Ascend 600 m

Firstly, 1.00 g of HA was dissolved in 100 mL of ultrapure water, and 0.56 g sodium periodate was added and stirred for 24 h under dark conditions at room temperature. After the reaction, 1 mL of ethylene glycol was added to the solution and stirred for an additional hour to neutralize the excess sodium periodate. Finally, the solution was purified by dialysis (MWCO: 8000 Da) using a large amount of ultrapure water for 2 days (3 times a day, 1 L each time). The final product was lyophilized and kept in a dryer for further use. The chemical structure of AHA was characterized by ¹H NMR (Ascend 600 M, BRUKER, Ettlingen, Germany), and FTIR (Nicolet 6700, Thermo Nicolet Corporation, Madison, WI, USA).

The fabrication of DAHA was improved according to the preparation method in the literature [32 (link)]. A total of 1.00 g of AHA was dissolved in 100 mL of phosphate-buffered saline (PBS, pH = 5.0) followed by adding DA of equal molar (AHA/DA = 1:1) and stirring for 10 h with the protection of nitrogen and under dark conditions at room temperature. The specific preparation scheme is shown in Table S3. The reaction solution was dialyzed against ultrapure water for 3 days. During the dialysis, the dialysate was measured by UV-vis (SHIMADZU UV-1900i, Shimadzu, Kyoto, Japan) to ensure that the free DA was removed completely. The final product was lyophilized and kept in a dryer for further use. The chemical structure of DAHA was characterized by ¹H NMR (Ascend 600 M, BRUKER, USA), FTIR (Nicolet 6700, Thermo Nicolet Corporation, Madison, WI, USA), and UV-vis (SHIMADZU UV-1900i, Shimadzu, Kyoto, Japan). The absorbance of DAHA solution with a known concentration at 280 nm was measured, and the standard curve of DA was calculated using UV-vis.