Light induced assembly and self-sorting of silica microparticles

Abstract

To tailor the properties of colloidal materials, precise control over the self-assembly of their constituents is a prerequisite. Here, we govern the assembly of silica particles by functionalization with supramolecular moieties which interact with each other via directional and reversible hydrogen bonding. Through a generally applicable synthesis protocol, two different types of self-complementary hydrogen bonding moieties, BTA-and UPy-derivatives, are anchored to silica particles. Their selfassembly is initiated by the UV-induced removal of a photolabile protecting group, allowing the formation of hydrogen bonds between tethered molecules. The light-induced assembly of BTA-and UPy-decorated colloids in single-component dispersions and colloidal self-sorting in mixed dispersions is studied. Furthermore, we demonstrate that UPy-colloids can dissasemble upon addition of traces of a competitive binder (NaPy). This work provides further insight into the utility of supramolecular handles to orchestrate the assembly of micron-sized colloids via non-oligonucleotide hydrogen-bonding units.The ability to control molecular self-assembly via non-covalent interactions is an emerging bottom-up strategy to create complex metamaterials. In turn, well-defined molecular recognition can be used as a powerful tool to direct the assembly of micron-sized 1-3 colloids or even macroscopic objects 4 and create larger aggregated structures with emergent optical 5-7 , mechanical 8 or catalytic properties 9,10 . Molecular control over the assembly of micron-sized particles can be realized through particle surface-grafting of molecules exhibiting dipole-dipole 11,12 , metal coordination 13 , hydrophobic forces 14,15 and/or hydrogen bonding (H-bonding) [16][17][18] . Ideally, the tethered motifs should be easy to synthesize, responsive, externally addressable and provide directional, dynamic and specific bonding within the assemblies. Moreover, to facilitate colloidal assembly, a precise control between the interplay of non-specific surface forces (attractive and/or repulsive) is crucial 19 .A popular strategy in the field is the functionalization of colloids with complementary DNA strands 20,21 . Great advances in insight and structural complexity have been achieved in the last 20 years, enabling the assembly of colloids into both disordered and exotic ordered states 22,23 , in a reversible 22,24,25 or irreversible 26 manner and at the nano-27,28 and mesoscale 25,29 . Notwithstanding, DNA-technology has its limitations, such as high cost and restricted environmental conditions 27,30 because the strands only assemble in water at sufficiently high ionic strengths and at low temperature, precluding material synthesis and processing from organic solvents. Furthermore, up to now, only temperature has been used as external trigger of assembly, while recent advances towards light sensitive DNA-strands can be utilized in future to develop dual-responsive systems sensitive to both temperature and light 31 . A promising alternative strategy exploits...

Mimicking Adhesion in Minimal Synthetic Cells

“…Self-sorting is defined by the ability to distinguish between self and nonself and relies on orthogonal cell-cell interactions. [68,76,78] 1) Indiscriminate self-assembly: Weak and unspecific interactions, such as electrostatic or hydrophilic/hydrophobic interactions, lead to indiscriminate assemblies in which all types of colloids assemble into one aggregate. [76,77] The concept of self-sorting is therefore of interest for bottom-up synthetic biology to coassemble multiple prototissues with higher complexity.…”

“…[76] Different forms of self-sorting are possible depending on the type of interactions between cell mimetics. [78] For this, two different types of self-complementary interaction partners were each tethered onto particles and the self-sorting was triggered within this two component mixture by UV-induced removal of protecting groups. For example, the self-assembly based on hydrophilic-hydrophobic phase transition of peptides or polymers enables all particles in the mixture to self-assemble into indiscriminate aggregates.…”

“…For example, the self-assembly based on hydrophilic-hydrophobic phase transition of peptides or polymers enables all particles in the mixture to self-assemble into indiscriminate aggregates. [78] 3) Social sorting: Two orthogonal heterophilic interaction pairs allow for social self-sorting leading to the formation of Lipids with photocleavable PEG chains sterically hinder the interaction between the minimal fusion peptides E and K. Upon light illumination, the PEG is cleaved leading to the interaction between the two peptides and consequently the adhesion and fusion of the vesicles. For example, two populations of azobenzene-functionalized gold nanoparticles were functionalized with differently substituted azobenzene nanoparticles such that each azobenzene preferentially interacted with itself upon UV or blue light illumination.…”

Electrostatic loading and photoredox-based release of molecular cargo from oligoviologen-crosslinked microparticles

“…Photo-stimulated microparticles are thus well suited as an attractive option that blends such characteristics for use in drug-release 12,13 and self-healing 14 applications, among others.…”

Independent Blue and Red Light Triggered Narcissistic Self‐Sorting Self‐Assembly of Colloidal Particles

“…Decorating colloids with DNA, proteins, and supramolecular interaction partners allows to program their self‐assembly and modify assemblies in response to external triggers such as temperature, pH, and light . Among these stimuli, photoresponsive assemblies are especially attractive since light provides noninvasive, tunable, and specific control with high spatiotemporal resolution …”