Fig. 4: Performance of HG-LGS in Phe-Gly-Gly detection and quantitative CO₂ release.

a Schematic for quantifiable visual detection based on the distance signal readout. b Time-dependent marker advancement with different concentrations of Phe-Gly-Gly. c Linear standard curves obtained from 0 to 100 μM Phe-Gly-Gly in 1 min. Inserts: Images showing marker advancement at various concentrations of Phe-Gly-Gly in 1 min. d Quantifiable visual CO₂ release based on the color signal readout. Left: Plots of CO₂ emission against the Phe-Gly-Gly concentration. Right: Illustration of the color signal readout by the HG-LGS. Error bars represent standard deviations (n = 3).