Flowerlike hybrid horseradish peroxidase nanobiocatalyst for the polymerization of guaiacol

Investigation of the free-radical polymerization of vinyl monomers using horseradish peroxidase (HRP) nanoflowers

In this study, we report the production of flower-shaped HRP-Cu2+ hybrid nano biocatalyst (HRP-Cu2+ HNF) from the complexation between horseradish peroxidase (HRP) enzyme and Cu2+ ions, and investigate catalytic activity and stability of the obtained nanoflowers on the polymerization of some vinyl monomers (styrene, methylmethacrylate, acrylamide and N-isopropylacrylamide). Polymerizations of these monomers, except water soluble acrylamide, were accomplished under emulsion conditions using cationic, anionic and non-ionic surfactants in the presence of hydrogen peroxide (H2O2) and 2,4-pentanedione mediator. Optimum polymerizations were achieved under the conditions of non-ionic surfactant (tween 40) used. HRP-Cu2+ HNF mediated polymerizations resulted in very high yields and molecular weights (M n) of the polymers. Optimum polymerization of styrene with 84% of yield (M n = 319 kDa) was accomplished at room temperature. However, the highest polymerization yields for acrylamide (96%, M n = 171 kDa) and N-isopropylacrylamide (85%, M n = 185 kDa) was achieved at 70 °C. Similarly, optimum polymerization of methylmethacrylate was accomplished with 84% of yield (M n = 190 kDa) at 60 °C. While free-HRP loses its catalytic activity at 60 °C and above temperatures, HRP-Cu2+ HNF showed very high catalytic activity and stability even at 70 °C. Increasing activity and stability of hybrid nanoflowers provide significant advantages for both scientific and industrial applications.

Investigation of Peroxidase-Like Activity of Flower-Shaped Nanobiocatalyst from Viburnum Opulus L. Extract on the Polymerization Reactions

Here, we report the effects of peroxidase-mimicking activity of flower shaped hybrid nanobiocatalyst obtained from Viburnum-Opulus L. (Gilaburu) extract and Cu2+ ions on the polymerization of phenol and its derivatives (guaiacol and salicylic acid). The obtained nanoflowers exhibited quite high catalytic activity upon the polymerization of phenol and guaiacol. The yields and the number average molecular weights of the obtained polymers were significantly high. Due to solubility issue of salicylic acid in aqueous media, polymerization of salicylic acid resulted in very low yields. Free-horseradish peroxidase (HRP) enzyme is known to be losing its catalytic activity at 60 °C and above temperatures. However, the synthesized nanoflowers exhibited quite high catalytic activity even at 60 °C and above reaction temperatures. This provides notable benefits for reactions needed at high temperatures, and it is very important to use these kinds of nanobiocatalysts for both scientific studies and industrial applications.

Production of flower‐shaped nanobiocatalysts from green tea and investigation of their peroxidase mimicking activity on the polymerization of phenol derivatives

Enzyme catalyzed reactions are known to be environmental friendly and easy method for many applications. However, utilization of enzymes in a variety of reactions is strictly limited due to their high cost, instability in aqueous solutions, denaturation in organic solvents and high temperatures. For this reason, it is important to discover new generation catalyst systems indicating enzyme‐like catalytic activity. Here, we report hybrid organic–inorganic flower‐shaped green tea‐Cu2+ nanobiocatalyst synthesized from green tea extract as an organic component and copper (II) ions (Cu2+) as inorganic component. The effect of the peroxidase‐mimicking activity of green tea‐Cu2+ nanobiocatalyst was investigated on the polymerization of phenol and derivatives (guaiacol and salicylic acid) through Fenton‐like reaction mechanism. Obtained successful outcomes showed that the synthesized nanobiocatalyst showed very high catalytic activity upon polymerization of phenol and guaiacol. The slight solubility of salicylic acid in water limited to achieve its polymerization under‐performed reaction conditions. The yields and molecular weights of the obtained polymers were found to be quite high. While free peroxidase enzymes like horseradish peroxidase (HRP) enzyme loses its catalytic activity at 60°C and above temperatures, green tea‐Cu2+ nanobiocatalyst exhibited very high catalytic activity upon polymerization reactions even at 60°C reaction temperature. This outcome provides significant advantages in some reactions requiring high temperatures. In order to understand the origin of the catalytic activity of the green tea‐Cu2+ nanoflowers, similar biocatalysts were also synthesized from caffeine and catechin alkaloids which are the active components of green tea. Caffeine‐Cu2+ and catechine‐Cu2+ nanobiocatalysts also exhibited quite high catalytic activity toward polymerization of phenol and derivatives. We suggest that green tea‐Cu2+ and similar types of nanobiocatalysts may expand their utilization in polymer chemistry as promising catalytic agents for radicalic polymerizations.

Immobilized enzymes in inorganic hybrid nanoflowers for biocatalytic and biosensing applications

Enzyme immobilization has been accepted as a powerful technique to solve the drawbacks of free enzymes such as limited activity, stability and recyclability under harsh conditions. Different from the conventional immobilization methods, enzyme immobilization in inorganic hybrid nanoflowers was executed in a biomimetic mineralization manner with the advantages of mild reaction conditions, and thus it was beneficial to obtain ideal biocatalysts with superior characteristics. The key factors influencing the formation of enzyme-based inorganic hybrid nanoflowers were elucidated to obtain a deeper insight into the mechanism for achieving unique morphology and improved properties of immobilized enzymes. To date, immobilized enzymes in inorganic hybrid nanoflowers have been successfully applied in biocatalysis for preparing medical intermediates, biodiesel and biomedical polymers, and solving the environmental or food industrial issues such as the degradation of toxic dyes, pollutants and allergenic proteins. Moreover, they could be used in the development of various biosensors, which provide a promising platform to detect toxic substances in the environment or biomarkers associated with various diseases. We hope that this review will promote the fundamental research and wide applications of immobilized enzymes in inorganic hybrid nanoflowers for expanding biocatalysis and biosensing.