4D printing of biocompatible, hierarchically porous shape memory polymeric structures

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Biomedical Engineering

Background:

• Conventional biomedical implants face limitations such as a one-size-fits-all design, need for monitoring, and risk of immune rejection.
• 4D printing offers a solution for creating personalized, shape-changing implants, but suitable materials with appropriate properties are lacking.
• Shape memory polymers (SMPs) are promising for 4D printing, but existing options often have suboptimal glass transition temperatures (T_g), biocompatibility, or mechanical properties for soft tissue integration.

Purpose of the Study:

• To develop a novel 4D printable shape memory polymer (SMP) with tailored properties for biomedical applications.
• To engineer hierarchically porous structures within the SMP to enhance biological activity and tissue integration.
• To demonstrate the feasibility of creating complex, personalized implant shapes using the developed material and 4D printing technique.

Main Methods:

• Synthesis and characterization of Poly(glycerol dodecanoate) acrylate (PGDA) as the base SMP material.
• Utilizing porogen leaching to create hierarchically porous textures within the 3D printed PGDA structures.
• Employing 4D printing to fabricate complex geometries and evaluating the material's shape memory effect (SME), mechanical properties, and cytocompatibility.

Main Results:

• The developed porous PGDA exhibited a glass transition temperature (T_g) of 35.6 °C and a Young's Modulus of 0.31–1.22 MPa, closely matching soft biological tissues.
• A one-way shape memory effect (SME) with shape fixity and recovery ratios exceeding 98% was achieved, indicating reliable shape-changing capabilities.
• Cell cultures demonstrated a survival rate over 90%, confirming the cytocompatibility of the porous SMP scaffolds.
• Complex 3D structures, including overhanging and tilted designs, were successfully printed, showcasing the versatility of the 4D printing approach.

Conclusions:

• This work presents a novel method for creating hierarchically porous shape memory scaffolds using 4D printing with PGDA.
• The developed scaffolds possess an optimal T_g for minimally invasive implantation and tunable mechanical properties suitable for soft tissue applications.
• The combination of engineered porosity, excellent shape memory performance, and cytocompatibility makes these scaffolds highly promising for advanced biomedical implants.