Self-Assembling Peptide-Based Functional Biomaterials

Enzyme mimics based on self-assembled peptide functionalized with graphene oxide for polyethylene terephthalate degradation

The degradation of polyethylene terephthalate (PET) has garnered notable attention owing to its widespread accumulation and the challenges associated with its breakdown. Herein, the enzyme mimics with PET-hydrolytic activity were developed by combining peptide nanofibers with graphene oxide (GO). Inspired by native enzymes, we designed self-assembled peptides that included active amino acids (serine, histidine, aspartate and tryptophan) and different hydrophobic amino acids, with a 9-fluorenylmethoxycarbonyl group at the N-terminus. Our comparison of hydrophobic amino acids revealed that their content not only influenced the higher-order assembly of peptide but also affected molecular conformation and PET degradation ability. By co-assembling two peptides with catalytic and binding sites in a 1:1 ratio, a more effective active enzyme mimic was constructed which was owning to the cooperative interactions among the active amino acids; in addition, hydrogen bonds and π-π stacking interactions were the main forces in enhancing catalytic effects. To further improve PET-hydrolytic ability, the co-assembled enzyme mimic was functionalised with GO through π-π stacking. This GO-peptide nanofiber hybrid exhibited increased PET-hydrolytic, as GO provided a hydrophobic microenvironment for substrate attraction and abundant carbon for facilitating proton transfer. The GO-peptide nanofiber hybrid as enzyme mimics will be a promising material for PET degradation.

The potential of carbohydrate supramolecular hydrogels for long-term 3D culture of primary fibroblasts

N-Alkyl-galactonamides, which are small synthetic molecules derived from galactose, self-assemble to give fibrous hydrogels. These molecules are biocompatible and, in a previous study, the cell culture of human neural stem cells was performed for 7 days on a gel of N-heptyl-D-galactonamide. With the objective of broadening the scope of these molecules as scaffolds for cell culture, in the present study, the culture of primary human dermal fibroblasts has been carried out on N-nonyl-D-galactonamide hydrogels. These supramolecular fibrillar hydrogels have a sufficient mechanical strength to withstand cell culture (≈50 kPa) and they are resistant enough on the long term to carry out the cell culture over at least 3 weeks. In contrast to N-heptyl-D-galactonamide, N-nonyl-D-galactonamide is insoluble in the culture medium. It avoids its dissolution at each renewal of the culture medium. The molecule is only slowly eliminated by other mechanisms (1/3rd in 3 weeks), which did not impair the cell culture on a monthly scale. The hydrogel's microstructure and how the cells organize on this scaffold have been studied using electron and two-photon microscopies. The gel is made of a quite homogeneous network with a width of ≈180 nm and hundreds of micrometer long fibers, except at the surface where a dense mat of heterogeneous fibers is formed. We focused on methods able to colocalize the cells and the gel fibers. Many cell clusters have elongated and multidirectionnal shapes, guided by the fibers. Chains of single cells are also found following the fibers from one cluster to another. N-Nonyl-D-galactonamide fibers, which have the advantage of not being autofluorescent, do not mask the fluorescence of cells. But interestingly, they give a strong second harmonic generation (SHG) signal, due to their well-organized lamellar structure. We also made a special effort to visualize the penetration of cells within the depth of the hydrogels, in 3D, notably by sectioning the hydrogels, despite their softness. It was found that most of the cells stayed at the surface, but several cells grew within the supramolecular fiber network between 50 and 100 μm depth.

Self-healing, 3D printed bioinks from self-assembled peptide and alginate hybrid hydrogels

There is a pressing need for new cell-laden, printable, biomaterials that are rigid and highly biocompatible. These materials can mimic stiffer tissues such as cartilage, fibrotic tissue and cancer microenvironments, and thus have exciting applications in regenerative medicine, wound healing and cancer research. Self-assembled peptides (SAPs) functionalised with aromatic groups such as Fluorenyl-9-methoxycarbonyl (Fmoc) show promise as components of these biomaterials. However, the harsh basic conditions often used to solubilise SAPs leads to issues with toxicity and reproducibility. Here, we have designed a hybrid material comprised of self-assembled Fmoc-diphenylalanine (Fmoc-FF) assemblies dispersed throughout a sodium alginate matrix and investigated the influence of different organic solvents as peptide solubilising agents. Bioinks fabricated from peptides dissolved in 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) showed improved biocompatibility compared to those made from Dimethyl Sulfoxide (DMSO) peptide stocks, due to the increased volatility and reduced surface tension of HFIP, allowing for more efficient expulsion from the system. Through optimisation of assembly and solvent conditions we can generate hybrid bioinks with stiffnesses up to 8 times greater than sodium alginate alone that remain highly printable, even when laden with high concentrations of cells. In addition, the shear-thinning nature of the self-assembled peptide assemblies gave the hybrid bioinks highly desirable self-healing capabilities. Our developed hybrid materials allow the bioprinting of materials previously considered too stiff to extrude without causing shear induced cytotoxicity with applications in tissue engineering and biosensing.

Fmoc-conjugated dipeptide-based hydrogels and their pH-tuneable behaviour

In this work, we designed three dipeptide-based hydrogelators by attaching different hydrophilic amino acids (aspartic acid, glutamic acid, and glutamine) to Fmoc-conjugated phenylalanine. Self-assembly and gelation of the three dipeptides were studied in 50 mM phosphate buffer solutions. The gelation efficiency and kinetics of glutamine-based hydrogelators (FQ) were better than those of aspartic acid and glutamic acid-based hydrogelators FD and FE respectively at neutral pH. The lower gelation efficiency of FE and FD was due to the pH-responsive side chain (carboxylic acid) compared to FQ, where amide group was present as a side chain. Three hydrogelators exhibited better gelation efficiency at lower pHs as the anionic carboxylate group was protonated to the carboxylic group, facilitating better self-assembly and gelation processes. Thioflavin-T (ThT) binding study of hydrogels indicated the formation of β-sheet-like structure in the hydrogel state. The self-assembly process was inspected using molecular dynamic study, revealing that the newly developed FQ gelator possesses a higher aggregation tendency than FE and FD. Finally, these peptide-based injectable biomaterials were examined using fluorescence and FT-IR spectroscopy, scanning electron microscopy, and rheology.

Chimeric Antigen Receptor Cells Solid Tumor Immunotherapy Assisted by Biomaterials Tools

Chimeric antigen receptor (CAR) immune cell therapies have revolutionized oncology, particularly in hematological malignancies, yet their efficacy against solid tumors remains limited due to challenges such as dense stromal barriers and immunosuppressive microenvironments. With advancements in nanobiotechnology, researchers have developed various strategies and methods to enhance the CAR cell efficacy in solid tumor treatment. In this Review, we first outline the structure and mechanism of CAR-T (T, T cell), CAR-NK (NK, natural killer), and CAR-M (M, macrophage) cell therapies and deeply analyze the potential of these cells in the treatment of solid tumors and the challenges they face. Next, we explore how biomaterials can optimize these treatments by improving the tumor microenvironment, controlling CAR cell release, promoting cell infiltration, and enhancing efficacy. Finally, we summarize the current challenges and potential solutions, emphasize the effective combination of biomaterials and CAR cell therapy, and look forward to its future clinical application and treatment strategies. This Review provides important theoretical perspectives and practical guidance for the future development of more effective solid tumor treatment strategies.

Self-assembling Depsipeptides on Aggregation-Induced Emission Luminogens: A New Way to Create Programmable Nanovesicles and Soft Nanocarriers

We introduce the proof of concept of a new methodology to produce robust hollow nanovesicles stable in water or mixtures of water and organic solvents. The bottom-up produced nanovesicles are formed by the self-assembly of depsipeptide chains of natural origin combined with new aggregation-induced emission luminogens that function as constitutional vesicle-forming moieties and fluorescent indicators of the structure of the nanovesicle. The newly formed nanovesicles are robust enough to be used to carry large molecules such as physiological peptides without losing their structural characteristics, acting as programmable nanocarrier systems within living cells as Trojan horse systems, constituting a new approach to active transport and nanoencapsulation.

Trypsin-instructed bioactive peptide nanodrugs with cascading transformations to improve chemotherapy against colon cancer

Chemotherapy remains an effective treatment for colon cancer but is hampered by its limited response rate. Bioactive peptides, marked with intracellular transformations, have been reported as an effective approach to boosting chemotherapeutic activity. Herein, a promising trypsin-responsive bioactive peptide-based nanodrug is constructed, which could significantly prolong the drug retention time in vivo by cascading transformations and improve chemotherapeutic efficacy. Initially, 1-Pept co-assembles with Dox into a few nanofibers called 1-Pept/Dox NFs, inducing an enhanced cellular uptake via caveolae-mediated endocytosis by avoiding lysosomal degradation and further promoting perinuclear transportation, thus enlarging the drug efficacy in target areas. After nanofiber disassembly, the released 1-Pept converts into Pept under the catalysis of intracellular overexpressed trypsin, which then reassembles into denser Pept NFs, inducing a cascade of effects including disruption of the cytoskeleton, mitochondrial dysfunction, and activation of caspase-3. By the synergism of Pept NFs and Dox, caspase-3 can be further activated, and cause greater damage to nuclear, thereby leading to tumor ablation. As the first example of employing trypsin-mediated nanodrugs with cascading transformations to promote chemotherapeutic activity, this work promises a strategy for novel therapies for efficiently combating colon cancer.

Promoting Piezoelectricity in Amino Acids by Fluorination

Bioinspired piezoelectric amino acids and peptides are attracting attention due to their designable sequences, versatile structures, low cost, and biodegradability. However, it remains a challenge to design amino acids and peptides with high piezoelectricity. Herein, a high piezoelectric amino acid by simple fluorination in its side chain is presented. The three phenylalanine derivatives are designed: Cbz-Phe, Cbz-Phe(4F), and Cbz-pentafluoro-Phe. The effect of fluorination on self-assembly and piezoelectricity is investigated. Cbz-Phe(4F) can self-assemble into crystals with a C2 space group, while Cbz-Phe and Cbz-pentafluoro-Phe form aggregated self-assemblies. Moreover, Cbz-Phe(4F) crystals exhibit a remarkably higher piezoelectric coefficient (d 33 e f f $d_{\ 33}^{\ eff}$ ) of ≈17.9 pm V-1 than Cbz-Phe and Cbz-pentafluoro-Phe. When fabricated as a piezoelectric nanogenerator, it generates an open-circuit voltage of ≈2.4 V. Importantly, Cbz-Phe(4F) crystals serve as a flexible piezoelectric sensor for the classification of various nuts and their quality sorting, which includes those as small as individual pumpkin seeds with high sensitivity and accuracy of sorting and quality checks. When mounted onto soft grippers, the sensor performs the tactile self-sensing functions. This work provides a promising approach to designing high piezoelectric amino acids by simple fluorination, offering exciting prospects for advancements in bioinspired piezoelectric materials in the application of smart agriculture and soft robotics.

Peptide nanozymes: An emerging direction for functional enzyme mimics

The abundance of molecules on early Earth likely enabled a wide range of prebiotic chemistry, with peptides playing a key role in the development of early life forms and the evolution of metabolic pathways. Among peptides, those with enzyme-like activities occupy a unique position between peptides and enzymes, combining both structural flexibility and catalytic functionality. However, their full potential remains largely untapped. Further exploration of these enzyme-like peptides at the nanoscale could provide valuable insights into modern nanotechnology, biomedicine, and even the origins of life. Hence, this review introduces the groundbreaking concept of "peptide nanozymes (PepNzymes)", which includes single peptides exhibiting enzyme-like activities, peptide-based nanostructures with enzyme-like activities, and peptide-based nanozymes, thus enabling the investigation of biological phenomena at nanoscale dimensions. Through the rational design of enzyme-like peptides or their assembly with nanostructures and nanozymes, researchers have found or created PepNzymes capable of catalyzing a wide range of reactions. By scrutinizing the interactions between the structures and enzyme-like activities of PepNzymes, we have gained valuable insights into the underlying mechanisms governing enzyme-like activities. Generally, PepNzymes play a crucial role in biological processes by facilitating small-scale enzyme-like reactions, speeding up molecular oxidation-reduction, cleavage, and synthesis reactions, leveraging the functional properties of peptides, and creating a stable microenvironment, among other functions. These discoveries make PepNzymes useful for diagnostics, cellular imaging, antimicrobial therapy, tissue engineering, anti-tumor treatments, and more while pointing out opportunities. Overall, this research provides a significant journey of PepNzymes' potential in various biomedical applications, pushing them towards new advancements.

Morphology and Applications of Self-Assembled Peptide Nucleic Acids

Obtaining new materials by exploiting the self-assembly of biomolecules is a very challenging field. In recent years, short peptides and nucleic acids have been used as scaffolds to produce supramolecular structures for different applications in the biomedical and technological fields. In this review, we will focus on the self-assembly of peptide nucleic acids (PNAs), their conjugates with peptides, or other molecules. We will describe the physical properties of the assembled systems and, where described, the application they were designed for.

Synthetic Nanoassemblies for Regulating Organelles: From Molecular Design to Precision Therapeutics

Each organelle referring to a complex multiorder architecture executes respective biological processes via its distinct spatial organization and internal microenvironment. As the assembly of biomolecules is the structural basis of living cells, creating synthetic nanoassemblies with specific physicochemical and morphological properties in living cells to interfere or couple with the natural organelle architectures has attracted great attention in precision therapeutics of cancers. In this review, we give an overview of the latest advances in the synthetic nanoassemblies for precise organelle regulation, including the formation mechanisms, triggering strategies, and biomedical applications in precision therapeutics. We summarize the emerging material systems, including polymers, peptides, and deoxyribonucleic acids (DNAs), and their respective intermolecular interactions for intercellular synthetic nanoassemblies, and highlight their design principles in constructing precursors that assemble into synthetic nanoassemblies targeting specific organelles in the complex cellular environment. We further showcase the developed intracellular synthetic nanoassemblies targeting specific organelles including mitochondria, the endoplasmic reticulum, lysosome, Golgi apparatus, and nucleus and describe their underlying mechanisms for organelle regulation and precision therapeutics for cancer. Last, the essential challenges in this field and prospects for future precision therapeutics of synthetic nanoassemblies are discussed. This review should facilitate the rational design of organelle-targeting synthetic nanoassemblies and the comprehensive recognition of organelles by materials and contribute to the deep understanding and application of the synthetic nanoassemblies for precision therapeutics.

A Matter of Charge: Electrostatically Tuned Coassembly of Amphiphilic Peptides

Coassembly of peptide biomaterials offers a compelling avenue to broaden the spectrum of hierarchically ordered supramolecular nanoscale structures that may be relevant for biomedical and biotechnological applications. In this work coassemblies of amphiphilic and oppositely charged, anionic and cationic, β-sheet peptides are studied, which may give rise to a diverse range of coassembled forms. Mixtures of the peptides show significantly lower critical coassembly concentration (CCC) values compared to those of the individual pure peptides. Intriguingly, the highest formation of coassembled fibrils is found to require excess of the cationic peptide whereas equimolar mixtures of the peptides exhibited the maximum folding into β-sheet structures. Mixtures of the peptides coassembled sequentially from solutions at concentrations surpassing each peptide's intrinsic critical assembly concentration (CAC), are also found to require a higher portion of the cationic peptide to stabilize hydrogels. This study illuminates a systematic investigation of oppositely charged β-sheet peptides over a range of concentrations, in solutions and in hydrogels. The results may be relevant to the fundamental understanding of such intricate charge-driven assembly systems and to the formulation of peptide-based nanostructures with diverse functionalities.

Polypeptide-based multilayer nanoarchitectures: Controlled assembly on planar and colloidal substrates for biomedical applications

Polypeptides have shown an excellent potential in nanomedicine thanks to their biocompatibility, biodegradability, high functionality, and responsiveness to several stimuli. Polypeptides exhibit high propensity to organize at the supramolecular level; hence, they have been extensively considered as building blocks in the layer-by-layer (LbL) assembly. The LbL technique is a highly versatile methodology, which involves the sequential assembly of building blocks, mainly driven by electrostatic interactions, onto planar or colloidal templates to fabricate sophisticated multilayer nanoarchitectures. The simplicity and the mild conditions required in the LbL approach have led to the inclusion of biopolymers and bioactive molecules for the fabrication of a wide spectrum of biodegradable, biocompatible, and precisely engineered multilayer films for biomedical applications. This review focuses on those examples in which polypeptides have been used as building blocks of multilayer nanoarchitectures for tissue engineering and drug delivery applications, highlighting the characteristics of the polypeptides and the strategies adopted to increase the stability of the multilayer film. Cross-linking is presented as a powerful strategy to enhance the stability and stiffness of the multilayer network, which is a fundamental requirement for biomedical applications. For example, in tissue engineering, a stiff multilayer coating, the presence of adhesion promoters, and/or bioactive molecules boost the adhesion, growth, and differentiation of cells. On the contrary, antimicrobial coatings should repel and inhibit the growth of bacteria. In drug delivery applications, mainly focused on particles and capsules at the micro- and nano-meter scale, the stability of the multilayer film is crucial in terms of retention and controlled release of the payload. Recent advances have shown the key role of the polypeptides in the adsorption of genetic material with high loading efficiency, and in addressing different pathways of the particles/capsules during the intracellular uptake, paving the way for applications in personalized medicine. Although there are a few studies, the responsiveness of the polypeptides to the pH changes, together with the inclusion of stimuli-responsive entities into the multilayer network, represents a further key factor for the development of smart drug delivery systems to promote a sustained release of therapeutics. The degradability of polypeptides may be an obstacle in certain scenarios for the controlled intracellular release of a drug once an external stimulus is applied. Nowadays, the highly engineered design of biodegradable LbL particles/capsules is oriented on the development of theranostics that, limited to use of polypeptides, are still in their infancy.

Tailoring biomaterials for vaccine delivery

Biomaterials are substances that can be injected, implanted, or applied to the surface of tissues in biomedical applications and have the ability to interact with biological systems to initiate therapeutic responses. Biomaterial-based vaccine delivery systems possess robust packaging capabilities, enabling sustained and localized drug release at the target site. Throughout the vaccine delivery process, they can contribute to protecting, stabilizing, and guiding the immunogen while also serving as adjuvants to enhance vaccine efficacy. In this article, we provide a comprehensive review of the contributions of biomaterials to the advancement of vaccine development. We begin by categorizing biomaterial types and properties, detailing their reprocessing strategies, and exploring several common delivery systems, such as polymeric nanoparticles, lipid nanoparticles, hydrogels, and microneedles. Additionally, we investigated how the physicochemical properties and delivery routes of biomaterials influence immune responses. Notably, we delve into the design considerations of biomaterials as vaccine adjuvants, showcasing their application in vaccine development for cancer, acquired immunodeficiency syndrome, influenza, corona virus disease 2019 (COVID-19), tuberculosis, malaria, and hepatitis B. Throughout this review, we highlight successful instances where biomaterials have enhanced vaccine efficacy and discuss the limitations and future directions of biomaterials in vaccine delivery and immunotherapy. This review aims to offer researchers a comprehensive understanding of the application of biomaterials in vaccine development and stimulate further progress in related fields.

Self-Assembly of Polymers and Their Applications in the Fields of Biomedicine and Materials

Polymer self-assembly can prepare various shapes and sizes of pores, making it widely used. The complexity and diversity of biomolecules make them a unique class of building blocks for precise assembly. They are particularly suitable for the new generation of biomaterials integrated with life systems as they possess inherent characteristics such as accurate identification, self-organization, and adaptability. Therefore, many excellent methods developed have led to various practical results. At the same time, the development of advanced science and technology has also expanded the application scope of self-assembly of synthetic polymers. By utilizing this technology, materials with unique shapes and properties can be prepared and applied in the field of tissue engineering. Nanomaterials with transparent and conductive properties can be prepared and applied in fields such as electronic displays and smart glass. Multi-dimensional, controllable, and multi-level self-assembly between nanostructures has been achieved through quantitative control of polymer dosage and combination, chemical modification, and composite methods. Here, we list the classic applications of natural- and artificially synthesized polymer self-assembly in the fields of biomedicine and materials, introduce the cutting-edge technologies involved in these applications, and discuss in-depth the advantages, disadvantages, and future development directions of each type of polymer self-assembly.

Chemical Modifications in Hyaluronic Acid-Based Electrospun Scaffolds

Hyaluronic acid (HA) is a natural, non-sulfated glycosaminoglycan (GAG) present in ECM. It is involved in different biological functions with appealing properties in cosmetics and pharmaceutical preparations as well as in tissue engineering. Generally, HA has been electrospun in blends with natural or synthetic polymers to produce fibers having diameters in the order of nano and micro-scale whose pores can host cells able to regenerate damaged tissues. In the last decade, a rich literature on electrospun HA-based materials arose. Chemical modifications were generally introduced in HA scaffolds to favour crosslinking or conjugation with bioactive molecules. Considering the high solubility of HA in water, HA-based electrospun scaffolds are cross-linked to increase the stability in biological fluids. Crosslinking is necessary also to avoid the release of HA from the hybrid scaffold when implanted in-vivo. Furthermore, to endow the HA based scaffolds with new chemical or biological properties, conjugation of bioactive molecules to HA was widely reported. Herein, we review the existing research classifying chemical modifications on HA and HA-based electrospun fibers into three categories: i) in-situ crosslinking of electrospun HA-based scaffolds ii) off-site crosslinking of electrospun HA-based scaffolds; iii) conjugation of biofunctional molecules to HA with focus on peptides.

Small Peptide-Based Nanodelivery Systems for Cancer Therapy and Diagnosis

Developing nano-biomaterials with tunable topology, size, and surface characteristics has shown tremendously favorable benefits in various biologic and clinical applications. Among various nano-biomaterials, peptide-based drug delivery systems offer multiple merits over other synthetic systems due to their enhanced bio- and cytocompatibility and desirable biochemical and biophysical properties. Currently, around 100 peptide-based drugs are clinically available for numerous therapeutic purposes. In conjugation with chemotherapeutic moieties, peptides demonstrate a remarkable ability to reduce nonspecific drug effects by improving drug targetability at cancer sites. This review encompasses a wide-ranging role played by different peptide-based nanostructures in cancer theranostics. Section 1 introduces the rising concern about cancer as a disease and further describes peptide-based nanomaterials as biomedical agents to tackle the ailment. The subsequent section explores the mechanistic pathways behind the self-assembly of peptides to form hierarchically distinct assemblies. The crux of our review lies in an exhaustive exploration of the applications of various types of peptide-based nanostructures in cancer therapy and diagnosis. SIGNIFICANCE STATEMENT: Peptide-based drug delivery systems possess superior biocompatibility, biochemical, and biophysical properties compared to other synthetic alternatives. The development of these nano-biomaterials with customizable topology, size, and surface characteristics have shown promising outcomes in biomedical contexts. Peptides in conjunction with chemotherapeutic agents exhibit the ability to enhance drug targetability at cancer sites, reducing nonspecific drug effects. This comprehensive review emphasizes the pivotal role of diverse peptide-based nanostructures as cancer theranostics, elucidating their potential in revolutionizing cancer therapy and diagnosis.

Design and Function of α-Helix-Rich, Heme-Binding Peptide Materials

Peptide materials often employ short peptides that self-assemble into unique nanoscale architectures and have been employed across many fields relevant to medicine and energy. A majority of peptide materials are high in β-sheet, secondary structure content, including heme-binding peptide materials. To broaden the structural diversity of heme-binding peptide materials, a small series of peptides were synthesized to explore the design criteria required for (1) folding into an α-helix structure, (2) assembling into a nanoscale material, (3) binding heme, and (4) demonstrating functions similar to that of heme proteins. One peptide was identified to meet all four criteria, including the heme protein function of CO binding and its microsecond-to-millisecond recombination rates, as measured by transient absorption spectroscopy. Implications of new design criteria and peptide material function through heme incorporation are discussed.

Conformation Controlled Hydrogelation of Minimalistic α, γ Hybrid Peptide

A majority of short peptide (≤7 amino acids) hydrogels are primarily assembled via cross β-structure formation. In contrast to the natural trend, herein, we report the formation of supramolecular hydrogel from the ultrashort hybrid folded peptide composed of canonical α-amino acid and noncanonical γ-amino acid, Fmoc-γPhe-Phe-OH. The designed hybrid peptide hydrogel is composed of entangled fibers, has viscoelastic properties, exhibits proteolytic stability, and exhibits cytocompatibility with L929 fibroblast cells. Mutating the peptide sequence by altering the position of γPhe from the N-termini to C-termini transforms the self-assembly into crystalline aggregates. Combining FTIR, 2D NMR, and DFT calculations revealed that the hydrogel-forming peptide adopts a C9 H-bonded conformation, resembling the well-known γ-turn. However, the isomeric hybrid peptide adopts an extended structure. The present study highlights the importance of secondary structure in the higher order assembly of minimalist hybrid peptides and broadens the range of secondary structures to design short peptide-based hydrogels.

Harnessing the Potential of Self-Assembled Peptide Hydrogels for Neural Regeneration and Tissue Engineering

Spinal cord injury, traumatic brain injury, and neurosurgery procedures usually lead to neural tissue damage. Self-assembled peptide (SAP) hydrogels, a type of innovative hierarchical nanofiber-forming peptide sequences serving as hydrogelators, have emerged as a promising solution for repairing tissue defects and promoting neural tissue regeneration. SAPs possess numerous features, such as adaptable morphologies, biocompatibility, injectability, tunable mechanical stability, and mimicking of the native extracellular matrix. This review explores the capacity of neural cell regeneration and examines the critical aspects of SAPs in neuroregeneration, including their biochemical composition, topology, mechanical behavior, conductivity, and degradability. Additionally, it delves into the latest strategies involving SAPs for central or peripheral neural tissue engineering. Finally, the prospects of SAP hydrogel design and development in the realm of neuroregeneration are discussed.

Advances of biological macromolecules hemostatic materials: A review

Achieving hemostasis is a necessary intervention to rapidly and effectively control bleeding. Conventional hemostatic materials currently used in clinical practice may aggravate the damage at the bleeding site due to factors such as poor adhesion and poor adaptation. Compared to most traditional hemostatic materials, polymer-based hemostatic materials have better biocompatibility and offer several advantages. They provide a more effective method of stopping bleeding and avoiding additional damage to the body in case of excessive blood loss. Various hemostatic materials with greater functionality have been developed in recent years for different organs using diverse design strategies. This article reviews the latest advances in the development of polymeric hemostatic materials. We introduce the coagulation cascade reaction after bleeding and then discuss the hemostatic mechanisms and advantages and disadvantages of various polymer materials, including natural, synthetic, and composite polymer hemostatic materials. We further focus on the design strategies, properties, and characterization of hemostatic materials, along with their applications in different organs. Finally, challenges and prospects for the application of hemostatic polymeric materials are summarized and discussed. We believe that this review can provide a reference for related research on hemostatic materials, contributing to the further development of polymer hemostatic materials.

Asymmetric synthesis of unnatural α-amino acids through photoredox-mediated C-O bond activation of aliphatic alcohols

Unnatural α-amino acids constitute a fundamental class of biologically relevant compounds. However, despite the interest in these motifs, synthetic strategies have traditionally employed polar retrosynthetic disconnections. These methods typically entail the use of stoichiometric amounts of toxic and highly sensitive reagents, thereby limiting the substrate scope and practicality for scale up. In this work, an efficient protocol for the asymmetric synthesis of unnatural α-amino acids is realized through photoredox-mediated C-O bond activation in oxalate esters of aliphatic alcohols as radical precursors. The developed system uses a chiral glyoxylate-derived N-sulfinyl imine as the radical acceptor and allows facile access to a range of functionalized unnatural α-amino acids through an atom-economical redox-neutral process with CO2 as the only stoichiometric byproduct.

Construction of Reconfigurable and Polymorphic DNA Origami Assemblies with Coiled-Coil Patches and Patterns

DNA origami nanodevices achieve programmable structure and tunable mechanical and dynamic properties by leveraging the sequence-specific interactions of nucleic acids. Previous advances have also established DNA origami as a useful building block to make well-defined micron-scale structures through hierarchical self-assembly, but these efforts have largely leveraged the structural features of DNA origami. The tunable dynamic and mechanical properties also provide an opportunity to make assemblies with adaptive structures and properties. Here the integration of DNA origami hinge nanodevices and coiled-coil peptides are reported into hybrid reconfigurable assemblies. With the same dynamic device and peptide interaction, it is made multiple higher-order assemblies (i.e., polymorphic assembly) by organizing clusters of peptides into patches or arranging single peptides into patterns on the surfaces of DNA origami to control the relative orientation of devices. The coiled-coil interactions are used to construct circular and linear assemblies whose structure and mechanical properties can be modulated with DNA-based reconfiguration. Reconfiguration of linear assemblies leads to micron scale motions and ≈2.5-10-fold increase in bending stiffness. The results provide a foundation for stimulus-responsive hybrid assemblies that can adapt their structure and properties in response to nucleic acid, peptide, protein, or other triggers.

Amyloids, amorphous aggregates and assemblies of peptides - Assessing aggregation

Amyloid and amorphous aggregates represent the two major categories of aggregates associated with diseases, and although exhibiting distinct features, researchers often treat them as equivalent, which demonstrates the need for more thorough characterization. Here, we compare amyloid and amorphous aggregates based on their biochemical properties, kinetics, and morphological features. To further decipher this issue, we propose the use of peptide self-assemblies as minimalistic models for understanding the aggregation process. Peptide building blocks are significantly smaller than proteins that participate in aggregation, however, they make a plausible means to bridge the gap in discerning the aggregation process at the more complex, protein level. Additionally, we explore the potential use of peptide-inspired models to research the liquid-liquid phase separation as a feasible mechanism preceding amyloid formation. Connecting these concepts can help clarify our understanding of aggregation-related disorders and potentially provide novel drug targets to impede and reverse these serious illnesses.

Peptide-based self-assembled monolayers (SAMs): what peptides can do for SAMs and vice versa

Self-assembled monolayers (SAMs) represent highly ordered molecular materials with versatile biochemical features and multidisciplinary applications. Research on SAMs has made much progress since the early begginings of Au substrates and alkanethiols, and numerous examples of peptide-displaying SAMs can be found in the literature. Peptides, presenting increasing structural complexity, stimuli-responsiveness, and biological relevance, represent versatile functional components in SAMs-based platforms. This review examines the major findings and progress made on the use of peptide building blocks displayed as part of SAMs with specific functions, such as selective cell adhesion, migration and differentiation, biomolecular binding, advanced biosensing, molecular electronics, antimicrobial, osteointegrative and antifouling surfaces, among others. Peptide selection and design, functionalisation strategies, as well as structural and functional characteristics from selected examples are discussed. Additionally, advanced fabrication methods for dynamic peptide spatiotemporal presentation are presented, as well as a number of characterisation techniques. All together, these features and approaches enable the preparation and use of increasingly complex peptide-based SAMs to mimic and study biological processes, and provide convergent platforms for high throughput screening discovery and validation of promising therapeutics and technologies.

Exploring a Solvent Dependent Strategy to Control Self-Assembling Behavior and Cellular Interaction in Laminin-Mimetic Short Peptide based Supramolecular Hydrogels

Self-assembled hydrogels, fabricated through diverse non-covalent interactions, have been extensively studied in regenerative medicines. Inspired from bioactive functional motifs of ECM protein, short peptide sequences have shown remarkable abilities to replicate the intrinsic features of the natural extracellular milieu. In this direction, we have fabricated two short hydrophobic bioactive sequences derived from the laminin protein i. e., IKVAV and YIGSR. Based on the substantial hydrophobicity of these peptides, we selected a co-solvent approach as a suitable gelation technique that included different concentrations of DMSO as an organic phase along with an aqueous solution containing 0.1 % TFA. These hydrophobic laminin-based bioactive peptides with limited solubility in aqueous physiological environment showed significantly enhanced solubility with higher DMSO content in water. The enhanced solubility resulted in extensive intermolecular interactions that led to the formation of hydrogels with a higher-order entangled network along with improved mechanical properties. Interestingly, by simply modulating DMSO content, highly tunable gels were accessed in the same gelator domain that displayed differential physicochemical properties. Further, the cellular studies substantiated the potential of these laminin-derived hydrogels in enhancing cell-matrix interactions, thereby reinforcing their applications in tissue engineering.

Designing Multifunctional Biomaterials via Protein Self-Assembly

Protein self-assembly is a fundamental biological process where proteins spontaneously organize into complex and functional structures without external direction. This process is crucial for the formation of various biological functionalities. However, when protein self-assembly fails, it can trigger the development of multiple disorders, thus making understanding this phenomenon extremely important. Up until recently, protein self-assembly has been solely linked either to biological function or malfunction; however, in the past decade or two it has also been found to hold promising potential as an alternative route for fabricating materials for biomedical applications. It is therefore necessary and timely to summarize the key aspects of protein self-assembly: how the protein structure and self-assembly conditions (chemical environments, kinetics, and the physicochemical characteristics of protein complexes) can be utilized to design biomaterials. This minireview focuses on the basic concepts of forming supramolecular structures, and the existing routes for modifications. We then compare the applicability of different approaches, including compartmentalization and self-assembly monitoring. Finally, based on the cutting-edge progress made during the last years, we summarize the current knowledge about tailoring a final function by introducing changes in self-assembly and link it to biomaterials' performance.

Self-assembly of amphiphilic helical-coiled peptide nanofibers and inhibition of fibril formation with curcumin

Amphiphilic peptide sequences are conducive to secondary structures that self-assemble into higher-ordered peptide nanostructures. A select set of amphiphilic polycationic peptides displayed stable helical-coiled structures that self-assembled into peptide nanofibers. The progression of peptide fibril formation revealed short protofibrils that extended into thin filaments and into an entangled network of nanofibers over an extended (5 days) incubation period. Ligand binding with 8-anilinonaphthalene-1-sulfonic acid (ANS) and Congo Red (CR) confirmed the amphiphilic helical-coiled peptide structure assembly into nanofibers, whereas curcumin treatment led to inhibition of fibril formation. Considering the vast repertoire of fibrous biomaterials and peptide or protein (mis)folding contingent on fibril formation, this work relates the molecular interplay in between sequence composition, structural folding and the ligand binding events impacting peptide self-assembly into nanofibers.

Zinc-Induced Luminescent l-Valine-Based Pseudopeptidic Soft Bioinspired Materials for Precise Tuning of Nanoassembly

Pseudopeptide-based bioinspired materials are emerging for selective recognition of biologically significant analytes and are applicable in the modern nanoscience field. Therefore, we have developed novel multifunctional C2-symmetric soft pseudopeptides by amino acid l-valine and salicylaldehyde fragments using a series of aliphatic linkers. They are highly selective and sensitive to Zn (II) ions under physiological conditions and reveal significant fluorescence enhancement with the PET mechanism. The molecular self-assembly shows zinc-induced morphological transformation of the rod-shaped assembly into a chain-like morphology. Such a metal-induced hierarchical nano-assembly may have relevance for specific nanobiotechnology applications.

Stimuli-responsive peptide hydrogels for biomedical applications

Stimuli-responsive hydrogels can respond to external stimuli with a change in the network structure and thus have potential application in drug release, intelligent sensing, and scaffold construction. Peptides possess robust supramolecular self-assembly ability, enabling spontaneous formation of nanostructures through supramolecular interactions and subsequently hydrogels. Therefore, peptide-based stimuli-responsive hydrogels have been widely explored as smart soft materials for biomedical applications in the last decade. Herein, we present a review article on design strategies and research progress of peptide hydrogels as stimuli-responsive materials in the field of biomedicine. The latest design and development of peptide hydrogels with responsive behaviors to stimuli are first presented. The following part provides a systematic overview of the functions and applications of stimuli-responsive peptide hydrogels in tissue engineering, drug delivery, wound healing, antimicrobial treatment, 3D cell culture, biosensors, etc. Finally, the remaining challenges and future prospects of stimuli-responsive peptide hydrogels are proposed. It is believed that this review will contribute to the rational design and development of stimuli-responsive peptide hydrogels toward biomedical applications.

A self-standing superhydrophobic material formed by the self-assembly of an individual amino acid

HYPOTHESIS

There is a growing interest in designing superhydrophobic materials for many applications including self-clean surfaces, separation systems, and antifouling solutions. Peptides and amino acids offer attractive building blocks for these materials since they are biocompatible and biodegradable and can self-assemble into complex ordered structures.

EXPERIMENTS AND SIMULATIONS

We designed a self-standing superhydrophobic material through the self-assembly of an individual functionalized aromatic amino acid, Cbz-Phe(4F). The self-assembly of Cbz-Phe(4F) was investigated by experimental and computational methods. Moreover, when drop-casted three times on a solid support, it formed a self-standing superhydrophobic material. The mechanical properties and chemical stability of this self-standing superhydrophobic material were demonstrated.

FINDINGS

The designed Cbz-Phe(4F) self-assembled into fibrous structures in solution. Molecular dynamics (MD) simulations revealed that the fibrous backbone of Cbz-Phe(4F) aggregations was stabilized through hydrogen bonds, whereas the isotropic growth of the aggregates was driven by hydrophobic interactions. Importantly, when drop-casted three times on a solid support, it formed a self-standing superhydrophobic material. Moreover, this material had a high mechanical strength, with a Young's modulus of 53 GPa, resistance to enzymatic degradation, and thermal stability up to 200 ℃. This study provides a simple strategy to generate smart and functional materials by the simple self-assembly of functional individual amino acids.

Bioinspired Amino Acid Based Materials in Bionanotechnology: From Minimalistic Building Blocks and Assembly Mechanism to Applications

Inspired by natural hierarchical self-assembly of proteins and peptides, amino acids, as the basic building units, have been shown to self-assemble to form highly ordered structures through supramolecular interactions. The fabrication of functional biomaterials comprised of extremely simple biomolecules has gained increasing interest due to the advantages of biocompatibility, easy functionalization, and structural modularity. In particular, amino acid based assemblies have shown attractive physical characteristics for various bionanotechnology applications. Herein, we propose a review paper to summarize the design strategies as well as research advances of amino acid based supramolecular assemblies as smart functional materials. We first briefly introduce bioinspired reductionist design strategies and assembly mechanism for amino acid based molecular assembly materials through noncovalent interactions in condensed states, including self-assembly, metal ion mediated coordination assembly, and coassembly. In the following part, we provide an overview of the properties and functions of amino acid based materials toward applications in nanotechnology and biomedicine. Finally, we give an overview of the remaining challenges and future perspectives on the fabrication of amino acid based supramolecular biomaterials with desired properties. We believe that this review will promote the prosperous development of innovative bioinspired functional materials formed by minimalistic building blocks.

Photoresponsive peptide materials: Spatiotemporal control of self-assembly and biological functions

Peptides work as both functional molecules to modulate various biological phenomena and self-assembling artificial materials. The introduction of photoresponsive units to peptides allows the spatiotemporal remote control of their structure and function upon light irradiation. This article overviews the photoresponsive peptide design, interaction with biomolecules, and applications in self-assembling materials over the last 30 years. Peptides modified with photochromic (photoisomerizable) molecules, such as azobenzene and spiropyran, reversibly photo-controlled the binding to biomolecules and nanostructure formation through self-assembly. Photocleavable molecular units irreversibly control the functions of peptides through cleavage of the main chain and deprotection by light. Photocrosslinking between peptides or between peptides and other biomolecules enhances the structural stability of peptide assemblies and complexes. These photoresponsive peptides spatiotemporally controlled the formation and dissociation of peptide assemblies, gene expressions, protein-drug interactions, protein-protein interactions, liposome deformation and motility, cytoskeleton structure and stability, and cell functions by appropriate light irradiation. These molecular systems can be applied to photo-control biological functions, molecular robots, artificial cells, and next-generation smart drug delivery materials.

Simvastatin-Releasing Nanofibrous Peptide Hydrogels for Accelerated Healing of Diabetic Wounds

Wound healing is one of the major global health concerns in diabetic patients. Simvastatin (SMV) is a poorly soluble oral cholesterol-lowering drug that may aid diabetic wound healing. In the current study, a thixotropic peptide hydrogel of Fmoc-diphenylalanine (FmocFF) containing SMV was designed to accelerate skin wound healing effectively and safely in diabetic mice. FmocFF hydrogels were prepared at various concentrations by using the solvent-triggering technique and characterized by spectroscopic methods such as attenuated total reflection Fourier transform infrared (FT-IR) spectroscopy and fluorimetry. Mechanical behaviors were explored by oscillatory rheology. In model mice, the regenerative potential of the FmocFF-SMV hydrogel was evaluated in terms of wound contraction and closure, tissue regeneration, acute and chronic inflammation, granulation, and re-epithelization. The results showed that FmocFF-SMV hydrogels had an entangled nanofibrous microstructure and shear-thinning characteristics. FmocFF-SMV demonstrated a sustained drug release over 7 days. Compared to the unloaded FmocFF hydrogel, treatment with FmocFF-SMV led to superior diabetic wound recovery and reduced inflammation. Therefore, the utilization of the sustained-release FmocFF-SMV hydrogel formulation could become an attractive choice for topical wound therapy in diabetes patients.

An Overview of Supramolecular Platforms Boosting Drug Delivery

Numerous supramolecular platforms inspired by natural self-assembly are exploited as drug delivery systems. The spontaneous arrangement of single building blocks into inorganic and organic structures is determined and controlled by noncovalent forces such as electrostatic interactions, π-π interactions, hydrogen bonds, and van der Waals interactions. This review describes the main structures and characteristics of several building blocks used to obtain stable, self-assembling nanostructures tailored for numerous biological applications. Owing to their versatility, biocompatibility, and controllability, these nanostructures find application in diverse fields ranging from drug/gene delivery, theranostics, tissue engineering, and nanoelectronics. Herein, we described the different approaches used to design and functionalize these nanomaterials to obtain selective drug delivery in a specific disease. In particular, the review highlights the efficiency of these supramolecular structures in applications related to infectious diseases and cancer.

Construction of a novel amphiphilic peptide paclitaxel rod micelle: Demonstrating that the nano-delivery system shape can affect the cellular uptake efficiency of paclitaxel and improve the therapeutic efficacy for breast cancer

Recent studies have shown that the morphology of nano-delivery systems has become a key factor affecting their anti-tumor effects. Although it has been demonstrated that rod-like nanoparticles are more easily absorbed by tumor cells, the application of rod-like nanoparticles is still limited by the lack of safe vector in vivo. In this study, a biocompatible amphiphilic peptide (IIQQQQ, I2Q4), was designed to form rod-like micelles. The key forces of the self-assembly mechanism were investigated. Driven by hydrogen bonds, the hydrophilic segment of the peptide formed a β-sheet structure, and the molecules accumulated and extended along the side chain direction to form a rod-like structure. Using paclitaxel (PTX) as the model drug, a PTX rod-like nano-drug delivery system, PTX@I2Q4, was constructed. PTX exists in a randomly coiled state in the hydrophobic cavity formed by the peptide. Compared to PTX and spherical PTX albumin nanoparticles, PTX@I2Q4 showed higher entry efficiency and better antitumor effects in vivo and in vitro. This was mainly because PTX@I2Q4 not only allowed more efficient entry into cells via macro-pinocytosis, but also significantly prolonged the t1/2 of PTX. The results confirmed the feasibility of regulating the morphology of nanoparticles to improve the efficacy of PTX and provide a reference for further research on the influence of the morphology of the nano-drug delivery system on the efficacy of antitumor effects.

Construction and reconfiguration of dynamic DNA origami assemblies with coiled-coil patches and patterns

DNA origami nanodevices achieve programmable structure and tunable mechanical and dynamic properties by leveraging the sequence specific interactions of nucleic acids. Previous advances have also established DNA origami as a useful building block to make well-defined micron-scale structures through hierarchical self-assembly, but these efforts have largely leveraged the structural features of DNA origami. The tunable dynamic and mechanical properties also provide an opportunity to make assemblies with adaptive structure and properties. Here we report the integration of DNA origami hinge nanodevices and coiled-coil peptides into hybrid reconfigurable assemblies. With the same dynamic device and peptide interaction, we make multiple higher order assemblies by organizing clusters of peptides (i.e. patches) or arranging single peptides (i.e. patterns) on the surfaces of DNA origami to control the relative orientation of devices. We use coiled-coil interactions to construct circular and linear assemblies whose structure and mechanical properties can be modulated with DNA-based actuation. Actuation of linear assemblies leads to micron scale motions and ~2.5-10-fold increase in bending stiffness. Our results provide a foundation for stimulus responsive hybrid assemblies that can adapt their structure and properties in response to nucleic acid, peptide, protein, or other triggers.

Control of charge transport in electronically active systems towards integrated biomolecular circuits (IbC)

The miniaturization of traditional silicon-based electronics will soon reach its limitation as quantum tunneling and heat become serious problems at the several-nanometer scale. Crafting integrated circuits via self-assembly of electronically active molecules using a "bottom-up" paradigm provides a potential solution to these technological challenges. In particular, integrated biomolecular circuits (IbC) offer promising advantages to achieve this goal, as nature offers countless examples of functionalities entailed by self-assembly and examples of controlling charge transport at the molecular level within the self-assembled structures. To this end, the review summarizes the progress in understanding how charge transport is regulated in biosystems and the key redox-active amino acids that enable the charge transport. In addition, charge transport mechanisms at different length scales are also reviewed, offering key insights for controlling charge transport in IbC in the future.

Perspectives on recent advancements in energy harvesting, sensing and bio-medical applications of piezoelectric gels

The development of next-generation bioelectronics, as well as the powering of consumer and medical devices, require power sources that are soft, flexible, extensible, and even biocompatible. Traditional energy storage devices (typically, batteries and supercapacitors) are rigid, unrecyclable, offer short-lifetime, contain hazardous chemicals and possess poor biocompatibility, hindering their utilization in wearable electronics. Therefore, there is a genuine unmet need for a new generation of innovative energy-harvesting materials that are soft, flexible, bio-compatible, and bio-degradable. Piezoelectric gels or PiezoGels are a smart crystalline form of gels with polar ordered structures that belongs to the broader family of piezoelectric material, which generate electricity in response to mechanical stress or deformation. Given that PiezoGels are structurally similar to hydrogels, they offer several advantages including intrinsic chirality, crystallinity, degree of ordered structures, mechanical flexibility, biocompatibility, and biodegradability, emphasizing their potential applications ranging from power generation to bio-medical applications. Herein, we describe recent examples of new functional PiezoGel materials employed for energy harvesting, sensing, and wound dressing applications. First, this review focuses on the principles of piezoelectric generators (PEGs) and the advantages of using hydrogels as PiezoGels in energy and biomedical applications. Next, we provide a detailed discussion on the preparation, functionalization, and fabrication of PiezoGel-PEGs (P-PEGs) for the applications of energy harvesting, sensing and wound healing/dressing. Finally, this review concludes with a discussion of the current challenges and future directions of P-PEGs.

Advancements in Biosensors Based on the Assembles of Small Organic Molecules and Peptides

Over the past few decades, molecular self-assembly has witnessed tremendous progress in a variety of biosensing and biomedical applications. In particular, self-assembled nanostructures of small organic molecules and peptides with intriguing characteristics (e.g., structure tailoring, facile processability, and excellent biocompatibility) have shown outstanding potential in the development of various biosensors. In this review, we introduced the unique properties of self-assembled nanostructures with small organic molecules and peptides for biosensing applications. We first discussed the applications of such nanostructures in electrochemical biosensors as electrode supports for enzymes and cells and as signal labels with a large number of electroactive units for signal amplification. Secondly, the utilization of fluorescent nanomaterials by self-assembled dyes or peptides was introduced. Thereinto, typical examples based on target-responsive aggregation-induced emission and decomposition-induced fluorescent enhancement were discussed. Finally, the applications of self-assembled nanomaterials in the colorimetric assays were summarized. We also briefly addressed the challenges and future prospects of biosensors based on self-assembled nanostructures.

Peptide Self-Assembled Nanocarriers for Cancer Drug Delivery

The design of novel cancer drug nanocarriers is critical in the framework of cancer therapeutics. Nanomaterials are gaining increased interest as cancer drug delivery systems. Self-assembling peptides constitute an emerging novel class of highly attractive nanomaterials with highly promising applications in drug delivery, as they can be used to facilitate drug release and/or stability while reducing side effects. Here, we provide a perspective on peptide self-assembled nanocarriers for cancer drug delivery and highlight the aspects of metal coordination, structure stabilization, and cyclization, as well as minimalism. We review particular challenges in nanomedicine design criteria and, finally, provide future perspectives on addressing a portion of the challenges via self-assembling peptide systems. We consider that the intrinsic advantages of such systems, along with the increasing progress in computational and experimental approaches for their study and design, could possibly lead to novel classes of single or multicomponent systems incorporating such materials for cancer drug delivery.