Effect of PEGylation on the Structure and Drug Loading Capacity of PAMAM-G4 Dendrimers: A Molecular Modeling Approach on the Complexation of 5-Fluorouracil with Native and PEGylated PAMAM-G4

Abstract

Fully atomistic molecular dynamics (MD) simulations have been performed to examine the effect of PEGylation on the structure and drug loading properties of 25%–100% PEGylated poly(amidoamine) (PAMAM)-G4 dendrimers in complex with 5-fluorouracil (5-FU) as a model anticancer compound. Theoretical estimates predict a complex stoichiometry of 23:1 for the 5-FU:PAMAM-G4 system in high agreement with isothermal titration calorimetry and nuclear magnetic resonance (NMR) experiments, thus supporting the validity of our computational approach. MD simulations reveal a progressive increase in the total drug loading capacity as the PEGylation degree becomes higher. In systems with PEGylation degrees ≥50%, drug complexation occurs almost exclusively within outermost polyethylene glycol (PEG) chains, due to their higher affinity toward complexation with 5-FU compared to PAMAM-G4 branches. On the other hand, the 25% PEG-PAMAM-G4 system retains the internal complexation capability of PAMAM-G4 and provides additional assistance for drug retention through the cooperative interaction with back folded PEG chains, appearing as the most suitable option for drug delivery applications.