Enhanced Cell Killing by Paclitaxel-Loaded Recombinant Protein Micelles Bearing Integrin-Binding and Cell-Penetrating Peptides.

Peptide ligands are effective and specific vectors that can target cell surface receptors, and have shown great potential for targeting drug delivery vehicles. Often, materials used as drug delivery matrices are chemically synthesized and difficult to functionalize, which compromises their development as smart drug carriers. Here, we assemble carriers from a recombinant protein as a novel approach to overcome these limitations. We have previously shown that oleosin, a natural surfactant protein, can be engineered to self-assemble into spherical micelles, and that functionalizing oleosin with RGDS can increase cellular uptake in integrin bearing cells. Here, we investigated whether we could further enhance cellular uptake by incorporating either a RGDS synergy peptide PHSRN or a cell-penetrating Tat peptide derived from human immunodeficiency virus (HIV). The resulting modified oleosins self-assemble into spherical micelles in aqueous environments. Spherical micelles made from oleosin can effectively encapsulate the hydrophobic chemotherapeutic drug paclitaxel (PX). After 15 h, 350 nM PX loaded oleosin micelles equipped with both RGDS and Tat increased cell killing by 2-fold compared to free paclitaxel, and 1.2-fold compared to micelles made from RGD-oleosin alone. Micelles equipped with PHSRN alone do not facilitate cell killing compared to free paclitaxel, whereas micelles equipped with both PHSRN and RGDS increased cell killing by 1.1-fold compared to micelles with RGDS alone in 15 h. Therefore, incorporating multiple motifs into oleosin is an approach for making a versatile drug delivery carrier.