Perfluorocarbon-loaded polydopamine nanoparticles as ultrasound contrast agents.

A versatile platform for the development of new ultrasound contrast agents is demonstrated through a one-pot synthesis and fluorination of submicron polydopamine (PDA-F) nanoparticles. The fluorophilicity of these particles allows loading with perfluoropentane (PFP) droplets that display strong and persistent ultrasound contrast in aqueous suspension and ex vivo tissue samples. Contrast under continuous imaging by color Doppler persists for 1 h in 135 nm PDA-F samples, even at maximum clinical imaging power (MI = 1.9). Additionally, use of a Cadence Contrast Pulse Sequence (CPS) results in a non-linear response suitable for imaging at 0.5 mg mL-1. Despite the PFP volatility and the lack of a hollow core, PDA-F particles display minimal signal loss after storage for over a week. The ability to tune size, metal-chelation, and add covalently-bound organic functionality offers myriad possibilities for extending this work to multimodal imaging, targeted delivery, and therapeutic functionality.