Disassembling peptide-based fibres by switching the hydrophobic-hydrophilic balance

The role of critical micellization concentration in efficacy and toxicity of supramolecular polymers

The inception and development of supramolecular chemistry have provided a vast library of supramolecular structures and materials for improved practice of medicine. In the context of therapeutic delivery, while supramolecular nanostructures offer a wide variety of morphologies as drug carriers for optimized targeting and controlled release, concerns are often raised as to how their morphological stability and structural integrity impact their in vivo performance. After intravenous (i.v.) administration, the intrinsic reversible and dynamic feature of supramolecular assemblies may lead them to dissociate upon plasma dilution to a concentration below their critical micellization concentration (CMC). As such, CMC represents an important characteristic for supramolecular biomaterials design, but its pharmaceutical role remains elusive. Here, we report the design of a series of self-assembling prodrugs (SAPDs) that spontaneously associate in aqueous solution into supramolecular polymers (SPs) with varying CMCs. Two hydrophobic camptothecin (CPT) molecules were conjugated onto oligoethylene-glycol (OEG)-decorated segments with various OEG repeat numbers (2, 4, 6, 8). Our studies show that the lower the CMC, the lower the maximum tolerated dose (MTD) in rodents. When administrated at the same dosage of 10 mg/kg (CPT equivalent), SAPD 1, the one with the lowest CMC, shows the best efficacy in tumor suppression. These observations can be explained by the circulation and dissociation of SAPD SPs and the difference in molecular and supramolecular distribution between excretion and organ uptake. We believe these findings offer important insight into the role of supramolecular stability in determining their therapeutic index and in vivo efficacy.

Supramolecular assembly of functional peptide–polymer conjugates

The following review gives an overview about synthetic peptide–polymer conjugates as macromolecular building blocks and their self-assembly into a variety of supramolecular architectures, from supramolecular polymer chains, to anisotropic 1D arrays, 2D layers, and more complex 3D networks.

Synergistic antitumor activity of a self-assembling camptothecin and capecitabine hybrid prodrug for improved efficacy

The direct use of anticancer drugs to create their own nanostructures is an emerging concept in the field of drug delivery to obtain nanomedicines of high drug loading and high reproducibility, and the combination use of two or more drugs has been a proven clinical strategy to enhance therapeutic outcomes. We report here the synthesis, assembly and cytotoxicity evaluation of self-assembling hybrid prodrugs containing both camptothecin (CPT) and a capecitabine (Cap) analogue. CPT and Cap molecules were conjugated onto a short β-sheet-forming peptide (Sup35) to yield three different self-assembling prodrugs (dCPT-Sup35, CPT-Cap-Sup35 and dCap-Sup35). We found that the chemical structure of conjugated drugs could strongly influence their assembled morphology as well as their structural stability in aqueous solution. With a decrease in number of CPT units, the resulting nanostructures exhibited a morphological transformation from nanofibers (dCPT-Sup35) to filaments (CPT-Cap-Sup35) then to spherical particles (dCap-Sup35). Notably, the hybrid CPT-Cap prodrug showed a synergistic effect and significantly enhanced potency against three esophageal adenocarcinoma cell lines compared with the two homo-prodrugs (dCPT-Sup35 and dCap-Sup35) as well as free parent drugs (CPT, 5-Fu and CPT/5-FU mixture (1:1)). We believe this work represents a conceptual advancement in integrating two structurally distinct drugs of different action mechanisms into a single self-assembling hybrid prodrug to construct self-deliverable nanomedicines for more effective combination chemotherapy.

Tightening up the structure, lighting up the pathway: Application of molecular constraints and light to manipulate protein folding, self-assembly and function

Chemical cross-linking provides an effective avenue to reduce the conformational entropy of polypeptide chains and hence has become a popular method to induce or force structural formation in peptides and proteins. Recently, other types of molecular constraints, especially photoresponsive linkers and functional groups, have also found increased use in a wide variety of applications. Herein, we provide a concise review of using various forms of molecular strategies to constrain proteins, thereby stabilizing their native states, gaining insight into their folding mechanisms, and/or providing a handle to trigger a conformational process of interest with light. The applications discussed here cover a wide range of topics, ranging from delineating the details of the protein folding energy landscape to controlling protein assembly and function.

Self-assembling amphiphilic peptides

The self-assembly of several classes of amphiphilic peptides is reviewed, and selected applications are discussed. We discuss recent work on the self-assembly of lipopeptides, surfactant-like peptides and amyloid peptides derived from the amyloid-β peptide. The influence of environmental variables such as pH and temperature on aggregate nanostructure is discussed. Enzyme-induced remodelling due to peptide cleavage and nanostructure control through photocleavage or photo-cross-linking are also considered. Lastly, selected applications of amphiphilic peptides in biomedicine and materials science are outlined.

Self-assembly of peptides to nanostructures

The formation of well-ordered nanostructures through self-assembly of diverse organic and inorganic building blocks has drawn much attention owing to their potential applications in biology and chemistry. Among all organic building blocks, peptides are one of the most promising platforms due to their biocompatibility, chemical diversity, and resemblance to proteins. Inspired by the protein assembly in biological systems, various self-assembled peptide structures have been constructed using several amino acids and sequences. This review focuses on this emerging area, the recent advances in peptide self-assembly, and formation of different nanostructures, such as tubular structures, fibers, vesicles, and spherical and rod-coil structures. While different peptide nanostructures have been discovered, potential applications are explored in drug delivery, tissue engineering, wound healing, and surfactants.

PEG-peptide conjugates

The remarkable diversity of the self-assembly behavior of PEG-peptides is reviewed, including self-assemblies formed by PEG-peptides with β-sheet and α-helical (coiled-coil) peptide sequences. The modes of self-assembly in solution and in the solid state are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized.

Amide I Band and Photoinduced Disassembly of a Peptide Hydrogel

Peptide hydrogels are promising candidates for a wide range of medical and biotechnological applications. To further expand the potential utility of peptide hydrogels, herein we demonstrate a simple yet effective strategy to render peptide hydrogels photodegradable, making controlled disassembly of the gel structure of interest feasible. In addition, we find that the high-frequency amide I' component (i.e., the peak at ~1685 cm-1) of the photodegradable peptide hydrogel studied shows an unusually large enhancement, in comparison to that of other peptide fibrils consisting of antiparallel β-sheets, making it a good model system for further study of the coupling-structure relationship.

Soft matter approaches to food structuring

We give an overview of the many opportunities that arise from approaching food structuring from the perspective of soft matter physics. This branch of physics employs concepts that build upon the seminal work of van der Waals, such as free volume, the mean field, and effective temperatures. All these concepts aid scientists in understanding and controlling the thermodynamics and (slow) dynamics of structured foods. We discuss the use of these concepts in four topics, which will also be addressed in a forthcoming Faraday Discussion on food structuring.

Bio-inspired supramolecular self-assembly towards soft nanomaterials

Supramolecular self-assembly has proven to be a reliable approach towards versatile nanomaterials based on multiple weak intermolecular forces. In this review, the development of bio-inspired supramolecular self-assembly into soft materials and their applications are summarized. Molecular systems used in bio-inspired "bottom-up self-assembly" involve small organic molecules, peptides or proteins, nucleic acids, and viruses. Self-assembled soft nanomaterials have been exploited in various applications such as inorganic nanomaterial synthesis, drug or gene delivery, tissue engineering, and so on.