Ring-opening polymerization-mediated controlled formulation of polylactide-drug nanoparticles.
We report here a unique method for formulating doxorubicin-polylactide (Doxo-PLA) conjugate nanoparticles, known as nanoconjugates (NCs), through Doxo/(BDI)ZnN(TMS)(2)-mediated [(BDI) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)-imino)-2-pentene], chemo- and regioselective polymerizations of lactide (LA) followed by nanoprecipitation. When Doxo/(BDI)ZnN(TMS)(2) was mixed with 1-pyrenemethanol (Pyr-OH) and 1-pyrenemethylamine (Pyr-NH(2)) and the mixture was utilized for the polymerization of LA, remarkable chemoselectivity was observed. Pyr-OH was completely consumed and covalently linked to the terminus of the PLA, whereas the Pyr-NH(2) remained intact in the polymerization solution. When Doxo was used as the initiator to polymerize LA in the presence of (BDI)ZnN(TMS)(2), the polymerization was complete within hours, with nearly 100% Doxo-loading efficiency and 100% LA conversion. Doxo loading as high as 27% could be achieved at a LA/Doxo ratio of 10. Both the steric bulk of the chelating ligand and the metal catalyst had dramatic effects on the regioselectivity during the initiation step. When Doxo/(BDI)ZnN(TMS)(2) was mixed with succinic anhydride (SA) to mimic the initiation of Doxo/(BDI)ZnN(TMS)(2)-mediated LA polymerization, Doxo-14-succinic ester (Doxo-SE) was the predominate product. When the steric bulk of BDI was reduced or when the BDI ligand was removed, significant amounts of Doxo-4',14-bis-succinic ester (Doxo-2SE) and Doxo-4',9,14-trisuccinic ester (Doxo-3SE) were formed. The use of (BDI)MgN(TMS)(2) in such a reaction also resulted in reduced regioselectivity and formation of both Doxo-SE and Doxo-2SE. Doxo/(BDI)ZnN(TMS)(2)-mediated LA polymerizations yielded Doxo-PLA conjugates with well-controlled molecular weights and polydispersities (as low as 1.02). The nanoprecipitation of Doxo-PLA formed NCs less than 150 nm in size with narrow particle size distributions. The sustained release of Doxo from Doxo-PLA NCs was achieved without a burst release. This method may have widespread utility for controlled conjugation of hydroxyl-containing agents to polyesters and formation of corresponding nanoparticles.
Tong
Rong
R
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Cheng
Jianjun
J
D002384:Catalysis; D004317:Doxorubicin / Q000138:chemical synthesis / Q000737:chemistry*; D004337:Drug Carriers / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D008670:Metals / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D011091:Polyesters / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
D004337:Drug Carriers; D008024:Ligands; D008670:Metals; D011091:Polyesters; C033616:poly(lactide); D004317:Doxorubicin