Nested  Microbubbles  as  Ultrasound  Contrast  Agents  and  Triggered  Drug
Delivery  Vehicles
Ultrasound  imaging  is  non-­‐ionizing  radiation  and  an  inexpensive,  non-­‐invasive  diagnostic   tool.  However,  ultrasound  alone  results  in  poor  image  resolution  as  well  as  shallow   depth  of  view  and  is  therefore  insufficient  for  many  diagnostic  processes.  In  order  to   improve  the  resolution  of  the  image,  a  contrast  agent  is  injected  into  the  bloodstream,   but  with  this  comes  an  added  safety  risk  as  well  as  complications  due  to  a  relatively   short  lifespan.  To  improve  currently  available  contrast  agents,  a  novel  design  is   formulated.  This  contrast  agent  is  comprised  of  lipid  microbubbles  within  the  aqueous   core  of  polymer  shell  microcapsules,  termed  nested  microbubbles.
Nested  microbubbles  also  function  as  prospective  ultrasound  triggered  drug  delivery   vehicles  when  the  polymer  shell  is  replaced  with  a  lipid  bilayer  and  the  core  now   contains  an  aqueous  drug  in  addition  to  the  microbubbles.  This  formulation  has  dual   benefits:  drug  release  from  the  membrane  when  microbubbles  are  present  within  the   liposome  and  an  increase  in  image  brightness  during  ultrasound  guided  procedures.  One   important  aspect  of  this  research  is  the  relationship  between  the  type  of  cavitation  and   resulting  membrane  disruption.  Two  regimes  exist  during  the  membrane  damage-­‐ inducing  events  caused  by  cavitating  microbubbles  which  can  allow  for  tailored  drug   release  behavior  at  the  desired  location  within  the  body.