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Understanding physiological and pathological processes in the brain requires tracking the reversible changes in chemical signals with long‐term stability. We developed a new anti‐biofouling microfiber array to real‐time quantify extracellular Ca2+ concentrations together with neuron activity across many regions in the mammalian brain for 60 days, in which the signal degradation was < ca. 8 %. The microarray with high tempo‐spatial resolution (ca. 10 μm, ca. 1.3 s) was implanted into 7 brain regions of free‐moving mice to monitor reversible changes of extracellular Ca2+ upon ischemia‐reperfusion processes. The changing sequence and rate of Ca2+ in 7 brain regions were different during the stroke. ROS scavenger could protect Ca2+ influx and neuronal activity after stroke, suggesting the significant influence of ROS on Ca2+ overload and neuron death. We demonstrated this microarray is a versatile tool for investigating brain dynamic during pathological processes and drug treatment. [ABSTRACT FROM AUTHOR]

Herein, we present an electrochemophysiological microarray (ECPM) for real‐time mapping and simultaneous quantification of chemical signals for multiple ions in the deep brain of a freely moving rat, in which microelectrode arrays were developed for direct determination of multiple ions using open‐circuit potentiometry. Specific recognition ionophores were synthesized and optimized for determination of K+, Ca2+, Na+ and pH. A reference electrode was also developed to avoid interferences in the brain. The microarrays were successfully applied in real‐time monitoring and quantification of ions in a live brain. The extra current‐free potentiometry allowed mapping and biosensing of chemical signals, together with recording of electrical signals in the whole brain without cross‐talk, for the first time. Furthermore, the ECPM provided a platform for real‐time monitoring of the dynamic changes of multiple ions in the deep brain of freely moving rat during a seizure. [ABSTRACT FROM AUTHOR]

To have a profound understanding of the physiological and pathological processes in a brain, both chemical and electrical signals need to be recorded, but this is still very challenging. Herein, micrometer‐ to nanometer‐sized SERS optophysiological probes were created to determine both the CO32− concentration and the pH in live brains and neurons because both species play important roles in regulating the acid–base balance in the brain. A ratiometric SERS microarray of eight microprobes with tip sizes of 5 μm was established and used for the first time for real‐time mapping and simultaneous quantification of CO32− and pH in a live brain. We found that both the CO32− concentration and the pH value dramatically decreased under ischemic conditions. The present SERS technique can be combined with electrophysiology without cross‐talk to record both electrical and chemical signals in brains. To deepen our understanding of the mechanism of ischemia on the single‐cell level, a SERS nanoprobe with a tip size of 200 nm was developed for use in a single neuron. [ABSTRACT FROM AUTHOR]

Herein, we develop a novel method for designing electrochemical biosensors with both current and potential signal outputs for the simultaneous determination of two species in a living system. Oxygen (O2) and pH, simple and very important species, are employed as model molecules. By designing and synthesizing a new molecule, Hemin-aminoferrocene (Hemin-Fc), we create a single electrochemical biosensor for simultaneous detection and ratiometric quantification of O2 and pH in the brain. The reduction peak current of the hemin group increases with the concentration of O2 from 1.3 to 200.6 μ m. Meanwhile, the peak potential positively shifts with decreasing pH from 8.0 to 5.5, resulting in the simultaneous determination of O2 and pH. The Fc group can serve as an internal reference for ratiometric biosensing because its current and potential signals remain almost constant with variations of O2 and pH. The developed biosensor has high temporal and spatial resolutions, as well as remarkable selectivity and accuracy, and is successfully applied in the real-time quantification of O2 and pH in the brain upon ischemia, as well as in tumor during cancer therapy. [ABSTRACT FROM AUTHOR]