Covalently triggered self-assembly of peptide-based nanodrugs for cancer theranostics

Covalently triggered peptide self-assembly is achieved through sequential integration of spontaneous covalent reaction and noncovalent interactions, thus both enhancing the physiological stability and extending unexpected functionality of the resulting peptide-based assemblies, different from popular supramolecular peptide self-assembly merely associated with noncovalent interactions. This review summarizes the recent progress on the development of covalently triggered peptide self-assembly for cancer theranostics. Especially, we propose the fundamental design principle of covalently triggered peptide self-assembly for constructing a variety of peptide-based assemblies including nanoparticles, nanofibers, hollow nanospheres, and other nanoarchitectures. Subsequently, the discussion is anchored in an overview of representative covalently assembled peptide-based nanodrugs for the cancer theranostics. Finally, the challenges and perspectives on the clinical potential of the covalently assembled peptide-based nanodrugs are highlighted. This review will provide new insights into construction of peptide-based nanodrugs through combination of covalent reaction and noncovalent self-assembly and prompt their clinical applications in cancer diagnosis and therapeutics.

Structural and photoactive properties of self-assembled peptide-based nanostructures and their optical bioapplication in food analysis

BACKGROUND

Food processing plays an important role in the modern industry because food quality and security directly affect human health, life safety, and social and economic development. Accurate, efficient, and sensitive detection technology is the basis for ensuring food quality and security. Optosensor-based technology with the advantage of fast and visual real-time detection can be used to detect pesticides, metal ions, antibiotics, and nutrients in food. As excellent optical centres, self-assembled peptide-based nanostructures possess attractive advantages, such as simple preparation methods, controllable morphology, tunable functionality, and inherent biocompatibility.

AIM OF REVIEW

Self-assembled peptide nanostructures with good fabrication yield, stability, dispersity in a complex sample matrix, biocompatibility, and environmental friendliness are ideal development goals in the future. Owing to its flexible and unique optical properties, some short peptide self-assemblies can possibly be used to achieve the purpose of rapid and sensitive detection of composition in food, agriculture, and the environment, expanding the understanding and application of peptide-based optics in analytical chemistry.

KEY SCIENTIFIC CONCEPT OF REVIEW

The self-assembly process of peptides is driven by noncovalent interactions, including hydrogen bonding, electrostatic interactions, hydrophobic interactions, and π-π stacking, which are the key factors for obtaining stable self-assembled peptide nanostructures with peptides serving as assembly units. Controllable morphology of self-assembled peptide nanostructures can be achieved through adjustment in the type, concentration, and pH of organic solvents and peptides. The highly ordered nanostructures formed by the self-assembly of peptides have been proven to be novel biological structures and can be used for the construction of optosensing platforms in biological or other systems. Optosensing platforms make use of signal changes, including optical signals and electrical signals caused by specific reactions between analytes and active substances, to determine the content or concentration of an analyte.

Tuning Rheological Behaviors of Supramolecular Aqueous Gels via Charge Transfer Interactions

Rheological properties are critical for determining real applications of supramolecular gels in various fields. Correspondingly, the modulation of gel rheology will be very important for meeting real requirements. In this aspect, a few strategies were applied to tune the rheological behaviors of supramolecular gels, but some specific interactions like charge transfer (CT) interactions were less explored at the molecular level. Herein, we report a pyrene-containing derivative of diphenylalanine as a donor gelator and naphthalenediimide or 3,5-dinitrobenzene as matching acceptor molecules. It was found that the viscoelastic properties and strength of the original gel could be tuned through addition of different acceptor molecules to the original gel with changing the ratios of the selected acceptor molecules. As a result, storage modulus was continuously adjusted over a wide range from 190,000 to 50,000 Pa by CT interactions. Furthermore, the mechanism of the CT-induced change in rheological properties was understood and clarified through relevant techniques (e.g., UV-Vis, fluorescence, and FT-IR spectroscopy and TEM). The findings in this work would provide a novel strategy to modulate the rheological properties of supramolecular gels for adaption to broader fields of real applications.

Trace Water as Prominent Factor to Induce Peptide Self-Assembly: Dynamic Evolution and Governing Interactions in Ionic Liquids

The interaction between water and biomolecules including peptides is of critical importance for forming high-level architectures and triggering life's functions. However, the bulk aqueous environment has limitations in detecting the kinetics and mechanisms of peptide self-assembly, especially relating to interactions of trace water. With ionic liquids (ILs) as a nonconventional medium, herein, it is discovered that trace amounts of water play a decisive role in triggering self-assembly of a biologically derived dipeptide. ILs provide a suitable nonaqueous environment, enabling us to mediate water content and follow the dynamic evolution of peptide self-assembly. The trace water is found to be involved in the assembly process of dipeptide, especially leading to the formation of stable noncovalent dipeptide oligomers in the early stage of nucleation, as evident by both experimental studies and theoretical simulations. The thermodynamics of the growth process is mainly governed by a synergistic effect of hydrophobic interaction and hydrogen bonds. Each step of assembly presents a different trend in thermodynamic energy. The dynamic evolution of assembly process can be efficiently mediated by changing trace water content. The decisive role of trace water in triggering and mediating self-assembly of biomolecules provides a new perspective in understanding supramolecular chemistry and molecular self-organization in biology.

Solvent-Induced Molecular Folding and Self-Assembled Nanostructures of Tyrosine and Tryptophan Analogues in Aqueous Solution: Fascinating Morphology of High Order

Hydrophobic derivatives of tyrosine and tryptophan, viz. octyl and dodecyl esters of tyrosine and octyl ester of tryptophan, are synthesized, and the interfacial and bulk properties in aqueous media are investigated as models for the membrane proteins. Molecular modeling by the density functional theory method is carried out to understand the molecular conformation and geometry for the purpose of determining the packing parameters. Water-induced molecular folding of the esters of both tyrosine and tryptophan, as observed using rotating frame nuclear Overhauser effect spectroscopy, indicates that the segregation of the hydrophobic and hydrophilic blocks in water is the key to the development of fascinating interfacial property displayed by the aromatic amino acid esters. The unusually high-order morphology of the aggregates, as observed using high-resolution transmission electron microscopy, is highly uncommon for single-chain amphiphiles and points to the fact that the self-assembly behavior of the present systems resembles that of block copolymers. The study of the growth of mesosized hollow aggregates with internal bilayer structures from tyrosine and tryptophan-based model systems would add to the understanding of biochemistry and biotechnology relevant to the cell membrane. The potential of biocompatible nanostructured motifs as the drug carriers is discussed. The highly functional role played by the aromatic amino acids at the membrane-water interface will be considered with the present amphiphilic models for future perspective.

Multiscale simulations for understanding the evolution and mechanism of hierarchical peptide self-assembly

Multiscale molecular simulations that combine and systematically link several hierarchies can provide insights into the evolution and dynamics of hierarchical peptide self-assembly from the molecular level to the mesoscale.