Formation of Polymeric Particles by Direct Polymerization on the Surface of a Supramolecular Template

Formation of polymeric materials on the surface of supramolecular assemblies is rather challenging because of the often weak noncovalent interactions between the self-assembled template and the monomers before polymerization. We herein show that the introduction of a supramolecular anion recognition motif, the guanidiniocarbonyl pyrrole cation (GCP), into a short Fmoc-dipeptide 1 leads to self-assembled spherical nanoparticles in aqueous solution. Negatively charged diacetylene monomers can be attached onto the surface of these nanoparticles, which, after UV polymerization, leads to the formation of a polymer shell around the self-assembled template. The hybrid supramolecular and polymeric nanoparticles demonstrate intriguing thermal hysteresis phenomena. The template nanoparticles could be disassembled upon treatment with organic base, which cleaved the Fmoc moiety on 1. This strategy thus showed that a supramolecular anion recognition motif allows the post-assembly formation of polymeric nanomaterials from anionic monomers around a cationic self-assembled template.

Formation of Twisted β-Sheet Tapes from a Self-Complementary Peptide Based on Novel Pillararene-GCP Host-Guest Interaction with Gene Transfection Properties

Small peptides capable of assembling into well-defined nanostructures have attracted extensive attention due to their interesting applications as biomaterials. This work reports the first example of a pillararene functionalized with a guanidiniocarbonyl pyrrole (GCP)-conjugated short peptide segment. The obtained amphiphilic peptide 1 spontaneously self-assembles into a supramolecular β-sheet in aqueous solution based on host-guest interaction between pillararene and GCP unit as well as hydrogen-bonding between the peptide strands. Interestingly, peptide 1 at low concentration shows transitions from small particles to "pearl necklace" assemblies, and finally to branched fibers in a time-dependent process. At higher concentration, it directly assembles into twisted β-sheet tapes. Notably, without pillararene moiety, the control peptide A forms α-helix structure with morphology changing from particles to bamboo-like assemblies depending on concentration, indicating a significant role of the pillararene-GCP host-guest interaction for the secondary structure formation. Moreover, peptide 1 can serve as an efficient gene transfection vector.

A Photoinduced Reversible Phase Transition in a Dipeptide Supramolecular Assembly

Tunable supramolecular assembly has found various applications in biomedicine, molecular catalysis, optoelectronics, and nanofabrication. Unlike traditional covalent conjugation, non-covalent introduction of a photoswitchable moiety enables reversible photomodulation of non-photosensitive dipeptide supramolecular assembly. Under light illumination, a long-lived photoacid generator releases a proton and mediates the dissociation of dipeptide-based organogel, thereby resulting in sol formation. Under darkness, the photoswitchable moiety entraps a proton, resulting in gel regeneration. Furthermore, accompanying the isothermal recycled gel-sol transition in a spatially controlled manner, renewable patterns are spontaneously fabricated. This new concept of light-controlled phase transition of amino acid-based supramolecular assemblies will open up the possibility of wide applications.

Transformation of Dipeptide-Based Organogels into Chiral Crystals by Cryogenic Treatment

Controlled molecular assembly is an important approach for the synthesis of single-component materials with diverse functions. Unlike traditional heat treatment or solvent modulation, cryogenic treatment at 77 K enabled the tunable transition of a self-assembled diphenylalanine organogel into a hexagonal crystal. Under these conditions, the assembled molecules undergo an internal rearrangement in the solid state to form a well-defined chiral crystal structure. Moreover, these assemblies exhibit enhanced emission. This strategy for the synthesis of single-component supramolecular assemblies can create new functions by manipulating phase transitions.