Availability of Environmental Iron Influences the Performance of Biological Adhesives Produced by Blue Mussels

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.

Coacervate Phase Evolution and Membrane Formation in Natural Seawater

Marine organisms produce biological materials through the complex self-assembly of protein condensates in seawater, but our understanding of the mechanisms of microstructure evolution and maturation remains incomplete. Here, we show that critical processing attributes of mussel holdfast proteins can be captured by the design of an amphiphilic, fluorescent polymer (PECHIA) consisting of a polyepichlorohydrin backbone grafted with 1-imidazolium acetonitrile. Aqueous solutions of PECHIA were extruded into seawater, wherein the charge repulsion of PECHIA is screened by high salinity, facilitating interfacial condensation via enhanced "cation-dipole" interactions. Diffusion of seawater into the PECHIA solution caused droplets to form immiscibly within the PECHIA phase (i.e., inverse coacervation). Simultaneously, weakly alkaline seawater catalyzes nitrile cyclization and time-dependent solidification of the PECHIA phase, leading to hierarchically porous membranes analogous to porous architectures in mussel plaques. In contrast to conventional polymer processing technologies, processing of this biomimetic polymer required neither organic solvents nor heating and enabled the template-free production of hollow spheres and fibers over a wide range of salinities.

Poly lactic acid production using the ring opening polymerization (ROP) method using Lewis acid surfactant combined iron (Fe) catalyst (Fe(DS)3)

LASC catalyst synthesis process was carried out using iron metal (Fe) and its characterization properties were tested. There are five stages carried out, namely, the manufacture of the LASC Fe(DS)3 catalyst, lactic acid dehydration, polycondensation of lactic acid into l-lactic acid oligomers (OLLA), depolymerization of oligomers into l-lactide, and the ROP process to convert l-lactide into Polymers. l-lactic acid (PLLA). The analysis used is as follows, Karl-Fisher; Spectroscopy Fourier Transform Infrared (FTIR); and Nuclear Magnetic Resonance (HNMR); Gel Permeation Chromatography (GPC); Thermogravimetry Gravity Analysis (TGA) and X-Ray Diffraction (XRD). Based on the experimental results, the catalyst Fe(DS)₃ has a crystallinity value of 24% which indicates an amorphous nature and is easy to react. The value of the thermal stability of the catalyst is at 180 °C where the catalyst is able to process up to a temperature of 180 ^°C. Each step of the ROP is validated by FTIR analysis which shows that the components of the group are in accordance with the expected product. The comparison of the crystallinity values of PLA produced with FeCl₃ and Fe(DS)₃ were 37.5 and 49%, respectively. Melting temperature (Tm) values are 111 and 107 ^°C, respectively, Td values are 327 and 352 °C, and the resulting molecular weights are 23,720 and 20,232 g/mol. Based on the results obtained, it can be seen that the use of a LASC catalyst in the form of Fe(DS)₃ is more effective than without using a LASC catalyst.

Rare metal, precious adhesion

[Figure: see text].

Effectiveness and Mechanisms of Recoverable Magnetic Nanoparticles on Mitigating Golden Mussel Biofouling

Mussel biofouling has become a problem in aquatic ecosystems, causing significant ecological impact and huge economic loss globally. Although several strategies have been proposed and tested, efficient and environment-friendly antifouling methods are still scarce. Here, we investigated the effects of recoverable magnetic ferroferric oxide nanoparticles (Fe₃O₄-NPs) with different sizes (10 and 100 nm), coatings (polyethylene glycol and polylysine), and concentrations (0.01 and 0.1 mg/L) on byssus adhesion-mediated biofouling by the notorious golden mussel Limnoperna fortunei. The results showed that magnetic Fe₃O₄-NPs, especially negatively charged polyethylene glycol-coated Fe₃O₄-NPs, size- and concentration-dependently reduced the byssus production, performance (breaking force and failure location), and adhesion rate. Further investigations on mechanisms showed that the down-regulation of foot protein 2 (Lffp-2) and energy-related metabolic pathways inhibited byssus production. The declined gene expression level and metal-binding ability of Lffp-2 significantly affected foot protein interactions, further reducing the plaque size and byssus performance. In addition, the change in the water redox state likely reduced byssus performance by preventing the interface interactions between the substrate and foot proteins. Our results confirm the effectiveness and underlying mechanisms of magnetic Fe₃O₄-NPs on mitigating L. fortunei biofouling, thus providing a reference for developing efficient and environment-friendly antifouling strategies against fouling mussels.