Influence of dendrimer surface chemistry and pH on the binding and release pattern of chalcone studied by molecular dynamics simulations.

Poly(amidoamine) (PAMAM) dendrimers are promising nanocarriers that can enhance the solubility of hydrophobic drugs. The surface chemistry of dendrimers is of great relevance as end groups of these nanocarriers can be easily modified to improve the bioavailability and sustained release of the cargo. Therefore, a molecular-level understanding of the host-guest interactions that can give both qualitative and quantitative information is particularly desirable. In this work, fully atomistic molecular dynamics simulations were used to study the association of a bioactive natural product, ie, chalcone, with amine-, acetyl-, and carboxyl-terminated PAMAM dendrimers at physiological and acidic pH environments. Amine- and carboxyl-terminated PAMAM dendrimers have an open microstructure at low pH that is not able to hold the ligand tightly, resulting in an unfavorable encapsulation of the chalcone molecule. In the case of acetyl-terminated dendrimer, chalcone molecule diffuses out of the dendritic cavities a few times during the simulation time and prefers to locate close to the surface of dendrimer. Average center of mass distance values at neutral pH showed that the chalcone molecule bounds firmly in the internal pockets of amine-, acetyl-, and carboxyl-terminated dendrimers and forms stable complexes with these nanovectors. The potential of mean force calculations showed that the release of the ligand from the dendrimers occurs at a controlled rate in the body.