Safe and effective gene delivery is essential to the success of gene therapy. We synthesized and characterized a novel nonviral gene delivery system in which folate (FA) molecules were functioned as blockers on cationic polyrotaxanes (PR) composed of poly(ethylenimine) (PEI)(600)-grafted α-cyclodextrin rings linearized on polyethylene glycol to form FA-terminated PR-PEI(600) (FPP). The FA terminal caps of FPP target cell surfaces abundant in FA receptor (FR), a common feature of tumor cells. The structure of FPP was characterized by using (1)H nuclear magnetic resonance ((1)H NMR). The delivery particle was composed of chemically bonded PEG (4000), α-cyclodextrins (CD), and PEI (600 Da) at a molar ratio of 1:17:86.7, and the particle size and zeta potential of FPP/pDNA polyplexes were measured using dynamic light scattering. FPP/pDNA exhibited a lower cytotoxicity, strong specificity to FR, and high efficiency of delivering DNA to target cells in vitro and in vivo with the reporter genes. Furthermore, the FPP/DNA complex showed an enhanced antitumor effect in the nude mice compared with other delivery systems, such as PEI-25K. Together, these results suggest that FPP may be useful for gene therapy.
The residual stress distribution introduced by shot peening (SP) in the deformed surface layer of titanium matrix composite (TiB+TiC)/Ti-6Al-4V was investigated via three-dimensional (3D) finite element dynamic simulation and experimental validation. The program of ANSYS/LS-DYNA was utilized in the 3D finite element dynamic analysis of SP process, and the 3D homogeneous and inhomogeneous models were set up. The results showed that the compressive residual stresses (CRS) were introduced in the matrix, but the tensile residual stresses appeared in the reinforcements. The maximum CRS and tensile residual stress were -1511 and +1155MPa respectively, which revealed the higher yield strength of reinforcements. This type of stress distribution revealed the effect of reinforcements, keeping the adverse tensile stresses in the reinforcements and retarding the damage to the matrix during deformation. In terms of experiments, after SP, the residual stresses along the depth from the surface were measured using X-ray diffraction (XRD) method. The experimental results indicated that the CRS formed in the surface layer and the maximum appeared on the subsurface. The range of residual stresses found in experiments supported the simulated results, which verified the validity of 3D finite element dynamic analysis.
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