Amplification of photoacoustic effect in bimodal polymer particles by self-quenching of indocyanine green.

A new type of bimodal contrast agent was made that is based on the self-quenching of indocyanine green (ICG) encapsulated in a biocompatible and biodegradable polymer shell. The increasing of a local ICG concentration that is necessary for the obtaining of self-quenching effect was achieved by freezing-induced loading and layer-by-layer assembly. As a result, an efficient photoacoustic(optoacoustic)/fluorescent contrast agent based on composite indocyanine green/polymer particles was successfully prepared and was characterized by fluorescence and photoacoustic(optoacoustic) tomography . This type of contrast agent holds good promise for clinical application owing to its high efficiency and biosafety.