Opportunities and challenges with 4D smart materials for tissue engineering

S. Lohfeld
University of Missouri-Kansas City,
United States

Keywords: shape memory polymers, biocompatibility, implants


Smart materials, capable of altering their properties in response to environmental stimuli or remote activation, show great promise for various medical applications, including implants. By leveraging these materials, medical procedures can potentially become more minimally invasive, as they enable shape and size adjustments in vivo at the site of application, thereby minimizing the required incision size. Moreover, during treatment, smart implants can undergo shape corrections remotely to adapt to the evolving progress of therapy, thus obviating the need for further surgical interventions. These materials can respond to changes in parameters such as humidity, temperature, or light. In the realm of tissue engineering and regenerative medicine, the integration of biodegradable materials with shape-changing capabilities holds particular interest, as it allows implants to be absorbed by the body once they have fulfilled their function, mitigating the risk of late infection. The shape memory functionality of polymers can be remotely controlled through the incorporation of responsive substances such as graphene or iron tetraoxide nanoparticles. The resulting light-responsive shape memory polymer composite can be manipulated via irradiation with near-infrared (NIR) light. Upon exposure to NIR light, a polymer previously deformed from its memorized shape will revert to its original form. This phenomenon occurs as the nanoparticles absorb the NIR light and partially convert it into thermal energy, leading to localized heating of the polymer and subsequent softening, facilitating the return to the memorized shape. Despite the potential benefits for medical applications, such composite materials pose certain risks. Regarding biocompatibility, there exists the possibility of tissue reactions, especially in the case of biodegradable materials. The release of the nanoparticles during the material degradation and their subsequent distribution within the body may induce adverse effects. Another concern is the generation of excess heat within the material during the shape recovery process. Depending on the nanoparticle concentration and the energy of the delivered light, the composite may experience excessive heating, potentially causing damage to surrounding tissues. Finally, it is essential for the material surface to promote cell adhesion, proliferation and differentiation to facilitate tissue growth while ensuring proper absorption of the implant. Therefore, the development of shape memory polymer composites for tissue engineering applications necessitates early-stage assessments during the definition of the material composition to ensure they meet the fundamental requirements for tissue engineering materials.