Leng Nie

Bio: Leng Nie is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Nanobiotechnology & Gene delivery. The author has an hindex of 4, co-authored 5 publications receiving 3539 citations.

Intrinsic peroxidase-like activity of ferromagnetic nanoparticles

Abstract: Nanoparticles containing magnetic materials, such as magnetite (Fe3O4), are particularly useful for imaging and separation techniques. As these nanoparticles are generally considered to be biologically and chemically inert, they are typically coated with metal catalysts, antibodies or enzymes to increase their functionality as separation agents. Here, we report that magnetite nanoparticles in fact possess an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, which are widely used to oxidize organic substrates in the treatment of wastewater or as detection tools. Based on this finding, we have developed a novel immunoassay in which antibody-modified magnetite nanoparticles provide three functions: capture, separation and detection. The stability, ease of production and versatility of these nanoparticles makes them a powerful tool for a wide range of potential applications in medicine, biotechnology and environmental chemistry.

Carbon nanotube delivery of the GFP gene into mammalian cells.

Abstract: Exogenous-gene expression and manipulation in mammalian cells has become a mainstay of biomedical research. Consequently, improving methods for efficient gene transfer to a broad range of cell types is of great interest and remains a high priority. Several classes of transfection methods have been developed, which include traditional cationic moleculemediated agents, such as Lipofectamine 20000 and FuGENE 6, viral-vector systems, and the “gene gun” approach. With the rapid development of nanobiotechnology, a variety of new materials, such as gold nanoparticles, silica nanoparticles, polymers, nanogels, and dendrimers have been investigated as biocompatible transporters. Recently, carbon nanotube—a well-studied nanomaterial— have been investigated for their ability to interact with and affect living systems. For instance, carbon nanotubes have been found to enhance DNA amplification in PCR and affect the growth pattern of neurons. Pantarotto et al. have reported the internalization of fluorescein isothiocynate (FITC) labeled nanotubes and nanotube delivery of the gene that encodes b-galactosidase into cells, with no apparent toxic effects. Kam et al. have studied the mechanism of protein-conjugated carbon nanotube uptake into cells via the endocytic pathway. Here we present our finding that amino-functionalized multiwalled carbon nanotubes (NH2-MWCNTs) are able to interact with plasmid DNA and deliver the green fluorescence protein (GFP) gene into cultured human cells. Our data strongly suggest that carbon nanotubes can be considered as a new carrier for the delivery of biomolecules, such as DNA, proteins, and peptides into mammalian cells. Therefore, this novel system might have potential applications in biology and therapy, including vaccine and gene delivery. In order to increase their biocompatibility, we introduced amino-, carboxyl-, hydroxyl-, and alkyl groups onto the surface of MWCNTs. COOH-MWCNTs were first prepared by nitric / sulfuric acid oxidation, and then NH2and CH3CH2CH2-groups were added. Finally, we obtained four types of MWCNTs with different chemical groups on their surface. Functionalized MWCNTs were observed under an electron microscope and were found to be 60–70 nm in diameter and 1–2 mm in length. Although we did not find a significant difference in size between the NH2-MWCNTs and NH2-MWCNT–DNAs, the latter appeared to have the tendency to aggregate (Figure 1B). In order to test the DNA-binding ability of amino-, carboxyl-, hydroxyl-, and alkyl-group-modified MWCNTs, we incubated them with pEGFPN1-plasmid DNA, and MWCNT–DNA mixtures were analyzed by agarose-gel electrophoresis. The results show that only NH2-MWCNT bound to DNA (Figure 2); since the NH2-MWCNT–DNA complex was too big to run into the

Three-dimensional functionalized tetrapod-like ZnO nanostructures for plasmid DNA delivery.

Abstract: Due to their special electrical, optical, and magnetic properties, materials less than 100 nm in size are very promising for biosensors, bio-separation, and drug delivery. In recent years liposomes and polymers have been used as carriers for transfections. Certain inorganic materials such as silica nanoparticles, carbon nanotubes, and silica nanotubes have been used as transporters with little toxicity in mammalian-cell transfections. These zero-dimensional nanoparticles and one-dimensional nanotubes suggest that nanomaterials, if modified properly, can be used as carriers for transfections. However, the application of three-dimensional nanostructures as biomolecule carriers is less well-studied. Here, we report three-dimensional functionalized tetrapod-like ZnO nanostructures as novel carriers for mammalian cell transfections. In this work, silica-coated amino-modifed nanostructures were prepared. Through electrostatic interactions, ZnO tetrapods could be bound to plasmid DNA. When mixed with cells, the tetrapods attached to cell membranes. Just as phages stand on cells with six legs suitable for gene delivery, ZnO nanostructures stand on the cells with three needle-shaped legs for DNA delivery as a result of their tetrapodal shape. With three tips located on the cell surfaces, the opportunity of internalization of the tips by cells should be increased. In addition, the geometry of the tetrapods imply a much larger steric hindrance, which makes it difficult for the tetrapods to pass wholly through the cell membranes. Just as phages insert genes into cells without entering them, tetrapods delivered plasmid DNA into the cells while standing on the cell membrane. This result is helpful in decreasing any cytotoxic effects. These results demonstrate a novel application of tetrapod-like nanostructures for gene delivery. Three-dimensional ZnO nanostructures were synthesized by thermal evaporation at 900 8C. The nanostructures consisted of four needle-shaped tetrahedrally arranged legs connected at the center, forming a tetrapod-like ZnO structure. The legs were single-crystalline and stable in air, with a mean diameter of 80 nm and a length of 5–10 mm. As shown in Figure 1A, one of the needle-shaped legs was per-

Functionalized tetrapod-like ZnO nanostructures for plasmid DNA purification, polymerase chain reaction and delivery

Abstract: Functionalized tetrapodal ZnO nanostructures are tested in plasmid DNA experiments (1) as a solid-phase adsorbent for plasmid DNA purification, (2) as improving reagents in a polymerase chain reaction (PCR) and (3) as novel carriers for gene delivery. The amino-modification, the tetrapod-like shape of the nanostructure and its high biocompatibility all contribute to measurements showing promise for applications. A sol-gel method is used for silica coating and amino-modification. Plasmid DNA is purified through reversible conjugations of amino-modified ZnO tetrapods with DNA. Also, as additional reagents, functionalized tetrapods are shown to improve the amount of PCR product. For transfection, ZnO tetrapods provide some protection against deoxyribonuclease cleavage of plasmid DNA and deliver plasmid DNA into cells with little cytotoxicity.

Functionalized tetrapod-like ZnO nanostructrures for DNA gene delivery

Abstract: Amino-modified tetrapod-like ZnO nanostructures were tried as novel carriers for mammalian cell transfections. The nanostructures consisted of four needle-shaped tetrahedrally arranged legs connected at the center. After silica coating and amino modification, ZnO nanostructures complexes bound plasmid DNA through electrostatic interactions in aqueous solution. When mixed with cells, DNA-nanostructures attached easily onto cell membranes and entered the cells for gene expressions. Due to high positive charge densities on surfaces and needle-shaped tetrahedral structures, functionalized ZnO used as carriers for cell transfections with both high transfection efficiency and little cytotoxicity. And a possible transfection machamism was proposed in this report.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes

Abstract: Over the past few decades, researchers have established artificial enzymes as highly stable and low-cost alternatives to natural enzymes in a wide range of applications. A variety of materials including cyclodextrins, metal complexes, porphyrins, polymers, dendrimers and biomolecules have been extensively explored to mimic the structures and functions of naturally occurring enzymes. Recently, some nanomaterials have been found to exhibit unexpected enzyme-like activities, and great advances have been made in this area due to the tremendous progress in nano-research and the unique characteristics of nanomaterials. To highlight the progress in the field of nanomaterial-based artificial enzymes (nanozymes), this review discusses various nanomaterials that have been explored to mimic different kinds of enzymes. We cover their kinetics, mechanisms and applications in numerous fields, from biosensing and immunoassays, to stem cell growth and pollutant removal. We also summarize several approaches to tune the activities of nanozymes. Finally, we make comparisons between nanozymes and other catalytic materials (other artificial enzymes, natural enzymes, organic catalysts and nanomaterial-based catalysts) and address the current challenges and future directions (302 references).

Graphene oxide: intrinsic peroxidase catalytic activity and its application to glucose detection.

Abstract: Carboxyl-modified graphene oxide (GO-COOH) possesses intrinsic peroxidase-like activity that can catalyze the reaction of peroxidase substrate 3,3,5,5-tetramethyl-benzidine (TMB) in the presence of H2O2 to produce a blue color reaction. A simple, cheap, and highly sensitive and selective colorimetric method for glucose detection has been developed and will facilitate the utilization of GO-COOH intrinsic peroxidase activity in medical diagnostics and biotechnology.

Nanozymes: Classification, Catalytic Mechanisms, Activity Regulation, and Applications

Abstract: Because of the high catalytic activities and substrate specificity, natural enzymes have been widely used in industrial, medical, and biological fields, etc. Although promising, they often suffer from intrinsic shortcomings such as high cost, low operational stability, and difficulties of recycling. To overcome these shortcomings, researchers have been devoted to the exploration of artificial enzyme mimics for a long time. Since the discovery of ferromagnetic nanoparticles with intrinsic horseradish peroxidase-like activity in 2007, a large amount of studies on nanozymes have been constantly emerging in the next decade. Nanozymes are one kind of nanomaterials with enzymatic catalytic properties. Compared with natural enzymes, nanozymes have the advantages such as low cost, high stability and durability, which have been widely used in industrial, medical, and biological fields. A thorough understanding of the possible catalytic mechanisms will contribute to the development of novel and high-efficient nanozymes, and the rational regulations of the activities of nanozymes are of great significance. In this review, we systematically introduce the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years. We also propose the current challenges of nanozymes as well as their future research focus. We anticipate this review may be of significance for the field to understand the properties of nanozymes and the development of novel nanomaterials with enzyme mimicking activities.

Carbon Nanotubes in Biology and Medicine: In vitro and in vivo Detection, Imaging and Drug Delivery

Abstract: Carbon nanotubes exhibit many unique intrinsic physical and chemical properties and have been intensively explored for biological and biomedical applications in the past few years. In this comprehensive review, we summarize the main results from our and other groups in this field and clarify that surface functionalization is critical to the behavior of carbon nanotubes in biological systems. Ultrasensitive detection of biological species with carbon nanotubes can be realized after surface passivation to inhibit the non-specific binding of biomolecules on the hydrophobic nanotube surface. Electrical nanosensors based on nanotubes provide a label-free approach to biological detection. Surface-enhanced Raman spectroscopy of carbon nanotubes opens up a method of protein microarray with detection sensitivity down to 1 fmol/L. In vitro and in vivo toxicity studies reveal that highly water soluble and serum stable nanotubes are biocompatible, nontoxic, and potentially useful for biomedical applications. In vivo biodistributions vary with the functionalization and possibly also size of nanotubes, with a tendency to accumulate in the reticuloendothelial system (RES), including the liver and spleen, after intravenous administration. If well functionalized, nanotubes may be excreted mainly through the biliary pathway in feces. Carbon nanotube-based drug delivery has shown promise in various In vitro and in vivo experiments including delivery of small interfering RNA (siRNA), paclitaxel and doxorubicin. Moreover, single-walled carbon nanotubes with various interesting intrinsic optical properties have been used as novel photoluminescence, Raman, and photoacoustic contrast agents for imaging of cells and animals. Further multidisciplinary explorations in this field may bring new opportunities in the realm of biomedicine.

Magnetically recoverable nanocatalysts.

Abstract: We gratefully acknowledge funding and support from King Abdullah University of Science and Technology (KAUST). Thanks are also due to the KAUST communication department for designing several images for this Review.