Biocompatibility of common polyimides with human endothelial cells for a cardiovascular microsensor

The cardiovasculature is an emerging niche for polyimide microdevices, yet the biocompatibility of polyimides with human endothelial cells has not been reported in the literature. In this study, we have evaluated an experimental polyimide-based pressure sensor for biological safety to determine its suitability for intravascular operation by using an in vitro model of human endothelium, following ISO 10993-5 protocols for extract tests and direct contact tests. First, SV-HCEC cells were incubated with extracts derived from common microfabrication polyimides utilized in the transducer (PMDA-ODA, BPDA-PPD, and a proprietary thermoplastic adhesive), and then labeled with selective probes to evaluate the effect of the polyimides on mitochondria and cell viability. Flow cytometry analysis showed that incubation of SV-HCECs with polyimide extracts resulted in no significant change in mitochondrial membrane potential (detected by JC-1) or apoptotic (annexin V) and necrotic (propidium iodide) cell death, when compared to incubation with extracts of high-density polyethylene (HDPE) and untreated cells used as negative controls. Second, primary human endothelial cells were incubated in direct contact with the completed sensor and then labeled with selective probes for live-dead analysis (calcein-AM, ethidium homodimer-1). Endothelial cells showed no loss of viability when compared to negative controls. Combined, the studies show no significant change in early markers of stress or more strict markers of viability in endothelial cells treated with the polyimides tested. We conclude that these common microfabrication polyimides and the derived sensor are not cytotoxic to human endothelial cells, the primary cell type that cardiovascular sensors will contact in vivo.