Smart nanocarriers are of particular interest as nanoscale vehicles of imaging and therapeutic agents in the field of theranostics. Herein, we report dually pH/reduction-responsive terpolymeric vesicles with monodispersive size distribution, which are constructed by assembling acetal- and disulfide-functionalized star terpolymer with near-infrared cyanine dye and anticancer drug. The vesicular nanostructure exhibits multiple theranostic features including on-demand drug releases responding to pH/reduction stimuli, enhanced photothermal conversion efficiency of cyanine dye, and efficient drug translocation from lysosomes to cytoplasma, as well as preferable cellular uptakes and biodistribution. These multiple theranostic features result in ultrahigh-contrast fluorescence imaging and thermo-chemotherapy-synergized tumor ablation. The dually stimuli-responsive vesicles represent a versatile theranostic approach for enhanced cancer imaging and therapy.

b S Supporting Information ' INTRODUCTIONSynthesis and properties of functional branched and star polymers have attracted much attention since these polymers usually possess unique physicochemical properties and wide applications originating from a large number of chain ends per molecule and their branched chain architectures. Generally, hyperbranched polymers can be synthesized by step-growth polymerization via polycondensation or addition polymerization of multifunctional monomers, 3,4,30-32 copolymerization of conventional monomers via self-condensing vinyl polymerization (SCVP), 33-37 or copolymerization of vinyl monomers in the presence of multifunctional vinyl comonomers. 38,39 "Living"/ controlled radical polymerization approaches such as inifertermediated polymerization, 40 nitroxide-mediated polymerization, 41 atom transfer radical polymerization, 42-44 and reversible addition-fragmentation chain transfer (RAFT) polymerization [45][46][47][48][49][50][51][52][53] have been efficiently used to synthesize a variety of hyperbranched and star polymers with controlled compositions and variable functionality. Among them, RAFT polymerization is a facile and versatile approach to synthesize hyperbranched and star polymers due to its many advantages such as relatively mild reactions, wide range of monomers, tolerance of various functionalities, and lack of metal catalyst. A range of hyperbranched polymers have been achieved by RAFT polymerization in the presence of divinyl comonomers, 38,39 from a polymer backbone with pendant xanthate groups, 54 or with AB* styryl or acryloyl chain transfer agents. 55-58 Until now, the types of hyperbranched polymers obtained via RAFT process were relatively limited, and the feed ratio of vinyl monomer to chain transfer agent was usually higher than 10. In particular, the copolymerization behavior of conventional monomer with polymerizable RAFT agent has not been thoroughly investigated. It is therefore of great interest to study in depth the dependence of copolymer composition and degree of branching (DB) of hyperbranched copolymers on reaction conditions during RAFT polymerization.Star polymers, on the other hand, have been well-studied. They can be synthesized by approaches such as "arm first", 59-63 "core first", 64-67 and their combination. [68][69][70][71] The arm first approach involves the synthesis of prefabricated arms, usually through "living"/controlled polymerization, followed by reaction with a multifunctional core reagent, which is easily performed and can also afford target star polymers with low polydispersity. The potential drawback of arm first method is that the arm ABSTRACT: Facile synthesis of hyperbranched and star polymers on the basis of S-(4-vinyl)benzyl S 0 -propyltrithiocarbonate (VBPT) was described. RAFT copolymerization of VBPT with vinyl monomers such as methyl methacrylates (MMA), styrene (St), methyl acrylate (MA), and tert-butyl acrylate (tBA) afforded hyperbranched copolymers with variable branch length and degree of branching. Hyperbranched ...

Photoconversion tunability of fluorophore dye is of great interest in cancer nanomedicine such as fluorescence imaging, photodynamic therapy (PDT), and photothermal therapy (PTT). Herein, this paper reports wavelength-dependent photoconversional polymeric vesicles of boron dipyrromethene (Bodipy) fluorophore for either PDT under 660 nm irradiation or PTT under 785 nm irradiation. After being assembled within polymeric vesicles at a high drug loading, Bodipy molecules aggregate in the conformations of both J-type and H-type, thereby causing red-shifted absorption into near-infrared region, ultralow radiative transition, and ideal resistance to photobleaching. Such vesicles further possess enhanced blood circulation, preferable tumor accumulation, as well as superior cell uptake as compared to free Bodipy. In particular, the vesicles mainly generate abundant intracellular singlet oxygen for PDT treatment under 660 nm irradiation, while they primarily produce a potent hyperthermia for PTT with tumor ablation through singlet oxygen-synergized photothermal necrosis under 785 nm irradiation. This approach provides a facile and general strategy to tune photoconversion characteristics of fluorophore dyes for wavelength-dependent photoinduced cancer therapy.

In this study, the Z supported reversible addition−fragmentation chain transfer (RAFT) graft polymerization to prepare silica-polymer hybrids was investigated. Two chain transfer agents (CTAs), S-benzyl S‘-trimethoxysilylpropyltrithiocarbonate and S-methoxycarbonylphenylmethyl S‘-trimethoxysilylpropyltrithiocarbonate, were synthesized and covalently attached to the surface of fumed silica. The resultant silica supported CTAs were used to mediate RAFT polymerization of vinyl monomers such as methyl acrylate, butyl acrylate, N,N-dimethylacrylamide, N-isopropylacrylamide, methyl methacrylate, and styrene in the presence of a free CTA to synthesize polymer grafted silica particles. Effects of CTA loadings on solid supports, types of free CTAs, and reaction media on graft polymerization were investigated in detail. Under optimal conditions such as using 2-(2-cyanopropyl)dithiobenzoate as a free CTA and controlling the polymerization at a low conversion (typically less than 40%), well-defined polymeric chains with polydispersity indices less than 1.2 and chain lengths similar to those of free polymers could be successfully grafted onto the surface of fumed silica, and relatively high grafting ratios could be achieved, as is evident from GPC, FT-IR, and TGA analyses. As compared with polymerization in toluene, RAFT graft polymerization of methyl acrylate in methanol could afford longer grafted chain lengths and significantly increased grafting efficiency at identical conditions, suggesting the potential effects of reaction media on graft polymerization.

Star-shaped polylactide was synthesized by bulk polymerization of lactide with poly(amidoamine) (PAMAM) dendrimer as initiator, which was marked as PAMAM-g-PLA for simplicity. The nonlinear architecture of PAMAM-g-PLA was confirmed by gel permeation chromatograph, nuclear magnetic resonance, and differential scanning calorimetry analysis. Unlike the linear polylactide (PLA) with similar molecular weight, PAMAM-g-PLA had a higher hydrophilicity and a faster degradation rate because of shortened polymer chains and increased polar terminal endgroups due to its branch structure. The highly branched structure significantly accelerated the release of water-soluble bovine serum albumin from PAMAM-g-PLA microspheres, whereas the linear PLA with similar molecular weight exhibited an initial time lag release. This star polymer may have potential applications for hydrophilic drug delivery in tissue engineering, including growth factor and antibodies to induce tissue regeneration, by adjusting the chain lengths of PLA branches.