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.

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.