3D-engineered nano-architectures with various functionalities are still difficult to obtain and translate for real-world applications. However, such nanomaterials are naturally abundant and yet wasted, but could trigger huge interest for blue bioeconomy, provided that our understanding of their ultrastructure-function is achieved. To date, the Bouligand pattern in crustaceans shell structure is believed to be unique. Here we demonstrated that in blue crab Callinectes sapidus, the 3D-nanoarchitecture is color-specific, while the blue and red-orange pigments interplay in different nano-sized channels and pores. Thinnest pores of about 20 nm are found in blue shell. Additionally, the blue pigment co-existence in specific Bouligand structure is proved for the green crab Carcinus aestuarii, although the crab does not appear blue. The pigments interplay, simultaneously detected by Raman spectroscopy in color-specific native cuticles, overturns our understanding in crustaceans coloration and may trigger the selective use of particular colored natural nanoarchitectures for broaden area of applications.

The current study presents the effect of naked Fe₃O₄@Carbon nanoparticles obtained by the combustion method on primary human gingival fibroblasts (HGFs) and primary gingival keratinocytes (PGKs)—relevant cell lines of buccal oral mucosa. In this regard, the objectives of this study were as follows: (i) development via combustion method and characterization of nanosized magnetite particles with carbon on their surface, (ii) biocompatibility assessment of the obtained magnetic nanoparticles on HGF and PGK cell lines and (iii) evaluation of possible irritative reaction of Fe₃O₄@Carbon nanoparticles on the highly vascularized chorioallantoic membrane of a chick embryo. Physicochemical properties of Fe₃O₄@Carbon nanoparticles were characterized in terms of phase composition, chemical structure, and polymorphic and molecular interactions of the chemical bonds within the nanomaterial, magnetic measurements, ultrastructure, morphology, and elemental composition. The X-ray diffraction analysis revealed the formation of magnetite as phase pure without any other secondary phases, and Raman spectroscopy exhibit that the pre-formed magnetic nanoparticles were covered with carbon film, resulting from the synthesis method employed. Scanning electron microscopy shown that nanoparticles obtained were uniformly distributed, with a nearly spherical shape with sizes at the nanometric level; iron, oxygen, and carbon were the only elements detected. While biological screening of Fe₃O₄@Carbon nanoparticles revealed no significant cytotoxic potential on the HGF and PGK cell lines, a slight sign of irritation was observed on a limited area on the chorioallantoic membrane of the chick embryo.

The compliance of crab shells traditionally used as a complex natural product for agricultural soil amendment with modern biofertilizers’ quality and safety requirements was investigated. Shells waste from the Blue crab, Callinectes sapidus and the Green crab, Carcinus aestuarii were tested for macronutrients, heavy metals, bacteria content, and antimicrobial properties. Such information is crucial for further utilization of the biogenic powders for any composite formulation in added-value by-products. The calcium carbonate-rich hard tissue yield was 52.13% ± 0.015 (mean ± S.D.) and 64.71% ± 0.144 from the blue and green crabs, respectively. The contents of Pb, Ni, Zn, Cr (VI), and Cu were several orders of magnitude below the prescribed limit by EU biofertilizer legislation, with Fe, Mn (not prescribed), and As being the most abundant. The content of As and Cd from the material considered here was within limits. The shells contain no colony-forming units of Salmonella spp. and compliant levels of Escherichia coli; moreover, the shell micro-powder showed dose-dependent growth inhibition of Pseudomonas aeruginosa and Staphylococcus aureus. In summary, the waste crab shells present a complex natural product as plant biofertilizer following the circular economy concepts.