Surface-Modified Electrospun Polyurethane Tubular Scaffold for Engineering Renal Proximal Tubule Constructs

The renal proximal tubule (PT) is central to kidney physiology and is particularly susceptible to injury; however, in vitro systems that accurately replicate its microenvironment and functional characteristics remain limited. To address this need, we report the fabrication and surface modification of electrospun polyurethane (PU) tubular scaffolds designed to enhance epithelial compatibility and support functional behavior of renal PT epithelial cells (RPTECs). While PU provides robust mechanical strength and flexibility for tubular constructs, its inherent hydrophobicity limits cell attachment; therefore, scaffolds were surface modified via tetraethoxy silane (TEOS) plasma deposition (PU-P) and Type I collagen coating (PU-C). Surface characterization demonstrated increased roughness and significantly improved hydrophilicity, as evidenced by reduced water contact angles in PU-P (97.26° ± 1.92°) and PU-C (64.1° ± 2.96°). These modifications promoted enhanced protein adsorption, with BSA and laminin binding increasing by 1.7-fold and 1.8-fold, respectively, compared with unmodified tubules. Cytocompatibility assessment confirmed high cell viability across all scaffold types (> 90%). RPTECs cultured on surface-modified electrospun PU tubules exhibited efficient adhesion, well-spread morphology, and organized cytoskeletal architecture, indicating improved cellular compatibility. In contrast, cell attachment on unmodified tubules was minimal. Immunofluorescence analysis demonstrated robust expression of renal PT markers, including Aquaporin 1 and Collagen IV, on modified scaffolds, while expression was weak or absent on unmodified constructs, indicating maintenance of the PT phenotype. Functional assessment revealed a threefold increase in alkaline phosphatase activity on coated tubules over 14 days compared with 2D culture, reflecting enhanced brush border activity and improved epithelial functional behavior. Overall, surface modification of electrospun PU tubular scaffolds significantly improves RPTEC adhesion, phenotype preservation, and functional activity, supporting the development of physiologically relevant renal PT models for in vitro applications.