Dual-Needle Field-Effect Transistor Biosensor for In Vivo pH Monitoring

Local pH of the brain microenvironment is a prominentindicatorfor assessing health status and is closely related to many diseases;therefore, the development of effective in vivo pH methods is of greatimportance. This work demonstrates a dual-needle biosensor based ona solution-gate field-effect transistor (FET) for selective and sensitivemonitoring of pH in cerebrospinal fluid in the central nervous system.The sensor consists of two parts: a needle FET modified with high-puritycarbon nanotubes for electrical signal conduction and a needle gatemodified with polyaniline for specific pH response. Based on the device'sspecific shape and sensing characteristics, the dual-needle sensoris sensitive to the measurement of pH in the living brain while maintainingexcellent stability. The prepared dual-needle biosensor exhibits ahigh Nernstian response of 53.7 mV/pH over a wide pH range from 4.0to 9.0 and excellent selectivity toward pH against other potentialinterfering species in the brain. Either in the case of directly injectingweak acids and bases into the rat brain or in the constructed acuteacid-base poisoning model, the dual-needle biosensor can respondsensitively to the pH changes of the rat brain. This work has produceda unique dual-needle FET biosensor with high reliability and stability,which provides a new method for real-time monitoring of dynamic pHchanges in the body.