Glutathione peroxidase (GPx) protects cells from oxidative damage by scavenging surplus reactive oxygen species (ROS). Commonly, an appropriate amount of ROS acts as a signal molecule in the metabolism. A smart artificial GPx exhibits adjustable catalytic activity, which can potentially reduce the amount of ROS to an appropriate degree and maintain its important physiological functions in metabolism. To construct an optimum and excellent smart artificial GPx, a novel supramolecular microgel artificial GPx (SM-Te) was prepared based on the supramolecular host-guest interaction employing the tellurium-containing guest molecule (ADA-Te-ADA) and the cyclodextrin-containing host block copolymer (poly(N-isopropylacrylamide)-b-[polyacrylamides-co-poly(6-o-(triethylene glycol monoacrylate ether)-β-cyclodextrin)], PPAM-CD) as building blocks. Subsequently, based on these building blocks, SM-Te was constructed and the formation of its self-assembled structure was confirmed by dynamic light scattering, NMR, SEM, TEM, etc. Typically, benefitting from the temperature responsive properties of the PNIPAM scaffold, SM-Te also exhibited similar temperature responsive behaviour. Importantly, the GPx catalytic rates of SM-Te displayed a noticeable temperature responsive characteristic. Moreover, SM-Te exhibited the typical saturation kinetics behaviour of a real enzyme catalyst. It was proved that the changes of the hydrophobic microenvironment and the pore size in the supramolecular microgel network of SM-Te played significant roles in altering the temperature responsive catalytic behaviour. The successful construction of SM-Te not only overcomes the insurmountable disadvantages existing in previous covalent bond crosslinked microgel artificial GPx but also bodes well for the development of novel intelligent antioxidant drugs.

In an effort to construct smart artificial glutathione peroxidase (GPx) featuring high catalytic activity in an efficient preparation process, an artificial microgel GPx (PPAM-ADA-Te) has been prepared using a supramolecular host-guest self-assembly technique. Herein, 6,6'-telluro-bis(6-deoxy-β-cyclodextrin) (CD-Te-CD) was selected as a tellurium-containing host molecule, which also served as the crosslinker for the scaffold of the supramolecular microgel. And an adamantane-containing block copolymer (PPAM-ADA) was designed and synthesized as a guest building block copolymer. Subsequently, PPAM-ADA-Te was constructed through the self-assembly of CD-Te-CD and PPAM-ADA. The formation of this self-assembled construct was confirmed by dynamic light scattering, NMR, SEM and TEM. Notably, PPAM-ADA-Te not only exhibits a significant temperature responsive catalytic activity, but also features the characteristic saturation kinetics behaviour similar to that of a natural enzyme catalyst. We demonstrate in this paper that both the hydrophobic microenvironment and the crosslinker in this supramolecular microgel network played significant roles in enhancing and altering the temperature responsive catalytic behaviour. The successful construction of PPAM-ADA-Te not only provides a novel method for the preparation of microgel artificial GPx with high catalytic activity but also provides properties suitable for the future development of intelligent antioxidant drugs.

A smart supramolecular artificial glutathione peroxidase (GPx) with tunable catalytic activity was prepared based on host–guest interaction and a blending process. The change of the self-assembled structure of SGPxmax during the temperature responsive process played a significant role in altering the temperature responsive catalytic behavior.

A supramolecular artificial glutathione peroxidase (PNIPAM-CD-g-Te) was prepared based on a supramolecular graft copolymer. PNIPAM-CD-g-Te was constructed by supramolecular host-guest self-assembly. Significantly, PNIPAM-CD-g-Te displayed noticeable temperature-dependent catalytic activity and typical saturation kinetics behavior. It was also proved that the change in the self-assembled structure of PNIPAM-CD-g-Te during the temperature-dependent process played a significant role in the temperature-dependent catalytic behavior. The construction of PNIPAM-CD-g-Te based on supramolecular graft copolymer endows artificial GPx with temperature-dependent catalytic ability, enriched catalytic centers, and homogeneously distributed catalytic centers. This work bodes well for the development of other biologically related host-guest supramolecular biomaterials.

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A crown ether/amino rotaxane was investigated using two-dimensional free-energy landscapes to characterize the conformational change of the crown ether and the shuttling motions in chloroform and water.

With cassava starch as a raw material and octenyl succinic anhydride as an esterifying agent, octenyl succinic anhydride modified starch (OSA–starch) was prepared in an aqueous medium and treated by water‐bath heating and microwave radiation at a certain temperature, respectively. The reaction kinetics of esterification were studied. The structural analysis and synthesis mechanism of OSA–starch were investigated by means of scanning electron microscopy and Fourier transform infrared spectroscopy. The differences in the esterification reaction kinetics between starches treated with water‐bath heating and microwave radiation were observed. Under the condition of water‐bath heating, the apparent activation energy of the esterification reaction was 52.22 ± 1.21 kJ/mol, and the pre‐exponential factor was 9018.20/min−1. Under the condition of microwave radiation, the apparent activation energy of the esterification reaction was 50.13 ± 1.16 kJ/mol, and the pre‐exponential factor was 4510.21/min−1. We found that microwave radiation could reduce both the activation energy of the reaction and the pre‐exponential factor. The lowering effect of the apparent activation energy was greater than that of the pre‐exponential factor under the condition of microwave radiation, and this resulted in increased reaction rates. The change in the esterification reaction kinetics was a nonthermal effect of microwave radiation on the esterification of cassava starch. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43909.

The development of selenium‐enriched food is one of the most effective ways to acheive selenium supplementation. However, the selenium content in selenium‐enriched food is unstable, and the selenium in the food needs to be incorporated into glutathione peroxidase (GPx) by the human body before it can exert its antioxidant activity. Herein, a selenium‐enriched cassava starch (Se‐ca‐starch80) with immediate antioxidant activity is synthesized by the successive esterification and selenation of cassava starch. The characterizations such as proton nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FT‐IR), scanning electron microscope (SEM), and X‐ray diffraction (XRD) indicate that the reactions mainly occur on the surface of starch and do not destroy the starch skeleton significantly. Such Se‐ca‐starch80 with selenium content of 9.44 µg g–1 reveals a remarkable antioxidant activity (the initial rate of the catalytic reaction, v0 > 10 µmol L–1 min–1) due to the cooperation of catalytic centers, substrate recognition sites, and hydrophobic microenvironments. Similar to the natural GPx, the Se‐ca‐starch80 is non‐cytotoxic and shows a saturation kinetic catalytic behavior. This work may open the door to design modified starch for functional foods and antioxidant drugs.