Enzyme-Nanoporous Gold Biocomposite: Excellent Biocatalyst with Improved Biocatalytic Performance and Stability

Abstract

BackgroundApplications involving biomolecules, such as enzymes, antibodies, and other proteins as well as whole cells, are often hampered by their unstable nature at extremely high temperature and in organic solvents.Methodology/Principal FindingsWe constructed enzyme-NPG biocomposites by assembling various enzymes onto the surface of nanoporous gold (NPG), which showed much enhanced biocatalytic performance and stability. Various enzymes with different molecular sizes were successfully tethered onto NPG, and the loadings were 3.6, 3.1 and 0.8 mg g−1 for lipase, catalase and horseradish peroxidase, respectively. The enzyme-NPG biocomposites exhibited remarkable catalytic activities which were fully comparable to those of free enzymes. They also presented enhanced stability, with 74, 78 and 53% of enzymatic activity retained after 20 successive batch reactions. Moreover, these novel biocomposites possessed significantly enhanced reaction durability under various thermal and in organic solvent systems. In a sample transesterification reaction, a high conversion rate was readily achieved by using the lipase-NPG biocomposite.Conclusion/SignificanceThese nano-biocomposite materials hold great potential in applications such as biosensing, molecular electronics, catalysis, and controlled delivery.

An overview of dealloyed nanoporous gold in bioelectrochemistry

“…After incubation for 30 minutes at 50, 60 and 70°C, 62, 59 and 54% of the initial activity was observed for free lipase, compared with 75, 74, and 76%, respectively, for lipase adsorbed on NPG ( Figure 6A) [38]. After treatment with ethyl acetate (log P of 0.68), 27% of the initial 40 activity of free lipase remained, while 81% activity was observed for the lipase-NPG biocomposite [38].…”

“…After treatment with ethyl acetate (log P of 0.68), 27% of the initial 40 activity of free lipase remained, while 81% activity was observed for the lipase-NPG biocomposite [38]. On exposure to chloroform (log P of 2.0) free and immobilised lipase retained 42 and 85% of the initial activity, respectively.…”

“…Spectroscopic methods such as energy dispersive X-ray (EDX) spectroscopy 10 and X-ray photoelectron spectroscopy (XPS) have been used to analyse the chemical composition the electrodes. XPS is useful for the analysis of NPG functionalized with biomolecules at relatively low concentrations [38,39].…”

“…Firstly, enzymes confined within NPG display higher stability on exposure to high temperatures [49,50] and organic solvents [38] due to the nanopore providing a protective environment to the enzyme. After incubation at 50 °C for 2 h, only 6% of the initial activity of free laccase remained 35 in comparison to 60% for laccase immobilised on NPG [49].…”

“…Nanoporous gold has emerged as a promising support for the immobilisation of enzymes for (reprinted with permission from [38]), covalent bonding in the assistance of SAM (B) (reprinted with permission from [69]) and entrapment within conducting polymers (C) (reprinted with permission from [33]). Reproduced from [76] with permission.…”