Hydrophobic drug loaded contrast agents: effects on enhancement

The objectives of this research are to develop methods to produce polymeric ultrasound (US) contrast agents (CA) with the added capability of serving as drug carriers. Although about 30 million US diagnostic scans are performed every year, discrimination between diseased and normal tissue is not optimal without the use of CA. Combining imaging and drug delivery functions would enable entirely new applications for CA. PLA (Poly-lactic acid) microcapsules were previously developed in our lab as ultrasound CA, using a double emulsion process, where encapsulated camphor and ammonium carbonate were sublimed out to produce hollow microcapsules. This work investigates a model drug incorporated by two methods, either absorbed to the surface of the microcapsules or included within the shell. Sudan Black was used a small molecular weight hydrophobic drug. The drug-loaded CA show US enhancement of 20-27 dB, and an imaging half live of more than 15 min in physiological environment. In vivo echogenicity persisted for over 11 minutes, at 7.5 MHz.