When engineering nanomaterials for application in biological systems, it is important to understand how multivalent ions, such as calcium, affect the structural, thermodynamic, and chemical properties of polymer-modified nanoconstructs. In this work, a recently developed molecular theory was employed to study the effect of surface curvature on the calcium-induced collapse of end-tethered weak polyelectrolytes. In particular, we focused on cylindrical and spherical nanoparticles coated with poly(acrylic acid) in the presence of different amounts of Ca<sup>2+</sup> ions. We describe the structural changes of polymer-coated nanoparticles as a function of calcium concentration, surface curvature, and morphology. The polymer layers collapse in aqueous solutions that contain sufficient amounts of calcium. The collapse of end-tethered pAA layers, due to formation of calcium bridges, is strongly dependent on the pH of the solutions as well as divalent and monovalent salt concentrations of the reservoir solution. However, it is also strongly influenced by the curvature or radius of the tethering surface. The transition from a swollen to a collapsed layer as function of calcium concentration broadens and shifts to lower amounts of calcium ions as radius of NP increase (Fig. 1). The results show how the interplay between calcium binding and surface curvature governs the structural and functional 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.

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

2019 Spring National Meeting

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