Binding and uptake of novel RGD micelles to the α_vβ₃ integrin receptor for targeted drug delivery

Abstract

Purpose: To understand the binding and internalization of novel RGD micelles in tumor cells that overexpress the α_vβ₃ integrin receptor.

Methods: Peptide amphiphiles containing a C16 or C18 fatty-acid chain with one or two ADA units linked to an RGD motif were prepared, characterized, and assessed for their binding specificity to the α_vβ₃ receptor. The internalization of the amphiphiles was evaluated by confocal microscopy and cytotoxicity studies in A2058 cells that overexpress the α_vβ₃ integrin receptor.

Results: The CMC and size and of RGD micelles ranged from 9 to 30 μM and 130 to 300 nm, respectively. Micelles showed good in vitro stability by retaining their micellar integrity and good specificity by binding to the α_vβ₃ integrin receptor in an RGD-dependent manner. Confocal studies showed higher intracellular fluorescence when FITC was delivered through the micelles compared with its free form and showed significantly higher FITC uptake at 37 °C versus 4 °C (p < 0.05). The lower IC50 values were obtained when paclitaxel was delivered to A2058 cells via the RGD-loaded carriers (3.6–4.87 nM) compared with unencapsulated drug (7.86 nM), further demonstrated micelle specificity to the α_vβ₃ receptor.

Conclusion: RGD micelles bound specifically to the α_vβ₃ receptor and their uptake was mediated by an endocytic process.

• Confocal microscopy
• cytotoxicity
• fluorescence polarization
• micelle stability
• receptor-mediated endocytosis
• RGD peptide amphiphile

Acknowledgements

We would like to express our sincere thanks to Dr. Mamoun Alhamadsheh in the Department of Pharmaceutics and Medicinal Chemistry for his guidance with the fluorescence polarization studies and Dr. Lisa Wrischnik in the Department of Biology for her support in using the confocal microscope. This work was supported by the NIH: Grant number 1R15CA108864-01A2.