Interface-Engineered PVA/PAA Composite Hydrogel Coatings on Bioinspired 3D-Printed PEEK Bilayers for Lubrication and Diclofenac Delivery

Retaining a lubricating, drug-delivering hydrogel on a load-supporting implant requires coordinated scaffold and interface design. We developed an osteochondral-inspired poly(ether ether ketone) (PEEK)/hydrogel bilayer by continuous 3D printing and surface modification. A dense PEEK base supports a porous upper region containing a poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) composite hydrogel. Sulfonation and ultraviolet-assisted acrylic acid (AA) treatment prepare the substrate for hydrogel attachment. At a 4:1 PVA:AA feed mass ratio, the drug-free composite construct (gPCH) exhibited a maximum detachment force per unit width of 304.60 ± 7.20 N m−1, 2.39 times that of PVA on sulfonated PEEK without AA/UV treatment. Its friction coefficient was 0.073 ± 0.005 during a 10 min screening test under 2 N in 25% fetal bovine serum at room temperature. The diclofenac sodium (DFN)-loaded counterpart (gPCHD) released 73.92 ± 3.24% of DFN over 72 h in PBS at 37 °C. In lipopolysaccharide-stimulated rabbit bone marrow-derived mesenchymal stem cells, gPCHD showed lower COX-1, COX-2, and IL-6 mRNA expression than composition-matched, drug-free gPCH. Twelve-week rabbit histology (n = 3 per group) provided descriptive observations of tissue contact and a retained hydrogel-bearing layer. This architecture–interface design integrates structural support, interfacial retention, short-duration lubrication, and drug delivery; long-term tribological performance and component-specific in vivo effects remain to be established.