pH and NIR responsive polydopamine-doped dendritic silica carriers for pesticide delivery.

The stimuli-responsive pesticide delivery system provides a powerful strategy for enhancing the effective utilization of pesticides and reducing environmental pollution. Here, we prepared a new polydopamine doped dendritic silica (SiO2/PDA) nanocarriers for pesticide delivery. The SiO2/PDA nanocarriers present uniform spheres with an average diameter of 250 nm and carry center-radial inner pores. After loading dinotefuran (DNF) insecticide, polyethyleneimine (PEI) was used to cap the loaded-pesticide pores. The resulting SiO2/PDA@PEI displays high photothermal conversion effect (η = 35.1 %) and pH and near infrared (NIR) light-responsive release behavior. Meanwhile, the SiO2/PDA and SiO2/PDA@PEI carriers displayed high adhesion and wettability to leaves, and the photostability of DNF encapsulated in SiO2/PDA@PEI was improved by nearly 10 times greater than for free DNF. Importantly, the SiO2/PDA carriers possessed a benign biocompatibility on Escherichia coli (E. coli), seed and cells. Therefore, this work provides a promising approach to improve the utilization of pesticide.

Polydopamine-encapsulated cap-like mesoporous silica based delivery system for responsive pesticide release and high retention.

Nanopesticides formulation has been applied in modern agriculture, but the effective deposition of pesticides on plant surfaces is still a critical challenge. Here, we developed a cap-like mesoporous silica (C-mSiO2) carrier for pesticide delivery. The C-mSiO2 carriers with surface amino groups present uniform cap-like shape and have an mean diameter of 300 nm and width of 100 nm. This structure would reduce the rolling and bouncing of carriers on plant leaves, leading to improving the foliage deposition and retention. After loading dinotefuran (DIN), polydopamine (PDA) was used to encapsulate the pesticide (DIN@C-mSiO2@PDA). The C-mSiO2 carriers exhibit high drug loading efficiency (24.7%) and benign biocompatibility on bacteria and seed. Except for pH/NIR response release, the DIN@C-mSiO2@PDA exhibited excellent photostability under UV irradiation. Moreover, the insecticidal activity of DIN@C-mSiO2@PDA was comparable to that of pure DIN and DIN commercial suspension (CS-DIN). This carrier system has the potential for improving the foliage retention and utilization of pesticides.

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. It's found that both matrix polymer of PVA and enrichment of active {111} facets present in Ag NWs are favorable for the antibacterial performance.

Highly water-dispersible silver sulfadiazine decorated with polyvinyl pyrrolidone and its antibacterial activities.

Highly water-dispersible silver sulfadiazine (SSD) was prepared by liquid phase method with polyvinyl pyrrolidone (PVP) as a surface modification agent. The structure and morphology of the PVP-modified silver sulfadiazine (P-SSD) were investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier-transform infrared (FT-IR) spectrometry. The produced particles are ginkgo leaf-like architecture with the sizes of micron-nanometer. Due to hydrophilic PVP decorated on the surface, the P-SSD has excellent dispersion in water over a period of 24h, which is obviously stable by comparison to that of the commercial silver sulfadiazine (C-SSD). In addition, the P-SSD exhibits good antibacterial activities against Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus).

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. It's 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 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 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.

Controlled synthesis of Ag nanoparticles with different morphologies and their antibacterial properties.

In this paper, Ag triangle nanoplates and nanospheres were synthesized by liquid chemical reduction method in the presence of seeds, with L-ascorbic acid as the reductant and polyvinyl pyrrolidone (PVP) as the surface modification agent, respectively. Characterizations of the particles were conducted by various techniques such as X-ray powder diffraction, transmission electron microscopy, ultraviolet-visible absorption spectroscopy, Fourier transformation infrared spectrometry, and thermal analysis. The antibacterial properties of Ag nanoparticles against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were investigated by disk diffusion and broth dilution methods. The results indicate that Ag nanospheres exhibit better antibacterial properties than that of triangle nanoplates.