Controllable microfluidic synthesis of multiphase drug-carrying lipospheres for site-targeted therapy.

We report the production of micrometer-sized gas-filled lipospheres using digital (droplet-based) microfluidics technology for chemotherapeutic drug delivery. Advantages of on-chip synthesis include a monodisperse size distribution (polydispersity index (sigma) values of <5%) with consistent stability and uniform drug loading. Photolithography techniques are applied to fabricate novel PDMS-based microfluidic devices that feature a combined dual hydrodynamic flow-focusing region and expanding nozzle geometry with a narrow orifice. Spherical vehicles are formed through flow-focusing by the self-assembly of phospholipids to a lipid layer around the gas core, followed by a shear-induced break off at the orifice. The encapsulation of an extra oil layer between the outer lipid shell and inner bubble gaseous core allows the transport of highly hydrophobic and toxic drugs at high concentrations. Doxorubicin (Dox) entrapment is estimated at 15 mg mL(-1) of particles packed in a single ordered layer. In addition, the attachment of targeting ligands to the lipid shell allows for direct vehicle binding to cancer cells. Preliminary acoustic studies of these monodisperse gas lipospheres reveal a highly uniform echo correlation of greater than 95%. The potential exists for localized drug concentration and release with ultrasound energy.