Summary: A novel thermosensitive amphiphilic copolymer (PCL‐g‐P(NIPAAm‐co‐HEMA)) comprised of hydrophobic PCL segments and hydrophilic P(NIPAAm‐co‐HEMA) segments was designed and synthesized. The structure of the copolymer was characterized by FT‐IR, 1H NMR and GPC analysis. The copolymer may self‐assemble into micelles in water and the resulting micelles demonstrated temperature sensitivity with a lower critical solution temperature (LCST) of 33 °C. The critical micellar concentration (CMC) obtained from surface tension measurements and the fluorescence method was around 30 mg · L−1. Transmission electron microscopy (TEM) showed that the micelles exhibit a nanospheric morphology within a narrow size range of 150–160 nm. A cytotoxicity study showed that the PCL‐g‐P(NIPAAm‐co‐HEMA) copolymer exhibits good biocompatibility. The controlled drug release of the resulting micelles was investigated and it was found that micelles loaded with prednisone acetate showed improved drug release behavior due to the special micellar structure.Self‐assembly of the PCL‐g‐P(NIPAAm‐co‐HEMA) copolymers.magnified imageSelf‐assembly of the PCL‐g‐P(NIPAAm‐co‐HEMA) copolymers.

Polymeric nanoparticles with unique properties are regarded as the most promising materials for biomedical applications including drug delivery and in vitro/in vivo imaging. Among them, stimulus-responsive polymeric nanoparticles, usually termed as "intelligent" nanoparticles, could undergo structure, shape, and property changes after being exposed to external signals including pH, temperature, magnetic field, and light, which could be used to modulate the macroscopical behavior of the nanoparticles. This paper reviews the recent progress in stimulus-responsive nanoparticles used for drug delivery and in vitro/in vivo imaging, with an emphasis on double/multiple stimulus-responsive systems and their biomedical applications.polymer, stimulus-responsive nanoparticles, drug carrier, cellular imaging

A polyethylene glycol–poly(ε-benzyloxycarbonyl- l -lysine) (PEG-SS-PLL) block copolymer based on a disulfide-linked, novel biodegradable catiomer bearing a PEG-sheddable shell was developed to avoid “PEG dilemma” in nanoparticle intracellular tracking of PEG-PLL where PEG was nondegradable. However, PEG-SS-PLL catiomers have not been used to deliver small interfering VEGF RNA (siVEGF) in antiangiogenesis gene therapy. In this study, we aimed to investigate whether this novel biodegradable catiomer can deliver siVEGF into cancer cells and at the same time have an antitumor effect in a xenograft mouse model. It was found that PEG-SS-PLL efficiently delivered siVEGF with negligible cytotoxicity, and significantly decreased the expression of VEGF at both the messenger-RNA and protein levels both in vitro and in vivo, and thus tumor growth was inhibited. Our findings demonstrated that PEG-SS-PLL/siVEGF could potentially be applied to antiangiogenesis gene therapy for hepatocellular carcinoma.