Using well-defined Ag nanocubes as substrates to quantify the spatial resolution and penetration depth of surface-enhanced Raman scattering imaging.

The multiplexing capability and high sensitivity of surface-enhanced Raman scattering (SERS) make this new imaging modality particularly attractive for rapid diagnosis. With 100 nm Ag nanocubes serving as the substrate, this work quantitatively evaluated, for the first time, some of the fundamental parameters of SERS imaging such as blur, spatial resolution and penetration depth. Our results imply that SERS is a high-resolution imaging technique with a blur value of 0.5 μm that is lower than many traditional modalities such as mammography. The spatial resolution was measured to be 1.1 μm, suggesting that SERS images could be collected effectively by adjusting the imaging step size to the same length scale, or no more than 2 μm. The major drawback of SERS imaging is its penetration depth, which is limited by the scattering and absorption of tissues. We demonstrated that enhancement of signal caused by aggregation of multiple nanoparticles could help overcome this potential road-block to in vivo imaging.