(Nanowerk Spotlight) Cardiovascular diseases remain a leading cause of death worldwide, with atherosclerosis being a primary contributor. The narrowing of blood vessels due to plaque buildup can lead to life-threatening conditions, prompting the development of various interventional treatments. Stents, small mesh tubes inserted into arteries to keep them open, have been a cornerstone of cardiovascular medicine for decades. However, traditional stents have faced persistent challenges, including the risk of restenosis – the re-narrowing of arteries after stent placement.
The evolution of stent technology has seen several iterations, from bare metal stents to drug-eluting stents, each aiming to address the limitations of its predecessors. Yet, the ideal stent that combines optimal mechanical properties, biocompatibility, and real-time monitoring capabilities has remained elusive. The rigidity of metal stents can make placement in curved vessels difficult, while polymer-based biodegradable stents often lack sufficient radial strength to support vessel walls effectively.
Recent advancements in materials science, 3D printing technology, and miniaturized sensors have opened new avenues for stent design. The integration of wireless sensors into stents has been explored as a means to detect early signs of restenosis and monitor blood pressure changes. However, these smart stents have faced their own set of challenges. Metal stents interfere with the transmission of wireless signals, while polymer stents lack the necessary structural integrity for long-term use.
The convergence of these technological developments has set the stage for a new generation of stents that could potentially overcome the limitations of current designs. Researchers have been working on hybrid structures that combine the strengths of different materials, as well as incorporating advanced sensing technologies that can function without compromising the stent’s primary mechanical role.
A team of researchers in Korea has now introduced an innovative hybrid smart stent system that represents a significant step forward in addressing these long-standing challenges. Their work, published in Advanced Functional Materials (“The PolyCraft Polymer–Metal Hybrid Smart Stent System: The Future of Cardiovascular Blood Pressure Management”), details the development of the PolyCraft polymer-metal hybrid smart stent system, which combines the structural advantages of metal stents with the signal-friendly properties of polymers, all while integrating a wireless pressure sensor for real-time monitoring.
The PolyCraft system consists of a hybrid stent made from alternating segments of cobalt-chromium alloy and polycaprolactone (PCL), connected by a unique dual inverted Y-type connector. This design allows for excellent radial strength, comparable to traditional metal stents, while maintaining flexibility similar to polymer stents. The hybrid structure also enables the integration of an inductor-capacitor (LC) wireless pressure sensor without signal degradation, a problem that has plagued previous attempts at creating smart metal stents.
Overview of the PolyCraft polymer–metal hybrid smart stent system. a) Working principle of the PolyCraft polymer–metal hybrid smart stent system. b) Schematic of the PolyCraft polymer–metal hybrid smart stent system and polymer–metal hybrid stent design. c) Schematic of the LC wireless pressure sensor. d) Layer-wise breakup of the sensor. e) Cross-section of the connection structure of wireless pressure sensor. (Image: Reprinted with permission by Wiley-VCH Verlag)
The researchers employed a combination of advanced manufacturing techniques to create their hybrid stent. The metal segments were precision-cut using lasers, while the polymer components were fabricated using custom 3D printing methods. A critical innovation in the design is the use of polylactic acid (PLA) as a connecting material between the metal and PCL segments. PLA’s transparency allows for laser transmission welding, which significantly strengthens the bond between the metal and polymer components, ensuring structural integrity while maintaining flexibility.
The integrated LC wireless pressure sensor, fabricated using microelectromechanical systems (MEMS) technology, is capable of detecting subtle changes in blood pressure. This could potentially allow for early detection of restenosis or other cardiovascular issues before they become critical. The sensor’s design includes a pressure-sensitive capacitor and a signal-coupling inductor, encased in biocompatible materials.
Extensive testing of the PolyCraft system demonstrated its promising mechanical and sensing capabilities. The hybrid stent showed excellent radial strength (0.125 N/mm) and flexibility (2 N mm2), striking a balance between the rigid support of metal stents and the adaptability of polymer stents. Notably, the radial strength was only slightly lower than that of bare metal stents (0.137 N/mm), while its flexibility was significantly better than both PLA (5.01 N mm2) and metal stents (8.43 N mm2). This combination of properties could make the PolyCraft system particularly suitable for use in curved or complex vascular geometries.
The researchers conducted both in vitro and in vivo studies to validate the system’s performance. In a phantom system designed to mimic human blood vessels, the PolyCraft stent successfully detected pressure changes with high accuracy. The team then modified the system into an artificial blood vessel and implanted it into the femoral artery of a pig, demonstrating its ability to monitor blood pressure in a living organism.
One of the most significant advantages of the PolyCraft system is its potential for continuous, real-time monitoring of vascular health. By integrating wireless sensing capabilities directly into the stent, doctors could potentially track a patient’s cardiovascular condition without the need for invasive procedures. This could lead to earlier interventions and more personalized treatment strategies.
The development of the PolyCraft system also opens up new possibilities for the integration of smart medical devices with artificial intelligence. The continuous stream of data from implanted sensors could be analyzed using advanced machine learning algorithms to detect patterns or anomalies that might not be apparent through traditional monitoring methods. This integration of AI with real-time physiological data could potentially revolutionize the management of cardiovascular diseases, allowing for more proactive and precise interventions based on individualized, data-driven insights.
While the results of this study are promising, it’s important to note that further research and clinical trials will be necessary before such a system could be used in human patients. Long-term studies will be needed to assess the durability of the hybrid stent and the longevity of the integrated sensor. Additionally, the biocompatibility and potential long-term effects of the materials used will require thorough investigation.
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