Multifunctional polyelectrolyte microcapsules as a contrast agent for photoacoustic imaging in blood

The polyelectrolyte microcapsules that can be accurate either visualized in biological media or in tissue would en- hance their further in vivo application both as a carrier of active payloads and as a specific sensor. The immobiliza- tion of active species, for instance fluorescent dyes, quan- tum dots, metal nanoparticles, in polymeric shell enables visualization of capsules by optical imaging techniques in aqueous solution. However, for visualization of capsules in complex media an instrument with high contrast mod- ality requires. Herein, we show for the first time photoa- coustic imaging (PAI) of multifunctional microcapsules in water and in blood. The microcapsules exhibit greater photoacoustic intensity compare to microparticles with the same composition of polymeric shell presumably their higher thermal expansion. Photoacoustic intensity form microcapsules dispersed in blood displays an enhance- ment (2-fold) of signal compare to blood. Photoacoustic imaging of microcapsules might contribute to non-inva- sive carrier visualization and further their in vivo distribution.