Personalized, Mechanically Strong, and Biodegradable Coronary Artery Stents via Melt Electrowriting

Abstract

Biodegradable coronary artery stents are soughtafter alternatives to permanent stents. These devices are designed to degrade after the blood vessel heals, leaving behind a regenerated artery. The original generation of clinically available biodegradable stents required significantly thicker struts (∼150 μm) than nondegradable ones to ensure sufficient mechanical strength. However, these thicker struts proved to be a key contributor to the clinical failure of the stents. A current challenge lies in the fabrication of stents that possess both thin struts and adequate mechanical strength. In this contribution, we describe a method for the bottom-up, additive manufacturing of biodegradable composite stents with ultrathin fibers and superior mechanical properties compared to the base polymer. Specifically, we illustrate that melt electrowriting (MEW) can be used to 3D print composite structures with thin struts (60−80 μm) and a high degree of geometric complexity required for stenting applications. Additionally, this technology allows additive manufacture of personalized stents that are customized to a patient's unique anatomy and disease state. Furthermore, we illustrate that polycaprolactone-reduced graphene oxide nanocomposites have superior mechanical properties compared to original polycaprolactone without detriment to the material's cytocompatibility and that customizable stent-like structures can be fabricated from these materials with struts as thin as 60 μm, well below the target value for clinical use of 80 μm.

Degradation of Melt Electrowritten PCL Scaffolds Following Melt Processing and Plasma Surface Treatment

“…This means that during routine MEW, polymers are retained at elevated temperatures within a syringe loaded within a heated print head, often for days at a time, to ensure sufficient material is available to print sufficient scaffold replicates for in vitro and in vivo studies. [ 6–8 ] This compares to other extrusion‐based 3D printing techniques such as a fused deposition modelling (FDM) where materials are fed into the heated print head in the form of filament, and localized heating is applied immediately prior to extrusion, followed by rapid cooling. Thermally‐induced oxidative degradation of polymers during MEW where the entire polymer reservoir is held at elevated temperatures is therefore a concern [ 9 ] which could impact the stability and mechanical properties of MEW scaffolds.…”

Amphiphilic Core Cross-Linked Star Polymers for the Delivery of Hydrophilic Drugs from Hydrophobic Matrices

“…Solutions were continuously stirred with a magnetic stirrer for 24 h to allow dispersion of GO. GO was thermally reduced at 150 °C to obtain reduced graphene oxide (rGO) according to our previously published protocol …”

“…The thicker struts resulted in more prothrombogenic material within the vessel and caused detrimental changes to the blood flow profile that further promoted thrombosis. , Previously, we illustrated that polymer nanocomposites could be used to increase the mechanical strength of the polymer, facilitating the design of stents with thinner struts. We additionally showed that the novel fabrication technique of melt electrowriting (MEW) could be used to fabricate stents with thin struts (∼60 μm) and arbitrary shapes, potentiating its use in personalized stent design . To further address the problem of long-term stent thrombosis, we propose the development of a material that enables the prolonged delivery of the antithrombotic drug heparin throughout the degradation of the stent to aid in the prevention of thrombosis and facilitate the development of safe and effective devices.…”

The Importance of Interfaces in Multi‐Material Biofabricated Tissue Structures

“…[139] This technique allows to obtain stable structures with a porosity higher than 80% that encompass fibers with diameters between ≈300 nm and 50 μm, [140] which approximate to the sizes of the fibrous structure of native ECM structure, and can subsequently significantly contribute to the mechanical properties of composite matrices. [139,141,142] Important to mention that a first step in convergence of fiber formation fabrication technologies with biofabrication was reported by Kim et al which integrating solution electrospinning of SF with melt electrospinning of PCL, [143] while Yeo et al proposed an alternative hybrid approach that combined melt spinning of PCL with electrospinning of cell-laden alginate-based bioink (Figure 7B). [144] Nevertheless, extrusion-based bioprinting (using GelMA as bioink) has been successfully converged with MEW of thermoplastic polymers (e.g., PCL) to create biologically functional constructs with more complex architecture and low thermoplastic content than the ones obtained by conventional extrusion printing.…”