Size control and compartmentalization in self-assembled nano-structures of a multisegment amphiphile

Abstract

A ''multisegment amphiphile'' has been synthesized by covalently connecting two well known building blocks, a gelator and a micelle forming surfactant. Self-assembly results in the formation of compartmentalized nano-object displaying properties inherited from both parents.Amphiphiles continue to attract widespread attention in science and technology, not only because of their fascinating self-assembly properties, but also because their numerous, diverse applications in e.g. detergent formulations, catalysis, and drug delivery. Despite their large chemical diversity, amphiphiles share a common structure consisting of a hydrophilic and a hydrophobic segment, giving rise to a limited range of morphologies like micelles, vesicles, bilayers, and the corresponding inverted phases. 1 More recently, other building blocks such as small molecule gelators and peptides have been used to construct novel self-assembled architectures like ribbons, helices and tubes 2 with regular, well-defined structural features at molecular length scales. 3 Nevertheless, small molecule based self-assembled structures cannot yet compete with the sophisticated architectures found in natural systems, especially with regard to the levels of compartmentalization, size control, and hierarchical structure formation. 4 Currently, such multicompartment structures of defined size and 3-50 nm structural features can most easily be fabricated by controlled phase separation of multiple covalently connected segments in block copolymers, giving rise to a variety of multicompartment assemblies 5 and hierarchically structured materials. 6 Only few examples have been reported of self-assembled structures from small molecules with a block structure. 7 The challenge remains to develop self-assembling systems based on small molecules that allow size control, hierarchical structure formation and compartmentalization at (sub)-molecular length scales. Previously we and others showed that the orthogonal self-assembly of certain hydrogelators and surfactants is a valid strategy towards new nanoarchitectures, including selfassembled interpenetrating networks and various organizations of vesicles or micelles with fibrous networks (Scheme 1a). 8,9 We anticipated that the covalent connection of two orthogonally self-assembling molecular building blocks would give rise to microphase separation phenomena at the molecular length scale.Here we present a first example of such a ''multisegment amphiphile'', as the small molecule counterpart of block copolymers (Scheme 1b). We found that this multisegment amphiphile self-assembles into well-defined aggregates with compartments and structural features at molecular length scales inherited from its parent compounds. Our results suggest that this behavior results from strong spatial constraints on a phase separating system at the molecular scale.A first requirement for a multisegment amphiphile is that the self-assembly of each segment is driven by incompatible interactions. In this study we have combined a low-molecularweight ...

Cell death versus cell survival instructed by supramolecular cohesion of nanostructures

“…51, 52 Solutions of molecules 1 and 2 , ranging from 1 μM to 1000 μM in PBS, were prepared from stock solutions, and Nile Red in ethanol was diluted 200-fold into solutions to a final concentration of 250 nM. Using a NanoLogHJ spectrofluorometer, the samples were excited at 550 nm and the spectra were collected from 580 – 750 nm.…”

Programmed Morphological Transitions of Multisegment Assemblies by Molecular Chaperone Analogues

“…As a model system, we use a previously described multisegment amphiphile that consists of two covalently linked but orthogonally self-assembling building blocks, and which forms architectures characterized by each individual segment. [9] Through the addition of a chaperone analogue we can selectively switch off the self-assembly of each of these segments individually, resulting in architectures of the other segment. Interestingly, not only the morphologies of the other segment are retained, but also its dynamics of self-assembly.…”

“…[11a] We have previously shown that MA 3 in water assembles into architectures that display properties of both parental segments. [9] The gelator segment forces these molecules to stack into fibrils because of intermolecular hydrogen bonding and these fibrils assemble into tapes caused by the hydrophobic interactions between the surfactant segments (Figure 1 b). These tapes form an entangled network in the solvent leading to turbid gels above a critical gelation concentration (cgc) of 5.0 mm.…”

Programmed Morphological Transitions of Multisegment Assemblies by Molecular Chaperone Analogues

“…The multisegment amphiphile (MA 3 ) is constructed of a gelator10 segment reminiscent of gelator 1 and a surfactant segment reminiscent of EO 4 C 8 (surfactant 2 ), which assemble orthogonally (Figure 1 a). 11a We have previously shown that MA 3 in water assembles into architectures that display properties of both parental segments 9. The gelator segment forces these molecules to stack into fibrils because of intermolecular hydrogen bonding and these fibrils assemble into tapes caused by the hydrophobic interactions between the surfactant segments (Figure 1 b).…”

“…Herein we demonstrate that morphological transitions can easily be programmed by separately addressing the complex aggregation behavior of a segmented self‐assembling molecule, using small molecule chaperone analogues, that is, small molecules that selectively switch off self‐assembly of another molecule through selective association. As a model system, we use a previously described multisegment amphiphile that consists of two covalently linked but orthogonally self‐assembling building blocks, and which forms architectures characterized by each individual segment 9. Through the addition of a chaperone analogue we can selectively switch off the self‐assembly of each of these segments individually, resulting in architectures of the other segment.…”