Enzyme-Driven, Switchable Catalysis Based on Dynamic Self-Assembly of Peptides

A Photo-Switchable Peptide Fibril Esterase

Recent attempts to mimic enzyme catalysis using simple, short peptides have been successful in enhancing various reactions, but the on-demand, temporal or spatial regulation of such processes by external triggers remains a great challenge. Light irradiation is an ideal trigger for regulating molecular functionality, since it can be precisely manipulated in time and space, and because most reaction mediums do not react to light. We herein report the selection of a photo-switchable amphiphilic peptide catalyst from a small library of isomeric peptides, each containing an azobenzene-based light responsive group and a catalytic histidine residue. In its native fibrillar form, the selected peptide is efficiently and enantio-selectively active for ester hydrolysis, but after irradiation by UV light inducing trans-to-cis azobenzene isomerization, the fibrils disassemble to amorphous aggregates that are much less catalytically active. Significantly, this esterase-like activity can be manipulated multiple times, as the fibrillar peptide assembly is reversibly reduced and restored upon alternate irradiation by UV and visible light, respectively. We propose that this research may shine light on the origin of complex functions in early chemical evolution. Furthermore, it paves the way to regulate additional functions for peptide nanotechnology, such as replication, charge transfer, and delivery.

The Intrinsic Fluorescence of Peptide Self-Assemblies Across pH Levels

The regulation of solution pH on the structural and optical properties of peptide self-assemblies remains a critical yet unresolved issue in peptide research. This study investigates the heptapeptide Ac-IHIHIQI-NH2 and its intrinsic fluorescence across a range of pH levels, demonstrating that variations in pH lead to significant changes in the morphology of the self-assembled structures. While the position of the fluorescence emission remains constant-due to the stability provided by the hydrogen bonding network of the peptide backbone-the intensity of the fluorescence exhibits a direct correlation with the degree of self-assembly. This finding underscores a dynamic relationship between structural morphology and optical properties. Notably, the ability of the peptide to self-assemble under diverse pH conditions is a novel observation that contrasts with previously reported literature. By employing a computationally driven approach, complemented by rigorous experimental validation, this work establishes a new paradigm for studying complex interacting systems such as peptide self-assembly. Our findings enhance the understanding of how environmental factors influence peptide behavior and pave the way for the design of innovative peptide-based materials with tunable optical characteristics, with potential applications in bioluminescent probes and diagnostic tools for neurodegenerative diseases.

Advances in Injectable Hydrogels Based on Diverse Gelation Methods for Biomedical Imaging

The injectable hydrogels can deliver the loads directly to the predetermined sites and form reservoirs to increase the enrichment and retention of the loads in the target areas. The preparation and injection of injectable hydrogels involve the sol-gel transformation of hydrogels, which is affected by factors such as temperature, ions, enzymes, light, mechanics (self-healing property), and pH. However, tracing the injection, degradation, and drug release from hydrogels based on different ways of gelation is a major concern. To solve this problem, contrast agents are introduced into injectable hydrogels, enabling the hydrogels to be imaged under techniques such as fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, and radionuclide imaging. This review details methods for causing the gelation of imageable hydrogels; discusses the application of injectable hydrogels containing contrast agents in various imaging techniques, and finally explores the potential and challenges of imageable hydrogels based on different modes of gelation.

Enzyme-Mimetic, Cascade Catalysis-Based Triblock Polypeptide-Assembled Micelles for Enhanced Chemodynamic Therapy

Peptides and their conjugates are appealing as molecular scaffolds for constructing supramolecular biomaterials from the bottom up. Through strategic sequence design and interaction modulation, these peptides can self-assemble into diverse nanostructures that can, in turn, mimic the structural and catalytic functions of contemporary proteins. Here, inspired by the histidine brace active site identified in the metalloenzyme, we developed a triblock polypeptide with a hydrophobic polyleucine segment, a hydrophilic polylysine segment, and a terminal oligohistidine segment. This polypeptide demonstrates tunable and adaptive self-assembly morphologies. Moreover, copper ions can interact with the oligohistidine chelator and mediate the supramolecular assembly, generating metal-ligand centers for redox flow. The triblock polypeptide-based peptide micelles show Fenton-type activity with high substrate affinity when coassembled with copper ions. We have also engineered therapeutic micelles by coassembling two polypeptides, one integrated with copper ions and the other conjugated with glucose oxidase. This coassembled nanoplatform shows high in vitro and in vivo antitumor efficacy through a mechanism that combines triggered starvation and chemodynamic therapy. The versatility of this polypeptide sequence, which is compatible with various metal ions and functional ligands, paves the way for a broad spectrum of therapeutic and diagnostic applications.

One-Dimensional Implantable Sensors for Accurately Monitoring Physiological and Biochemical Signals

In recent years, one-dimensional (1D) implantable sensors have received considerable attention and rapid development in the biomedical field due to their unique structural characteristics and high integration capability. These sensors can be implanted into the human body with minimal invasiveness, facilitating real-time and accurate monitoring of various physiological and pathological parameters. This review examines the latest advancements in 1D implantable sensors, focusing on the material design of sensors, device integration, implantation methods, and the construction of the stable sensor-tissue interface. Furthermore, a comprehensive overview is provided regarding the applications and future research directions for 1D implantable sensors with an ultimate aim to promote their utilization in personalized healthcare and precision medicine.

Amino Acid-Derived Supramolecular Assembly and Soft Materials

Amino acids (AAs), serving as the primary monomer of peptides and proteins, are widely present in nature. Benefiting from their inherent advantages, such as chemical diversity, low cost, ease of modification, chirality, biosafety, and bio-absorbability, AAs have been extensively exploited to create self-assembled nanostructures and supramolecular soft materials. In this review article, we systematically describe the recent progress regarding amino acid-derived assembly and functional soft materials. A brief background and several classified assemblies of AAs and their derivatives (chemically modified AAs) are summarized. The key non-covalent interactions to drive the assembly of AAs are emphasized based on the reported systems of self-assembled and co-assembled AAs. We discuss the molecular design of AAs and the general rules behind the hierarchical nanostructures. The resulting soft materials with interesting properties and potential applications are demonstrated. The conclusion and remarks on AA-based supramolecular assemblies are also presented from the viewpoint of chemistry, materials, and bio-applications.

Computation-Driven Rational Design of Self-Assembled Short Peptides for Catalytic Hydrogen Production

Self-assembling peptides represent a captivating area of study in nanotechnology and biomaterials. This interest is largely driven by their unique properties and the vast application potential across various fields such as catalytic functions. However, design complexities, including high-dimensional sequence space and structural diversity, pose significant challenges in the study of such systems. In this work, we explored the possibility of self-assembled peptides to catalyze the hydrolysis of hydrosilane for hydrogen production using ab initio calculations and carried out wet-lab experiments to confirm the feasibility of these catalytic reactions under ambient conditions. Further, we delved into the nuanced interplay between sequence, structural conformation, and catalytic activity by combining modeling with experimental techniques such as transmission electron microscopy and nuclear magnetic resonance and proposed a dual mode of the microstructure of the catalytic center. Our results reveal that although research in this area is still at an early stage, the development of self-assembled peptide catalysts for hydrogen production has the potential to provide a more sustainable and efficient alternative to conventional hydrogen production methods. In addition, this work also demonstrates that a computation-driven rational design supplemented by experimental validation is an effective protocol for conducting research on functional self-assembled peptides.

Supramolecular Mimotope Peptide Nanofibers Promote Antibody-Ligand Polyvalent and Instantaneous Recognition for Biopharmaceutical Analysis

Peptide-based supramolecules exhibit great potential in various fields due to their improved target recognition ability and versatile functions. However, they still suffer from numerous challenges for the biopharmaceutical analysis, including poor self-assembly ability, undesirable ligand-antibody binding rates, and formidable target binding barriers caused by ligand crowding. To tackle these issues, a "polyvalent recognition" strategy employing the CD20 mimotope peptide derivative NBD-FFVLR-GS-WPRWLEN (acting on the CDR domains of rituximab) was proposed to develop supramolecular nanofibers for target antibody recognition. These nanofibers exhibited rapid self-assembly within only 1 min and robust stability. Their binding affinity (179 nM) for rituximab surpassed that of the monomeric peptide (7 μM) by over 38-fold, highlighting that high ligand density and potential polyvalent recognition can efficiently overcome the target binding barriers of traditional supramolecules. Moreover, these nanofibers exhibited an amazing "instantaneous capture" rate (within 15 s), a high recovery (93 ± 3%), and good specificity for the target antibody. High-efficiency enrichment of rituximab was achieved from cell culture medium with good recovery and reproducibility. Intriguingly, these peptide nanofibers combined with bottom-up proteomics were successful in tracking the deamidation of asparagine 55 (from 10 to 16%) on the rituximab heavy chain after 21 day incubation in human serum. In summary, this study may open up an avenue for the development of versatile mimotope peptide supramolecules for biorecognition and bioanalysis of biopharmaceuticals.