Tuning the Mechanical Properties of Recombinant Protein-Stabilized Gas Bubbles Using Triblock Copolymers

Gas bubbles enhance contrast in ultrasound sonography and can also carry and deliver therapeutic agents. The mechanical properties of the bubble shell play a critical role in determining the physical response of gas bubbles under ultrasound insonation. Currently, few methods allow for tailoring of the mechanical properties of the stabilizing layers of gas bubbles. Here, we demonstrate that blending of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic triblock copolymer with a recombinant protein, oleosin, enables the tuning of the mechanical properties of the bubble stabilizing layer. The areal expansion modulus of gas bubbles, as determined by micropipette aspiration, depends on the structure as well as the concentration of PEO-PPO-PEO triblock copolymers. We believe our method of using a mixture of PEO-PPO-PEO and oleosin can potentially lead to the formation of microbubbles with stabilizing shells that can be functionalized and tailored for specific applications in ultrasound imaging and therapy.