Otolith biomineralization results from biochemical processes regulated by the interaction of internal (physiological) and external (environmental) factors which leads to morphological and ultrastructural variability at intra- and inter-specific levels [1]. Here, for the first time, we: 1) describe the relationship between multi-scale otolith parameters and fish somatic growth (i.e., total fish length) in juveniles, females, and males of Merluccius merluccius (European hake) from the western Adriatic Sea; 2) characterize the sulcus acusticus and its subregions (ostial colliculum, caudal colliculum and collum) and measured the corresponding area and volume; 3) reveal a sexual dimorphism in the morphology of otolith during ontogenesis. We show that juvenile’s otoliths had faster growth in length, width, area, perimeter, volume, weight, a higher amount of organic matter and trace element concentration, a lower density (both micro-density and bulk-density), a higher porosity and a higher value of sulcus volume: otolith volume ratio (SV:OV) compared to adult’s otoliths. Furthermore, the sexual dimorphism in the morphology of otolith during ontogenesis has been revealed for the first time through a novel 3D shape analysis approach based on micro CT scans.

We found that, with increasing fish length, female saccular otoliths contained a higher amount of protuberances compared to male specimens which showed more uniform mean curvature density. The changes observed in the otolith features and sulcus acusticus regions during the growth could be linked to an eco-morphological adaptation to different biological, behavioral and environmental characteristics between juveniles and adults, which could have a functional meaning in terms of otolith response to sound waves (shape/structure–function relationships). In addition, the differences between females and males discovered in this study could be associated with fish hearing adaptation to reproductive behavioral strategies during the spawning season. Based on the outcomes of this first investigation, the use of innovative approaches is promising in highlighting differences in otoliths that could bring functional significance in specific ecological and behavioral contexts. Furthermore, the results obtained from this study can also provide inputs for further investigations aiming to understand otolith growth process according to fish size and gender and to explore the sources of otolith morphological variability during ontogenesis.

Future virtual experiments of vibroacoustic will be addressed in order to establish the shape/structure–function relationships in otoliths during fish ontogenesis and between sex and, consequently, investigate if there are any differences in the otolith response to sound waves which could enhance auditory abilities in a certain habitat or improve fish communication in specific contexts.

[1] Campana, S.E. (1992) Measurement and interpretation of the microstructure of fish otoliths. Canadian Special Publication of Fisheries and Aquatic Sciences, 117, 59-71.

Foraminifers are unicellular marine organisms which form a carbonate shell (‘test’) that is made of consecutively mineralised chambers. Due to the high abundance and good preservation of these tests in ocean sediments, foraminifers are a key component of the global carbon cycle and provide an outstanding archive for paleoclimate reconstruction. The exact mechanism of biomineralisation in foraminifers is not known, which results in uncertainties both in their reaction to climate change and ocean acidification, as well as for the interpretation of element and isotope proxies for past climate conditions measured on fossil tests.

To address this, we investigated the crystal structure and structural hierarchy of the tests of planktic and benthic hyaline foraminifer species from different suborders, including both modern and fossil specimens dating back to approx. 5 Ma. A multi-technique approach was taken, including Laser Ablation Inductively Coupled Plasma Mass Spectrometry, Electron Backscatter Diffraction (EBSD), Scanning Electron Microscopy (SEM), as well as Rietveld refinement and Pair Distribution Function (PDF) analysis based on laboratory X-ray diffraction measurements. The investigated tests show no resolvable crystallographic difference between modern and fossil specimens. Crystalline metastable phases were not observed in any of the specimens. In modern samples, a slight elevation of the amorphous diffraction background is present, which could be attributed either to amorphous carbonates or organic residues. The unit cell parameters of biogenic Mg-calcites of the foraminifer shells were determined by Rietveld refinement to be close to inorganic Mg-calcite of the respective Mg-content. Crystallite dimensions for the investigated hyaline foraminifer tests range between 40-150 nm, as determined by Rietveld refinement, and at least 30-40 nm by PDF analysis. The small dimension of coherently diffracting crystallite domains is supported by a nanogranular surface morphology of mechanically fractured chamber walls in SEM, which exhibits irregularly formed units 100-300 nm in size. EBSD analysis demonstrates the presence of uniformly scattering regions in the test of the planktic species G. ruber with a diameter of several micrometres and the crystallographic c-axis of the grains oriented perpendicular to the chamber surface, which is a feature observed in several other hyaline foraminifer species [1]. This indicates that the tests of the investigated species are built of micrometre-sized mesocrystals made of aligned nanometre-sized entities. We hypothesise that a coalescence of the nanocrystallites is prevented by the presence of an amorphous margin around the entities, possibly organic- and/or impurity-rich, which is supported by the observation of amorphous matter at grain boundaries in a different hyaline foraminifer species [2].

The presence of nanogranular mesocrystals in hyaline foraminifer test calcites together with the distinct orientation of mesocrystal grains indicates a biochemically controlled biomineralisation mechanism, which follows a non-classical crystallisation pathway [2,3]. This supports the notion that foraminiferal biomineralisation involves the formation of a metastable precursor phase such as amorphous CaCO₃, possibly in interaction with an organic matrix, which is followed by directed crystallisation. This could suggest an involvement of organic matter in hyaline foraminifera biomineralisation not only as a template for mineralisation [4], but also as a surface and matrix for nucleation.

Hence, as a next step to resolve test biomineralisation mechanisms in foraminifers and to improve our understanding of the relation of proxies and test structure to environmental parameters, the composition and function of the organic material present at the site of mineralisation needs to be better understood, and the influence of organic matter on the nucleation and crystallisation of carbonates should be further studied in experimental models.

[1] Read, E. (2019). PhD thesis, University of Cambridge, United Kingdom

[2] Jacob, D. E., Wirth, R., Agbaje, O. B. A., Branson, O. & Eggins, S. M. (2017). Nature Communications. 8, 1–8.

[3] Wolf, S. E., Böhm, C. F., Harris, J., Demmert, B., Jacob, D. E., Mondeshki, M., Ruiz-Agudo, E. & Rodríguez-Navarro, C. (2016). Journal of Structural Biology. 196, 244–259.

[4] Towe, K. & Cifelli, R. (1967). Journal of Paleontology. 41, 742–762.

Modified amino acids and short peptides, as biologically active molecules and constituents of proteins, can be a golden remedy for diverse diseases, including viral infections, cancers, or neurodegenerative disorders, due to their unique features. Their specificity has been grinded by evolution over a million years. Peptides act as signaling entities via all domains of life and interfere with protein-protein interactions, which are indispensable in bio-processes. Advances in bio-nano-technological sciences and bio-informatics lead to overcome their poor ADMET profile. As consequence, these the simplest biomolecules are a glimmer of hope for next-generation, effective and safe theranostics [1]. From the point of view of the drug discovery, the supramolecular hydrogen-bonding synthon concept [2] is a promising tool in the future design of idealized ligands, with effective binding, inside the protein pockets through matching synthonic functionalities (from corresponding libraries) to the model ligands [3]. Notably, the same synthons, structural units formed by synthetic operations requiring non-covalent interactions, are observed both in supramolecular systems of ligands and bio-complexes. The latter can be considered as a supermolecule, which has been underestimated so far. The supramolecular studies of biomolecules, which cannot be mimicked by any other chemical compounds, are of prime importance. The idea of design and development of innovative and smart therapeutic peptide-based agents by utilizing of supramolecular synthon approach in ligand-protein complexes will be discussed in detail.

References

[1] Apostolopoulos, V., Bojarska, J., Chai, T.-T., Elnagdy, S., Kaczmarek, K., Matsoukas, J., et al. (2021). A Global Review on Short Peptides: Frontiers and Perspectives. Molecules 26, 430–475.

[2] Bojarska, J., Kaczmarek, K., Zabrocki, J., and Wolf,W.M. (2018a). Supramolecular Chemistry of Modified Amino Acids and Short Peptides. In Advances in Organic Synthesis; A. Rahman, Ed.; Bentham Science Publishers Ltd.: Sharjah, UAE, Volume 11, pp. 43–107.

[3] Spackman, P. R., Yu, L. J., Morton, C. J., Parker, M. W., Bond, C. S., Spackman, M. A., et al. (2019). Bridging Crystal Engineering and Drug Discovery by Utilizing Intermolecular Interactions and Molecular Shapes in Crystals. Angew. Chem. 131, 16936–16940.

Ion-mineral surface interactions are ubiquitous. The behavior of these interactions are reflective of the environment where the minerals and ions exist. In this work, interactions of ions and how they modulate the mineralization of calcium oxalate shall be discussed. Combinations of bulk and interfacial techniques reveal an interesting interplay of changes in crystal or mineral surface feature due to unique mode(s) of action where surface termination may facilitate the effective growth behavior of the crystal. Insights from the studies may have implication in rational design and control of crystalline materials.

Synthesizing pharmaceuticals and biomaterials that have antimicrobial biofunctionality has gained an increasing interest. In this respective, silver nanoparticles (AgNPs) possess outstanding antimicrobial activity. Nevertheless, their uncontrolled release in biological media can induce cytotoxic effects. In order to improve their bio-functionality, a number of metal phosphates, based on titanium and zirconium as the metallic sources, belonging to two distinct morphologies: nanolayered and nanofibrous structures were used as reservoirs for AgNPs (Fig.1). Nanolayered α-phases of titanium- and zirconium (IV) phosphates were supplemented with AgNPs. The structural assessment confirmed the stability of the structures and their sizes that laid in the nanoscale at least in one dimension. The cytocompatibility assays confirmed the biocompatibility of the pristine phases and the antimicrobial assays confirmed that both silver-enriched nanolayered structures maintain an antibacterial effect at reasonably low concentrations. The silver release in these layered structures is largely controlled owing to their intercalation [1]. On the other hand, the nanofibrous metal phosphates were utilized through synthesizing two phases of nanostructured titanium phosphate (π and ρ polymorphs). To assess the feasibility of using these nanofibrous π and ρ titanium (IV) phosphate phases for antimicrobial applications, they were enriched with AgNPs. The antimicrobial assays confirmed their functionality as antimicrobial materials. Moreover, the silver release could be controlled through enriching these nanofibrous Ag-enriched structures with strontium that increased their cytocompatibility, as was confirmed using the cytocompatibility and ion-release assessments. As a direct application of these phases for biomaterials applications, Ag-Sr-enriched nanostructured π-titanium phosphate was induced to grow on a commercially available titanium alloy (Ti-6Al-4V), widely used in orthopedic and dental implants. The structural and microscopic observations confirmed the resultant phases and their enrichment with strontium and AgNPs. Analysis of the surface roughness revealed that its values lays at the interface between the nanosized and micro sized topologies [2]. The results altogether demonstrate the feasibility of using the studied (Sr-) Ag-enriched layered and fibrous metal phosphates as bio-functional bone cement/filling or coatings for metallic implants for biomedical applications.

1. García, I., Trobajo, C., Amghouz, Z., Alonso-Guervos, M., Díaz, R., Mendoza, R., Mauvezín-Quevedo, M. & Adawy, A. (2021). Mater. Sci. Eng. C, 126, 112168.
2. García, I., Trobajo, C., Amghouz, Z. & Adawy, A. (2021). Materials, 14, 1481.

This research was funded by MINECO, grant number MAT2016-78155-C2-1-R and by the Government of the Principality of Asturias, grant number GRUPIN-IDI/2018/170. Special thanks go to professor S. García-Granda for the continuous support.

To meet future demands for cutting-edge wearable electronics, flexible supercapacitors must possess many features, such as eco-friendly processing, aesthetic appeal and no health hazards, in addition to have lightweight, robust and excellent cycling stability. We proposed a biomimetic and scalable method to fabricate an all-solid-state flexible supercapacitor (assFSC) using bioinspired clay/polymer nanocomposites and electroplated manganese oxide as electrode materials and a gel electrolyte. Experimental results from X-ray techniques (tomography, small-angel x-ray scattering and diffraction) showed that the electrode’s structure features a 3D ant-nest-like framework composed of 2D nacre-like clay nanosheets, i.e. hierarchical layers-within-networks structure, which is formed via water-evaporation induced self-organization. The shapeable electrodes made by a molding process could, therefore, be used to meet the demands for fashionable, wearable electronics. Accordingly, the structural electrodes exhibit high tensile strength of 62 MPa, Young’s modulus of 4.4 GPa, and torsional strength of 165 MPa. Under a large operating potential of 4.0 V, the assFSC exhibited ultrahigh energy density (233.3 W h kg^-1 at 2 kW kg^-1), ultrahigh power density (125 kW kg^-1 at 55.5 W h kg^-1), and outstanding static cyclability (less than 10% loss after 5,000 cycles). We also performed a cycle-life test under dynamic deformation and demonstrated that the assFSC had charging and discharging abilities during motion, according to particle applications of wearable electronics. Thus stable and superior electrochemical performance can be attributed to the biomimetic layers-within-networks structure, which not only provided robust framework but also induced 3D conducting networks with increasing ion channels and shortening charge transports.

Super Oxide Dismutase (SOD), which removes excess reactive oxygen species from the body, is also an important enzyme for not only the development of cancer drugs but also understanding the phenomena of disease development and progression. In the study of SOD model metal complexes such as zinc(II), copper(II), iron(II) or manganese(II), we focused on a Schiff base copper(II) complex of N- salicylidene-amino acid containing alpha-amino acid moiety1 to model structures as well as mimic functions of the native enzymes. However, few studies of hybrid proteins including SOD model complexes have been carried out so far to our knowledge.

In this study, we have synthesized a copper(II) complex incorporating L-threonine moiety2 and characterized by means of UV-vis, CD, and ESR spectra to compare SOD activity of the metal complex solely and the hybrid protein. The related copper(II) complexes potentially act as a photocatalyst for the reduction of metal ions3. After coordinating with lysozyme, the crystal structure of a hybrid lysozyme including the copper complex was determined at 0.92 Å to reveal coordination features and the related conformation of the protein. The imidazole nitrogen atom of His15 in lysozyme coordinated to the fourth coordination site of the four-coordinated copper(II) complex having the tridentate Schiff base ligand near the molecular surface of lysozyme (Fig. 1).