Synthesis of multiarm star copolymers based on polyglycerol cores with polylactide arms and their application as nanocarriers†
Hyperbranched polyglycerol (hPG) with two different molecular weights (hPG2400 and hPG8000) was used as a macroinitiator for the polymerization of lactide. Thereby, amphiphilic linear-dendritic multiarm star copolymers (MSCs) were prepared and investigated with regard to their ability to encapsulate and transport guest molecules. Various ratios of monomer to hydroxy functional end groups ([LA]/[OH]) were used for the preparation of linear-dendritic multiarm copolymers with different degrees of polymerization (DP), molecular weight, and arm multiplicity. At high molecular weights almost all of the hydroxy groups of hPG were reacted with the lactide monomer and the number of arms was equal to the number of hydroxy functional groups. The ability of the synthesized MSCs to encapsulate and transport small guest molecules was examined. The transport capacity (TC) of all nanocarriers under different conditions was investigated using the model dye Congo red as well as the model drug 5-aminosalicylic acid (5-ASA). With both hPG2400 and hPG8000 cores, the TC increased along with an increasing number and length of the arms. The dependence of the TC on the concentration of MSCs was also investigated and found to deteriorate with increasing polymer concentration. Finally the ability of the synthesized nanocarriers to penetrate into the skin and transport Nile red through this barrier was successfully investigated.