A Biocompatible 4D Printing Shape Memory Polymer as Emerging Strategy for Fabrication of Deployable Medical Devices.

The rapid development of 4D printing provides a potential strategy for the fabrication of deployable medical devices (DMD). The minimally invasive surgery to implant the DMD into the body is critical, 4D printing DMD allows the well-defined device to be implanted with a high-compacted shape and transformed into their designed shape to meet the requirement. Herein, a 4D printing tissue engineering material is developed with excellent biocompatibility and shape memory effect based on the photocrosslinked polycaprolactone (PCL). The fast thiol-acrylate click reaction is applied for photocrosslinking of the acrylates capped star polymer (s-PCL-MA) with poly-thiols, that enable the 3D printing for the DMD fabrication. The cell viability, erythrocyte hemolysis, and platelet adhesion results indicate the excellent biocompatibility of the 4D printing polymer, especially the biological subcutaneous implantation results confirm the promote tissue growth and good histocompatibility. A 4D printing stent with deformable shape and recovery at a temperature close to human body temperature demonstrated the potential application as DMD. In addition, the everolimus is loaded to the polymer (ps1-PCL) through host-guest coordination with ß-cyclodextrin as the core of the star polymer, which shows sustained drug release and improved body's inflammatory response.

4D Printing of Shape Memory Vascular Stent Based on ßCD-g-Polycaprolactone.

The 4D-printing technology is applied to fabricate a shape memory peripheral stent with good biocompatibility, which sustains long-term drug release. The star polymer s-PCL is prepared by ring opening polymerization of ε-caprolactone with the -OH of ß-cyclodextrin (ßCD) as initiator, and then the s-PCL is modified with acrylate endgroup which allows the polymerization under UV light to form the crosslinking network c-PCL. Attributed to the feature of the high crosslinked structure and chemical nature of polycaprolactone (PCL) and ßCD, the composite exhibits appropriate tensile strength and sufficient elasticity and bursting pressure, and it is comparable with great saphenous vein in human body. The radial support of the 4D-printed stent is 0.56 ± 0.11 N and is equivalent to that of commercial stent. The cell adhesion and proliferation results show a good biocompatibility of the stent with human umbilical vein endothelial cells. Due to the presence of ßCD, the wettability and biocompatibility of the materials are improved, and the sustained paclitaxel release based on the host-guest complexion shows the potential of the drug-loaded stent for long-term release. This study provides a new strategy to solve the urgent need of small-diameter scaffolds to treat critical limb ischemia.