Rongrong Zhu

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 use of layered double hydroxides as DNA vaccine delivery vector for enhancement of anti-melanoma immune response.

Our previous studies have shown that Mg:Al 1:1 layered double hydroxides (LDH(R1)) nanoparticles could be taken up by the MDDCs effectively and had an adjuvant activity for DC maturation. Furthermore, these LDH(R1) nanoparticles could up-regulate the expression of CCR7 and augment the migration of DCs in response to CCL21. In current study, we have evaluated whether LDH(R1) as DNA vaccine delivery carrier can augment the efficacy of DNA vaccine immunization in vivo. Firstly, we found that LDH(R1) was efficient in combining DNA and formed LDH(R1)/DNA complex with an average diameter of about 80-120 nm. Its high transfection efficiency in vivo delivered with a GFP expression plasmid was also observed. After delivery of pcDNA(3)-OVA/LDH(R1) complex by intradermal immunization in C57BL/6 mice, the LDH(R1) induced an enhanced serum antibody response much greater than naked DNA vaccine. Using B16-OVA melanoma as tumor model, we demonstrated that pcDNA(3)-OVA/LDH(R1) complex enhanced immune priming and protection from tumor challenge in vivo. Furthermore, we showed that LDH(R1) induced dramatically more effective CTL activation and skewed T helper polarization to Th1. Collectively, these findings demonstrate that this LDH(R1)/DNA plasmid complex should be a new and promising way in vaccination against tumor.

Enhanced bioavailability and efficiency of curcumin for the treatment of asthma by its formulation in solid lipid nanoparticles.

Curcumin has shown considerable pharmacological activity, including anti-inflammatory, but its poor bioavailability and rapid metabolization have limited its application. The purpose of the present study was to formulate curcumin-solid lipid nanoparticles (curcumin-SLNs) to improve its therapeutic efficacy in an ovalbumin (OVA)-induced allergic rat model of asthma. A solvent injection method was used to prepare the curcumin-SLNs. Physiochemical properties of curcumin-SLNs were characterized, and release experiments were performed in vitro. The pharmacokinetics in tissue distribution was studied in mice, and the therapeutic effect of the formulation was evaluated in the model. The prepared formulation showed an average size of 190 nm with a zeta potential value of −20.7 mV and 75% drug entrapment efficiency. X-ray diffraction analysis revealed the amorphous nature of the encapsulated curcumin. The release profile of curcumin-SLNs was an initial burst followed by sustained release. The curcumin concentrations in plasma suspension were significantly higher than those obtained with curcumin alone. Following administration of the curcumin-SLNs, all the tissue concentrations of curcumin increased, especially in lung and liver. In the animal model of asthma, curcumin-SLNs effectively suppressed airway hyperresponsiveness and inflammatory cell infiltration and also significantly inhibited the expression of T-helper-2-type cytokines, such as interleukin-4 and interleukin-13, in bronchoalveolar lavage fluid compared to the asthma group and curcumin-treated group. These observations implied that curcumin-SLNs could be a promising candidate for asthma therapy.

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.

pH-sensitive strontium carbonate nanoparticles as new anticancer vehicles for controlled etoposide release

Strontium carbonate nanoparticles (SCNs), a novel biodegradable nanosystem for the pH-sensitive release of anticancer drugs, were developed via a facile mixed solvent method aimed at creating smart drug delivery in acidic conditions, particularly in tumor environments. Structural characterization of SCNs revealed that the engineered nanocarriers were uniform in size and presented a dumbbell-shaped morphology with a dense mass of a scale-like spine coating, which could serve as the storage structure for hydrophobic drugs. Chosen as a model anticancer agent, etoposide was effectively loaded into SCNs based on a simultaneous process that allowed for the formation of the nanocarriers and for drug storage to be accomplished in a single step. The etoposide-loaded SCNs (ESCNs) possess both a high loading capacity and efficient encapsulation. It was found that the cumulative release of etoposide from ESCNs is acid-dependent, and that the release rate is slow at a pH of 7.4; this rate increases significantly at low pH levels (5.8, 3.0). Meanwhile, it was also found that the blank SCNs were almost nontoxic to normal cells, and ESCN systems were evidently more potent in antitumor activity compared with free etoposide, as confirmed by a cytotoxicity test using an MTT assay and an apoptosis test with fluorescence-activated cell sorter (FACS) analysis. These findings suggest that SCNs hold tremendous promise in the areas of controlled drug delivery and targeted cancer therapy.

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.

Signalling pathways involved in the activation of dendritic cells by layered double hydroxide nanoparticles

Layered double hydroxide (LDH) nanoparticles are attractive as potential drug vectors for the targeting not only of tissues, but also of intracellular organelles, and particularly the acidic endolysosomes created after cell endocytosis. The purpose of this study was to investigate the ability of LDH nanoparticles designed as vectors to activate dendritic cells (DCs), as measured by various cellular functions. The study also explored the possible signaling pathway through which the LDH nanoparticles exerted their effects on the cellular functions of DCs. First, LDH nanoparticles with different ratios of Mg(OH)(2) to Al(OH)(3) (1:1, 2:1 and 3:1, called R1, R2 and R3 respectively) were optimized and had a hydrodynamic diameter of 57 nm with a zeta potential of +35 mV. Then, the efficient endocytosis of the optimized LDH nanoparticles by bone marrow-derived dendritic cells (MDDCs) was monitored by fluorescence-activated cell sorting. The effect of R1, R2 and R3 on the expression of the pro- and anti-inflammatory cytokines (TNF-alpha, IL-6, and IL-12) and the co-stimulatory molecules (CD40, CD80, CD86, and MHC class II) in MDDCs was examined. The exposure of R1 caused a dose-dependent increase in the expression of TNF-alpha, IL-12, CD86 and CD40, while R2 and R3 did not up-regulate these cytokines and co-stimulatory molecules. Migration assays showed that R1 could increase the migration capacity of DCs to CCL21 and up-regulate the expression of CCR7. Furthermore, we found that R1 significantly increased the NF-kappaB expression in the nucleus (in a dose-dependent manner) and promoted the degradation of total IkappaBalpha levels, indicating that the NF-kappaB signaling pathway might involve in an R1-induced DC activation. Our results suggested that LDH nanoparticles, in the future, may function as a useful vector for ex vivo engineering to promote vaccine delivery in immune cells.

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.

The in vitro sustained release profile and antitumor effect of etoposide-layered double hydroxide nanohybrids

Magnesium-aluminum layered double hydroxides intercalated with antitumor drug etoposide (VP16) were prepared for the first time using a two-step procedure. The X-ray powder diffraction data suggested the intercalation of VP16 into layers with the increased basal spacing from 0.84–1.18 nm was successful. Then, it was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, and transmission electron microscopy. The prepared nanoparticles, VP16-LDH, showed an average diameter of 62.5 nm with a zeta potential of 20.5 mV. Evaluation of the buffering effect of VP16-LDH indicated that the nanohybrids were ideal for administration of the drugs that treat human stomach irritation. The loading amount of intercalated VP16 was 21.94% and possessed a profile of sustained release. The mechanism of VP16-LDH release in the phosphate buffered saline solution at pH 7.4 is likely controlled by the diffusion of VP16 anions from inside to the surface of LDH particles. The in vitro cytotoxicity and antitumor assays indicated that VP16-LDH hybrids were less toxic to GES-1 cells while exhibiting better antitumor efficacy on MKN45 and SGC-7901 cells. These results imply that VP16-LDH is a potential antitumor drug for a broad range of gastric cancer therapeutic applications.