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Seashells are hierarchical bio-organic/mineral composites made of calcium carbonate (CaCO3) and an organic matrix (1-5 wt. %) composed mainly of proteins and polysaccharides. Fishery industry waste containing seashells from mussels, scallops, and oysters, represents an important environmental issue. The process is ecologically harmful and implies the loss of potentially useful biomaterials [1]. The valorization of seashell waste by transforming the CaCO3 crystals into biomimetic apatite micro/nanoparticles for biomedical applications may have a positive environmental impact besides economic profitability since the global market (including nano-sized, micron-sized, and higher sizes) is expected to grow in the next years. Different methods to transform biogenic CaCO3 into apatite nano/microparticles have been developed recently. They are mainly two-step processes involving calcination to CaO at 900-1000 °C followed by the reaction of a phosphate reagent (typically H3PO4) with the Ca(OH)2 produced by hydration of the CaO [2]. In this work, we have developed a one-step hydrothermal process to obtain biomimetic carbonated-apatite using oyster shells (Mg-calcite, 5 wt.% Mg) from the species Crassostrea gigas as model raw material. Shells were treated with NaClO 5% v/v to remove surface organic residues, crushed by a hammer mill, milled in a ball mill and sieved using a <45 ¿m mesh. The so obtained particles were submitted to hydrothermal treatment. Different experimental parameters were tested: P reagents (H3PO4, KH2PO4, and K2HPO4); P/Ca molar ratios (0.24, 0.6, and 0.96); temperature (25-200°C) and time (from 1 week to 2 months), without any pH adjustment. Characterization was performed by XRD, FTIR, Raman, SEM, TEM, DLS and TGA. The apatite/calcite ratio (wt.%) of the final precipitates was determined by Rietveld analysis using TOPAS 6.0 software. Among the many results, it is worth of mentioning that at the lowest experimental time used (1 week), the temperatures to o

We have developed a straightforward, one-pot, low-temperature hydrothermal method to transform oyster shell waste particles (bCCP) from the species Crassostrea gigas (Mg-calcite, 5 wt% Mg) into hydroxyapatite (HA) micro/nanoparticles. The influence of the P reagents (HPO, KHPO, and KHPO), P/bCCP molar ratios (0.24, 0.6, and 0.96), digestion temperatures (25-200 °C), and digestion times (1 week-2 months) on the transformation process was thoroughly investigated. At 1 week, the minimum temperature to yield the full transformation significantly reduced from 160 °C to 120 °C when using KHPO instead of KHPO at a P/bCCP ratio of 0.6, and even to 80 °C at a P/bCCP ratio of 0.96. The transformation took place via a dissolution-reprecipitation mechanism driven by the favorable balance between HA precipitation and bCCP dissolution, due to the lower solubility product of HA than that of calcite at any of the tested temperatures. Both the bCCP and the derived HA particles were cytocompatible for MG-63 human osteosarcoma cells and m17.ASC murine mesenchymal stem cells, and additionally, they promoted the osteogenic differentiation of m17.ASC, especially the HA particles. Because of their physicochemical features and biological compatibility, both particles could be useful osteoinductive platforms for translational applications in bone tissue engineering.

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Small forest patches embedded in agricultural (and peri-urban) landscapes in Western Europe play a key role for biodiversity conservation with a