Ultra-strong bio-glue from genetically engineered polypeptides

Nano-fibrous biopolymers as building blocks for gel networks: Interactions, characterization, and applications

Biopolymers derived from natural resources are highly abundant, biodegradable, and biocompatible, making them promising candidates to replace non-renewable fossil fuels and mitigate environmental and health impacts. Nano-fibrous biopolymers possessing advantages of biopolymers entangle with each other through inter-/intra-molecular interactions, serving as ideal building blocks for gel construction. These biopolymer nanofibers often synergize with other nano-building blocks to enhance gels with desirable functions and eco-friendliness across various applications in biomedical, environmental, and energy sectors. The inter-/intra-molecular interactions directly affect the assembly of nano-building blocks, which determines the structure of gels, and the integrity of connected nano-building blocks, influencing the mechanical properties and the performance of gels in specific applications. This review focuses on four biopolymer nanofibers (cellulose, chitin, silk, collagen), commonly used in gel preparations, as representatives for polysaccharides and polypeptides. The covalent and non-covalent interactions between biopolymers and other materials have been categorized and discussed in relation to the resulting gel network structures and properties. Nanomechanical characterization techniques, such as surface forces apparatus (SFA) and atomic force microscopy (AFM), have been employed to precisely quantify the intermolecular interactions between biopolymers and other building blocks. The applications of these gels are classified and correlated to the functions of their building blocks. The inter-/intra-molecular interactions act as "sewing threads", connecting all nano-building blocks to establish suitable network structures and functions. This review aims to provide a comprehensive understanding of the interactions involved in gel preparation and the design principles needed to achieve targeted functional gels.

Coacervate-Derived Assembly of Poly(ethylene glycol) Nanoparticles for Combinational Tumor Therapy

Coacervates have garnered significant attention as potential drug carriers. However, the instability resulting from their intrinsic membrane-free nature restricts the application of coacervates in drug delivery. Herein, the engineering of poly(ethylene glycol) nanoparticles (PEG NPs) is reported using coacervates composed of PEG and polyphenols as the templates, where PEG is subsequently cross-linked based on different chemistries (e.g., thiol-disulfide exchange, click chemistry, and Schiff base reaction). The reported assembly strategy avoids the template removal process and the resultant PEG NPs exhibit excellent stability in the physiological environment compared to coacervates. The presence of polyphenols in PEG NPs enables the loading of various cargos including metal ions (i.e., Ru, Gd, Mn, Fe) and drug molecules (i.e., doxorubicin), which demonstrates their promise in magnetic resonance imaging and combinational tumor therapy. This work provides a promising strategy to promote the development of coacervate-derived NPs as a drug delivery system for biomedical applications.

Molecular self-assembly strategy tuning a dry crosslinking protein patch for biocompatible and biodegradable haemostatic sealing

Uncontrolled haemorrhage is a leading cause of trauma-related fatalities, highlighting the critical need for rapid and effective haemostasis. Current haemostatic materials encounter limitations such as slow clotting and weak mechanical strength, while most of bioadhesives compromise their adhesion performance to wet tissues for biocompatibility and degradability. In this study, a molecular self-assembly strategy is proposed, developing a biocompatible and biodegradable protein-based patch with excellent adhesion performance. This strategy utilizes fibrinogen modified with hydrophobic groups to induce self-assembly into a hydrogel, which is converted into a dry patch. The protein patch enhances adhesion performance on the wet tissue through a dry cross-linking method and robust intra/inter-molecular interactions. This patch demonstrates excellent haemostatic efficacy in  both porcine oozing wound and porcine severe acute haemorrhage. It maintains biological functionality, and ensures sustained wound sealing while gradually degrading in vivo, making it a promising candidate for clinical tissue sealing applications.

An Antibacterial and Antioxidant Food Packaging Film Based on Amphiphilic Polypeptides-Resveratrol-Chitosan

Antimicrobial and antioxidant packaging films play a crucial role in extending food shelf life, maintaining quality, and enhancing safety by inhibiting microbial growth and slowing oxidation processes. However, most commercial preservative films suffer from limited antimicrobial and antioxidant properties. Moreover, these films are made from petroleum-based materials that degrade into microplastics, resulting in environmental contamination and potential health risks for humans. Herein, an antibacterial and antioxidant food packaging film (CS-SAP@R) is developed by integrating star-shaped amphiphilic polypeptides (SAP) and resveratrol (R) into the chitosan (CS) matrix. The incorporation of SAP not only effectively addresses the existing compatibility issues between the highly hydrophobic resveratrol and water-soluble CS film, but also significantly enhances the antimicrobial properties of CS. Additionally, the well-integrated resveratrol molecules endow the film with superior antioxidant properties. Furthermore, CS-SAP@R has achieved bacterial killing rates of 97.31% against E. coli and 99.05% against S. aureus. The enhanced characteristics of the CS-SAP@R film contribute to its exceptional preservation performance, effectively extending the shelf life of perishable products by ≈3 days when stored at 4 °C. These remarkable attributes underscore the benefits of polypeptide-based biopolymers and demonstrate the potential applicability of the CS-SAP@R film in effectively safeguarding perishable products.

Bio-inspired anti-swelling amyloid-fiber lysozyme adhesive for rapid wound closure and hemostasis

Instant adhesion to wet biological surfaces and reduced swelling of tissue adhesives are crucial for rapid wound closure and hemostasis. However, previous strategies to reduce swelling were always accompanied by a decrease in the tissue bonding strength of the adhesive. Moreover, the irreducibility of the covalent bonds in currently reported adhesives results in the adhesives losing their tissue adhesive ability. To tackle the challenge, a superior anti-swelling coacervate adhesive possessing fast self-healing properties through physical interactions (electrostatic interactions, hydrogen bonding) and chemical crosslinking (Schiff base reaction) was obtained with aldehyde-modified γ-PGA (γ-PGA-CHO), a natural lysozyme (LZM) and an amyloid fiber reduced lysozyme (RLZM). The instant shear adhesion strength and burst pressure tolerance of the adhesive on wet pig intestine reached 50.8 kPa (2.6 times that of CA glue) and 142.5 mmHg (5.9 times that of CA glue), and it maintained an adhesion strength of 37.4 kPa after exposure to the physical environment for 12 h and the swelling rate was only 34.0% underwater. The in vitro and in vivo experiments provided the coacervate adhesive with potential applicability for emergency rescue and wound care scenarios.

Dynamic Peptide Nanoframework-Guided Protein Coassembly: Advancing Adhesion Performance with Hierarchical Structures

Hierarchical structures are essential in natural adhesion systems. Replicating these in synthetic adhesives is challenging due to intricate molecular mechanisms and multiscale processes. Here, we report three phosphorylated peptides featuring a hydrophobic self-assembly motif linked to a hydrophilic phosphorylated sequence (pSGSS), forming peptide fibril nanoframeworks. These nanoframeworks effectively coassemble with elastin-derived positively charged proteins (PCP), resulting in complex coacervate-based adhesives with hierarchical structures. Our method enables the controlled regulation of both cohesion and adhesion properties in the adhesives. Notably, the complex adhesives formed by the dityrosine-containing peptide and PCP demonstrate an exceptional interfacial adhesion strength of up to 30 MPa, outperforming most known supramolecular adhesives and rivaling cross-linked chemical adhesives. Additionally, these adhesives show promising biocompatibility and bioactivity, making them suitable for applications such as visceral hemostasis and tissue repair. Our findings highlight the utility of bioinspired hierarchical assembly combined with bioengineering techniques in advancing biomedical adhesives.

Effect of Macromolecular Architecture on Adhesion

The behavior of single linear chains on a substrate is a well-studied area of polymer science. Herein, one of the most essential issues is the interaction of the chains with the substrate, which determines both macromolecular conformations near the substrate and adhesive properties of polymer materials. However, very little is known about the effect of macromolecular architecture on adhesion. In particular, there was no assessment of the effect of chain branching on the adhesion force. On the other hand, an essential progress in macromolecular chemistry allows the synthesis of various macromolecular architectures, including star-, comb-like, etc., in a very precise way. They are widely used in numerous applications. In particular, synthetic peptides are currently an integral part of many systems for biomedical purposes including bioglues, for which the adhesion force is a fundamental property. In this study, we conducted force experiments on the desorption of star-like pentapeptide chains from a solid substrate using an atomistic model of computer simulations. The cases of a linear chain and four- and eight-armed stars were considered. We have shown that the presence of branching enhances the adsorption strength under a fixed mass of the macromolecules. The force needed for chain desorption was shown to be linearly dependent on the branching degree.

Robustly Injectable Tetra-PEG Hydrogel Sealants for Annulus Fibrosus Repair

Discectomy serves as the primary therapeutic approach for lumbar disc herniation, but the annular fibrosus defects after discectomy may lead to recurrence of disc herniation. Despite recent advances in bioinspired adhesives to seal the AF defect, the growing popularity of endoscopic discectomy has put forward high requirements for the tissue bioadhesives with rapid injectability, easy operation, and robust tissue adhesion in underwater environments. Herein, a rapidly in situ forming injectable tetra-PEG bioadhesive (ISG) comprising of FDA-approved tetra-armed poly (ethylene glycol) amine (tetra-PEG-NH2) and tetra-armed poly (ethylene glycol) succinimidyl glutarate (tetra-PEG-SG) for the sutureless closure of AF defects, is reported. Relying on quick ammonolysis reaction between N-hydroxysuccinimide (NHS)-ester of tetra-PEG-SG polymer and amine groups of tetra-PEG-NH2 polymer and tissue proteins, the uniform networks are formed within seconds with easy injection, efficient waterproofness, instant tissue adhesion, and durable compliance. The goat lumbar discectomy model was used to assess the effect of ISG hydrogels in vivo. The results reveal that the resultant ISG bioadhesive can effectively maintain the disc height, fuse with the host tissue, ameliorate IVD degeneration, and retain the initial biomechanics. Together, this study provides an efficient strategy of in situ injectable glue for the minimally invasive treatment of AF defects.

Spontaneous Self-Organized Order Emerging From Intrinsically Disordered Protein Polymers

Intrinsically disordered proteins (IDPs) are proteins that, despite lacking a defined 3D structure, are capable of adopting dynamic conformations. This structural adaptability allows them to play not only essential roles in crucial cellular processes, such as subcellular organization or transcriptional control, but also in coordinating the assembly of macromolecules during different stages of development. Thus, in order to artificially replicate the complex processes of morphogenesis and their dynamics, it is crucial to have materials that recapitulate the structural plasticity of IDPs. In this regard, intrinsically disordered protein polymers (IDPPs) emerge as promising materials for engineering synthetic condensates and creating hierarchically self-assembled materials. IDPPs exhibit remarkable properties for their use in biofabrication, such as functional versatility, tunable sequence order-disorder, and the ability to undergo liquid-liquid phase separation (LLPS). Recent research has focused on harnessing the intrinsic disorder of IDPPs to design complex protein architectures with tailored properties. Taking advantage of their stimuli-responsiveness and degree of disorder, researchers have developed innovative strategies to control the self-assembly of IDPPs, resulting in the creation of hierarchically organized structures and intricate morphologies. In this review, we aim to provide an overview of the latest advances in the design and application of IDPP-based materials, shedding light on the fundamental principles that control their supramolecular assembly, and discussing their application in the biomedical and nanobiotechnological fields.

Advances in Adhesive Materials for Oral and Maxillofacial Soft Tissue Diseases

Oral diseases represent a prevalent global health burden, profoundly affecting patients' quality of life. Given the involvement of oral mucosa and muscles in diverse physiological functions, coupled with clinical aesthetics considerations, repairing oral and maxillofacial soft tissue defects poses a formidable challenge. Wet-adhesive materials are regarded as promising oral repair materials due to their unique advantages in easily overcoming physical and biological barriers in the oral cavity. This review first introduces the intricate wet-state environment prevalent in the oral cavity, meticulously explaining the fundamental physical and chemical adhesion mechanisms that underpin adhesive materials. It then comprehensively summarizes the diverse types of adhesives utilized in stomatology, encompassing polysaccharide, protein, and synthetic polymer adhesive materials. The review further evaluates the latest research advancements in utilizing these materials to treat various oral and maxillofacial soft tissue diseases, including oral mucosal diseases, periodontitis, peri-implantitis, oral and maxillofacial skin defects, and maxillofacial tumors. Finally, it also highlights the promising future prospects and pivotal challenges related to stomatology application of multifunctional adhesive materials.

Zwitterion-Conjugated Protein Coatings for Enhanced Antifouling in Complex Biofluids: Underlying Molecular Interaction Mechanisms

Biofouling can cause severe infections, device malfunctions, and failures in diagnostics and therapeutics. Proteins such as bovine serum albumin (BSA) have recently been used as coatings to resist biofouling because they combine surface anchoring and antifouling properties. However, their antifouling effectiveness will significantly deteriorate in complex biofluids with high salinity, limiting their practical applications. In this work, we developed a zwitterion-conjugated protein with enhanced antifouling capability by grafting zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) onto BSA protein via a click reaction. This conjugated protein can easily anchor on various substrates, both inorganic and organic, and exhibits efficient and broad-spectrum fouling resistance to metabolites, proteins, and complex biofluids. Even in the complex fetal bovine serum with higher salinity, the BSA@MPC coating can also maintain 99% fouling resistance robustly, over 6-fold superior to native BSA-coated surfaces in antifouling capability. Direct surface forces measurement reveals that such outstanding antifouling properties of conjugated protein BSA@MPC could be attributed to the stable hydration layer on its surface and the steric repulsion from the antipolyelectrolyte behavior of zwitterionic MPC polymer in the high-salinity environment. Our findings advance the development of protein-based functional materials and provide valuable insights for designing novel antifouling surfaces for marine, food, and bioengineering applications.

Robust tetra-armed poly (ethylene glycol)-based hydrogel as tissue bioadhesive for the efficient repair of meniscus tears

Repair and preservation of the injured meniscus has become paramount in clinical practice. However, the complexities of various clinic stitching techniques for meniscus repair pose challenges for grassroots doctors. Hence, there is a compelling interest in innovative therapeutic strategies such as bioadhesives. An ideal bioadhesive must cure quickly in aqueous and blood environments, bind strongly, endure arthroscopic washing pressures, and degrade appropriately for tissue regeneration. Here, we present a tetra-poly (ethylene glycol) (PEG)-based hydrogel bioadhesive, boasting high biocompatibility, ultrafast gelation, facile injectable operation, and favorable mechanical strength. In view of the synergistic effects of chemical anchor and physical chain entanglement to tightly bind the meniscus, a seamless interface was formed between the surrounding meniscal tissues and hydrogels, enabling the longitudinal tear of the meniscus fused in situ to withstand large tensile force with the adhesive strength of 541.5 ± 31.4 kPa and arthroscopic washout resistance of 29.4 kPa. Superior to existing commercial adhesives, ours allows sutureless application and arthroscopic assistance, without requiring specialized clinical skills. This research is expected to significantly impact our understanding of meniscal healing and ultimately promote a simpler process for achieving functional and structural recovery in torn menisci.

Nature-inspired recycling of a protein mixture into a green fluorescent protein-based hydrogel

Protein-based materials are biocompatible and have a variety of remarkable properties; consequently, they are finding more and more applications. Nature recycles proteins in multiple ways, ranging from bio-degradation (a slow approach) to fast recycling of protein metabolism. The latter is a wonderful example because a random mixture of proteins gets digested into amino acids (AAs), the fundamental building blocks of proteins. These AAs are then used by cells to produce whichever protein is needed at the time of synthesis. Seen through the lens of recycling, this process transforms a random mixture into something not necessarily present at the start but needed at the moment of recycling. We have recently shown that the process of protein recycling can be performed in vitro and called it NaCRe (Nature Inspired Circular Recycling). In a previous NaCRe proof-of-concept experiment, we started with various protein mixtures but were able to produce only small quantities of recycled protein, in the microgram scale. Here, we show that NaCRe can be used to convert milligrams of a protein mixture containing one of the most common protein materials (silk) into a milligram of an hydrogel made of green fluorescent protein (GFP). We show that in order for NaCRe to be efficient the starting protein mixture must contain a good balance of all AAs and discuss the challenges encountered when scaling up NaCRe.

piSTING: A Pocket-Independent Agonist Based on Multivalency-Driven STING Oligomerization

The stimulator of interferon genes (STING) pathway is a potent therapeutic target for innate immunity. Despite the efforts to develop pocket-dependent small-molecule STING agonists that mimic the endogenous STING ligand, cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), most of these agonists showed disappointing results in clinical trials owing to the limitations of the STING pocket. In this study, we developed novel pocket-independent STING-activating agonists (piSTINGs), which act through multivalency-driven oligomerization to activate STING. Additionally, a piSTING-adjuvanted vaccine elicited a significant antibody response and inhibited tumour growth in therapeutic models. Moreover, a piSTING-based vaccine combination with aPD-1 showed remarkable potential to enhance the effectiveness of immune checkpoint blockade (ICB) immunotherapy. In particular, piSTING can strengthen the impact of STING pathway in immunotherapy and accelerate the clinical translation of STING agonists.

Mussel Foot Protein-Inspired Adhesive Tapes with Tunable Underwater Adhesion

Instant and strong adhesion to underwater adherends is a big challenge due to the continuous interference of water. Mussel foot protein-bioinspired catechol-based adhesives have garnered great interest in addressing this issue. Herein, a novel self-made catecholic compound with a long aliphatic chain was utilized to prepare thin (∼0.07 mm) and optically transparent (>80%) wet/underwater adhesive tapes by UV-initiated polymerization. Its adhesion activity was water-triggered, fast (<1 min), and strong (adhesion strength to porcine skin: ∼1.99 MPa; interfacial toughness: ∼610 J/m2, burst pressure: ∼1950 mmHg). The effect of the catechol/phenol group and positively charged moiety on the wet/underwater adhesion to abiotic/biotic substrates was investigated. On the wet/underwater adherends, the tape with catechol groups presented much higher interfacial toughness, adhesion strength, and burst pressure than the analogous tape with phenol groups. The tape with both the catechol group and cationic polyelectrolyte chitosan had a more impressive improvement in its adhesion to wet/underwater biological tissues than to abiotic substrates. Therefore, catechol and a positive moiety in the tape would synergistically enhance its wet/underwater adhesion to various substrates, especially to biological tissues. The instant, strong, and noncytotoxic tape may provide applications in underwater adhesion for sealing and wound closure.

Adhesive Zwitterionic Poly(ionic liquid) with Unprecedented Organic Solvent Resistance

The resistance of adhesives to organic solvents is of paramount importance in diverse industries. Unfortunately, many currently available adhesives exhibit either weak intermolecular chain interactions, resulting in insufficient resistance to organic solvents, or possess a permanent covalent crosslinked network, impeding recyclability. This study introduces an innovative approach to address this challenge by formulating zwitterionic poly(ionic liquid) (ZPIL) derivatives with robust dipole-dipole interactions, incorporating sulfonic anions and imidazolium cations. Due to its unique dynamic and electrostatic self-crosslinking structure, the ZPIL exhibits significant adhesion to various substrates and demonstrates excellent recyclability even after multiple adhesion tests. Significantly, ZPIL exhibits exceptional adhesion stability across diverse nonpolar and polar organic solvents, including ionic liquids, distinguishing itself from nonionic polymers and conventional poly(ionic liquid)s. Its adhesive performance remains minimally affected even after prolonged exposure to soaking conditions. The study presents a promising solution for the design of highly organic solvent-resistant materials for plastics, coatings, and adhesives.

An artificial liquid-liquid phase separation-driven silk fibroin-based adhesive for rapid hemostasis and wound sealing

The powerful adhesion systems of marine organisms have inspired the development of artificial protein-based bioadhesives. However, achieving robust wet adhesion using artificial bioadhesives remains technically challenging because the key element of liquid-liquid phase separation (LLPS)-driven complex coacervation in natural adhesion systems is often ignored. In this study, mimicking the complex coacervation phenomenon of marine organisms, an artificial protein-based adhesive hydrogel (SFG hydrogel) was developed by adopting the LLPS-mediated coacervation of the natural protein silk fibroin (SF) and the anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SF/SDBS complex coacervate enabled precise spatial positioning and easy self-adjustable deposition on irregular substrate surfaces, allowing for tight contact. Spontaneous liquid-to-solid maturation promoted the phase transition of the SF/SDBS complex coacervate to form the SFG hydrogel in situ, enhancing its bulk cohesiveness and interfacial adhesion. The formed SFG hydrogel exhibited intrinsic advantages as a new type of artificial protein-based adhesive, including good biocompatibility, robust wet adhesion, rapid blood-clotting capacity, and easy operation. In vitro and in vivo experiments demonstrated that the SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, thus advancing its clinical applications. STATEMENT OF SIGNIFICANCE: Marine mussels utilize the liquid-liquid phase separation (LLPS) strategy to induce the supramolecular assembly of mussel foot proteins, which plays a critical role in strong underwater adhesion of mussel foot proteins. Herein, an artificial protein-based adhesive hydrogel (named SFG hydrogel) was reported by adopting the LLPS-mediated coacervation of natural protein silk fibroin (SF) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SFG hydrogel enabled the precise spatial positioning and easy self-adjustable deposition on substrate surfaces with irregularities, allowing tight interfacial adhesion and cohesiveness. The SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, exhibiting intrinsic advantages as a new type of artificial protein-based bioadhesives.

A solvent-free processed low-temperature tolerant adhesive

Ultra-low temperature resistant adhesive is highly desired yet scarce for material adhesion for the potential usage in Arctic/Antarctic or outer space exploration. Here we develop a solvent-free processed low-temperature tolerant adhesive with excellent adhesion strength and organic solvent stability, wide tolerable temperature range (i.e. -196 to 55 °C), long-lasting adhesion effect ( > 60 days, -196 °C) that exceeds the classic commercial hot melt adhesives. Furthermore, combine experimental results with theoretical calculations, the strong interaction energy between polyoxometalate and polymer is the main factor for the low-temperature tolerant adhesive, possessing enhanced cohesion strength, suppressed polymer crystallization and volumetric contraction. Notably, manufacturing at scale can be easily achieved by the facile scale-up solvent-free processing, showing much potential towards practical application in Arctic/Antarctic or planetary exploration.

Biocompatible Tough Ionogels with Reversible Supramolecular Adhesion

Cohesive and interfacial adhesion energies are difficult to balance to obtain reversible adhesives with both high mechanical strength and high adhesion strength, although various methods have been extensively investigated. Here, a biocompatible citric acid/L-(-)-carnitine (CAC)-based ionic liquid was developed as a solvent to prepare tough and high adhesion strength ionogels for reversible engineered and biological adhesives. The prepared ionogels exhibited good mechanical properties, including tensile strength (14.4 MPa), Young's modulus (48.1 MPa), toughness (115.2 MJ m-3), and high adhesion strength on the glass substrate (24.4 MPa). Furthermore, the ionogels can form mechanically matched tough adhesion at the interface of wet biological tissues (interfacial toughness about 191 J m-2) and can be detached by saline solution on demand, thus extending potential applications in various clinical scenarios such as wound adhesion and nondestructive transfer of organs.

Spidroin-mimetic Engineered Protein Fibers with High Toughness and Minimized Batch-to-batch Variations through β-sheets Co-assembly

Synthetic spidroin fibers have not yet attained the same level of toughness and stability as natural spider silks due to the complexity of composition and hierarchical structure. Particularly, understanding the intricate interactions between spidroin components in spider fiber is still elusive. Herein, we report modular design and preparation of spidroin-mimetic fibers composed of a conservative C-terminus spidroin module, two different natural β-sheets modules, and a non-spidroin random-coil module. The resulting fibers exhibit a toughness of ~200 MJ/m3, reaching the highest value among the reported artificial spider silks. The interactions between two components of recombinant spidroins facilitate the intermolecular co-assembly of β-sheets, thereby enhancing the mechanical strength and reducing batch-to-batch variability in the dual-component spidroin fibers. Additionally, the dual-component spidroin fibers offer potential applications in implantable or even edible devices. Therefore, our work presents a generic strategy to develop high-performance protein fibers for diverse translations in different scenarios.

Emerging Landscape of Supercharged Proteins and Peptides for Drug Delivery

Although groundbreaking biotechnological techniques such as gene editing have significantly progressed, the effective and targeted transport of therapeutic agents into host cells remains a major obstacle to the development of biotherapeutics. Confronting the unique challenge posed by large macromolecules such as proteins, peptides, and nucleic acids adds complexity to this issue. Recent findings reveal that the supercharging of proteins and peptides not only enables control over critical properties, such as temperature resistance and catalytic activity, but also holds promise as a viable strategy for their use in drug delivery. This review provides a concise summary of the attributes of supercharged proteins and peptides, encompassing both their natural occurrence and engineered variants. Furthermore, it sheds light on the present status and future possibilities of supercharged proteins and peptides as carriers for significant biomolecules in the realms of medical research and therapeutic applications.

Artificial structural proteins: Synthesis, assembly and material applications

Structural proteins have evolved over billions of years and offer outstanding mechanical properties, such as resilience, toughness and stiffness. Advances in modular protein engineering, polypeptide modification, and synthetic biology have led to the development of novel biomimetic structural proteins to perform in biomedical and military fields. However, the development of customized structural proteins and assemblies with superior performance remains a major challenge, due to the inherent limitations of biosynthesis, difficulty in mimicking the complexed macroscale assembly, etc. This review summarizes the approaches for the design and production of biomimetic structural proteins, and their chemical modifications for multiscale assembly. Furthermore, we discuss the function tailoring and current applications of biomimetic structural protein assemblies. A perspective of future research is to reveal how the mechanical properties are encoded in the sequences and conformations. This review, therefore, provides an important reference for the development of structural proteins-mimetics from replication of nature to even outperforming nature.

Effect of Indentation Depth on Friction Coefficient in Adhesive Contacts: Experiment and Simulation

The quasi-static regime of friction between a rigid steel indenter and a soft elastomer with high adhesion is studied experimentally. An analysis of the formally calculated dependencies of a friction coefficient on an external load (normal force) shows that the friction coefficient monotonically decreases with an increase in the load, following a power law relationship. Over the entire range of contact loads, a friction mode is realized in which constant shear stresses are maintained in the tangential contact, which corresponds to the "adhesive" friction mode. In this mode, Amonton's law is inapplicable, and the friction coefficient loses its original meaning. Some classical works, which show the existence of a transition between "adhesive" and "normal" friction, were analyzed. It is shown that, in fact, there is no such transition. A computer simulation of the indentation process was carried out within the framework of the boundary element method, which confirmed the experimental results.

Linear and ring polypeptides complexed with oppositely charged surfactants: the cohesion of the complexes as revealed in atomistic simulations

The use of linear supercharged unfolded polypeptides (SUPs) and oppositely charged surfactants in aqueous solution has demonstrated impressive adhesive properties. These substances possess biocompatibility, biodegradability and other necessary properties for practical application as a biomedical glue in wound repair. The success of these substances, coupled with limited knowledge about such systems, provides hope for enhancing the performance of the final product. One potential approach involves altering the topology of the polypeptide chain. In this article, we conduct a comparative analysis to examine the behavior of the ring and linear chains of a polypeptide in aqueous solution. This analysis utilizes full-atomic computer modeling to monitor the properties of the chains. We investigate the temperature dependence of the shape and size of individual polypeptides in the solution, as well as the formation of complexes via mixing the polypeptide chains with oppositely charged sodium dodecylbenzene sulfonate (SDBS) surfactant molecules in a stoichiometric ratio. Additionally, we explore the cohesive properties of the resulting complex through power experiments involving the extraction of single polypeptide chains out of the SUP-SDBS complexes.

Underwater Adhesives from Redox-Responsive Polyplexes of Thiolated Polyamide Polyelectrolytes

We report the fabrication of optically clear underwater adhesives using polyplexes of oppositely charged partially-thiolated polyamide polyelectrolytes (TPEs). The thiol content of the constituent PEs was varied to assess its influence on the adhesive properties of the resulting glues. These catechol-free, redox-responsive TPE-adhesives were formulated in aquo and exhibited high optical transparency and strong adhesion even on submerged or moist surfaces of diverse polar substrates such as glass, aluminium, wood, and bone pieces. The adhesives could be cured under water through oxidative disulphide crosslinking of the constituent TPEs. The polyamide backbone provided multi-site H-bonding interactions with the substrates while the disulphide crosslinking provided the cohesive strength to the glue. Strong adhesion of mammalian bones (load bearing capacity upto 7 kg/cm2 ) was achieved using the adhesive containing 30 mol % thiol residues. Higher pH and use of oxidants such as povidone-iodine solution enhanced the curing rate of the adhesives, and so did the use of Tris buffer instead of Phosphate buffer. The porous architecture of the adhesive and its progressive degradation in aqueous medium over the course of three weeks bode well for diverse biomedical applications where temporary adhesion of tissues is required.

A General and Convenient Peptide Self-Assembling Mechanism for Developing Supramolecular Versatile Nanomaterials Based on The Biosynthetic Hybrid Amyloid-Resilin Protein

Self-assembling peptides are valuable building blocks to fabricate supramolecular biomaterials, which have broad applications from biomedicine to biotechnology. However, limited choices to induce different globular proteins into hydrogels hinder these designs. Here, an easy-to-implement and tunable self-assembling strategy, which employs Ure2 amyloidogenic peptide, are described to induce any target proteins to assemble into supramolecular hydrogels alone or in combination with notable compositional control. Furthermore, the collective effect of nanoscale interactions among amyloid nanofibrils and partially disordered elastomeric polypeptides are investigated. This led to many useful macroscopic material properties simultaneously emerging from one pure protein material, i.e. strong adhesion to any substrates under wet conditions, rapidly self--assembling into robust and porous hydrogels, adaptation to remodeling processes, strongly promoting cell adhesion, proliferation and differentiation. Moreover, he demonstrated this supramolecular material's robust performance in vitro and vivo for tissue engineering, cosmetic and hemostasis applications and exhibited superior performance compared to corresponding commercial counterparts. To the best of his knowledge, few pure protein-based materials could meet such seemingly mutually exclusive properties simultaneously. Such versatility renders this novel supramolecular nanomaterial as next-generation functional protein-based materials, and he demonstrated the sequence level modulation of structural order and disorder as an untapped principle to design new proteins.

Robust aortic media adhesion using hydrophobically modified Alaska pollock gelatin-based adhesive for aortic dissections

Type-A aortic dissection is an acute injury involving the delamination of the aorta at the parts of the aortic media. Aldehyde crosslinker-containing glues have been used to adhere to the media of the dissected aorta before joining an artificial graft. These glues effectively adhere to the aortic media; however, they show low biocompatibility due to the release of aldehyde compounds. In this study, we report innovative adhesives based on hydrophobically modified Alaska pollock gelatin (hm-ApGltn) with different alkyl or cholesteryl (Chol) groups that adhere to the media of the dissected aorta by combining hm-ApGltns with a biocompatible crosslinker, pentaerythritol poly(ethylene glycol) ether tetrasuccinimidyl glutarate. The modification of alkyl or Chol groups contributed to enhanced adhesion strength between porcine aortic media. The adhesion strength increased with increasing modification ratios of alkyl groups from propanoyl to dodecanoyl groups and then decreased at a modification ratio of ~20 mol %. Porcine aortic media adhered using 7.5Chol-ApGltn adhesive showed stretchability even when expanded and shrunk vertically by 25% at least five times. Hm-ApGltn adhesives subcutaneously injected into the backs of mice showed no severe inflammation and were degraded during the implantation period. These results indicated that hm-ApGltn adhesives have potential applications in type-A aortic dissection.

Biomimetic, self-coacervating adhesive with tough underwater adhesion for ultrafast hemostasis and infected wound healing

Massive bleeding and wound infection due to severe traumas pose a huge threat to the life and health of sufferers; therefore, it is of clinical importance to fabricate adhesives with rapid hemostatic and superior antibacterial capabilities. However, the weak wet adhesion and insufficient function of existing bioadhesives limits their practical application. In this study, a sandcastle worm protein inspired polyelectrolyte self-coacervate adhesive of poly-γ-glutamic acid (PGA) and lysozyme (LZM) was developed. The adhesive exhibited strong underwater adhesion to various surfaces (>250 kPa for solid plates and >50 kPa for soft tissues) and maintained a 80 kPa even when soaked in water for 7 days. Rat liver and tail defect bleeding models revealed that the hemostatic efficiency was superior to that of commercial samples. The in vitro antimicrobial tests showed that the bacterial inhibition to Staphylococcus aureus and Escherichia coli reached almost 100%. Additionally, the infected wound regeneration model demonstrated that the healing rate of the adhesive group was about 100% within 15 days, which was greater than that of the control group. In vitro and in vivo experiments proved that this facilely prepared adhesive will be a promising material to fulfil the integration functions for rapid wound closure and facilitating wound healing.

Genetically Engineered Protein-Based Bioadhesives with Programmable Material Properties

Silk-amyloid-mussel foot protein (SAM) hydrogels made from recombinant fusion proteins containing β-amyloid peptide, spider silk domain, and mussel foot protein (Mfp) are attractive bioadhesives as they display a unique combination of tunability, biocompatibility, bioabsorbability, strong cohesion, and underwater adhesion to a wide range of biological surfaces. To design tunable SAM hydrogels for tailored surgical repair applications, an understanding of the relationships between protein sequence and hydrogel properties is imperative. Here, we fabricated SAM hydrogels using fusion proteins of varying lengths of silk-amyloid repeats and Mfps to characterize their structure and properties. We found that increasing silk-amyloid repeats enhanced the hydrogel's β-sheet content (r = 0.74), leading to higher cohesive strength and toughness. Additionally, increasing the Mfp length beyond the half-length of the full Mfp sequence (1/2 Mfp) decreased the β-sheet content (r = -0.47), but increased hydrogel surface adhesion. Among different variants, the hydrogel made of 16xKLV-2Mfp displayed a high ultimate strength of 3.0 ± 0.3 MPa, an ultimate strain of 664 ± 119%, and an attractive underwater adhesivity of 416 ± 20 kPa to porcine skin. Collectively, the sequence-structure-property relationships learned from this study will be useful to guide the design of future protein adhesives with tunable characteristics for tailored surgical applications.

Bioinspired engineered proteins enable universal anchoring strategy for surface functionalization

HYPOTHESIS

Conventional coating strategies and materials for bio-applications with protective, diagnostic, and therapeutic functions are commonly limited by their arduous preparation processes and lack of on-demand functionalities. Herein, inspired by the 'root-leaf' structure of grass, a series of novel polyacrylate-conjugated proteins can be engineered with sticky bovine serum albumin (BSA) protein as a 'root' anchoring layer and a multifunctional polyacrylate as a 'leaf' functional layer for the facile coating procedure and versatile surface functionalities.

EXPERIMENTS

The engineered proteins were synthesized based on click chemistry, where the 'root' layer can universally anchor onto both organic and inorganic substrates through a facile dip/spraying method with excellent stability in harsh solution conditions, thanks to its multiple adaptive molecular interactions with substrates that further elucidated by molecular force measurements between the 'root' BSA protein and substrates. The 'leaf' conjugated-polyacrylates imparted coatings with versatile on-demand functionalities, such as resistance to over 99% biofouling in complex biofluids, pH-responsive performance, and robust adhesion with various nanomaterials.

FINDINGS

By synergistically leveraging the universal anchoring capabilities of BSA with the versatile physicochemical properties of polyacrylates, this study introduces a promising and facile strategy for imparting novel functionalities to a myriad of surfaces through engineering natural proteins and biomaterials for biotechnical and nanotechnical applications.

The construction of elastin-like polypeptides and their applications in drug delivery system and tissue repair

Elastin-like polypeptides (ELPs) are thermally responsive biopolymers derived from natural elastin. These peptides have a low critical solution temperature phase behavior and can be used to prepare stimuli-responsive biomaterials. Through genetic engineering, biomaterials prepared from ELPs can have unique and customizable properties. By adjusting the amino acid sequence and length of ELPs, nanostructures, such as micelles and nanofibers, can be formed. Correspondingly, ELPs have been used for improving the stability and prolonging drug-release time. Furthermore, ELPs have widespread use in tissue repair due to their biocompatibility and biodegradability. Here, this review summarizes the basic property composition of ELPs and the methods for modulating their phase transition properties, discusses the application of drug delivery system and tissue repair and clarifies the current challenges and future directions of ELPs in applications.

Functional adhesive hydrogels for biological interfaces

Hydrogel adhesives are extensively employed in biological interfaces such as epidermal flexible electronics, tissue engineering, and implanted device. The development of functional hydrogel adhesives is a critical, yet challenging task since combining two or more attributes that seem incompatible into one adhesive hydrogel without sacrificing the hydrogel's pristine capabilities. In this Review, we highlight current developments in the fabrication of functional adhesive hydrogels, which are suitable for a variety of application scenarios, particularly those that occur underwater or on tissue/organ surface conditions. The design strategies for a multifunctional adhesive hydrogel with desirable properties including underwater adhesion, self-healing, good biocompatibility, electrical conductivity, and anti-swelling are discussed comprehensively. We then discuss the challenges faced by adhesive hydrogels, as well as their potential applications in biological interfaces. Adhesive hydrogels are the star building blocks of bio-interface materials for individualized healthcare and other bioengineering areas.

Facilely Prepared Thirsty Granules Arouse Tough Wet Adhesion on Overmoist Wounds for Hemostasis and Tissue Repair

Bioadhesives have been widely used in hemostasis and tissue repair, but the overmoist and wet nature of wound surface (due to the presence of blood and/or wound exudate) has led to poor wet adhesion of bioadhesives, which interrupts the continuous care of wounds. Here, a thirsty polyphenolic silk granule (Tan@SF-pwd-hydro), which absorbs blood and exudate to self-convert to robust bioadhesives (Tan@SF-gel-hydro) in situ, was facilely developed in this study for enhanced wet adhesion toward hemostasis and tissue repair. Tan@SF-pwd-hydro could shield wounds' wetness and immediately convert itself to Tan@SF-gel-hydro to seal wounds for hemorrhage control and wound healing. The maximum adhesiveness of Tan@SF-gel-hydro over wet pigskin was as high as 59.8 ± 2.1 kPa. Tan@SF-pwd-hydro is a promising transformative dressing for hemostasis and tissue repair since its hemostatic time was approximately half of that of the commercial hemostatic product, CeloxTM, and its healing period was much shorter than that of the commercial bioadhesive product, TegadermTM. This pioneering study utilized adverse wetness over wounds to arouse robust adhesiveness by converting thirsty granules to bioadhesives in situ, creatively turning adversity into opportunities. The facile fabrication approach also offers new perspectives for manufacturing sustainability of biomaterials.

Strong Protein Adhesives through Lanthanide-enhanced Structure Folding and Stack Density

Generating strong adhesion by engineered proteins has the potential for high technical applications. Current studies of adhesive proteins are primarily limited to marine organisms, e.g., mussel adhesive proteins. Here, we present a modular engineering strategy to generate a type of exotic protein adhesives with super strong adhesion behaviors. In the protein complexes, the lanmodulin (LanM) underwent α-helical conformational transition induced by lanthanides, thereby enhancing the stacking density and molecular interactions of adhesive protein. The resulting adhesives exhibited outstanding lap-shear strength of ≈31.7 MPa, surpassing many supramolecular and polymer adhesives. The extreme temperature (-196 to 200 °C) resistance capacity and underwater adhesion performance can significantly broaden their practical application scenarios. Ex vivo and in vivo experiments further demonstrated the persistent adhesion performance for surgical sealing and healing applications.

Rational Design of Bioactive Materials for Bone Hemostasis and Defect Repair

Everyday unnatural events such as trauma, accidents, military conflict, disasters, and even medical malpractice create open wounds and massive blood loss, which can be life-threatening. Fractures and large bone defects are among the most common types of injuries. Traditional treatment methods usually involve rapid hemostasis and wound closure, which are convenient and fast but may result in various complications such as nerve injury, deep infection, vascular injury, and deep hematomas. To address these complications, various studies have been conducted on new materials that can be degraded in the body and reduce inflammation and abscesses in the surgical area. This review presents the latest research progress in biomaterials for bone hemostasis and repair. The mechanisms of bone hemostasis and bone healing are first introduced and then principles for rational design of biomaterials are summarized. After providing representative examples of hemostatic biomaterials for bone repair, future challenges and opportunities in the field are proposed.

Biomimetic Structural Proteins: Modular Assembly and High Mechanical Performance

Protein-based biomaterials attract growing interests due to their encoded and programmable robust mechanical properties, superelasticity, plasticity, shape adaptability, excellent interfacial behavior, etc., derived from sequence-guided backbone structures, particularly compared to chemically synthetic counterparts in materials science and biomedical engineering. For example, protein materials have been successfully fabricated as (1) artificial implants (man-made tendons, cartilages, or dental tissues), due to programmable chemistry and biocompatibility; (2) smart biodevices with temperature/light-response and self-healing effects; and (3) impact resistance materials having great mechanical performance due to biomimetics. However, the existing method of regenerating protein materials from natural sources has two critical issues, low yield and structural damage, making it unable to meet demands. Therefore, it is crucial to develop an alternative strategy for fabricating protein materials. Heterologous expression of natural proteins with a modular assembly approach is an effective strategy for material preparation. Standardized, easy-to-assemble protein modules with specific structures and functions are developed through experimental and computational tools based on natural functional protein sequences. Through recombination and heterologous expression, these artificial protein modules become keys to material fabrication. Undergoing an assembly process similar to supramolecular self-assembly of proteins in cells, biomimetic modules can be fabricated for formation of macroscopic materials such as fibers and adhesives. This strategy inspired by synthetic biology and supramolecular chemistry is important for improving target protein yields and assembly integrity. It also preserves and optimizes the mechanical functions of structural proteins, accelerating the design and fabrication of artificial protein materials.In this Account, we overview recent studies on fabricating biomimetic protein materials to elucidate the concept of modular assembly. We discuss the design of biomimetic structural proteins at the molecular level, providing a wealth of details determining the bulk properties of materials. Additinally, we describe the modular self-assembly and assembly driven by inducing molecules, and mechanical properties and applications of resulting fibers. We used these strategies to develop fiber materials with high tensile strength, high toughness, and properties such as anti-icing and high-temperature resistance. We also extended this approach to design protein-based adhesives with ultra-strong adhesion, biocompatibility, and biodegradability for surgical applications such as wound sealing and healing. Other protein materials, including films and hydrogels, have been developed through chemical assembly routes. Finally, we describe exploiting synthetic biology and chemistry to overcome bottlenecks in structural protein modular design, biosynthesis, and material assembly and our perspectives for future development in structural biomaterials.

Tunable backbone-degradable robust tissue adhesives via in situ radical ring-opening polymerization

Adhesives with both robust adhesion and tunable degradability are clinically and ecologically vital, but their fabrication remains a formidable challenge. Here we propose an in situ radical ring-opening polymerization (rROP) strategy to design a backbone-degradable robust adhesive (BDRA) in physiological environment. The hydrophobic cyclic ketene acetal and hydrophilic acrylate monomer mixture of the BDRA precursor allows it to effectively wet and penetrate substrates, subsequently forming a deep covalently interpenetrating network with a degradable backbone via redox-initiated in situ rROP. The resulting BDRAs show good adhesion strength on diverse materials and tissues (e.g., wet bone >16 MPa, and porcine skin >150 kPa), higher than that of commercial cyanoacrylate superglue (~4 MPa and 56 kPa). Moreover, the BDRAs have enhanced tunable degradability, mechanical modulus (100 kPa-10 GPa) and setting time (seconds-hours), and have good biocompatibility in vitro and in vivo. This family of BDRAs expands the scope of medical adhesive applications and offers an easy and environmentally friendly approach for engineering.

Advances, challenges, and prospects for surgical suture materials

As one of the long-established and necessary medical devices, surgical sutures play an essentially important role in the closing and healing of damaged tissues and organs postoperatively. The recent advances in multiple disciplines, like materials science, engineering technology, and biomedicine, have facilitated the generation of various innovative surgical sutures with humanization and multi-functionalization. For instance, the application of numerous absorbable materials is assuredly a marvelous progression in terms of surgical sutures. Moreover, some fantastic results from recent laboratory research cannot be ignored either, ranging from the fiber generation to the suture structure, as well as the suture modification, functionalization, and even intellectualization. In this review, the suture materials, including natural or synthetic polymers, absorbable or non-absorbable polymers, and metal materials, were first introduced, and then their advantages and disadvantages were summarized. Then we introduced and discussed various fiber fabrication strategies for the production of surgical sutures. Noticeably, advanced nanofiber generation strategies were highlighted. This review further summarized a wide and diverse variety of suture structures and further discussed their different features. After that, we covered the advanced design and development of surgical sutures with multiple functionalizations, which mainly included surface coating technologies and direct drug-loading technologies. Meanwhile, the review highlighted some smart and intelligent sutures that can monitor the wound status in a real-time manner and provide on-demand therapies accordingly. Furthermore, some representative commercial sutures were also introduced and summarized. At the end of this review, we discussed the challenges and future prospects in the field of surgical sutures in depth. This review aims to provide a meaningful reference and guidance for the future design and fabrication of innovative surgical sutures. STATEMENT OF SIGNIFICANCE: This review article introduces the recent advances of surgical sutures, including material selection, fiber morphology, suture structure and construction, as well as suture modification, functionalization, and even intellectualization. Importantly, some innovative strategies for the construction of multifunctional sutures with predetermined biological properties are highlighted. Moreover, some important commercial suture products are systematically summarized and compared. This review also discusses the challenges and future prospects of advanced sutures in a deep manner. In all, this review is expected to arouse great interest from a broad group of readers in the fields of multifunctional biomaterials and regenerative medicine.

Protein fibers with self-recoverable mechanical properties via dynamic imine chemistry

The manipulation of internal interactions at the molecular level within biological fibers is of particular importance but challenging, severely limiting their tunability in macroscopic performances and applications. It thus becomes imperative to explore new approaches to enhance biological fibers' stability and environmental tolerance and to impart them with diverse functionalities, such as mechanical recoverability and stimulus-triggered responses. Herein, we develop a dynamic imine fiber chemistry (DIFC) approach to engineer molecular interactions to fabricate strong and tough protein fibers with recoverability and actuating behaviors. The resulting DIF fibers exhibit extraordinary mechanical performances, outperforming many recombinant silks and synthetic polymer fibers. Remarkably, impaired DIF fibers caused by fatigue or strong acid treatment are quickly recovered in water directed by the DIFC strategy. Reproducible mechanical performance is thus observed. The DIF fibers also exhibit exotic mechanical stability at extreme temperatures (e.g., -196 °C and 150 °C). When triggered by humidity, the DIFC endows the protein fibers with diverse actuation behaviors, such as self-folding, self-stretching, and self-contracting. Therefore, the established DIFC represents an alternative strategy to strengthen biological fibers and may pave the way for their high-tech applications.

Engineered Bicomponent Adhesives with Instantaneous and Superior Adhesion Performance for Wound Sealing and Healing Applications

Surgical adhesives are playing an important role in wound repair and emergency hemostasis in clinical treatment. However, the development of strong bioglue with rapid in situ adhesion, durable adhesiveness, and flexibility in dynamic and moist physiological environments is still challenging. Herein, a new type of biosynthetic protein bioadhesives with superior adhesion performance is reported by developing a protein aldimine condensation strategy. Lysine‐rich recombinant proteins are designed and massively biosynthesized to instantaneously react with aldehyde cross‐linkers to realize in situ strong adhesion. The obtained bioadhesives show an ultra‐high adhesion strength of ≈101.6 kPa on porcine skin, outperforming extant clinical bioglues. In addition, they possess super biocompatibility, flexibility, biodegradability, and compliance with the tissues. Owing to the strong and instantaneous adhesion properties, the bioadhesives are qualified for dynamic wound closure, facilitating wound repair, and noncompressible hemorrhage. Importantly, they can be industrially encapsulated into custom‐made cartridge delivery tubes at low cost for clinical use. Therefore, biosynthetic bioadhesives have great potential for biological applications and are capable of scaling up to the industrial level for clinical transformation, which will be a successful paradigm for reforming existing clinical products.

Synthesis of robust underwater glues from common proteins via unfolding-aggregating strategy

Underwater adhesive proteins secreted by organisms greatly inspires the development of underwater glue. However, except for specific proteins such as mussel adhesive protein, barnacle cement proteins, curli protein and their related recombinant proteins, it is believed that abundant common proteins cannot be converted into underwater glue. Here, we demonstrate that unfolded common proteins exhibit high affinity to surfaces and strong internal cohesion via amyloid-like aggregation in water. Using bovine serum albumin (BSA) as a model protein, we obtain a stable unfolded protein by cleaving the disulfide bonds and maintaining the unfolded state by means of stabilizing agents such as trifluoroethanol (TFE) and urea. The diffusion of stabilizing agents into water exposes the hydrophobic residues of an unfolded protein and initiates aggregation of the unfolded protein into a solid block. A robust and stable underwater glue can thus be prepared from tens of common proteins. This strategy deciphers a general code in common proteins to construct robust underwater glue from abundant biomass.

Biodegradable Implants for Internal Fixation of Fractures and Accelerated Bone Regeneration

Bone fractures have always been a burden to patients due to their common occurrence and severe complications. Traditionally, operative treatments have been widely used in the clinic for implanting, despite the fact that they can only achieve bone fixation with limited stability and pose no effect on promoting tissue growth. In addition, the nondegradable implants usually need a secondary surgery for implant removal, otherwise they may block the regeneration of bones resulting in bone nonunion. To overcome the low degradability of implants and avoid multiple surgeries, tissue engineers have investigated various biodegradable materials for bone regeneration, whereas the significance of stability of long-term bone fixation tends to be neglected during this process. Combining the traditional orthopedic implantation surgeries and emerging tissue engineering, we believe that both bone fixation and bone regeneration are indispensable factors for a successful bone repair. Herein, we define such a novel idea as bone regenerative fixation (BRF), which should be the main future development trend of biodegradable materials.

Recombinant supercharged polypeptides for safe and efficient heparin neutralization

Heparin is a widely used anticoagulant agent in the clinic. After application, its anticoagulant effect must be reversed to prevent potential side effects. Protamine sulfate (PS) is the only clinically licensed antidote that has been used for this purpose in the last 80 years, which, however, provokes severe adverse effects, such as systemic hypotension and even death. Herein, we demonstrate the potential of supercharged polypeptides as a promising alternative for protamine sulfate. A series of supercharged polypeptides with multiple positive charges was recombinantly produced, and the heparin-neutralizing performance of the polypeptides was evaluated in comparison with PS. It was found that increasing the number of charges significantly enhanced the ability to neutralize heparin and resist the screening effect induced by salt. In particular, the polypeptide bearing 72 charges (K72) exhibited an excellent heparin-neutralizing behavior that was comparable to that of PS. Further in vivo studies revealed that the heparin-triggered bleeding was almost completely alleviated by K72 while a negligible toxic effect was observed. Therefore, such recombinant supercharged polypeptides might replace protamine sulfate as heparin-reversal agents.

Mimosa-Inspired Stimuli-Responsive Curling Bioadhesive Tape Promotes Peripheral Nerve Regeneration

Trauma often results in peripheral nerve injuries (PNIs). These injuries are particularly challenging therapeutically because of variable nerve diameters, slow axonal regeneration, infection of severed ends, fragility of the nerve tissue, and the intricacy of surgical intervention. Surgical suturing is likely to cause additional damage to peripheral nerves. Therefore, an ideal nerve scaffold should possess good biocompatibility, diameter adaptability, and a stable biological interface for seamless biointegration with tissues. Inspired by the curl of Mimosa pudica, this study aimed to design and develop a diameter-adaptable, suture-free, stimulated curling bioadhesive tape (SCT) hydrogel for repairing PNI. The hydrogel is fabricated from chitosan and acrylic acid-N-hydroxysuccinimide lipid via gradient crosslinking using glutaraldehyde. It closely matches the nerves of different individuals and regions, thereby providing a bionic scaffold for axonal regeneration. In addition, this hydrogel rapidly absorbs tissue fluid from the nerve surface achieving durable wet-interface adhesion. Furthermore, the chitosan-based SCT hydrogel loaded with insulin-like growth factor-I effectively promotes peripheral nerve regeneration with excellent bioactivity. This procedure for peripheral nerve injury repair using the SCT hydrogel is simple and reduces the difficulty and duration of surgery, thereby advancing adaptive biointerfaces and reliable materials for nerve repair.

Mussel Foot Protein Inspired Tape-Type Adhesive with Water-Responsive, High Conformal, Tough, and On-Demand Detachable Adhesion to Wet Tissue

Wet adhesion is highly demanded in noninvasive wound closure, tissue repair, and biomedical devices, but it is still a big challenge for developing biosafe and tough wet bioadhesives due to low or even nonadhesion in the wet state for conventional adhesives. Inspired by the wet-adhesion-contributing factors of mussel foot proteins, a water-responsive dry robust tissue adhesive PAGU tape is made with thickness of <0.5 mm through fast UV-initiated copolymerization of acrylic acid (AA), gelatin (Gel), and hexadecenyl-1,2-catechol (UH). The tape shows strong cohesive mechanical properties and strong interfacial adhesion bonds. Upon application onto wet tissue, the adhesive tape can conform to the tissue, quickly dry tissue surface through absorbing surface/interfacial water and then allows formation of interfacial bonding with a high interfacial toughness of ≈818 J m-2 . Furthermore, it can be readily detached by treating with aq. urea solution. A highly efficient avenue is provided here for producing conformable, tough, and easy detachable wet bioadhesive tapes.

Engineered protein and Jakinib nanoplatform with extraordinary rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is a relatively common inflammatory disease that affects the synovial tissue, eventually results in joints destruction and even long-term disability. Although Janus kinase inhibitors (Jakinibs) show a rapid efficacy and are becoming the most successful agents in RA therapy, high dosing at frequent interval and severe toxicities cannot be avoided. Here, we developed a new type of fully compatible nanocarriers based on recombinant chimeric proteins with outstanding controlled release of upadacitinib. In addition, the fluorescent protein component of the nanocarriers enabled noninvasive fluorescence imaging of RA lesions, thus allowing real-time detection of RA therapy. Using rat models, the nanotherapeutic is shown to be superior to free upadacitinib, as indicated by extended circulation time and sustained bioefficacy. Strikingly, this nanosystem possesses an ultralong half-life of 45 h and a bioavailability of 4-times higher than pristine upadacitinib, thus extending the dosing interval from one day to 2 weeks. Side effects such as over-immunosuppression and leukocyte levels reduction were significantly mitigated. This smart strategy boosts efficacy, safety and visuality of Jakinibs in RA therapy, and potently enables customized designs of nanoplatforms for other therapeutics.

Electronic Supplementary Material

Supplementary material (further details of DLS analysis, biocompatibility of PCP-UPA, CIA models construction, etc.) is available in the online version of this article at 10.1007/s12274-023-5838-0.

Lyophilized Platelet-Rich Fibrin Exudate-Loaded Carboxymethyl Chitosan/GelMA Hydrogel for Efficient Bone Defect Repair

Platelet-rich fibrin (PRF) is an autologous growth factor carrier that promotes bone tissue regeneration, but its effectiveness is restrained by poor storage capabilities, uncontrollable concentration of growth factors, unstable shape, etc. Herein, we developed a photocrosslinkable composite hydrogel by incorporating lyophilized PRF exudate (LPRFe) into the carboxymethyl chitosan methacryloyl (CMCSMA)/gelatin methacryloyl (GelMA) hydrogel to effectively solve the dilemma of PRF. The hydrogel possessed suitable physical properties and sustainable release ability of growth factors in LPRFe. The LPRFe-loaded hydrogel could improve the adhesion, proliferation, migration, and osteogenic differentiation of rat bone mesenchymal stem cells (BMSCs). Furthermore, the animal experiments demonstrated that the hydrogel possessed excellent biocompatibility and biodegradability, and the introduction of LPRFe in the hydrogel can effectively accelerate the bone healing process. Conclusively, the combination of LPRFe with CMCSMA/GelMA hydrogel may be a promising therapeutic approach for bone defects.

An Adhesive/Anti-Adhesive Janus Tissue Patch for Efficient Closure of Bleeding Tissue with Inhibited Postoperative Adhesion

Most of the current bioadhesives cannot perform well on bleeding tissues while postoperative adhesion is a general but serious clinical issue. Here, a three-layer biodegradable Janus tissue patch (J-TP) that is able to simultaneously enable efficient closure of bleeding wounds with significantly promoted clotting ability and suppressed postoperative adhesion of tissues is reported. A dry adhesive hydrogel bottom layer of the J-TP can form rapid (within 15 s) and strong (tensile strength up to 98 kPa) adhesion to bleeding/wet tissues with high bursting pressure (about 312.5 mmHg on a sealed porcine skin) through hydrogen binding and covalent conjugation between the carboxyl & N-hydroxy succinimide (NHS) groups of hydrogel and the primary amine groups of tissues, while the phosphonic motifs can significantly reduce blood loss (by 81% on a rat bleeding liver model) of bleeding wounds. A thin polylactic acid (PLA) middle layer can improve the tensile strength (by 132%) of the J-TP in wet conditions while the grafted zwitterionic polymers can effectively prevent postoperative tissue adhesion and inflammatory reaction. This J-TP may be a promising tissue patch to assist the clinical treatment of injured bleeding tissues with inhibited postoperative adhesion.

Liquid sculpture and curing of bio-inspired polyelectrolyte aqueous two-phase systems

Aqueous two-phase systems (ATPS) provide imperative interfaces and compartments in biology, but the sculpture and conversion of liquid structures to functional solids is challenging. Here, inspired by phase evolution of mussel foot proteins ATPS, we tackle this problem by designing poly(ionic liquids) capable of responsive condensation and phase-dependent curing. When mixed with poly(dimethyl diallyl ammonium chloride), the poly(ionic liquids) formed liquid condensates and ATPS, which were tuned into bicontinuous liquid phases under stirring. Selective, rapid curing of the poly(ionic liquids)-rich phase was facilitated under basic conditions (pH 11), leading to the liquid-to-gel conversion and structure sculpture, i.e., the evolution from ATPS to macroporous sponges featuring bead-and-string networks. This mechanism enabled the selective embedment of carbon nanotubes in the poly(ionic liquids)-rich phase, which showed exceptional stability in harsh conditions (10 wt% NaCl, 80 ^oC, 3 days) and high (2.5 kg/m²h) solar thermal desalination of concentrated salty water under 1-sun irradiation.