Xiaoyu Sun

Nanotoxicity of TiO2 nanoparticles to erythrocyte in vitro

Titanium dioxide (TiO(2)) has been considered as non-toxic mineral particles widely used in the fields like cosmetics, food and drug. When the scale come to nanometer, TiO(2) nanoparticles (nano-TiO(2)) exhibits multiple specific characteristics coupled with unknown risks on health. The purpose of this study was to systematically research the influence of nano-TiO(2) on erythrocyte. The results indicated that the erythrocytes treated with nano-TiO(2) underwent abnormal sedimentation, hemagglutination and dose dependent hemolysis, totally differing from those treated with micro-TiO(2). The ghost cells were firstly investigated by using ultra-thin cell section in the case under nano-TiO(2). The mechanism of such adverse effects is (1) the attachment around erythrocyte change the surface native properties and ultimately lead to hemoagglutination; (2) the content leak to the outside of erythrocyte through the breakage induced by both the nano-TiO(2) trans-membrane and the oxidative stress under nano-TiO(2). Our findings imply that nano-TiO(2) may have potential toxicity to human being health.

The in vitro and in vivo anti-tumor effect of layered double hydroxides nanoparticles as delivery for podophyllotoxin

In this research, we intercalated anti-tumor drug podophyllotoxin (PPT) into layered double hydroxides (LDHs) and investigated the in vitro cytotoxicity to tumor cells, the cellular uptake and in vivo anti-tumor inhibition of PPT-LDH. The nanohybrids were prepared by a two-step method with the size of 80-90nm and the zeta potential of 20.3mV. The in vitro cytotoxicity experiment indicated that PPT-LDH nanoparticles show better anti-tumor efficacy than PPT and are more readily taken up by Hela cells. PPT-LDH shows a long-term suppression effect on the tumor growth, and enhances the apoptotic process of tumor cells. The in vivo tests reveal that delivery of PPT via LDH nanoparticles is more efficient, but the mice toxicity of PPT in PPT-LDH hybrids is reduced in comparison with PPT alone. Pharmacokinetics study displays a prolonged circulation time and an increased bioavailability of PPT-LDH than PPT. These observations imply that LDH nanoparticles are the potential carrier of anti-tumor drugs in a range of new therapeutic applications.

The enhanced immune response of hepatitis B virus DNA vaccine using SiO2@LDH nanoparticles as an adjuvant.

Various approaches have been used to improve systemic immune response to infectious disease or virus, and DNA vaccination has been demonstrated to be one of these effective ways to elicit protective immunity against pathogens. Our previous studies showed that layered double hydroxides (LDH) nanoparticles could be efficiently taken up by the MDDCs and had an adjuvant activity for DC maturation. To further enhance the immune adjuvant activity of LDH, core-shell structure SiO2@LDH nanoparticles were synthesized with an average diameter of about 210 nm. And its high transfection efficiency in vitro was demonstrated by using GFP expression plasmid as model DNA. Exposing SiO2@LDH nanoparticles to macrophages caused a higher dose-dependent expression of IFN-γ, IL-6, CD86 and MHC II, compared with SiO2 and LDH respectively. Furthermore, in vivo immunization of BALB/c mice indicated that, DNA vaccine loaded-SiO2@LDH nanoparticles not only induced much higher serum antibody response than naked DNA vaccine and plain nanoparticles, but also obviously promoted T-cell proliferation and skewed T helper to Th1 polarization. Additionally, it was proved that the caveolae-mediated uptake of SiO2@LDH nanoparticles by macrophage lead to macrophages activation via NF-κB signaling pathway. Our results indicate that SiO2@LDH nanoparticles could serve as a potential non-viral gene delivery system.

Preparation, characterization, and anti-tumor property of podophyllotoxin-loaded solid lipid nanoparticles

In an effort to develop an alternative formulation of podophyllotoxin suitable for drug release and delivery, podophyllotoxin-loaded solid lipid nanoparticles (PPT-SLNs) were constructed, characterized and examined for in vitro cytotoxicity and tumor inhibition. The SLNs were prepared by using a solvent emulsification-evaporation method, and their size was around 50 nm. TEM detection showed that the SLNs were homogeneous and spherical in shape, and differential scanning calorimetry (DSC) measurement revealed a new conformation of PPT-SLNs. An in vitro drug release study showed that PPT was released from the SLNs in a slow but time-dependent manner. Furthermore, the treatment of 293T and HeLa cells with PPT-SLNs demonstrated that PPT-SLNs were less toxic to normal cells and more effective in anti-tumor potency compared with unconjugated PPT. A colony forming efficiency assay showed an effective long-term cancer growth suppression of PPT-SLNs; in addition, they can also enhance the apoptotic and cellular uptake processes on tumor cells compared with PPT. These results collectively demonstrated that this SLN formulation has a potential application as an alternative delivery system for anti-tumor drugs.

Enzyme activity inhibition and secondary structure disruption of nano-TiO2 on pepsin

In this study, the binding and enzyme activity inhibitory effect of nano-TiO(2) on pepsin was explored compared with micro-TiO(2). Nano-TiO(2) was about 60 nm and micro-TiO(2) was about 200 nm, both round in shape. The activity of pepsin was depressed significantly by nano-TiO(2) comparing to micro-ones. The results of UV spectrometry, HPLC, SDS-PAGE and CD assay proved that micro-TiO(2) has only physical absorption effect on pepsin, but no impairment on primary sequences or secondary structure. However, nano-TiO(2) had coordination interaction with pepsin besides physical binding effect. The secondary structure of pepsin was unfolded with the treatment of nano-TiO(2) at pH 6.5 and pH 3.53, which might consequently affect the beta-hairpin loop that protects the active center of pepsin, and then reduce the enzyme activity. Furthermore, the thermodynamic mechanisms of interaction between nano-TiO(2) and pepsin were explored by fluorescence spectrum and ITC analysis. According to the results of thermodynamic analysis, the K value was 3.64x10(6), stoichiometry (N(pepsin:nano-TiO2)) was 3.04x10(3), the total DeltaH was -2277 cal/mol, DeltaS was 22.7 cal/(K mol), therefore the nano-TiO(2)-pepsin interaction is spontaneous. The depression of activity and the unfolding of secondary structure of pepsin were resulted from non-covalent reactions, including electrostatic force and hydrophobic binding. This work studied the different inhibitory effects and revealed mechanisms of the interaction between micro/nano-TiO(2) and pepsin, and provided a useful approach for evaluating the health risk of nano-materials on level of proteins.

Intracellular uptake of etoposide-loaded solid lipid nanoparticles induces an enhancing inhibitory effect on gastric cancer through mitochondria-mediated apoptosis pathway

The objective of this study was to prepare and characterize etoposide (VP16)-loaded solid lipid nanoparticles (SLNs) and evaluate their antitumor activity in vitro. VP16-SLNs were prepared using emulsification and low-temperature solidification methods. The physicochemical properties of the VP16-SLNs were investigated by particle-size analysis, zeta potential measurement, drug loading, drug entrapment efficiency, stability, and in vitro drug-release behavior. In contrast to free VP16, the VP16-SLNs were well dispersed in aqueous medium, showing a narrow size distribution at 30–50 nm, a zeta potential value of −28.4 mV, high drug loading (36.91%), and an ideal drug entrapment efficiency (75.42%). The drug release of VP16-SLNs could last up to 60 hours and exhibited a sustained profile, which made it a promising vehicle for drug delivery. Furthermore, VP16-SLNs could significantly enhance in vitro cytotoxicity against SGC7901 cells compared to the free drug. Furthermore, VP16-SLNs could induce higher apoptotic rates, more significant cell cycle arrest effects, and greater cellular uptake in SGC7901 cells than free VP16. Moreover, results demonstrated that the mechanisms of VP16-SLNs were similar to those claimed for free VP16, including induction of cellular apoptosis by activation of p53, release of cytochrome c, loss of membrane potential, and activation of caspases. Thus, these results suggested that the SLNs might be a promising nanocarrier for VP16 to treat gastric carcinoma.

The examination of berberine excited state by laser flash photolysis

The property of the excited triplet state of berberine (BBR) was investigated by using time-resolved laser flash photolysis of 355 nm in acetonitrile. The transient absorption spectra of the excited triplet BBR were obtained in acetonitrile, which have an absorption maximum at 420 nm. And the ratio of excitation to ionization of BBR in acetonitrile solvent was calculated. The self-decay and self-quenching rate constants, and the absorption coefficient of (3)BBR* were investigated and the excited state quantum yield was determined. Furthermore utilizing the benzophenone (BEN) as a triplet sensitizer, and the beta-carotene (Car) as an excited energy transfer acceptor, the assignment of (3)BBR* was further confirmed and the related energy transfer rate constants were also determined.

Characterization of the transient species generated by the photoionization of Berberine: a laser flash photolysis study.

Using 266 nm laser flash photolysis it has been demonstrated that Berberine (BBR) in aqueous solution is ionized via a mono-photonic process giving a hydrated electron, anion radical that formed by hydrated electron react with steady state of BBR, and neutral radical that formed from rapid deprotonation of the radical cation of BBR. The quantum yield of photoionization is determined to be 0.03 at room temperature with KI solution used as a reference. Furthermore utilizing pH changing method and the SO(4.)(-) radical oxidation method, the assignment of radical cation of BBR was further confirmed, the pK(a) value of it was calculated, and the related set up rate constant was also determined.

Dexamethasone sodium phosphate intercalated layered double hydroxides and their therapeutic efficacy in a murine asthma model

Although inhaled steroids are the first choice to control asthma, frequent corticosteroid administration is associated with many side effects such as adrenocortical suppression, Cushings syndrome and osteoporosis. The purpose of this study was to develop a drug delivery system to overcome the limitation of corticosteroid administration and improve the therapeutic efficacy in an ovalbumin (OVA)-induced allergic asthma rat model. The intercalation of dexamethasone sodium phosphate (Dexa) into layered double hydroxides (LDHs) was achieved by the co-precipitation method and the obtained nanoparticles (Dexa–LDHs) have an average diameter of approximately 100 nm. The X-ray diffraction patterns and FT-IR spectra of the Dexa–LDHs indicated that the Dexa molecules were successfully intercalated into the LDHs via electrostatic interactions. 13C NMR chemical shifts were analysed to clarify the characteristic changes in functional groups after intercalation. Elemental C/H/N and inductively coupled plasma (ICP) analysis revealed the compositions of the nanohybrids. The thermal stability of Dexa anions was enhanced by holding together within the LDHs layers. The drug loading was estimated to be 50.8% and a gradual and biphasic in vitro release behavior of the drugs from LDHs in pH = 7.4 phosphate buffered saline (PBS) was observed. The parabolic diffusion model was used to simulate the release kinetics of Dexa from the LDHs. The potential of Dexa–LDHs as an anti-asthmatic agent was evaluated in the allergic asthma rat model. The results showed that Dexa–LDHs were more effective than Dexa to reduce the number of inflammatory cells in bronchoalveolar lavage (BAL) fluid. Furthermore, Dexa–LDHs significantly inhibited the increase of T-helper-2-type cytokines such as IL-4 and IL-13, and more effectively suppressed airway hyperresponsiveness. In conclusion, these results suggest that Dexa–LDHs could enhance the anti-asthmatic effect of Dexa in the treatment of allergic asthma rats. Our work indicated that LDHs could be a promising candidate for the exploration of new Dexa formulations.

Oxidative and Binding Effect of Nano-TiO2 on Plasmid DNA and Pepsin

With the development of nano material industry, more and more attention has been paid on the biological effect of nano materials. However, little research focused on the effect of nano TiO2 on protein level. In this study, we detected the toxic effect of nano TiO2 (50~60 nm) on DNA and functional proteinase. The oxidative damage of nano TiO2 on DNA was detected by gel electrophoresis and HPLC. Anson method was used to study the inhibition of nano TiO2 on pepsin, and the mechanism of the reaction was further researched by the method of UV-Vis scan and TEM. The results showed that the ratio of super-coiled DNA decreased significantly both under UV radiation and visible light. Levels of 8-OHdG generated from DNA increased from 27.66 8- OHdG/104 dG to 296.69 8-OHdG/104 dG after treated with nano TiO2. After water incubated with nano TiO2 at 37degC, the activity of pepsin decreased with the increase of the concentration of particels, UV-Vis scan and TEM detection proved the binding effect of nano TiO2 on pepsin, which indicated potential usage for oral drug delivery of nano TiO2.