Preparation and characterization of FsHA/FsCol beads: Cell attachment and cytotoxicity studies

The present study was conducted to prepare the fish scales' hydroxyapatite/collagen beads (FsHA/FsCol) and characterize their biological, physical, and chemical properties. A new method was used to prepare FsHA/FsCol composite beads by infiltrating the beads of FsHA in the solution of FsCol as a green method. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) analysis, Fourier-transform infrared (FTIR) spectroscopy analysis and energy dispersive X-ray analysis (EDX), used to evaluate the physical-chemical properties of the synthesized samples. Meanwhile, the cytotoxic and attachment studies of the FsHA/FsCol beads were used to investigate the biological features against the MG-63 human cell line. The results specified the efficiency of the new method, functional groups of FsCol were indicated to be present inside the beads of FsHA according to the XRD analysis which shows the functional peaks of FsCol. The SEM image were conformed successfully use starch as a porous agent to increasing the porous of the FsHA beads after adding 20 wt% of it. Alamar Blue assay has been used to evaluate the cytotoxicity of FsHA/FsCol beads the results were shown 87% average cell viability of the MG-63 human cell line on the beads and attached very well to the surface of the composites, indicating no toxicity being exerted by all the composites at high concentrations.

Insight into the differences in carbon dots prepared from fish scales using conventional hydrothermal and microwave methods

The preparation of carbon dots (CDs) from waste fish scales is an attractive and high-value transformation. In this study, fish scales were used as a precursor to prepare CDs, and the effects of hydrothermal and microwave methods on their fluorescence properties and structures were evaluated. The microwave method was more conducive to the self-doping of nitrogen due to rapid and uniform heating. However, the low temperature associated with the microwave method resulted in insufficient dissolution of the organic matter in the fish scales, resulting in incomplete dehydration and condensation and the formation of nanosheet-like CDs, whose emission behavior had no significant correlation with excitation. Although the CDs prepared using the conventional hydrothermal method showed lower nitrogen doping, the relative pyrrolic nitrogen content was higher, which was beneficial in improving their quantum yield. Additionally, the controllable high temperature and sealed environment used in the conventional hydrothermal method promoted dehydration and condensation of the organic matter in the fish scales to form CDs with a higher degree of carbonization, uniform size, and higher C = O/COOH content. CDs prepared using the conventional hydrothermal method exhibited higher quantum yields and excitation wavelength-dependent emission behavior.

Using fish scales as a new biosorbent for adsorption of nickel and copper ions from wastewater and investigating the effects of electric and magnetic fields on the adsorption process

In this study, fish scales (Pomadasys kaakan's scales) were used as new biosorbent for removing Ni²⁺ and Cu²⁺ ions from wastewater. The effects of electric and magnetic fields on the absorption efficiency were also investigated. The effects of sorbent content, ion concentration, contact time, pH, electric field (EF), and magnetic field (MF) on absorption efficiency were assertained. In addition, the isotherm of absorption was studied in this work. This study revealed that electric field and magnetic field have significant effects on the absorption efficiency of ions from wastewater. An increase in the electric field enhanced the removal percentage of the ions and accelerated the absorption process by up to 40% in comparison with the same condition without an electric field or a magnetic field. By increasing contact time from 10 to 120 min, the removal of Ni²⁺ ions was increased from 1% to 40% and for Cu²⁺ ions, the removal increased from 20% to almost 95%, respectively. In addition, increasing pH, ion concentration and scales dose increased removal percentage effectively. The results indicated that using fish scales for Cu²⁺ ions absorption is ideal due to the very high removal percentage (approximately 95%) without using either an electric or magnetic field.

Eco-friendly preparation and characterization of bioplastic films made from marine fish-scale wastes

Synthetic plastics are becoming hazardous wastes, posing a threat to environmental sustainable health; hence, they must be replaced with alternatives. This study aimed to prepare corn starch-based bioplastics using fish scale through film casting technique as an alternative to synthetic plastics. In this work, four types of bioplastic films (CSF, CSFSF1, CSFSF2, FSF) containing different percentages of fish-scale powder and corn starch were prepared. Physical and chemical properties such as texture, color, solubility in hot water, tensile strength, functional groups, and morphology of all the four types of the prepared bioplastics were analyzed. The mixture of fish-scale powder and corn starch powder in the ratio of 1:3 (CSFSF1) yielded the best results. Its average thickness is 0.0420 ± 0.001 mm, water absorption range is 55-60%, tensile strength is 6.06 ± 0.05 MPa, and thermal stability is 278.741 °C. In the biodegradability test, degradation was noticed after 7 days of treatment with organic waste. The degradation was confirmed by surface changes in the morphology and the development of Aspergillus sp. Corn starch film (CSF) exhibited the highest degradation (60%), while the fish-scales film (FSF) underwent the least degradation (28%). The produced bioplastics were prepared from eco-friendly, inexpensive, and natural materials. Thus, the present research has provided a viable alternative to synthetic plastics.

Investigation of the combustion process of fish scales from Northeast Brazil in a drop tube furnace (DTF)

The waste generated by the global fishing industry, such as fish scales, is mostly considered useless and discarded in a disorderly and/or unplanned way in inappropriate places, posing serious risks to both the environment and human health. This study proposes the use of fish scales in combustion processes as an alternative for such residues and to avoid their exposure in urban areas. Combustion experiments were conducted in a drop tube furnace (DTF), and the factors temperature, residence time, and sample particle size were investigated. The main atmospheric pollutants (CO, NO, CO₂, and SO₂) and the residues generated from the combustion processes were characterized by FTIR, EDS and ICP-OES analyses, and SEM images. The samples showed better performance at 1100 °C and 500 -ms residence time, when the burnout reached 96%, and particle size greater than 300-μm and 300-ms residence time led to the worst combustion performance (24.45% burnout), with the highest CO and NO peaks, indicating incomplete combustion of the fish scales. The analysis of the residues revealed total decomposition of the organic matter at temperatures above 700 °C and formation of hydroxyapatite. According to the DTF results, the use of fish scales in firing processes is a viable treatment of the residues, generating energy and avoiding environmental problems caused by inadequate disposal.

Bioremediation potential of Dicentrarchus labrax fish scales for dye-based emerging contaminants by ANN-GA hybrid modeling

This work investigates the possibility of using scales of sea bass Dicentrarchus labrax as a low-cost material for the adsorptive removal of methylene blue (MB) cationic dye in aqueous solutions. The physical-chemical characterizations of fish scales in natura (FS-in natura) revealed through thermogravimetry that they are composed of inorganic (hydroxyapatite) and organic (collagen) phases in relatively similar amounts. Spectroscopy analyses show that the interactions of MB with FS-in natura occur mainly in the organic phase layer of the adsorbent. The effects of initial MB concentration (5.0 × 10^-4 and 5.0 × 10^-3 mol L^-1) and temperature (25-55 °C) on the adsorption efficiency of FS-in natura were evaluated. FS-in natura at MB concentration (5.0 × 10^-3 and 5.0 × 10^-4 mol L^-1) exhibited the maximum adsorption capacities of 2.2 × 10^-3 mol g^-1 at 25 °C and 2.8 × 10^-5 mol g^-1 at 55 °C, respectively. The pseudo-second-order model represented the adsorption kinetics well, and the equilibrium isotherm data were better correlated using the Langmuir equation. The newly developed neural model demonstrated a high predictive capacity with an R-value greater than 0.99 and reduced values for mean squared error, root mean squared error, and mean absolute error equal to 0.003, 0.055, and 0.0348, respectively. The genetic algorithm was used to optimize the experimental conditions of the process. In conclusion, the sea bass scales have promising prospects as a low-cost alternative material for removing cationic dyes from aqueous solutions.

Hydroxylated benzo[c]phenanthrene metabolites cause osteoblast apoptosis and skeletal abnormalities in fish

To study the toxicity of 3-hydroxybenzo[c]phenanthrene (3-OHBcP), a metabolite of benzo[c]phenanthrene (BcP), first we compared it with its parent compound, BcP, using an in ovo-nanoinjection method in Japanese medaka. Second, we examined the influence of 3-OHBcP on bone metabolism using goldfish. Third, the detailed mechanism of 3-OHBcP on bone metabolism was investigated using zebrafish and goldfish. The LC50s of BcP and 3-OHBcP in Japanese medaka were 5.7 nM and 0.003 nM, respectively, indicating that the metabolite was more than 1900 times as toxic as the parent compound. In addition, nanoinjected 3-OHBcP (0.001 nM) induced skeletal abnormalities. Therefore, fish scales with both osteoblasts and osteoclasts on the calcified bone matrix were examined to investigate the mechanisms of 3-OHBcP toxicity on bone metabolism. We found that scale regeneration in the BcP-injected goldfish was significantly inhibited as compared with that in control goldfish. Furthermore, 3-OHBcP was detected in the bile of BcP-injected goldfish, indicating that 3-OHBcP metabolized from BcP inhibited scale regeneration. Subsequently, the toxicity of BcP and 3-OHBcP to osteoblasts was examined using an in vitro assay with regenerating scales. The osteoblastic activity in the 3-OHBcP (10-10 to 10-7 M)-treated scales was significantly suppressed, while BcP (10-11 to 10-7 M)-treated scales did not affect osteoblastic activity. Osteoclastic activity was unchanged by either BcP or 3-OHBcP treatment at each concentration (10-11 to 10-7 M). The detailed toxicity of 3-OHBcP (10-9 M) in osteoblasts was then examined using gene expression analysis on a global scale with fish scales. Eight genes, including APAF1, CHEK2, and FOS, which are associated with apoptosis, were identified from the upregulated genes. This indicated that 3-OHBcP treatment induced apoptosis in fish scales. In situ detection of cell death by TUNEL methods was supported by gene expression analysis. This study is the first to demonstrate that 3-OHBcP, a metabolite of BcP, has greater toxicity than the parent compound, BcP.

Proteomics of sea bass skin-scales exposed to the emerging pollutant fluoxetine compared to estradiol

Teleost fish skin-scales are essential for protection and homeostasis and the largest tissue in direct contact with the environment, but their potential as early indicators of pollutant exposure are hampered by limited knowledge about this model. This study evaluated multi-level impacts of in vivo exposure of European sea bass to fluoxetine (FLX, a selective serotonin-reuptake inhibitor and an emerging pollutant) and 17β-estradiol (E2, a natural hormone and representative of diverse estrogenic endocrine-disrupting pollutants). Exposed fish had significantly increased circulating levels of FLX and its active metabolite nor-FLX that, in contrast to E2, did not have estrogenic effects on most fish plasma and scale indicators. Quantitative proteomics using SWATH-MS identified 985 proteins in the scale total proteome. 213 proteins were significantly modified 5 days after exposure to E2 or FLX and 31 were common to both treatments and responded in the same way. Common biological processes significantly affected by both treatments were protein turnover and cytoskeleton reorganization. E2 specifically up-regulated proteins related to protein production and degradation and down-regulated the cytoskeleton/extracellular matrix and innate immune proteins. FLX caused both up- and down-regulation of protein synthesis and energy metabolism. Multiple estrogen and serotonin receptor and transporter transcripts were altered in sea bass scales after E2 and/or FLX exposure, revealing complex disruptive effects in estrogen/serotonin responsiveness, which may account for the partially overlapping effects of E2 and FLX on the proteome. A large number (103) of FLX-specifically regulated proteins indicated numerous actions independent of estrogen signalling. This study provides the first quantitative proteome of the fish skin-scale barrier, elucidates routes of action and biochemical and molecular signatures of E2 or FLX-exposure and identifies potential physiological consequences and candidate biomarkers of pollutant exposure, for monitoring and risk assessment.

Glyoxal-induced formation of advanced glycation end-products in type 1 collagen decreases both its strength and flexibility in vitro

The high plasma glucose induced in glucose metabolism disorders leads to the non-enzymatic glucose-dependent modification (glycation) of type 1 collagen, which is an essential component of bone tissue. The glycation of proteins induces the formation of advanced glycation end-products, such as carboxymethyl arginine, which is preferentially generated in glycated collagen. However, the effect of advanced glycation end-product formation on the characteristics of type 1 collagen remains unclear due to the lack of suitable in vitro experimental systems analyzing type 1 collagen. Here, we show that the glycation of type 1 collagen can be analyzed in vitro using a goldfish-scale bone model. Our study using these scales provides evidence that the advanced glycation end-product formation in type 1 collagen induced by glyoxal, the carboxymethyl arginine inducer, facilitates the crosslinking of type 1 collagen, decreasing both its strength and flexibility.

Construction and characterization of degradable fish scales for enhancing cellular adhesion and potential using as tissue engineering scaffolds

As a framework for tissue engineering regeneration, the characteristics of cell scaffold materials directly affect cell adhesion, migration and metabolism. In this study, we have fabricated decellularized and decalcified fish scale-derived scaffolds and determined its basic physicochemical properties to serve as cell scaffolds in tissue engineering. Scanning electron microscopy (SEM) results showed that there were radial grooves and ring ridges on the surface of the scale-derived scaffolds, which could simulate three-dimensional microenvironment for cells culture. Similarity to the bone extracellular matrix, the main components of the fish scales were hydroxyapatite (HA) and type I collagen fibers, which were conducive to cells spreading and proliferation. Moreover, for culturing L929 cells and rat bone marrow mesenchymal stem cells (BMSCs), the fish scales as cell scaffolds exhibited high cytocompatibility to enhance cells adhesion and proliferation, and also displayed the ability to guide cells migration along the ridge channels. Accordingly, the results suggested that the fish scale-derived scaffolds had a great potential as a natural extracellular matrix for tissue engineering.

Structural and mechanical properties of fish scales for the bio-inspired design of flexible body armors: A review

Natural protection offered to living beings is the result of millions of years of biological revolution. The protections provided in fishes, armadillos, and turtles by unique hierarchal designs help them to survive in surrounding environments. Natural armors offer protections with outstanding mechanical properties, such as high penetration resistance and toughness to weight ratio. The mechanical properties are not the only key features that make scales unique; they are also highly flexible and breathable. In this study, we aim to review the structural and mechanical characteristics of the scales from ray-finned or teleost fishes, which can be used for new bio-inspired armor designs. It is also essential to consider the hierarchical structure of extinct and existing natural armors. The basic characteristics, as mentioned above, are the foundation for developing high-performance, well-structured flexible natural armors. Furthermore, the present review justifies the importance of interaction between toughness, hardness, and deformability in well-engineered bio-inspired body armor. At last, some suggestions are proposed for the design and fabrication of new bio-inspired flexible body armors.

Differentiating wild, lake-farmed and pond-farmed carp using stable isotope and multi-element analysis of fish scales with chemometrics

Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios and multi-element signatures of pooled fish scales were used to differentiate wild, lake-farmed and pond-farmed carp from Dongting Lake, China. Fish scales were found to be important archives for the dietary history and trophic level of wild and farmed fish, indicating their food sources. δ¹³C and δ¹⁵N values of pond-farmed carp scales were comparatively enriched to wild and lake-farmed carp due to their animal protein-derived feeds. Multi-element compositions of fish scales also showed significant differences between wild and farmed fish. A partial least squares discriminant analysis (PLS-DA) model correctly discriminated the three carp groups. Discrimination accuracies of wild, lake-farmed and pond-farmed carp were 100%, 95%, and 100% for the training set, and 100% for the testing set. This strategy provides a promising non-lethal alternative method to combat mislabeling of freshwater carp from different farming methods.

Effect of polysaccharides on the gel characteristics of "Yu Dong" formed with fish (Cyprinus carpio L.) scale aqueous extract

A novel protein-based gel named "Yu dong" prepared with fish (Cyprinus carpio L.) scale aqueous extract and enhanced by polysaccharides is described in this study. The effects of pectin, alginate, and sodium carboxyl methyl cellulose (CMC-Na) on FS gel formation, stability, textural characteristics, microstructure, and water distribution were evaluated. The results indicated the viscosity of the FS gels decreased and changed slowly as the addition of pectin. While, the addition of alginate enhanced the formation of FS gels. As pectin addition in FS gels, the transition temperature decreased. When alginate and CMC-Na was added to the FS gels, the transition temperature increased. The addition of pectin, alginate, and CMC-Na to the FS gels significantly increased G_r from 44.5% to 71.99%, 61.86%, and 71.35%, respectively. Gel strength increased significantly as the addition of pectin, alginate, and CMC-Na. LF-NMR results showed that a moderate amount (0.2%) of polysaccharides bonded the protein and water more tightly, which was consistent with the SEM results showing gel structure with more uniform pores. This study provides a direct application of FS protein in preparing of gel food, which showing a better way to utilize the abandoned fish resource.

Contributions of intermolecular bonding and lubrication to the mechanical behavior of a natural armor

Among many dermal armors, fish scales have become a source of inspiration in the pursuit of "next-generation" structural materials. Although fish scales function in a hydrated environment, the role of water and intermolecular hydrogen bonding to their unique structural behavior has not been elucidated. Water molecules reside within and adjacent to the interpeptide locations of the collagen fibrils of the elasmodine and provide lubrication to the protein molecules during deformation. We evaluated the contributions of this lubrication and the intermolecular bonding to the mechanical behavior of elasmodine scales from the Black Carp (Mylopharyngodon piceus). Scales were exposed to polar solvents, followed by axial loading to failure and the deformation mechanisms were characterized via optical mechanics. Displacement of intermolecular water molecules by liquid polar solvents caused significant (p ≤ 0.05) increases in stiffness, strength and toughness of the scales. Removal of this lubrication decreased the capacity for non-linear deformation and toughness, which results from the increased resistance to fibril rotations and sliding caused by molecular friction. The intermolecular lubrication is a key component of the "protecto-flexibility" of scales and these natural armors as a system; it can serve as an important component of biomimetic-driven designs for flexible armor systems. STATEMENT OF SIGNIFICANCE: The natural armor of fish has become a topic of substantial scientific interest. Hydration is important to these materials as water molecules reside within the interpeptide locations of the collagen fibrils of the elasmodine and provide lubrication to the protein molecules during deformation. We explored the opportunity for tuning the mechanical behavior of scales as a model for next-generation engineering materials by adjusting the extent of hydrogen bonding with polar solvents and the corresponding interpeptide molecular lubrication. Removal of this lubrication decreased the capacity for non-linear deformation and toughness due to an increase in resistance to fibril rotations and sliding as imparted by molecular friction. We show that intermolecular lubrication is a key component of the "protecto-flexibility" of natural armors and it is an essential element of biomimetic approaches to develop flexible armor systems.

Light microscopic studies to evaluate fish scales as non-invasive indicators of heavy metal-contaminated waters

Heavy metal pollution in aquatic bodies is a matter of serious concern for aquatic fauna and human health. This study evaluated the effect of heavy metals on structural aberrations in fish scales of freshwater Indian major carp Labeo rohita. Scales from two size groups-lesser than and equal to 40 cm and greater than 40 cm-collected from three markets of Ludhiana district for a period of 6 months were assessed. The values of Pb, Zn and Cr in fish scales exceeded the permissible limits. Structural alterations such as distorted focus, damaged and eroded circuli, distorted pattern of circuli, damaged margins of scales, dispersed chromatophores, disorganised radii and damaged tubercles were observed on the dorsal surface of scales using light microscopy. It is postulated that heavy metals would be responsible for structural anomalies on scales as their accumulation was higher in larger fishes which have been exposed to metals for longer duration. These observations clearly suggest that fish scales are effective non-invasive indicator of water quality where fish have been reared and cultured.

Comparative assessment of the interface between poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and fish scales in composites: Preparation, characterization, and applications

Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites containing fish scales (FSs) were prepared and used in the fabrication of three-dimensional printing filaments. Maleic anhydride (MA)-grafted polyhydroxyalkanoate (PHBV-g-MA) and FS were used to improve the compatibility of FS within a PHBV matrix. Mechanical and morphological characterization indicated that improved adhesion between FS and PHBV-g-MA enhanced the tensile strength of the composite compared with that of PHBV/FS. The PHBV-g-MA/FS composites were also more water-resistant than the PHBV/FS composites. Human foreskin fibroblasts (FBs) were seeded on two series of these composites to assess cytocompatibility. FB proliferation was greater on PHBV/FS composites than on PHBV-g-MA/FS composites. Cell-cycle assays with FBs on PHBV/FS and PHBV-g-MA/FS series composites were unaffected. Moreover, FS enhanced the antioxidant and antimicrobial properties of PHBV-g-MA/FS and PHBV/FS composites, demonstrating the potential of PHBV-g-MA/FS and PHBV/FS composites for biomedical material applications.

α-Melanocyte-stimulating hormone promotes bone resorption resulting from increased osteoblastic and osteoclastic activities in goldfish

We examined the effects of α-melanocyte-stimulating hormone (α-MSH) on bone metabolism using regenerating goldfish scales. Normally developed scales on the bodies of goldfish were removed to allow the regeneration of scales under anesthesia. Thereafter, the influence of α-MSH on the regeneration of goldfish scales was investigated in vivo. In brief, α-MSH was injected at a low dose (0.1 μg/g body weight) or a high dose (1 μg/g body weight) into goldfish every other day. Ten days after removing the scales, we collected regenerating scales and analyzed osteoblastic and osteoclastic activities as respective marker enzyme (alkaline phosphatase for osteoblasts, tartrate-resistant acid phosphatase for osteoclasts) activity in the regenerating scales as well as plasma calcium levels. At both doses, osteoblastic and osteoclastic activities in the regenerating scales increased significantly. Plasma calcium concentrations in the α-MSH-treated group (high doses) were significantly higher than those in the control group. Next, in vitro experiments were performed to confirm the results of in vivo experiments. In the cultured regenerating scales, osteoblastic and osteoclastic activities significantly increased with α-MSH (10^-7 and 10^-6 M) treatment. In addition, real-time PCR analysis indicated that osteoclastogenesis in α-MSH-treated scales was induced by the receptor activator of the NF-κB/receptor activator of the NF-κB ligand/osteoprotegerin pathway. Furthermore, we found that α-MSH receptors (melanocortin receptors 4 and 5) were detected in the regenerating scales. Thus, in teleosts, we are the first to demonstrate that α-MSH functions in bone metabolism and promotes bone resorption via melatonin receptors 4 and/or 5.

The limiting layer of fish scales: Structure and properties

Fish scales serve as a flexible natural armor that have received increasing attention across the materials community. Most efforts in this area have focused on the composite structure of the predominately organic elasmodine, and limited work addresses the highly mineralized external portion known as the Limiting Layer (LL). This coating serves as the first barrier to external threats and plays an important role in resisting puncture. In this investigation the structure, composition and mechanical behavior of the LL were explored for three different fish, including the arapaima (Arapaima gigas), the tarpon (Megalops atlanticus) and the carp (Cyprinus carpio). The scales of these three fish have received the most attention within the materials community. Features of the LL were evaluated with respect to anatomical position to distinguish site-specific functional differences. Results show that there are significant differences in the surface morphology of the LL from posterior and anterior regions in the scales, and between the three fish species. The calcium to phosphorus ratio and the mineral to collagen ratios of the LL are not equivalent among the three fish. Results from nanoindentation showed that the LL of tarpon scales is the hardest, followed by the carp and the arapaima and the differences in hardness are related to the apatite structure, possibly induced by the growth rate and environment of each fish.

STATEMENT OF SIGNIFICANCE

The natural armor of fish, turtles and other animals, has become a topic of substantial scientific interest. The majority of investigations have focused on the more highly organic layer known as the elasmodine. The present study addresses the highly mineralized external portion known as the Limiting Layer (LL). Specifically, the structure, composition and mechanical behavior of the LL were explored for three different fish, including the arapaima (Arapaima gigas), the tarpon (Megalops atlanticus) and the carp (Cyprinus carpio). Results show that there are significant differences in the surface morphology of the LL from posterior and anterior regions in the scales, and between the three species. In addition, the composition of the LL is also unique among the three fish. Results from nanoindentation showed that the LL of tarpon scales is the hardest, followed by the carp and the arapaima and the differences in hardness are related to the apatite structure, possibly induced by the growth rate and environment of each fish. In addition, a new feature was indentified in the LL, which has not been discussed before. As such, we feel this work is unique and makes a significant contribution to the field.

Assessment of fish scales waste as a low cost and eco-friendly adsorbent for removal of an azo dye: Equilibrium, kinetic and thermodynamic studies

In this study, AB113 dye was successfully sequestered using a novel adsorbent made of mixed fish scales (MFS). The influence of adsorbent dosage, initial pH, temperature, initial concentration and contact time on the adsorption performance was investigated. The surface chemistry and morphology of the adsorbent were examined by FTIR, TGA and SEM. Amides, phosphate and carbonate groups were evidently responsible for the high affinity of MFS towards the dye. The adsorption equilibrium and kinetic were well described by Langmuir and pseudo-second-order models, respectively. The maximum adsorption capacities of MFS were 145.3-157.3mg/g at 30-50°C. The adsorption of AB113 dye onto the adsorbent was exothermic and spontaneous as reflected by the negative enthalpy and Gibbs energy changes. The results support MFS asa potential adsorbent for AB113 dye removal.

Historical record of trace elements (1983-2007) in scales from Atlantic salmon (Salmo salar): Study of past metal contamination from a copper mine (Ulla River, NW Iberian Peninsula)

The chemical composition of fish scales has been reported to reflect the composition of the waters in which fish have been resident, therefore having the potential for the assessment of temporal trends in watershed water quality. Here we studied the historical (1983-2007) metal contamination in the Ulla river (NW Iberian Peninsula) watershed - impacted by a Cu mine that was in operation from 1973 until 1988 - by means of the analysis of major and trace elements in salmon scales. Results indicate the presence of a significant contamination for several metals (especially Cu, Au, Ag, Sb, Zn) during the 1980's. Concentrations of Cu in salmon scales during the influence of the mine (1983-1990) were 20 ± 5 μg/g, exceeding the values for the recent years (1995-2007): 1.8 ± 0.4 μg/g. Concentrations for Au in these two periods were 31 ± 12 and 2.1 ± 1.2 ng/g; for Ag: 21 ± 4 and 4 ± 2 ng/g; for Sb: 48 ± 21 and 15 ± 4 ng/g; and for Zn: 133 ± 16 and 93 ± 10 μg/g. The estimated concentrations of dissolved copper during the operation of the mine indicate a scenario of toxic effects due to sensory impairments in the salmon, and a reduction in scales calcification. The results presented here demonstrate that the analysis of trace elements in archived fish scales is a suitable tool for the reconstruction of the past contamination in aquatic systems, and it can be also used as a non-lethal approach for biomonitoring purposes.

In vitro screening for estrogenic endocrine disrupting compounds using Mozambique tilapia and sea bass scales

A wide range of estrogenic endocrine disruptors (EDCs) are accumulating in the environment and may disrupt the physiology of aquatic organisms. The effects of EDCs on fish have mainly been assessed using reproductive endpoints and in vivo animal experiments. We used a simple non-invasive assay to evaluate the impact of estrogens and EDCs on sea bass (Dicentrarchus labrax) and tilapia (Oreochromis mossambicus) scales. These were exposed to estradiol (E2), two phytoestrogens and six anthropogenic estrogenic/anti-estrogenic EDCs and activities of enzymes related to mineralized tissue turnover (TRAP, tartrate-resistant acid phosphatase and ALP, alkaline phosphatase) were measured. Semi-quantitative RT-PCR detected the expression of both membrane and nuclear estrogen receptors in the scales of both species, confirming scales as a target for E2 and EDCs through different mechanisms. Changes in TRAP or ALP activities after 30minute and 24h exposure were detected in sea bass and tilapia scales treated with E2 and three EDCs, although compound-, time- and dose-specific responses were observed for the two species. These results support again that the mineralized tissue turnover of fish is regulated by estrogens and reveals that the scales are a mineralized estrogen-responsive tissue that may be affected by some EDCs. The significance of these effects for whole animal physiology needs to be further explored. The in vitro fish scale bioassay is a promising non-invasive screening tool for E2 and EDCs effects, although the low sensitivity of TRAP/ALP quantification limits their utility and indicates that alternative endpoints are required.

Fish Scales as Potential Substrate for Production of Alkaline Protease and Amino Acid Rich Aqua Hydrolyzate by Bacillus altitudinis GVC11

Fish processing industries generate large quantities of fish scales as processing waste, if not treated leading to environmental pollution. Fish scales are hard to degrade, hence cause difficulty in waste management. In this context present study was made to utilize fish scales as substrate for the production of alkaline protease by Bacillus altitudinis GVC11 and subsequently amino acid rich aqua hydrolyzate. B. altitudinis GVC11 efficiently utilized five types of fish scales as substrates and produced maximum alkaline protease using Labeo rohita (28,150 U/mL) followed by Catla catla (23,320 U/mL) at 48 h and Cyprinus carpio (17,146 U/mL) Mugil cephalus (18,917 U/mL), Cirrhinus mrigala (12,430 U/mL) at 72 h. The HPLC analysis of protein hydrolyzate obtained after fermentation was enriched in essential amino acids, leucine, isoleucine, phenylalanine, lysine and non-essential amino acids, tyrosine, arginine and cysteine which can be used as animal feed supplement and organic fertilizer.

A comparative study of bio-inspired protective scales using 3D printing and mechanical testing

Flexible natural armors from fish, alligators or armadillo are attracting an increasing amount of attention for their unique combinations of hardness, flexibility and light weight. The extreme contrast of stiffness between hard scales and surrounding soft tissues gives rise to unusual and attractive mechanisms, which now serve as models for the design of bio-inspired armors. Despite this growing interest, there is little guideline for the choice of materials, optimum thickness, size, shape and arrangement for the protective scales. In this work, we explore how the geometry and arrangement of hard scales can be tailored to promote scale-scale interactions. We use 3D printing to fabricate arrays of scales with increasingly complex geometries and arrangements, from simple squares with no overlap to complex ganoid-scales with overlaps and interlocking features. We performed puncture tests and flexural tests on each of the 3D printed materials, and we report the puncture resistance - compliance characteristics of each design on an Ashby chart. The interactions between the scales can significantly increase the resistance to puncture, and these interactions can be maximized by tuning the geometry and arrangement of the scales. Interestingly, the designs that offer the best combinations of puncture resistance and flexural compliance are similar to the geometry and arrangement of natural teleost and ganoid scales, which suggests that natural evolution has shaped these systems to maximize flexible protection. This study yields new insights into the mechanisms of natural dermal armor, and also suggests new designs for personal protective systems.

STATEMENT OF SIGNIFICANCE

Flexible natural armors from fishes, alligators or armadillos are attracting an increasing amount of attention for their unique and attractive combinations of hardness, flexibility and low weight. Despite a growing interest in bio-inspired flexible protection, there is still little guideline for the choice of materials, optimum thickness, size, shape and arrangement of the protective scales. In this work, we explore how the geometry and arrangement of hard scales affect puncture resistance and flexural compliance, using 3D printing and mechanical testing. Our main finding is that the performance of the scaled skin in terms of puncture resistance can be significantly improved by slight changes in their geometry and arrangement. Our results also suggest that natural evolution has shaped scaled skins to maximize flexible protection. This study yields new insights into the mechanics of natural dermal armors, and also suggests new designs for personal protective systems.

Non-ideal effects in bending response of soft substrates covered with biomimetic scales

Biomimetic scales are known to substantially alter the mechanics response of the underlying substrate engendering complex nonlinearities that can manifest even in small deformations due to scales interaction. This interaction is typically modeled using a-priori homogenization with an enforced periodicity of engagement. Such a framework is fairly useful especially when dealing with the structural length scale which is at least one order of magnitude greater than the scales themselves since individual tracking of a large number of scales become insurmountable. On the other hand, this scheme makes several assumptions whose validity has not yet been investigated including infinite length of the substrate and rigidity of the scales. The validity of these assumptions and the accuracy and limitations of associated analytical models are investigated. Finite element based numerical studies were carried out to identify the critical role of edge effects and other non-ideal behavior such as violation of periodicity and nonlinear constitutive response on scale rotation. Our investigation shows that several important quantities show a strong saturation characteristic which justify many of the simplifying assumptions whereas others need much greater care.

Effects of hyperglycemia on bone metabolism and bone matrix in goldfish scales

Increased risk of fracture associated with type 2 diabetes has been a topic of recent concern. Fracture risk is related to a decrease in bone strength, which can be affected by bone metabolism and the quality of the bone. To investigate the cause of the increased fracture rate in patients with diabetes through analyses of bone metabolism and bone matrix protein properties, we used goldfish scales as a bone model for hyperglycemia. Using the scales of seven alloxan-treated and seven vehicle-treated control goldfish, we assessed bone metabolism by analyzing the activity of marker enzymes and mRNA expression of marker genes, and we measured the change in molecular weight of scale matrix proteins with SDS-PAGE. After only a 2-week exposure to hyperglycemia, the molecular weight of α- and β-fractions of bone matrix collagen proteins changed incrementally in the regenerating scales of hyperglycemic goldfish compared with those of euglycemic goldfish. In addition, the relative ratio of the γ-fraction significantly increased, and a δ-fraction appeared after adding glyceraldehyde-a candidate for the formation of advanced glycation end products in diabetes-to isolated type 1 collagen in vitro. The enzymatic activity and mRNA expression of osteoblast and osteoclast markers were not significantly different between hyperglycemic and euglycemic goldfish scales. These results indicate that hyperglycemia is likely to affect bone quality through glycation of matrix collagen from an early stage of hyperglycemia. Therefore, non-enzymatic glycation of collagen fibers in bone matrix may lead to the deterioration of bone quality from the onset of diabetes.

Tissue responsiveness to estradiol and genistein in the sea bass liver and scale

As in mammals, estrogens in fish are essential for reproduction but also important regulators of mineral homeostasis. Fish scales are a non-conventional target tissue responsive to estradiol and constitute a good model to study mineralized tissues effects and mechanisms of action of estrogenic compounds, including phytoestrogens. The responsiveness to estradiol and the phytoestrogen genistein, was compared between the scales and the liver, a classical estrogenic target, in sea bass (Dicentrarchus labrax). Injection with estradiol and genistein significantly increased circulating vitellogenin (for both compounds) and mineral levels (estradiol only) and genistein also significantly increased scale enzymatic activities suggesting it increased mineral turnover. The repertoire, abundance and estrogenic regulation of nuclear estrogen receptors (ESR1, 2a and 2b) and membrane G-protein receptors (GPER and GPER-like) were different between liver and scales, which presumably explains the tissue-specific changes detected in estrogen-responsive gene expression. In scales changes in gene expression mainly consisted of small rapid increases, while in liver strong, sustained increases/decreases in gene expression occurred. Similar but not overlapping gene expression changes were observed in response to both estradiol and genistein. This study demonstrates for the first time the expression of membrane estrogen receptors in scales and that estrogens and phytoestrogens, to which fish may be exposed in the wild or in aquaculture, both affect liver and mineralized tissues in a tissue-specific manner.

Element distribution over the surface of fish scales and its connection to the geochemical environment of habitats: a potential biogeochemical tag

The elemental content of fish scales is known to be a reliable biogeochemical tag for tracing the origin of fishes. In this study, this correlation is further confirmed to exist on the surface of fish scales using a novel environmental analytical method, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), which bypasses several complicated sample preparation procedures such as acid digestion and pre-concentration. The results suggest that the elemental ratios of Sr/Ca, Ba/Ca, and Mn/Ca on the surface of fish scales are strongly correlated with the geochemical environment of their original habitat. This correlation is further demonstrated to be sensitive to variation of water in the habitat due to the adsorbed inorganic ions. In this sense, the limitation of fish scales as a biogeochemical tag is the sensitivity of LA-ICP-MS toward the studied elements. Graphical abstract Illustration of the connection between element distribution pattern over the surface of fish scales and biogeochemical environment of its habitat.

Biomimetic synthesis of silver nanoparticles using the fish scales of Labeo rohita and their application as catalysts for the reduction of aromatic nitro compounds

In this article, a cleaner, greener, cheaper and environment friendly method for the generation of self assembled silver nanoparticles (Ag NPs) applying a simple irradiation technique using the aqueous extract of the fish scales (which is considered as a waste material) of Labeo rohita is described. Gelatin is considered as the major ingredient responsible for the reduction as well as stabilisation of the self assembled Ag NPs. The size and morphology of the individual Ag NPs can be tuned by controlling the various reaction parameters, such as temperature, concentration, and pH. Studies showed that on increasing concentration and pH Ag NPs size decreases, while on increasing temperature, Ag NPs size increases. The present process does not need any external reducing agent, like sodium borohydride or hydrazine or others and gelatin itself can play a dual role: a 'reducing agent' and 'stabilisation agent' for the formation of gelatin-Ag NPs colloidal dispersion. The synthesized Ag NPs were characterised by Ultraviolet-Visible spectroscopy (UV-Vis), Transmission electron microscopy (TEM) and Selected area electron diffraction (SAED) analyses. The synthesized Ag NPs was used to study the catalytic reduction of various aromatic nitro compounds in aqueous and three different micellar media. The hydrophobic and electrostatic interaction between the micelle and the substrate is responsible for the catalytic activity of the nanoparticles in micelle.

Protective role of Arapaima gigas fish scales: structure and mechanical behavior

The scales of the arapaima (Arapaima gigas), one of the largest freshwater fish in the world, can serve as inspiration for the design of flexible dermal armor. Each scale is composed of two layers: a laminate composite of parallel collagen fibrils and a hard, highly mineralized surface layer. We review the structure of the arapaima scales and examine the functions of the different layers, focusing on the mechanical behavior, including tension and penetration of the scales, with and without the highly mineralized outer layer. We show that the fracture of the mineral and the stretching, rotation and delamination of collagen fibrils dissipate a significant amount of energy prior to catastrophic failure, providing high toughness and resistance to penetration by predator teeth. We show that the arapaima's scale has evolved to minimize damage from penetration by predator teeth through a Bouligand-like arrangement of successive layers, each consisting of parallel collagen fibrils with different orientations. This inhibits crack propagation and restricts damage to an area adjoining the penetration. The flexibility of the lamellae is instrumental to the redistribution of the compressive stresses in the underlying tissue, decreasing the severity of the concentrated load produced by the action of a tooth. The experimental results, combined with small-angle X-ray scattering characterization and molecular dynamics simulations, provide a complete picture of the mechanisms of deformation, delamination and rotation of the lamellae during tensile extension of the scale.