Label-free imaging of polymeric nanomedicines using coherent anti-stokes Raman scattering microscopy

Nanoparticulate drug delivery is known to greatly improve the efficacy of pharmaceuticals and has found a wide range of applications with different administration methods including oral, intravenous, transcutaneous and ocular routes. However, the mechanisms by which these nanoparticles travel through, interact with, and modify tissues and how this relates to the improved drug performance are still unclear. These are critical questions that need to be answered to optimise the properties of future pharmaceuticals, dose rates and frequencies, and reduce potential side effects. Our ability to answer these questions is greatly hindered by the fact that there is currently no imaging modality available to directly visualise such small particles and the structure and function of the surrounding tissue, without the aid of contrast agents or highly invasive methods. Current imaging modalities derive image contrast of the nanoparticles and/or the surrounding tissues by means of external labels. We present coherent antistokes Raman scattering microscopy as a novel tool for imaging nanoparticle drug carriers against a background of biological tissues and cells.