Designable and dynamic single-walled stiff nanotubes assembled from sequence-defined peptoids

Abstract

Despite recent advances in the assembly of organic nanotubes, conferral of sequence-defined engineering and dynamic response characteristics to the tubules remains a challenge. Here we report a new family of highly designable and dynamic nanotubes assembled from sequence-defined peptoids through a unique “rolling-up and closure of nanosheet” mechanism. During the assembly process, amorphous spherical particles of amphiphilic peptoid oligomers crystallize to form well-defined nanosheets before folding to form single-walled nanotubes. These nanotubes undergo a pH-triggered, reversible contraction–expansion motion. By varying the number of hydrophobic residues of peptoids, we demonstrate tuning of nanotube wall thickness, diameter, and mechanical properties. Atomic force microscopy-based mechanical measurements show peptoid nanotubes are highly stiff (Young’s Modulus ~13–17 GPa). We further demonstrate the precise incorporation of functional groups within nanotubes and their applications in water decontamination and cellular adhesion and uptake. These nanotubes provide a robust platform for developing biomimetic materials tailored to specific applications.

Solid‐phase synthesis of three‐armed star‐shaped peptoids and their hierarchical self‐assembly

“…The first broad q peak ( d = 3.1 nm) corresponded to the tube wall thickness. The peak at 1.67 nm assigned to the distance between two peptoid backbones in the direction of Nbpm groups facing each other . The strong peak at 4.6 Å was attributed to the distance among the aligned peptoid chains .…”

“…Morphology diversity plays crucial roles in the fundamental research and applications (e.g., multi‐drug delivery systems) of functional materials based on TASS polymer assemblies . In our previous study, linear diblock amphiphilic peptoid with one hydrophobic segment of six nonpolar groups and one hydrophilic segment of six polar Nce groups self‐assembled into highly stable and self‐repairable bilayer‐like nanomembranes and highly stiff and dynamic nanotubes . One effective strategy to demonstrate the self‐assembly of TASS peptoids is to select those similar to previously‐reported linear peptoids for self‐assembly, thus Pep‐5 , Pep‐6 , and Pep‐7 were used as representative TASS peptoids for aqueous self‐assembly (Figure ), in which the 5.0 mM peptoid clear solution obtained by dissolving lyophilized peptoid powders in the mixture of H 2 O and CH 3 CN (v/v = 1:1) was slowly evaporated at 4 °C for crystallization (See details in the Materials and Methods).…”

“…The hierarchical self‐assembly of TASS peptoids was performed using a slow evaporation‐induced crystallization process as previously reported, in which the lyophilized and HPLC‐grade TASS peptoids powders were dissolved in H 2 O/CH 3 CN (v/v = 1:1) mixture to obtain 5.0 mM clear solution, this clear solution was then slowly evaporated at 4 °C for the hierarchical self‐assembly. The detailed self‐assembly protocols of each TASS peptoids were described in Supporting Information.…”

“…Peptoids possess the combined superiorities of synthetic polymers and biopolymers, such as cheaply and easily programmed synthesis, narrow polydispersity index of molecular weight, and large side‐chain diversity. Besides, peptoids exhibit high stability and biocompatibility, and offer unique advantages for hierarchical self‐assembly of biomimetic nanomaterials due to the lack of backbone hydrogen bond donors . Therefore, the design of sequence‐defined peptoids that self‐assemble into biomimetic materials with hierarchical structures has recently received increasing attention.…”

“…Therefore, the design of sequence‐defined peptoids that self‐assemble into biomimetic materials with hierarchical structures has recently received increasing attention. For example, linear and cyclic peptoids have been recently designed and used as building blocks to synthesize nanotubes, nanosheets, nanomembranes, and superhelices . Recently, to enrich the topological structure of peptoids, Peschko et al .…”