Figure 2.

Fabrication of fluorescent nanodiamond hydrogel for glucose sensing. A) FTIR spectra of unmodified nanodiamond (1), octadecylamine modified nanodiamond (2), and octadecylamine modified nanodiamond with alkene surface group (3). The cross‐section (B) and top view (C) of the confocal images show that the glucose molecules can reversibly trigger the swelling of the hydrogel in vitro. D) In vitro fluorescence imaging shows that the nanodiamond hydrogel has higher fluorescent emission in the presence of glucose (500 mg dL⁻¹) compared with phosphate‐buffered saline (PBS) solution. E) Fluorescent emission of the nanodiamond based hydrogel shows strong correlation with glucose concentration in vitro, n = 3. Data are presented as mean ± standard deviation (SD). All error bars represent SD. F) Compared with the classical Con A glucose‐responsive hydrogels, the nanodiamond based hydrogels exhibited excellent photostability in vitro, n = 4. Data are presented as mean ± SD. All error bars represent SD.