SERS-fluorescence monitored drug release of a redox-responsive nanocarrier based on graphene oxide in tumor cells.

A redox-responsive drug carrier based on nanoscale graphene oxide (NGO) loaded with Ag nanoparticles, whose intracellular release behavior can be investigated by SERS-fluorescence combined spectroscopy, is presented. In this demonstrated drug carrier, to make the carrier integrated with the redox responsive property, we utilized disulfide linkages to load drug molecules to the surfaces of NGO directly, which can be cleaved by glutathione (GSH). Covalent drug loading and GSH-responsive release strategy can reduce the influence of the surface diffusion barriers introduced by multifunctionalization. Interestingly, the intracellular real-time drug release dynamics can be monitored by the combined SERS-fluorescence signals of the drugs, while the distribution of the drug carrier can simultaneously be tracked by the intrinsic SERS signals of NGO in the whole process. Our results show that upon the internalization of doxorubicin (DOX)-loaded nanocarriers into living cells, DOX was efficiently released under a GSH regulated reducing environment. Because tumor cells generally exhibit a higher concentration of GSH than normal ones, this drug carrier should have potential in the field of tumor therapy.