Fiber-Reinforced Silk Composite for Enhanced Urokinase Production Using High-Density Perfusion Culture and Bioactive Molecule Supplementation

Urokinase plasminogen activator (uPA) has been extensively used as a thrombolytic drug in cases of myocardial infarction, thromboembolism, and ischemic brain stroke. Media optimization and high-density perfusion culture are the decisive factors that facilitate enhanced urokinase production in a conditioned medium. In this study, we have aimed for a high-density perfusion culture of HT1080, a human fibrosarcoma cell line, by formulating optimal media for enhanced urokinase productivity. Four scaffold variants were fabricated from silk fibroin and microfibers of Bombyx mori (BM) and Antheraea assamensis (AA) and physico-chemically characterized. Field emission scanning electron microscopy studies revealed a heterogeneous distribution of pores with interconnected networks supporting cell infiltration, attachment, and long-term viability. AA-based fiber-reinforced scaffolds (ASAF) demonstrated superior mechanical strength, integral stability, and increased cell proliferation as compared to pure silk scaffolds. Media formulation was accomplished by limiting serum concentration (2% FBS) and supplementing with 20 μg/mL arginine and 20 ng/mL TGF-β1 to retain the stationary phase of cells and augment the urokinase production. A perfusion bioreactor culture of HT1080-laden scaffolds in the presence of formulated media was performed for improving the production of urokinase, with a maximum activity of 432 U/L. Also, gene expression analysis revealed that the individual silk scaffolds have different effects on regulating the expression of plasminogen activator urokinase and plasminogen activator urokinase receptor. In brief, our results suggest that a perfusion bioreactor culture of HT1080-laden ASAF scaffolds in formulated media promotes an increased urokinase production, such that it can be further used as a novel 3D matrix platform for industrial production of the lifesaving uPA drug.