Different from the 'building block' (recognition unit, signal unit, self-assembly unit, etc.) construction mode of most existing peptide systems . When constructing the peptide library, the synergistic effect of peptide structure and function was fully Since EH system contained labile protons, we envisioned that regulating the pH of the system may alter the charge state of the EH, which may further affect the interaction with the Ag2S . Firstly, the zeta potential of EH and Ag2S at different pH were measured. As shown in Fig. and Fig. , it was found that the EH supramolecular assembly were positively charged in normal physiological conditions (pH 7.4), and the Ag2S were negatively charged whether in normal physiological conditions (pH 7.4) or tumor slightly acidic conditions (pH 6.0). Therefore, we envisaged that EH and Ag2S could co-assemble to form supramolecular structures through electrostatic adsorption interaction at pH 7.4. By adjusting the mass ratio of EH and Ag2S (Fig. ), we tried to make Ag2S adsorb on the EH fiber surface without affecting the formation process of EH fibers. Through our experiments, when EH was mixed with the Ag2S at mass ratios of 4:1, Ag2S and EH scattered on the surface of mica slices. We speculated that the high content of Ag2S affected the longitudinal growth of EH fibers. When the mass ratio was adjusted to 5:1, EH nanofiber could be observed to start growing. When the mass ratio was adjusted to 10:1, stable short fibers of EH could be observed. However, the distribution of Ag2S on EH was not enough. When the mass ratio was 20:1, Ag2S could be uniformly distributed on the nanofibers to construct EH@Ag2S co-assembly. The morphology of EH@Ag2S was observed by AFM and TEM. It was found in Fig. and Fig. that Ag2S could be uniformly distributed on the nanofibers. The sizes of the EH@Ag2S were measured by dynamic light scattering (DLS). DLS showed two peaks, i.e., 30 and 3100 nm, which indicated the diameter and the length of the EH@Ag2S (Fig. ). The formation of co-assembled system EH@Ag2S was also confirmed by energy dispersive spectroscopy (EDS) mapping with the distribution of C, N, O, Ag and S. Through experiments, it was found that large amounts of Ag2S were dispersed on the surface of nanofibers. C, N, O, Ag, and S exhibited the high uniformity of each element distribution (Fig. ). In addition, to verify whether the co-assembly affects the affinity of EH for PD-L1, we determined the binding affinity of the EH@Ag2S co-assemblies using SPRi. The results showed that the KD of EH@Ag2S for PD-L1 was 6.67 × 10 -7 M (Fig. ), similar to the affinity of EH for PD-L1 (KD=7.79 × 10 -7 M). In subsequent experiments, we adjusted the pH of the system to less than 6.0 and found that decreased pH led to charge reversal of EH supramolecular assembly. At shown in Fig. , the surface charge of EH supramolecular assembly and Ag2S was negatively charged, leading to the electrostatic attraction between the Ag2S and EH disappeared. This result was also confirmed by AFM and TEM image in Fig. and Fig. , co-assembled system EH@Ag2S could not be observed when the pH changed to less than 6.0. EH and the Ag2S were randomly scattered on the substrate. We speculated that Ag2S could be released from the co-assembled system EH@Ag2S as the pH decreased less than 6.0. Overall, it could be concluded that electrostatic attraction was the main factor driving the formation of EH@Ag2S.