Biomimetic SERS-Active Transwell Insert for Non-Invasive Monitoring of Extracellular pH

The development of physiologically relevant cell culture materials is increasingly important in screening therapies in a biologically meaningful manner. Air-liquid interface (ALI) cultures are widely used to study organs such as the lung where both the basement membrane (BM) and epithelial barrier are important. The ability to monitor these cultures in a label-free way, using standard cell culture formats, is important in ensuring widespread adoption. Standard ALI culture systems rely on membranes that lack the structural complexity of the native BM and offer no inherent capacity for sensing cellular responses to therapy. Here, we present a biomimetic SERS-active electrospun Transwell insert (SERS-pH-Mesh) that delivers a step change in an ALI culture platform by enabling non-invasive monitoring of chemotherapy-induced pHe shifts in lung cancer epithelial cells. To construct this system, thermoplastic polyurethane (TPU) nanofibers were electrospun, gold-coated, integrated into a Transwell setup, and functionalized with the pH-sensitive probe 4-mercaptobenzoic acid (4-MBA). A549 lung cancer epithelial cells were then cultured on the SERS-pH-Mesh under ALI conditions and treated with cisplatin. SERS measurements in live cultures revealed dose-dependent pH shifts, indicating increased extracellular alkalinity at higher cisplatin concentrations. By enabling quantitative and label-free assessment of treatment-induced metabolic alterations, the biomimetic SERS-pH-Mesh platform could accelerate preclinical drug screening and disease modeling by providing rapid and non-destructive readouts of cellular responses.