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4D Printing of PLA–PEG–Mg Bio-composites: Shape-Memory Behavior, Degradability, and Biocompatibility

Aghabarari, Roozbeh | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58548 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Alizadeh, Reza
  7. Abstract:
  8. Polylactic acid (PLA) is a promising candidate due to its biocompatibility and printability; however, its relatively high glass transition temperature (Tg) limits activation near body temperature. Here, to lower Tg and enable actuation at a body-safe temperature, 10 wt% polyethylene glycol (PEG) was incorporated into PLA via solvent casting in dichloromethane (DCM) to form a PLA-10PEG matrix. Magnesium particles were then added at 2.5 and 5 wt%. The composites were melt-extruded into filaments and 3D printed as gyroid scaffolds. Differential scanning calorimetry (DSC) confirmed a reduction of Tg to ~44 °C. Cyclic thermomechanical (shape-memory) tests in compression showed near-perfect shape fixity (~100%) for all formulations; notably, PLA-10PEG-2.5Mg achieved the best recovery at 44 °C (Rr ≈ 70%). Long-term performance was assessed by in vitro degradation in phosphate-buffered saline (PBS) over 2, 4, 8, and 12 weeks, accompanied by compressive testing and ¹H NMR spectroscopy to track the decrease in number-average molecular weight and residual PEG in the scaffolds. Cytocompatibility evaluated by the MTT assay indicated that magnesium (especially at 2.5 wt%) enhanced wettability and surface roughness, promoting cell viability and proliferation, whereas 5 wt% Mg led to over-alkalinization of the culture medium and diminished biocompatibility
  9. Keywords:
  10. Shape Memory Polymers ; Scaffold ; Polylactic Acid ; Polyethylene Glycol Polycitric Acid Copolymer ; Fused Deposition Modeling (FDM) ; Four Dimensional Printing

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