Higher Order Architecture of Designer Peptides Forms Bioinspired 10 nm siRNA Delivery System.

The higher-order architecture observed in biological systems, like viruses, is very effective in nucleic acid transport. The replications of this system has been attempted with both synthetic and naturally occurring polymers with mixed results. Here we describe a peptide/siRNA quaternary complex that functions as an siRNA delivery system. The rational design of a peptide assembly is inspired by the viral capsids, but not derived from them. We selected the collagen peptide (COL) to provide the structural stability and the folding framework, and hybridize it with the cell penetrating peptide (CPP) that allows for effective penetration of biological barriers. The peptide/siRNA quaternary complex forms stoichiometric, 10 nm nanoparticles, that show fast cellular uptake (<30 min), effective siRNA release, and gene silencing. The complex provides capsid-like protection for siRNA against nucleases without being immunostimulatory, or cytotoxic. Our data suggests that delivery vehicles based on synthetic quaternary structures that exhibit higher-order architecture may be effective in improving delivery and release of nucleic acid cargo.

Conjugation of Paclitaxel to Hybrid Peptide Carrier and Biological Evaluation in Jurkat and A549 Cancer Cell Lines.

Paclitaxel (PTX) is one of the most potent cancer drugs; however, its low solubility and strong systemic side effects limit its clinical applications. To overcome these issues, new drug formulations and chemical modifications have been proposed. In this study, we present conjugation of PTX to hybrid collagen-cell penetrating peptide (COL-CPP) carriers. The peptide carrier is highly soluble and utilizes a unique stabilization strategy: folding into a triple helix. Here, we report the formation of PTX-COL-CPP prodrug that has similar drug potency as free PTX when tested in Jurkat (human T lymphocyte of acute T cell leukemia) cells but not in A549 (human epithelial of lung carcinoma) cells. Confocal images and flow cytometry show that this behavior originates from lower cellular uptake of COL-CPP and endosomal entrapment of the prodrug in A549, but not in Jurkat cells.

Thermoresponsive Collagen/Cell Penetrating Hybrid Peptide as Nanocarrier in Targeting-Free Cell Selection and Uptake.

The effective delivery of therapeutics and imaging agents to a selected group of cells has been at the forefront of biomedical research. Unfortunately, the identification of the unique cell surface targets for cell selection remains a major challenge, particularly if cells within the selected group are not identical. Here we demonstrate a novel approach to cell section relying on a thermoresponsive peptide-based nanocarrier. The hybrid peptide containing cell-penetrating peptide (CPP) and collagen (COLL) domains is designed to undergo coil-to-helix transition (folding) below physiological temperature. Because only the helical form undergoes effective internalization by the cells, this approach allows effective temperature-discriminate cellular uptake. The cells selected for uptake are locally cooled, thus enabling the carrier to fold and subsequently internalize. Our approach demonstrates a generic method as selected cells could differ from the adjacent cells or could belong to the same cell population. The method is fast (<15 min) and selective; over 99.6% of cells in vitro internalized the peptide carrier at low temperatures (15 °C), while less than 0.2% internalized at 37 °C. In vivo results confirm the high selectivity of the method. The potential clinical applications in mixed cell differentiation carcinoma, most frequently encountered in breast and ovarian cancer, are envisioned.