Graphene Oxide as a Matrix for Enzyme Immobilization

Abstract

Graphene oxide (GO), having a large specific surface area and abundant functional groups, provides an ideal substrate for study enzyme immobilization. We demonstrated that the enzyme immobilization on the GO sheets could take place readily without using any cross-linking reagents and additional surface modification. The atomically flat surface enabled us to observe the immobilized enzyme in the native state directly using atomic force microscopy (AFM). Combining the AFM imaging results of the immobilized enzyme molecules and their catalytic activity, we illustrated that the conformation of the immobilized enzyme is mainly determined by interactions of enzyme molecules with the functional groups of GO.

Increasing the activity of immobilized enzymes with nanoparticle conjugation

“…When GO is directly loaded with horseradish peroxidase (HRP) it has a maximum loading of 0.1 mg mg À1 [39], but loadings increase to 0.2, 0.7 and 1.3 mg mg À1 when applied to separate CRGO samples which were chemically reduced with L-ascorbic acid (L-AA) for 2, 4 and 12 h (CRGO-2, CRGO-4, and CRGO-12) [40]. Higher enzyme loading could be sustained on GO samples that were further reduced and it was also noted that the resultant hydrophobicity of the CRGO surface was proportional to the extent of its chemical reduction -a process which subsequently functionalized the GO surface with amine groups.…”

Interactions of graphene and graphene oxide with proteins and peptides

“…GO used as a matrix for enzyme immobilization was first reported by Zhang et al [65,66] . Without using any cross-linking reagents, horseradish peroxidase (HRP) and lysozyme molecules were immobilized onto GO simply by incubating the GO sheets in a phosphate buffer containing the HRP or lysozyme.…”

“…The unique large and atomically flat surface of GO provides a platform for studying the as loaded external species through high-resolution surface analytic techniques such as atomic force microscopy (AFM) etc. This is essential for studying the interaction mechanism between GO and loaded species and also for their conformational change [65] . The oxygen-containing groups on GO sheets afford them with moderate biocompatibility, thus, favorable to their biological and biomedicinal applications [72 -75] .…”

Graphene and graphene oxide as nanomaterials for medicine and biology application

“…The variation in the surface charge density of functional groups containing oxygen on GO determines its preparation and storage. The GO-oxygen containing groups, makes it acceptable for immobilization of biocatalysts with no surface adjustments and no coupling reagents [43]. Further, to monitor the protein absorption by using the channel of graphene as electrolyte gate, field effect transistor was [25].…”