Preparation, Characterization and Antifungal Properties of Chitosan-Silver Nanoparticles Synergize Fungicide Against Pyricularia oryzae.

Rice (Oryza sativa L.) is one of the major staple food crops of nearly two-third of the world's population. However, rice blast caused by fungus Pyricularia oryzae is generally considered the most serious disease of cultivated rice worldwide due to its extensive distribution and destructiveness under favourable climatic conditions. In this report, the combination between chitosan (CS) and silver (Ag), Ag@CS, was introduced for antifungal activity against Pyricularia oryzae extracted from blast-infected leaves. In detail, Ag@CS nanoparticles (NPs) were first synthesized and further mixed with Trihexad 700 WP (Tri), Ag@CS-Tri, against the fungus by agar diffusion method. The prepared Ag@CS-Tri NPs were characterized by Fourier transform infrared (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). In aqueous condition, Ag@CS-Tri NPs were successfully prepared and existed as spherical NPs with particle size of 17.26 ± 0.89 nm, which is an ideal size for their uptake into plant cells, indicating that the size of their parentally Ag@CS NPs is small enough to combine Tri, and their diameter is large enough to effectively penetrate the cellular membrane and kill fungi. More importantly, the antifungal property of Ag@CS-Tri NPs was significantly increased with inhibition zone around 25 nm compared with only around 12 nm of Ag@CS at the same concentration of Ag (2 ppm) and CS (4000 ppm). These results demonstrated that the synergistic effect of Tri and Ag@CS NPs can be a potential candidate with high antifungal activity for the use of antibiotics in agriculture.

Low systemic toxicity nanocarriers fabricated from heparin-mPEG and PAMAM dendrimers for controlled drug release.

In this report, poly(amide amine) (PAMAM) dendrimer and Heparin-grafted-monomethoxy polyethylene glycol (HEP-mPEG) were synthesized and characterized. In aqueous solution, the generation 4 PAMAM dendrimers (G4.0-PAMAM) existed as nanoparticles with particle size of 5.63nm. However, after electrostatic complexation with HEP-mPEG to form a core@shell structure G4.0-PAMAM@HEP-mPEG, the size of nanoparticles was significantly increased (73.82nm). The G4.0-PAMAM@HEP-mPEG nanoparticles showed their ability to effectively encapsulate doxorubicin (DOX) for prolonged and controlled release. The cytocompatibility of G4.0-PAMAM@HEP-mPEG nanocarriers was significantly increased compared with its parentally G4.0-PAMAM dendrimer in both mouse fibroblast NIH3T3 and the human tumor HeLa cell lines. DOX was effectively encapsulated into G4.0-PAMAM@HEP-mPEG nanoparticles to form DOX-loaded nanocarriers (DOX/G4.0-PAMAM@HEP-mPEG) with high loading efficiency (73.2%). The release of DOX from DOX/G4.0-PAMAM@HEP-mPEG nanocarriers was controlled and prolonged up to 96h compared with less than 24h from their parentally G4.0-PAMAM nanocarriers. Importantly, the released DOX retained its bioactivity by inhibiting the proliferation of monolayer-cultured cancer HeLa cells with the same degree of fresh DOX. This prepared G4.0-PAMAM@HEP-mPEG nanocarrier can be a potential candidate for drug delivery systems with high loading capacity and low systemic toxicity in cancer therapy.