Figure 1

(A) Schematic illustration of mediated electron transfer pathways catalyzed by Fd-Glts[43]. Reproduced with permission of Ref. 43, copyright 2018 American Chemical Society. (B) Schematic illustration of aptCFE and typical current response of in vivo DA dynamics upon electrical stimulation[46]. Reproduced with permission of Ref. 46, copyright 2020 WILEY-VCH. (color on line)

Figure 2

(A) (a-b) HAADF-STEM image (a) and EXAFS fitting curve (b) of Co-N4/C. (c) Relative current ratio of H2O2 to O2 recorded by three catalysts shown in the figure, and (d) in vivo O2 fluctuation recorded by Co-N4/C-based sensor[60]. Reproduced with permission of Ref. 60, copyright 2020 American Chemical Society. (B) (a-b) Schematic illustration of fabrication process (a) and stretching process (b) of Ni SAC/N-C-based sensor. (c) Real-time monitoring of NO release[61]. Reproduced with permission of Ref. 61, copyright 2020 Springer Nature. (C) (a) Schematic illustration of online electrochemical system (OECS) with a SAC-based electrochemical sensor for continuous glucose monitoring, and (b) typical amperometric response of OECS toward microdialysate in vivo sampled from rat brain[62]. Reproduced with permission of Ref. 62, copyright 2019 Springer. (color on line)

Figure 3

(A) Schematic illustration of Pd/GDY formation via electroless deposition[64]. Reproduced with permission of Ref. 64, copyright 2015 American Chemical Society. (B) TEM image (a), HRTEM image (b), STEM image (c), FFT pattern (d) and AFM images (e-f) of exfoliated GDY[65]. Reproduced with permission of Ref. 65, copyright 2019 WILEY-VCH. (C) (a) Schematic illustration of bonding model between water molecules and carbon nanomaterials (i.e., GO and GDYO). (b) Normalized current responses of GDYO-based sensor towards different human respiratory patterns[66]. Reproduced with permission of Ref. 66, copyright 2018 WILEY-VCH. (D) (a) Construction of the mediated biosensor interface and (b) typical amperometric responses to glucose and other neurochemicals[67]. Reproduced with permission of Ref. 67, copyright 2020 American Chemical Society. (color on line)

Figure 4

(A) (a) Typical current-voltage responses acquired by using bare micropipette (black curve) and PimB-modified micro-pipette (red curve). (b) Schematic illustration of proposed three-layer model[69]. Reproduced with permission of Ref. 69, copyright 2017 American Chemical Society. (B) Schematic illustrations of (a) experimental setup of in vivo pH sensing by using PvimB-modified micropipette and (b) transient ion transport behaviors and generated ion currents under high-frequency pulse potential[72]. Reproduced with permission of Ref. 72, copyright 2021 Royal Society of Chemistry. (color on line)

Figure 5

(A) Schematic illustration of GRP sensor[80]. (B) Schematic illustration of orientation and cyclic voltammograms of untreated and ethanol-treated laccase on SWCNT/GCE[79]. Reproduced with permission of Ref. 79, copyright 2017 American Chemical Society. (C) (a) Schematic illustration of GRP sensor for in vivo sensing of AA. (b) Calibration curves of the GRP sensor before and after BSA absorption. (c) Real-time recording of cortical AA level during global cerebral ischemia (red arrow) and reperfusion (blue arrow)[80]. Reproduced with permission of Ref. 80, copyright 2018 American Chemical Society. (D) (a) Schematic illustration of the single-carbon-fiber-powered microsensor and in vivo sensing of AA with the microsensor. (b) Change in open circuit voltage (OCV) after adding AA and interferents. (c) In vivo synchronous OCV measurement with the microsensor and electrophysiological recording by the MEA[81]. Reproduced with permission of Ref. 81, copyright 2020 WILEY-VCH. (color on line)

Figure 6

(A) (a) Current signals recorded with CFEAA1.0 under different bias voltages and (b) in vivo sensing of AA in the rat cortex during SD process[84]. Reproduced with permission of Ref. 84, copyright 2019 WILEY-VCH. (B) Schematic illustration and typical current responses of in vivo AA release in rat brain by using CFEAA2.0[85]. Reproduced with permission of Ref. 85, copyright 2020 American Chemical Society. (color on line)