parameters of the compounds themselves also influenced the extraction efficiency. This technology proved to be rapid, sensitive, and reliable for the quality control of P. hydropiper L. samples.

Regulation of survivin and Bcl-2 in HepG2 cell apoptosis induced by quercetin.

Quercetin, a widely distributed bioflavonoid, has been shown to induce growth inhibition in a variety of human cancer cells. However, the regulation of survivin and Bcl‐2 on the quercetin‐induced cell‐growth inhibition and apoptosis in cancer cells remains unclear. In the present study, we report that quercetin can inhibit proliferation and induce apoptosis in HepG2 cells in dose‐ and time‐dependent manner. Hoechst 33258 and acridine orange/ethidium bromide (AO/EB) staining showed that HepG2 cells underwent the typical morphologic changes of apoptosis characterized by nuclear shrinkage, chromatin condensation, or fragmentation after exposure to quercetin. Cell‐cycle analysis reveals a significant increase of the proportion of cells in G0/G1 phase. We also demonstrate that the levels of survivin and Bcl‐2 protein expression in HepG2 cells decreased concurrently, and the levels of p53 protein increased significantly after treatment with quercetin by immunocytochemistry analysis. Relative activity of caspase‐3 and caspase‐9 increased significantly. These data clearly indicate that quercetin‐induced apoptosis is associated with caspase activation, and the levels of survivin and Bcl‐2. Our results indicate that the expression of survivin may be associated with Bcl‐2 expression, and the inhibition expression of survivin, in conjunction with Bcl‐2, might cause more pronounced apoptotic effects. Together, concurrent down‐regulated survivin and Bcl‐2 play an important role in HepG2 cell apoptosis induced by quercetin.

Cancer therapy based on nanomaterials and nanocarrier systems

Targeted delivery of drug molecules to tumor tissue is one of the most interesting and challenging endeavors faced in pharmaceutical field, due to the critical and pharmacokinetically specific environment that exists in tumor. Over these years, cancer targeting treatment has been greatly improved by new tools and approaches based on nanotechnology. The review firstly introduces the specific physical and chemical properties of a serial of nanomaterials, such as nanoparticles, micelles, dendrimers, carbon nanotubes, quantum dots, and nanofibers. It then places great emphasis on their application in the field of cancer therapy when they are used as nanocarrier systems. Based on the current status, the paper further discusses the unsolved problems and makes a perspective for the future prospects of the nanocarrier systems.