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Although biomimetic designs are expected to play a key role in exploring future structural materials, facile fabrication of bulk biomimetic materials under ambient conditions remains a major challenge. Here, we describe a mesoscale \"assembly-and-mineralization\" approach inspired by the natural process in mollusks to fabricate bulk synthetic nacre that highly resembles both the chemical composition and the hierarchical structure of natural nacre. The millimeter-thick synthetic nacre consists of alternating organic layers and aragonite platelet layers (91 weight percent) and exhibits good ultimate strength and fracture toughness. This predesigned matrix-directed mineralization method represents a rational strategy for the preparation of robust composite materials with hierarchically ordered structures, where various constituents are adaptable, including brittle and heat-labile materials.

Marine organisms represent a highly diverse reserve of bioactives which could aid in the treatment of a wide range of diseases, including various musculoskeletal conditions. Osteoporosis in particular would benefit from a novel and effective marine-based treatment, due to its large disease burden and the inefficiencies of current treatment options. Osteogenic bioactives have been isolated from many marine organisms, including nacre powder derived from molluscan shells and fucoidan—the sulphated polysaccharide commonly sourced from brown macroalgae. Such extracts and compounds are known to have a range of osteogenic effects, including stimulation of osteoblast activity and mineralisation, as well as suppression of osteoclast resorption. This review describes currently known soluble osteogenic extracts and compounds from marine invertebrates and algae, and assesses their preclinical potential.

Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness 1 – 3 . Such properties are attributed to the elaborate layered microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix 4 – 6 . Inspired by these biological structures, several assembly strategies—including layer-by-layer 4 , 7 , 8 , casting 9 , 10 , vacuum filtration 11 – 13 and use of magnetic fields 14 , 15 —have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 ± 80 megapascals and a Young’s modulus of 198.8 ± 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 ± 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre; meanwhile, the tensile strength is 1,195 ± 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites. Layered nanocomposites fabricated using a continuous and scalable process achieve properties exceeding those of natural nacre, the result of stiffened matrix polymer chains confined between highly aligned nanosheets.

The development of flexible thermistor epidermal electronics (FTEE) to satisfy high temperature resolution without strain induced signal distortion is of great significance but still challenging. Inspired by the nacre microstructure capable of restraining the stress concentration, we exemplify a versatile MXene-based thermistor elastomer sensor (TES) platform that significantly alleviates the strain interference by the biomimetic laminated strategy combining with the in-plane stress dissipation and nacre-mimetic hierarchical architecture, delivering competitive advantages of superior thermosensitivity (−1.32% °C −1 ), outstanding temperature resolution (~0.3 °C), and unparalleled mechanical durability (20000 folding fatigue cycles), together with considerable improvement in strain-tolerant thermosensation over commercial thermocouple in exercise scenario. By a combination of theoretical model simulation, microstructure observation, and superposed signal detection, the authors further reveal the underlying temperature and strain signal decoupling mechanism that substantiate the generality and customizability of the nacre-mimetic strategy, possessing insightful significance of fabricating FTEE for static and dynamic temperature detection. Flexible thermistor epidermal electronics is desired to continuously monitor skin temperature in medical applications. Hao et al. report a nacre mimetic laminated strategy to fabricate thermistors with large mechanical durability for high-fidelity temperature discrimination without signal distortion.

Nacre is generally regarded as tough body armor, but it was often smashed by predators with a certain striking speed. Nacre-like architectures have been demonstrated to dissipate abundant energy by tablets sliding at static or specific low-speed loads, but whether they’re still impact-resistant templates in a wide range of impact velocities remains unclear. Here, we find an anomalous phenomenon that nacre-like structures show superior energy-dissipation ability only in a narrow range of low impact velocities, while they exhibit lower impact resistance than laminated structures when impact velocity exceeds a critical value. This is because the tablets sliding in nacre-like structure occurs earlier and wider at low impact velocities, while it becomes localized at excessive impact velocities. Such anomalous phenomenon remains under different structural sizes and boundary conditions. It further inspires us to propose a hybrid architecture design strategy that achieves optimal impact resistance in a wide range of impact velocities. Nacre structure is used as inspiration in the design of impact resistant materials yet natural nacre is overcome by high impact speed attacks from predators. Here, the authors perform a range of testing and demonstrate superior energy dissipation of nacre-like structures at low impact velocities which is lost at higher impact velocities.

The nacre color of shells has an effect on the pearl color in Hyriopsis cumingii and is an important indicator for its value. The nacre is part of the shell, and some studies have shown that exosomes of the mantle are involved in the formation of shells. Most of the RNA contained in exosomes are microRNAs (miRNAs); however, little information is available on the roles of exosomes and miRNAs on the formation of nacre color in mussels. In this study, exosomes of mantles were extracted from white and purple mussels. High-throughput Illumina sequencing was performed on the white and purple mussel mantle exosomes, and 7,665,167 and 10,994,115 reads were harvested. Using the standard of |log2(Fold change)| ≥ 2, and a p value ≤ 0.05, a total of 54 differentially expressed miRNAs were identified. The miRNAs that regulated the target genes (hcApo, HcTyr, HcTyp-1, HcMitf, HcSRCR1, and HcSRCR2) involved in shell color formation were predicted. Moreover, miR-15b negatively regulated hcApo, which plays important roles in the absorption and transport of β-carotene in H. cumingii. These results improve our understanding of the molecular mechanisms of nacre color formation in H. cumingii.

Biological materials such as nacre have evolved microstructural design principles that result in outstanding mechanical properties. While nacre’s design concepts have led to bio-inspired materials with enhanced fracture toughness, the microstructural features underlying the remarkable damping properties of this biological material have not yet been fully explored in synthetic composites. Here, we study the damping behavior of nacre-like composites containing mineral bridges and platelet asperities as nanoscale structural features within its brick-and-mortar architecture. Dynamic mechanical analysis was performed to experimentally elucidate the role of these features on the damping response of the nacre-like composites. By enhancing stress transfer between platelets and at the brick/mortar interface, mineral bridges and nano-asperities were found to improve the damping performance of the composite to levels that surpass many biological and man-made materials. Surprisingly, the improved properties are achieved without reaching the perfect organization of the biological counterparts. Our nacre-like composites display a loss modulus 2.4-fold higher than natural nacre and 1.4-fold more than highly dissipative natural fiber composites. These findings shed light on the role of nanoscale structural features on the dynamic mechanical properties of nacre and offer design concepts for the manufacturing of bio-inspired composites for high-performance damping applications.

Thermally conductive polymer nanocomposites integrated with lightweight, excellent flexural strength, and high fracture toughness ( K Ic ) would be of great use in many fields. However, achieving all of these properties simultaneously remains a great challenge. Inspired by natural nacre, here we demonstrate a lightweight, strong, tough, and thermally conductive boron nitride nanosheet/epoxy layered (BNNEL) nanocomposite. Because of the layered structure and enhancing the interfacial interactions through hydrogen bonding and Si–O–B covalent bonding, the resulting nacre-inspired BNNEL nanocomposites show high fracture toughness of ∼ 4.22 MPa·m 1/2 , which is 7 folds as high as pure epoxy. Moreover, the BNNEL nanocomposites demonstrate sufficient flexural strength (∼ 168.90 MPa, comparable to epoxy resin), while also being lightweight (∼ 1.23 g/cm 3 ). Additionally, the BNNEL nanocomposites display a thermal conductivity ( κ ) of ∼ 0.47 W/(m·K) at low boron nitride nanosheet loading of 2.08 vol.%, which is 2.7 times higher than that of pure epoxy resin. The developed nacre-inspired strategy of layered structure design and interfacial enhancement provides an avenue for fabricating high mechanical properties and thermally conductive polymer nanocomposites.

In the classic molecular model of nacreous layer formation, unusual acidic matrix proteins rich in aspartic acid (Asp) residues are essential for nacre nucleation due to their great affinity for binding calcium. However, the acidic matrix proteins discovered in the nacreous layer so far have been weakly acidic with a high proportion of glutamate. In the present study, several silk-like matrix proteins, including the novel matrix protein HcN57, were identified in the ethylenediaminetetraacetic acid-soluble extracts of the nacreous layer of Hyriopsis cumingii. HcN57 is a highly repetitive protein that consists of a high proportion of alanine (Ala, 34.4%), glycine (Gly, 22.5%), and serine (Ser, 11.4%). It forms poly Ala blocks, GlynX repeats, an Ala-Gly repeat, and a Ser-Ala-rich region, exhibiting significant similarity to silk proteins found in spider species. The expression of HcN57 was specifically located in the dorsal epithelial cells of the mantle pallium and mantle center. Notably, expression of HcN57 was relatively high during nacreous layer regeneration and pearl nacre deposition, suggesting HcN57 is a silk matrix protein in the nacreous layer. Importantly, HcN57 also contains a certain content of Asp residues, making it an unusual acidic matrix protein present in the nacreous layer. These Asp residues are mainly distributed in three large hydrophilic acidic regions, which showed inhibitory activity against aragonite deposition and morphological regulation of calcite in vitro. Moreover, HcN57-dsRNA injection resulted in failure of nacre nucleation in vivo. Taken together, our results show that HcN57 is a bifunctional silk protein with poly Ala blocks and Gly-rich regions that serve as space fillers within the chitinous framework to prevent crystallization at unnecessary nucleation sites and Asp-rich regions that create a calcium ion supersaturated microenvironment for nucleation in the center of nacre tablets. These observations contribute to a better understanding of the mechanism by which silk proteins regulate framework construction and nacre nucleation during nacreous layer formation.

Constructing flexible and robust thermally conductive but electrically insulating composite films for efficient and safe thermal management has always been a sought-after research topic. Herein, a nacre-inspired high-performance poly(p-phenylene-2,6-benzobisoxazole) (PBO)/MXene nanocomposite film was prepared by a sol-gel-film conversion method with a homogeneous gelation process. Because of the as-formed optimized brick and mortar structure, and the strong bridging and caging effects of the fine PBO nanofibre network on the MXene nanosheets, the resulting nanocomposite film is electrically insulating (2.5 × 10 9  Ω cm), and exhibits excellent mechanical properties (tensile strength of 416.7 MPa, Young’s modulus of 9.1 GPa and toughness of 97.3 MJ m −3 ). More importantly, the synergistic orientation of PBO nanofibres and MXene nanosheets endows the film with an in-plane thermal conductivity of 42.2 W m −1 K −1 . The film also exhibits excellent thermal stability and flame retardancy. This work broadens the ideas for preparing high-performance thermally conductive but electrically insulating composites. Constructing thermally conductive but electrically insulating composites remains a challenge. Here, Ti 3 C 2 MXene is combined in a nacre-like structure with the polymer PBO to form such materials, also exhibiting high thermal stability and flame retardancy.