Ultrasound contrast agents targeted to malignancies: optimizing cellular attachment

Hollow poly (lactic acid) (PLA) microcapsules were modified with Arg-Gly-Asp (RGD) peptide to create a targeted contrast agent (CA) that enhances ultrasound imaging. The RGD peptide targets cell-surface receptors (integrins α_vβ₃ and α_vβ₅) which are overexpressed in cancer and angiogenesis. The influence of RGD surface density and RGD spacer length were evaluated for their contribution to CA attachment to human breast cancer cells. The CA performance was dependent on both the RGD surface density and glycine spacer length and therefore should be considered in the design of a site-targeted CA. The optimized RGD peptide modified microcapsules are ideal candidates for targeted diagnostic imaging and for drug delivery.