Denatured crude protein extracts from the sea anemone Entacmaea quadricolor as capping agents for silver nanoclusters

Novel nanomaterials derived from numerous biological samples including extracts from plants, animals, and even bacteria have gained prominence due to their unique properties, more environmental friendly preparation, and interesting bioactivities. Among these, protein-capped noble metal, e.g., Ag, nanoclusters (NC) have gained considerable attention for their many potential applications, and significant efforts are being directed at using a wide variety of protein sources as capping agents as well as. In this work, crude protein extracts from the sea anemone Entacmaea quadricolor (E. quadricolor) subjected to either heat or β-mercaptoethanol denaturation were prepared to investigate the effects of these processes in the formation of AgNC and on its preliminary bioactivity, measured using a hemolysis assay against human erythrocytes. Fourier-transform infrared spectrometry (FTIR) analysis showed comparable spectra for the two denatured crude protein-capped AgNC, as well with as the undenatured protein-capped AgNC, like previous reports indicating successful capping of the NC. Moreover, the spectra suggest no significant alterations if protein secondary structure upon NC formation. The crude protein extracts were also found to be very weakly hemolytic at the concentration range tested (0.5 – 1 mg protein/mL) and denaturing the protein prior to NC formation did not significantly alter its hemolytic activity as well. These results imply that E. quadricolor crude protein denaturation prior to use with the reduction of Ag+ has no deleterious effects in functioning as capping agents for the prepared AgNC.