Polyhydroxyalkanoate-based amphiphilic diblock copolymers as original biocompatible nanovectors
Résumé
Polyhydroxyalkanoate-based diblock copolymers, poly(β-malic acid)-b-poly(3-hydroxybutyrate) (PMLA-b-PHB), featuring different sizes of segments have been synthesized, for the first time, in two steps and in grams quantity. First, the controlled sequential ring-opening polymn. of β-butyrolactone (BL, in bulk) followed by benzyl β-malolactonate (MLABe, in toluene) has been achieved with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) to afford well-defined poly(benzyl β-malolactonate)-b-poly(3-hydroxybutyrate) (PMLABe-b-PHB) copolymers. A subsequent hydrogenolysis of β-benzyloxycarbonyl units afforded the corresponding PMLA-b-PHB amphiphilic copolymers, as evidenced by 1H, 13C\1H\ and DOSY NMR, SEC, TGA, DSC and contact angle analyses. Next, PMLA-b-PHB copolymers featuring different hydrophilic wt. fractions (10-65%) self-assembled in PBS upon nanopptn. Nano-objects with narrow size distributions (Dh = 17-180 nm; 0.19 \textless PDI \textless 0.30) and exhibiting a neg. surface charge (-32 to -52 mV) were obtained as characterized by DLS, zeta potential, and TEM analyses. Using HepaRG and SK-MEL-28 cells, cytotoxicity studies evidenced no effect on cell viability at low concns. (\textless 88 μg mL-1) while high concns. (88-320 μg mL-1) induced a mild toxicity. Also, high concns. of nanoparticles (ca. 180 μg mL-1) slightly reduced DNA replication while apoptosis measured with DEVD-AMC caspase activity remained unaffected, thus suggesting a moderate cytostatic effect of the nanoparticles without induction of cell death. Furthermore, HepaRG cells were found to efficiently uptake PMLA-b-PHB-based nanoparticles. All these results demonstrated that PMLA-b-PHB copolymers are promising candidates as drug-delivery systems.