We have developed technologies to ensure liposomal and virus-based therapeutics can achieve good circulation following injection into the bloodstream, decreasing uptake into non-target tissue and allowing a level of accumulation in tumour deposits. However, at present, release of the tumor-cell-killing cargo and penetration of that cargo deep into the tumour is still sub-optimal. In response, we have developed systems which utilise focused ultrasound as a stimulus to trigger release of therapeutic payload and propel it deep into tumours. The ultrasound induced phenomena that drive this release and movement are the microstreaming created by inertial cavitation, an event resulting from the rapid expansion and violent collapse of a gas bubble in response to the rarefactional and compressional pressures exerted by an ultrasound wave.