Zhifei Wang

Peroxidase-like activity of mesoporous silica encapsulated Pt nanoparticle and its application in colorimetric immunoassay

Nanomaterial-based artificial enzymes have received great attention in recent year due to their potential application in immunoassay techniques. However, such potential is usually limited by poor dispersion stability or low catalytic activity induced by the capping agent essentially required in the synthesis. In an attempt to address these challenges, here, we studied the novel Pt nanoparticles (NPs) based peroxidase-like mimic by encapsulating Pt NP in mesoporous silica (Pt@mSiO2 NPs). Compared with other nanomaterial-based artificial enzymes, the obtained Pt@mSiO2 NPs not only exhibit high peroxidase-like activity but also have good dispersion stability in buffer saline solution when grafted with spacer PEG. Results show that when the thickness of silica shell is about 9 nm the resulting Pt@mSiO2 NPs exhibit the catalytic activity similar to that of Pt NPs, which is approximately 26 times higher than that of Fe3O4 NPs (in terms of Kcat for H2O2). Due to the protection of silica shell, the subsequent surface modification with antibody has little effect on their catalytic activity. The analytical performance of this system in detecting hCG shows that after 5 min incubation the limit of detection can reach 10 ng mL(-1) and dynamic linear working range is 5-200 ng mL(-1). Our findings pave the way for design and development of novel artificial enzyme labeling.

Fluorescent artificial enzyme-linked immunoassay system based on Pd/C nanocatalyst and fluorescent chemodosimeter.

Artificial enzyme mimics have recently attracted considerable interest because they possess many advantages compared with natural enzymes, such as low cost of preparation and high stability. Herein, we present a novel fluorescent artificial enzyme-linked immunoassay strategy by utilizing Pd/C nanocatalyst as the enzyme mimic and bis-allyloxycarbonyl rhodamine 110 (BI-Rho 110) as the substrate, and the amplification procedure is based on the palladium-catalyzed Tsuji-Trost reaction. Pd/C nanocatalyst with the average size of 150 nm was prepared by the impregnation-reduction method, and high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses reveal that Pd clusters with an average size of about 1 nm are dispersed uniformly on each carbon nanospheres surface. Kinetic studies show that this reaction follows Michaelis-Menten kinetics and the fluorescence intensity is proportional to the concentration of Pd/C nanocatalyst under certain conditions. The turnover number of Pd/C nanocatalyst reaches up to 3.3 × 10(7) (h(-1)). The analytical performance of this system in detecting hCG shows that after a 24 h incubation the sensitivity limit can reach 0.1 ng/mL and the dynamic linear working range is 1-10 ng/mL. Our findings pave the way to use Pd-catalyzed reaction for design and development of novel analytical methods.

Effects of template removal on both morphology of mesoporous silica-coated gold nanorod and its biomedical application

Mesoporous silica-coated Au nanorods (Aurod@SiO2) have recently attracted considerable interest in nanomedicine, and the template removal procedure is crucial for the preparation of such hybrid nanostructure. Herein, two kinds of typical extraction solvents, i.e., NH4NO3–CH3OH and HCl–CH3OH, were separately used to extract the surfactant cetyltrimethylammonium bromide (CTAB) from the obtained Aurod@SiO2. The results show that CTAB molecules could be completely removed from the pores of Aurod@SiO2 without damaging the internal Au nanorod by NH4NO3–CH3OH, while Aurod@SiO2 treated with HCl–CH3OH suffered from both poor extraction efficiency and the shape transformation of Au nanorod due to selective etching in the presence of oxygen. In addition, the consequent drug loading experiment shows that Aurod@SiO2 extracted by NH4NO3–CH3OH possesses a larger drug loading capacity with a loading efficiency of 82.5%. Furthermore, the in vitro photo-thermal therapy experiment shows that Aurod@SiO2 extracted by NH4NO3–CH3OH is more efficient in killing the YCC-2 gastric cancer cells as compared with that extracted by HCl–CH3OH.

A FITC-doped silica coated gold nanocomposite for both in vivo X-ray CT and fluorescence dual modal imaging

Dual-modal imaging contrast agents with unique X-ray computed tomography (CT) and optical imaging capabilities have attracted much attention in recent years. Herein, the new silica hybrid nanocomposites containing Au nanoparticles and FITC dyes (FITC–Au@SiO2) were investigated as this kind of contrast agent. TEM characterization showed that the as-synthesized FITC–Au@SiO2 nanoprobes were uniform in morphology with the average size of 90 nm. After the PEGylation, the obtained FITC–Au@SiO2@PEG exhibited good dispersion stability under different conditions. The MTT assay suggested that FITC–Au@SiO2@PEG didnt show appreciable toxicity toward KB cells even at high concentration of up to 1000 μg mL−1. In addition, it was found that FITC–Au@SiO2@PEG could cross the cell membrane and enter into the cytoplasm during the incubation with cells. In vivo dual modal optical/CT imaging of C57BL/6J mice uncovered that within 2 h post-injection FITC–Au@SiO2@PEG nanoprobes preferred to accumulate in the liver and were gradually cleared through the enterohepatic circulation system, which could bring novel opportunities to the next generation of dual-modality contrast agents.

PEGylated denatured bovine serum albumin modified water-soluble inorganic nanocrystals as multifunctional drug delivery platforms†

A novel approach of using denatured bovine serum albumin (dBSA) to modify hydrophobic nanocrystals is reported. The dBSA layer outside of nanocrystals can adsorb water insoluble drugs excellently via hydrophobic interactions. Further PEGylation of the engineered nanocrystals greatly improves their aqueous stability. PEGylated dBSA modified upconversion nanoparticles, as a model for construction of integrating imaging and drug delivery platform, were also studied. The results demonstrated the modified upconversion nanoparticles not only maintain their unique up-conversion luminescence characters but also exhibit higher drug loading ability. Thus, such novel PEGylated dBSA modification approach expands the range of biological applications of inorganic nanocrystals.

Near-infrared light-induced dissociation of zeolitic imidazole framework-8 (ZIF-8) with encapsulated CuS nanoparticles and their application as a therapeutic nanoplatform

Incorporation of CuS nanoparticles into the framework of ZIF-8 provides a chance to integrate near-infrared (NIR) light/low pH triggered release and chemo-photothermal therapy into one system. For the first time, we observed that the framework of ZIF-8 could be disintegrated at pH 7.4 under NIR laser irradiation.

Nuclease-responsive DNA–PEI hollow microcapsules for bio-stimuli controlled release

In this paper, a DNA-PEI microcapsule with novel nuclease-responsive controlled release properties was demonstrated. This microcapsule was constructed by the self-assembly of native DNA and PEI, and can work as a dual carrier for both DNA in the capsule shell and drugs inside the capsule. The controlled release behavior of the model drug BSA-FITC was studied using fluorescence microscopy and UV spectroscopy, and the results show that the synergetic controlled release can be triggered very well by a bio-stimulus, DNA nuclease recognition capsule decomposition, as well as the pH value and salt concentration. The therapeutic effects of the drug are enhanced due to the bio-stimuli responsive properties and the synergetic release of DNA and the drug together.

Coating Carbon Nanosphere with Patchy Gold for Production of Highly Efficient Photothermal Agent

Gold- or carbon-based photothermal therapy (PTT) agents have shown encouraging therapeutic effects of PTT in the near-infrared region (NIR) in many preclinical animal experiments. It is expected that gold/carbon hybrid nanomaterial will possess combinational NIR light absorption and can achieve further improvement in photothermal conversion efficiency. In this work, we design and construct a novel PTT agent by coating a carbon nanosphere with patchy gold. To synthesize this composite particle with Janus structure, a new versatile approach based on a facile adsorption-reduction method was presented. Different from the conventional fabrication procedures, the formation of patchy gold in this approach is mainly a thermodynamics-driven spontaneous process. The results show that when compared with the conventional PTT agent gold nanorod the obtained nanocomposites not only have higher photothermal conversion efficiency but also perform more thermally stable. On the basis of these outstanding photothermal effects, the in vitro and in vivo photothermal performances in a MCF-7 cells (human breast adenocarcinoma cell line) and mice were investigated separately. Additionally, to further illustrate the advantage of this asymmetric structure, their potential was explored by selective surface functionalization, taking advantage of the affinity of both patchy gold and carbon domain to different functional molecules. These results suggest that this new hybrid nanomaterial can be used as an effective PTT agent for cancer treatment in the future.

Wet Chemical Synthesis of Silica Nanosheets via Ethyl Acetate-Mediated Hydrolysis of Silica Precursors and Their Applications

Freestanding and transferable silica nanosheets with thicknesses of ≈5-7xa0nm are prepared via ethyl acetate-mediated hydrolysis of silica precursors in aqueous solution. The resulting silica nanosheets have shown many potential applications. For example, they can be used as the support film on the finer mesh grids for transmission electron microscopy imaging and as the precursor for the synthesis of silicon nanosheets.

Threading different metal nanomaterials on natural PhiX174 DNA to assemble a necklace

Multiple nanomaterials were assembled on a circular DNA to form a necklace. AuNPs were first attached to natural PhiX174 ss-DNA, and then a single-circle PCR was adopted to immobilize the attachments. The structures of the assemblies were confirmed by TEM imaging and UV-vis spectrometry. In this way, various types and shapes of nanomaterials were assembled on the DNA, such as palladium nanocubes and gold nanorods.