HSA (50 mg) was accurately weighed, dissolved in 9 mL of pure water, and stirred magnetically in a 20 mL reaction flask. Approximately 20–40 mg of EDC and NHS were added into the reaction flask, and the duration of the activation reaction was 15 min. Next, NH2-PEG4000-NH2 (150 mg) and PBS (1 mL) were added to the reaction flask for 24 h. Following reaction, the material was placed in ultrapure water for dialysis and purification to obtain PHSA and stored in a refrigerator at 4°C.