Zhu Xinyuan

CO2-induced Crystallization of Isotactic Polypropylene by Annealing Near Its Melting Temperature

CO2-induced crystallization of isotactic polypropylene (iPP) by annealing had been studied using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). The iPP before annealed was in α-form and amorphous states. At lower temperatures by CO2 isothermal treatments, iPP chains crystallized from the amorphous phase and only one crystal form, i.e., α-form, was observed. At higher temperatures by CO2 isothermal treatments, both crystallization from the amorphous phase and thickening of existing crystal lamellae were observed. Moreover, light γ-form crystal appeared in the treated iPP. The crystalline lamellar thickness of iPP annealed at different CO2 pressures had been determined. Using the Gibbs–Thomson plot method, the equilibrium melting temperature was found to be 187.6°C.

Tracing drug release process with dual-modal hyperbranched polymer-gold nanoparticle complexes

Dual-modal surface enhanced Raman spectrum (SERS)-fluorescence polymer/metal hybrid complexes have been prepared for tracing drug release process in tumor cells. Firstly, the hyperbranched poly((S-(4-vinyl) benzyl S′-propyltrithiocarbonate)-co- (poly(ethylene glycol) methacrylate)) (HPVBEG) was synthesized via the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization and self-condensing vinyl polymerization (SCVP). Subsequently, the anticancer drug doxorubicin (DOX) was linked to HPVBEG via pH sensitive Schiff base bonds to form HPVBEG-g-DOX conjugates. Through aminolysis reaction, HPVBEG-g-DOX was coordinated with gold nanoparticles (GNP), resulting in the formation of HPVBEG-g-DOX/GNP complexes. In neutral condition, the HPVBEG-g-DOX/GNP complexes were stable, and DOX was bound to the surface of GNPs. Therefore, the SERS of DOX could be observed, while the fluorescence of DOX was quenched by GNPs. Under an acidic environment, DOX was released from the surface of GNPs with breakage of Schiff base bonds. Thus, the SERS signal of DOX was gradually reduced. Correspondingly, the fluorescence signal of DOX was enhanced. Through dual-modal SERS-fluorescence technique, the DOX delivery and release process was traced in tumor cells. Moreover, the viability of MCF-7 cells incubated with HPVBEG-g-DOX/GNP complexes was investigated by Cell Counting Kit-8 (CCK-8) assay. The experimental results showed that HPVBEG-g-DOX/GNP complexes had similar proliferation inhibition effect compared with free DOX. Definitely, the dual-modal SERS-fluorescence complexes for tracing drug delivery and release will have promising prospects on tumor diagnosis and therapy.