{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T22:09:53Z","timestamp":1789682993530,"version":"4.0.1"},"reference-count":53,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T00:00:00Z","timestamp":1780963200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Bioengineering"],"abstract":"<jats:p>Corneal blindness remains a major clinical challenge, yet donor grafts are scarce. Bioprinting has emerged in recent decades to potentially overcome donor shortage. In bioprinting, collagen is a common biomaterial. However, one alternative biomaterial, which has shown promising results in corneal tissue engineering, is keratin. Therefore, human hair keratin was investigated in this study as a bioink component for stroma bioprinting. Two keratin preparations, an aqueous extraction and an alkaline extraction, were incorporated into a methacrylated hyaluronic acid bioink and compared with a collagen methacrylated hyaluronic acid bioink. Corneal stroma-like constructs were printed by extrusion bioprinting and evaluated for optical transmission, biomechanical properties, cell compatibility and protein expression of collagen type I and alpha-smooth muscle actin over a four-week period. Two different cell types, immortalized corneal keratocytes and human corneal fibroblasts, were used. The alkaline keratin dialysate-supplemented bioink showed similar optical transparency and biomechanical properties to the collagen-supplemented bioink. Cell viability was high in all formulations. Protein expression of collagen type I and \u03b1-smooth muscle actin remained low in all bioinks. Human corneal fibroblasts appeared to be in a quiescent state and were unable to produce large amounts of collagen. This comparative study between collagen and keratin is a first step towards establishing keratins in bioprinting, leading to more complex bioinks.<\/jats:p>","DOI":"10.3390\/bioengineering13060670","type":"journal-article","created":{"date-parts":[[2026,6,11]],"date-time":"2026-06-11T05:50:58Z","timestamp":1781157058000},"page":"670","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Keratin-Laden Bioink for Corneal Stroma Bioprinting"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-0256-9512","authenticated-orcid":false,"given":"Leon","family":"Balters","sequence":"first","affiliation":[{"name":"Institute of Pharmaceutical Technology and Biopharmaceutics, Technische Universit\u00e4t Braunschweig, 38106 Braunschweig, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8344-9070","authenticated-orcid":false,"given":"Stephan","family":"Reichl","sequence":"additional","affiliation":[{"name":"Institute of Pharmaceutical Technology and Biopharmaceutics, Technische Universit\u00e4t Braunschweig, 38106 Braunschweig, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"190","DOI":"10.4103\/ijo.IJO_646_17","article-title":"Anatomy of cornea and ocular surface","volume":"66","author":"Sridhar","year":"2018","journal-title":"Indian J. 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