Oil-filled polymeric ultrasound contrast agent as local drug delivery system for lipophilic drugs

Novel polymeric microcapsules, filled with a mixture of gas and oil, were produced and their potential as ultrasound contrast agent-based drug delivery system for lipophilic drugs was investigated. Microcapsules were synthesized that contained either no oil, were almost half-filled with oil, or were almost completely filled with oil. Mean number weighted diameters were between 1.22 and 1.31 mum. At a low MI (1 MHz, P_ of 0.24 MPa), microcapsules typically compressed without cracking. At a high MI (1 MHz, P_ of 0.51 MPa), microcapsules cracked, thereby releasing their content. Guidance and monitoring of therapy will be possible because the microcapsules were echogenic and stable at low MI. These microcapsules therefore have great potential as local drug delivery system for lipophilic drugs.