Zolfaghari, P. | bioRxiv Science

bioRxiv2025

Minimally invasive and in situ capacitive sensing of cardiac biomarker from interstitial fluid

Current diagnostic approaches for myocardial infarction (MI) rely on blood-based cardiac biomarker analysis by centralized instruments, often delaying timely clinical decisions. We present a microneedle-based capacitive biosensor (MiCaP) for in situ, minimally invasive monitoring of cardiac troponin I (cTnI) in interstitial fluid (ISF) for point-of-care (POC) applications. MiCaP is a label-free biosensor operating based on non-faradaic sensing by monitoring electric double layer capacitance at the microneedle-ISF interface. We extracted a simplified equivalent circuit model for MiCaP inserted into skin, confirming that the measured capacitance variations originate from cTnI binding to surface-immobilized antibodies. MiCaP was fabricated using a scalable process and functionalized with anti-cTnI antibodies. In vitro measurements showed a dynamic detection range of 10 pg/mL to 10 ng/mL, a limit of detection (LOD) of 3.27 pg/mL, and a total assay turnaround time of less than 15 minutes. A spike-and-recovery test using cTnI-spiked human serum yielded a recovery accuracy exceeding 93%. In vivo studies in rats demonstrated ISF cTnI levels of 3 {+/-} 0.4 pg/mL in controls and 912 {+/-} 683 pg/mL in experimental animals, indicating an increasing trend consistent with serum concentrations measured using a clinical immunoassay. These results support the potential of MiCaP as a minimally invasive biosensing platform for cardiac biomarker monitoring, with possible extension to multiplexed ISF-based diagnostics in POC.

bioengineering↗

bioRxiv2023

Variable and reversible opacification process on IOLs for cataract simulation

Understanding vision through mild and dense cataracts is important for vision scientists and IOL developers. There have been virtual simulators using VR headsets for subjective evaluation of cataractous vision. However, a physical intraocular lens with variable cataracts for objective evaluation is not available. In this study, we developed a reversible process that can be selectively applied to the whole or parts of an IOL to affect the opacification level. We used our eye model and developed a cataractous lens simulator for progressive levels of opacification, which is achieved by applying a reversible chemical procedure on the intraocular lens surfaces. After the lens is fully or partially immersed in acetone, subsequent testing of the lens in distilled water results in a progressive change in opacification level within minutes. We measured the quality of vision by obtaining modulation transfer function curves, transmission, and spectroscopic measurements at different opacification levels. By simulating variable opacification across the IOLs, we tested how vision changes from less dense to more dense cataractous regions in a holographic display system with programmable small exit pupils. All results were consistent with the expected vision degradation caused by natural opacification.

bioengineering↗