Search

RALA is a cationic amphipathic peptide which has shown great promise as an efficient, multifunctional delivery system for the delivery of nucleic acids. Rational peptide design was utilised in this study to understand the essential amino acids required for delivery and if any improvements to the RALA peptide could be made. Six amphipathic peptides were synthesised with strategic sequences and amino acid substitutions to reduce peptide sequence, while maintaining the functional characteristics of RALA including amphipathicity, alpha-helicity and pH responsiveness for endosomal escape. Data demonstrated that all six peptides complexed pEGFP-N1 to produce cationic nanoparticles <200 nm in diameter, but not all peptides resulted in successful transfection; indicating the influence of peptide design for cellular uptake and endosomal escape. Pep2, produced nanoparticles with similar characteristics and transfection efficiency to the parent peptide, RALA. However, Pep2 had issues with toxicity and a lack of pH-responsive alpha-helcity. Therefore, RALA remains the superior sequence for non-toxic gene delivery., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Bisphosphonates (BPs) are a class of bone resorptive drug with a high affinity for the hydroxyapatite structure of bone matrices that are used for the treatment of osteoporosis. However, clinical application is limited by a common toxicity, BP-related osteonecrosis of the jaw. There is emerging evidence that BPs possess anticancer potential, but exploitation of these antiproliferative properties is limited by their toxicities. We previously reported the utility of a cationic amphipathic fusogenic peptide, RALA, to traffic anionic nucleic acids into various cell types in the form of cationic nanoparticles. We hypothesized that complexation with RALA could similarly be used to conceal a BP's hydroxyapatite affinity, and to enhance bioavailability, thereby improving anticancer efficacy. Incubation of RALA with alendronate, etidronate, risedronate, or zoledronate provoked spontaneous electrostatic formation of cationic nanoparticles that did not exceed 100 nm in diameter and that were stable over a range of temperatures and for up to 6 h. The nanoparticles demonstrated a pH responsiveness, possibly indicative of a conformational change, that could facilitate release of the BP cargo in the endosomal environment. RALA/BP nanoparticles were more potent anticancer agents than their free BP counterparts in assays investigating the viability of PC3 prostate cancer and MDA-MB-231 breast cancer cells. Moreover, RALA complexation potentiated the tumor growth delay activity of alendronate in a PC3 xenograft model of prostate cancer. Taken together, these findings further validate the use of BPs as repurposed anticancer agents.