Tae-Sik Jang, Seong Je Park, Ji Eun Lee, Jeongho Yang, Suk-Hee Park, Martin Byung-Guk Jun, Young Won Kim, Clodualdo Aranas, Joon Phil Choi, Yu Zou, Rigoberto C. Advincula, Yufeng Zheng, Hae Lin Jang, Nam-Joon Cho, Hyun-Do Jung,* and Sang Hoon Kim*

T.-S. Jang
Department of Materials Science and Engineering Chosun University Gwangju 61452, Republic of Korea
S. J. Park
Department of Mechanical Design Engineering Hanyang University Seoul 04763, Republic of Korea
S. J. Park, S. H. Kim
Advanced Joining and Additive Manufacturing R&D Department Korea Institute of Industrial Technology Siheung, Gyeonggi-do 15014, Republic of Korea
J. E. Lee
Advanced Textile R&D Department Korea Institute of Industrial Technology Ansan, Gyeonggi-do 15588, Republic of Korea
J. Yang, S.-H. Park
School of Mechanical Engineering Pusan National University Busan 46241, Republic of Korea
M. B.-G. Jun, Y. W. Kim
School of Mechanical Engineering Purdue University West Lafayette, IN 47907, USA
C. Aranas
Department of Mechanical Engineering University of New Brunswick Fredericton, New Brunswick E3B 5A3, Canada
J. P. Choi
Department of 3D Printing Korea Institute of Machinery & Materials Daejeon 34103, Republic of Korea
Y. Zou
Department of Materials Science and EngineeringUniversity of TorontoToronto, Ontario M5S 3E4, Canada
R. C. Advincula
Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland, OH 44106, USA
R. C. Advincula
Department of Chemical and Biomolecular Engineering and  Joint Institute for Advanced Materials University of Tennessee Knoxville, TN 37996, USA
R. C. Advincula
Center for Nanophase Materials and Sciences Oak Ridge National Laboratory Oak Ridge, TN 37830, USA
Y. Zheng
School of Materials Science and Engineering Peking UniversityBeijing 100871, China
H. L. Jang
Center for Engineered Therapeutics Department of Medicine and Orthopedic Surgery Brigham and Women’s Hospital Harvard Medical SchoolBoston, MA 02115, USA
N.-J. Cho
School of Materials Science and EngineeringNanyang Technological UniversitySingapore 637553, Singapore
H.-D. Jung
Department of Biotechnology The Catholic University of KoreaBucheon, Gyeonggi-do 14662, Republic of Korea
H.-D. Jung
Department of Biomedical and Chemical Engineering (BMCE)The Catholic University of KoreaBucheon, Gyeonggi-do 14662, Republic of Korea

T.-S.J.  and  S.J.P.  contributed  equally  to  this  work. 
*Corresponding authors: Hyun-Do Jung and Sang Hoon Kim

Orthopedic implants should have sufficient strength and promote bone tissue regeneration. However, most conventional implants are optimized for use either under high mechanical load or for active osseointegration. To achieve the dual target of mechanical durability and biocompatibility, polyether ether ketone (PEEK) filaments reinforced with internal titanium dioxide (TiO₂) nanoparticles via dopamine-induced polymerization are additively manufactured into an orthopedic implant through material extrusion (ME). The exterior of the PEEK/TiO₂ composite is coated with hydroxyapatite (HA) using radiofrequency (RF) magnetron sputtering to increase both the strength and biocompatibility provided by homogeneous ceramic–ceramic interactions and the protuberant nanoscale topography between the internal TiO₂ nanoparticle reinforcement and external HA coating. The hardness, tensile, and compression, and scratch test results demonstrate a considerable enhancement in the mechanical strength of the hierarchical PEEK/TiO2/HA hybrid composite structure compared to that of the conventional 3D-printed PEEK. Furthermore, PEEK with internal TiO₂ reinforcement improves the proliferation and differentiation of bone cells in vitro, whereas the external HA coating leads to a more prevalent osteoblast absorption. Micro-computed tomography and histological analyses confirm new bone formation and a high bone-to-implant contact ratio on the HA-coated PEEK structure reinforced with TiO₂ nanoparticles.