Guangjun Nie

Physicochemical properties determine nanomaterial cellular uptake, transport and fate

Although a growing number of innovations have emerged in the fields of nanobiotechnology and nanomedicine, new engineered nanomaterials (ENMs) with novel physicochemical properties are posing novel challenges to understand the full spectrum of interactions at the nano-bio interface. Because these could include potentially hazardous interactions, researchers need a comprehensive understanding of toxicological properties of nanomaterials and their safer design. In depth research is needed to understand how nanomaterial properties influence bioavailability, transport, fate, cellular uptake, and catalysis of injurious biological responses. Toxicity of ENMs differ with their size and surface properties, and those connections hold true across a spectrum of in vitro to in vivo nano-bio interfaces. In addition, the in vitro results provide a basis for modeling the biokinetics and in vivo behavior of ENMs. Nonetheless, we must use caution in interpreting in vitro toxicity results too literally because of dosimetry differences between in vitro and in vivo systems as well the increased complexity of an in vivo environment. In this Account, we describe the impact of ENM physicochemical properties on cellular bioprocessing based on the research performed in our groups. Organic, inorganic, and hybrid ENMs can be produced in various sizes, shapes and surface modifications and a range of tunable compositions that can be dynamically modified under different biological and environmental conditions. Accordingly, we cover how ENM chemical properties such as hydrophobicity and hydrophilicity, material composition, surface functionalization and charge, dispersal state, and adsorption of proteins on the surface determine ENM cellular uptake, intracellular biotransformation, and bioelimination versus bioaccumulation. We review how physical properties such as size, aspect ratio, and surface area of ENMs influence the interactions of these materials with biological systems, thereby affecting their hazard potential. We discuss our actual experimental findings and show how these properties can be tuned to control the uptake, biotransformation, fate, and hazard of ENMs. This Account provides specific information about ENM biological behavior and safety issues. This research also assists the development of safer nanotherapeutics and guides the design of new materials that can execute novel functions at the nano-bio interface.

A doxorubicin delivery platform using engineered natural membrane vesicle exosomes for targeted tumor therapy.

Targeted drug delivery vehicles with low immunogenicity and toxicity are needed for cancer therapy. Here we show that exosomes, endogenous nano-sized membrane vesicles secreted by most cell types, can deliver chemotherapeutics such as doxorubicin (Dox) to tumor tissue in BALB/c nude mice. To reduce immunogenicity and toxicity, mouse immature dendritic cells (imDCs) were used for exosome production. Tumor targeting was facilitated by engineering the imDCs to express a well-characterized exosomal membrane protein (Lamp2b) fused to αv integrin-specific iRGD peptide (CRGDKGPDC). Purified exosomes from imDCs were loaded with Dox via electroporation, with an encapsulation efficiency of up to 20%. iRGD exosomes showed highly efficient targeting and Dox delivery to αv integrin-positive breast cancer cells in vitro as demonstrated by confocal imaging and flow cytometry. Intravenously injected targeted exosomes delivered Dox specifically to tumor tissues, leading to inhibition of tumor growth without overt toxicity. Our results suggest that exosomes modified by targeting ligands can be used therapeutically for the delivery of Dox to tumors, thus having great potential value for clinical applications.

Enhanced anti-tumor efficacy by co-delivery of doxorubicin and paclitaxel with amphiphilic methoxy PEG-PLGA copolymer nanoparticles

The use of single chemotherapeutic drug has shown some limitations in anti-tumor treatment, such as development of drug resistance, high toxicity and limited regime of clinical uses. The combination of two or more therapeutic drugs is feasible means to overcome the limitations. Co-delivery strategy has been proposed to minimize the amount of each drug and to achieve the synergistic effect for cancer therapies. Attempts have been made to deliver chemotherapeutic drugs simultaneously using drug carriers, such as micelles, liposomes, and inorganic nanoparticles (NPs). Here we reported core-shell NPs that were doubly emulsified from an amphiphilic copolymer methoxy poly(ethylene glycol)-poly(lactide-co-glycolide) (mPEG-PLGA). These NPs offered advantages over other nanocarriers, as they were easy to fabricate by improved double emulsion method, biocompatible, and showed high loading efficacy. More importantly, these NPs could co-deliver hydrophilic doxorubicin (DOX) and hydrophobic paclitaxel (TAX). The drug-loaded NPs possessed a better polydispersity, indicating that they are more readily subject to controlled size distribution. Studies on drug release and cellular uptake of the co-delivery system demonstrated that both drugs were effectively taken up by the cells and released simultaneously. Furthermore, the co-delivery nanocarrier suppressed tumor cells growth more efficiently than the delivery of either DOX or TAX at the same concentrations, indicating a synergistic effect. Moreover, the NPs loading drugs with a DOX/TAX concentration ratio of 2:1 showed the highest anti-tumor activity to three different types of tumor cells. This nanocarrier might have important potential in clinical implications for co-delivery of multiple anti-tumor drugs with different properties.

Structure-activity relationship analysis of antioxidant ability and neuroprotective effect of gallic acid derivatives

Gallic acid and its derivatives are a group of naturally occurring polyphenol antioxidants which have recently been shown to have potential healthy effects. In order to understand the relationship between the structures of gallic acid derivatives, their antioxidant activities, and neuroprotective effects, we examined their free radical scavenging effects in liposome and anti-apoptotic activities in human SH-SY5Y cell induced by 6-hydrodopamine autooxidation. It was found that these polyphenol antioxidants exhibited different hydrophobicity and could cross through the liposome membrane to react with 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical in a time and dose-dependent manner. At the same time, the structure-antioxidant activity relationship of gallic acid derivatives on scavenging DPPH free radical in the liposome was also analyzed based on theoretical investigations. Analysis of cell apoptosis, intracellular GSH levels, production of ROS and the influx of Ca(2+) indicated that the protective effects of gallic acid derivatives in cell systems under oxidative stress depend on both their antioxidant capacities and hydrophobicity. However, the neuroprotective effects of gallic acid derivatives seem to depend more on their molecular polarities rather than antioxidant activities in the human SH-SY5Y cell line. In conclusion, these results reveal that compounds with high antioxidant activity and appropriate hydrophobicity are generally more effective in preventing the injury of oxidative stress in neurodegenerative diseases.

Facet-Mediated Photodegradation of Organic Dye over Hematite Architectures by Visible Light†

Structure–reactivity correlations are a central theme in heterogeneous catalysis. In general, the crystallographic surface structure of a catalyst is determined by its exposed facets, and the enclosed facets of a particle-like catalyst in turn determine its geometric shape as well as catalytic properties. Tuning the shape of catalysts, therefore, is essential in developing new catalysts and modifying existing ones with desirable reactivity, selectivity, and stability. Indeed, great advances have been achieved on model catalysts, and insights into the structure–reactivity correlations are crucial not only for our understanding of catalytic processes, but also for generating new concepts to guide the rational design of practical catalysts. In recent years, significant attention has been directed towards using solar-driven photocatalysts to degrade aqueous organic pollutants (for example, azo dyes). In view of being naturally abundant and environmentally benign, iron oxides show great promise. Among iron oxides, hematite (aFe2O3) is the most thermodynamically stable semiconductor (Eg = 2.1–2.2 eV) that can absorb visible light, that is, a substantial fraction of the solar spectrum. a-Fe2O3 has a wide range of applications, such as light-induced water splitting, solar cells, lithium ion batteries, and biotechnology. Most studies to date have been carried out on powder substrates in which particle shapes are inherently not welldefined, making it difficult to explore the structure–reactivity correlations. While the vast majority of studies on the impact of particle shape on photocatalytic reactivity are limited to titanium dioxide (TiO2), [18–27] far less information is available regarding the shape effects on other photocatalysts, including iron oxides. In this regard, systematic studies on heterogeneous photo-Fenton catalysis, a technologically promising process in wastewater treatment, by iron-bearing nanocatalysts with particular shapes are still lacking. 29] Over the past decade, size, shape, and architecture control of low-dimensional nanomaterials (for example, nanodots, nanorods, and nanosheets) with unusual properties has seen rapid growth. For example, in one-dimensional (1D) anisotropic nanostructures, it is possible to enhance the photoreactivity by tuning the direction and path of photogenerated charge carriers through quantum confinement while minimizing the e –h recombination. Herein, we investigate visible-light-induced photodegradation of model dye rhodamine B (RhB) in the presence of hydrogen peroxide (H2O2) over hematite architectures, namely 1D nanorods, 2D nanoplates, and 3D nanocubes. Herein we use “architectures” to describe hematite nanostructures that can be assembled by nano-building units by oriented attachment. 36, 39] To the best of our knowledge, this is the first study to investigate heterogeneous photo-Fenton catalysis by nanocatalysts with well-defined architectures. The detailed synthesis of a-Fe2O3 architectures [39–42] is described in the Experimental Section and the Supporting Information. The structure, stoichiometry, and oxidation state of the as-prepared a-Fe2O3 architectures were characterized using X-ray diffraction (XRD; Supporting Information, Figure S1a), micro-Raman (Supporting Information, Figure S1b), and high-resolution X-ray photoelectron spectroscopy (XPS; Supporting Information, Figure S1c,d), and results demonstrate that all samples are pure a-Fe2O3 with a rhombohedral hexagonal phase (space group R3̄c). The morphology and crystallinity of as-prepared a-Fe2O3 architectures were analyzed using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). A TEM image for 2D nanoplates is shown in Figure 1a. All of the nanoplates display a well-defined hexagonal shape. Based on a SEM (Supporting Information, Figure S2a) and TEM analysis (Figure 1 a; Supporting Information, Figure S2b), the width and thickness of the plates is determined to be (208.5 27.3) and (14.6 2.6) nm, respectively. A representative HRTEM image (Figure 1 b) and fast Fourier transforms (FFT; inset in Figure 1b) show the lattice fringe to be 0.25 nm, which is consistent with (110), ( 120), and ( 210) planes, respectively. Thus, the resulting basal plane is (001). Vertically aligned plates that are frequently observed (Supporting Information, Figure S2b,c) are wedgeshaped and the lateral facets are ascribed to {102}. A TEM [*] X. M. Zhou, J. Y. Lan, Prof. G. Liu, Prof. K. Deng, Prof. Y. L. Yang, Prof. G. J. Nie, Prof. L. J. Zhi National Center for Nanoscience and Technology Beijing, 100190 (China) E-mail: liug@nanoctr.cn zhilj@nanoctr.cn

Controlling Assembly of Paired Gold Clusters within Apoferritin Nanoreactor for in Vivo Kidney Targeting and Biomedical Imaging

Functional nanostructures with high biocompatibility and stability, low toxicity, and specificity of targeting to desired organs or cells are of great interest in nanobiology and medicine. However, the challenge is to integrate all of these desired features into a single nanobiostructure, which can be applied to biomedical applications and eventually in clinical settings. In this context, we designed a strategy to assemble two gold nanoclusters at the ferroxidase active sites of ferritin heavy chain. Our studies showed that the resulting nanostructures (Au-Ft) retain not only the intrinsic fluorescence properties of noble metal, but gain enhanced intensity, show a red-shift, and exhibit tunable emissions due to the coupling interaction between the paired Au clusters. Furthermore, Au-Ft possessed the well-defined nanostructure of native ferritin, showed organ-specific targeting ability, high biocompatibility, and low cytotoxicity. The current study demonstrates that an integrated multimodal assembly strategy is able to generate stable and effective biomolecule-noble metal complexes of controllable size and with desirable fluorescence emission characteristics. Such agents are ideal for targeted in vitro and in vivo imaging. These results thus open new opportunities for biomolecule-guided nanostructure assembly with great potential for biomedical applications.

Unraveling stress-induced toxicity properties of graphene oxide and the underlying mechanism.

Graphene oxide shows stress-induced toxicity properties in vivo under different pathophysiological conditions. A dual-path chemical mechanism, involving the overproduction of hydroxyl radicals and the formation of oxidizing cytochrome c intermediates, is responsible for the toxicity properties.

Chirality of Glutathione Surface Coating Affects the Cytotoxicity of Quantum Dots

Quantum dots (QDs) have been extensively investigated as fluorescent probes and are emerging as a new class of agents for biomedical imaging and diagnosis because of their broad absorption profiles, tunable emission wavelengths, and high photooxidation stability. QDs consist of an inorganic core surrounded by an organic shell. Normally, different types of biomolecules, such as amino acids, DNA, or peptides, are used for the organic shell to facilitate water solubility and biocompatibility of the QDs. However, because the core may contain toxic heavy metals (e.g., Cd, Hg, Pb, and Zn), the potential cytotoxicity of QDs has been a major impediment to their widespread application. It has therefore become critical to fully understand the interactions between QDs and living cells in order to develop nontoxic and biocompatible QDs for clinical use. Early studies have suggested that the release of core components, the generation of reactive oxygen species (ROS), and nonspecific binding to cellular membranes and intracellular proteins are the major mechanisms of the observed cytotoxic effects of QDs. Despite a significant surge in the number of investigations into the cytotoxicity of QDs, there is currently only limited knowledge about the cytological and physiological mediators of these effects. Interestingly, recent data have suggested that the induction of autophagy by certain sizes of QDs could play an important role in their toxic actions. Autophagy is a metabolic process involved in protein and organelle degradation and plays key roles in maintaining cellular homeostasis and contributing to cellular defense. It has been recognized as a third pathway of cell death, after apoptosis and necrosis, and is responsive to various physicopathological stimuli. Recent work has shown that small QDs (< 10 nm) rather than those with larger sizes (40–50 nm) induce autophagy in cultured cells. This size-dependent induction of autophagy has also been reported for other nanoparticles (NPs). However, all the above studies focused on the effects of type and size of the NPs, while other factors that may induce autophagy remain unexplored. Although many studies have demonstrated that surface modification of QDs with biomolecules endows them with various biological functionalities, the impact on living organisms of the chirality of the surface biomolecules has been largely neglected. Chirality is an important phenomenon in living systems and nearly all biological polymers must be homochiral to function. For example, all amino acids in proteins are “left-handed”, whereas all sugars in DNA and RNA are “right-handed”. Different chiral properties of biomolecules may determine their ability to interact with other biomolecules and thereby modulate a range of downstream processes. More recently, several attempts to develop chiral QDs with optical activities using different chiral stabilizers have been reported. Herein, the effects of QDs capped with different chiral forms of the tripeptide glutathione (GSH) on cytotoxicity and induction of autophagy were examined. Two different sizes of cadmium telluride (CdTe) QDs coated with either l-GSH (lGSH-QDs) or d-GSH (d-GSH-QDs) were found to show dose-dependent cytotoxicity and to significantly increase the levels of autophagic vacuoles. The activation of autophagy was chirality-dependent, with l-GSH-QDs being more effective than d-GSH-QDs. The ability of QDs to induce cell death was correlated with their ability to induce autophagy. This chirality-associated regulation of cellular metabolism and cytotoxicity highlights the important role of the conformation of the stabilizers, and has important implications for the design of novel QDs with enhanced optical properties and reduced or no toxicity. In this study, negatively charged water-soluble CdTe QDs were synthesized according to the Rogach–Weller method and coated with different chiral forms of GSH as stabilizers (Figure 1a). To clearly understand the chirality effect, two series of QDs were prepared. Group 1 comprised small-sized [*] Y. Li, Prof. Y. Zhao, Prof. G. Nie CAS Key Laboratory for Biological Effects of Nanomaterials & Nanosafety, National Center for Nanoscience and Technology 11 Beiyijie, Zhongguancun, Beijing 100190 (China) E-mail: niegj@nanoctr.cn

Localized Electric Field of Plasmonic Nanoplatform Enhanced Photodynamic Tumor Therapy

Near-infrared plasmonic nanoparticles demonstrate great potential in disease theranostic applications. Herein a nanoplatform, composed of mesoporous silica-coated gold nanorods (AuNRs), is tailor-designed to optimize the photodynamic therapy (PDT) for tumor based on the plasmonic effect. The surface plasmon resonance of AuNRs was fine-tuned to overlap with the exciton absorption of indocyanine green (ICG), a near-infrared photodynamic dye with poor photostability and low quantum yield. Such overlap greatly increases the singlet oxygen yield of incorporated ICG by maximizing the local field enhancement, and protecting the ICG molecules against photodegradation by virtue of the high absorption cross section of the AuNRs. The silica shell strongly increased ICG payload with the additional benefit of enhancing ICG photostability by facilitating the formation of ICG aggregates. As-fabricated AuNR@SiO2-ICG nanoplatform enables trimodal imaging, near-infrared fluorescence from ICG, and two-photon luminescence/photoacoustic tomography from the AuNRs. The integrated strategy significantly improved photodynamic destruction of breast tumor cells and inhibited the growth of orthotopic breast tumors in mice, with mild laser irradiation, through a synergistic effect of PDT and photothermal therapy. Our study highlights the effect of local field enhancement in PDT and demonstrates the importance of systematic design of nanoplatform to greatly enhancing the antitumor efficacy.

Protective effects of green tea polyphenols and their major component, (-)-epigallocatechin-3-gallate (EGCG), on 6-hydroxydopamine-induced apoptosis in PC12 cells.

Abstract Green tea polyphenols exert a wide range of biochemical and pharmacological effects, and have been shown to possess antimutagenic and anticarcinogenic properties. Oxidative stress is involved in the pathogenesis of Parkinsons disease. However, although green tea polyphenols may be expected to inhibit the progression of Parkinsons disease on the basis of their known antioxidant activity, this has not previously been established. In the present study, we evaluated the neuroprotective effects of green tea polyphenols in the Parkinsons disease pathological cell model. The results show that the natural antioxidants have significant inhibitory effects against apoptosis induced by oxidative stress. 6-Hydroxydopamine (6-OHDA)-induced apoptosis in catecholaminergic PC12 cells was chosen as the in vitro model of Parkinsons disease in our study. Apoptotic characteristics of PC12 cells were assessed by MTT assay, flow cytometry, fluorescence microscopy and DNA fragmentation. Green tea polyphenols and their major component, EGCG at a concentration of 200 μM, exert significant protective effects against 6-OHDA-induced PC12 cell apoptosis. EGCG is more effective than the mixture of green tea polyphenols. The antioxidant function of green tea polyphenols may account for this neuroprotective effect. The present study supports the notion that green tea polyphenols have the potential to be effective as neuropreventive agents for the treatment of neurodegenerative diseases.