Guoqiang Zhou

Time-dependent translocation and potential impairment on central nervous system by intranasally instilled TiO2 nanoparticles

Nanoparticles can be administered via nasal, oral, intraocular, intratracheal (pulmonary toxicity), tail vein and other routes. Here, we focus on the time-dependent translocation and potential damage of TiO(2) nanoparticles on central nervous system (CNS) through intranasal instillation. Size and structural properties are important to assess biological effects of TiO(2) nanoparticles. In present study, female mice were intranasally instilled with two types of well-characterized TiO(2) nanoparticles (i.e. 80 nm, rutile and 155 nm, anatase; purity>99%) every other day. Pure water instilled mice were served as controls. The brain tissues were collected and evaluated for accumulation and distribution of TiO(2), histopathology, oxidative stress, and inflammatory markers at post-instillation time points of 2, 10, 20 and 30 days. The titanium contents in the sub-brain regions including olfactory bulb, cerebral cortex, hippocampus, and cerebellum were determined by inductively coupled plasma mass spectrometry (ICP-MS). Results indicated that the instilled TiO(2) directly entered the brain through olfactory bulb in the whole exposure period, especially deposited in the hippocampus region. After exposure for 30 days, the pathological changes were observed in the hippocampus and olfactory bulb using Nissl staining and transmission electron microscope. The oxidative damage expressed as lipid peroxidation increased significantly, in particular in the exposed group of anatase TiO(2) particles at 30 days postexposure. Exposure to anatase TiO(2) particles also produced higher inflammation responses, in association with the significantly increased tumor necrosis factor alpha (TNF-alpha) and interleukin (IL-1 beta) levels. We conclude that subtle differences in responses to anatase TiO(2) particles versus the rutile ones could be related to crystal structure. Thus, based on these results, rutile ultrafine-TiO(2) particles are expected to have a little lower risk potential for producing adverse effects on central nervous system. Although understanding the mechanisms requires further investigation, the present results suggest that we should pay attention to potential risk of occupational exposure for large-scaled production of TiO(2) nanoparticles.

Potential neurological lesion after nasal instillation of TiO2 nanoparticles in the anatase and rutile crystal phases

Nanoscale titanium dioxide (TiO(2)) is massively produced and widely used in living environment, which hence make the potential risk to human health. Central nervous system (CNS) is the potential susceptible target of inhaled nanoparticles, but the studies on this aspect are limited so far. We report the accumulation and toxicity results in vivo of two crystalline phases of TiO(2) nanoparticles (80nm, rutile and 155nm, anatase; purity >99%). The female mice were intranasally instilled with 500microg of TiO(2) nanoparticles suspension every other day for 30 days. Synchrotron radiation X-ray fluorescence analysis (SRXRF) and inductively coupled plasma mass spectrometry (ICP-MS) were used to determine the contents of titanium in murine brain. Then, the pathological examination of brain tissue, oxidative stress-mediated responses, and levels of neurochemicals in the brain of exposed mice were also analyzed. The obvious morphological changes of hippocampal neurons and increased GFAP-positive astrocytes in the CA4 region were observed, which were in good agreements with higher Ti contents in the hippocampus region. Oxidative stress occurred obviously in whole brain of exposed mice such as lipid peroxidation, protein oxidation and increased activities of catalase, as well as the excessive release of glutamic acid and nitric oxide. These findings indicate anatase TiO(2) nanoparticles exhibited higher concern on some tested biological effects. To summarize, results provided the preliminary evidence that nasal instilled TiO(2) nanoparticles could be translocated into the central nervous system and cause potential lesion of brain, and the hippocampus would be the main target within brain.

Molecular mechanism of pancreatic tumor metastasis inhibition by Gd@C82(OH)22 and its implication for de novo design of nanomedicine

Pancreatic adenocarcinoma is the most lethal of the solid tumors and the fourth-leading cause of cancer-related death in North America. Matrix metalloproteinases (MMPs) have long been targeted as a potential anticancer therapy because of their seminal role in angiogenesis and extracellular matrix (ECM) degradation of tumor survival and invasion. However, the inhibition specificity to MMPs and the molecular-level understanding of the inhibition mechanism remain largely unresolved. Here, we found that endohedral metallofullerenol Gd@C82(OH)22 can successfully inhibit the neoplastic activity with experiments at animal, tissue, and cellular levels. Gd@C82(OH)22 effectively blocks tumor growth in human pancreatic cancer xenografts in a nude mouse model. Enzyme activity assays also show Gd@C82(OH)22 not only suppresses the expression of MMPs but also significantly reduces their activities. We then applied large-scale molecular-dynamics simulations to illustrate the molecular mechanism by studying the Gd@C82(OH)22–MMP-9 interactions in atomic detail. Our data demonstrated that Gd@C82(OH)22 inhibits MMP-9 mainly via an exocite interaction, whereas the well-known zinc catalytic site only plays a minimal role. Steered by nonspecific electrostatic, hydrophobic, and specific hydrogen-bonding interactions, Gd@C82(OH)22 exhibits specific binding modes near the ligand-specificity loop S1′, thereby inhibiting MMP-9 activity. Both the suppression of MMP expression and specific binding mode make Gd@C82(OH)22 a potentially more effective nanomedicine for pancreatic cancer than traditional medicines, which usually target the proteolytic sites directly but fail in selective inhibition. Our findings provide insights for de novo design of nanomedicines for fatal diseases such as pancreatic cancer.

The effect of Gd@C82(OH)22 nanoparticles on the release of Th1/Th2 cytokines and induction of TNF-α mediated cellular immunity

It is known that down-regulation of the immune response may be associated with the progenesis, development and prognosis of cancer or infectious diseases. Up-regulating the immune response in vivo is therefore a desirable strategy for clinical treatment. Here we report that poly-hydroxylated metallofullerenol (Gd@C(82)(OH)(22)) has biomedical functions useful in anticancer therapy arising from immunomodulatory effects observed both in vivo and in vitro. We found that metallofullerenol can inhibit the growth of tumors, and shows specific immunomodulatory effects on T cells and macrophages. These effects include polarizing the cytokine balance towards Th1 (T-helper cell type 1) cytokines, decreasing the production of Th2 cytokines (IL-4, IL-5 and IL-6), and increasing the production of Th1 cytokines (IL-2, IFN-gamma and TNF-alpha) in the serum samples. Immune-system regulation by this nanomaterial showed dose-dependent behavior: at a low concentration, Gd@C(82)(OH)(22) nanoparticles slightly affected the activity of immune cells in vitro, while at a high concentration, they markedly enhanced immune responses and stimulated immune cells to release more cytokines, helping eliminate abnormal cells. Gd@C(82)(OH)(22) nanoparticles stimulated T cells and macrophages to release significantly greater quantities of TNF-alpha, which plays a key role in cellular immune processes. Gd@C(82)(OH)(22) nanoparticles are more effective in inhibiting tumor growth in mice than some clinical anticancer drugs but have negligible side effects. The underlying mechanism for high anticancer activity may be attributed to the fact that this water-soluble nanomaterial effectively triggers the host immune system to scavenge tumor cells.

Size-dependent cytotoxicity of yttrium oxide nanoparticles on primary osteoblasts in vitro

Yttrium oxide nanoparticles are an excellent host material for the rare earth metals and have high luminescence efficiency providing a potential application in photodynamic therapy and biological imaging. In this study, the effects of yttrium oxide nanoparticles with four different sizes were investigated using primary osteoblasts in vitro. The results demonstrated that the cytotoxicity generated by yttrium oxide nanoparticles depended on the particle size, and smaller particles possessed higher toxicological effects. For the purpose to elucidate the relationship between reactive oxygen species generation and cell damage, cytomembrane integrity, intracellular reactive oxygen species level, mitochondrial membrane potential, cell apoptosis rate, and activity of caspase-3 in cells were then measured. Increased reactive oxygen species level was also observed in a size-dependent way. Thus, our data demonstrated that exposure to yttrium oxide nanoparticles resulted in a size-dependent cytotoxicity in cultured primary osteoblasts, and reactive oxygen species generation should be one possible damage pathway for the toxicological effects produced by yttrium oxide particles. The results may provide useful information for more rational applications of yttrium oxide nanoparticles in the future.

Poly(lactic-co-glycolic acid)/Polycaprolactone Nanofibrous Membranes for High-Efficient Capture of Nano- and Microsized Particulate Matter

The incidence of many diseases is closely related to air pollution. Suspended particulate matter of different sizes represents a major source of environmental pollution. Fine particles, especially ultrafine particles smaller than 2.5 μm, might be more harmful to human health because of their extremely small size, which enables them to penetrate human lungs and bronchi and makes them difficult to filter out. Therefore, the fatal risks associated with PM call for the development of air purification materials with high efficiency and low resistance. In this study, poly(lactic-co-glycolic acid) and polycaprolactone were used to prepare nanofibrous membranes suitable for the efficient capture of particulate matter formed in haze-fog episodes, especially particles smaller than 0.5 μm. The present nanofibrous membranes exhibit superior filtration efficiency for particulate matter, with a much lower pressure drop compared to typical commercial microfiber air filters. Thanks to the combination of small pore size, high porosity, and robust mechanical properties, the poly(lactic-co-glycolic acid)/polycaprolactone (6:4) composite membrane exhibits a high filtration efficiency of 97.81% and a low pressure drop of 181 Pa. These favorable features, combined with the easy availability and biocompatibility of the component materials, highlight the promising potential of the present nanofibrous membranes for the development of personal wearable air purifiers.

A Distinct Endocytic Mechanism of Functionalized-Silica Nanoparticles in Breast Cancer Stem Cells

Nanoparticles provide new fields for life medical science application, including targeted-drug delivery and cancer treatment. To maximize the delivery efficiency of nanoparticle, one must understand the uptake mechanism of nanoparticle in cells, which may determine their ultimate fate and localization in cells. Recently, the proposed-cancer stem cell (CSC) theory has been attracted great attention and regarded as new targets for the new nanodrug developmet and cancer therapies. The interaction between nanoparticles and cancer cells has been extensively studied, but the uptake mechanism of nanoparticles in CSCs has received little attention. Here, we use the pharmacological inhibitors of major endocytic pathways to study the silica nanoparticle (SiNP) uptake mechanisms in the human breast adenocarcinoma cell line (MCF-7) and MCF-7-derived breast cancer stem cells (BCSCs). The results demonstrate that the uptake of SiNPs, particularly amino-functionalized SiNPs, in MCF-7 cells is strongly affected by the actin depolymerization, whereas BCSCs more strongly inhibit the amino-functionalized SiNP uptake after the scavenger receptor disruption. These findings indicate a distinct endocytic mechanism of functionalized SiNPs in BCSCs, which is significant for designing ideal nanosized drug delivery systems and improving the selectivity for CSC-targeted therapy.

Mussel Inspired Polynorepinephrine Functionalized Electrospun Polycaprolactone Microfibers for Muscle Regeneration

Electrospun scaffolds with excellent mechanical properties, high specific surface area and a commendable porous network are widely used in tissue engineering. Improving the hydrophilicity and cell adhesion of hydrophobic substrates is the key point to enhance the effectiveness of electrospun scaffolds. In this study, polycaprolactone (PCL) fibrous membranes with appropriate diameter were selected and coated by mussel-inspiredxa0poly norepinephrine (pNE). And norepinephrine is a catecholamine functioning as a hormone and neurotransmitter in the human brain. The membrane with smaller diameter fibers, a relative larger specific surface area and the suitable pNE functionalization provided more suitable microenvironment for cell adhesion and proliferation both in vitro and in vivo. The regenerated muscle layer can be integrated well with fibrous membranes and surrounding tissues at the impaired site and thus the mechanical strength reached the value of native tissue. The underlying molecular mechanism is mediated via inhibiting myostatin expression by PI3K/AKT/mTOR hypertrophy pathway. The properly functionalized fibrous membranes hold the potential for repairing muscle injuries. Our current work also provides an insight for rational design and development of better tissue engineering materials for skeletal muscle regeneration.

Innovative biodegradable poly(L-lactide)/collagen/ hydroxyapatite composite fibrous scaffolds promote osteoblastic proliferation and differentiation

The development of an artificial bone graft which can promote the regeneration of fractures or diseased bones is currently the most challenging aspect in bone tissue engineering. To achieve the purpose of promoting bone proliferation and differentiation, the artificial graft needs have a similar structure and composition of extracellular matrix. One-step electrospinning method of biocomposite nanofibers containing hydroxyapatite (HA) nanoparticles and collagen (Coll) were developed for potential application in bone tissue engineering. Nanocomposite scaffolds of poly(L-lactide) (PLLA), PLLA/HA, PLLA/Coll, and PLLA/Coll/HA were fabricated by electrospinning. The morphology, diameter, elements, hydrophilicity, and biodegradability of the composite scaffolds have been investigated. The biocompatibility of different nanocomposite scaffolds was assessed using mouse osteoblasts MC3T3-E1 in vitro, and the proliferation, differentiation, and mineralization of cells on different nanofibrous scaffolds were investigated. The results showed that PLLA/Coll/HA nanofiber scaffolds enhanced cell adhesion, spreading, proliferation, differentiation, mineralization, and gene expression of osteogenic markers compared to other scaffolds. In addition, the nanofibrous scaffolds maintained a stable composition at the beginning of the degradation period and morphology wastage and weight loss were observed when incubated for up to 80 days in physiological simulated conditions. The PLLA/Coll/HA composite nanofibrous scaffolds could be a potential material for guided bone regeneration.

Quantitative Analysis on Cellular Uptake of Hydroxyapatite Nanoparticles in the Primary Osteoblasts in Vitro

With the fast development of nanotechnology, the nanomaterials have raised questions concerning its potential toxic effects on human health. In this study, the effects of hydroxyapatite nanoparticles on the primary osteoblasts were investigated. As an indicator of membrane damage, lactate dehydrogenase was quantitatively assessed. The quantitative analysis on cellular uptake of hydroxyapatite nanoparticles could be detected by flow cytometer and inductively coupled plasma mass spectrometry, respectively. The results demonstrated that hydroxyapatite nanoparticles can enter cells through cell membrane and the nanoparticles taken up in the cells followed dose and time dependent manner. The methods could be used for the initial screening of the uptake potential of nanoparticles as an index of nanotoxicity.