**2.4. Water absorbability**

The lyophilized PAQ composite samples were soaked in phosphate‐buffered saline (PBS, pH 7.4) and acetic acid/sodium acetate buffer (HAc‐NaAc, pH 5.0). At different assigned times, the sample was taken out and the excessive solution on the surface of the sample was removed by Kimwipes. The water absorbability was the ratio of weight difference of lyophilized sample before and after the soaking versus the weight of lyophilized sample (the amount of adsorbed water vs. dry weight of lyophilized sample).
