Application of a GaAs-Based Sensor for Detecting Hemoglobin in Gastrointestinal Environments

In clinical applications, inspection of the hemorrhagic spots in the gastrointestinal (GI) tract is a challenging task. The hybrid GaAs-based device, developed by us, has been successfully used for sensing hemoglobin (Hb) in biological solutions. In this paper, a new method and apparatus were applied for using the GaAs-based sensor to detect Hb in a mimicked gastrointestinal circumstance. A surface protection layer of polymerized thiolated silanes was deposited on the top of the device to obtain a chemical passivation coating against surface etching and to achieve bio-compatibility. A selective device functionalization was achieved by the subsequent adsorption of Hb antibodies on the top of the protection layer. An integrated sensor containing two different antibodies enabled examining its selectivity to purely Hb. In vitro testing of the sensor indicated that it is capable of discriminating fasted-state simulated intestinal fluids when the concentration of Hb was above $10~\mu \text{g}$ /mL. Moreover, the sensor was capable of detecting Hb in swine intestinal fluids with the same sensitivity. This paper verified the feasibility to apply the sensor in clinical use, by embedding it on different types of endoscopes, in order to localize GI bleeding with high precision and sensitivity.