Biophysical Characterization of a Riboflavin-Conjugated Dendrimer Platform for Targeted Drug Delivery

The present study describes the biophysical characterization of generation-five poly(amidoamine) (PAMAM) dendrimers conjugated with riboflavin (RF) as a cancer targeting platform Two new series of dendrimers were designed, each presenting the riboflavin ligand attached at a different site (isoalloxazine at N-3 and D-ribose at N-10) and at varying ligand valency. Isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) were used to determine the binding activity for riboflavin binding, protein (RfBP) in a cell free solution. The ITC data shows dendrimer conjugates have K-D values of >= 465 nM on a riboflavin basis, an affinity similar to 93-fold lower than that of free riboflavin. The N-3 series showed greater binding affinity in comparison with the N-10 series. Notably, the affinity is inversely correlated with ligand valency. These findings are also corroborated by DSC where greater protein-conjugate stability is achieved with the N-3 series and at lower ligand valency.