Improved resolution of 3D printed scaffolds by shrinking

3D-Printed Radiopaque Bioresorbable Stents to Improve Device Visualization

Bioresorbable stents (BRS) hold great promise for the treatment of many life-threatening luminal diseases. Tracking and monitoring of stents in vivo is critical for avoiding their malposition and inadequate expansion, which often leads to complications and stent failure. However, obtaining high X-ray visibility of polymeric BRS has been challenging because of their intrinsic radiolucency. This study demonstrates the use of photopolymerization-based 3D printing technique to fabricate radiopaque BRS by incorporating iodixanol, a clinical contrast agent, into a bioresorbable citrate-based polymer ink. The successful volumetric dispersion of the iodixanol through the 3D-printing process confers strong X-ray visibility of the produced BRS. Following in vitro degradation, the 3D-printed BRS embedded in chicken muscle maintains high X-ray visibility for at least 4 weeks. Importantly, the 3D-printed radiopaque BRS demonstrates good cytocompatibility and strong mechanical competence in crimping and expansion, which is essential for minimally invasive stent deployment. In addition, it is found that higher loading concentrations of iodixanol, e.g. 10 wt.%, results in more strut fractures in stent crimping and expansion. To conclude, this study introduces a facile strategy to fabricate radiopaque BRS through the incorporation of iodixanol in the 3D printing process, which could potentially increase the clinical success of BRS.

Bio-Based Polymers for 3D Printing of Bioscaffolds

Three-dimensional (3D) printing technologies enable not only faster bioconstructs development but also on-demand and customized manufacturing, offering patients a personalized biomedical solution. This emerging technique has a great potential for fabricating bioscaffolds with complex architectures and geometries and specifically tailored for use in regenerative medicine. The next major innovation in this area will be the development of biocompatible and histiogenic 3D printing materials with bio-based printable polymers. This review will briefly discuss 3D printing techniques and their current limitations, with a focus on novel bio-based polymers as 3D printing feedstock for clinical medicine and tissue regeneration.

Development and performance of a 3D-printable poly(ethylene glycol) diacrylate hydrogel suitable for enzyme entrapment and long-term biocatalytic applications

Physical entrapment of enzymes within a porous matrix is a fast and gentle process to immobilize biocatalysts to enable their recycling and long-term use. This study introduces the development of a biocompatible 3D-printing material suitable for enzyme entrapment, while having good rheological and UV-hardening properties. Three different viscosity-enhancing additives have been tested in combination with a poly(ethylene glycol) diacrylate-based hydrogel system. The addition of polyxanthan or hectorite clay particles results in hydrogels that degrade over hours or days, releasing entrapped compounds. In contrast, the addition of nanometer-sized silicate particles ensures processability while preventing disintegration of the hydrogel. Lattice structures with a total height of 6 mm consisting of 40 layers were 3D-printed with all materials and characterized by image analysis. Rheological measurements identified a shear stress window of 200 < τ < 500 Pa at shear rates of 25 s^-1 and 25°C for well-defined geometries with an extrusion-based printhead. Enzymes immobilized in these long-term stable hydrogel structures retained an effective activity of approximately 10% compared to the free enzyme in solution. It could be shown that the reduction of effective activity is not caused by a significant reduction of the intrinsic enzyme activity but by mass transfer limitations within the printed hydrogel structures.