Authors: Tangi Aubert | Kai Ma | Yunye Gong | Melik Z. Turker | Teresa Kao | Peter C. Doerschuk | Ulrich Wiesner
Source: Ghent University Academic Bibliography (Ghent University) (article, 2018-01-01)
Field: Materials Science — Materials Chemistry

Ultrasmall inorganic cages directed by surfactant micelles Functional silica nanoparticles have become highly relevant materials in the fields of biology and medicine. Ultrasmall fluorescent silica nanoparticles developed in our group (Cdots) have now reached phase 2 of clinical trials for cancer diagnostics. Nevertheless, modern nanomedicine techniques and their increasing complexity today are still in demand for more efficient and multifunctional tools for advanced applications such as theranostics. To this end, important developments have been made in order for these nanoparticles to achieve their full potential, including chemical modification of their matrix to improve their optical properties, and new synthetic strategies for multifunctional nanoparticles via a surface modification approach with various functional groups. In parallel, new alternative particle geometries have been investigated for targeted drug delivery applications.\nIn this contribution, we will review some of the recent progress made in our group that ultimately led to the discovery of highly symmetrical dodecahedral silica nanocages, or ‘silicages’ [1]. Ultrasmall (&lt; 10 nm) silica nanoparticles with tunable geometries can be obtained through their templating with surfactant micelles. The self-assembly of silica clusters on these micelles gives rise to unique and well defined structures. The dodecahedral cage structure in particular is of great fundamental importance. It is the simplest of a set of Voronoi polyhedra suggested to form the smallest structural units of multiple forms of mesoporous silica, yet such highly symmetrical silica cages had never been isolated before. In order to resolve the actual structure of these ultrasmall objects, single-particle 3D reconstruction from tens of thousands of cryo-electron microscopy images was performed using a custom-built ‘Hetero’ machine learning algorithm. We will finally show that cage formation is not limited to silica, but has been observed for other materials including metals and transition metal oxides.\nThe chemical and practical value of this polyhedral structure may prove immense. Given the versatility of silica surface chemistry one can readily conceive of cage derivatives of many kinds, which may exhibit unusual properties and be useful in applications ranging from catalysis to drug delivery. For example, given recent success in the clinical translation of ultrasmall fluorescent silica nanoparticles with similar particle sizes and surface properties to these cages, one can envisage a range of new diagnostic and therapeutic probes with drugs hidden inside the cages.\nReference:\n[1] K. Ma, Y. Gong, T. Aubert, M. Z. Turker, T. Kao, P. C. Doerschuk, U. Wiesner, Nature 2018, DOI: 10.1038/s41586-018-0221-0. Nanotechnology ; Mesoporous silica ; Nanomedicine ; Nanoparticle ; Dodecahedron ; Nanocages ; Materials science ; Micelle ; Particle (ecology) ; Drug delivery ; Mesoporous material ; Chemistry ; Crystallography ; Organic chemistry ; Aqueous solution Mesoporous Materials and Catalysis ; Diatoms and Algae Research ; Catalytic Processes in Materials Science