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Rosa Bellavita,1,* Marialuisa Piccolo,1,* Linda Leone,2 Maria Grazia Ferraro,1,3 Principia Dardano,4 Luca De Stefano,4 Flavia Nastri,2 Carlo Irace,1 Annarita Falanga,5 Stefania Galdiero1,* 1Department of Pharmacy, School of Medicine, University of Naples ‘Federico II’, Napoli, Italy; 2Department of Chemical Sciences, University of Napoli “Federico II”, Naples, Italy; 3School of Infection and Immunity, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK; 4Institute of Applied Sciences and Intelligent Systems, Consiglio Nazionale delle Ricerche, Naples, Italy; 5Department of Agricultural Science, University of Naples “Federico II”, Portici, Italy*These authors contributed equally to this workCorrespondence: Stefania Galdiero, Email stefania.galdiero@unina.itIntroduction: The design of delivery tools that efficiently transport drugs into cells remains a major challenge in drug development for most pathological conditions. Triple-negative breast cancer (TNBC) is a very aggressive subtype of breast cancer with poor prognosis and limited effective therapeutic options.Purpose: In TNBC treatment, chemotherapy remains the milestone, and doxorubicin (Dox) represents the first-line systemic treatment; however, its non-selective distribution causes a cascade of side effects. To address these problems, we developed a delivery platform based on the self-assembly of amphiphilic peptides carrying several moieties on their surfaces, aimed at targeting, enhancing penetration, and therapy.Methods: Through a single-step self-assembly process, we used amphiphilic peptides to obtain nanofibers decorated on their surfaces with the selected moieties. The surface of the nanofiber was decorated with a cell-penetrating peptide (gH625), an EGFR-targeting peptide (P22), and Dox bound to the cleavage sequence selectively recognized and cleaved by MMP-9 to obtain on-demand drug release. Detailed physicochemical and cellular analyses were performed.Results: The obtained nanofiber (NF-Dox) had a length of 250 nm and a diameter of 10 nm, and it was stable under dilution, ionic strength, and different pH environments. The biological results showed that the presence of gH625 favored the complete internalization of NF-Dox after 1h in MDA-MB 231 cells, mainly through a translocation mechanism. Interestingly, we observed the absence of toxicity of the carrier (NF) on both healthy cells such as HaCaT and TNBC cancer lines, while a similar antiproliferative effect was observed on TNBC cells after the treatment with the free-Dox at 50 μM and NF-Dox carrying 7.5 μM of Dox.Discussion: We envision that this platform is extremely versatile and can be used to efficiently carry and deliver diverse moieties. The knowledge acquired from this study will provide important guidelines for applications in basic research and biomedicine. Keywords: self-assembling peptides, triple negative breast cancer, nanofiber, on-demand strategy, doxorubicin

The two crystals of the terminally blocked sequential peptides, L-proline-alpha-aminoisobutyric acid (L-Pro-Aib)n, have been characterized at atomic resolution using X-ray diffraction. The sequential L-Pro-Aib dipeptide units exhibit an asymmetric 3(sub 10)-helix type with a right-handed beta-bend ribbon spiral configuration which is stabilized by intramolecular H-bonds between the N-H groups of the Aib fragments and the C=O groups of the pBrB- moiety and of the Pro fragments.