Tailoring degradation of PLA/Mg/PEG bone scaffolds through triply periodic minimal surface (TPMS) diamond architectures (Uniform vs graded) using fused filament fabrication (FFF) additive manufacturing

Matching scaffold degradation to the pace of bone regeneration remains challenging, particularly for polymer–metal composites where composition and pore architecture jointly influence fluid transport, local reactions, and structural integrity. This study investigates the degradation behaviour of Diamond-type triply periodic minimal surface (TPMS) scaffolds fabricated by fused filament fabrication (FFF) from PLA/Mg/PEG biocomposite filaments. Uniform and functionally graded structures (FGS) with a fixed global porosity of 50% were compared while varying magnesium (3–10 wt%) and polyethylene glycol (3–7.5 wt%) contents. Scaffolds were immersed in polyethylene glycol (PBS) (pH 7.4, 37 °C) for 3 months, with weekly pH monitoring and monthly mass-loss measurements. Mass loss increased with Magnesium (Mg) and polyethylene glycol (PEG) content, ranging from 10.00 ± 17.42% for FGS-1 (94/3/3 wt%) to 50.30 ± 5.35% for FGS-9 (82.5/10/7.5 wt%) after 3 months. One-way analysis of variance (ANOVA) showed significant differences among scaffold groups at month 3 (p = 0.0049), while the graded scaffold exhibited significantly greater mass loss than the uniform scaffold at identical composition (50.30 ± 5.35% vs. 22.01 ± 9.68%, p = 0.0197). Weekly pH profiles showed an initial alkaline shift followed by fluctuations near neutral to slightly alkaline values. SEM, cross-sectional morphology, XRD, and FTIR analyses revealed greater structural disruption and stronger corrosion- and phosphate-related signals in graded scaffolds. These findings indicate that TPMS pore grading promotes controlled degradation and represents an effective design strategy for tailoring PLA/Mg/PEG bone scaffold performance.