Generation-dependent encapsulation/electrostatic attachment of phenobarbital molecules by poly(amidoamine) dendrimers: Evidence from 2D-NOESY investigations

The interactions of phenobarbital with different generations of amine-terminated poly(amidoamine) (PAMAM) dendrimers were investigated by using two dimensional-nuclear Overhauser effect spectroscopic (2D-NOESY) investigations. The NOESY spectra clearly showed that there were cross-peaks from NOE interactions between the protons of phenobarbital and the protons in interior cavities of generation 5 or generation 6 PAMAM dendrimers but none of such cross-peaks was found in the case of generation 3 or generation 4 dendrimers. The NOESY analysis, together with aqueous solubility data, suggested that higher generation dendrimers are more capable of encapsulating phenobarbital molecules into the interior cavities than lower generation dendrimers, and that lower generation dendrimers are much easier for the electrostatic attachment of phenobarbital molecules than higher ones at a fixed mass concentration.