CADY

CADY-1 is an amphipathic peptide that possesses cell-penetrating activity. As an amphipathic peptide, CADY-1 is capable of forming complexes by self-assembly, and they are these complexes that possess cell-penetrating activity. This distinct characteristic of CADY-1 makes it a potent cell-penetrating drug delivery system. Doxorubicin is a widely used cytotoxic anti-cancer drug but is limited by its toxicity. Although the liposomal formulation of doxorubicin ameliorates its toxicity, its complicated synthesis remains an obstacle to its wide clinical use. In this study, our findings revealed that CADY-1 and doxorubicin form a stable complex at optimised molar ratios in a self-assembling manner. Formation of the complex extended the blood residence time of doxorubicin in a similar fashion to that of liposomal doxorubicin. In addition, the complex was capable of carrying doxorubicin across the cell membrane, which increased the therapeutic index of doxorubicin. Experimental animals treated with a CADY-1/doxorubicin complex exhibited better tolerance and anti-tumour activity than animals treated with either liposomal doxorubicin or the free form of doxorubicin. Collectively, the findings in this study support the advantages of using complexes formed by the self-assembled peptide CADY-1 and suggest that CADY-1 is a potent drug delivery system.

Although siRNA consist in very promising therapeutics, their clinical development is limited by several biological barriers including low cellular permeability, poor stability and lack of tissue specificity. Therefore the Achilles' heel for siRNA-based therapy is directly related to the lack of efficient system to promote their delivery. During the last two decades, cell-penetrating peptides (CPPs) have been widely developed to enhance the cellular delivery of therapeutics. In this context we have elaborated a new strategy based on self-assembling peptide-based nanoparticles. The CADY peptide is a 20-residue secondary amphipathic peptide which is able to spontaneously self associate with siRNA with a strong affinity, by combining both electrostatic and hydrophobic interactions, to form stable nanoparticles. Investigations of both physico-chemical properties and cellular siRNA delivery revealed that the CADY/siRNA complexes were able to enter a wide variety of cell lines by a mechanism independent of any endocytotic pathway. In addition a deeper understanding of the self assembly of CADY molecules around siRNA leads to a "raspberry"-like nanoparticle architecture which provides new perspectives for the CADY/siRNA formulations. Finally the robustness of the biological response infers that peptide-based nanoparticle technology holds a strong promise for therapeutic applications. The present review deals with most of the biophysical characteristics as well as the cellular mechanism and cellular applications of CADY/siRNA nanoparticles.

Cell-penetrating peptides (CPPs) constitute a family of peptides with the characteristic ability to cross biological membranes and deliver cargo into the intracellular milieu. Several CPPs have been proposed for delivery of polypeptides and proteins into cells through either of two strategies: covalent or complexed in a non-covalent fashion. Members of the PEP family are primary amphipathic peptides which have been shown to deliver peptides and proteins into a wide variety of cells through formation of non-covalent complexes. CADY is a secondary amphipathic peptide which has been demonstrated to deliver short nucleic acids, in particular siRNA with high efficiency. Here we review the characteristics of the PEP and CADY carriers and describe a novel derivative of CADY termed CADY2, which also presents sequence similarities to Pep1. We have compared Pep1, CADY and CADY2 in their efficiency to interact with and internalize short fluorogenic peptides and proteins into cultured cells, and provide evidence that CADY2 can interact with proteins and peptides and deliver them efficiently into living cells, similar to Pep1, but in contrast to CADY which is unable to deliver any peptide, even short negatively charged peptides. This is the first study to investigate the influence of the cargo on the interactions between PEP and CADY carriers, thereby providing novel insights into the physicochemical parameters underlying interactions and cellular uptake of peptides and proteins by these non-covalent CPPs.