A strong quick-release biointerface in mussels mediated by serotonergic cilia-based adhesion

Transcriptomic and metabolomic analyses provide insights into the energy metabolism and signaling regulation of byssus secretion in winged pearl oyster Pteria penguin

The winged pearl oyster Pteria penguin has the unique stout byssus in comparison with other pearl oysters. However, the mechanism of the byssus secretion in this species has not been largely investigated. This study applied transcriptomic and metabolomic techniques to elucidate this mechanism. The results showed that 3420 differentially expressed genes (DEGs) were identified which were enriched in glycolysis/gluconeogenesis, pentose phosphate pathway, TCA cycle, fatty acid metabolism, mTOR signaling pathway, FoxO signaling pathway and Notch signaling pathway. The metabolomic analysis revealed that 135 significantly different metabolites (SDMs) were identified with 23 pathways involved, including pentose phosphate pathway, glutathione metabolism and amino acid metabolism. Comprehensive analysis of transcriptome and metabolome indicated that glycogen, fatty acid metabolism and protein conversion could be used interchangeably as energy sources. Moreover, the glutathione metabolism and immune response demonstrated the importance of cellular homeostasis for byssus secretion in the winged pearl oyster. Dynamic expression of 5-hydroxytryptamine, dopamine receptors and adenylate cyclase suggested that the foot may regulate byssus secretion through an aminergic neurofeedback system which could translate information into neurochemical signals. In conclusion, this study provided insights into the energy metabolism and signaling regulation of byssus secretion in winged pearl oyster by the transcriptomic and metabolomic analyses.

Mussel Foot Protein Membrane-Enclosed Crystalline Drug with Zero-Order Release Kinetics for Long-Acting Therapy

Injectable formulations with sustained and steady release capabilities are critically required to treat diseases requiring temporary or lifelong continuous therapy, especially for drugs with a short half-life. Additionally, achieving a sufficiently high drug loading in a single dose remains a persistent challenge. Herein, by mimicking the formation principles of mussel adhesive plaques, we have developed membrane-enclosed crystalline systems of insulin and progesterone as model macro- and small-molecular crystalline drugs. The system exhibits a substantial drug loading capacity (>90 %). It exhibits sustained and zero-order release kinetics, thereby facilitating the establishment of a subcutaneous reservoir containing a substantial drug load, enabling progressive and continuous release of the drug into the body. One single injection of membrane-enclosed insulin crystal can maintain normoglycemia in diabetic mice for up to 7 days. Meanwhile, membrane-coated progesterone crystals can sustain drug release in rats for over 7 days. The protein membrane can be cleared from the injection sites in 35 days. This system can serve as a versatile platform for the sustained release of various crystalline pharmaceuticals and the treatment of distinct diseases.

Reusable Liquid Metal-Based Hierarchical Hydrogels with Multifunctional Sensing Capability for Electrophysiology Electrode Substitution

Electrophysiological electrode patches are often used to collect surface electrophysiological signals to monitor and evaluate human health. However, commercial Ag/AgCl gels are very susceptible to electrode-skin interface interference during rehabilitation exercises and cannot achieve a stable collection of electrophysiological signals. In order to solve this challenge, this paper designed a liquid metal-based hierarchical hydrogel, which has a series of great performances, including adhesion to various substrates, efficient self-healing ability, excellent stretchability, and conductivity. Due to the hydrogel's unique rheological and adhesive properties, a conformal electrode/skin interface was generated, thus enabling stable electrophysiological signal acquisition during exercise. In addition, the strain sensor assembled based on the conductive hydrogel can sensitively monitor human limb movements in real time and can even be used for remote intelligent gesture recognition. Therefore, this work provides scientific guidance for developing a next generation of intelligent hydrogels with personal health surveillance, rehabilitation training monitoring, and wearable human-machine interaction.

The chromosomal-level genome assembly and annotation of pen shell Atrina pectinata

The pen shell Atrina pectinata is a bivalve recognized for its outstanding large adductor muscle and developed byssus. Now, it becomes threatened in East Asia, requiring special attention for artificial breeding to boost yield. However, the lack of high-quality genomes hinders our understanding of its reproductive biology, which resulting in the artificial breeding in pen shell is still a scientific technological problem. Here, we produced a high-quality chromosome-level genome assembly of A. pectinata combing the PacBio, Illumina, and high-resolution chromosome conformation capture sequencing. The final assembly has a size of 951.01 Mb with a scaffold N50 of 52.64 Mb, 98.87% of sequence was anchored onto 17 chromosomes, with a BUSCO evaluation integrity score of 98.8%. We successfully identified 29,326 protein-coding genes and 24,708 genes (84.25%) were functionally annotated. The BUSCO evaluation integrity score for the predicted protein-coding genes was 97.7%. This work promotes the applicability of the A. pectinata genome, laying a solid foundation for future investigations into genomics and biology within this species.

Interfacial Reinforcement of Polymer-Bonded Explosives by Grafting a Neutral Bonding Agent with Enhanced Mechanical Properties

The poor bonding of energetic crystals has severely influenced the comprehensive performance of explosive composites. Herein, surface modification is displayed as an effective method to implement the interaction of composites. In this work, a multipurpose functionalization of interfacial additives and biomimetic coating was demonstrated in facial and reproductive ways. The self-polymerization of dopamine (DA) formed polydopamine (PDA) shells, followed by neutral bonding agent (NBA) grafting, which led to a roughness change of the 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) crystal. The new bonds of amino ester (-NHCOO) were generated, proving the success of the "grafting to" strategy. The ability to resist deformation after surface modification was significantly improved with strain below 0.06% under 75 °C or 9 MPa. The storage modulus of PBX is above 4000 MPa within a temperature range of 20-120 °C. Moreover, the mechanical properties of PBX-3 significantly improved, with the strength and elongation in the Brazillian mechanical test increasing by 19.4 and 24.4%, respectively, ultimately resulting in an enhancement of approximately 51.6% in fracture work. The dual effect of hydrogen bonding and a physical anchor may serve to enhance mechanical properties. The approach of PDA coating and NBA grafting presented in this paper may be favorable for improving the mechanics of general composites.

Catechol redox maintenance in mussel adhesion

Catechol-functionalized proteins in mussel holdfasts are essential for underwater adhesion and cohesion and have inspired countless synthetic polymeric materials and devices. However, as catechols are prone to oxidation, long-term performance and stability of these inventions awaits effective antioxidation strategies. In mussels, catechol-mediated interactions are stabilized by 'built-in' homeostatic redox reservoirs that restore catechols oxidized to quinones. Mussel byssus has a typical 'core-shell' architecture in which the core is a degradable fibrous block copolymer consisting of collagen and fibroin coated by robust protein networks stabilized by bis-catecholato-metal and tris-catecholato-metal ion complexes. The coating is well-adapted to protect the core against abrasion, hydrolysis and microbial attack, but it is not impervious to oxidative damage, which, during function, is promptly repaired by redox poise via coacervated catechol-rich and thiol-rich reducing interlayers and inclusions. However, when the e- and H+ equivalents from these reducing reservoirs are depleted, coating damage accumulates, leading to exposure of the vulnerable core to environmental attack. Heeding and translating these strategies is essential for deploying catechols with longer service lifetimes and designing more sustainable next-generation polymeric adhesives.

Biomimetic Janus Particles Induced In Situ Interfacial Remineralization for Dentin Hypersensitivity

Dentin hypersensitivity (DH), caused by the exposure of dentin tubules, is a common complaint of dental patients. Although occlusion of the exposed tubules is the primary treatment approach, the complex oral environment, and multiple simultaneous requirements often hinder its implementation. In this study, strawberry‐shaped hemispheric Janus particles (JPs) are synthesized, and their use in the treatment of DH is evaluated in vitro and in an animal model. The hemispheric side of the JPs is modified with polymers of quaternary ammonium salts (QASs) to form a superhydrophobic coating with antibiofilm properties, while the flat side is modified with catechol groups able to form strong bonds with dentin. Even after 1 h of ultrasonication or 1000 rounds of thermal cycling, the dentin tubules are completely occluded by the JPs. Moreover, biofilm formation is not observed, and the area of living bacteria is less than 1% compared to the blank control and sodium fluoride (NaF)‐treated groups. In a rat model, the dentin tubules in the fixed specimens are completely occluded at day 3, much earlier than the occlusion obtained with commonly used NaF. These results demonstrate that JPs can provide a novel approach to the treatment of DH.

Chemo-Mechanical Due-Biomimetic Approach for Ultra-Stable Adsorption Across Multiple Scenarios

The unique adhesion capabilities of soft-bodied creatures such as leeches and octopuses have provided considerable inspiration for the development of artificial adhesive materials. However, previous studies have either focused on the design of sucker structures or concentrated on the synthesis of adhesive materials, with the combination of these two aspects not yet having been deeply investigated. In this study, inspired from leech's unique adsorption ability, a biomimetic approach is proposed that combined artificial sucker and mucus, to achieve remarkable adhesion stability on rough surfaces using 5 cm diameter silicone suction cups. Even on 40-mesh substrates, the mucus-coated suction cups maintained over 95% of their adhesion force compared to smooth surfaces. The formation of a liquid seal by the mucus at the suction cup edges effectively prevented gas leakage on rough substrates, thus ensuring stable adhesion. This experiments across various scenarios and real-world objects substantiated the stability and versatility of this strategy. In summary, a straightforward method is presented for achieving reliable adhesion with centimeter-scale suction cups, thereby unveiling new avenues for the development of commercially viable adhesion devices.

Biomimetic poly(thioctic acid)-based bioadhesive hydrogels for wet adhesion, expeditious hemostasis and enhanced wound healing

The bioadhesive hydrogels have been viewed as promising substitutes for surgical sutures in wound closure. However, current bioadhesives face challenges such as weak wet adhesion and hemostatic performance, which hinder their wider clinical application. In this study, a novel poly(thioctic acid)Li+/caffeic acid-grafted sericin (CAS) (PTALi-CAS) supramolecular hydrogel was prepared using facile one-pot method. Among the PTALi-CAS hydrogels with varying CAS content, the PTALi-7%CAS hydrogels exhibited the highest adhesion strength (32.02 ± 2.28 kPa) and could adhere on surfaces of various organs in moist environments. It is noteworthy that the microstructure of the PTALi-7%CAS hydrogels after stretching closely resemble those of mussel byssal adhesion proteins. Additionally, the PTALi-7%CAS hydrogels exhibited rapid hemostatic properties in rat hemorrhage models and significantly accelerated the wound healing in rat skin incision experiments. Therefore, this study proposes a promising approach for developing a versatile hydrogel to aid in healing traumatic wounds.

Robust Chiral Metal-Organic Framework Coatings for Self-Activating and Sustainable Biofouling Mitigation

Surface coatings are designed to mitigate pervasive biofouling herald, a new era of surface protection in complex biological environments. However, existing strategies are plagued by persistent and recurrent biofilm attachment, despite the use of bactericidal agents. Herein, a chiral metal-organic framework (MOF)-based coating with conformal microstructures to enable a new anti-biofouling mode that involves spontaneous biofilm disassembly followed by bacterial eradication is developed. A facile and universal metal-polyphenol network (MPN) is designed to robustly anchor the MOF nanoarmor of biocidal Cu2+ ions and anti-biofilm d-amino acid ligands to a variety of substrates across different material categories and surface topologies. Incorporating a diverse array of chiral amino acids endows the resultant coatings with widespread signals for biofilm dispersal, facilitating copper-catalyzed chemodynamic reactions and inherent mechano-bactericidal activities. This synergistic mechanism yields unprecedented anti-biofouling efficacy elucidated by RNA-sequencing transcriptomics analysis, enhancing broad-spectrum antibacterial activities, preventing biofilm formation, and destroying mature biofilms. Additionally, the chelation-directed amorphous/crystalline coatings can activate photoluminescent properties to inhibit the settlement of microalgae biofilms. This study provides a distinctive perspective on chirality-enhanced antimicrobial behaviors and pioneers a rational pathway toward developing next-generation anti-biofouling coatings for diverse applications.

Harnessing Biomimicry for Controlled Adhesion on Material Surfaces

Nature serves as an abundant wellspring of inspiration for crafting innovative adhesive materials. Extensive research is conducted on various complex forms of biological attachment, such as geckos, tree frogs, octopuses, and mussels. However, significant obstacles still exist in developing adhesive materials that truly replicate the behaviors and functionalities observed in living organisms. Here, an overview of biological organs, structures, and adhesive secretions endowed with adhesion capabilities, delving into the intricate relationship between their morphology and function, and potential for biomimicry are provided. First, the design principles and mechanisms of adhesion behavior and individual organ morphology in nature are summarized from the perspective of structural and size constraints. Subsequently, the value of engineered and bioinspired adhesive materials through selective application cases in practical fields is emphasized. Then, a forward-looking gaze on the conceivable challenges and associated opportunities in harnessing biomimetic strategies and biological materials for advancing adhesive material innovation is highlighted and cast.

Sequentially photocatalytic degradation of mussel-inspired polydopamine: From nanoscale disassembly to effective mineralization

Mussel-inspired polydopamine (PDA) coating has been utilized extensively as versatile deposition strategies that can functionalize surfaces of virtually all substrates. However, the strong adhesion, stability and intermolecular interaction of PDA make it inefficient in certain applications. Herein, a green and efficient photocatalytic method was reported to remove adhesion and degrade PDA by using TiO2-H2O2 as photocatalyst. The photodegradation process of the PDA spheres was first undergone nanoscale disassembly to form soluble PDA oligomers or well-dispersed nanoparticles. Most of the disassembled PDA can be photodegraded and finally mineralized to CO2 and H2O. Various PDA coated templates and PDA hollow structures can be photodegraded by this strategy. Such process provides a practical strategy for constructing the patterned and gradient surfaces by the "top-down" method under the control of light scope and intensity. This sequential degradation strategy is beneficial to achieve the decomposition of highly crosslinked polymers.

Nature-Inspired Wet Drug Delivery Platforms

Nature has created various organisms with unique chemical components and multi-scale structures (e.g., foot proteins, toe pads, suckers, setose gill lamellae) to achieve wet adhesion functions to adapt to their complex living environments. These organisms can provide inspirations for designing wet adhesives with mediated drug release behaviors in target locations of biological surfaces. They exhibit conformal and enhanced wet adhesion, addressing the bottleneck of weaker tissue interface adhesion in the presence of body fluids. Herein, it is focused on the research progress of different wet adhesion and bioinspired fabrications, including adhesive protein-based adhesion and inspired adhesives (e.g., mussel adhesion); capillarity and Stefan adhesion and inspired adhesive surfaces (e.g., tree frog adhesion); suction-based adhesion and inspired suckers (e.g., octopus' adhesion); interlocking and friction-based adhesion and potential inspirations (e.g., mayfly larva and teleost adhesion). Other secreted protein-induced wet adhesion is also reviewed and various suckers for other organisms and their inspirations. Notably, one representative application scenario of these bioinspired wet adhesives is highlighted, where they function as efficient drug delivery platforms on target tissues and/or organs with requirements of both controllable wet adhesion and optimized drug release. Finally, the challenges of these bioinspired wet drug delivery platforms in the future is presented.

Hydrogel Coatings of Implants for Pathological Bone Repair

Hydrogels are well-suited for biomedical applications due to their numerous advantages, such as excellent bioactivity, versatile physical and chemical properties, and effective drug delivery capabilities. Recently, hydrogel coatings have developed to functionalize bone implants which are biologically inert and cannot withstand the complex bone tissue repair microenvironment. These coatings have shown promise in addressing unique and pressing medical needs. This review begins with the major functionalized performance and interfacial bonding strategy of hydrogel coatings, with a focus on the novel external field response properties of the hydrogel. Recent advances in the fabrication strategies of hydrogel coatings and their use in the treatment of pathologic bone regeneration are highlighted. Finally, challenges and emerging trends in the evolution and application of physiological environment-responsive and external electric field-responsive hydrogel coatings for bone implants are discussed.

An Ultra-Conductive and Patternable 40 nm-Thick Polymer Film for Reliable Emotion Recognition

Understanding psychology is an important task in modern society which helps predict human behavior and provide feedback accordingly. Monitoring of weak psychological and emotional changes requires bioelectronic devices to be stretchable and compliant for unobtrusive and high-fidelity signal acquisition. Thin conductive polymer film is regarded as an ideal interface; however, it is very challenging to simultaneously balance mechanical robustness and opto-electrical property. Here, a 40 nm-thick film based on photolithographic double-network conductive polymer mediated by graphene layer is reported, which concurrently enables stretchability, conductivity, and conformability. Photolithographic polymer and graphene endow the film photopatternability, enhance stress dissipation capability, as well as improve opto-electrical conductivity (4458 S cm-1@>90% transparency) through molecular rearrangement by π-π interaction, electrostatic interaction, and hydrogen bonding. The film is further applied onto corrugated facial skin, the subtle electromyogram is monitored, and machine learning algorithm is performed to understand complex emotions, indicating the outstanding ability for stretchable and compliant bioelectronics.

What Exactly Can Bionic Strategies Achieve for Flexible Sensors?

Flexible sensors have attracted great attention in the field of wearable electronic devices due to their deformability, lightness, and versatility. However, property improvement remains a key challenge. Fortunately, natural organisms exhibit many unique response mechanisms to various stimuli, and the corresponding structures and compositions provide advanced design ideas for the development of flexible sensors. Therefore, this Review highlights recent advances in sensing performance and functional characteristics of flexible sensors from the perspective of bionics for the first time. First, the "twins" of bionics and flexible sensors are introduced. Second, the enhancements in electrical and mechanical performance through bionic strategies are summarized according to the prototypes of humans, plants, and animals. Third, the functional characteristics of bionic strategies for flexible sensors are discussed in detail, including self-healing, color-changing, tangential force, strain redistribution, and interfacial resistance. Finally, we summarize the challenges and development trends of bioinspired flexible sensors. This Review aims to deepen the understanding of bionic strategies and provide innovative ideas and references for the design and manufacture of next-generation flexible sensors.

Hyposalinity stress reduces mussel byssus secretion but does not cause detachment

Environmental stressors such as salinity fluctuations can significantly impact the ecological dynamics of mussel beds. The present study evaluated the influence of hyposalinity stress on the detachment and survival of attached mussels by simulating a mussel farming model in a laboratory setting. Byssus production and mechanical properties of thread in response to varying salinity levels were assessed, and histological sections of the mussel foot were analyzed to identify the changes in the byssus secretory gland area. The results showed that hyposalinity stress (20 and 15 psu) led to a significant decrease in mussel byssus secretion, delayed initiation of new byssus production, and reduced plaque adhesion strength and breaking force of byssal threads compared to the control (30 psu) (p < 0.05). The complete suppression of byssal thread secretion in mussels under salinity conditions of 10 and 5 psu, leading to lethality, indicates the presence of a blockade in byssus secretion when mussels are subjected to significant physiological stressors. Histological analysis further demonstrated a decrease in the percentage of foot secretory gland areas in mussels exposed to low salinities. However, contrary to expectations, the study found that mussels did not exhibit marked detachment from ropes in response to the reduced salinity levels during one week of exposure. Hyposalinity stress exposure reduced the byssal secretion capacity and the mechanical properties of threads, which could be a cause for the detachment of suspension-cultured mussels. These results highlight the vulnerability of mussels to hyposalinity stress, which significantly affects their byssus mechanical performance.

Visual Quantitation of Dopamine-Inspired Fluorescent Adhesion with Orthogonal Phenanthrenequinone Photochemistry

Quantifying adhesion is crucial for understanding adhesion mechanisms and developing advanced dopamine-inspired materials and devices. However, achieving nondestructive and real-time quantitation of adhesion using optical spectra remains challenging. Here, we present a dopamine-inspired orthogonal phenanthrenequinone photochemistry strategy for the one-step adhesion and real-time visual quantitation of fluorescent spectra. This strategy utilizes phenanthrenequinone-mediated photochemistry to facilitate conjoined network formation in the adhesive through simultaneous photoclick cycloaddition and free-radical polymerization. The resulting hydrogel-like adhesive exhibits good mechanical performance, with a Young's modulus of 300 kPa, a toughness of 750 kJ m-3, and a fracture energy of 4500 J m-2. This adhesive, along with polycyclic aromatic phenanthrenequinones, shows strong adhesion (>100 kPa) and interfacial toughness thresholds (250 J m-2) on diverse surfaces─twice to triple as much as typical dopamine-contained adhesives. Importantly, such an adhesive demonstrates excellent fluorescent performance under UV irradiation, closely correlating with its adhesion strengths. Their fluorescence intensities remain constant after continuous stretching/releasing treatment and even in the dried state. Therefore, this dopamine-inspired orthogonal phenanthrenequinone photochemistry is readily available for real-time and nondestructive visual quantitation of adhesion performance under various conditions. Moreover, the adhesive precursor is chemically ultrastable for more than seven months and achieves adhesion on substrates within seconds upon blue light irradiation. As a proof-of-concept, we leverage the rapid and visual quantitation of adhesion and printability to create fluorescent patterns and structures, showcasing applications in information storage, adhesion prediction, and self-reporting properties. This general and straightforward strategy holds promise for rapidly preparing functional adhesive materials and designing high-performance wearable devices.

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.

Natural polyphenolic antibacterial bio-adhesives for infected wound healing

Bio-adhesives used clinically, commonly have the ability to fill surgical voids and support wound healing, but which are devoid of antibacterial activity, and thus, could not meet the particular needs of the infected wound site. Herein, a series of natural polyphenolic antibacterial bio-adhesives were prepared via simple mixing and heating of polyphenols and acid anhydrides without any solvent or catalyst. Upon the acid anhydride ring opening and acylation reactions, various natural polyphenolic bio-adhesives could adhere to various substrates (i.e., tissue, wood, glass, rubber, paper, plastic, and metal) based on multi-interactions. Moreover, these bio-adhesives showed excellent antibacterial and anti-infection activity, rapid hemostatic performance and appropriate biodegradability, which could be widely used in promoting bacterial infection wound healing and hot burn infection wound repair. This work could provide a new strategy for strong adhesives using naturally occurring molecules, and provide a method for the preparation of novel multifunctional wound dressings for infected wound healing.

A dynamic biointerface controls mussel adhesion

The mussel-adherent secreta interface reveals how nonliving material can be compatible with tissue.