Graphene Oxide as an Enzyme Inhibitor: Modulation of Activity of α-Chymotrypsin

Abstract

We have investigated the efficacy of graphene oxide (GO) in modulating enzymatic activity. Specifically, we show that graphene oxide can mimic as an artificial receptor and inhibit the activity of α-chymotrypsin (ChT), a serine protease. Most significantly, our data demonstrate that GO exhibits the highest inhibition dose response (by weight) for α-chymotrypsin inhibition compared to all other reported artificial inhibitors. Through fluorescence spectrometry and circular dichroism (CD) studies, we show that this protein-receptor interaction is highly biocompatible and conserves the protein’s secondary structure over extended periods (>24 h). We have also explored GO-enzyme interaction by controlling the ionic strength of media, which attenuates the host-guest electrostatic interaction. These findings suggest a new generation of enzymatic inhibitors that can be applied to other complex proteins by systematic modification of GO functionality.

Interactions of graphene and graphene oxide with proteins and peptides

“…Apparently, the enzyme immobilization onto GO might be a result of the synergic effect of the different interactions. De et al [96] studied the interaction between GO and chymotrypsin and found that GO could strongly inhibit the activity of chymotrypsin, which might be due to the coexistence of anionic, hydrophobic, and π -π stacking interactions and a large surface area to mass ratio of GO. As pointed by Duinhoven et al the enzyme immobilization on solid substrate should be a comprehensive result of several attractive and repulsive interactions, and the exact interaction or " driving force " for it should be different for various classes of enzymes/proteins [121] .…”

“…Generally, the conformation of the enzymes might be changed after being immobilized on solid substrate surface, thus, their activities could be affected upon immobilization [96] . The effect of the solid substrate on the immobilized enzymes in many cases is unpredictable because its surface structure and property are unknown.…”

Chemically Exfoliated MoS2 as Near‐Infrared Photothermal Agents

“…Because of its high surface-area-to-mass ratio, ceMoS 2 also possesses loading capacities on par with GO, the current best-in-class. [15] Clearly, ceMoS 2 possesses many desirable traits present in the aforementioned photothermal agents.…”

“…This value is significant, as it demonstrates that ceMoS 2 has a ChT doseinhibition capacity comparable to GO, which is the current benchmark material (full comparison in the Supporting Information). [15] To show that the host-guest interaction between ChT and ceMoS 2 is reversible, we incubated ChT with 11 ppm of ceMoS 2 (full inhibition concentration) in media of increasing ionic strength to negate electrostatic interactions. [27] In one set of experiments, ceMoS 2 was added to ChT in media prespiked with NaCl (pre-incubated).…”

“…These observations suggest that either some part of ChT is denatured following complexation with ceMoS 2 , or that there may be a two component complexation process where one component acts through non-electrostatic forces. [15] To distinguish between these mechanisms, we investigated the protein structure of ChT after complexation with ceMoS 2 using circular dichroism (CD) and fluorescence spectroscopy. Here, using CD, it can be seen that native ChT structure presents characteristic minima at 232 and 204 nm (Figure 4a and Figure S3).…”