Insulin crystals grown in short peptide supramolecular hydrogels show enhanced thermal stability and slower release profile. Álvarez Cienfuegos Rodríguez, Luis Insulin composite crystals Protein therapeutics Protein therapeutics have a major role in medicine, being used to treat diverse pathologies. Their three-dimensional structures offer high specificity and lower toxicity than small organic compounds but also make them less stable limiting their in vivo half-life. Protein-analogs obtained by recombinant DNA technology or by chemical modification and / or the use of drug delivery vehicles have been developed to improve or modulate the in vivo pharmacological activity of proteins. Nevertheless, strategies to improve the shelf-life of protein pharmaceuticals have been less explored which challenge the preservation of their activity. Herein, we present a methodology that simultaneously increases the stability of proteins and modulates the release profile, and implemented with human insulin as a proof of concept. Two novel thermally stable insulin composite crystal formulations intended for the therapeutic treatment of diabetes are reported. These composite crystals have been obtained by crystallizing insulin in agarose and Fmoc-AA (fluorenylmethoxycarbonyl-dialanine) hydrogels. This process affords composite crystals, in which, hydrogel fibers are occluded inside the crystals. Insulin in both crystalline formulations remains unaltered at 50 C for 7 days. Differential Scanning Calorimetry, High Performance Liquid Chromatography, mass spectrometry and in vivo studies have shown that insulin does not degrade after the heat treatment. The nature of the hydrogel modifies the physicochemical properties of the crystals. Crystals grown in Fmoc-AA hydrogel are more stable and have a slower dissolution rate than crystals grown in agarose. This methodology paves the way for the development of more stable protein pharmaceuticals overcoming some of the exiting limitations. 2021-03-26T12:08:49Z 2021-03-26T12:08:49Z 2021 journal article ACS Appl. Mater. Interfaces https://dx.doi.org/10.1021/acsami.1c00639 http://hdl.handle.net/10481/67738 10.1021/acsami.1c00639 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ open access Atribución-NoComercial-SinDerivadas 3.0 España ACS