Lei Sun

Fabrication of autofluorescent porous silica nanoparticles for redox-responsive drug release

Porous silica nanoparticles were prepared by emulsion-condensation route. The silica nanoparticles with diameter of 50nm have both accessible center-radial large pore channels (19.9nm) and small pore size of 3.5nm. The hierarchical porous structure endows them large pore volume for loading drugs and sustained release property. The silica nanoparticles were further modified with glucose-oxidized glutathione. The formulated Schiff base and disulfide bonds render the silica nanoparticles auto-fluorescent and redox-responsive properties. The cleavage of disulfide bonds caused by reactive thiols facilitates aminomethylbenzoic acid (AMA) release. The release of drug leads to the loss of fluorescence, which would be used to monitor the drug delivery and carrier distribution.

Fabrication of silver nanoparticles embedded into polyvinyl alcohol (Ag/PVA) composite nanofibrous films through electrospinning for antibacterial and surface-enhanced Raman scattering (SERS) activities

Silver nanoparticle-embedded polyvinyl alcohol (PVA) nanofibers were prepared through electrospinning technique, using as antimicrobial agents and surface-enhanced Raman scattering (SERS) substrates. Ag nanoparticles (NPs) were synthesized in liquid phase, followed by evenly dispersing in PVA solution. After electrospinning of the mixed solution at room temperature, the PVA embedded with Ag NPs (Ag/PVA) composite nanofibers were obtained. The morphologies and structures of the as-synthesized Ag nanoparticles and Ag/PVA fibers were characterized by the techniques of transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Ag NPs have an average diameter of 13.8nm, were found to be uniformly dispersed in PVA nanofibers. The Ag/PVA nanofibers provided robust antibacterial activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) microorganisms. Its also found that Ag/PVA nanofibers make a significant contribution to the high sensitivity of SERS to 4-mercaptophenol (4-MPh) molecules.

Fabrication of SnO2/porous silica/polyethyleneimine nanoparticles for pH-responsive drug delivery.

To create novel nanocarriers for achieving excellent drug delivery performance, pH-responsive fluorescent porous silica (PS) nanocarriers were developed by encapsulating SnO2 nanoparticles and coating polyethyleneimine (PEI) layer. SnO2/porous silica (SnO2/PS) nanoparticles have an average diameter of 80nm and center-radial large pore channels. The large channels endow them high surface area with a Brunauer-Emmett-Teller (BET) area of 939m(2)g(-1). Aspirin was used as test drug to evaluate the releasing behavior of SnO2/porous silica/polyethyleneimine (SnO2/PS/PEI) nanoparticles. Results indicated that aspirin can be successfully incorporated into the SnO2/PS/PEI nanoparticles and the SnO2/PS/PEI nanoparticles displayed excellent pH-responsive release. The release rate in pH7.4 buffer is higher than that in pH5.5 buffer, which attributed to the PEI structure change in varied pH buffer. In addition, the SnO2/PS/PEI nanoparticles presented novel drug-dependent fluorescence, which could be used to trace the drug release.

Synthesis of poly acrylic acid modified silver nanoparticles and their antimicrobial activities.

Poly acrylic acid modified silver (Ag/PAA) nanoparticles (NPs) have been successfully synthesized in the aqueous solution by using tannic acid as a reductant. The structure, morphology and composition of Ag/PAA NPs were characterized by various techniques such as X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible absorption spectroscopy (UV-vis) and thermogravimetry analysis (TGA). The results show that PAA/Ag NPs have a quasi-ball shape with an average diameter of 10 nm and exhibit well crystalline, and the reaction conditions have some effect on products morphology and size distribution. In addition, the as-synthesized Ag/PAA NPs antimicrobial activities against Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) were evaluated by the methods of broth dilution, cup diffusion, optical density (OD600) and electron microscopy observation. The as-synthesized Ag/PAA NPs exhibit excellent antibacterial activity. The antimicrobial mechanism may be attributed to the damaging of bacterial cell membrane and causing leakage of cytoplasm.

Biofunctionalization of silica microspheres for protein separation.

Mercapto-silica (SiO2-SH) microspheres were prepared via direct hydrolysis of 3-mercaptopropyltrimethoxysilane (MPS) in a basic aqueous solution. The content of surface thiol group (SH) of SiO2-SH microspheres was measured by Ellmans reagent method and X-ray photoelectron spectroscopy (XPS) and the content of surface thiol group of SiO2-SH microspheres is strongly dependent on the reaction conditions. The thermal stability of SiO2-SH microspheres was evaluated by thermogravimetric (TG) analysis, which tended to reduce with the increase of content of surface thiol groups. SiO2-SH microspheres can be easily modified with reduced glutathione (GSH) to generate SiO2-GSH microspheres for the affinity separation of Glutathione S-transferase (GST). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed to examine the validity of the separation procedure. The results showed that SiO2-GSH microspheres were efficient in GST affinity separation from mixed proteins.

Preparation of AgBr@SiO2 core@shell hybrid nanoparticles and their bactericidal activity.

AgBr@SiO2 core@shell hybrid nanoparticles (NPs) were successfully prepared by sol-gel method. Their morphology and structure were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The hybrid NPs are predominantly spherical in shape, with an average diameter of 180-200 nm, and each NP contains one inorganic core. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the hybrid NPs were examined against Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli), respectively. Results indicated that the AgBr@SiO2 NPs had excellent antibacterial activity.

pH-responsive drug release and real-time fluorescence detection of porous silica nanoparticles

In this work, pH-sensitive dual-switch porous silica (pSiO2) nanoparticles (NPs) were constructed for drug delivery. Poly(acrylic acid) (PAA) was grafting onto the internal and external surfaces of amino groups functionalized porous silica (pSiO2-NH2) NPs by the amidation between the amino groups and the carboxyl groups of PAA for pH triggered drug release. The resultant pSiO2/PAA NPs have an average diameter of 50-60nm and high specific surface area (914m2·g-1). To improve the loading capacity, ZnO quantum dots (QDs) were used to block the partial pores of pSiO2/PAA and the loading capacity reached to 28% for methotrexate (MTX) model drug. The in vitro cellular cytotoxicity test and a hemolysis assay demonstrated that the pSiO2/PAA/ZnO NPs were highly biocompatible and suitable to utilize as drug carriers. The MTX-loaded pSiO2/PAA/ZnO NPs displayed more efficient cytotoxic to HepG2 cells than free MTX. The pSiO2/PAA/ZnO NPs displayed low premature, pH-responsive release and pH-dependent fluorescence. Moreover, pH-dependent fluorescence enables to trace MTX release behavior.

Selective binding and magnetic separation of histidine-tagged proteins using Fe3O4/Cu-apatite nanoparticles.

Hierarchical Fe3O4@Cu-apatite nanoparticles (NPs) were synthesized via a facile hydrothermal method. The Fe3O4 cores present spherical shape and have a mean diameter of 300nm, and the Cu-apatite shell with thickness of about 50nm is composed of a large number of sheets. Using the high affinity of Cu(2+) on the surface toward histidine tags, the Fe3O4@Cu-apatite NPs can be applied to enrich and magnetically separate histidine tagged (His-tagged) proteins directly from the mixture of lysed cells. Research results indicated that the Fe3O4@Cu-apatite NPs presented negligible nonspecific protein adsorption and high protein binding ability.

Electrospinning of Ag Nanowires/polyvinyl alcohol hybrid nanofibers for their antibacterial properties

In order to developing a sort of flexible fibrous mats with outstanding and durable antibacterial activates, silver nanowires incorporated into polyvinyl alcohol (PVA) nanofibers were fabricated by electrospun method. Uniform Ag nanowires (NWs) were synthesized through a template-free method of solvothermal combined with polyol process, and then, they were dispersed in PVA solution. At last, Ag NWs embedded in PVA (Ag NWs/PVA) hybrid nanofibrous films were gained by electrospun of the mixed solution. The antibacterial activity of Ag NWs/PVA nanofibers against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was investigated by the methods of absorption and turbidity. Ag NWs with a mean diameter of 86nm were demonstrated to be uniformly incorporated into PVA nanofibers, forming a core-sheath nanocable structure. The as-prepared flexible and free-standing Ag NWs/PVA nanofibrous films show outstanding antimicrobial activities against both E. coli and S. aureus. Its found that both matrix polymer of PVA and enrichment of active {111} facets present in Ag NWs are favorable for the antibacterial performance.

Synthesis and antibacterial activity of Ag/CeO2 hybrid architectures

AbstractFlower-like ceria (CeO2) architectures consisting of well aligned nanosheets were first synthesized by a glycol solvothermal method. The size of CeO2 architectures is about 5u2009μm in width and 10u2009μm in length, with the nanosheets thickness below 100u2009nm. Subsequently, the adsorbed Ag ions on the surface of CeO2 were in situ reduced to form Ag nanoparticles (NPs), leading to the fabrication of Ag/CeO2 hybrid architectures (HAs). The formed Ag NPs with sizes of 20–40u2009nm were uniformly loaded on the surface of the CeO2 sheets. The antibacterial properties of Ag/CeO2 HAs against Gram-negative E. coli and Gram-positive S. aureus were evaluated by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and a filter paper inhibition zone method. The results demonstrated that Ag/CeO2 HAs displayed excellent antibacterial activity toward S. aureus and E. coli, which were attributed to the synergistic antibacterial effect between Ag NPs and CeO2 in HAs. Here, CeO2 nanoflowers as a new substrate could restrict Ag NPs aggregations and improve their antibacterial activities. Therefore, the resulted Ag/CeO2 HAs would be considered as a promising antibacterial agent.n HighlightsFlower-like Ag/CeO2 hybrid architectures (HAs) were successfully fabricated.Ag/CeO2 HAs displayed excellent antibacterial activity towards S. aureus and E. coli.The improved antibacterial performance of Ag/CeO2 HAs was attributed to the synergistic effect between Ag NPs and CeO2.