Tyrosine-Rich Peptides as a Platform for Assembly and Material Synthesis

Hierarchical protein nano-crystalline hydrogel with extracellular vesicles for ectopic lymphoid structure formation

Among cancer therapies, immune checkpoint blockade (ICB) has emerged as a prominent approach, substantially enhancing anti-tumor immune responses. However, the efficacy of ICB is often limited in the absence of a pre-existing immune response within the tumor microenvironment. Here, we introduce a novel hierarchical protein hydrogel platform designed to facilitate the formation of artificial tertiary lymphoid structures (aTLS), thereby improving ICB efficacy. Through the integration of self-assembling ferritin protein nanocages, rec1-resilin protein, and CP05 peptide, our hierarchical hydrogels provide a structurally supportive and functionally adaptive scaffold capable of on-demand self-repair in response to mild thermal treatments. The effective encapsulation of extracellular vesicles (EVs) via the CP05 peptide ensures the formation of aTLS with germinal center-like structures within the hierarchical hydrogel. We demonstrate that, combined with ICB therapy, EV-loaded hierarchical hydrogels also induce the TLS within the tumor, markedly promoting immune responses against ICB-resistant tumor. This bioactive hydrogel platform offers a versatile tool for enhancing a broad range of immunotherapies, with potential applications extending beyond TLS to other frameworks that support complex tissue architectures.

Effect of Tyrosine-Containing Self-Assembling β-Sheet Peptides on Macrophage Polarization and Inflammatory Response

Self-assembling peptides (SAPs) are fully defined nanobiomaterials offering unprecedented opportunities to control nanostructure and chemical attributes to investigate and manipulate cellular signals. To investigate the influence of chemical and morphological characteristics on inflammatory signaling in native immunity, we designed five β-sheet SAPs: EFEFKFEFK (EF8), YEFEFKFEFK (YEF8), EFEFKFEFKY (EF8Y), YEFEFKFEFKY (YEF8Y), and EYEFKFEFK (EYF8) (F: phenylalanine; E: glutamic acid; K: lysine, Y: tyrosine). The position of tyrosine in the peptide sequence dictated the self-assembly into nanostructures, with all SAPs self-assembling into thin constituent nanofibers with d ≈ 3.8 ± 0.4 nm, and sequences YEF8 and EF8 showing a propensity for associative bundling. These distinct SAPs induced contrasting inflammatory responses of monocytic model THP-1 cells-derived macrophages (MΦs). Presence of soluble EF8 nanofibers (at 2 mM) induced an anti-inflammatory response and polarization toward an M2 state, whereas YEF8 (at 2 mM) displayed a tendency for inducing a pro-inflammatory response and polarization toward an M1 state. EF8Y, YEF8Y, and EYF8 SAPs did not induce an inflammatory response in our models. These results were validated using peripheral blood mononuclear cells (PBMCs)-derived MΦs from human donors, confirming the critical role of EF8 and YEF8 SAPs as possible orchestrators of the repair of tissues or inducers of pro-inflammatory state, respectively. The same MΦs polarization responses from THP-1-derived MΦs cultured on 20 mM hydrogels were obtained. These findings will facilitate the utilization of this family of SAPs as immunomodulatory nanobiomaterials potentially changing the course of inflammation during the progression of various diseases.

Self-assembly of Tyrosine Scaffolds in Aqueous Media: Complex Molecular Architectures from Simple Building Blocks

Mimicking natural systems, self-assembly has been employed for constructing highly stable and well-ordered supramolecular structures. Amino acids are frequently used as building blocks in the self-assembly process due to their advantageous characteristics including easy availability, easy functionalization, tunable mechanical property, and biodegradability. In situ generation of active building blocks to obtain complex materials via self-assembly has enhanced their application in biomedical fields including bio-imaging, therapeutics. Single amino acid as the small building-block can provide artificial supramolecular materials with unique properties. In this review, we summarize the self-assembly of tyrosine-derivatives as single amino acid-based building blocks providing supramolecular assemblies and provide perspectives on their potential impact. Finally, we discuss the ongoing challenges for future research.

Autonomous Bioelectronic Devices Based on Silk Fibroin

The development of autonomous bioelectronic devices capable of dynamically adapting to changing biological environments represents a significant advancement in healthcare and wearable technologies. Such systems draw inspiration from the precision, adaptability, and self-regulation of biological processes, requiring materials with intrinsic versatility and seamless bio-integration to ensure biocompatibility and functionality over time. Silk fibroin (SF) derived from Bombyx mori cocoons, has emerged as an ideal biomaterial with a unique combination of biocompatibility, mechanical flexibility, and tunable biodegradability. Adding autonomous features into SF, including self-healing, shape-morphing, and controllable degradation, enables dynamic interactions with living tissues while minimizing immune responses and mechanical mismatches. Additionally, structural tunability and environmental sustainability of SF further reinforce its potential as a platform for adaptive implants, epidermal electronics, and intelligent textiles. This review explores recent progress in understanding the structure-property relationships of SF, its modification strategies, and its great potential for integration into advanced autonomous bioelectronic systems while addressing challenges related to scalability, reproducibility, and multifunctionality. Future opportunities, such as AI-assisted material design, scalable fabrication techniques, and the incorporation of wireless and personalized technologies, are also discussed, positioning SF as a key material in bridging the gap between biological systems and artificial technologies.

Assessment of Phage-Displayed Peptides Targeting Cancer Cell Surface Proteins: A Comprehensive Molecular Docking Study

Peptides binding overexpressed breast and cervical cancer cell surface proteins can be isolated by phage display technology, and their affinity to their potential receptors can be assessed by molecular docking. We isolated 44 phage clones displaying dodecapeptides with high affinity to HeLa cervical cancer and MDA-MB-231 (MDA) breast cancer cells by repeated biopanning of an MK13 phage library and explored their affinity to specific proteins by molecular docking. Six peptides appeared repeatedly during biopanning: two with affinity to HeLa (H5/H21), and four with affinity to MDA cells (M3/M7/M15/M17). Peptide pairs M3/H5 and H1/M17 had affinity to both cell lines. A systematic review identified Annexin A2, EGFR, CD44, CD146, and Integrin alpha V as potential protein targets in HeLa cells, and Vimentin, Galectin-1, and Annexins A1 and A5 in MDA cells. Via virtual screening, we selected six peptides with the highest total docking scores: H1 (-916.32), H6 (-979.21), H19 (-1093.24), M6 (-732.21), M16 (-745.5), and M19 (-739.64), and identified that docking scores were strengthened by the protein type, the interacting amino acid side chains, and the polarity of peptides. This approach facilitates the selection of relevant peptides that could be further explored for active targeting in cancer diagnosis and treatment.

Harnessing Amino Acid Modularity for Programmable Function in Covalent Peptide Assemblies

Covalent peptide assembly leverages robust covalent bonds and dynamic non-covalent interactions to provide enhanced stability and introduce diverse functionalities. Nevertheless, it remains significantly challenging to achieve modular control over the structural diversity and functional complexity while elucidating how specific amino acid sequences contribute to these processes. Here, the systematic encoding of peptide derivative characteristics is demonstrated through amino acid modularity to enable precise control over both the structural diversity and functional complexity in covalent peptide assemblies. By systematically screening single amino acid substitutions in pentapeptides using tyrosine crosslinking, a diverse library of peptide constructs is developed. Each construct is tailored to exhibit distinct properties, including charge repulsion, aggregation-induced quenching, disassembly behavior, and redox responsiveness. The strategic manipulation of sequence composition, both in individual assemblies and combinatorial systems, enables programmable control over the structural diversity and functional complexity. This approach yields various module-specific functions, including frustrated growth, hierarchical hollow architecture formation, affinity enrichment, stimuli-responsive behavior, and fluorescence signal amplification. This work establishes a framework for the design of modular peptide materials with programmable functionalities, advancing the development of next-generation multicomponent peptide assembly technologies characterized by unprecedented complexity and adaptability.

Harnessing Mn2+ Ions and Antitumor Peptides: A Robust Hydrogel for Enhanced Tumor Immunotherapy

Immunotherapy has attracted widespread attention because of its durable and effective antitumor properties. However, systemic delivery strategies often result in immune-related off-target toxicity effects and inadequate drug retention at the tumor site, which limits its broader application. In this research, we designed a dual-functional antitumor peptide (N-Pep) that serves as both a therapeutic agent and metal ions (Mn2+) immunomodulator carrier. The rational designed antitumor peptide self-assembles into a hydrogel through coordination with Mn2+ ions (referred to as N-Pep-Mn gel). The multiporous hydrogel network allows for efficient loading of antiprogrammed death-1 antibody (αPD-1). The hydrogel served as a depot for the sustained release of Mn2+ ions and encapsulated αPD-1, effectively activating dendritic cells, polarizing tumor-associated macrophages and enhancing effector T cell infiltration, thereby leading to the effective inhibition of tumor growth through intratumoral and systemic immune responses. Additionally, the hydrogel induces robust immune memory, providing substantial protection against tumor recurrence. These findings underscore the potential of Mn2+ ion-coordinated antitumor peptide hydrogel as an advanced platform for enhancing antitumor immunotherapy.

Phase-separating peptide coacervates with programmable material properties for universal intracellular delivery of macromolecules

Phase-separating peptides (PSPs) self-assembling into coacervate microdroplets (CMs) are a promising class of intracellular delivery vehicles that can release macromolecular modalities deployed in a wide range of therapeutic treatments. However, the molecular grammar governing intracellular uptake and release kinetics of CMs remains elusive. Here, we systematically manipulate the sequence of PSPs to unravel the relationships between their molecular structure, the physical properties of the resulting CMs, and their delivery efficacy. We show that a few amino acid alterations are sufficient to modulate the viscoelastic properties of CMs towards either a gel-like or a liquid-like state as well as their binding interaction with cellular membranes, collectively enabling to tune the kinetics of intracellular cargo release. We also demonstrate that the optimized PSPs CMs display excellent transfection efficiency in hard-to-transfect cells such as primary fibroblasts and immune cells. Our findings provide molecular guidelines to precisely program the material properties of PSP CMs and achieve tunable cellular uptake and release kinetics depending on the cargo modality, with broad implications for therapeutic applications such as protein, gene, and immune cell therapies.

Pristine Photopolymerizable Gelatin Hydrogels: A Low-Cost and Easily Modifiable Platform for Biomedical Applications

The study addresses the challenge of temperature sensitivity in pristine gelatin hydrogels, widely used in biomedical applications due to their biocompatibility, low cost, and cell adhesion properties. Traditional gelatin hydrogels dissolve at physiological temperatures, limiting their utility. Here, we introduce a novel method for creating stable hydrogels at 37 °C using pristine gelatin through photopolymerization without requiring chemical modifications. This approach enhances consistency and simplifies production and functionalization of the gelatin with bioactive molecules. The stabilization mechanism involves the partial retention of the triple-helix structure of gelatin below 25 °C, which provides specific crosslinking sites. Upon activation by visible light, ruthenium (Ru) acts as a photosensitizer that generates sulphate radicals from sodium persulphate (SPS), inducing covalent bonding between tyrosine residues and "locking" the triple-helix conformation. The primary focus of this work is the characterization of the mechanical properties, swelling ratio, and biocompatibility of the photopolymerized gelatin hydrogels. Notably, these hydrogels supported better cell viability and elongation in normal human dermal fibroblasts (NHDFs) compared to GelMA, and similar performance was observed for human pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). As a proof of concept for functionalization, gelatin was modified with selenous acid (GelSe), which demonstrated antioxidant and antimicrobial capacities, particularly against E. coli and S. aureus. These results suggest that pristine gelatin hydrogels, enhanced through this new photopolymerization method and functionalized with bioactive molecules, hold potential for advancing regenerative medicine and tissue engineering by providing robust, biocompatible scaffolds for cell culture and therapeutic applications.

Photocrosslinkable triple helical protein with enhanced higher-order formation for biomaterial applications

Bacterial collagen, produced via recombinant DNA methods, offers advantages including consistent purity, customizable properties, and reduced allergy potential compared to animal-derived collagen. Its controlled production environment enables tailored features, making it more sustainable, non-pathogenic, and compatible with diverse applications in medicine, cosmetics, and other industries. Research has focused on the engineering of collagen-like proteins to improve their structure and function. The study explores the impact of introducing tyrosine, an amino acid known for its role in fibril formation across diverse proteins, into a newly designed bacterial collagen-like protein (Scl2), specifically examining its effect on self-assembly and fibril formation. Biophysical analyses reveal that the introduction of tyrosine residues didn't compromise the protein's structural stability but rather promoted self-assembly, resulting in the creation of nanofibrils-a phenomenon absent in the native Scl2 protein. Additionally, stable hydrogels are formed when the engineered protein undergoes di-tyrosine crosslinking under light exposure. The hydrogels, shown to support cell viability, also facilitate accelerated wound healing in mouse fibroblast (NIH/3T3) cells. These outcomes demonstrate that the targeted inclusion of functional residues in collagen-like proteins enhances fibril formation and facilitates the generation of robust hydrogels using riboflavin chemistry, presenting promising paths for research in tissue engineering and regenerative medicine.

A Dual-Fluorescence Molecular "Open Bridge" for Evaluating Gestational Hypoxia and Hypertension under the Stress of SARS-Cov-2

Gestational hypertension is a dangerous condition that is sometimes fatal to the mother and her unborn off-spring. The strong connection between hypertension and hypoxia is emphasized by the currently rampaging SARS-Cov-2, which can induce similar conditions, in which hemolysis and the subsequent oxidative damage may release hemoglobin and tissue factor into the serum. To detect these dangerous proteins normally absent from serum, we mimic the molecular pathology of hypoxia, resulting in a synthesizable molecular machine around which a new bioassay can be designed to simultaneously detect the two proteins in a one-step and reagentless fashion. The "open bridge"-like probe can split into two upon ATP-induced cross-linking of hemoglobin to the probe. The covalently captured hemoglobin can subsequently use its peroxidase-like activity to induce a second cross-coupling between the probe and the tissue factor. A fluorescent probe-target covalent complex is formed, enabling thorough rinsing to minimize nonspecific interference. Finally, using hemoglobin's peroxidase activity to improve sensitivity, the assay has been successfully applied in detecting the two proteins in the periphery serum of pregnant women. These results may promise a near future application of the proposed method for providing an early warning for gestational hypoxia and hypertension, particularly under the stress of SARS-Cov-2.

Design, Synthesis and Characterization of Mn(II)Cysteine-Tyrosine Dithiocarbamate Complex for against the Cancer on MCF-7 Breast Cancer Cell Line

OBJECTIVE

Breast cancer is the most frequently diagnosed cancer and the second cause of death worldwide. The drug often used for chemotherapy is cisplatin. However, the drug cisplatin has a number of problems, including lack of selectivity, undesirable side effects, resistance, and toxicity in the body. So research is carried out on new drug compounds with low toxicity by designing in silico with molecular docking.

METHODS

Mn(II) Cysteine-Tyrosine dithiocarbamate is a new complex molecule whose research involves several steps, such as in-silico molecular docking testing with target proteins, ADMET then synthesis, characterization and in-vitro MCF-7 cells for anticancer drugs. The synthesis process involves the reaction of manganese metal with tyrosine, cysteine, CS2 and KOH. Characterization tests have been carried out including FT-IR spectroscopy, SEM-EDS, UV Vis, conductivity, melting point and XRD.

RESULT

Confirm the structure of the compound using UV Vis, obtained orbitals π to π* and n to π* in the group N = C = S is represented by the absorption at 400 nm and 600 nm, FT-IR with the results obtained by the functional groups O-H, N-H, C =N and C=S. In vitro test results showed morphological changes (apoptosis) in MCF-7 cancer cells starting from 250 μg/mL and an IC50 value of 416.90 µg/mL. Molecular docking studies of the Mn(II)Cysteine-Tyrosine dithiocarbamate complex were identified with 4,4',4''-[(2R)-butane-1,1,2-triyl]triphenol - Estrogen α which showed an active site with amino acid residues GLU323, GLU385, VAL446, ILE514, TRP360, LYS449, MET388, MET357, PHE445, VAL392 and ILE389. Hydrophobic and hydrophobic bonds are seen in Mn(II)Cysteine-Tyrosine dithiocarbamate - Estrogen α has a bond energy of -77.5372 kJ/mol.

CONCLUSION

Despite having a high H-bond interaction intensity, the chemical does not have a powerful enough anticancer impact. Despite the produced compound's low bioactivity, this study should offer important new understandings into how molecular structure affects anticancer activity.

Peptide-IR820 Conjugate: A Promising Strategy for Efficient Vascular Disruption and Hypoxia Induction in Melanoma

Photothermal therapy (PTT) has emerged as a noninvasive and precise cancer treatment modality known for its high selectivity and lack of drug resistance. However, the clinical translation of many PTT agents is hindered by the limited biodegradability of inorganic nanoparticles and the instability of organic dyes. In this study, a peptide conjugate, IR820-Cys-Trp-Glu-Trp-Thr-Trp-Tyr (IR820-C), was designed to self-assemble into nanoparticles for both potent PTT and vascular disruption in melanoma treatment. When co-assembled with the poorly soluble vascular disrupting agent (VDA) combretastatin A4 (CA4), the resulting nanoparticles (IR820-C@CA4 NPs) accumulate efficiently in tumors, activate systemic antitumor immune responses, and effectively ablate melanoma with a single treatment and near-infrared irradiation, as confirmed by our in vivo experiments. Furthermore, by exploiting the resulting tumor hypoxia, we subsequently administered the hypoxia-activated prodrug tirapazamine (TPZ) to capitalize on the created microenvironment, thereby boosting therapeutic efficacy and antimetastatic potential. This study showcases the potential of short-peptide-based nanocarriers for the design and development of stable and efficient photothermal platforms. The multifaceted therapeutic strategy, which merges photothermal ablation with vascular disruption and hypoxia-activated chemotherapy, holds great promise for advancing the efficacy and scope of cancer treatment modalities.

Applications of self-assembled peptide hydrogels in anti-tumor therapy

Peptides are a class of active substances composed of a variety of amino acids with special physiological functions. The rational design of peptide sequences at the molecular level enables their folding into diverse secondary structures. This property has garnered significant attention in the biomedical sphere owing to their favorable biocompatibility, adaptable mechanical traits, and exceptional loading capabilities. Concurrently with advancements in modern medicine, the diagnosis and treatment of tumors have increasingly embraced targeted and personalized approaches. This review explores recent applications of self-assembled peptides derived from natural amino acids in chemical therapy, immunotherapy, and other adjunctive treatments. We highlighted the utilization of peptide hydrogels as delivery systems for chemotherapeutic drugs and other bioactive molecules and then discussed the challenges and prospects for their future application.

Porous protein crystals: synthesis and applications

Large-pore protein crystals (LPCs) are an emerging class of biomaterials. The inherent diversity of proteins translates to a diversity of crystal lattice structures, many of which display large pores and solvent channels. These pores can, in turn, be functionalized via directed evolution and rational redesign based on the known crystal structures. LPCs possess extremely high solvent content, as well as extremely high surface area to volume ratios. Because of these characteristics, LPCs continue to be explored in diverse applications including catalysis, targeted therapeutic delivery, templating of nanostructures, structural biology. This Feature review article will describe several of the existing platforms in detail, with particular focus on LPC synthesis approaches and reported applications.

Harnessing prion-inspired amyloid self-assembly for sustainable and biocompatible proton conductivity

Protein-based materials have emerged as promising candidates for proton-conducting biomaterials. Therefore, drawing inspiration from the amino acid composition of prion-like domains, we designed short self-assembling peptides incorporating the (X-Tyr) motif, with X representing Asn, Gly and Ser, which form fibrillar structures capable of conducting protons. In this study, we conducted an analysis of the conductivity capacity of these fibers, with a focus on temperature and frequency dependence of conductivity. The loss tangent curves data and the electrode polarization model with the Debye approximation were employed to calculate transport properties, including conductivity, diffusivity, and density of charge carriers. Results revealed the prion-like fibers can transport protons more efficiently than biomaterials and other synthetic proton conducting materials, and that a significant increase in conductivity is observed with fibrillar orientations. The temperature dependence of conductivity of the peptides, measured in wet conditions, showed conductivities following the trend σ(NY7) < σ(GY7) < σ(SY7), in all the range of temperatures studied. The Arrhenius behavior, and the activation energy associated with conductivity followed the trend: Eact (SY7) = 8.2 ± 0.6 kJ mol-1 < Eact (GY7) < 13 ± 5 kJ mol-1 < Eact (NY7) = 31 ± 7 kJ mol-1, in different range of temperatures depending of the peptide. Furthermore, the diffusion coefficient correlated with increasing temperature in GY7 and SY7 fibers for temperatures compress between 20 °C and 80 °C, while NY7 only below 60 °C. However, it is noteworthy that the diffusivity observed in the SY7 peptide is lower, compared to GY7 and NY7 presumably due to its enlarged length. This observation can be attributed to two factors: firstly, the higher conductivity values observed in SY7 compared to GY7 and NY7, and secondly, to the value of relation observed of cations present in the peptide SY7 compared with GY7 and NY7, which in turn is dependent on temperature. In light of these findings, we envision our prion-inspired nanofibers as highly efficient proton-conducting natural biopolymers that are both biocompatible and biodegradable. These properties provide the opportunity for the development of next-generation bioelectrical interfaces and protonic devices.

Self-Assembling Triple-Helix Recombinant Collagen Hydrogel Enriched with Tyrosine

The self-assembly of collagen within the human body creates a complex 3D fibrous network, providing structural integrity and mechanical strength to connective tissues. Recombinant collagen plays a pivotal role in the realm of biomimetic natural collagen. However, almost all of the reported recombinant collagens lack the capability of self-assembly, severely hindering their application in tissue engineering and regenerative medicine. Herein, we have for the first time constructed a series of self-assembling tyrosine-rich triple helix recombinant collagens, mimicking the structure and functionality of natural collagen. The recombinant collagen consists of a central triple-helical domain characterized by the (Gly-Xaa-Yaa)n sequence, along with N-terminal and C-terminal domains featuring the GYY sequence. The introduction of GYY has a negligible impact on the stability of the triple-helical structure of recombinant collagen while simultaneously promoting its self-assembly into fibers. In the presence of [Ru(bpy)3]Cl2 and APS as catalysts, tyrosine residues in the recombinant collagen undergo covalent cross-linking, resulting in a hydrogel with exceptional mechanical properties. The recombinant collagen hydrogel exhibits outstanding biocompatibility and bioactivity, significantly enhancing the proliferation, adhesion, migration, and differentiation of HFF-1 cells. This innovative self-assembled triple-helix recombinant collagen demonstrates significant potential in the fields of tissue engineering and medical materials.

Chemical cyclization of tyrosine-containing peptides via in situ generated triazolinedione peptides

Tyr-derived cyclic peptide natural products are formed by enzymatic manifolds that oxidatively cross-link embedded phenolic side chains of tyrosine (Tyr) and 4-hydroxyphenylglycine residues during their controlled production. Bioactive Tyr-derived cyclic peptides, such as the arylomycins and vancomycins, continue to motivate the development of enzymatic and chemical strategies for their de novo assembly and modification. However, chemical access to these structurally diverse natural cycles can be challenging and step intensive. Therefore, we developed an oxidative procedure to selectively convert Tyr-containing N4-substituted 1,2,4-triazolidine-3,5-dione peptides (urazole peptides) into stable Tyr-linked cyclic peptides. We show that Tyr-containing urazole peptides are simple to prepare and convert into reactive N4-substituted 1,2,4-triazoline-3,5-dione peptides by oxidation, which then undergo spontaneous cyclization under mildly basic aqueous conditions to form a cross-linkage with the phenol side chain of embedded Tyr residues. Using this approach, we have demonstrated access to over 25 Tyr-linked cyclic peptides (3- to 11-residue cycles) with good tolerance of native residue side chain functionalities. Importantly, this method is simple to perform, and product formation can be quickly confirmed by mass spectrometric and 1H NMR spectroscopic analyses.

Molecular Crowding: The History and Development of a Scientific Paradigm

It is now generally accepted that macromolecules do not act in isolation but "live" in a crowded environment, that is, an environment populated by numerous different molecules. The field of molecular crowding has its origins in the far 80s but became accepted only by the end of the 90s. In the present issue, we discuss various aspects that are influenced by crowding and need to consider its effects. This Review is meant as an introduction to the theme and an analysis of the evolution of the crowding concept through time from colloidal and polymer physics to a more biological perspective. We introduce themes that will be more thoroughly treated in other Reviews of the present issue. In our intentions, each Review may stand by itself, but the complete collection has the aspiration to provide different but complementary perspectives to propose a more holistic view of molecular crowding.

Self-propelled assembly of nanoparticles with self-catalytic regulation for tumour-specific imaging and therapy

Targeted assembly of nanoparticles in biological systems holds great promise for disease-specific imaging and therapy. However, the current manipulation of nanoparticle dynamics is primarily limited to organic pericyclic reactions, which necessitate the introduction of synthetic functional groups as bioorthogonal handles on the nanoparticles, leading to complex and laborious design processes. Here, we report the synthesis of tyrosine (Tyr)-modified peptides-capped iodine (I) doped CuS nanoparticles (CuS-I@P1 NPs) as self-catalytic building blocks that undergo self-propelled assembly inside tumour cells via Tyr-Tyr condensation reactions catalyzed by the nanoparticles themselves. Upon cellular internalization, the CuS-I@P1 NPs undergo furin-guided condensation reactions, leading to the formation of CuS-I nanoparticle assemblies through dityrosine bond. The tumour-specific furin-instructed intracellular assembly of CuS-I NPs exhibits activatable dual-modal imaging capability and enhanced photothermal effect, enabling highly efficient imaging and therapy of tumours. The robust nanoparticle self-catalysis-regulated in situ assembly, facilitated by natural handles, offers the advantages of convenient fabrication, high reaction specificity, and biocompatibility, representing a generalizable strategy for target-specific activatable biomedical imaging and therapy.

The Sleep Quality- and Myopia-Linked PDE11A-Y727C Variant Impacts Neural Physiology by Reducing Catalytic Activity and Altering Subcellular Compartmentalization of the Enzyme

Recently, a Y727C variant in the dual-specific 3',5'-cyclic nucleotide phosphodiesterase 11A (PDE11A-Y727C) was linked to increased sleep quality and reduced myopia risk in humans. Given the well-established role that the PDE11 substrates cAMP and cGMP play in eye physiology and sleep, we determined if (1) PDE11A protein is expressed in the retina or other eye segments in mice, (2) PDE11A-Y7272C affects catalytic activity and/or subcellular compartmentalization more so than the nearby suicide-associated PDE11A-M878V variant, and (3) Pde11a deletion alters eye growth or sleep quality in male and female mice. Western blots show distinct protein expression of PDE11A4, but not PDE11A1-3, in eyes of Pde11a WT, but not KO mice, that vary by eye segment and age. In HT22 and COS-1 cells, PDE11A4-Y727C reduces PDE11A4 catalytic activity far more than PDE11A4-M878V, with both variants reducing PDE11A4-cAMP more so than PDE11A4-cGMP activity. Despite this, Pde11a deletion does not alter age-related changes in retinal or lens thickness or axial length, nor vitreous or anterior chamber depth. Further, Pde11a deletion only minimally changes refractive error and sleep quality. That said, both variants also dramatically alter the subcellular compartmentalization of human and mouse PDE11A4, an effect occurring independently of dephosphorylating PDE11A4-S117/S124 or phosphorylating PDE11A4-S162. Rather, re-compartmentalization of PDE11A4-Y727C is due to the loss of the tyrosine changing how PDE11A4 is packaged/repackaged via the trans-Golgi network. Therefore, the protective impact of the Y727C variant may reflect a gain-of-function (e.g., PDE11A4 displacing another PDE) that warrants further investigation in the context of reversing/preventing sleep disturbances or myopia.

Hierarchical self-assembly of a reflectin-derived peptide

Reflectins are a family of intrinsically disordered proteins involved in cephalopod camouflage, making them an interesting source for bioinspired optical materials. Understanding reflectin assembly into higher-order structures by standard biophysical methods enables the rational design of new materials, but it is difficult due to their low solubility. To address this challenge, we aim to understand the molecular self-assembly mechanism of reflectin's basic unit-the protopeptide sequence YMDMSGYQ-as a means to understand reflectin's assembly phenomena. Protopeptide self-assembly was triggered by different environmental cues, yielding supramolecular hydrogels, and characterized by experimental and theoretical methods. Protopeptide films were also prepared to assess optical properties. Our results support the hypothesis for the protopeptide aggregation model at an atomistic level, led by hydrophilic and hydrophobic interactions mediated by tyrosine residues. Protopeptide-derived films were optically active, presenting diffuse reflectance in the visible region of the light spectrum. Hence, these results contribute to a better understanding of the protopeptide structural assembly, crucial for the design of peptide- and reflectin-based functional materials.

Feature architecture aware phylogenetic profiling indicates a functional diversification of type IVa pili in the nosocomial pathogen Acinetobacter baumannii

The Gram-negative bacterial pathogen Acinetobacter baumannii is a major cause of hospital-acquired opportunistic infections. The increasing spread of pan-drug resistant strains makes A. baumannii top-ranking among the ESKAPE pathogens for which novel routes of treatment are urgently needed. Comparative genomics approaches have successfully identified genetic changes coinciding with the emergence of pathogenicity in Acinetobacter. Genes that are prevalent both in pathogenic and a-pathogenic Acinetobacter species were not considered ignoring that virulence factors may emerge by the modification of evolutionarily old and widespread proteins. Here, we increased the resolution of comparative genomics analyses to also include lineage-specific changes in protein feature architectures. Using type IVa pili (T4aP) as an example, we show that three pilus components, among them the pilus tip adhesin ComC, vary in their Pfam domain annotation within the genus Acinetobacter. In most pathogenic Acinetobacter isolates, ComC displays a von Willebrand Factor type A domain harboring a finger-like protrusion, and we provide experimental evidence that this finger conveys virulence-related functions in A. baumannii. All three genes are part of an evolutionary cassette, which has been replaced at least twice during A. baumannii diversification. The resulting strain-specific differences in T4aP layout suggests differences in the way how individual strains interact with their host. Our study underpins the hypothesis that A. baumannii uses T4aP for host infection as it was shown previously for other pathogens. It also indicates that many more functional complexes may exist whose precise functions have been adjusted by modifying individual components on the domain level.

Dragonfly-Inspired Wing Design Enabled by Machine Learning and Maxwell's Reciprocal Diagrams

This research is taking the first steps toward applying a 2D dragonfly wing skeleton in the design of an airplane wing using artificial intelligence. The work relates the 2D morphology of the structural network of dragonfly veins to a secondary graph that is topologically dual and geometrically perpendicular to the initial network. This secondary network is referred as the reciprocal diagram proposed by Maxwell that can represent the static equilibrium of forces in the initial graph. Surprisingly, the secondary graph shows a direct relationship between the thickness of the structural members of a dragonfly wing and their in-plane static equilibrium of forces that gives the location of the primary and secondary veins in the network. The initial and the reciprocal graph of the wing are used to train an integrated and comprehensive machine-learning model that can generate similar graphs with both primary and secondary veins for a given boundary geometry. The result shows that the proposed algorithm can generate similar vein networks for an arbitrary boundary geometry with no prior topological information or the primary veins' location. The structural performance of the dragonfly wing in nature also motivated the authors to test this research's real-world application for designing the cellular structures for the core of airplane wings as cantilever porous beams. The boundary geometry of various airplane wings is used as an input for the design proccedure. The internal structure is generated using the training model of the dragonfly veins and their reciprocal graphs. One application of this method is experimentally and numerically examined for designing the cellular core, 3D printed by fused deposition modeling, of the airfoil wing; the results suggest up to 25% improvements in the out-of-plane stiffness. The findings demonstrate that the proposed machine-learning-assisted approach can facilitate the generation of multiscale architectural patterns inspired by nature to form lightweight load-bearable elements with superior structural properties.

Effects of Nelumbonucifera Gaertn. Petal Tea Extract on Hepatotoxicity and Oxidative Stress Induced by Mancozeb in Rat Model

Mancozeb (Mz) is one of the most widely used pesticides that has been reported to cause adverse human health risks. White Nelumbo nucifera (N. nucifera) petals have therapeutic properties to prevent toxicity. Hence, this study attempted to determine the effects of N. nucifera extract on hepatotoxicity and oxidative stress in mancozeb-treated rats. Seventy-two male rats were divided into nine groups and designed with a control; N. nucifera extract was administered at the doses of 0.55, 1.1, and 2.2 mg/kg bw/day, Mz was administered at 500 mg/kg bw/day, and the co-treatment groups (N. nucifera and Mz) were administered 0.55, 1.1, and 2.2 mg/kg bw/day of N. nucifera followed by administering Mz 500 mg/kg bw/day daily for 30 days. The results showed that all doses of N. nucifera extract did not induce hepatic toxicity and could suppress the toxicity of mancozeb by increasing body weight gain and decreasing relative liver weight, lobular inflammation, and total injury score. The combination treatment also decreased the molecular markers of oxidative stress (2-hydroxybutyric acid, 4-hydroxynonenal, l-tyrosine, pentosidine, and N6-carboxymethyllysine). Furthermore, the reduced glutathione and oxidized glutathione contents were adjusted close to the normal level. Therefore, N. nucifera extract is a natural antioxidant supplement that could decrease the toxicity of mancozeb and can be safely consumed.

Strategies for improving the 3D printability of decellularized extracellular matrix bioink

3D bioprinting is a revolutionary technology capable of replicating native tissue and organ microenvironments by precisely placing cells into 3D structures using bioinks. However, acquiring the ideal bioink to manufacture biomimetic constructs is challenging. A natural extracellular matrix (ECM) is an organ-specific material that provides physical, chemical, biological, and mechanical cues that are hard to mimic using a small number of components. Organ-derived decellularized ECM (dECM) bioink is revolutionary and has optimal biomimetic properties. However, dECM is always "non-printable" owing to its poor mechanical properties. Recent studies have focused on strategies to improve the 3D printability of dECM bioink. In this review, we highlight the decellularization methods and procedures used to produce these bioinks, effective methods to improve their printability, and recent advances in tissue regeneration using dECM-based bioinks. Finally, we discuss the challenges associated with manufacturing dECM bioinks and their potential large-scale applications.

Towards understanding the mechanism of 3D printing using protein: femtosecond laser direct writing of microstructures made from homopeptides

Femtosecond laser direct write (fs-LDW) is a promising technology for three-dimensional (3D) printing due to its high resolution, flexibility, and versatility. A protein solution can be used as a precursor to fabricate 3D proteinaceous microstructures that retain the protein's native function. The large diversity of protein molecules with different native functions allows diverse applications of this technology. However, our limited understanding of the mechanism of the printing process restricts the design and generation of 3D microstructures for biomedical applications. Therefore, we used eight commercially available homopeptides as precursors for fs-LDW of 3D structures. Our experimental results show that tyrosine, histidine, glutamic acid, and lysine contribute more to the fabrication process than do proline, threonine, phenylalanine, and alanine. In particular, we show that tyrosine is highly beneficial in the fabrication process. The beneficial effect of the charged amino acids glutamic acid and lysine suggests that the printing mechanism involves ions in addition to the previously proposed radical mechanism. Our results further suggest that the uneven electron density over larger amino acid molecules is key in aiding fs-LDW. The findings presented here will help generate more desired 3D proteinaceous microstructures by modifying protein precursors with beneficial amino acids. STATEMENT OF SIGNIFICANCE: Femtosecond laser direct write (fs-LDW) offers a three-dimensional (3D) printing capability for creating well-defined micro-and nanostructures. Applying this technology to proteins enables the manufacture of complex biomimetic 3D micro-and nanoarchitectures with retention of their original protein functions. To our knowledge, amino acid homo-polymers themselves have never been used as precursor for fs-LDW so far. Our studygainsseveral new insights into the 3D printing mechanism of pure protein for the first time. We believe that the experimental evidence presented greatly benefits the community of 3D printing of proteinin particular and the biomaterial science community in general. With the gained insight, we aspire toexpand the possibilitiesof biomaterial and biomedical applications of this technique.

Ionogel-Electrode for the Study of Protein Tunnel Junctions under Physiologically Relevant Conditions

The study of charge transport through proteins is essential for understanding complicated electrochemical processes in biological activities while the reasons for the coexistence of tunneling and hopping phenomena in protein junctions still remain unclear. In this work, a flexible and conductive ionogel electrode is synthesized and is used as a top contact to form highly reproducible protein junctions. The junctions of proteins, including human serum albumin, cytochrome C and hemoglobin, show temperature-independent electron tunneling characteristics when the junctions are in solid states while with a different mechanism of temperature-dependent electron hopping when junctions are hydrated under physiologically relevant conditions. It is demonstrated that the solvent reorganization energy plays an important role in the electron-hopping process and experimentally shown that it requires ≈100 meV for electron hopping through one heme group inside a hydrated protein molecule connected between two electrodes.

Reactive Oxygen Species-Responsive Transformable and Triple-Targeting Butylphthalide Nanotherapy for Precision Treatment of Ischemic Stroke by Normalizing the Pathological Microenvironment

High potency and safe therapies are still required for ischemic stroke, which is a leading cause of global death and disability. Herein, a reactive oxygen species (ROS)-responsive, transformable, and triple-targeting dl-3-n-butylphthalide (NBP) nanotherapy was developed for ischemic stroke. To this end, a ROS-responsive nanovehicle (OCN) was first constructed using a cyclodextrin-derived material, which showed considerably enhanced cellular uptake in brain endothelial cells due to notably reduced particle size, morphological transformation, and surface chemistry switching upon triggering via pathological signals. Compared to a nonresponsive nanovehicle, this ROS-responsive and transformable nanoplatform OCN exhibited a significantly higher brain accumulation in a mouse model of ischemic stroke, thereby affording notably potentiated therapeutic effects for the nanotherapy derived from NBP-containing OCN. For OCN decorated with a stroke-homing peptide (SHp), we found significantly increased transferrin receptor-mediated endocytosis, in addition to the previously recognized targeting capability to activated neurons. Consistently, the engineered transformable and triple-targeting nanoplatform, i.e., SHp-decorated OCN (SON), displayed a more efficient distribution in the injured brain in mice with ischemic stroke, showing considerable localization in endothelial cells and neurons. Furthermore, the finally formulated ROS-responsive transformable and triple-targeting nanotherapy (NBP-loaded SON) demonstrated highly potent neuroprotective activity in mice, which outperformed the SHp-deficient nanotherapy at a 5-fold higher dose. Mechanistically, our bioresponsive, transformable, and triple-targeting nanotherapy attenuated the ischemia/reperfusion-induced endothelial permeability and improved dendritic remodeling and synaptic plasticity of neurons in the injured brain tissue, thereby promoting much better functional recovery, which were achieved by efficiently enhancing NBP delivery to the ischemic brain tissue, targeting injured endothelial cells and activated neurons/microglial cells, and normalizing the pathological microenvironment. Moreover, preliminary studies indicated that the ROS-responsive NBP nanotherapy displayed a good safety profile. Consequently, the developed triple-targeting NBP nanotherapy with desirable targeting efficiency, spatiotemporally controlled drug release performance, and high translational potential holds great promise for precision therapy of ischemic stroke and other brain diseases.

An Antibacterial Polypeptide Coating Prepared by In Situ Enzymatic Polymerization for Preventing Delayed Infection of Implants

Delayed implant-associated infection is an important challenge, as the treatment involves a high risk of implant replacement. Mussel-inspired antimicrobial coatings can be applied to coat a variety of implants in a facile way, but the adhesive 3,4-dihydroxyphenylalanine (DOPA) group is prone to oxidation. Therefore, an antibacterial polypeptide copolymer poly(Phe₇-stat-Lys₁₀)-b-polyTyr₃ was designed to prepare the implant coating upon tyrosinase-induced enzymatic polymerization for preventing implant-associated infections. Both poly(Phe₇-stat-Lys₁₀) and polyTyr₃ blocks have specific functions: the former provides intrinsic antibacterial activity with a low risk to induce antimicrobial resistance, and the latter is attachable to the surface of implants to rapidly generate an antibacterial coating by in situ injection of polypeptide copolymer since tyrosine could be oxidized to DOPA under catalyzation of skin tyrosinase. This polypeptide coating with excellent antibacterial effect and desirable biofilm inhibition activity is promising for broad applications in a multitude of biomedical materials to combat delayed infections.

Photocrosslinkable natural polymers in tissue engineering

Natural polymers have been widely used in scaffolds for tissue engineering due to their superior biocompatibility, biodegradability, and low cytotoxicity compared to synthetic polymers. Despite these advantages, there remain drawbacks such as unsatisfying mechanical properties or low processability, which hinder natural tissue substitution. Several non-covalent or covalent crosslinking methods induced by chemicals, temperatures, pH, or light sources have been suggested to overcome these limitations. Among them, light-assisted crosslinking has been considered as a promising strategy for fabricating microstructures of scaffolds. This is due to the merits of non-invasiveness, relatively high crosslinking efficiency via light penetration, and easily controllable parameters, including light intensity or exposure time. This review focuses on photo-reactive moieties and their reaction mechanisms, which are widely exploited along with natural polymer and its tissue engineering applications.

Tyrosine-Derived Polymers as Potential Biomaterials: Synthesis Strategies, Properties, and Applications

Peptide-based polymers are evolving as promising materials for various biomedical applications. Among peptide-based polymers, polytyrosine (PTyr)-based and l-tyrosine (Tyr)-derived polymers are unique, due to their excellent biocompatibility, degradability, and functional as well as engineering properties. To date, different polymerization techniques (ring-opening polymerization, enzymatic polymerization, condensation polymerization, solution-interfacial polymerization, and electropolymerization) have been used to synthesize various PTyr-based and Tyr-derived polymers. Even though the synthesis starts from Tyr, different synthesis routes yield different polymers (polypeptides, polyarylates, polyurethanes, polycarbonates, polyiminocarbonate, and polyphosphates) with unique functional characteristics, and these polymers have been successfully used for various biomedical applications in the past decades. This Review comprehensively describes the synthesis approaches, classification, and properties of various PTyr-based and Tyr-derived polymers employed in drug delivery, tissue engineering, and biosensing applications.

A Diphenylalanine Based Pentapeptide with Fibrillating Self-Assembling Properties

Peptides and their related compounds can self-assemble into diverse nanostructures of different shapes and sizes in response to various stimuli such as pH, temperature or ionic strength. Here we report the synthesis and characterization of a lysozyme derived pentapeptide and its ability to build well-defined fibrillar structures. Lysozyme FESNF peptide fragment was synthesized by solid phase peptide synthesis using the Fmoc/t-Bu strategy, purified by analytical high-performance liquid chromatography (HPLC) and its molecular weight was confirmed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Spectroscopic features of this pentapeptide were investigated by UV-visible spectroscopy and fluorimetry showing the pattern of marginal phenylalanine residues within the peptide sequence. Self-assembling properties were determined using atomic force microscopy (AFM), aggregation index and thioflavin T assay (ThT). FESNF generating fibrillar structures observed by AFM and aggregation propensity were primarily influenced by pH conditions. Moreover, the experimental data were confirmed by molecular dynamics simulation studies. The obtained fibrils will be used next to explore their potential to act as support material for medical and cosmetic application.

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

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

Collagen and Silk Fibroin as Promising Candidates for Constructing Catalysts

A catalyst determines the mechanism of an organic chemical reaction, thus enabling the commercially viable formation of desired material products. Biopolymers offer new opportunities for the construction of catalysts by virtue of their biocompatibility, environmental benignity, and sustainability, as well as their low cost. Biopolymers are especially useful as carriers and precursors in catalysis application. The employment of biocompatible and biosustainable collagen and silk fibroin materials will revolutionize state-of-the-art electronic devices and systems that currently rely on conventional technologies. In this review, we first consider the ordered hierarchical structure, origin, and processing methods of collagen and silk fibroin. Then, the unique advantages and applicability of collagen and silk fibroin for constructing catalysts are summarized. Moreover, a summary of the state-of-the-art design, fabrication, and application of collagen- and silk fibroin-based catalysts, as well as the application of collagen- and silk-based catalysts, is presented by focusing on their roles as carriers and precursors, respectively. Finally, challenges and prospects are assessed for the construction and development of collagen and silk fibroin-based catalysts.

Self-Assembled Peptide-Based Nanodrugs: Molecular Design, Synthesis, Functionalization, and Targeted Tumor Bioimaging and Biotherapy

Functional nanomaterials as nanodrugs based on the self-assembly of inorganics, polymers, and biomolecules have showed wide applications in biomedicine and tissue engineering. Ascribing to the unique biological, chemical, and physical properties of peptide molecules, peptide is used as an excellent precursor material for the synthesis of functional nanodrugs for highly effective cancer therapy. Herein, recent progress on the design, synthesis, functional regulation, and cancer bioimaging and biotherapy of peptide-based nanodrugs is summarized. For this aim, first molecular design and controllable synthesis of peptide nanodrugs with 0D to 3D structures are presented, and then the functional customization strategies for peptide nanodrugs are presented. Then, the applications of peptide-based nanodrugs in bioimaging, chemotherapy, photothermal therapy (PTT), and photodynamic therapy (PDT) are demonstrated and discussed in detail. Furthermore, peptide-based drugs in preclinical, clinical trials, and approved are briefly described. Finally, the challenges and potential solutions are pointed out on addressing the questions of this promising research topic. This comprehensive review can guide the motif design and functional regulation of peptide nanomaterials for facile synthesis of nanodrugs, and further promote their practical applications for diagnostics and therapy of diseases.

Antimicrobial nano-assemblies of tryptocidine C, a tryptophan-rich cyclic decapeptide, from ethanolic solutions

Tryptocidine C (TpcC), a Trp-rich cyclodecapeptide is a minor constituent in the antibiotic tyrothricin complex from Brevibacillus parabrevis. TpcC possesses a high tendency to oligomerise in aqueous solutions and dried TpcC forms distinct self-assembled nanoparticles. High-resolution scanning electron microscopy revealed the influence of different ethanol:water solvent systems on TpcC self-assembly, with the TpcC, dried from a high concentration in 15% ethanol, primarily assembling into small nanospheres with 24.3 nm diameter and 0.05 polydispersity. TpcC at 16 μM, near its CMC, formed a variety of structures such as small nanospheres, large dense nanospheroids and facetted 3-D-crystals, as well as sheets and coarse carpet-like structures which depended on ethanol concentration. Drying 16 μM TpcC from 75% ethanol resulted in highly facetted 3-D crystals, as well as small nanospheres, while those in 10% ethanol preparation had less defined facets. Drying from 20 to 50% ethanol led to polymorphic architectures with a few defined nanospheroids and various small nanoparticles, imbedded in carpet- and sheet-like structures. These polymorphic surface morphologies correlated with maintenance of fluorescence properties and the surface-derived antibacterial activity against Staphylococcus aureus over time, while there was a significant change in fluorescence and loss in activity in the 10% and 75% preparations where 3-D crystals were observed. This indicated that TpcC oligomerisation in solutions with 20-50% ethanol leads to metastable structures with a high propensity for release of antimicrobial moieties, while those leading to crystallisation limit active moieties release. TpcC nano-assemblies can find application in antimicrobial coatings, surface disinfectants, food packaging and wound healing materials.

Electron transport via tyrosine-doped oligo-alanine peptide junctions: role of charges and hydrogen bonding

A way of modulating the solid-state electron transport (ETp) properties of oligopeptide junctions is presented by charges and internal hydrogen bonding, which affect this process markedly. The ETp properties of a series of tyrosine (Tyr)-containing hexa-alanine peptides, self-assembled in monolayers and sandwiched between gold electrodes, are investigated in response to their protonation state. Inserting a Tyr residue into these peptides enhances the ETp carried via their junctions. Deprotonation of the Tyr-containing peptides causes a further increase of ETp efficiency that depends on this residue's position. Combined results of molecular dynamics simulations and spectroscopic experiments suggest that the increased conductance upon deprotonation is mainly a result of enhanced coupling between the charged C-terminus carboxylate group and the adjacent Au electrode. Moreover, intra-peptide hydrogen bonding of the Tyr hydroxyl to the C-terminus carboxylate reduces this coupling. Hence, the extent of such a conductance change depends on the Tyr-carboxylate distance in the peptide's sequence.

Solvent modulation in peptide sub-microfibers obtained by solution blow spinning

Peptides possess high chemical diversity at the amino acid sequence level, which further translates into versatile functions. Peptides with self-assembling properties can be processed into diverse formats giving rise to bio-based materials. Peptide-based spun fibers are an interesting format due to high surface-area and versatility, though the field is still in its infancy due to the challenges in applying the synthetic polymer spinning processes to protein fibers to peptides. In this work we show the use of solution blow-spinning to produce peptide fibers. Peptide fiber formation was assisted by the polymer poly (vinyl pyrrolidone) (PVP) in two solvent conditions. Peptide miscibility and further self-assembling propensity in the solvents played a major role in fiber formation. When employing acetic acid as solvent, peptide fibers (0.5 μm) are formed around PVP fibers (0.75 μm), whereas in isopropanol only one type of fibers are formed, consisting of mixed peptide and PVP (1 μm). This report highlights solvent modulation as a mean to obtain different peptide sub-microfibers via a single injection nozzle in solution blow spinning. We anticipate this strategy to be applied to other small peptides with self-assembly propensity to obtain multi-functional proteinaceous fibers.

Urea-Modified Self-Assembling Peptide Amphiphiles That Form Well-Defined Nanostructures and Hydrogels for Biomedical Applications

Hydrogen bonding plays a critical role in the self-assembly of peptide amphiphiles (PAs). Herein, we studied the effect of replacing the amide linkage between the peptide and lipid portions of the PA with a urea group, which possesses an additional hydrogen bond donor. We prepared three PAs with the peptide sequence Phe-Phe-Glu-Glu (FFEE): two are amide-linked with hydrophobic tails of different lengths and the other possesses an alkylated urea group. The differences in the self-assembled structures formed by these PAs were assessed using diverse microscopies, nuclear magnetic resonance (NMR), and dichroism techniques. We found that the urea group influences the morphology and internal arrangement of the assemblies. Molecular dynamics simulations suggest that there are about 50% more hydrogen bonds in nanostructures assembled from the urea-PA than those assembled from the other PAs. Furthermore, in silico studies suggest the presence of urea-π stacking interactions with the phenyl group of Phe, which results in distinct peptide conformations in comparison to the amide-linked PAs. We then studied the effect of the urea modification on the mechanical properties of PA hydrogels. We found that the hydrogel made of the urea-PA exhibits increased stability and self-healing ability. In addition, it allows cell adhesion, spreading, and growth as a matrix. This study reveals that the inclusion of urea bonds might be useful in controlling the morphology, mechanical, and biological properties of self-assembled nanostructures and hydrogels formed by the PAs.

Rhodium-Catalyzed Annulation of Vinylated Tyrosines with Internal Alkynes to Access Oxepine-Mounted Unnatural Tyrosines and Its Peptide Late Stage Functionalization

A Rh(III)-catalyzed [5+2] annulation of vinyl tyrosines with symmetrical and unsymmetrical internal alkynes was achieved, furnishing a series of oxepine-mounted tyrosine-based unnatural amino acids. In addition, the chemical applicability of the developed strategy was exemplified by stapling amino acid/peptide-appended alkynes with vinyl tyrosines and late stage functionalization of tyrosine-containing dipeptides and tripeptide with internal alkynes.

Control of Tyrosyl Radical Stabilization by {SiO2@Oligopeptide} Hybrid Biomimetic Materials

Tyrosine radicals are notoriously short-lived/unstable in solution, while they present an impressive degree of stability and versatility in bioenzymes. Herein, we have developed a library of hybrid biomimetic materials (HBMs), which consists of tyrosine-containing oligopeptides covalently grafted on SiO₂ nanoparticles, and studied the formation, lifetime, and redox properties of tyrosyl radicals. Using electron paramagnetic resonance spectroscopy, we have studied the radical-spin distribution as a probe of the local microenvironment of the tyrosyl radicals in the HBMs. We find that the lifetime of the tyrosyl radical can be enhanced by up to 6 times, by adjusting three factors, namely, a proximal histidine, the length of the oligopeptide, and the interface with the SiO₂ nanomatrix. This is shown to be correlated to a significant lowering of E_1/2 from +736 mV, in free tyrosine, to +548 mV in the {12-peptide}@SiO₂ material. Moreover, we show that grafting on SiO₂ lowers the E_1/2 of tyrosine radicals by ∼50 mV in all oligopeptides. Analysis of the spin-distribution by EPR reveals that the positioning of a histidine at a H-bonding distance from the tyrosine further favors tyrosine radical stabilization.

Peptide-Based Coacervate-Core Vesicles with Semipermeable Membranes

Coacervates droplets have long been considered as potential protocells to mimic living cells. However, these droplets lack a membrane and are prone to coalescence, limiting their ability to survive, interact, and organize into higher-order assemblies. This work shows that tyrosine-rich peptide conjugates can undergo liquid-liquid phase separation in a well-defined pH window and transform into stable membrane-enclosed protocells by enzymatic oxidation and cross-linking at the liquid-liquid interface. The oxidation of the tyrosine-rich peptides into dityrosine creates a semipermeable, flexible membrane around the coacervates with tunable thickness, which displays strong intrinsic fluorescence, and stabilizes the coacervate protocells against coalescence. The membranes have an effective molecular weight cut-off of 2.5 kDa, as determined from the partitioning of small dyes and labeled peptides, RNA, and polymers into the membrane-enclosed coacervate protocells. Flicker spectroscopy reveals a membrane bending rigidity of only 0.1k_B T, which is substantially lower than phospholipid bilayers despite a larger membrane thickness. Finally, it is shown that enzymes can be stably encapsulated inside the protocells and be supplied with substrates from outside, which opens the way for these membrane-bound compartments to be used as molecularly crowded artificial cells capable of communication or as a vehicle for drug delivery.

Surface Biofunctionalization of Silk Biomaterials Using Dityrosine Cross-Linking

Biofunctionalization of silk biomaterial surfaces with extracellular matrix (ECM) molecules, cell binding peptides, or growth factors is important in a range of applications, including tissue engineering and development of implantable medical devices. Passive adsorption is the most common way to immobilize molecules of interest on preformed silk biomaterials but can lead to random molecular orientations and displacement from the surface, limiting their applications. Herein, we developed techniques for covalent immobilization of biomolecules using enzyme- or photoinitiated formation of dityrosine bonds between the molecule of interest and silk. Using recombinantly expressed domain V of the human basement membrane proteoglycan perlecan (rDV) as a model molecule, we demonstrated that rDV can be covalently immobilized via dityrosine cross-linking without the need to modify rDV or silk biomaterials. Dityrosine-based immobilization resulted in a different molecular orientation to passively absorbed rDV with less C- and N-terminal region exposure on the surface. Dityrosine-based immobilization supported functional rDV immobilization where immobilized rDV supported endothelial cell adhesion, spreading, migration, and proliferation. These results demonstrate the utility of dityrosine-based cross-linking in covalent immobilization of tyrosine-containing molecules on silk biomaterials in the absence of chemical modification, adding a simple and accessible technique to the silk biofunctionalization toolbox.

Sequence-Dependent Tyrosine-Containing Peptide Nanoassemblies for Sensing Tyrosinase and Melanoma

Tyrosine-containing peptide nanoassemblies have received tremendous attention because of their potential applications in biomedicine and nanomaterial fields. However, a current outstanding challenge is to direct the equilibrium between oxidative polymerization of precursors and the noncovalent assembly to precisely tune their specific nanostructures and functionalities through the rational design of peptide sequences. With a simple library of tripeptides containing tyrosine, glycine, and lysine, here we demonstrate how amino acid sequence encodes the property of tripeptide nanoassemblies by modulating the enzymatic oxidation of tyrosinase with the accompanied self-assembly, and thus select the pathways toward fluorescent or melanin-like nanoassemblies. The fluorescence of tripeptide nanoassemblies has been demonstrated in sensing both tyrosinase and melanoma. Our findings will provide inspiration of peptide sequence design for generating the complex bioactive peptide nanomaterials for biomedical applications.

Photochemical synthesis of pink silver and its use for monitoring peptide nitration via surface enhanced Raman spectroscopy (SERS)

Oxidative stress may cause extended tyrosine posttranslational modifications of peptides and proteins. The 3-nitro-L-tyrosine (Nit), which is typically formed, affects protein behavior during neurodegenerative processes, such as Alzheimer's and Parkinson's diseases. Such metabolic products may be conveniently detected at very low concentrations by surface enhanced Raman spectroscopy (SERS). Previously, we have explored the SERS detection of the Nit NO₂ bending vibrational bands in a presence of hydrogen chloride (Niederhafner et al., Amino Acids 53:517-532, 2021, ibid). In this article, we describe performance of a new SERS substrate, "pink silver", synthesized photochemically. It provides SERS even without the HCl induction, and the acid further decreases the detection limit about 9 times. Strong SERS bands were observed in the asymmetric (1550-1475 cm^-1) and symmetric (1360-1290 cm^-1) NO stretching in the NO₂ group. The bending vibration was relatively weak, but appeared stronger when HCl was added. The band assignments were supported by density functional theory modeling.

Charge-Modulated Accessibility of Tyrosine Residues for Silk-Elastin Copolymer Cross-Linking

The modulation of reaction kinetics with horseradish peroxidase (HRP)-catalyzed cross-linking of proteins remains a useful strategy to modulate hydrogel formation. Here, we demonstrate that the presence of positively charged lysines in silk-elastin-like polymers impacts the thermal transition temperature of these proteins, while the location in the primary sequence modulates the reactivity of the tyrosines. The positively charged lysine side chains decreased π-π interactions among the tyrosines and reduced the rate of formation and number of HRP-mediated dityrosine bonds, dependent on the proximity of the charged group to the tyrosine. The results suggest that the location of repulsive charges can be used to tailor the reaction kinetics for enzymatic cross-linking, providing further control of gelation rates for in situ gel formation and the resulting protein-based gel characteristics.

Micro- and Nanocapsules Based on Artificial Peptides

The encapsulation of active ingredients into solid capsules from biodegradable materials has received significant attention over the last decades. In this short review, we focus on the formation of micro- and nano-sized capsules and emulsions based on artificial peptides as a fully degradable material. It deals with various approaches for the preparation of peptide-based capsules as well as with their crucial properties such as size and stability. We categorize all preparation procedures into three basic approaches: self-assembly, polymerization and crosslinking, and layer-by-layer technology. This article is meant to offer a short overview over all successful methods suitable for obtaining access to these very promising carrier systems.