Additively manufactured gradient porous Ti–6Al–4V hip replacement implants embedded with cell-laden gelatin methacryloyl hydrogels

May 10, 2021

Elham Davoodi (1,2,3,4), Hossein Montazerian (2,3,4), Reza Esmaeilizadeh (1), Ali-Cheloee Darabi (5), Armin Rashidi (6), Javad Kadkhodapour (5), Hamid Jahed (1), Mina Hoorfar (6), Abbas S. Milani (6), Paul S. Weiss (2,3,7,8), Ali Khademhosseini (2,3,4), Ehsan Toyserkani (1)
ACS Applied Materials & Interfaces, 13, May 2021: 22110−22123. DOI: 10.1021/acsami.0c20751


additive manufacturing; laser powder-bed fusion; Ti−6Al−4V; TPMS; mechanical properties; permeability; triply periodic minimal surfaces


Laser additive manufacturing has led to a paradigm shift in the design of next-generation customized porous implants aiming to integrate better with the surrounding bone. However, conflicting design criteria have limited the development of fully functional porous implants; increasing porosity improves body fluid/cell-laden prepolymer permeability at the expense of compromising mechanical stability. Here, functionally gradient porosity implants and scaffolds designed based on interconnected triply periodic minimal surfaces (TPMS) are demonstrated. High local porosity is defined at the implant/tissue interface aiming to improve the biological response. Gradually decreasing porosity from the surface to the center of the porous constructs provides mechanical strength in selective laser melted Ti−6Al−4V implants. The effect of unit cell size is studied to discover the printability limit where the specific surface area is maximized. Furthermore, mechanical studies on the unit cell topology effects suggest that the bending-dominated architectures can provide significantly enhanced strength and deformability, compared to stretching-dominated architectures. A finite element (FE) model developed also showed great predictability (within ∼13%) of the mechanical responses of implants to physical activities. Finally, in vitro biocompatibility studies were conducted for two-dimensional (2D) and threedimensional (3D) cases. The results of the 2D in conjunction with surface roughness show favored physical cell attachment on the implant surface. Also, the results of the 3D biocompatibility study for the scaffolds incorporated with a cell-laden gelatin methacryloyl (GelMA) hydrogel show excellent viability. The design procedure proposed here provides new insights into the development of porous hip implants with simultaneous high mechanical and biological responses.

How Our Software Was Used

Dragonfly was used for image processing and porosity analysis.

Author Affiliation

(1) Mechanical and Mechatronics Engineering Department, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
(2) Department of Bioengineering, University of California, Los Angeles, 410 Westwood Plaza, Los Angeles, California 90095, United States.
(3) California NanoSystems Institute (CNSI), University of California, Los Angeles, 570 Westwood Plaza, Los Angeles, California 90095, United States.
(4) Terasaki Institute for Biomedical Innovation, Los Angeles, California 90024, United States.
(5) Institute for Materials Testing, Materials Science and Strength of Materials, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany.
(6) School of Engineering, University of British Columbia, 3333 University Way, Kelowna, British Columbia V1V 1V7, Canada.
(7) Department of Chemistry & Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095, United States.
(8) Department of Materials Science and Engineering, University of California, Los Angeles, 410 Westwood Plaza, Los Angeles, California 90095, United States.