**Targeted Microbubbles - Design**


Fig. 6. Depicts a targeted microbubble. The cyclo-CRGDC analog is attached to a lipid anchor via a PEG spacer to form a bioconjugate. The bioconjugate comprises about from about 0.1 to 5 mole percent of the lipid coating the microbubble. There is additional PEG'ylated lipid from about 5-10 mole percent in the lipid coating the microbubble.

Fig. 7. Depicts a targeted cationic microbubble binding DNA. The bioconjugates are designed to bind to endothelial epitopes upregulated in disease. The microbubble can be followed and monitored by ultrasound imaging and activated with ultrasound energy for local delivery.

**Targeted Microbubbles - Design**

• Anchor: lipid

• Ligand: pep de

• Tether: PEG

Fig. 6. Depicts a targeted microbubble. The cyclo-CRGDC analog is attached to a lipid anchor via a PEG spacer to form a bioconjugate. The bioconjugate comprises about from about 0.1 to 5 mole percent of the lipid coating the microbubble. There is additional PEG'ylated lipid from about 5-10 mole percent in the lipid coating the microbubble.

**Ligand**

CRGDWPC

**Anchor Tether**

Fig. 7. Depicts a targeted cationic microbubble binding DNA. The bioconjugates are designed to bind to endothelial epitopes upregulated in disease. The microbubble can be followed and monitored by ultrasound imaging and activated with ultrasound energy for

local delivery.

clinically translatable. A maleimide labeled spacer might be affixed to the microbubble and the nanoparticles might be thiolated to covalently bind the nanoparticle to the surface of the microbubbles in a potentially biocompatible manner. Another approach would be to use electrostatic interaction between the nanoparticle and the surface of the microbubbles but this must be optimized to ensure that the DNA is bound until it reaches the target site. Note also that if the bubble has excess cationic charge this may adversely affect biodistribution. Note also that it is more difficult to bind low molecular weight genetic material such as si-RNA using merely electrostatic interaction.

Fig. 8. Depicts a unique microbubble construct for gene delivery. The parent microbubble is PEG'ylated but the DNA (or siRNA) is condensed into nanoparticles that are bound to the surface of the microbubble. The nanoparticles have targeting ligands to bind to cell specific epitopes. Note also that the construct could be modified to comprise endothelial targeting moieties on the microbubble so that the microbubble could bind to endothelial epitopes.
