Influence of kapok fibers on the formation of tumor and fibroblast cell aggregates.

Bioscaffolds have been incorporated into three-dimensional (3D) cell culture systems to develop advanced cellular models that mimic in vivo physiological environments and facilitate oxygen and nutrient transport within cell aggregates, thereby reducing hypoxia and necrotic core formation. In this study, raw and NaOH-treated kapok fibers were employed to evaluate their potential as bioscaffolds in 3D cell culture systems with different cell types, including human breast cancer (MCF-7), human osteosarcoma (SaOS-2), and mouse embryonic fibroblast (NIH/3 T3). Both raw and treated fibers supported cell attachment without inducing cytotoxicity. All cells successfully formed aggregates without and with kapok fibers. Kapok fibers influenced the structural organization of aggregates in a cell type-specific manner, mainly reducing aggregate density and promoting the appearance of internal cavities linked to the hollow fiber lumen. In addition, the incorporation of kapok fiber enhanced aerobic metabolism in MCF-7, SaOS-2, and NIH/3 T3 aggregates. The presence of kapok fibers also promoted cell viability in MCF-7 aggregates, with treated fibers exhibiting the highest growth profile. For NIH/3 T3 aggregates, fiber incorporation significantly attenuated cell death, with treated kapok fibers showing the greatest protective effect and highest cell viability. Furthermore, the presence of treated kapok fiber in SaOS-2 aggregates reduced reactive oxygen species (ROS) levels without affecting cell viability. These findings demonstrate that kapok fibers are promising biocompatible scaffolds for modulating aggregate morphology and cellular function in 3D in vitro culture models.