Polyaniline nanoparticles: Potential optical coherence tomography contrast agents

Polyaniline, an organic conducting polymer, exhibits strong light absorption in the near-infrared region. Herein, the potential of polyaniline nanoparticles as the contrast agents for optical coherence tomography imaging was investigated. Polyaniline nanoparticles were synthesized by a facile chemical oxidative method. The optical coherence tomography images obtained from ex vivo swine liver tissues showed the concentration-dependent contrast effect of polyaniline nanoparticles. Then the nanoagents were applied to in vivo optical coherence tomography imaging of tumor tissues using a xenograft tumor mouse model. The penetration depth of the optical coherence tomography signals from tumors injected with polyaniline nanoparticles was significantly lower than that from tumors injected with phosphate buffer solution. The remarkable contrast effect of polyaniline nanoparticles was then quantitatively studied by the attenuation coefficients of optical coherence tomography signals. Furthermore, the permeation dynamics of polyaniline nanoparticles in tissue was also studied by Raman spectroscopy.