Dendritic nanoreactor

M. Ooe, M. Murata, T. Mizugaki, K. Ebitani, and K. Kaneda, Dendritic nanoreactors encapsulating Pd particles for substrate-specific hydrogenation of olefins. Nano Lett. 2,999-1002 (2002). 

Yeung, L.K. and Crooks, R.M. (2001) Heck heterocoupling within a dendritic nanoreactor. Nano Lett., 1, 14—7. 

The stable and bright dendron nanocrystals were soluble in various aqueous media, including all common biological buffer solutions tested. However, coating with dendron led to an increase of nanocrystal diameters [52]. In this example, dendritic nanoreactor influenced the solubility of QDs and improved its stability. 

Dendritic nanoreactor 1 was also employed as a recyclable micellar nanoreactor, stabilizer, and activator of Cu -catalyzed alkyne—azide cycloaddition click reaction, CuAAC reaction, in the presence of a very low amount (only 0.1%) of Cu (hexabenzyltren) Br (tren = triaminoethylantine) catalyst, 4, in aqueous media (Fig. 6.24) [60]. 

Dendritic nanoreactors can be used as a template and/or stabilizer for synthesis of nanoparticles with definite size and disparity. Various kinds of mono and bimetallic nanoparticles, as well as QDs, have been prepared using dendrimers. 

The role of dendritic nanoreactors is not limited to templating and stabilizing. They are capable of molecular recognition through the filtering role of their periphery. 

Applications of dendritic nanoreactors are beyond the issues discussed in this chapter, and that readers who are interested are encouraged to study the references for more details. 

Figure 17.16 Schematic of a dendritic nanoreactor, which can use the phase-separated nature of the macromolecule to facilitate mass transport of reagents. (Reproduced with permission from J.M.J. Frechet, Dendrimers and supramolecular chemistry, Proceedings of the National Academy of Sciences of the United States of America, 99, 8, 4782-4787. 2002 National Academy of Sciences, USA.)...

Heck heterocoupling within a dendritic nanoreactor. Nano Letters, 1,14. 

Ooe, M., Murata, M., Mizugaki, T., Ebitani, K. and Kaneda, K. (2002) Dendritic nanoreactors encapsulating Pd particles for substrate-spedfic hydrogenation of olefins. Nano Letters,... 

Gitsov et al 10) produced a nanoreactor fi om laccase and linear poly(ethylene oxide)-dendritic poly(benzyl ether) diblock copolymers. A notable feature of this system is the presence of hydrophobic dendritic pockets that increase the local concentration of water-insoluble organic compounds near the active site where they are oxidized. Li and Hsieh (77) employed a hydrogel fiber membrane, with a large surface area and improved organic solvent solubility in order to facilitate lipase reactions. He (72) grafted lipase onto silica particles, which permitted him to carry out synthesis of polyesters, polycarbonates, polyphosphates, and their copolymers at temperatures up to 150°C. 

Green Oxidation of Steroids in Nanoreactors Assembled from Laccase and Linear-Dendritic Copolymers... 

There are also examples of nanoreactors which have increased enzyme activity when encapsulated compared with bulk conditions. PICsomes that are stable to salt and elevated temperatures have been successfully developed using PEG-h-P( Asp) and are able to encapsulate trypsin without altering the original enzymatic activity [25]. Furthermore, these specifically designed PICsomes maintained their vesicular architecture at salt concentrations of 300 mM NaCl and temperatures up to 70°C, with only a subtle inaease in their size. For example, encapsulated nucleoside hydrolase has a substrate turnover number (kat) up to six times higher than the free enzyme [59]. Other enzymes, such as GOx and HRP, showed an 85% inaease in activity afta encapsulation in polyelectrolyte capsules [112], In addition, laccase entrapped in linear-dendritic based nanoreactors showed superior activity compared with its activity in bulk, and also inaeased temperature stability (up to 70 C) [19]. Howeva, the intrinsic branched architecture of den-drimers offers insufficient fluidity and space for entrapping larger biomolecules. 

Gitsov I, Hamzik J, Ryan J, Simonyan A, Nakas JP, Omori S, Krastanov A, Cohen T, Tanen-baum SW. Enzymatic nanoreactors for environmentally benign biotransformations. 1. Formation and catalytic activity of supramolecular complexes of laccase and hnear-dendritic block copolymers. Biomacromolecules 2008 9(3) 804-ll. 

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