Ultra-strong bio-glue from genetically engineered polypeptides

Bioglues Based on an Elastin-Like Recombinamer: Effect of Tannic Acid as an Additive on Tissue Adhesion and Cytocompatibility

More than 260 million surgical procedures are performed worldwide each year. Although sutures and staples are widely used to reconnect tissues, they can cause further damage and increase the risk of infection. Bioadhesives have been proposed as an alternative to reconnect tissues. However, clinical adhesives that combine strong adhesion with cytocompatibility have yet to be developed. In this study, we explored the production of adhesives based on protein-engineered polymers bioinspired by the sequence of elastin (i.e., elastin-like recombinamers, ELRs). We hypothesized that the combination of polyphenols (i.e., tannic acid, TA) and ELRs would produce an adhesive coacervate (ELR+TA), as reported for other protein polymers such as silk fibroin (SF). Notably, the adhesion of ELR alone surpassed that of ELR+TA. Indeed, ELR alone achieved adhesive strengths of 88.8 ± 33.2 kPa and 17.0 ± 2.0 kPa on porcine bone and skin tissues, respectively. This surprising result led us to explore a multicomponent bioadhesive to encompass the complementary roles of elastin (mimicked here by ELR) and silk fibroin (SF), and subsequently mirror more closely the multicomponent nature of the extracellular matrix. Tensile testing showed that ELR+SF achieved an adhesive strength of 123.3 ± 60.2 kPa on porcine bone and excellent cytocompatibility. To express this in a more visual and intuitive way, a small surface of only 2.5 cm2 was able to lift at least 2 kg of weight. This opens the door for further studies focusing on the ability of protein-engineered polymers to adhere to biological tissues without further chemical modification for applications in tissue engineering.

Fracture Detection in Bio-Glues with Fluorescent-Protein-Based Optical Force Probes

Glues are being used to bond, seal, and repair in industry and biomedicine. The improvement of gluing performance is hence important for the development of new glues with better and balanced property spaces, which in turn necessitates a mechanistic understanding of their mechanical failure. Optical force probes (OFPs) allow the observation of mechanical material damage in polymers from the macro- down to the microscale, yet have never been employed in glues. Here, the development of a series of ratiometric OFPs based on fluorescent-protein-dye and protein-protein conjugates and their incorporation into genetically engineered bio-glues is reported. The OFPs are designed to efficiently modulate Förster resonance energy transfer upon force application thereby reporting on force-induced molecular alterations independent of concentration and fluorescence intensity both spectrally and through their fluorescence lifetime. By fluorescence spectroscopy in solution and in the solid state and by fluorescence lifetime imaging microscopy, stress concentrations are visualized and adhesive and cohesive failure in the fracture zone is differentiated.

Lipidation Alters the Structure and Hydration of Myristoylated Intrinsically Disordered Proteins

Lipidated proteins are an emerging class of hybrid biomaterials that can integrate the functional capabilities of proteins into precisely engineered nano-biomaterials with potential applications in biotechnology, nanoscience, and biomedical engineering. For instance, fatty-acid-modified elastin-like polypeptides (FAMEs) combine the hierarchical assembly of lipids with the thermoresponsive character of elastin-like polypeptides (ELPs) to form nanocarriers with emergent temperature-dependent structural (shape or size) characteristics. Here, we report the biophysical underpinnings of thermoresponsive behavior of FAMEs using computational nanoscopy, spectroscopy, scattering, and microscopy. This integrated approach revealed that temperature and molecular syntax alter the structure, contact, and hydration of lipid, lipidation site, and protein, aligning with the changes in the nanomorphology of FAMEs. These findings enable a better understanding of the biophysical consequence of lipidation in biology and the rational design of the biomaterials and therapeutics that rival the exquisite hierarchy and capabilities of biological systems.

Topical Delivery of Cell-Penetrating Peptide-Modified Human Growth Hormone for Enhanced Wound Healing

Protein drugs have been emerging as a class of promising therapeutics. However, their topical application has been limited by their high molecular weight and poor permeability to the cell membrane. In this study, we aimed to enhance human growth hormone (hGH) permeability for topical application by conjugation of TAT peptide, a cell-penetrating peptide, to hGH via crosslinker. After TAT was conjugated to hGH, TAT-hGH was purified by affinity chromatography. TAT-hGH significantly increased cell proliferation compared with the control. Interestingly, the effect of TAT-hGH was higher than hGH at the same concentration. Furthermore, the conjugation of TAT to hGH enhanced the permeability of TAT-hGH across the cell membrane without affecting its biological activity in vitro. In vivo, the topical application of TAT-hGH into scar tissue markedly accelerated wound healing. Histological results showed that TAT-hGH dramatically promoted the re-epithelialization of wounds in the initial stage. These results demonstrate TAT-hGH as a new therapeutic potential drug for wound healing treatment. This study also provides a new method for topical protein application via enhancement of their permeability.

Construction of adhesive and bioactive silk fibroin hydrogel for treatment of spinal cord injury

Spinal cord injury (SCI) often causes severe and permanent disabilities due to the complexity of injury progression. The promising methods are generally based on tissue engineering technology using biocompatible hydrogels to achieve SCI repair. However, hydrogels are commonly incapable of close contact with the damaged spinal cord stumps and fail to support neural regeneration in SCI. Therefore, it is still a challenge to achieve stable contact with the transected nerve stumps and accelerate neural regeneration in the lesion microenvironment. Here, an in situ forming glycidyl methacrylated silk fibroin/ laminin-acrylate (SF-GMA/LM-AC) hydrogel was fabricated for SCI repair. The polymer chains formed a network quickly after ultraviolet (UV)-light trigger, in topological entanglement with the spinal cord, stitching the hydrogel and wet tissues together like a suture at the molecular scale. The SF-GMA/LM-AC hydrogel also provided a favorable environment for the growth of cells due to the incorporation of LM-AC. Compared with physical entrapment of LM, LM-AC immobilized in the hydrogel by covalent technology provided better microenvironments for neural stem cells (NSCs) growth. The repair of complete transection SCI in rats demonstrated that this hydrogel guided and promoted neural regeneration over 8 weeks, leading to hind limb locomotion recovery. This adhesive and bioactive SF-GMA/LM-AC hydrogel may open many opportunities in various therapeutic indications, including SCI. STATEMENT OF SIGNIFICANCE: Many materials have been developed for building transplanted scaffolds, but it is still a challenge to fabricate bioactive scaffolds and adhesion to wet tissues. In this study, we successfully developed an in situ forming SF-GMA/LM-AC hydrogel for SCI repair. This in situ forming hydrogel formed significant adhesion to the native spinal cord, stitching hydrogel and tissue together like a suture at the molecular scale. In addition, covalent immobilized LM-AC was used as the contact guidance biochemical cues for axonal outgrowth and had much better bioactive effects than physically entangled LM. Moreover, this universal strategy would open an avenue to fabricate adhesive and bioactive hydrogel for various disease treatments including SCI.

Facile preparation of polyphenol-crosslinked chitosan-based hydrogels for cutaneous wound repair

The design and facile preparation of the smart hydrogel wound dressings with inherent excellent antioxidant and antibacterial capacity to effectively promote wound healing processes is highly desirable in clinical applications. Herein, a series of multifunctional hydrogels were prepared by the dynamic Schiff base and boronate ester crosslinking among phenylboronic acid (PBA) grafted carboxymethyl chitosan (CMCS), polyphenols and Cu²⁺-crosslinked polyphenol nanoparticles (CuNPs). The dynamic crosslinking bonds endowed hydrogels with excellent self-healing and degradable properties. Three polyphenols including tannic acid (TA), oligomeric proanthocyanidins (OPC) and (-)-epigallocatechin-3-O-gallate (EGCG) contributed to the outstanding antibacterial and antioxidant abilities of these hydrogels. The tissue adhesive capacity of hydrogels gave them good hemostatic effect. Through a full-thickness skin defect model of mice, these biocompatible hydrogels could accelerate wound healing processes by promoting granulation tissue formation, collagen deposition, M2 macrophage polarization and cytokine secretion, demonstrating that these natural-derived hydrogels with inherent physiological properties and low-cost preparation approaches could be promising dressing materials.

Interfacial Instability-Induced (3I) Adhesives through "Mediator" Solvent Diffusion for Robust Underoil Adhesion

Underoil adhesives are intensively needed in case of oil spill caused by pipeline rupture, but remain a challenge owing to the obstruction of oil layer or their swelling in oil. Herein, a general solvent diffusion principle is demonstrated by introducing dual-soluble "mediator" solvents to develop a new type of interfacial instability-induced (3I) adhesives, achieving effective underoil adhesion on various substrates and blocking the oil leakage within seconds. Microscopic characterization reveals a fast and dynamic solvent exchange process that destroys the oil layer by liquid-liquid interfacial diffusion between the "mediator" solvent and oil, enabling 3I adhesives to contact the solid surfaces directly. The principle of interfacial instability-induced liquid replacement is quite different from typical immiscible liquid replacement and is not restricted by the surface tension of solvents, surface energy, and roughness of solid surfaces, successfully directing the construction of a series of effective 3I adhesives with commercially available feedstocks. This study provides a unique clue for the design of next-generation adhesives in complex environments.

Bionic Engineered Protein Coating Boosting Anti-Biofouling in Complex Biological Fluids

Implantable medical devices have been widely applied in diagnostics, therapeutics, organ restoration, and other biomedical areas, but often suffer from dysfunction and infections due to irreversible biofouling. Inspired by the self-defensive "vine-thorn" structure of climbing thorny plants, a zwitterion-conjugated protein is engineered via grafting sulfobetaine methacrylate (SBMA) segments on native bovine serum albumin (BSA) protein molecules for surface coating and antifouling applications in complex biological fluids. Unlike traditional synthetic polymers of which the coating operation requires arduous surface pretreatments, the engineered protein BSA@PSBMA (PolySBMA conjugated BSA) can achieve facile and surface-independent coating on various substrates through a simple dipping/spraying method. Interfacial molecular force measurements and adsorption tests demonstrate that the substrate-foulant attraction is significantly suppressed due to strong interfacial hydration and steric repulsion of the bionic structure of BSA@PSBMA, enabling coating surfaces to exhibit superior resistance to biofouling for a broad spectrum of species including proteins, metabolites, cells, and biofluids under various biological conditions. This work provides an innovative paradigm of using native proteins to generate engineered proteins with extraordinary antifouling capability and desired surface properties for bioengineering applications.

An Instant Underwater Tissue Adhesive Composed of Catechin-Chondroitin Sulfate and Cholesterol-Polyethyleneimine

Due to the safety issue and poor underwater adhesion of current commercially available bioadhesives, they are hard to apply to in vivo physiological environments and more diverse medical use conditions. In this study, a novel and facile bioadhesive for underwater medical applications are designed based on the coacervation of electrostatic interactions and hydrophobic interactions, with the introduction of catechin as a provider of catechol moieties for adhesion to surrounding tissues. The orange-colored bio-adhesive, named PcC, is generated within seconds by mixing catechin-modified chondroitin sulfate and cholesterol chloroformate-modified polyethyleneimine with agitation. In vitro mechanical measurements prove that this novel PcC bio-adhesive is superior in underwater adhesion performance when applied to cartilage. Animal experiments in a rat mastectomy model and rat cartilage graft implantation model demonstrate its potential for diverse medical purposes, such as closing surgical incisions, reducing the formation of seroma, and tissue adhesive applied in orthopedic or cartilage surgery.

Water-Processable, Stretchable, and Ion-Conducting Coacervate Fibers from Keratin Associations with Polyelectrolytes

Keratin is one of the most abundant biopolymers, produced on a scale of millions of tons per year but often simply discarded as waste. Due to its abundance, biocompatibility, and excellent mechanical properties, there is an extremely high interest in developing protocols for the recycling of keratin and its conversion into protein-based materials. In this work, we describe a novel protocol for the conversion of keratin from wool into hybrid fibers. Our protocol uses a synthetic polyanion, which undergoes complex coacervation with keratin, leading to a viscous liquid phase that can be used directly as a dope for dry-spinning. The use of polyelectrolyte complexation allows us to use all of the extracted keratin, unlike previous works that were limited to the fraction with the highest molecular weight. The fibers prepared by this protocol show excellent mechanical properties, humidity responsiveness, and ion conductivity, which makes them promising candidates for applications as a strain sensor.

Multifunctional 3D platforms for rapid hemostasis and wound healing: Structural and functional prospects at biointerfaces

354Fabrication of multifunctional hemostats is indispensable against chronic blood loss and accelerated wound healing. Various hemostatic materials that aid wound repair or rapid tissue regeneration has been developed in the last 5 years. This review provides an overview of the three-dimensional (3D) hemostatic platforms designed through the latest technologies like electrospinning, 3D printing, and lithography, solely or in combination, for application in rapid wound healing. We critically discuss the pivotal role of micro/nano-3D topography and biomaterial properties in mediating rapid blood clots and healing at the hemostat-biointerface. We also highlight the advantages and limitations of the designed 3D hemostats. We anticipate that this review will guide the fabrication of smart hemostats of the future for tissue engineering applications.

Molecularly Engineered Protein Glues with Superior Adhesion Performance

Naturally inspired proteins are investigated for the development of bioglues that combine adhesion performance and biocompatibility for biomedical applications. However, engineering such adhesives by rational design of the proteins at the molecular level is rarely reported. Herein, it is shown that a new generation of protein-based glues is generated by supramolecular assembly through de novo designed structural proteins in which arginine triggers robust liquid-liquid phase separation. The encoded arginine moieties significantly strengthen multiple molecular interactions in the complex, leading to ultrastrong adhesion on various surfaces, outperforming many chemically reacted and biomimetic glues. Such adhesive materials enable quick visceral hemostasis in 10 s and outstanding tissue regeneration due to their robust adhesion, good biocompatibility, and superior antibacterial capacity. Remarkably, their minimum inhibitory concentrations are orders of magnitude lower than clinical antibiotics. These advances offer insights into molecular engineering of de novo designed protein glues and outline a general strategy to fabricate mechanically strong protein-based materials for surgical applications.

Debonding-On-Demand Polymeric Wound Patches for Minimal Adhesion and Clinical Communication

Herein, a multifunctional bilayer wound patch is developed by integrating a debonding-on-demand polymeric tissue adhesive (DDPTA) with an ionic conducting elastomer (ICE). As a skin adhesive layer, the DDPTA is soft and adherent at skin temperature but hard and non-tacky when cooled, so it provides unique temperature-triggered quick adhesion and non-forced detachment from the skin. During use, the dense surface of the DDPTA prevents blood infiltration and reduces unnecessary blood loss with gentle pressing. Moreover, its hydrophobic matrix helps to repel blood and prevents the formation of clots, thus precluding wound tearing during its removal. This unique feature enables the DDPTA to avoid the severe deficiencies of hydrophilic adhesives, providing a reliable solution for a wide range of secondary wound injuries. The DDPTA is versatile in that it can be covered with ICE to configure a DDPTA@ICE patch for initiating non-verbal communication systems by the fingers, leading toward sign language recognition and a remote clinical alarm system. This multifunctional wound patch with debonding-on-demand can promote a new style of tissue sealant for convenient clinical communication.

John J, Khademhosseini A. Recent advances in biopolymer-based hemostatic materials

Hemorrhage is the leading cause of trauma-related deaths, in hospital and prehospital settings. Hemostasis is a complex mechanism that involves a cascade of clotting factors and proteins that result in the formation of a strong clot. In certain surgical and emergency situations, hemostatic agents are needed to achieve faster blood coagulation to prevent the patient from experiencing a severe hemorrhagic shock. Therefore, it is critical to consider appropriate materials and designs for hemostatic agents. Many materials have been fabricated as hemostatic agents, including synthetic and naturally derived polymers. Compared to synthetic polymers, natural polymers or biopolymers, which include polysaccharides and polypeptides, have greater biocompatibility, biodegradability and processibility. Thus, in this review, we focus on biopolymer-based hemostatic agents of different forms, such as powder, particles, sponges and hydrogels. Finally, we discuss biopolymer-based hemostatic materials currently in clinical trials and offer insight into next-generation hemostats for clinical translation.

Combination wound healing using polymer entangled porous nanoadhesive hybrids with robust ROS scavenging and angiogenesis properties

Nanoadhesives can achieve tight wound closure by connecting biomacromolecules from both sides. However, previously developed adhesive systems suffered from suboptimal wound healing efficiency due to the lack of interparticle cohesion, sufficient reactive oxygen species (ROS)-scavenging sites, and angiogenesis consideration. Herein, we developed a polymer entangled porous nanoadhesive system to address the above challenge by synergy of three functional components. Firstly, hybrid mesoporous silica nanoparticles with highly integrated polydopamine (MS-PDA) were prepared by templated synthesis. The entangling between PVA polymer and MS-PDA contributed to much stronger cohesion between nanoparticles, which led to 75% larger adhesion strength. As confirmed by in vitro and in vivo evaluations, the highly exposed catechol groups boosted the scavenging activity of ROS (1.8-4.1 fold enhancement as compared with nonporous counterpart). Consequently, more macrophages exhibited anti-inflammatory phenotype, leading to 2-2.6 fold lower pro-inflammatory cytokine levels. Moreover, the sustained release of bioactive SiO₄^4- by the disintegration of nanoparticles contributed to ∼3-fold higher expression of VEGF and enhanced new blood vessel formation, as well as better wound repair. This platform can provide a new paradigm for developing multifunctional nanoadhesive systems in treating skin wounds. STATEMENT OF SIGNIFICANCE: PVA polymer entangled mesoporous nanoadhesives of polydopamine (PDA)/silica hybrids with the combination of excellent wound closure effect, boosted ROS-scavenging activity, and significant angiogenesis ability were developed for improving the suboptimal skin wound healing efficiency. This strategy not only greatly advances our ability to rationally integrate repairing elements in nanoadhesives for manipulating combined processes of interfacial events during wound healing, but also offers general implications toward application of polymers to reinforce the adhesion strength in nanoadhesive systems. In addition, our findings on the impacts of pore effects mediated ROS species conversion and polymer entanglement may also trigger great interests and facilitate the development/broad application of therapeutic adhesives.

Long-Lasting Proteinaceous Nanoformulation for Tumor Imaging and Therapy

Nanodrugs have attracted increasing interest in drug delivery and disease treatment. However, the cumbersome preparation process and the poor biocompatibility of nanodrugs obstruct their clinical translation. In this study, we utilized a self-assembly strategy to develop a low-toxicity, long-lasting nanodrug for the effective treatment and real-time monitoring of bladder tumors. The accurate self-assembly of compatible raw materials allowed for an encapsulation rate of 43.7% for insoluble erdafitinib. Interestingly, robust therapeutic effects and reduced side effects could be realized simultaneously using this nanodrug, enabling broader scenarios for the clinical application of erdafitinib. Furthermore, the nanodrug exhibited a significantly prolonged in vivo half-life (14.4 h) and increased bioavailability (8.0 μg/mL·h), which were 8.3 times and 5.0 times higher than those of its nonformulated counterpart. Also, it is worth mentioning that the introduction of a fluorescent protein module into the nanodrug brought up a novel possibility for real-time feedback on the therapeutic response. In conclusion, this research revealed a versatile technique for developing low-toxicity, long-acting, and multifunctional nanoformulations, paving the way for multidimensional therapy of malignant tumors.

Small-molecule ionic liquid-based adhesive with strong room-temperature adhesion promoted by electrostatic interaction

Low-molecular-weight adhesives (LMWAs) possess many unique features compared to polymer adhesives. However, fabricating LMWAs with adhesion strengths higher than those of polymeric materials is a significant challenge, mainly because of the relatively weak and unbalanced cohesion and interfacial adhesion. Herein, an ionic liquid (IL)-based adhesive with high adhesion strength is demonstrated by introducing an IL moiety into a Y-shaped molecule replete with hydrogen bonding (H-bonding) interactions. The IL moieties not only destroyed the rigid and ordered H-bonding networks, releasing more free groups to form hydrogen bonds (H-bonds) at the substrate/adhesive interface, but also provided electrostatic interactions that improved the cohesion energy. The synthesized IL-based adhesive, Tri-HT, could directly form thin coatings on various substrates, with high adhesion strengths of up to 12.20 MPa. Advanced adhesives with electrical conductivity, self-healing behavior, and electrically-controlled adhesion could also be fabricated by combining Tri-HT with carbon nanotubes.

Responsive and self-healing structural color supramolecular hydrogel patch for diabetic wound treatment

The treatment of diabetic wounds remains a great challenge for medical community. Here, we present a novel structural color supramolecular hydrogel patch for diabetic wound treatment. This hydrogel patch was created by using N-acryloyl glycinamide (NAGA) and 1-vinyl-1,2,4-triazole (VTZ) mixed supramolecular hydrogel as the inverse opal scaffold, and temperature responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel loaded with vascular endothelial cell growth factor (VEGF) as a filler. Supramolecular hydrogel renders hydrogel patch with superior mechanical properties, in which NAGA and VTZ also provide self-healing and antibacterial properties, respectively. Besides, as the existence of PNIPAM, the hydrogel patch was endowed with thermal-responsiveness property, which could release actives in response to temperature stimulus. Given these excellent performances, we have demonstrated that the supramolecular hydrogel patch could significantly enhance the wound healing process in diabetes rats by downregulating the expression of inflammatory factors, promoting collagen deposition and angiogenesis. Attractively, due to responsive optical property of inverse opal scaffold, the hydrogel patch could display color-sensing behavior that was suitable for the wound monitoring and management as well as guidance of clinical treatment. These distinctive features indicate that the presented hydrogel patches have huge potential values in biomedical fields.

Supramolecular Adhesive Materials with Antimicrobial Activity for Emerging Biomedical Applications

Traditional adhesives or glues such as cyanoacrylates, fibrin glue, polyethylene glycol, and their derivatives have been widely used in biomedical fields. However, they still suffer from numerous limitations, including the mechanical mismatch with biological tissues, weak adhesion on wet surfaces, biological incompatibility, and incapability of integrating desired multifunction. In addition to adaptive mechanical and adhesion properties, adhesive biomaterials should be able to integrate multiple functions such as stimuli-responsiveness, control-releasing of small or macromolecular therapeutic molecules, hosting of various cells, and programmable degradation to fulfill the requirements in the specific biological systems. Therefore, rational molecular engineering and structural designs are required to facilitate the development of functional adhesive materials. This review summarizes and analyzes the current supramolecular design strategies of representative adhesive materials, serving as a general guide for researchers seeking to develop novel adhesive materials for biomedical applications.

Coacervation between two positively charged poly(ionic liquid)s

Complex coacervates are usually formed through electrostatic attraction between oppositely charged polyelectrolytes, with a few of exceptions such as coacervates of like-charge proteins and polyelectrolytes, both in vivo and in vitro. Understanding of the preparation and mechanism of these coacervates is limited. Here we design a positively charged poly(ionic liquid) poly(1-vinyl-3-benzylimidazolium chloride) (PILben) that bears benzene rings in repeating units. Fluidic coacervates were prepared by mixing the PILben aqueous solution with a like-charge poly(ionic liquid) named poly(dimethyl diallyl ammonium chloride) (PDDA). The effects of polymer concentration, temperature and ionic strength in the PILben-PDDA coacervate were studied. Raman spectroscopy and two-dimensional ¹ H-¹³ C heteronuclear single quantum coherence (¹ H-¹³ C HSQC) characterizations verify that the coacervate formation benefits from the cation-π interaction between PILben and PDDA. This work provides principles and understandings of designing coacervates derived from like-charge poly(ionic liquids) with high charge density. This article is protected by copyright. All rights reserved.

BioAdhere: tailor-made bioadhesives for epiretinal visual prostheses

Introduction: Visual prostheses, i.e. epiretinal stimulating arrays, are a promising therapy in treating retinal dystrophies and degenerations. In the wake of a new generation of devices, an innovative method for epiretinal fixation of stimulator arrays is required. We present the development of tailor-made bioadhesive peptides (peptesives) for fixating epiretinal stimulating arrays omitting the use of traumatic retinal tacks. Materials and methods: Binding motifs on the stimulating array (poly[chloro-p-xylylene] (Parylene C)) and in the extracellular matrix of the retinal surface (collagens I and IV, laminin, fibronectin) were identified. The anchor peptides cecropin A (CecA), KH1, KH2 (author's initials) and osteopontin (OPN) were genetically fused to reporter proteins to assess their binding behavior to coated microtiter plates via fluorescence-based assays. Domain Z (DZ) of staphylococcal protein A was used as a separator to generate a bioadhesive peptide. Following ISO 10993 "biological evaluation of medical materials", direct and non-direct cytotoxicity testing (L-929 and R28 retinal progenitor cells) was performed. Lastly, the fixating capabilities of the peptesives were tested in proof-of-principle experiments. Results: The generation of the bioadhesive peptide required evaluation of the N- and C-anchoring of investigated APs. The YmPh-CecA construct showed the highest activity on Parylene C in comparison with the wildtype phytase without the anchor peptide. eGFP-OPN was binding to all four investigated ECM proteins (collagen I, laminin > collagen IV, fibronectin). The strongest binding to collagen I was observed for eGFP-KH1, while the strongest binding to fibronectin was observed for eGFP-KH2. The selectivity of binding was checked by incubating eGFP-CecA and eGFP-OPN on ECM proteins and on Parylene C, respectively. Direct and non-direct cytotoxicity testing of the peptide cecropin-A-DZ-OPN using L-929 and R28 cells showed good biocompatibility properties. Proof-of-concept experiments in post-mortem rabbit eyes suggested an increased adhesion of CecA-DZ-OPN-coated stimulating arrays. Conclusion: This is the first study to prove the applicability and biocompatibility of peptesives for the fixation of macroscopic objects.

Bioinspired Polypeptide Photonic Films with Tunable Structural Color

We report a new synthetic strategy of combining N-carboxyanhydride (NCA) chemistry and photonic crystals for the fabrication of polypeptide structural color films. Driven by surface-initiated ring-opening polymerization, the di-NCA derivative of l-cystine (Cys) is introduced to replicate the functionalized colloidal crystal templates and construct freestanding P(Cys) films with tunable structural color. Furthermore, the feasibility of preparing patterned polypeptide photonic films is demonstrated via template microfabrication. Because of the incorporation of l-glutamate (Glu) components, the P(Cys-co-Glu) co-polypeptide films are endowed with a visual color responsiveness toward pH changes. Additionally, the polypeptide photonic films show on-demand degradability. Given the large family of amino acid building blocks, this powerful and versatile approach paves the way for chemical derivatization of multifunctional peptide-based optical platforms.

Engineering High Strength and Super-Toughness of Unfolded Structural Proteins and their Extraordinary Anti-Adhesion Performance for Abdominal Hernia Repair

The utility of unfolded structural proteins with diverse sequences offers multiple potentials to create functional biomaterials. However, it is challenging to overcome their structural defects for the development of biological fibers with a combination of high strength and high toughness. Herein, robust fibers from a recombinant unfolded protein consisting of resilin and supercharged polypeptide are fabricated via wet-spinning approaches. Particularly, the highly ordered structures induced by supramolecular complexation significantly improve the fiber's mechanical performance. In contrast to chemical fibers with high strength and low toughness (or vice versa), the present fibers demonstrate exceptional high strength and super-toughness, showing a breaking strength of ≈550 MPa and a toughness of ≈250 MJ m^-3 , respectively, surpassing many polymers and artificial protein fibers. Remarkably, the outstanding biocompatibility and superior mechanical properties allow application of the constructed fiber patches for efficient abdominal hernia repair in rat models. In stark contrast to clinical patches, there is no observed tissue adhesion by this treatment. Therefore, this work provides a new type of engineered protein material for surgical applications.

Electrically Programmable Interfacial Adhesion for Ultrastrong Hydrogel Bonding

Adjustable interfacial adhesion is of great significance in smart-hydrogel-related engineering fields. This study presents an electroadhesion strategy for universal and ultrastrong hydrogel bonding with electrically programmable strength. An ionic hydrogel containing lithium ions is designed to achieve hydrated-ion-diffusion-mediated interfacial adhesion, where external electric fields are employed to precisely control spatiotemporal dynamics of the ion diffusion across ionic adhesion region (IAR). The hydrogel can realize a universal, ultrastrong, efficient, tough, reversible, and environmentally tolerant electroadhesion to diverse hydrogels, whose peak adhesion strength and interfacial adhesion toughness are as high as 1.2 MPa and 3750 J m^-2 , respectively. With a mechanoelectric coupling model, the dominant role of the hydrated ions in IAR played in the interfacial electroadhesion is further quantitatively revealed. The proposed strategy opens a door for developing high-performance adhesion hydrogels with electrically programmable functions, which are indispensable for various emerging fields like flexible electronics and soft robotics.

Tough, Instant, and Repeatable Adhesion of Self-Healable Elastomers to Diverse Soft and Hard Surfaces

Repeatability and high adhesion toughness are usually contradictory for common polymer adhesives. Repeatability requires temporary interactions between the adhesive and the substrate, while high adhesion toughness is usually achieved by permanent bonding. Integrating these two features into one adhesive system is still a daunting challenge. Here, the development of a series of viscoelastic elastomers composed of a soft and hard segment is reported, which exhibit tough, instant, yet repeatable adhesion to a variety of soft and hard surfaces. Such a combination of mutually exclusive properties is attributed to the synergy of high mobility of polymer chains and massive viscoelastic dissipation of the elastomers around the interface. By optimizing the relaxation time and mechanical dissipation, the resulting adhesives can achieve a tough yet repeatable adhesion toughness above 2000 J m^-2 , superior to the best-in-class commercial adhesives. Numerous acrylate monomers are proven applicable to the preparation of such adhesives, validating the universality of the fabrication method. The application of these elastomers as adhesive and protective layers in soft electronics by virtue of their universal and tough adhesion to various soft and hard substrates is also demonstrated.

An Engineered Protein-Au Bioplaster for Efficient Skin Tumor Therapy

Melanoma is the most lethal malignancy in skin cancer and may occur at any site and express melanocytes. Due to malignant melanoma's invasion and migration nature, conventional therapies make it challenging to remove the whole tumor tissue while undertaking the high risks of tumor recurrence. Regarding the emerging targeted therapies and immunotherapy, drug resistance and low immunotherapeutic activity remain significant challenges. It is thus becoming urgently important to develop alternative strategies for melanoma therapy. Herein, a novel bifunctional protein-based photothermal bioplaster (PPTB) is developed for non-invasive tumor therapy and skin tissue regeneration. The complexation of adhesive protein and gold nanorods (GNRs) endow the obtained PPTB with good biocompatibility, controllable near-infrared (NIR) light-mediated adhesion performance, and high photothermal performance. Therefore, the PPTB bioagent facilitates skin adhesion and effectively transfers heat from skin to tumor. This behavior endows PPTB capability to eradicate skin tumors conveniently. Thus, the assembly strategy enables this hybrid bioplaster to hold great potential for skin-related tumor treatment.

Biosynthetic Structural Proteins with Super Plasticity, Extraordinary Mechanical Performance, Biodegradability, Biocompatibility and Information Storage Ability

Degradable bioplastics have attracted growing interest worldwide. However, it is challenging to develop bioplastics with a simple processing procedure, strong mechanical performance, good biocompatibility, and adjustable physicochemical properties. Herein, we introduced structural proteins as building blocks and developed a simple environmentally friendly approach to fabricate diverse protein-based plastics. A cost-effective and high-level production approach was developed through batch fermentation of Escherichia coli to produce the biomaterials. These bioplastics possess super plasticity, biocompatibility, biodegradability, and high resistance to organic solvents. Their structural and mechanical properties can be precisely controlled. Besides, high density information storage and hemostatic applications were realized in the bioplastic system. The customizable bioplastics have great potential for applications in numerous fields and are capable to scale up to the industrial level.

Bioinspired Super-Strong Aqueous Synthetic Tissue Adhesives

Existing tissue adhesives and sealants are far from satisfactory when applied on wet and dynamic tissues. Herein, we report a strategy for designing biodegradable super-strong aqueous glue (B-Seal) for surgical uses inspired by an English ivy adhesion strategy and a cement particle packing theory. B-Seal is a fast-gelling, super-strong, and elastic adhesive sealant composed of injectable water-borne biodegradable polyurethane (WPU) nanodispersions with mismatched particle sizes and counterions in its A-B formulation. B-Seal showed 24-fold greater burst pressure than DuraSeal®, 138-fold greater T-pull adhesive strength than fibrin glue, and 16-fold greater lap shear strength than fibrin glue. In vivo evaluation on a rat cerebrospinal fluid (CSF) rhinorrhea model and a porcine craniotomy model validated the safety and efficacy of B-Seal for effective CSF leak prevention and dura repair. The plant-inspired adhesion strategy combined with particle packing theory represents a new direction of designing the next-generation wet tissue adhesives for surgeries.

Multifunctional Single-Component Polypeptide Hydrogels: The Gelation Mechanism, Superior Biocompatibility, High Performance Hemostasis, and Scarless Wound Healing

Polymeric hydrogels have been increasingly studied for wound sealants, adhesives, hemostats, and dressings, however, multi-component gelation, adhesion-causing tissue damage, inefficient hemostasis, and skin scarring in wound healing hamper their advances. So it is urgent to develop multifunctional single-component polymeric hydrogels with benign tissue detachment, high performance hemostasis, and scarless wound healing attributes. Herein, a dopamine-modified poly(l-glutamate) hydrogel at an ultralow concentration of 0.1 wt% is serendipitously constructed by physical treatments, in which a gelation mechanism is disclosed via oxidative catechol-crosslinking and sequential dicatechol-carboxyl hydrogen-bonding interactions. The covalent/H-bonding co-crosslinked and highly negative-charged networks enable the polypeptide hydrogels thermo-, salt-, urea-resistant, self-healing, injectable, and adhesive yet detachable. In vitro and in vivo assays demonstrate they have superior biocompatibility with ≈0.5% hemolysis and negligible inflammation. The polypeptide/graphene oxide hybrid hydrogel performs fast and efficient hemostasis of 12 s and 1.4% blood loss, surpassing some hydrogels and commercial counterparts. Remarkably, the polypeptide hydrogels achieve scarless and full wound healing and regenerate thick dermis with some embedded hair follicles within 14 days, presenting superior full-thickness wound healing and skin scar-preventing capabilities. This work provides a simple and practicable method to construct multifunctional polypeptide hemostatic and healing hydrogels that overcome some above-mentioned hurdles.

Hot Melt Super Glue: Multi-Recyclable Polyphenol-Based Supramolecular Adhesives

We report the rapid and facile synthesis of hot melt super glue (HMSG) via the formation of adhesive supramolecular networks between catechol or pyrogallol hydroxyl groups (-OH) of polyphenols and repeat units (-CH₂ CH₂ O-) of poly(ethylene glycol) (PEG) based on hydrogen bonds. The adhesion strength of HMSG, processed by heating-cooling of polyphenols and PEG without additional solvents, can be tuned up to 8.8 MPa via changing the molecular weight of PEG and the ratio of hydrogen bonding donors and receptors. The advantages of the reported HMSG lie in the ease and scalability of the assembly process, rapid adhesion on various substrates with excellent processability, resistance of low temperature and organic solvents, and recyclable adhesion strength. The solvent-free HMSG represents a promising adhesive supramolecular network to expand the versatility and application of polyphenol-based materials. This article is protected by copyright. All rights reserved.

Fabrication of adhesive hydrogels based on poly (acrylic acid) and modified hyaluronic acid

Hydrogel wound dressings with good flexibility and adhesiveness to resist deformation during wound movement are urgently needed in clinical application. In this work, the hydrogels based on poly (acrylic acid) and N-hydroxysuccinimide grafted hyaluronic acid (PAA/HA_-NHS) with good elasticity and adhesiveness were prepared by chemical cross-linking and hydrogen bonding. The elastic and adhesive properties within the PAA hydrogels could reach a balance by adjusting the concentration of potassium persulfate (KPS) and N, N'-methylenebisacrylamide (MBA). Subsequently, HA_-NHS was incorporated into the PAA hydrogel system. The mechanical test revealed that the elongation at break and interfacial toughness of the PAA/HA_-NHS hydrogels could reach 265.79 ± 21.93% and 52.88 ± 3.51 J/m², respectively. In addition, the hydrogels possess a connected porous network and well water absorption ability (with porosity of 51.90 ± 0.11% and swelling ratio in wet state of 122.17 ± 2.78%). In vitro experiment demonstrates that the PAA/HA_-NHS hydrogels exhibit nontoxic and cell in-adhesive properties. The PAA/HA_-NHS hydrogels could cover the wound spots directly, stretch with the skin movement and gently remove from the wound tissue due to the suitable adhesiveness and poor cell adhesion. In conclusion, the PAA/HA_-NHS hydrogels show great application value in the field of wound dressing.

Stimuli-Responsive Natural Proteins and Their Applications

Natural proteins are essential biomacromolecules that fulfill versatile functions in the living organism, such as their usage as cytoskeleton, nutriment transporter, homeostasis controller, catalyzer, or immune guarder. Due to the excellent mechanical properties and good biocompatibility/biodegradability, natural protein-based biomaterials are well equipped for prospective applications in various fields. Among these natural proteins, stimuli-responsive proteins can be reversibly and precisely manipulated on demand, rendering the protein-based biomaterials promising candidates for numerous applications, including disease detection, drug delivery, bio-sensing, and regenerative medicine. Therefore, we present some typical natural proteins with diverse physical stimuli-responsive properties, including temperature, light, force, electrical, and magnetic sensing in this review. The structure-function mechanism of these proteins is discussed in detail. Finally, we give a summary and perspective for the development of stimuli-responsive proteins.

Dopamine based adhesive nano-coatings on extracellular matrix (ECM) based grafts for enhanced host-graft interfacing affinity

Interfacing affinity between grafts and host tissues is an urgent issue that needs to be addressed for the clinical translation of tissue engineered extracellular matrix (ECM) based grafts. Dopamine is known as a universal adhesive, the catechol groups on which could form chelating bonds with metal ions. Herein we developed an adhesive nano-coating on ECM based grafts which could crosslink in situ with ferric ions for fixation with surrounding tissues after implantation without affecting the porous structures of the grafts. Therefore, decellularized living hyaline cartilage graft (dLhCG), a model ECM-based graft, with dopamine based natural biological material adhesive coatings was manufactured to address the interfacing affinity issue between ECM-based grafts and cartilage. A macromolecule backbone was needed for the coating material to avoid the formation of a rigid crosslinking system and adverse effects caused by small molecules of dopamine. Chondroitin sulfate (CS), a cartilage derived sulfated GAG, was chosen as the backbone to fabricate dopamine modified CS (CSD) with no impurities introduced to the joint. Dopamine modified serum albumin (BCD) was also chosen for the favorable biocompatibility of albumin. Both dLhCG coated with CSD and dLhCG coated with BCD showed enhanced adhesive strength with cartilage after chelating with ferric ions in situ compared to dLhCG and further potential in improving the interfacing affinity of dLhCG with cartilage.

Bioengineered Protein-based Adhesives for Biomedical Applications

Protein-based adhesives with their robust adhesion performance and excellent biocompatibility have been extensively explored over years. In particular, the unique adhesion behaviours of mussel and sandcastle worm inspired the development of synthetic adhesives. However, the chemical synthesized adhesives often demonstrate weak underwater adhesion performance and poor biocompatibility/biodegradability, limiting their further biomedical applications. In sharp contrast, genetically engineering endows the protein-based adhesives the ability to maintain underwater adhesion property as well as biocompatibility/biodegradability. Herein, we outline recent advances in the design and development of protein-based adhesives by genetic engineering. We summarize the fabrication and adhesion performance of elastin-like polypeptide-based adhesives, followed by mussel foot protein (mfp) based adhesives and other sources protein-based adhesives, such as, spider silk spidroin and suckerin. In addition, the biomedical applications of these bioengineered protein-based adhesives are presented. Finally, we give a brief summary and perspective on the future development of bioengineered protein-based adhesives.

Robust Antiwater and Anti-oil-fouling Double-Sided Tape Enabled by SiO2 Reinforcement and a Liquefied Surface

Realizing simultaneous antiwater and anti-oil-fouling adhesion is extremely challenging owing to the solvated overlayer on the surface of substrates. Herein, we develop a supertough polyacrylate-based tape bearing SiO₂ as a reinforcing filler and a solvent to liquefy the surface. The SiO₂ reinforcement enhances the cohesion strength, while the liquefied surface not only expels the solvated overlayer but also improves the interfacial wettability and interaction. This material design imparts the double-sided tape with admirable antiwater and anti-oil-fouling adhesion performance, which far exceeds that of commercial tapes, as well as high transparency and long-term stability. In addition, we carry out an in-depth study on the adhesive mechanism for the tape and clarify the role of the solvent and the interaction between SiO₂ and a polymer matrix. This work provides a novel strategy for designing antiwater and anti-oil-fouling adhesives with wide applications in various fields such as leakage repair, antiseep, underwater adhesion, building materials, and biological adhesives.