A self-assembled nanocomplex from starch-protein- fatty acid: Thermodynamics of self-assembly

A self-assembling, nanoscale complex formed from common biological molecules, starch, proteins, and fatty acids, was previously reported by our group. While the formation of this nanocomplex has been confirmed using various analytical techniques, its thermodynamic distinctiveness compared to conventional nano-emulsion systems has not yet been explored. This study aims to provide a physicochemical understanding of the self-assembly process by evaluating changes in thermodynamic properties, enthalpy, entropy, and the Gibbs free energy during complex formation. Interactions among these biological molecules, mixed in specific ratios, were monitored using modulated differential scanning calorimetry (MDSC). Changes in the reversing heat capacity during the initial cooling cycle were used to calculate the entropic and the Gibbs free energy changes associated with self-assembly. Applying classical equilibrium thermodynamics, it was demonstrated that the presence of protein thermodynamically favored the formation of a higher-order nanostructure, distinguishing it from typical emulsion systems. Moreover, this structure is more stable than binary complexes such as amylose-fatty acid and protein-fatty acid assemblies. Our findings provide compelling evidence that these self-assembling nanoscale complexes are not only chemically viable but also thermodynamically favored and stable.