Polymer-lipid microbubbles for biosensing and the formation of porous structures.

Polymer-lipid microbubbles (PLBs) are generated by microfluidic flow-focusing devices to form a new class of long-lasting hybrid particles. The specific PLB construct developed is an elastic gas-filled microsphere with a polydimethylsiloxane (PDMS) shell containing phospholipids conjugated to functionalized polyethyleneglycol (PEG). Digital "droplet-based" microfluidics technology enables control of particle composition, size, and polydispersity (sigma<10%). Use of PDMS as a shell component improves the functionality and stability (lifetime>6 months) of the hybrid particles due to the thermally maneuverable solidification process. With a gas core, they serve as a template material for creating three-dimensional porous structures and surfaces, requiring no cumbersome post-processing removal steps. By adding biotinylated PEG-lipid derivatives that offer targeting capabilities, we demonstrate the immobilization of fluorescent IgG antibodies on stationary PDMS-lipid microbubbles through biotin-avidin interactions and on-chip trapping for immunoassays. A PDMS-lipid composition offers several advantages such as biocompatibility and biodegradability for future in vivo use as porous engineered scaffolds, packing materials, or delivery (e.g. therapeutic) agents with cell targeting capability.