Mimicking Mytilus edulis foot protein: A versatile strategy for robust biomedical coatings

Universal coatings with versatile surface adhesion, good mechanochemical robustness, and the capacity for secondary modification are of great scientific interest. However, incorporating these advantages into a system is still a great challenge. Here, we report a series of catechol-decorated polyallylamines (CPAs), denoted as pseudo-Mytilus edulis foot protein 5 (pseudo-Mefp-5), that mimic not only the catechol and amine groups but also the backbone of Mefp-5. CPAs can fabricate highly adhesive, robust, multifunctional polyCPA (PCPA) coatings based on synergetic catechol-polyamine chemistry as universal building blocks. Due to the interpenetrating entangled network architectures, these coatings exhibit high chemical robustness against harsh conditions (HCl, pH 1; NaOH, pH 14; H2O2, 30%), good mechanical robustness, and wear resistance. In addition, PCPA coatings provide abundant grafting sites, enabling the fabrication of various functional surfaces through secondary modification. Furthermore, the versatility, multifaceted robustness, and scalability of PCPA coatings indicate their great potential for surface engineering, especially for withstanding harsh conditions in multipurpose biomedical applications.

Bioactive Hydrogels Inspired by Laminin: An Emerging Biomaterial for Tissue Engineering Applications

Tissue or organ damage due to severe injuries or chronic diseases can adversely affect the quality of life. Current treatments rely on organ or tissue transplantation which has limitations including unavailability of donors, ethical issues, or immune rejection after transplantations. These limitations can be addressed by tissue regeneration which involves the development of bioactive scaffolds closely mimicking the extracellular matrix (ECM). One of the major components of ECM is the laminin protein which supports several tissues associated with important organs. In this direction, peptide-based hydrogels can effectively mimic the essential characteristics of laminin. While several reports have discussed the structure of laminin, the potential of laminin-derived peptide hydrogels as effective biomaterial for tissue engineering applications is yet to be discussed. In this context, the current review focuses on the structure of laminin and its role as an essential ECM protein. Further, the potential of short peptide hydrogels in mimicking the crucial properties of laminin is proposed. The review further highlights the significance of bioactive hydrogels inspired by laminin - in addressing numerous tissue engineering applications including angiogenesis, neural, skeletal muscle, liver, and adipose tissue regeneration along with a brief outlook on the future applications of these laminin-based hydrogels.

Conductive Peptide-Based MXene Hydrogel as a Piezoresistive Sensor

Wearable pressure sensors have become increasingly popular for personal healthcare and motion detection applications due to recent advances in materials science and functional nanomaterials. In this study, a novel composite hydrogel is presented as a sensitive piezoresistive sensor that can be utilized for various biomedical applications, such as wearable skin patches and integrated artificial skin that can measure pulse and blood pressure, as well as monitor sound as a self-powered microphone. The hydrogel is composed of self-assembled short peptides containing aromatic, positively- or negatively charged amino acids combined with 2D Ti3C2Tz MXene nanosheets. This material is low-cost, facile, reliable, and scalable for large areas while maintaining high sensitivity, a wide detection range, durability, oxidation stability, and biocompatibility. The bioinspired nanostructure, strong mechanical stability, and ease of functionalization make the assembled peptide-based composite MXene-hydrogel a promising and widely applicable material for use in bio-related wearable electronics.

Coupling Peptide-Based Encapsulation of Enzymes with Bacteria for Paraoxon Bioremediation

The catalytic efficiency of enzymes can be harnessed as an environmentally friendly solution for decontaminating various xenobiotics and toxins. However, for some xenobiotics, several enzymatic steps are needed to obtain nontoxic products. Another challenge is the low durability and stability of many native enzymes in their purified form. Herein, we coupled peptide-based encapsulation of bacterial phosphotriesterase with soil-originated bacteria, Arthrobacter sp. 4Hβ as an efficient system capable of biodegradation of paraoxon, a neurotoxin pesticide. Specifically, recombinantly expressed and purified methyl parathion hydrolase (MPH), with high hydrolytic activity toward paraoxon, was encapsulated within peptide nanofibrils, resulting in increased shelf life and retaining ∼50% activity after 132 days since purification. Next, the addition of Arthrobacter sp. 4Hβ, capable of degrading para-nitrophenol (PNP), the hydrolysis product of paraoxon, which is still toxic, resulted in nondetectable levels of PNP. These results present an efficient one-pot system that can be further developed as an environmentally friendly solution, coupling purified enzymes and native bacteria, for pesticide bioremediation. We further suggest that this system can be tailored for different xenobiotics by encapsulating the rate-limiting key enzymes followed by their combination with environmental bacteria that can use the enzymatic step products for full degradation without the need to engineer synthetic bacteria.

A Self-Assembled 3D Model Demonstrates How Stiffness Educates Tumor Cell Phenotypes and Therapy Resistance in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a dense and stiff extracellular matrix (ECM) associated with tumor progression and therapy resistance. To further the understanding of how stiffening of the tumor microenvironment (TME) contributes to aggressiveness, a three-dimensional (3D) self-assembling hydrogel disease model is developed based on peptide amphiphiles (PAs, PA-E3Y) designed to tailor stiffness. The model displays nanofibrous architectures reminiscent of native TME and enables the study of the invasive behavior of PDAC cells. Enhanced tuneability of stiffness is demonstrated by interacting thermally annealed aqueous solutions of PA-E3Y (PA-E3Yh) with divalent cations to create hydrogels with mechanical properties and ultrastructure similar to native tumor ECM. It is shown that stiffening of PA-E3Yh hydrogels to levels found in PDAC induces ECM deposition, promotes epithelial-to-mesenchymal transition (EMT), enriches CD133+/CXCR4+ cancer stem cells (CSCs), and subsequently enhances drug resistance. The findings reveal how a stiff 3D environment renders PDAC cells more aggressive and therefore more faithfully recapitulates in vivo tumors.

Tuning Surface Organic Structures by Small Gas Molecules through Catassembly and Coassembly

The field of molecular assembly has seen remarkable advancements across various domains, such as materials science, nanotechnology, and biomedicine. Small gas molecules serve as pivotal modulators, capable of altering the architecture of assemblies via tuning a spectrum of intermolecular forces including hydrogen bonding, dipole-dipole interactions, and metal coordination. Surface techniques, notably scanning tunneling microscopy and atomic force microscopy, have proven instrumental in dissecting the structural metamorphosis and characteristic features of these assemblies at an unparalleled single-molecule resolution. Recent research has spotlighted two innovative approaches for modulating surface molecular assemblies with the aid of small gas molecules: "catassembly" and "coassembly". This Perspective delves into these methodologies through the lens of varying molecular interaction types. The strategies discussed here for regulating molecular assembly structures using small gas molecules can aid in understanding various complex assembly processes and structures and provide guidance for the further fabrication of complex surface structures.

Salt-induced Fmoc-tripeptide supramolecular hydrogels: a combined experimental and computational study of the self-assembly

Delving into the mechanism behind the molecular interactions at the atomic level of short-sequence peptides plays a key role in the development of nanomaterials with specific structure-property-function relationships from a bottom-up perspective. Due to their poor water solubility, the self-assembly of Fmoc-bearing peptides is usually induced by dissolution in an organic solvent, followed by a dilution step in water, pH changes, and/or a heating-cooling process. Herein, we report a straightforward methodology for the gelation of Fmoc-FFpY (F: phenylalanine; Y: tyrosine; and p: PO42-), a negatively charged tripeptide, in NaCl solution. The electrostatic interactions between Fmoc-FFpY and Na+ ions give rise to different nanofibrillar hydrogels with rheological properties and nanofiber sizes modulated by the NaCl concentration in pure aqueous media. Initiated by the electrostatic interactions between the peptide phosphate groups and the Na+ ions, the peptide self-assembly is stabilized thanks to hydrogen bonds between the peptide backbones and the π-π stacking of aromatic Fmoc and phenyl units. The hydrogels showed self-healing and thermo-responsive properties for potential biomedical applications. Molecular dynamics simulations from systems devoid of prior training not only confirm the aggregation of peptides at a critical salt concentration and the different interactions involved, but also corroborate the secondary structure of the hydrogels at the microsecond timescale. It is worth highlighting the remarkable achievement of reproducing the morphological behavior of the hydrogels using atomistic simulations. To our knowledge, this study is the first to report such a correspondence.

Revolution in Cancer Treatment: How Are Intelligently Designed Nanostructures Changing the Game?

Nanoparticles (NPs) are extremely important tools to overcome the limitations imposed by therapeutic agents and effectively overcome biological barriers. Smart designed/tuned nanostructures can be extremely effective for cancer treatment. The selection and design of nanostructures and the adjustment of size and surface properties are extremely important, especially for some precision treatments and drug delivery (DD). By designing specific methods, an important era can be opened in the biomedical field for personalized and precise treatment. Here, we focus on advances in the selection and design of nanostructures, as well as on how the structure and shape, size, charge, and surface properties of nanostructures in biological fluids (BFs) can be affected. We discussed the applications of specialized nanostructures in the therapy of head and neck cancer (HNC), which is a difficult and aggressive type of cancer to treat, to give an impetus for novel treatment approaches in this field. We also comprehensively touched on the shortcomings, current trends, and future perspectives when using nanostructures in the treatment of cancer.

Stabilization of Lantern-Type Metal-Organic Cages (MOCs) by Protective Control of Ligand Exchange Rates

Self-assembling systems in nature display remarkable complexity with assemblies of different sub-units to generate functional species. Synthetic analogues of such systems are a challenge, often requiring the ability to bias distributions that are under thermodynamic assembly control. Using lantern-type MOCs (metal-organic cages) as a prototypical self-assembling system, herein we explore the role that steric bulk plays in controlling the exchange rate of ligands in paddlewheel-based assemblies, and thus the stability of cages, in competitive self-assembling scenarios. The effective lifetime of the lantern-type MOCs varies over an order of magnitude depending on the steric bulk proximal to the metal nodes with lifetimes of the cages ranging from tens of minutes to several hours. The bulk of the coordinating solvents likewise reduces the rate of ligand exchange, and thus yields longer-lived species. Understanding this subtle effect has implications for controlling the stability of complex assemblies in competitive environments with implications for guest release and application.

Redox-Regulated In Situ Seed-Induced Assembly of Peptides

Morphology-transformational self-assembly of peptides allows for manipulation of the performance of nanostructures and thereby advancing the development of biomaterials. Acceleration of the morphological transformation process under a biological microenvironment is important to efficiently implement the tailored functions in living systems. Herein, we report redox-regulated in situ seed-induced assembly of peptides via design of two co-assembled bola-amphiphiles serving as a redox-resistant seed and a redox-responsive assembly monomer, respectively. Both of the peptides are able to independently assemble into nanoribbons, while the seed monomer exhibits stronger assembling propensity. The redox-responsive monomer undergoes morphological transformation from well-defined nanoribbons to nanoparticles. Kinetics studies validate the role of the assembled inert monomer as the seeds in accelerating the assembly of the redox-responsive monomer. Alternative addition of oxidants and reductants into the co-assembled monomers promotes the redox-regulated assembly of the peptides facilitated by the in situ-formed seeds. The reduction-induced assembly of the peptide could also be accelerated by in situ-formed seeds in cancer cells with a high level of reductants. Our findings demonstrate that through precisely manipulating the assembling propensity of co-assembled monomers, the in situ seed-induced assembly of peptides could be achieved. Combining the rapid assembly kinetics of the seed-induced assembly with the common presence of redox agents in a biological microenvironment, this strategy potentially offers a new method for developing biomedical materials in living systems.

Understanding multicomponent low molecular weight gels from gelators to networks

BACKGROUND

The construction of gels from low molecular weight gelators (LMWG) has been extensively studied in the fields of bio-nanotechnology and other fields. However, the understanding gaps still prevent the prediction of LMWG from the full design of those gel systems. Gels with multicomponent become even more complicated because of the multiple interference effects coexist in the composite gel systems.

AIM OF REVIEW

This review emphasizes systems view on the understanding of multicomponent low molecular weight gels (MLMWGs), and summarizes recent progress on the construction of desired networks of MLMWGs, including self-sorting and co-assembly, as well as the challenges and approaches to understanding MLMWGs, with the hope that the opportunities from natural products and peptides can speed up the understanding process and close the gaps between the design and prediction of structures.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review is focused on three key concepts. Firstly, understanding the complicated multicomponent gels systems requires a systems perspective on MLMWGs. Secondly, several protocols can be applied to control self-sorting and co-assembly behaviors in those multicomponent gels system, including the certain complementary structures, chirality inducing and dynamic control. Thirdly, the discussion is anchored in challenges and strategies of understanding MLMWGs, and some examples are provided for the understanding of multicomponent gels constructed from small natural products and subtle designed short peptides.

Controlled Bio-Orthogonal Catalysis Using Nanozyme-Protein Complexes via Modulation of Electrostatic Interactions

Bio-orthogonal chemistry provides a powerful tool for drug delivery systems due to its ability to generate therapeutic agents in situ, minimizing off-target effects. Bio-orthogonal transition metal catalysts (TMCs) with stimuli-responsive properties offer possibilities for controllable catalysis due to their spatial-, temporal-, and dosage-controllable properties. In this paper, we fabricated a stimuli-responsive bio-orthogonal catalysis system based on an enhanced green fluorescent protein (EGFP)-nanozyme (NZ) complex (EGFP-NZ). Regulation of the catalytic properties of the EGFP-NZ complex was directly achieved by modulating the ionic strength of the solution. The dielectric screening introduced by salt ions allows the dissociation of the EGFP-NZ complex, increasing the access of substrate to the active site of the NZs and concomitantly increasing nanozyme activity. The change in catalytic rate of the NZ/EGFP = 1:1 complex was positively correlated with salt concentration from 0 mM to 150 mM.

Self-assembly of peptide nanomaterials at biointerfaces: molecular design and biomedical applications

Self-assembly is an important strategy for constructing ordered structures and complex functions in nature. Based on this, people can imitate nature and artificially construct functional materials with novel structures through the supermolecular self-assembly pathway of biological interfaces. Among the many assembly units, peptide molecular self-assembly has received widespread attention in recent years. In this review, we introduce the interactions (hydrophobic interaction, hydrogen bond, and electrostatic interaction) between peptide nanomaterials and biological interfaces, summarizing the latest advancements in multifunctional self-assembling peptide materials. We systematically demonstrate the assembly mechanisms of peptides at biological interfaces, such as proteins and cell membranes, while highlighting their application potential and challenges in fields like drug delivery, antibacterial strategies, and cancer therapy.

Preserving Structurally Labile Peptide Nanosheets After Molecular Functionalization of the Self-Assembling Peptides

A significant challenge in creating supramolecular materials is that conjugating molecular functionalities to building blocks often results in dissociation or undesired morphological transformation of their assemblies. Here we present a facile strategy to preserve structurally labile peptide assemblies after molecular modification of the self-assembling peptides. Sheet-forming peptides are designed to afford a staggered alignment with the segments bearing chemical modification sites protruding from the sheet surfaces. The staggered assembly allows for simultaneous separation of attached molecules from each other and from the underlying assembly motifs. Strikingly, using PEGs as the external molecules, PEG400 - and PEG700 -peptide conjugates directly self-associate into nanosheets with the PEG chains localized on the sheet surfaces. In contrast, the sheet formation based on in-register lateral packing of peptides does not recur upon the peptide PEGylation. This strategy allows for fabrication of densely modified assemblies with a variety of molecules, as demonstrated using biotin (hydrophobic molecule), c(RGDfK) (cyclic pentapeptide), and nucleic acid aptamer (negatively charged ssDNA). The staggered co-assembly also enables extended tunability of the amount/density of surface molecules, as exemplified by screening ligand-appended assemblies for cell targeting. This study paves the way for functionalization of historically challenging fragile assemblies while maintaining their overall morphology.

Enzyme-Responsive Nanoparticles for Dexamethasone Targeted Delivery to Treat Inflammation in Diabetes

Diabetes is a global epidemic accompanied by impaired wound healing and increased risk of persistent infections and resistance to standard treatments. Therefore, there is an immense need to develop novel methods to specifically target therapeutics to affected tissues and improve treatment efficacy. This study aims to use enzyme-responsive nanoparticles for the targeted delivery of an anti-inflammatory drug, dexamethasone, to treat inflammation in diabetes. These nanoparticles are assembled from fluorescently-labeled, dexamethasone-loaded peptide-polymer amphiphiles. The nanoparticles are injected in vivo, adjacent to labeled collagen membranes sub-periosteally implanted on the calvaria of diabetic rats. Following their implantation, collagen membrane resorption is linked to inflammation, especially in hyperglycemic individuals. The nanoparticles show strong and prolonged accumulation in inflamed tissue after undergoing a morphological switch into microscale aggregates. Significantly higher remaining collagen membrane area and less inflammatory cell infiltration are observed in responsive nanoparticles-treated rats, compared to control groups injected with free dexamethasone and non-responsive nanoparticles. These factors indicate improved therapeutic efficacy in inflammation reduction. These results demonstrate the potential use of enzyme-responsive nanoparticles as targeted delivery vehicles for the treatment of diabetic and other inflammatory wounds.

Peptide-Protein Coassemblies into Hierarchical and Bioactive Tubular Membranes

Multicomponent self-assembly offers opportunities for the design of complex and functional biomaterials with tunable properties. Here, we demonstrate how minor modifications in the molecular structures of peptide amphiphiles (PAs) and elastin-like recombinamers (ELs) can be used to generate coassembling tubular membranes with distinct structures, properties, and bioactivity. First, by introducing minor modifications in the charge density of PA molecules (PAK2, PAK3, PAK4), different diffusion-reaction processes can be triggered, resulting in distinct membrane microstructures. Second, by combining different types of these PAs prior to their coassembly with ELs, further modifications can be achieved, tuning the structures and properties of the tubular membranes. Finally, by introducing the cell adhesive peptide RGDS in either the PA or EL molecules, it is possible to harness the different diffusion-reaction processes to generate tubular membranes with distinct bioactivities. The study demonstrates the possibility to trigger and achieve minor but crucial differences in coassembling processes and tune material structure and bioactivity. The study demonstrates the possibility to use minor, yet crucial, differences in coassembling processes to tune material structure and bioactivity.

Precursor template-induced egg white-derived peptides self-assembly for the enhancement of curcumin: Structure, environmental stability, and bioavailability

Natural multicomponent peptides with abundant bioactivity, varied sizes, and tunable interaction potential are available for rational designing novel self-assembled delivery carriers. Herein, we exploited zein-hyaluronic acid nanoparticles (Z-HA NPs) with a predetermined ordered structure as precursor templates to induce the self-assembly of egg white-derived peptides (EWDP) to generate stable spherical architectures for the enhancement of curcumin (Cur). The resulting Z-EWDP-HA NPs encapsulated hydrophobic Cur through robust hydrogen bonding and hydrophobic interactions with high encapsulation efficiency (97.38% at pH 7.0). The NPs presented superior Cur aqueous solubility, redispersibility, and photothermal stability. More importantly, the self-assembled EWDP could exert synergistic antioxidant activity with Cur and enhance the bioaccessibility of Cur. Meanwhile, the favorable biocompatibility and membrane affinity of EWDP further prolonged residence and time-controlled release feature of Cur in the small intestine. Precursor template-induced multicomponent peptides' self-assembly provides an efficient and controllable strategy for co-enhanced bioactivity and self-assembly capacity of peptides, which could dramatically broaden the functionalization of multicomponent peptides hydrolyzed from natural food proteins.

Self-Assembly of Platelet Lysates Proteins into Microparticles by Unnatural Disulfide Bonds for Bottom-Up Tissue Engineering

There is a demand to design microparticles holding surface topography while presenting inherent bioactive cues for applications in the biomedical and biotechnological fields. Using the pool of proteins present in human-derived platelet lysates (PLs), the production of protein-based microparticles via a simple and cost-effective method is reported, exploring the prone redox behavior of cysteine (Cy-SH) amino acid residues. The forced formation of new intermolecular disulfide bonds results in the precipitation of the proteins as spherical, pompom-like microparticles with adjustable sizes (15-50 µm in diameter) and surface topography consisting of grooves and ridges. These PL microparticles exhibit extraordinary cytocompatibility, allowing cell-guided microaggregates to form, while also working as injectable systems for cell support. Early studies also suggest that the surface topography provided by these PL microparticles can support osteogenic behavior. Consequently, these PL microparticles may find use to create live tissues via bottom-up procedures or injectable tissue-defect fillers, particularly for bone regeneration, with the prospect of working under xeno-free conditions.

Two-dimensional self-assembly and co-assembly of two tetracarboxylic acid derivatives investigated by STM

In this work, the two-dimensional self-assembly and co-assembly behaviors of two tetracarboxylic acid derivatives (H4BDETP and H4BTB) were investigated by scanning tunneling microscopy (STM). H4BDETP molecules self-assembled into linear nanostructures, and H4BTB molecules formed lamellar and tetragonal nanostructures. The formation of a H4BDETP/H4BTB co-assembly nanostructure was closely related to the deposition sequence of H4BDETP and H4BTB on highly oriented pyrolytic graphite (HOPG). The introduction of H4BTB into the self-assembly system of H4BDETP resulted in the emergence of the H4BDETP/H4BTB nanostructure, while the addition of H4BDETP had no effect on the self-assembly system of H4BTB and a H4BDETP/H4BTB co-assembly nanostructure was not obtained.

Tryptophan-PNA gc Conjugates Self-Assemble to Form Fibers

Peptide nucleic acids and their conjugates to peptides can self-assemble and generate complex architectures. In this work, we explored the self-assembly of PNA dimers conjugated to the dipeptide WW. Our studies suggest that the indole ring of tryptophan promotes aggregation of the conjugates. The onset of fluorescence is observed upon self-assembly. The structure of self-assembled WWgc is concentration-dependent, being spherical at low concentrations and fibrous at high concentrations. As suggested by molecular modeling studies, fibers are stabilized by stacking interactions between tryptophans and Watson-Crick hydrogen bonds between nucleobases.

3D Printing of Extracellular Matrix-Based Multicomponent, All-Natural, Highly Elastic, and Functional Materials toward Vascular Tissue Engineering

3D printing offers an exciting opportunity to fabricate biological constructs with specific geometries, clinically relevant sizes, and functions for biomedical applications. However, successful application of 3D printing is limited by the narrow range of printable and bio-instructive materials. Multicomponent hydrogel bioinks present unique opportunities to create bio-instructive materials able to display high structural fidelity and fulfill the mechanical and functional requirements for in situ tissue engineering. Herein, 3D printable and perfusable multicomponent hydrogel constructs with high elasticity, self-recovery properties, excellent hydrodynamic performance, and improved bioactivity are reported. The materials' design strategy integrates fast gelation kinetics of sodium alginate (Alg), in situ crosslinking of tyramine-modified hyaluronic acid (HAT), and temperature-dependent self-assembly and biological functions of decellularized aorta (dAECM). Using extrusion-based printing approach, the capability to print the multicomponent hydrogel bioinks with high precision into a well-defined vascular constructs able to withstand flow and repetitive cyclic compressive loading, is demonstrated. Both in vitro and pre-clinical models are used to show the pro-angiogenic and anti-inflammatory properties of the multicomponent vascular constructs. This study presents a strategy to create new bioink whose functional properties are greater than the sum of their components and with potential applications in vascular tissue engineering and regenerative medicine.

Manipulating supramolecular gels with surfactants: Interfacial and non-interfacial mechanisms

Gel is a class of self-supporting soft materials with applications in many fields. Fast, controllable gelation, micro/nano structure and suitable rheological properties are essential considerations for the design of gels for specific applications. Many methods can be used to control these parameters, among which the additive approach is convenient as it is a simple physical mixing process with significant advantages, such as avoidance of pH change and external energy fields (ultrasound, UV light and others). Although surfactants are widely used to control the formation of many materials, particularly nanomaterials, their effects on gelation are less known. This review summarizes the studies that utilized different surfactants to control the formation, structure, and properties of molecular and silk fibroin gels. The mechanisms of surfactants, which are interfacial and non-interfacial effects, are classified and discussed. Knowledge and technical gaps are identified, and perspectives for further research are outlined. This review is expected to inspire increasing research interest in using surfactants for designing/fabricating gels with desirable formation kinetics, structure, properties and functionalities.

A Comprehensive Review of Self-Assembled Food Protein-Derived Multicomponent Peptides: From Forming Mechanism and Structural Diversity to Applications

Food protein-derived multicomponent peptides (FPDMPs) are a natural blend of numerous peptides with various bioactivities and multiple active sites that can assume several energetically favorable conformations in solutions. The remarkable structural characteristics and functional attributes of FPDMPs make them promising codelivery carriers that can coassemble with different bioactive ingredients to induce multidimensional structures, such as fibrils, nanotubes, and nanospheres, thereby producing specific health benefits. This review offers a prospective analysis of FPDMPs-based self-assembly nanostructures, focusing on the mechanism of formation of self-assembled FPDMPs, the internal and external stimuli affecting peptide self-assembly, and their potential applications. In particular, we introduce the exciting prospect of constructing functional materials through precursor template-induced self-assembly of FPDMPs, which combine the bioactivity and self-assembly capacity of peptides and could dramatically broaden the functional utility of peptide-based materials.

Genetic Fusion of Thermoresponsive Polypeptides with UCST-type Behavior Mediates 1D Assembly of Coiled-Coil Bundlemers

Thermoresponsive resilin-like polypeptides (RLPs) of various lengths were genetically fused to two different computationally designed coiled coil-forming peptides with distinct thermal stability, to develop new strategies to assemble coiled coil peptides via temperature-triggered phase separation of the RLP units. Their successful production in bacterial expression hosts was verified via gel electrophoresis, mass spectrometry, and amino acid analysis. Circular dichroism (CD) spectroscopy, ultraviolet-visible (UV/Vis) turbidimetry, and dynamic light scattering (DLS) measurements confirmed the stability of the coiled coils and showed that the thermosensitive phase behavior of the RLPs was preserved in the genetically fused hybrid polypeptides. Cryogenic-transmission electron microscopy and coarse-grained modeling revealed that functionalizing the coiled coils with thermoresponsive RLPs leads to their thermally triggered noncovalent assembly into nanofibrillar assemblies.

Stimuli-Responsive Self-Assembly Disassembly in Peptide Amphiphiles to Endow Block-co-Fibers and Tunable Piezoelectric Response

Supramolecular assemblies with well-defined structural attenuation toward varied functional implications are an emerging area in mimicking natural biomaterials. In that regard, the redox stimuli-responsive ferrocene moiety can reversibly change between a nonpolar ferrocenyl and polar ferrocenium cation that endows interesting modular features to the building blocks with respect to self-assembly/disassembly. We design a series of ferrocene anchored peptide fragment ^NVFFAKK^C using hydrophobic alkyl spacers of different chain lengths. Increasing the spacer length between the redox-responsive and self-assembling motifs increases the propensity to form robust nanofibers, which can be physically cross-linked to form hydrogels. The controlled redox response of the ferrocene moiety tandem with pH control provides access to structural control over the peptide nanostructures and tunable mechanical strengths. Further, such redox-sequestered dormant states hinder the spontaneous nucleation process that we exploit toward seeded supramolecular polymerization to form block cofibers composed of redox-responsive periphery and nonresponsive cores. Finally, such redox sequestration of peptide self-assembly renders an on-off piezoelectric response for potential utilization in peptide bioelectronics.

Designing ECM-inspired supramolecular scaffolds by utilizing the interactions between a minimalistic neuroactive peptide and heparin

Short bioactive peptide-based supramolecular hydrogels are emerging as interesting candidates for developing scaffolds for tissue engineering applications. However, proteins and peptides represent only a single class of molecules present in the native ECM, thus, recapitulating the complete ECM microenvironment via only peptide-based biomaterials is extremely challenging. In this direction, complex multicomponent-based biomaterials have started gaining importance for achieving the biofunctional complexity and structural hierarchy of the native ECM. Sugar-peptide complexes can be explored in this direction as they provide essential biological signaling required for cellular growth and survival in vivo. In this direction, we explored the fabrication of an advanced scaffold by employing heparin and short bioactive peptide interactions at the molecular level. Interestingly, the addition of heparin into the peptide has significantly modulated the supramolecular organization, nanofibrous morphology and the mechanical properties of the scaffold. Additionally, the combined hydrogels demonstrated superior biocompatibility as compared to the peptide counterpart at certain ratios. These newly developed scaffolds were also observed to be stable under 3-D cell culture conditions and supported cellular adhesion and proliferation. Most importantly, the inflammatory response was also minimized in the case of combined hydrogels as compared to heparin. We expect that this approach of using simple non-covalent interactions between the ECM-inspired small molecules to fabricate biomaterials with improved mechanical and biological properties could advance the current knowledge on designing ECM mimetic biomaterials. Such an attempt would create a novel, adaptable and simplistic bottom-up strategy for the invention of new and more complex biomaterials of ECM origin with advanced functions.

Delivery of Active Peptides by Self-Healing, Biocompatible and Supramolecular Hydrogels

Supramolecular and biocompatible hydrogels with a tunable pH ranging from 5.5 to 7.6 lead to a wide variety of formulations useful for many different topical applications compatible with the skin pH. An in vitro viability/cytotoxicity test of the gel components demonstrated that they are non-toxic, as the cells continue to proliferate after 48 h. An analysis of the mechanical properties demonstrates that the hydrogels have moderate strength and an excellent linear viscoelastic range with the absence of a proper breaking point, confirmed with thixotropy experiments. Two cosmetic active peptides (Trifluoroacetyl tripeptide-2 and Palmitoyl tripeptide-5) were successfully added to the hydrogels and their transdermal permeation was analysed with Franz diffusion cells. The liquid chromatography-mass spectrometry (HPLC-MS) analyses of the withdrawn samples from the receiving solutions showed that Trifluoroacetyl tripeptide-2 permeated in a considerable amount while almost no transdermal permeation of Palmitoyl tripeptide-5 was observed.

Advances in Peptide-Based Hydrogel for Tissue Engineering

The development of peptide-based materials has emerged as one of the most challenging aspects of biomaterials in recent years. It has been widely acknowledged that peptide-based materials can be used in a broad range of biomedical applications, particularly in tissue engineering. Among them, hydrogels have been attracting considerable interest in tissue engineering because they mimic tissue formation conditions by providing a three-dimensional environment and a high water content. It has been found that peptide-based hydrogels have received more attention due to mimicking proteins, particularly extracellular matrix proteins, as well as the wide variety of applications they are capable of serving. It is without a doubt that peptide-based hydrogels have become the leading biomaterials of today owing to their tunable mechanical stability, high water content, and high biocompatibility. Here, we discuss in detail various types of peptide-based materials, emphasizing peptide-based hydrogels, and then we examine in detail how hydrogels are formed, paying particular attention to the peptide structures that are incorporated into the final structure. Following that, we discuss the self-assembly and formation of hydrogels under various conditions, as well as the parameters to be considered as critical factors, which include pH, amino acid composi- tion within the sequence, and cross-linking techniques. Further, recent studies on the development of peptide-based hydrogels and their applications in tissue engineering are reviewed.

Self-Assembling Peptide-Based Functional Biomaterials

Peptides can self-assemble into various hierarchical nanostructures through noncovalent interactions and form functional materials exhibiting excellent chemical and physical properties, which have broad applications in bio-/nanotechnology. The self-assembly mechanism, self-assembly morphology of peptide supramolecular architecture and their various applications, have been widely explored which have the merit of biocompatibility, easy preparation, and controllable functionality. Herein, we introduce the latest research progress of self-assembling peptide-based nanomaterials and review their applications in biomedicine and optoelectronics, including tissue engineering, anticancer therapy, biomimetic catalysis, energy harvesting. We believe that this review will inspire the rational design and development of novel peptide-based functional bio-inspired materials in the future.

Self-assembly hydrogels of therapeutic agents for local drug delivery

Advanced drug delivery systems are of vital importance to enhance therapeutic efficacy. Among various recently developed formulations, self-assembling hydrogels composed of therapeutic agents have shown promising potential for local drug delivery owing to their excellent biocompatibility, high drug-loading efficiency, low systemic toxicity, and sustained drug release behavior. In particular, therapeutic agents self-assembling hydrogels with well-defined nanostructures are beneficial for direct delivery to the target site via injection, not only improving drug availability, but also extending their retention time and promoting cellular uptake. In brief, the self-assembly approach offers better opportunities to improve the precision of pharmaceutical treatment and achieve superior treatment efficacies. In this review, we intend to cover the recent developments in therapeutic agent self-assembling hydrogels. First, the molecular structures, self-assembly mechanisms, and application of self-assembling hydrogels are systematically outlined. Then, we summarize the various self-assembly strategies, including the single therapeutic agent, metal-coordination, enzyme-instruction, and co-assembly of multiple therapeutic agents. Finally, the potential challenges and future perspectives are discussed. We hope that this review will provide useful insights into the design and preparation of therapeutic agent self-assembling hydrogels.

Chemical strategies to engineer hydrogels for cell culture

Two-dimensional and three-dimensional cell culture systems are widely used for biological studies, and are the basis of the organoid, tissue engineering and organ-on-chip research fields in applications such as disease modelling and drug screening. The natural extracellular matrix of tissues, a complex scaffold with varying chemical and mechanical properties, has a critical role in regulating important cellular functions such as spreading, migration, proliferation and differentiation, as well as tissue morphogenesis. Hydrogels are biomaterials that are used in cell culture systems to imitate critical features of a natural extracellular matrix. Chemical strategies to synthesize and tailor the properties of these hydrogels in a controlled manner, and manipulate their biological functions in situ, have been developed. In this Review, we provide the rational design criteria for predictably engineering hydrogels to mimic the properties of the natural extracellular matrix. We highlight the advances in using biocompatible strategies to engineer hydrogels for cell culture along with recent developments to dynamically control the cellular environment by exploiting stimuli-responsive chemistries. Finally, future opportunities to engineer hydrogels are discussed, in which the development of novel chemical methods will probably have an important role.

Peptide-Based Low Molecular Weight Photosensitive Supramolecular Gelators

Over the last couple of decades, stimuli-responsive supramolecular gels comprising synthetic short peptides as building blocks have been explored for various biological and material applications. Though a wide range of stimuli has been tested depending on the structure of the peptides, light as a stimulus has attracted extensive attention due to its non-invasive, non-contaminant, and remotely controllable nature, precise spatial and temporal resolution, and wavelength tunability. The integration of molecular photo-switch and low-molecular-weight synthetic peptides may thus provide access to supramolecular self-assembled systems, notably supramolecular gels, which may be used to create dynamic, light-responsive "smart" materials with a variety of structures and functions. This short review summarizes the recent advancement in the area of light-sensitive peptide gelation. At first, a glimpse of commonly used molecular photo-switches is given, followed by a detailed description of their incorporation into peptide sequences to design light-responsive peptide gels and the mechanism of their action. Finally, the challenges and future perspectives for developing next-generation photo-responsive gels and materials are outlined.

Exploiting Minimalistic Backbone Engineered γ-Phenylalanine for the Formation of Supramolecular Co-Polymer

Ordered supramolecular hydrogels assembled by modified aromatic amino acids often exhibit low mechanical rigidity. Aiming to stabilize the hydrogel and understand the impact of conformational freedom and hydrophobicity on the self-assembly process, we designed two building blocks based on 9-fluorenyl-methoxycarbonyl-phenylalanine (Fmoc-Phe) gelator which contain two extra methylene units in the backbone, generating Fmoc-γPhe and Fmoc-(3-hydroxy)-γPhe. Fmoc-γPhe spontaneously assembled in aqueous media forming a hydrogel with exceptional mechanical and thermal stability. Moreover, Fmoc-(3-hydroxy)-γPhe, with an extra backbone hydroxyl group decreasing its hydrophobicity while maintaining some molecular flexibility, self-assembled into a transient fibrillar hydrogel, that later formed microcrystalline aggregates through phase transition. Molecular dynamics simulations and single crystal X-ray analyses revealed the mechanism underlying the two residues' distinct self-assembly behaviors. Finally, we demonstrated Fmoc-γPhe and Fmoc-(3-OH)-γPhe co-assembly to form a supramolecular hydrogel with notable mechanical properties. We believe that the understanding of the structure-assembly relationship will enable the design of new functional amino acid-based hydrogels. This article is protected by copyright. All rights reserved.

Polyaniline Functionalized Peptide Self-Assembled Conductive Hydrogel for 3D Cell Culture

The functionalization of self-assembled peptide hydrogel is of great importance to broaden its applications in the field of biomedicine. In this work, conductive hydrogel is fabricated by introducing conductive polymer polyaniline into peptide self-assembled hydrogel. Compared with pure peptide formed hydrogel, the conductive hydrogel exhibits enhanced conductivity, mechanical property and stability. In addition, the hydrogel is tested to be of great injectability and 3D bio-printability and could support the viability of encapsulated cells that are sensitive to electrical signals. It should have great application prospects in the preparation of tissue engineering scaffolds.

Chemical crosslinking in 'reactive' multicomponent gels

We show that the hydrolysis of EDC can be used to construct a reactive system to trigger permanent covalent crosslinking between the components in multicomponent gels comprising gelators with a carboxylic acid and amine group yielding an amide functionalized gel with enhanced mechanical properties.

Conformationally engineering flexible peptides on silver nanoparticles

Molecular conformational engineering is to engineer flexible non-functional molecules into unique conformations to create novel functions just like natural proteins fold. Obviously, it is a grand challenge with tremendous opportunities. Based on the facts that natural proteins are only marginally stable with a net stabilizing energy roughly equivalent to the energy of two hydrogen bonds, and the energy barriers for the adatom diffusion of some metals are within a similar range, we propose that metal nanoparticles can serve as a general replacement of protein scaffolds to conformationally engineer protein fragments on the surface of nanoparticles. To prove this hypothesis, herein, we successfully restore the antigen-recognizing function of the flexible peptide fragment of a natural anti-lysozyme antibody on the surface of silver nanoparticles, creating a silver nanoparticle-base artificial antibody (Silverbody). A plausible mechanism is proposed, and some general principles for conformational engineering are summarized to guide future studies in this area.

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A silver NP-based artificial antibody is created by conformational engineering

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Function emerges on NPs from non-functional peptide by mimicking the protein folding

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A general mechanism is proposed for the conformational engineering on metal NPs

Self-assembly of fullerene C60-based amphiphiles in solutions

Fullerene C₆₀ is an all-carbon cage molecule with rich physicochemical properties. It is highly symmetric and hydrophobic, which can be used as a building block for the preparation of amphiphiles that self-assemble into diverse supramolecular structures in aqueous solutions. Meanwhile, C₆₀ is also lipophobic, which is different from the alkyl chains in traditional surfactants. By attaching alkyl chains to the C₆₀ sphere, a new type of lipophobic-lipophilic amphiphiles can be constructed which undergo self-assembly in n-alkanes. When inorganic clusters such as polyoxometalate are linked to the C₆₀ sphere, organic-inorganic hybrids will be obtained which can self-assemble in polar organic solvents. Pristine C₆₀ has also been modified by polar groups such as hydroxy and carboxy, which are linked to hydrophobic moieties and form a new class of amphiphiles. In this review, the self-assembly of C₆₀-based amphiphiles in aqueous and nonaqueous solutions will be summarized. The characteristics exhibited by C₆₀-based amphiphiles during the self-assembly will be discussed with close comparison to traditional surfactants, and the influences of the aggregate formation on the physicochemical properties of the C₆₀ sphere will be described. Finally, a brief summary will be given together with a promising perspective in near future.

Embedding Proteins within Spatially Controlled Hierarchical Nanoarchitectures for Ultrasensitive Immunoassay

Modulating the precise self-assembly of functional biomacromolecules is a critical challenge in biotechnology. Herein, functional biomacromolecule-assembled hierarchical hybrid nanoarchitectures in a spatially controlled fashion are synthesized, achieving the biorecognition behavior and signal amplification in the immunoassay simultaneously. Biomacromolecules with sequential assembly on the scaffold through the biomineralization process show significantly enhanced stability, bioactivity, and utilization efficiency, allowing tuning of their functions by modifying their size and composition. The hierarchically hybrid nanoarchitectures show great potential in construction of ultrasensitive immunoassay platforms, achieving a three order-of-magnitude increase in sensitivity. Notably, the well-designed HRP@Ab₂ nanoarchitectures allow for optical immunoassays with a detection range from picogram mL^-1 to microgram mL^-1 on demand, providing great promise for quantitative analysis of both low-abundance and high-residue targets for biomedical applications.

Emerging low-molecular weight nucleopeptide-based hydrogels: state of the art, applications, challenges and perspectives

Over the last twenty years, low-molecular weight gelators and, in particular, peptide-based hydrogels, have drawn great attention from scientists thanks to both their inherent advantages in terms of properties and their high modularity (e.g., number and nature of the amino acids). These supramolecular hydrogels originate from specific peptide self-assembly processes that can be driven, modulated and optimized via specific chemical modifications brought to the peptide sequence. Among them, the incorporation of nucleobases, another class of biomolecules well-known for their abilities to self-assemble, has recently appeared as a new promising and burgeoning approach to finely design supramolecular hydrogels. In this minireview, we would like to highlight the interest, high potential, applications and perspectives of these innovative and emerging low-molecular weight nucleopeptide-based hydrogels.

All-in-one biofabrication and loading of recombinant vaults in human cells

One of the most promising approaches in the drug delivery field is the use of naturally occurring self-assembling protein nanoparticles, such as virus-like particles, bacterial microcompartments or vault ribonucleoprotein particles as drug delivery systems (DDS). Among them, eukaryotic vaults show a promising future due to their structural features, in vitro stability and non-immunogenicity. Recombinant vaults are routinely produced in insect cells and purified through several ultracentrifugations, both tedious and time-consuming processes. As an alternative, this work proposes a new approach and protocols for the production of recombinant vaults in human cells by transient gene expression of a His-tagged version of the Major Vault Protein (MVP-H6), the development of new affinity-based purification processes for such recombinant vaults, and the all-in-one biofabrication and encapsulation of a cargo recombinant protein within such vaults by their co-expression in human cells. Protocols proposed here allow the easy and straightforward biofabrication and purification of engineered vaults loaded with virtually any INT-tagged cargo protein, in very short times, paving the way to faster and easier engineering and production of better and more efficient DDS.

Peptide-Based Sensing, Logic Computing, and Information Security on the Antimonene Platform

Peptides have higher information density than DNA and equivalent molecular recognition ability and durability. However, there are currently no reports on the comprehensive use of peptides' recognition ability and structural diversity for sensing, logic computing, information coding, and protection. Herein, we, for the first time, demonstrate peptide-based sensing, logic computing, and information security on the antimonene platform. The molecular recognition capability and structural diversity (amino acid sequence) of peptides (Pb²⁺-binding peptide DHHTQQHD as a model) adsorbed on the antimonene universal fluorescence quenching platform were comprehensively utilized to sense targets (Pb²⁺) and give a response (fluorescence turn-on) and then to encode, encrypt, and hide information. Fluorescently labeled peptides used as the recognition probe and the information carrier were quenched and hidden by the large-plane two-dimensional material antimonene and specifically bound by Pb²⁺ as the stego key, resulting in fluorescence recovery. The above interaction and signal change can be considered as a peptide-based sensing and steganographic process to further implement quantitative detection of Pb²⁺, complex logic operation, information coding, encrypting, and hiding using a peptide sequence and the binary conversion of its selectivity. This research provides a basic paradigm for the construction of a molecular sensing and informatization platform and will inspire the development of biopolymer-based molecular information technology (processing, communication, control, security).

Structure of Self-assembled Peptide Determines the Activity of Aggregation-Induced Emission Luminogen-Peptide Conjugate for Detecting Alkaline Phosphatase

The unique property of turning on their fluorescence after aggregation or assembly makes aggregation-induced emission luminogens (AIEgens) ideal luminescent molecules for the construction of self-assembled peptide-based nanoprobes. However, the characteristic highly twisted or propeller-shaped molecular conformation of AIEgens tends to prevent the assembly of AIEgen-peptides. Here, we show that (i) the distance between tetraphenylethene (TPE) and assembled peptides should not be too far (less than five glycines), otherwise the self-assembly of peptides cannot limit the intramolecular rotation of conjugated TPE and the luminous efficiency of TPE-peptide to alkaline phosphatase (ALP) will decrease; (ii) properly increasing the number of amino acids with self-assembly ability (three phenylalanines) can improve their ALP-responsive self-assembly and luminescence ability; (iii) the strategy of co-assembly with a non-AIEgen-capped self-assembled peptide is a simple and effective way to realize the efficient assembly and luminescence of AIEgen-peptides; and (iv) the hydrophilic and hydrophobic balance of the probe should always be considered in the construction of an efficient AIEgen-peptide probe. In addition, AIEgen-peptide probes show good selectivity and sensitivity for ALP detection both in vitro and in live bacteria. These insights illustrated here are crucial for guiding the design of AIEgen-conjugated supramolecular materials, especially for the construction of AIEgen-peptides, for enzymes detection, biomarker imaging, diseases therapy, and other biomedical fields.

Peptide Amphiphile Hydrogels Based on Homoternary Cucurbit[8]uril Host-Guest Complexes

Supramolecular hydrogels based on peptide amphiphiles (PAs) are promising materials for tissue engineering and model extracellular matrixes for biological studies. While PA hydrogels are conventionally formed via electrostatic screening, new hydrogelation mechanisms might help to improve the design and functionality of these materials. Here, we present a host-guest-mediated PA hydrogelation method that relies on the formation of a host-guest homoternary complex with cucurbit[8]uril (CB[8]) and aromatic amino-acid-bearing PA nanofibers. As a result of the host-guest cross-linking between PA nanofibers, hierarchical morphologies and increased stiffness were found when host-guest-mediated PA hydrogels were compared to their ion-based equivalents. Additionally, both families of hydrogels exhibited similar biocompatibilities. These results demonstrate that CB[8]-mediated hydrogelation can be used as an alternative cross-linking method to upgrade the design of PA materials and extend their biomedical applications.

Disordered Protein Stabilization by Co-Assembly of Short Peptides Enables Formation of Robust Membranes

Molecular self-assembly is a spontaneous natural process resulting in highly ordered nano to microarchitectures. We report temperature-independent formation of robust stable membranes obtained by the spontaneous interaction of intrinsically disordered elastin-like polypeptides (ELPs) with short aromatic peptides at temperatures both below and above the conformational transition temperature of the ELPs. The membranes are stable over time and display durability over a wide range of parameters including temperature, pH, and ultrasound energy. The morphology and composition of the membranes were analyzed using microscopy. These robust structures support preosteoblast cell adhesion and proliferation as well as pH-dependent cargo release. Simple noncovalent interactions with short aromatic peptides can overcome conformational restrictions due to the phase transition to facilitate the formation of complex bioactive scaffolds that are stable over a wide range of environmental parameters. This approach offers novel possibilities for controlling the conformational restriction of intrinsically disordered proteins and using them in the design of new materials.

An atomistic view of rigid crystalline supramolecular polymers derived from short amphiphilic, α,β hybrid peptide

The spontaneous self-association of an amphiphilic α, β-hybrid peptide into supramolecular fibers and atomic details of the fibrillar assembly are reported.

Porous materials formed by four self-construction processes

Multiple self-construction behavior of cyclic oligoesters is described.