Antimicrobial peptide A₉K as a gene delivery vector in cancer cells

Designed peptides are promising biomaterials for biomedical applications. The amphiphilic cationic antimicrobial peptide (AMP), A₉K, can self-assemble into nano-rod structures and has shown cancer cell selectivity and could therefore be a promising candidate for therapeutic delivery into cancer cells. In this paper, we investigate the selectivity of A₉K for cancer cell models, examining its effect on two human cancer cell lines, A431 and HCT-116. Little or no activity was observed on the control, human dermal fibroblasts (HDFs). In the cancer cell lines the peptide inhibited cellular growth through changes in mitochondrial morphology and membrane potential while remaining harmless towards HDFs. In addition, the peptide can bind to and protect nucleic acids while transporting them into both 2D cultures and 3D spheroids of cancer cells. A₉K showed high efficiency in delivering siRNA molecules into the centre of the spheroids. A₉K was also explored in vivo, using a zebrafish (Danio rerio) development toxicity assay, showing that the peptide is safe at low doses. Finally, a high-content imaging screen, using RNA interference (RNAi) targeted towards cellular uptake, in HCT-116 cells was carried out. Our findings suggest that active cellular uptake is involved in peptide internalisation, mediated through clathrin-mediated endocytosis. These new discoveries make A₉K attractive for future developments in clinical and biotechnological applications.