A polydopamine-based coating technology to manufacture probes for multimodality imaging.

1120 Objectives The development of polydopamine (PD) coating technique has enabled many applications, and it inspires the development of multifunctional nanoprobes for molecular imaging. In addition to its superior optical behavior, PD also posesses good chelating property for transition metal ions. Furthermore, the coating layer provides a platform for further functionalization, for instance, molecules can be anchored onto the polymer layer through Schiff-type reactions or Michael addition reaction. Taking the advantages of such properties, we have developed a technology based on PD coating, to transform nanoplatforms into multimodal probes with the potential application in molecular imaging. Methods Gold nanoparticles with the size of 18 nm were first manufactured. Then the nanoparticles were mixed with dopamine hydrochloride in a mixed solution of water, ethanol and Tris buffer, and was stirred in air. A solution of copper sulfate was incubated with dopamine and added halfway of the reaction. After coating, polyethylene glycol or folic acid which had been functionalized with amine or thiol groups was added for further functionalization. The coated nanoparticles were separated, and various characterizations were performed. MTT tests were done to test the cytotoxicity. Moreover, ex vivo photoacoustic experiments were performed. Results The morphology of the nanoprobe was characterized by transmission electron microscopy and the coating layer with the thickness ranging from 4 nm to 15 nm was visible. Infrared red spectrum proved that the functionalized molecules were anchored onto the surface. The absorption spectra showed peaks at 536 nm and 595 nm. The molar ration between gold and copper is 20:1, which was determined by atomic absorption spectrum, and the presence of copper was also proved by X-ray photoelectron spectrum. Conclusions PD coating technology shows great potential in transforming nanomaterial to multifunctional probes for molecular imaging, with its innate chelating capability, optical behaviors and functionalization potentials. Research Support The research is supported by National Key Instrumentation Development Project (2011YQ030114) and Foundation for Innovative Research Groups of the National Natural Science Foundation of China (81421004).