*3.1. Materials*

D,L-lactide was provided by Corbion (Gorinchem, The Netherlands). Tin (II) 2- ethylhexanoate (Sn(Oct)2, 95%), pentaerythritol, diethylene glycol (DEG), (3-isocyanatopropyl) triethoxysilane (IPTES), dichloromethane, heptane, toluene, tetrahydrofuran, hydrochloric acid (37%) and hydrochloric acid (37%) (1 M in methanol), dichloromethane (DCM), trifluoroethanol, trifluoroacetic acid and phosphate buffer solution (PBS) were purchased from Sigma-Aldrich (St Quentin Fallavier, France).

CellTiter Glo assay was provided by Promega G7571 (Charbonnières-les-Bains, France). PrestoBlue® assay (A13262) and Clariostar plate reader (A13626) were acquired from Invitrogen (Illkirch, France). Negative RM-C and positive RM-A were supplied by Hatano Research Intitue, Food and Drug Safety Center, Hadano, Japan).

#### *3.2. Synthesis of Linear and 4-Arm Star Poly(Lactide)*

We synthesized LinearPLA of 200 kg·mol−<sup>1</sup> and 4-arms StarPLA of 25 kg·mol−1, 12 kg·mol−<sup>1</sup> and 5 kg·mol−1, i.e., LinearPLA200k, StarPLA25k, StarPLA12k and StarPLA5k, respectively. Polymers were synthesized by ring opening polymerization, using a procedure previously described [31]. Typically, for the synthesis of StarPLA-25k: D,L-lactide (30 g, 208 mmol, 14 eq), pentaerythritol as multifunctional initiator (0.163 g, 1.19 mmol, 1 eq) and SnOct2 as catalyst (0.194 g, 4.79 mmol, 0.4 eq) were introduced in a flask. After 2 h under vacuum, the flask was sealed and maintained at 120 ◦C for five days. The obtained polymers were solubilized in DCM and then precipitated in cold heptane (4 ◦C). Finally, the recovered polymer was vacuum dried overnight. The average reaction yields were 88 ± 9%. StarPLA12k and StarPLA5k were obtained by varying the molar ratio monomers/initiator: 20.8 and 8.67 respectively. The linearPLA200k was synthesized with the same protocol of polymerization of the StarPLA, but this time using diethylene glycol as initiator in a monomer/initiator molar ratio of 694.4. The molecular weight of the StarPLAs was determined by 1H-NMR from the signal ratio between methylene protons of pentaerythritol and the methyl proton of the lactic unit.

1H-NMR (400 MHz, CDCl3) δ (ppm) = 5.15 (m, C **H**CH3); 4.34 (m, C **H**CH3OH); 4.14 (s, CC **H**3O); 3.5 (s, CC **H**3OH); 1.54 (m, CHC **H**3)

#### *3.3. Functionalization of 4-Arm Starpoly(Lactide) with Triethoxysilane*

Polymers were functionalized using a procedure previously described [31]. Typically, the StarPLA25k (5 g, 2.5 mmol) was put in a flask under vacuum for 4 h. The polymer was solubilized in anhydrous toluene (100 mL) under inert gas during 1 h. Then, the IPTES (3.71 g, 15 mmol, 6 eq) was added in the solution and SnOct2 as catalyst (0.162 g, 0.4 mmol, 0.16 eq). The reaction was carried out at 75 ◦C, with constant stirring and under inert atmosphere for 24 h. The obtained StarPLA25k-PTES was purified in cold heptane and vacuum dried in order to eliminate traces of solvent. StarPLA12k and StarPLA5k were functionalized using the same protocol as for StarPLA25k.

The degree of functionalization was determined by 1H-NMR from the signal ratio between the methyl lactic proton (δ = 5.1 ppm) and the methylene proton linked to triethoxysilane (δ = 0.6 ppm).

1H-NMR (400 MHz, CDCl3) δ(ppm) = 5.15(m, CHCH3); 4.34(m, CHCH3OH); 4.14 (s, CCH3O); 3.83 (m, OCH2CH3); 3.5 (s, CCH3OH); 3.17 (m, NHCH2); 1.54 (m, CHC **H**3); 1.2 (m, OCH2C **H**3); 0.64–0.54 (m, CH2C **H**2Si).
