Effect of Surface Modification of Multifunctional Nanocomposite Drug Delivery Carriers with DARPin on Their Biodistribution In Vitro and In Vivo.

We present a targeted drug delivery system for therapy and diagnostics that is based on a combination of contrasting, cytotoxic, and cancer-cell-targeting properties of multifunctional carriers. The system uses multilayered polymer microcapsules loaded with magnetite and doxorubicin. Loading of magnetite nanoparticles into the polymer shell by freezing-induced loading (FIL) allowed the loading efficiency to be increased 5-fold, compared with the widely used layer-by-layer (LBL) assembly. FIL also improved the photoacoustic signal and particle mobility in a magnetic field gradient, a result unachievable by the LBL alone. For targeted delivery of the carriers to cancer cells, the carrier surface was modified with a designed ankyrin repeat protein (DARPin) directed toward the epithelial cell adhesion molecule (EpCAM). Flow cytometry measurements showed that the DARPin-coated capsules specifically interacted with the surface of EpCAM-overexpressing human cancer cells such as MCF7. In vivo and ex vivo biodistribution studies in FvB mice showed that the carrier surface modification with DARPin changed the biodistribution of the capsules toward epithelial cells. In particular, the capsules accumulated substantially in the lungs─a result that can be effectively used in targeted lung cancer therapy. The results of this work may aid in the further development of the "magic bullet" concept and may bring the quality of personalized medicine to another level.

Indocyanine green dye based bimodal contrast agent tested by photoacoustic/fluorescence tomography setup.

Multimodal imaging systems are in high demand for preclinical research, experimental medicine, and clinical practice. Combinations of photoacoustic technology with other modalities including fluorescence, ultrasound, MRI, OCT have been already applied in feasibility studies. Nevertheless, only the combination of photoacoustics with ultrasound in a single setup is commercially available now. A combination of photoacoustics and fluorescence is another compelling approach because those two modalities naturally complement each other. Here, we presented a bimodal contrast agent based on the indocyanine green dye (ICG) as a single signalling compound embedded in the biocompatible and biodegradable polymer shell. We demonstrate its remarkable characteristics by imaging using a commercial photoacoustic/fluorescence tomography system (TriTom, PhotoSound Technologies). It was shown that photoacoustic signal of the particles depends on the amount of dye loaded into the shell, while fluorescence signal depends on the total amount of dye per particle. For the first time to our knowledge, a commercial bimodal photoacoustic/fluorescence setup was used for characterization of ICG doped polymer particles. Additionally, we conducted cell toxicity studies for these particles as well as studied biodistribution over time in vivo and ex vivo using fluorescent imaging. The obtained results suggest a potential for the application of biocompatible and biodegradable bimodal contrast agents as well as the integrated photoacoustic/fluorescence imaging system for preclinical and clinical studies.

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 in vitro. This type of contrast agent holds good promise for clinical application owing to its high efficiency and biosafety.