Hypoxia weakens mussel attachment by interrupting DOPA cross-linking during adhesive plaque curing

Characterization of a novel antioxidant byssal protein from Mytilus coruscus foot

Mussel byssal proteins are of biomimetic importance for the development of novel underwater bio-adhesive agents. It is important to maintain a reduced state during the process of byssus adhesion. There are 19 mussel foot proteins (MFPs) have been reported in previous studies, among which only MFP-6 had been confirmed as an antioxidant protein in mussel byssus due to the function of cysteines, and playing an essential role in the redox balance of mussel byssus during adhesion process. Although the other four MFPs (MFP-16 ~ MFP-19) also have abundant cysteines, their function is still unknown. In this study, a novel mussel foot protein, named MFP-20, was identified from Mytilus coruscus foot. The sequential features, expression profile, and function of recombinant MFP-20 were verified. The results showed that MFP-20 has more abundant cysteines than other MFPs, the relative expression of mfp-20 was upregulated in Fe3+ stress and low pH seawater. In addition, different adhesive substrates induced significant changes of expression level of mfp-20. Furthermore, rMFP-20 showed strong antioxidant capacity in the DPPH assay, and the abundant cysteines in its sequence may play vital roles in the antioxidation activity. Our findings revealed the possible function of MFP-20 with a totally different sequence from the reported MFP-6 and provided new clues for exploring the redox balance of mussel byssus during the adhesion process.

Efficient genome editing by controlled release of Cas9 ribonucleoprotein in plant cytosol using polymer-modified microneedle array

Direct delivery of genome-editing proteins into plant tissues could be useful in obtaining DNA-free genome-edited crops obviating the need for backcrossing to remove vector-derived DNA from the host genome as in the case of genetically modified organisms generated using DNA vector. Previously, we successfully delivered Cas9 ribonucleoprotein (RNP) into plant tissue by inserting microneedle array (MNA) physisorbed with Cas9 RNPs. Here, to enhance protein delivery and improve genome-editing efficiency, we introduced a bioactive polymer DMA/HPA/NHS modification to the MNA, which allowed strong bonding between the proteins and MNA. Compared with other modifying agents, this MNA modification resulted in better release of immobilized protein in a plant cytosol-mimicking environment. The delivery of Cas9 RNPs in Arabidopsis thaliana reporter plants was improved from 4 out of 17 leaf tissues when using unmodified MNAs to 9 out of 17 when using the polymer-modified MNAs. Further improvements in delivery efficiency can be envisaged by optimizing the polymer modification conditions, which could have significant implications for the development of more effective plant genome editing techniques.

Antioxidant N-acetylcysteine removing ROS: an antifouling strategy inspired by mussels

Marine biofouling is a thorny issue that causes serious economic losses and adverse ecological impacts on marine ecosystems. Effective and promising antifouling strategies such as surface hydration, flow shear force, and lubricant injection have been developed to address this challenge. However, for the complex marine environment, they still appear inadequate. Mussels are a common fouling organism with strong surface adhesion ability. However, when hypoxia and the oxidative cross-linking reaction of 3,4-dihydroxy phenyl-L-alanine (DOPA) in the structure of adhesion proteins are disrupted, their adhesion ability will be greatly reduced. Inspired by this, we developed an effective antifouling strategy based on reactive oxygen species (ROS) scavenging using N-acetylcysteine (NAC) and evaluated its performance. As a ROS scavenger interfered with the oxidative cross-linking reaction of DOPA in an aqueous solution, the adhesion of DOPA was also affected on the surface of NAC functionalized polyvinyl chloride (PVC) (PVC-NAC). In addition, the colonization level of mussels and the adhesion rate of marine bacteria and benthic diatoms on PVC-NAC were low. The antifouling strategy proposed in this paper was eco-friendly and broad-spectrum, and may provide a new idea for solving marine biofouling and reducing the environmental and economic impacts of fouling organisms.

Mussel‐Inspired Biomaterials: From Chemistry to Clinic

After several billions of years, nature still makes decisions on its own to identify, develop, and direct the most effective material for phenomena/challenges faced. Likewise, and inspired by the nature, we learned how to take steps in developing new technologies and materials innovations. Wet and strong adhesion by Mytilidae mussels (among which Mytilus edulis—blue mussel and Mytilus californianus—California mussel are the most well‐known species) has been an inspiration in developing advanced adhesives for the moist condition. The wet adhesion phenomenon is significant in designing tissue adhesives and surgical sealants. However, a deep understanding of engaged chemical moieties, microenvironmental conditions of secreted proteins, and other contributing mechanisms for outstanding wet adhesion mussels are essential for the optimal design of wet glues. In this review, all aspects of wet adhesion of Mytilidae mussels, as well as different strategies needed for designing and fabricating wet adhesives are discussed from a chemistry point of view. Developed muscle‐inspired chemistry is a versatile technique when designing not only wet adhesive, but also, in several more applications, especially in the bioengineering area. The applications of muscle‐inspired biomaterials in various medical applications are summarized for future developments in the field.

Divergent Effects of Ocean Warming On Byssal Attachment in Two Congener Mussel Species

Organisms rely on the integrity of the structural materials they produce to maintain a broad range of processes, such as acquiring food, resisting predators or withstanding extreme environmental forces. The production and maintenance of these biomaterials, which are often modulated by environmental conditions, can therefore have important consequences for fitness in changing climates. One well-known example of such a biomaterial is mussel byssus, an array of collagen-like fibers (byssal threads) that tethers a bivalve mollusk securely to benthic marine substrates. Byssus strength directly influences mortality from dislodgement, predation or competition and depends on the quantity and quality of byssal threads produced. We compared the temperature sensitivity of byssal attachment strength of two mussel species common to the west coast of North America, Mytilus trossulus and M. galloprovincialis, when exposed to seawater temperatures ranging from 10 to 24˚C in the laboratory. We found the two species attached equally strong in seawater ≤ 18˚C, but higher temperatures caused byssal thread production rate and quality (break force and extensibility) to be greatly reduced in M. trossulus and increased in M. galloprovincialis, leading to a 2 to 10-fold difference in overall byssus strength between the two species. Using this threshold value (18˚C), we mapped habitat for each species along the west coast of North America based on annual patterns in sea surface temperature. Estimated ranges are consistent with the current distribution of the two species and suggest a potential mechanism by which ocean warming could facilitate the northern expansion of M. galloprovincialis and displacement of native M. trossulus populations.

Injectable pH-responsive adhesive hydrogels for bone tissue engineering inspired by the underwater attachment strategy of marine mussels

A major challenge in tissue engineering is the development of alternatives to traditional bone autografts and allografts that can regenerate critical-sized bone defects. Here we present the design of injectable pH-responsive double-crosslinked adhesive hydrogels inspired by the molecular mechanism and environmental post-processing of marine mussel adhesive. Nine adhesive hydrogel formulations were developed through the conjugation of crosslinkable catechol functional groups (DOPA) and the synthetic oligomer oligo[poly(ethylene glycol) fumarate] (OPF), varying the DOPA content (w/w%) and molecular weight (MW) of the OPF backbone to produce formulations with a range of swelling ratios, porosities, and crosslink densities. DOPA incorporation altered the surface chemistry, mechanical properties, and surface topography of hydrogels, resulting in an increase in material stiffness, slower degradation, and enhanced pre-osteoblast cell attachment and proliferation. When injected within simulated bone defects, DOPA-mediated interfacial adhesive interactions also prevented the displacement of scaffolds, an effect that was maintained even after swelling within physiological conditions. Taken together, OPF-DOPA hydrogels represent a promising new material to enhanced tissue integration and the prevention of the post-implantation migration of scaffolds that can occur due to biomechanical loading in vivo.

Counterplotting the Mechanosensing-Based Fouling Mechanism of Mussels against Fouling

Marine organisms react to various factors when building colonies for survival; however, severe accumulation of diverse organisms on artificial structures located close to water causes large industrial losses. Herein, we identify a concept in the development of antifouling surfaces based on understanding the surface stiffness recognition procedure of mussel adhesion at the genetic level. It was found that on a soft surface the combination of decreased adhesive plaque size, adhesion force, and plaque protein downregulation synergistically weakens mussel wet adhesion and sometimes prevents mussels from anchoring, mainly due to transcriptional changes within the mechanosensing pathway and the adhesive proteins in secretory glands. In addition, the use of soft substrates or antagonists of surface mechanosensing behavior suppresses mussel fouling significantly.

The entangled multi-level responses of Mytilus galloprovincialis (Lamarck, 1819) to environmental stressors as detected by an integrated approach

Anthropogenic pressure adds up and interacts with the effects of climate change with a varying magnitude and potential changes depend on species' Life History (LH) traits, local environmental conditions and co-occurrence of several stressors. Stressors exert negative effects on marine biota when acting as a single factor, but the effects may be amplified when more than one stressor work in combination, producing interacting effects on biodiversity and ecosystem functioning. The impairment of individual functional traits (FT) leads to strong rebounds on LH traits and this may have ecological consequences. No studies actually relate FT and antioxidant enzymes to multiple environmental stressors. In this paper we investigate the effects of food concentration, temperature and hypoxia on metabolic traits as expressed by a proxy such as respiration rate and feeding behaviour and on antioxidant enzymes (Catalase, Superoxide dismutase, Glutathione S-Transferase, Glutathione peroxidase) for the bivalve Mytilus galloprovincialis. Mussels were exposed to three temperatures (12, 20 and 28 °C) under normoxic (8 mg O₂ l^-1) and hypoxic (~2 mg O₂ l^-1) conditions, with varying food concentrations ranging from 0.9 to 3.5 μg of chlorophyll l^-1. The results show that FTs and antioxidant enzymes were affected by temperature, hypoxia and food availability, and outcome allowed us to emphasise that a multi-scalar integrated approach is suitable to detect and monitor effects of anthropogenic disturbance on ecosystem functioning.