## 4 Applications
### Biomedical Applications
The biocompatibility of these composites was confirmed by both in vitro and in vivo studies, with PEGylated AuNR improving hemocompatibility through increased hydrophilicity. Additionally, blood compatibility, cytocompatibility, and histocompatibility of the PLCL-AuNR/PEG composites were investigated and reported to be in acceptable levels [80]. Biodegradable SMPC-based stents represent a promising option for the treatment of cardiovascular and tracheal diseases. Drug-eluting nonvascular stents designed for local tumor treatment in tubular organs such as airways or the esophagus require both mechanical and therapeutic performance considerations. [PERSON] et al. developed a biodegradable digital light processing (DLP) 3D-printed SMPNC by incorporating AuNRs into a polyester copolymer, designed for stent fabrication [100]. This research included a clinically relevant demonstration where a human-sized meshed stent (H 12 mm, \(\mathcal{O}\) 16 mm, thickness 1.6 mm) was implanted in a porcine intestinal segment, showing rapid expansion under 808 nm NIR light exposure within 40 s, highlighting its potential for on-demand deployment and NIR light-triggered expansion in biodegradable stent applications (Figure 27d). In parallel, [PERSON] and colleagues utilized a shape-memory polycaprolactone-polydopamine (PCL-PDA) nanocomposite to create a biomedical tubular sample, which demonstrated efficient NIR light-triggered shape-memory behavior, reverting to its original configuration within 60 s during in vitro tests [260]. Further in vivo evaluations confirmed the non-cytotoxicity and excellent biocompatibility of the PCL-PDA polyurethane, as it did not inhibit cell proliferation or induce significant inflammatory responses. Utilizing direct writing printing technology, [PERSON] et al. developed stents from Fe\({}_{3}\)O\({}_{4}\) NPs incorporated UV cross-linked shape-memory PLA ink [281]. The resulting stents demonstrated remote non-contact actuation, as exemplified by a spiral structure expanding from a 1 mm to a 2.7 mm inner diameter within 10 s when exposed to an alternating magnetic field (Figure 27e). In another study, [PERSON] et al. developed a bio-designed tracheal scaffold using 4D printing technology, utilizing a shape-memory PLA/Fe\({}_{3}\)O\({}_{4}\) composite. These bioinspired scaffolds, activated by an alternating magnetic field, facilitate implantation in a temporarily deformed state and subsequent deployment into their predefined shapes, offering enhanced support and fixation within the trachea [282]. Polymer-based scaffolds for bone regeneration require materials that are non-toxic, biocompatible, and, in certain applications, biodegradable, characterized by high strength and a porous structure to facilitate tissue integration [283; 284]. The incorporation of active components to stimulate osteogenesis is essential, with polymers exhibiting a SME emerging as promising candidates for developing self-fitting scaffolds in tissue engineering. However, traditional bone tissue scaffolds encounter challenges, including brittleness, inadequate osteoinductive properties, and difficulties in implantation via minimally invasive procedures, underscoring the imperative for innovative approaches [25]. [PERSON] et al. engineered porous bone tissue scaffolds using shape-memory PLA/Fe\({}_{3}\)O\({}_{4}\) composite, inspired by the microstructure of lotus roots and cellular co-continuous-like structures through 3D printing technology (Figure 27f) [285]. Exhibiting a porosity of 60%, these scaffolds demonstrated a strength of approximately 27 MPa, exceeding that of clinical artificial bone and thus offering significant support for bone defects. Designed for minimally invasive implantation in a compact form, these scaffolds are capable of expanding to their operational state under remote non-contact actuation, such as by a magnetic field, facilitating their application in bone regeneration. In another study. [PERSON] et al.