Interactions of Poly(amidoamine) Dendrimers with Human Serum Albumin: Binding Constants and Mechanisms

Abstract

The interactions of nanomaterials with plasma proteins have a significant impact on their in vivo transport and fate in biological fluids. This article discusses the binding of human serum albumin (HSA) to poly(amidoamine) [PAMAM] dendrimers. We use protein-coated silica particles to measure the HSA binding constants (K b) of a homologous series of 19 PAMAM dendrimers in aqueous solutions at physiological pH (7.4) as a function of dendrimer generation, terminal group, and core chemistry. To gain insight into the mechanisms of HSA binding to PAMAM dendrimers, we combined 1H NMR, saturation transfer difference (STD) NMR, and NMR diffusion ordered spectroscopy (DOSY) of dendrimer−HSA complexes with atomistic molecular dynamics (MD) simulations of dendrimer conformation in aqueous solutions. The binding measurements show that the HSA binding constants (K b) of PAMAM dendrimers depend on dendrimer size and terminal group chemistry. The NMR 1H and DOSY experiments indicate that the interactions between HSA and PAMAM dendrimers are relatively weak. The 1H NMR STD experiments and MD simulations suggest that the inner shell protons of the dendrimers groups interact more strongly with HSA proteins. These interactions, which are consistently observed for different dendrimer generations (G0-NH2 vs G4-NH2) and terminal groups (G4-NH2 vs G4-OH with amidoethanol groups), suggest that PAMAM dendrimers adopt backfolded configurations as they form weak complexes with HSA proteins in aqueous solutions at physiological pH (7.4).

Spectroscopic and calorimetric studies of formation of the supramolecular complexes of PAMAM G5-NH2 and G5-OH dendrimers with 5-fluorouracil in aqueous solution

“…S1) as well as the mixtures of this drug and PAMAM G5-OH (Fig. S2) in heavy water as in previous 1 H NMR studies of PAMAM-NH 2 (Bányai et al, 2013;Barra et al, 2014a,b;Buczkowski et al, 2012bBuczkowski et al, , 2013Cao et al, 2013;Giri et al, 2011;Hu et al, 2010Hu et al, , 2012Keri et al, 2015) and PAMAM-OH dendrimers (Choi et al, 2012;Giri et al, 2011;Gomez et al, 2009a,b;Hu et al, 2012;Pellechia et al, 2004;Wang et al, 2013). With increasing the concentration of 5-fluorouracil in the mixture of drug and dendrimer one can observe that peak at 2.6 ppm corresponding to the protons of methylene groups present at tertiary amine groups is not clearly shifted during the drug bonding by cationic PAMAM G5-NH 2 dendrimer (Fig.…”

Aggregation is a critical cause of poor transfer into the brain tissue of intravenously administered cationic PAMAM dendrimer nanoparticles

“…29 In the case of dendrimers, previous studies have demonstrated that a few molecules of dendrimers and one molecule of albumin form an assembly, which is sustained for a long period of time. 30,31 These reports partially lend support to the results of our initial FCS, which indicated that cationic dendrimers and HSA formed 1:1 assemblies in PBS (-). Our further FCS analysis, however, revealed that mixing of HSA in PBS (+) led to the formation of dendrimer aggregates of submicron-or larger sizes.…”

Refractory dissolved organic nitrogen accumulation in high-elevation lakes

“…4c) differentiate these samples from typical DOM. Closer inspection reveals that many of these largest peaks are consistent with protein resonances 23,24 .…”