Enzyme–Carbon Nanotube Conjugates in Room-temperature Ionic Liquids

Abstract

Room-temperature ionic liquids (RTILs) are intriguing solvents, which are recognized as "green" alternatives to volatile organics. Although RTILs are nonvolatile and can dissolve a wide range of charged, polar, and nonpolar organic and inorganic molecules, there remain substantial challenges in their use, not the least of which is the solvents' high viscosity that leads to potential mass transfer limitations. In the course of this work, we discovered that the simple adsorption of the bacterial protease, proteinase K, onto singlewalled carbon nanotubes (SWNTs) results in intrinsically high catalytic turnover. The high surface area and the nanoscopic dimensions of SWNTs offered high enzyme loading and low mass transfer resistance. Furthermore, the enzyme-SWNT conjugates displayed enhanced thermal stability in RTILs over the native suspended enzyme counterpart and allowed facile reuse. These enzyme-SWNT conjugates may therefore provide a way to overcome key operational limitations of RTIL systems.

Controlled biodegradation of polymers using nanoparticles and its application

“…The first step is the adsorption of enzyme on the surface of the substrate through surface-binding domain resulting in the formation of enzyme-substrate complex and, the second step is hydrolysis of the ester bonds leading to the formation of soluble degradation products. Further, nanoparticles with high surface area have the advantages of adsorption of the bacterial protease (proteinase K) onto single-walled carbon nanotubes (SWNTs) resulting intrinsically high catalytic turnover owing to greater enzyme loading and low mass transfer resistance [78]. The stereochemistry of the polymer plays an important role for its degradation e.g.…”

Methods for stabilizing and activating enzymes in ionic liquids—a review

“…The noncovalent binding of proteinase K onto single-walled carbon nanotubes (SWNTs) resulted in higher enzyme activity and higher thermal stability than its native form in ILs; the enzyme-SWNT conjugates were well dispersed in ILs. 108 Similarly, Candida rugosa lipase adsorbed on multi-walled carbon nanotubes (MWNTs) displayed a higher transesterification activity and enantioselectivity than the pHtuned free form in [BMIM][PF 6 ]. 109 Du et al 110 6 ]), and observed that the encapsulated enzymes retained their bioelectrocatalytic activities toward the reduction of oxygen and hydrogen peroxide.…”

Cytochrome c dissolved in 1‐allyl‐3‐methylimidazolium chloride type ionic liquid undergoes a quasi‐reversible redox reaction up to 140°C

“…Accordingly, there are increasing studies on the development of functional ILs by selecting suitable structure of the component ions. The application of ILs as reaction media recently covers the bio‐derived molecules, for example, there are potential trials to use ILs as a matrix for enzymatic reactions (Eker et al, 2007; Kaar et al, 2003; Kragl et al, 2002; Laszlo and Compton, 2001; Lau et al, 2004), and as constituents of the sensitive layers of biosensors (Bozhinova et al, 2004). These attempts have potential for the construction of green biosystems because of less wastes and longer lifetime.…”