Aggregation behavior of nanoparticles: Revisiting the phase diagram of colloids

Abstract

Surface functionalization of metal nanoparticles (NPs), e.g., using peptides and proteins, has recently attracted a considerable attention in the field of design of therapeutics and diagnostics. The possibility of diverse functionalization allows them to selectively interact with proteins, while the metal core ensures solubility, making them tunable therapeutic agents against diseases due to mis-folding or aggregation. On the other hand, their action is limited by possible self-aggregation, which could be, however, prevented based on the full understanding of their phase diagram as a function of the environmental variables (temperature, ionic strength of the solution, concentration) and intrinsic characteristics (size, charge, amount, and type of functional groups). A common modeling strategy to study the phase behavior is to represent the NPs as spheres interacting via effective potentials implicitly accounting for the solvation effects. Their size put the NPs into the class of colloids, albeit with particularly complex interactions including both attractive and repulsive features, and a consequently complex phase diagram. In this work, we review the studies exploring the phases of these systems starting from those with only attractive or repulsive interactions, displaying a simpler disperse-clustered-aggregated transitions. The phase diagram is here interpreted focusing on the universal aspects, i.e., those dependent on the general feature of the potentials, and available data are organized in a parametric phase diagram. We then consider the potentials with competing attractive short range well and average-long-range repulsive tail, better representing the NPs. Through the proper combination of the attractive only and repulsive only potentials, we are able to interpret the appearance of novel phases, characterized by aggregates with different structural characteristics. We identify the essential parameters that stabilize the disperse phase potentially useful to optimize NP therapeutic activity and indicate how to tune the phase behavior by changing environmental conditions or the NP chemical–physical properties.

Design of Liquid Formulation Based on F127-Loaded Natural Dimeric Flavonoids as a New Perspective Treatment for Leishmaniasis

“…Considering the F127 copolymer concentration was set above the CMC for both formulations, micelles may become asymmetric, and eventually various aggregates may be formed. Such micellar aggregates may have the form of spherical objects, or they may be elongated stiff rods, less flexible worm-like, or more complex structures, such as branched worm-like [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. The larger aggregates are interconnected by branches to form stable aggregates with even larger sizes, as shown in Figure 3 D. Adhesion force mapping was determined for F127 and LF-B500.…”

“…branched worm-like [35][36][37][38][39][40][41]. The larger aggregates are interconnected by branches to form stable aggregates with even larger sizes, as shown in Figure 3D.…”

Antibacterial Activity, Cell Wall Damage, and Cytotoxicity of Zinc Oxide Nanospheres, Nanorods, and Nanoflowers

“…However, taking into account that in this study, the spherical shape has a lower specific surface area compared to other morphologies, probably because of the higher aggregation tendency of spherical particles. 46 Therefore, it can be argued that the effect of morphology is more dominant than the size of nanoparticles. Consequently, the rod-shaped nanoparticles synthesized in this research exhibit a higher specific surface area than the synthesized spherical nanoparticles.…”

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“…In 2022 Bini et al 748 also reviewed the phase behavior of colloidal systems in a rather detailed way. They indicate that a common modeling strategy to study the phase behavior is to represent nanoparticles as spheres interacting via effective potentials implicitly accounting for solvation effects.…”