Yanbao Zhao

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.

Synthesis of water-soluble Cu/PAA composite flowers and their antibacterial activities.

Water-soluble copper/polyacrylic acid (Cu/PAA) composites were synthesized by a facile solution-phase reduction route. The Cu/PAA composites presented flower-like architecture, consisting of several intercrossing sheets, and reaction conditions had an important effect on their morphologies. Their antibacterial activity towards the bacterial strains such as Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) were evaluated by the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC), cup diffusion method and optical density (OD600). Results indicated that Cu/PAA flower is selective in its antibacterial action. It displays more effective antibacterial activity against B. subtilis than other three stains, and better bactericidal activity against S. aureus, E. coli and P. aeruginosa than B. subtilis. There is no bactericidal ability against B. subtilis in the tested concentration range, which indicates that B. subtilis may be a copper-tolerant bacterium.

Synthesis and Tribology Properties of Stearate-Coated Ag Nanoparticles

Stearate-coated silver nanoparticles were synthesized in water solutions through the chemical reduction method. The morphology, structure, and thermal properties of the coated Ag nanoparticles were investigated with transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential thermal analysis. Their tribological properties were evaluated on a four-ball test machine. The rubbed surface was investigated by scanning electron microscopy. The results show that the stearate-coated Ag nanoparticles have an average particle size in the range of 8-10 nm, and the coated Ag nanoparticles as oil additives in liquid paraffin exhibit excellent tribological properties.

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.

Iminodiacetic acid functionalized porous hydroxyapatite nanoparticles for capturing histidine-tagged proteins

A simple strategy has been developed to synthesize hydroxyapatite (HAP) nanoparticles (NPs) in a simulated body fluid (SBF). The HAP NPs have an average diameter of 50nm and present porous structure. By taking advantage of surface hydroxyl groups, the HAP NPs are further modified with iminodiacetic acid (IDA), followed by chelating Ni(2+) ions. The HAP/IDA-Ni(2+) NPs as novel adsorbent can capture directly histidine-tagged (His-tagged) proteins from the mixture of lysed cells without sample pretreatment. Results indicated that the HAP/IDA-Ni(2+) NPs present negligible nonspecific adsorption and high protein binding ability, and their specificity and affinity toward His-tagged proteins can remain after 5 times of recycling. The HAP/IDA-Ni(2+) NPs are especially suitable for purification of His-tagged proteins with low molecule weight.

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.