  Citation: Theodoroula, N.F.; Karavasili, C.; Vlasiou, M.C.; Primikyri, A.; Nicolaou, C.; Chatzikonstantinou, A.V.; Chatzitaki, A.-T.; Petrou, C.; Bouropoulos, N.; Zacharis, C.K.; et al. NGIWY-Amide: A Bioinspired Ultrashort Self-Assembled Peptide Gelator for Local Drug Delivery Applications. Pharmaceutics 2022, 14, 133. https:// doi.org/10.3390/pharmaceutics14010133 Academic Editor: Rakesh Tiwari Received: 11 December 2021 Accepted: 31 December 2021 Published: 6 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). pharmaceutics Article NGIWY-Amide: A Bioinspired Ultrashort Self-Assembled Peptide Gelator for Local Drug Delivery Applications Nikoleta F. Theodoroula 1 , Christina Karavasili 2 , Manos C. Vlasiou 3 , Alexandra Primikyri 4 , Christia Nicolaou 3 , Alexandra V. Chatzikonstantinou 5 , Aikaterini-Theodora Chatzitaki 2 , Christos Petrou 3 , Nikolaos Bouropoulos 6,7 , Constantinos K. Zacharis 8 , Eleftheria Galatou 3 , Yiannis Sarigiannis 3, * , Dimitrios G. Fatouros 2 and Ioannis S. Vizirianakis 1,3, * 1 Department of Molecular Pharmacology, School of Pharmacy, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; theodorn@pharm.auth.gr 2 Department of Pharmaceutical Technology, School of Pharmacy, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; karavasc@pharm.auth.gr (C.K.); chatzita@pharm.auth.gr (A.-T.C.); dfatouro@pharm.auth.gr (D.G.F.) 3 Department of Life & Health Sciences, University of Nicosia, Nicosia 2417, Cyprus; vlasiou.m@unic.ac.cy (M.C.V.); krinikolaou@gmail.com (C.N.); petrou.c@unic.ac.cy (C.P.); galatou.e@unic.ac.cy (E.G.) 4 Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece; a.primikyri@uoi.gr 5 Biotechnology Laboratory, Department of Biological Applications and Technologies, University of Ioannina, 45110 Ioannina, Greece; achatzikonstantinou@uoi.gr 6 Department of Materials Science, University of Patras, 26504 Patras, Greece; nbouro@upatras.gr 7 Foundation for Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes, 26504 Patras, Greece 8 Laboratory of Pharmaceutical Analysis, Department of Pharmaceutical Technology, School of Pharmacy, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; czacharis@pharm.auth.gr * Correspondence: sarigiannis.i@unic.ac.cy(Y.S.); ivizir@pharm.auth.gr (I.S.V.) Abstract: Fibrillar structures derived from plant or animal origin have long been a source of inspira- tion for the design of new biomaterials. The Asn-Gly-Ile-Trp-Tyr-NH 2 (NGIWY-amide) pentapeptide, isolated from the sea cucumber Apostichopus japonicus, which spontaneously self-assembles in water to form hydrogel, pertains to this category. In this study, we evaluated this ultra-short cosmetic bioinspired peptide as vector for local drug delivery applications. Combining nuclear magnetic resonance, circular dichroism, infrared spectroscopy, X-ray diffraction, and rheological studies, the synthesized pentapeptide formed a stiff hydrogel with a high β-sheet content. Molecular dynamic simulations aligned well with scanning electron and atomic-force microscopy studies, revealing a highly filamentous structure with the fibers adopting a helical-twisted morphology. Model dye localization within the supramolecular hydrogel provided insights on the preferential distribution of hydrophobic and hydrophilic compounds in the hydrogel network. That was further depicted in the diffusion kinetics of drugs differing in their aqueous solubility and molecular weight, namely, doxorubicin hydrochloride, curcumin, and octreotide acetate, highlighting its versatility as a delivery vector of both hydrophobic and hydrophilic compounds of different molecular weight. Along with the observed cytocompatibility of the hydrogel, the NGIWY-amide pentapeptide may offer new approaches for cell growth, drug delivery, and 3D bioprinting tissue-engineering applications. Keywords: ultra-short peptides; smart materials; NGIWY-amide; self-assembled peptide hydrogels; drug delivery; sea cucumber 1. Introduction Ultra-short peptide hydrogels, with two to seven amino acids, have gained the interest of scientists due to their involvement in important biological processes [1]. In addition to their advances in therapeutics [2], they are used in advanced nano-supramolecular Pharmaceutics 2022, 14, 133. https://doi.org/10.3390/pharmaceutics14010133 https://www.mdpi.com/journal/pharmaceutics