Development of albumin monitoring system with hepatic hypoxia-on-a-chip.

Hypoxia plays an essential role in the pathogenesis of various liver diseases, and albumin is one of the important biomarkers secreted by the liver. In this study, we developed an albumin monitoring system composed of hepatic hypoxia-on-a-chip and an albumin sensor to study liver function change due to hypoxia. In hepatic hypoxia-on-a-chip, we vertically stack an oxygen-scavenging channel on a liver on a chip with a thin gas-permeable membrane in the middle. This unique design of the hepatic hypoxia-on-a-chip can help to induce hypoxia quickly, attaining <5% within 10 min. An electrochemical albumin sensor was fabricated based on the covalent immobilization of antibodies on the Au electrode to monitor albumin secreting function on the hepatic hypoxia-on-a-chip. Standard albumin samples spiked in PBS, and culture media were measured by the electrochemical impedance spectroscopy using the fabricated immunosensor. The LOD was calculated to be 10 ag/mL in both cases. Using the electrochemical albumin sensor, we measured albumin secretion in normoxia and hypoxia in the chips. The albumin concentration decreased to 27% after 24 h in hypoxia compared to normoxia. This response was consistent with physiological studies. With technical refinements, the present albumin monitoring system can be a powerful tool in studying hepatic hypoxia with real-time liver function monitoring.

Batteryless, Miniaturized Implantable Glucose Sensor Using a Fluorescent Hydrogel.

We propose a biomedical sensor system for continuous monitoring of glucose concentration. Despite recent advances in implantable biomedical devices, mm sized devices have yet to be developed due to the power limitation of the device in a tissue. We here present a mm sized wireless system with backscattered frequency-modulation communication that enables a low-power operation to read the glucose level from a fluorescent hydrogel sensor. The configuration of the reader structure is optimized for an efficient wireless power transfer and data communication, miniaturizing the entire implantable device to 3 × 6 mm 2 size. The operation distance between the reader and the implantable device reaches 2 mm with a transmission power of 33 dBm. We demonstrate that the frequency of backscattered signals changes according to the light intensity of the fluorescent glucose sensor. We envision that the present wireless interface can be applied to other fluorescence-based biosensors to make them highly comfortable, biocompatible, and stable within a body.