Interplay of nanointerface curvature and calcium binding in weak, polyelectrolyte-coated nanoparticles

GONZALEZ SOLVEYRA, ESTEFANIA; NAP, RIKKERT J.; SZLEIFER, IGAL

Orlando

Congreso; ACS Spring meeting 2019; 2019

American Chemistry Society

When engineering nanomaterials for application in biological systems, it is important to understand how multivalent ions, such as calcium, affect thestructural, thermodynamic, and chemical properties of polymer-modified nanoconstructs. In this work, a recently developed molecular theory was employedto study the effect of surface curvature on the calcium-induced collapse of end-tethered weak polyelectrolytes. In particular, we focused on cylindrical andspherical nanoparticles coated with poly(acrylic acid) in the presence of different amounts of Ca ions. We describe the structural changes of polymercoatednanoparticles as a function of calcium concentration, surface curvature, and morphology. The polymer layers collapse in aqueous solutions thatcontain sufficient amounts of calcium. The collapse of end-tethered pAA layers, due to formation of calcium bridges, is strongly dependent on the pH of thesolutions as well as divalent and monovalent salt concentrations of the reservoir solution. However, it is also strongly influenced by the curvature or radius ofthe tethering surface. The transition from a swollen to a collapsed layer as function of calcium concentration broadens and shifts to lower amounts ofcalcium ions as radius of NP increase (Fig. 1). The results show how the interplay between calcium binding and surface curvature governs the structural andfunctional properties of the polymer molecules. This would directly impact the fate of weak polyelectrolyte-coated nanoparticles in biological environments,in which calcium levels are tightly regulated.