Molecular insights into the binding of human serum albumin to charged dendritic nanomicelles: A synergistic experimental and in silico approach

Understanding the interaction between dendritic nanostructures and plasma proteins is critical for optimizing their in vivo behavior and biocompatibility. In this study, we investigate the binding of human serum albumin (HSA) to a set of amphiphilic poly(amidoamine) dendrimers, both as individual monomers and as self-assembled charged nanomicelles (1@-A, 1@-TA, and 1@-COOH). A comprehensive set of techniques, including fluorescence spectroscopy, circular dichroism, isothermal titration calorimetry, dynamic light scattering, and atomistic molecular dynamics simulations, was employed to assess binding affinity, conformational effects, and complex stoichiometry resulting from the interactions between the serum protein and the dendritic nanostructures. Isothermal titration calorimetry quantified stronger HSA binding for nanomicelles (Kd = 1.15 ± 0.64 μM for 1@-A; 4.29 ± 0.57 μM for 1@-COOH; 8.10 ± 0.11 μM for 1@-TA) relative to monomers (Kd = 112 ± 11, 89 ± 21, and 104 ± 18 μM for 1-A, 1-TA, and 1-COOH, respectively). The thermodynamic signatures differed markedly: nanomicelles exhibited favorable enthalpy (ΔH = −4.07 ± 0.05 to −6.53 ± 0.04 kcal/mol) with modest entropic contributions (−TΔS = −4.09 ± 0.40 to −0.80 ± 0.04 kcal/mol), whereas monomers were entropy-driven (ΔH = +2.88 ± 0.14 to +3.12 ± 0.10 kcal/mol; −TΔS = −8.51 ± 0.21 to −8.41 ± 0.23). Spectroscopic analyses indicated that HSA retained its secondary and tertiary structures upon interaction and confirmed the formation of stable protein–nanomicelle complexes. Computational modeling revealed distinct interaction patterns at the HSA–nanomicelle interface. Together, these findings demonstrate how the structural and surface properties of dendritic nanomicelles can modulate their interaction with proteins, offering valuable insights for future design strategies. Given that the formation of a soft protein corona, especially around micelles, plays a pivotal role in protein–nanomaterial interactions, the results presented here may constitute a key step toward the rational design of next-generation nanomedicine platforms.