Surface bio-engineering of melt electrowritten tubular scaffolds via plasma immersion ion implantation (PIII)

Melt electrowriting (MEW) enables the fabrication of highly controlled, open-pore tubular constructs for replicating the complex architectures of vascular, renal, and other tissues. However, a key challenge is to functionalize their surfaces so that they not only support but also instruct key biological interactions, particularly in promoting vascularization. Here, we propose plasma immersion ion implantation (PIII) as a biofunctionalization strategy for open-pore tubular constructs fabricated by MEW. Surface chemistry analysis confirmed homogeneous treatment across PIII-treated MEW 3D structures, while uniaxial tensile tests demonstrated no significant changes in mechanical properties following the treatment. Electron paramagnetic resonance (EPR) data provided evidence of the formation of a stable, radical-rich surface, which was further validated by fluorescence imaging with a model molecule, confirming the radicals' role in enabling uniform covalent biomolecule attachment. The PIII-treated MEW constructs were covalently functionalized with vascular endothelial growth factor (VEGF), thereby modulating the behavior of seeded cells. Endothelialization studies using conditionally immortalized glomerular endothelial cells (ciGEnC) demonstrated that VEGF-immobilized MEW tubes effectively support monolayer formation, achieving outcomes comparable to those observed with VEGF supplementation in culture media. Remarkably, the immobilized VEGF sustained endothelialization with a similar effectiveness to traditional VEGF suspension methods over prolonged culture conditions (21 days), but without the need for continuous VEGF supplementation. These findings establish a novel biofunctionalization strategy for vascularized tissue engineering scaffolds and pave the way for plasma-modified MEW tubes as platforms for preclinical models and regenerative medicine applications.