*2.1. Materials*

Granules of PLA (3 mm nominal granule size) and corn starch were purchased from Sigma-Aldrich (St. Louis, MO, USA). Corn starch was dried in an oven to remove excess moisture for 24 h at 70 ◦C before being used. Chloroform (CHCl3), acetone (C3H6O), PEG, ethanol, polyethylene (PE), phosphate buffer (PBS, pH = 7.4), sodium hydroxide (NaOH), hydrochloric acid 37 wt.% (HCl) were purchased from Merck, Darmstadt, Germany, and used without any further purification.
