Preparation and characterization of oxidized Multi-walled Carbon Nanotubes-Immobilized Aspergillus sp. Laccase Hybrid Materials

Abstract

This work deals with preparation and characterization of immobilized laccase (Aspergillus sp.) over oxidized multi-walled carbon nanotubes (ox-MWCNTs) via simple mixing technique. The resulting materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscope (TEM) and particle size distribution analysis using dynamic light scattering technique (DLS). The results showed that the TEM images exhibited more separate individual carbon bundles with particle size around of 396 nm after enzyme immobilization rather than the spaghetti-like tubes with size about 180 nm in the case of ox-MWCNTs. Also, the lowering in the zeta potential negative value (-5 mv) proved that the free carboxyl groups at ox-MWCNT surface were decreased after enzyme immobilization. Moreover, the thermal stability was decreased after enzyme immobilization using TGA. These results confirmed that the laccase could be reacted at the side walls of the ox-MWCNTs without structure damage. The biocatalytic effect of the immobilized laccase was investigated after its incubation with silver nitrate solution for 1 and 24 h. It can be concluded that the biocatalytic efficiency of the immobilized laccase could be enhanced after its incubation with silver nitrate solution for 24 h at room temperature relative to the free form. On the other hand, the enzyme stability was improved after immobilization up to 50ºC and at pH 3.0, while no remarkable differences on the activity values were observed for immobilized and free laccases at acidic pH range (4-6).

Organic-Inorganic Composites Based on Multi-walled Carbon Nanotubes ‎ Containing Lysine/Histidine

“…CNTs are often functionalized with different functional groups (such Egyptian Journal of Chemistry http://ejchem.journals.ekb.eg/ as -OH and -COOH) using covalent and non-covalent methods to increase dispersity in aqueous media and minimize toxicity [11][12][13][14]. Nonetheless, the toxicity of carbon nanotubes remains an unsettled question, with various research indicating opposing patterns [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. CNTs have mostly been employed as reinforcement filler in polymer-based scaffolds in the field of tissue engineering, increasing mechanical and electrical properties and permitting the production of scaffolds for neural, cardiac, and bone tissue engineering.…”