Development of a biomimetic hybrid nanofiber membrane towards lung-on-a-chip devices

Abstract

The alveolar basement membrane (BM) is essential for maintaining the integrity and function of the lung air-blood barrier. Replicating its structural, mechanical and biological properties remains a key challenge in the development of lung-on-a-chip (LoC) devices, as commonly used membranes often fail to fully replicate native BM characteristics. This study aimed to develop and characterise biomimetic electrospun nanofiber membranes as candidates for LoC integration. Three membrane types were fabricated: poly(ε-caprolactone) (PCL), PCL-collagen and a novel type, PCL-gelatin composite. The membranes were characterised for morphology, chemical composition, mechanical properties, wettability, and biocompatibility using scanning electron microscopy (SEM), ATR-FTIR spectroscopy, tensile testing, contact angle measurements, confocal fluorescence microscopy, and MRC-5 cell culture assays. SEM analysis revealed randomly oriented fibrous morphology with a consistent thickness of approximately 10 μm across all membranes. The PCL-gelatin membrane exhibited the smallest fiber diameter (0.803 ± 0.134 μm), closely replicating the nanoscale fibrillar architecture of the native alveolar BM. ATR-FTIR confirmed successful protein incorporation, with crosslinking evidenced by enhanced amide band intensity. Mechanically, PCL-gelatin presented the most balanced profile, combining the highest tensile strength with intermediate stiffness, offering a closer approximation to native tissue compliance. Both composite membranes exhibited complete surface wettability in contrast to the hydrophobic PCL control, confirming that protein incorporation fundamentally transforms surface character. Biocompatibility assessment via Live/Dead confocal fluorescence imaging confirmed high cell viability across all membranes, while PrestoBlue metabolic assay demonstrated enhanced and sustained MRC-5 cell proliferation on PCL-gelatin over 96 hours. A prototype microfluidic device was built, and a membrane was integrated between PDMS and COC layers, with on chip cell culture identified as a key direction for future optimisation. Overall, the PCL-gelatin hybrid nanofiber membrane demonstrates strong potential as a biomimetic platform for physiologically relevant LoC platforms.