No abstract

The use of growth modifiers in natural, biological, and synthetic crystallization is a ubiquitous strategy for controlling growth and achieving desired physicochemical properties. For crystals that grow classically (i.e., monomer-by-monomer addition), theories of crystallization are well established and the field of growth modification is rather mature, although many questions remain regarding the molecular driving forces of modifier–crystal interactions. A new frontier in crystallization is the application of classical methods to tailor materials that grow nonclassically (i.e., growth by the addition of species more complex than monomers). A recent surge of interest and activity in this field has been driven by mounting evidence of both inorganic and organic materials that grow via nonclassical pathways. In these systems, the challenge of elucidating the mechanism(s) of crystallization is underscored by a diversity of growth units that far outnumber those available for classical routes. In this Perspective, we discuss growth modification in nonclassical crystallization, including examples in the literature, the challenges associated with elucidating the modes of modifier action, and to what degree classical theories can be applied to these complex problems as a means of establishing versatile blueprints for crystal engineering.

Advanced methods of identifying therapeutics for kidney stone disease have created a greater awareness of the potential impact of crystal modifiers in pathological crystallization. Many natural and synthetic species have the capacity to act as growth inhibitors; however, the challenge of bridging in-vitro and in-vivo evidence has proven to be difficult. Future effort to better integrate laboratory research, clinical trials and animal studies has the potential to broaden our understanding of crystal growth modification and its role in mitigating pathological crystallization.