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Dendrimers have attracted much interest because of their unique structures and properties. 1 Their size, structure, and surface properties are highly controllable. Also, their interiors are capable of encapsulating small molecules. 2 Therefore, dendrimers are highly attractive materials for drug delivery applications. 3 Recently, efforts have been made to prepare dendrimers with poly(ethylene glycol) (PEG) chains at the chain ends. 4 Because the dendrimer moieties of PEG-attached dendrimers are covered with highly hydrophilic PEG chains, they may act as nanocapsules with a biocompatible surface. In a previous study, we successfully attached PEG chains to all of the chain ends of thirdand fourth-generation polyamidoamine (PAMAM) dendrimers and showed that these dendrimers have the ability to retain anticancer drugs. 4a In this study, we have attempted to provide the dendrimers with stimuli-sensitive properties because such properties are useful for site-specific or cytoplasmic drug delivery. Here, we report an effective strategy for the sensitization of dendrimers against oxidative or reductive environments using cysteine (Cys).PEG-attached PAMAM dendrimers with Cys residues were synthesized according to Scheme 1. The PAMAM G4 dendrimer, which has N-tert-butoxycarbonyl-S-acetamidomethylcysteine [Boc-Cys(Acm)] residues, was

Polymer structure of a block copolymer of poly(l‐lactic acid) (PLLA) and polystyrene (PS) is formed among a fibrous structure of PLLA inducing the gelation of PLLA in N,N‐dimethylformamide (DMF). The results of static and dynamic light scattering show the formation and growth of aggregates of the block copolymer (PLLA‐b‐PS) to form aggregates in DMF. The gels formed by the fibrous structure of PLLA in DMF are immersed in DMF solutions of PLLA‐b‐PS to allow the PLLA‐b‐PS chains to penetrate among the fibrous structure. The morphology of PLLA‐b‐PS in the gel is observed by field emission scanning electron microscopy. Viscoelastic measurements of the gel before and after the immersion indicate that the structure of the PLLA‐b‐PS elevates the flow temperature.

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