Click Modification of Multifunctional Liposomes Bearing Hyperbranched Polyether Chains

Aiming at controlled modification of liposomal surface structures, we describe a postpreparational approach for surface derivatization of a new type of multifunctional, sterically stabilized liposomes. Application of dual centrifugation (DC) resulted in high encapsulation efficiencies above 50% at very small batch sizes with a total volume of 150 μL, which were conductive to fast and efficient optimization of variegated surface modification reactions. Cholesterol-polymer amphiphiles, including complex hyperbranched polyether structures bearing 1–4 terminal alkynes, were used in DC formulations to provide steric stabilization. The alkyne moieties were explored as anchors for the conjugation of small molecules to the liposomal surface via click chemistry, binding 350–450 fluorophores per liposome as examples for surface active molecules. Using Forster resonance energy transfer (FRET) spectroscopy, the conjugation reaction as well as the uptake of FRET-labeled liposomes by RBE4 cells was monitored, and the d...