Intermolecular interaction and morphology investigation of drug loaded ABA-triblock copolymers with different hydrophilic/lipophilic ratios

Copolymers with different hydrophilic/lipophilic ratios (HLR) were used to optimize the compatibility between polymer as drug carrier and quercetin as lipophilic drug. Synthesis of amphiphilic triblock copolymers (TC) of poly(butylene adipate)-poly(ethylene glycol)-poly(butylene adipate) (PBA-PEG-PBA) with different PBA molecular weights is the first approach for this purpose. Polymerization and structural features of the polymers were analyzed by different characterization techniques (GPC, (1)H NMR and FT-IR). Formation of hydrophobic and hydrophilic domains with different ratios in the ABA-triblock copolymers was studied by (1)H NMR. The sunflower-like nanoparticles were prepared by self-assembling of the amphiphilic copolymers in the aqueous solution. The hydrophobic PBA segments formed the central solid-like core which stabilized by the hydrophilic PEG rings. The optimum HLR for these copolymers was determined on the basis of drug release time and profile, obtained from freeze-dried nanoparticle powders. The results indicated that optimum HLR for the sustained quercetin release obtained at higher molecular weight of polyesteric domains. Zeta potential measurements showed that the nanoparticle size was close related to the initial concentrations of the nanoparticle dispersions and the compositions of the triblock copolymers. Moreover, TEM pictures showed that the nanocarriers morphologies were changed by changing HLR of triblock copolymers. The PBA-PEG-PBA nanoparticles also showed good drug loading properties, suggesting that they were very suitable as delivery devices for hydrophobic drugs.