Finally, 24 h exposure to LRDNG did not affect the viability of either cell type at the dose studied (20 μg/ml). Flow cytometry and confocal microscopy indicated slow uptake of LRDNG in PMA-stimulated THP-1 cells, with only 41% of cells containing LRDNG after 24 h exposure. Although LysoTracker Green staining indicated a lysosomal fate for LRDNG, the mock drug cargo (HAF) diffused extensively inside the cell within 15 min. Epifluorescence microscopy confirmed rapid uptake of LRDNG by HUVEC. The LDNG (∼100 nm) were prepared with rhodamine-label dextran (LRDNG) via Maillard reaction followed by heat-gelation reaction and were loaded with a fluorescent probe, 5-hexadecanoylaminofluorescein (HAF), as a mock drug. In this work, we examine the potential of lysozyme-dextran nanogels (LDNG) as drug carriers in vitro using two cell lines: a model target tissue, human umbilical cord vein endothelial cells (HUVEC) and a model of the mononuclear phagocyte system (phorbol 12-myristate 13-acetate (PMA)-stimulated THP-1 cells). Nanogels (NG) hold great promise as a drug delivery platform. The new PVDF/SR/FKM TPV can be an idea potential alternative for expensive fluorosilicone rubbers in some applications.
The TPV exhibited good mechanical properties in which its tear strength was as high as 58kN.m-1. It was found that the tan δ value of core/shell bi-crosslinked TPV could be maintained at around 0.3 in range of 1-1000cpm. The crosslink density of SR-core and FKM-shell could be controlled to tailor the properties of the TPV. In the PVDF/FKM/SR (40/30/30) TPV, the size of core-shell particle was ~2μm, and the thickness of FKM shell was ~400nm. Results of TEM, SEM, EDX and FT-IR confirmed the formation of core-shell structure. The bi-crosslinked SR-core/FKM-shell structure effectively stabilized the blending morphology of TPV, avoiding the direct contact of PVDF and SR. Herein, we report a new method, core-shell dynamic vulcanization, to prepare a poly (vinylidene fluoride) (PVDF)-based TPV with crosslinking-controlled silicone rubber (SR)/fluororubber (FKM) core-shell particles. This study could provide more information for the design of TPVs with core-shell structure. Therefore, the mechanical properties improved with increasing FKM content especially, a remarkable improvement was observed when FKM/SR ratio was >1. When the FKM/SR ratio was 1, perfect core-shell structure was formed. The results showed that the FKM shell had more positive effect on interfacial-induced crystallization behavior than the SR core due to its better compatibility with PVDF. The effect of FKM-shell/SR-core ratio on morphology, crystallization, and mechanical properties of the ternary TPVs was studied.
Herein, these PVDF-based TPVs different FKM-shell thickness were prepared by changing FKM/SR ratios. However, the shell thickness on the properties has not been studied in detail. Recently, we have reported a novel core-shell dynamic vulcanization method to prepare poly(vinylidene fluoride) (PVDF)/fluororubber (FKM)/silicone rubber (SR) thermoplastic vulcanizates (TPVs) with cross-linked rubber core-shell particles.
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