Surfactant-Free Synthesis of Graphene Oxide Coated Silver Nanoparticles for SERS Biosensing and Intracellular Drug Delivery

Surface-enhanced Raman scattering (SERS) has attracted increasing attention in the field of biochemical sensing since its discovery in 1970s, in virtue of its ultrahigh sensitivity to extremely low concentration of analyte. The performance of SERS biosensing strongly relies on the surface properties of SERS substrates, which are generally noble metallic nanoparticles. Surfactants have always been used for the preparation of nanoparticles to maintain the stability of nanocolloids, which greatly affect the efficiency of SERS sensing due to the space blocking between SERS substrates and analytes, as well as the interference of intrinsic Raman signals from surfactant themselves. Herein, without adding any surfactant, we synthesized nanosized graphene oxide (NGO) coated silver nanoparticles (Ag@NGO), which were used as efficient SERS substrates, taking the advantages of surfactant-free surface with inert protective effect of the GO shell. The Ag@NGO nanoparticles demonstrated excellent SERS sensing capability and can be used as biocompatible nanoprobes for intracellular biosensing. The π–π interaction between the anticancer drug of doxorubicin (DOX, a typical anticancer drug) and GO facilitates DOX loading onto Ag@NGO nanoparticles as drug delivery nanocarriers as well. Therefore, Ag@NGO holds great potential as a theranostic platform with capabilities of both SERS biosensing and drug delivery.