Clot formation inside a membrane oxygenator (MO) due to blood-to-foreign surface interaction represents a frequent complication during extracorporeal membrane oxygenation. Since current standard monitoring methods of coagulation status inside the MO fail to detect clot formation at an early stage, reliable sensors for early clot detection are in demand to reduce associated complications and adverse events. Bioimpedance analysis offers a monitoring concept by integrating sensor fibers into the MO. Herein, the feasibility of clot detection via bioimpedance analysis is evaluated. A custom-made test chamber with integrated titanium fibers acting as sensors was perfused with heparinized human whole blood in an in vitro test circuit until clot formation occurred. The clot detection capability of bioimpedance analysis was directly compared to the pressure difference across the test chamber (ΔP-TC), analogous to the measurement across MOs (ΔP-MO), the clinical gold standard for clot detection. We found that bioimpedance measurement increased significantly 8 min prior to a significant increase in ΔP-TC, indicating fulminant clot formation. Experiments without clot formation resulted in a lack of increase in bioimpedance or ΔP-TC. This study shows that clot detection via bioimpedance analysis under flow conditions in a blood-perfused test chamber is generally feasible, thus paving the way for further investigation.

Blood clot formation inside the membrane oxygenator (MO) remains a risk in extracorporeal membrane oxygenation (ECMO). It is associated with thromboembolic complications and normally detectable only at an advanced stage. Established clinical monitoring techniques lack predictive capabilities, emphasizing the need for refinement in MO monitoring towards an early warning system. In this study, an MO was modified by integrating four sensor fibers in the middle of the hollow fiber mat bundle, allowing for bioimpedance measurement within the MO. The modified MO was perfused with human blood in an in vitro test circuit until fulminant clot formation. The optical analysis of clot residues on the extracted hollow fibers showed a clot deposition area of 51.88% ± 14.25%. This was detectable via an increased bioimpedance signal with a significant increase 5 min in advance to fulminant clot formation inside the MO, which was monitored by the clinical gold standard (pressure difference across the MO (dp-MO)). This study demonstrates the feasibility of detecting clot growth early and effectively by measuring bioimpedance within an MO using integrated sensor fibers. Thus, bioimpedance may even outperform the clinical gold standard of dp-MO as a monitoring method by providing earlier clot detection.

Mechanophores that translate mechanical force into optical signals are powerful tools for probing damage in polymeric materials, yet regularly suffer from undesired thermal reactivity compromising mechanochemical selectivity and processability of the host polymer. Here, we show that the [4+2] photodimerization of highly emissive 9-π-extended anthracene yields an optical force probe (OFP) which features excellent thermal stability above 200 °C as well as photochemical robustness. We demonstrate mechanochemical activation in thermoplastic polymers using blends of commercial poly(methyl methacrylate) (PMMA), polystyrene (PS), thermoplastic polyurethane (TPU), and polyethylene (PE) at low functional material loadings (≤ 5 wt%). Importantly, we subject OFP-functionalized TPU to melt processing including extrusion and melt spinning, and obtain mechanofluorogenic fibers that retain intact OFPs. Together, our results underscore photodimerization of fluorophores as strategy to tailor the optical readout of OFPs and open an avenue to investigate molecular-level damage in melt-processed thermoplastics.