•Fabricated FibraValves that maintained unidirectional blood flow in vivo•Demonstrated focused rotary jet spinning as medical implant fabrication platform•Manufactured micro- and nanofiber scaffolds that mimic native valve mechanics•Spun fiber-based heart valve replacements in minutes Children worldwide suffer from heart valve disease and often require open heart surgeries for valve replacements. Unfortunately, current heart valve replacements do not grow alongside the child, necessitating repeat high-risk surgeries throughout the pediatric patient’s life. This work introduces FibraValves, heart valve replacements fabricated in minutes that comprise of fibers produced by focused rotary jet spinning. FibraValves are manufactured using biodegradable polymer fibers that allow for the patient’s cells to attach and remodel the implanted scaffold, eventually building a native valve that can grow and live with the child throughout their life. These valves were tested in vitro and deployed in acute in vivo studies to evaluate their ability to maintain unidirectional blood flow in the heart. Together, these results suggest the potential translation of FibraValves as future cardiac implants, eliminating the need for repeated valve replacements in children. Pediatric heart valve disease affects children worldwide and necessitates valve replacements that remodel and grow with the patient. Current valve manufacturing technologies struggle to create valves that facilitate native tissue remodeling for permanent replacements. Here, we present focused rotary jet spinning (FRJS) for implantable medical devices, such as heart valves, to address this challenge. Combining RJS and a focused air stream, FRJS prints FibraValves, micro- and nanofibrous heart valves, in minutes. The micro- and nanoscale features provide structural cues to orient cells at the biotic-abiotic interface, while the centimeter-scale valve shape regulates cardiac flow. We built valves using poly(L-lactide-co-Ɛ-caprolactone) fiber scaffolds, which supported rapid cellular infiltration and displayed native valve-like mechanical properties. Evaluating clinical translatability, we assessed acute performance in a large animal model using a transcatheter delivery approach. These tests indicate that FRJS is a viable method for manufacturing heart valves and future medical implants. Pediatric heart valve disease affects children worldwide and necessitates valve replacements that remodel and grow with the patient. Current valve manufacturing technologies struggle to create valves that facilitate native tissue remodeling for permanent replacements. Here, we present focused rotary jet spinning (FRJS) for implantable medical devices, such as heart valves, to address this challenge. Combining RJS and a focused air stream, FRJS prints FibraValves, micro- and nanofibrous heart valves, in minutes. The micro- and nanoscale features provide structural cues to orient cells at the biotic-abiotic interface, while the centimeter-scale valve shape regulates cardiac flow. We built valves using poly(L-lactide-co-Ɛ-caprolactone) fiber scaffolds, which supported rapid cellular infiltration and displayed native valve-like mechanical properties. Evaluating clinical translatability, we assessed acute performance in a large animal model using a transcatheter delivery approach. These tests indicate that FRJS is a viable method for manufacturing heart valves and future medical implants. Congenital and rheumatic heart disease are significant pediatric health issues, affecting roughly 12 million and 40 million children, respectively.1Kumar R.K. Antunes M.J. Beaton A. Mirabel M. Nkomo V.T. Okello E. Regmi P.R. Reményi B. Sliwa-Hähnle K. 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Similarly, 3D printing approaches offer highly customizable and reproducible valve geometries33Jana S. Lerman A. Bioprinting a cardiac valve.Biotechnol. Adv. 2015; 33: 1503-1521https://doi.org/10.1016/j.biotechadv.2015.07.006Google Scholar,37Maxson E.L. Young M.D. Noble C. Go J.L. Heidari B. Khorramirouz R. Morse D.W. Lerman A. In vivo remodeling of a 3D-Bioprinted tissue engineered heart valve scaffold.Bioprinting. 2019; 16e00059https://doi.org/10.1016/j.bprint.2019.e00059Google Scholar but are unable to replicate the micro- and nanoscale features of valve scaffolds due to the trade-off between print resolution and production rate.38Chang H. Liu Q. Zimmerman J.F. Lee K.Y. Jin Q. Peters M.M. Rosnach M. Choi S. Kim S.L. Ardoña H.A.M. et al.Recreating the heart’s helical structure-function relationship with focused rotary jet spinning.Science. 2022; 377: 180-185https://doi.org/10.1126/SCIENCE.ABL6395Google Scholar For fiber spinning techniques, electrospinning is commonly used to produce micro- and nanofiber sheets as ECM analogs.27Kluin J. Talacua H. Smits A.I.P. Emmert M.Y. Brugmans M.C.P. Fioretta E.S. Dijkman P.E. Söntjens S.H.M. Duijvelshoff R. Dekker S. et al.In situ heart valve tissue engineering using a bioresorbable elastomeric implant - from material design to 12 months follow-up in sheep.Biomaterials. 2017; 125: 101-117https://doi.org/10.1016/j.biomaterials.2017.02.007Google Scholar,30Uiterwijk M. Smits A.I.P. van Geemen D. van Klarenbosch B. Dekker S. Cramer M.J. van Rijswijk J.W. Lurier E.B. Di Luca A. Brugmans M.C.P. et al.In situ remodeling overrules bioinspired scaffold architecture of supramolecular elastomeric tissue-engineered heart valves.JACC. Basic Transl. 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Weber B. et al.JetValve: rapid manufacturing of biohybrid scaffolds for biomimetic heart valve replacement.Biomaterials. 2017; 133: 229-241https://doi.org/10.1016/j.biomaterials.2017.04.033Google Scholar to address this issue; however, there were remaining improvements to be made in the manufacturing, fiber material, and valve geometrical design. In this study, we sought to overcome these limitations by developing focused rotary jet spinning (FRJS)38Chang H. Liu Q. Zimmerman J.F. Lee K.Y. Jin Q. Peters M.M. Rosnach M. Choi S. Kim S.L. Ardoña H.A.M. et al.Recreating the heart’s helical structure-function relationship with focused rotary jet spinning.Science. 2022; 377: 180-185https://doi.org/10.1126/SCIENCE.ABL6395Google Scholar for on-demand fabrication of customizable, native-like 3D heart valves. This system exploits centrifugal forces and focused air flow to engineer synthetic fibers and control their assembly via conformal deposition on a customizable valve collection mandrel. The rapid manufacturing capabilities of FRJS allow for the spinning of micro- and nanofibrous heart valve scaffolds (FibraValves) in less than 10 min, while the conformal collection supports the development of complex macroscale valve-shaped structures. We synthesized and tested a synthetic polymer, poly(L-lactide-co-Ɛ-caprolactone) (PLCL), in heart valve scaffolds, as it displayed native-like mechanical properties and allowed for increased cellular infiltration. Additionally, we investigated FibraValve performance in vitro, evaluating the valve’s ability to regulate cardiac flow, and in vivo, assessing acute performance and functionality in a large-animal model using a transcatheter delivery approach. The use of the PLCL material, facilitating increased cellular infiltration, combined with the conformal deposition capabilities of FRJS enabled improved valve geometrical designs and performance compared with JetValves. These data suggest the effectiveness of FRJS as a manufacturing platform for on-demand production of medical implants. Pulmonary valves are trileaflet valves characterized by a load-bearing micro- and nanofibrous collagen network with leaflet thicknesses of roughly 0.3–0.7 mm40Chester A.H. El-Hamamsy I. Butcher J.T. Latif N. Bertazzo S. Yacoub M.H. The living aortic valve: from molecules to function.Glob Cardiol Sci Pr. 2014; 2014: 52-77https://doi.org/10.5339/gcsp.2014.11Google Scholar (Figure 1A). Valvular function is maintained over millions of cycles due to the tissue’s elastic properties and the leaflets’ curved geometry, which combine to support physiological blood flow.40Chester A.H. El-Hamamsy I. Butcher J.T. Latif N. Bertazzo S. Yacoub M.H. The living aortic valve: from molecules to function.Glob Cardiol Sci Pr. 2014; 2014: 52-77https://doi.org/10.5339/gcsp.2014.11Google Scholar,41Balachandran K. Sucosky P. Yoganathan A.P. 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Effect of solvent evaporation on fiber morphology in rotary jet spinning.Langmuir. 2014; 30: 13369-13374https://doi.org/10.1021/la5023104Google Scholar To improve collection efficiency, the FRJS system employs a focused air jet positioned behind the rotating reservoir to direct the fibers into a focused stream onto the valve-shaped collection mandrel. The valve scaffolds are then embossed (while still on the collection mandrel) to create deeper curvature in the leaflets (Figure S2D). This FibraValve manufacturing process allows for minimal manufacturing steps: (1) mandrel design, (2) fiber scaffold collection, (3) leaflet embossing, and (4) trimming and suturing into a final shape (Figures 1C and S2). Leveraging this manufacturing capability, fibrous pulmonary valve scaffolds can be produced (Figure 1). The seamless collection method allows for the creation of entire valve geometries without reliance on post-processing of flat fiber sheets, which is necessary for other fabrication techniques.12Emmert M.Y. Weber B. Behr L. Sammut S. Frauenfelder T. Wolint P. Scherman J. Bettex D. Grünenfelder J. Falk V. Hoerstrup S.P. Transcatheter aortic valve implantation using anatomically oriented, marrow stromal cell-based, stented, tissue-engineered heart valves: technical considerations and implications for translational cell-based heart valve concepts.Eur. J. Cardio. Thorac. Surg. 2014; 45: 61-68https://doi.org/10.1093/ejcts/ezt243Google Scholar,13Syedain Z.H. Haynie B. Johnson S.L. Lahti M. Berry J. Carney J.P. Li J. Hill R.C. Hansen K.C. Thrivikraman G. et al.Pediatric tri-tube valved conduits made from fibroblast-produced extracellular matrix evaluated over 52 weeks in growing lambs.Sci. Transl. Med. 2021; 13eabb7225https://doi.org/10.1126/scitranslmed.abb7225Google Scholar,16Driessen-Mol A. Emmert M.Y. Dijkman P.E. Frese L. Sanders B. Weber B. Cesarovic N. Sidler M. Leenders J. Jenni R. et al.Transcatheter implantation of homologous “off-the-shelf” tissue-engineered heart valves with self-repair capacity: long-term functionality and rapid in vivo remodeling in sheep.J. Am. Coll. Cardiol. 2014; 63: 1320-1329https://doi.org/10.1016/j.jacc.2013.09.082Google Scholar Processing of these flat sheets includes physical modifications (such as bending, folding, and suturing) that may potentiate discontinuities, inconsistencies in properties such as leaflet shape, and delamination in the prosthesis. Scanning electron micrographs revealed the overall circumferential alignment of the fibers, induced by rotating the collection mandrel (Figure S3). This anisotropic organization mimics the directionality of the load-bearing circumferential collagen network found in the fibrosa layer of the native valve leaflet.31Capulli A.K. Emmert M.Y. Pasqualini F.S. Kehl D. Caliskan E. Lind J.U. Sheehy S.P. Park S.J. Ahn S. Weber B. et al.JetValve: rapid manufacturing of biohybrid scaffolds for biomimetic heart valve replacement.Biomaterials. 2017; 133: 229-241https://doi.org/10.1016/j.biomaterials.2017.04.033Google Scholar,40Chester A.H. El-Hamamsy I. Butcher J.T. Latif N. Bertazzo S. Yacoub M.H. The living aortic valve: from molecules to function.Glob Cardiol Sci Pr. 2014; 2014: 52-77https://doi.org/10.5339/gcsp.2014.11Google Scholar The FibraValve’s circumferential alignment is lower than the anisotropy of the native fibrosa layer. However, the crosshatch fiber assembly ensures biaxial loading capabilities that, in the native valve leaflet, are provided by the ventricularis layer, composed mostly of radially aligned elastin fibers.49Leopold J.A. Cellular mechanisms of aortic valve calcification.Circ. Cardiovasc. Interv. 2012; 5: 605-614https://doi.org/10.1161/CIRCINTERVENTIONS.112.971028Google Scholar After spinning and suturing into a nitinol stent, the valves showed a homogeneous surface without delaminating fibers (Figure 1D). The fiber production capabiliti