RSC Adv. 4 (2014)

UV light-induced surface-initiated atom-transfer radical polymerization (ATRP) was reported. This method uses TiO 2 nanoparticles as photoactive materials to reduce Cu(II)/L to a Cu(I)/L complex under UV irradiation by a one-electron transfer process for ATRP with multiple usage of monomer solutions. The growth of polymer brushes can be manipulated by either varying the content of photoactive materials or regulating the irradiation intensity, thereby yielding polymer brushes with controllable thickness, composition, and architecture. P olymer brushes produced by controlled or living surfaceinitiated radical polymerization 1,2 provide a superior route for surface functionalization, such as creation of smart surfaces, 3−5 antibiofouling materials, 6,7 and lubrication. 8 Compared with various controlled radical polymerization techniques 9 and organic polymer synthesis strategies, 10 atomtransfer radical polymerization (ATRP) 11−14 facilitates the construction of diverse polymer assemblies. 15−18 Generally, a Cu(I)−ligand complex and high monomer concentration are necessary to maximize polymer growth, 19−21 which highly relies on the reversible redox activation/deactivation of Cu(I)/ Cu(II). Control over the Cu(I)/Cu(II) ratio is important to obtain fast a polymerization rate while prolonging the lifetime of propagation chains. 22,23 The scope of ATRP has been expanded to external stimulusinduced polymerizations, 24,25 such as in electrochemically mediated ATRP (eATRP) for controlling polymerization by the electrically one-electron reduction of air-stable Cu(II). 26,27 We extended the eATRP technique to surface-initiated eATRP for controllable fabrication of surface-attached polymer brushes. 28 External visible light-stimulated living radical polymerization has been proposed through the excited Ir(III) species to reduce an alkyl bromide initiator for alkyl radical formation to initiate polymerization, 29,30 click reaction, 31,32 light-mediated atom-transfer radical addition, 33 and photoiniferter-mediated surface attached polymers formation. 34 The key to external stimulus-induced polymerization is continuous in situ generation of the activator catalyst. In this report, we propose a novel approach to achieve surface-initiated ATRP with multiple usage of monomer solutions, wherein the polymerization activators, Cu(I)−ligand, can be continuously generated from a photochemical reduction process by the excited electrons under ultraviolet (UV) illumination that uses the TiO 2 nanoparticle as the photosensitive material. Scheme 1(b) displays the mechanism of UV light-induced ATRP. A commercially available TiO 2 nanoparticle, P25, was

This review starts with a brief introduction to TiO 2 nanotubes (NTs), and then discusses in more detail how to optimize the structure of TiO 2 NTs for the fabrication of highly efficient solar cells, including the controllable fabrication of perfectly aligned TiO 2 NTs, optimizing the tube parameters, strategies of sensitization, improvement of the interface adhesion in polymer/TiO 2 solar cells and how to make devices flexible. Some key challenges and perspectives for future research are also tentatively discussed.

Brushing up on polymers: A difference in electrochemical potential allows surface‐initiated atom‐transfer radical polymerization on a sandwiched metal substrate using microliter volumes. CuI activators are continuously generated and diffuse to the initiator‐modified substrate (see scheme), while CuII deactivators maintain polymerization. Polymer‐brush gradients of SPMA and complex shapes were produced using this method.

The objective was to examine whether muscle structural capacity for O2 flux (i.e., capillary-to-fiber surface ratio) relative to fiber mitochondrial volume deteriorates with the muscle atrophy of aging in predominantly slow-(soleus, S) and fast-twitch (extensor digitorum longus, EDL) muscles of old (24 mo) and very old (35 mo) F344BN rats compared with adult (12 mo old). Wet muscle mass decreased 29% (196 Ϯ 4 to 139 Ϯ 5 mg) in S and 22% (192 Ϯ 3 to 150 Ϯ 3 mg) in EDL between 12 and 35 mo of age, without decline in body mass. Capillary density increased 65% (1,387 Ϯ 54 to 2,291 Ϯ 238 mm Ϫ2 ) in S and 130% (964 Ϯ 95 to 2,216 Ϯ 311 mm Ϫ2 ) in EDL, because of the muscle fiber atrophy, whereas capillary per fiber number remained unchanged. Altered capillary geometry, i.e., lesser contribution of tortuosity and branching to capillary length, was found in S at 35 compared with 12 and 24 mo, and not in EDL. Accounting for capillary geometry revealed 55% (1,776 Ϯ 78 to 2,750 Ϯ 271 mm Ϫ2 ) and 113% (1,194 Ϯ 112 to 2,540 Ϯ 343 mm Ϫ2 ) increases in capillary length-to-fiber volume ratio between 12 and 35 mo of age in S and EDL, respectively. Fiber mitochondrial volume density was unchanged over the same period, causing mitochondrial volume per micrometer fiber length to decrease in proportion to the fiber atrophy in both muscles. As a result of the smaller fiber mitochondrial volume in the face of the unchanged capillary-to-fiber number ratio, capillaryto-fiber surface ratio relative to fiber mitochondrial volume not only did not deteriorate, but in fact increased twofold in both muscles between 12 and 35 mo of age, independent of their different fiber type. capillary anisotropy; morphometry; ultrastructure; sarcopenia THE REDUCTION IN MUSCLE MAXIMAL capacity for aerobic work with aging is well known, and previous studies have shown alterations in both convective and diffusive components of O 2 transport in muscles. For example, reduced leg blood flow and increased leg O 2 extraction were found in older (63 Ϯ 2 yr old) compared with younger (27 Ϯ 1 yr old) endurance-trained men during submaximal exercise (42), and blood flow redistribution from highly oxidative to highly glycolytic muscles was recently demonstrated in the hindlimb of old (27-29 mo old) compared with young (6 -8 mo old) F344BN rats during submaximal exercise (37). Using an in situ pump-perfused hindlimb preparation to match convective O 2 delivery and eliminate age-related decline in blood flow, Hepple et al. (15) found a 22% decrease in the mass-specific O 2 uptake of the distal hindlimb in late middle aged (28 -39 mo) compared with young adult (8 mo) F344BN rats. In contrast, structural data on muscle capacity for O 2 transfer from capillary to fiber mitochondria have been contradictory. Human and/or animal studies have shown decreased (5, 12, 14, 38), unchanged (3, 4, 36), or even increased (8, 19, 36) capillary-to-fiber number ratios in skeletal muscles with aging. Part of the discrepancies have been attributed to the fact that differences in activit...

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This review provides substantial evidences of apoptosis pathways in cancer cells and the apoptotic proteins modulated by active natural products, which may help to gain a comprehensive understanding for the development of natural drugs for better cancer treatment.