4D Printing Shape Memory Vascular Stent Based on Polycaprolactone

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Polycaprolactone is an organic high molecular polymer with the chemical formula (C₆H₁₀O₂)_n. It has the property of being well soluble in aromatic compounds, ketones and polar solvents. Polycaprolactone has good biocompatibility, good compatibility with organic polymers, and good biodegradability, and can be used as a cell growth support material. It is compatible with a variety of conventional plastics and can be completely degraded in 6-12 months in the natural environment. In addition, polycaprolactone also has good shape memory temperature control properties and is widely used in the production and processing of drug carriers, plasticizers, degradable plastics, nanofiber spinning, and plastic materials.

The emerging 4D printing technology is a combination of additive manufacturing (3D printing) and deformable materials, in which static 3D printed objects change their shape over time. It not only enables precise 3D printing and complex structural design. Moreover, controllable attribute evolution over time can be achieved. The 4D printing process includes the 3D printing process, stimulation, smart response materials, interaction mechanisms and mathematical modeling. 4D printing uses time as the fourth dimension. Objects printed using smart materials create or modify shapes when stimulated. . Parameters that change over time include temperature, water, light, humidity, pH, etc. 4D printing responds to external stimuli, giving new dimensions of transformation on demand. These materials can be programmed to react with parameters of their surrounding environment, thereby changing their form. Therefore, 4D printing has attracted the attention of more and more researchers.

Shape memory polymers (SMPs) are stimulus-responsive materials based on the conformational transformation of polymer chains. It can fix the temporary shape under external stimulation (heat, light, electricity, magnet, PH, etc.) and can return to the original shape after changing the stimulation conditions. Based on adjustable properties and variable structures, SMPs can recover from programmed temporary shapes to their initial shapes. Active deformation capabilities increase the application of SMPs in biomedical fields, such as mitigating surgical approach injuries in surgical and vascular procedures. The combination of 4D printing and shape memory polymers can quickly print stents of various structures, and can deform under the influence of suitable human body temperature to achieve clinical effects of reducing surgical approach damage and treating target vascular lesions. Shape memory polymers have broad application prospects and huge biomedical potential.

Researchers have prepared a shape-memory polycaprolactone polymer that can load and sustain drugs, and used the polymer combined with 4D printing technology to prepare a small-diameter stent aimed at solving vascular stenosis in the lower limbs. This study first prepared a star-shaped polymer by ring-opening polymerization of 𝜷-cyclodextrin and 𝝐-caprolactone, and then modified the polymer with acrylation. Due to the highly cross-linked structure and chemical properties of polycaprolactone and 𝜷-cyclodextrin, the composite material has appropriate tensile strength and sufficient elasticity and bursting pressure, which is comparable to the human great saphenous vein. A shape memory peripheral stent with good biocompatibility was manufactured using 4D printing technology, with a radial support of 0.56±0.11N, which is equivalent to commercial metal stents. Cell adhesion and proliferation results indicated that the scaffold had good biocompatibility with human umbilical vein endothelial cells. And due to the presence of 𝜷-cyclodextrin, the wettability and biocompatibility of the material have been significantly improved. This vascular stent utilizes the hollow hydrophobic structure inside the 𝜷-cyclodextrin in the polymer structure network and the host-guest relationship with the drug, and uses paclitaxel as the drug to load the drug to achieve long-term release of the drug. The stent loaded with paclitaxel drug can better inhibit the growth of endothelial cells. This study provides a new strategy to address the urgent need for small-diameter stents to treat critical limb ischemia.

4D Printing Shape Memory Vascular Stent Based on Polycaprolactone