Stage M2 – Syntheses of CaCO3 minerals colored by bio-based organic pigments extracted from sea urchins  – LCMCP

Syntheses of CaCO3 minerals colored by bio-based organic pigments extracted from sea urchins

MASTER 2 Internship Proposal 2020

Host Institution
Name : LCMCP : Laboratoire Chimie de la Matière Condensée de Paris
Address : Tour 44, 4ème étage, 4 place Jussieu, 75005 Paris
Director (legal representative) : Christian Bonhomme
Tel : 01 44 27 62 95
E-mail : christian.bonhomme@sorbonne-universite.fr

Hosting Team
Team leader: Thierry Azaïs
Web site: https://lcmcp.upmc.fr/site/smiles/
Direct Supervisor: Marie Albéric
Position: Chargée de recherche CNRS
Tel: 01 44 27 56 75
E-mail: marie.alberic@sorbonne-universite.fr
Internship period: 5 mois from February 2020
Salary: Yes

Scientific Project:
1. Project
Sea urchin spines show intense and diverse colors (from purple to green) that are due to a family of organic molecules, the polyhydroxylated-naphthoquinone (PHNQ) [1] (Figure A and B). Although the majority of synthetic organic pigments (non-water soluble) hardly disperse in the medium to be colored and fade rapidly under sunlight, PHNQ mass-color and provide long-lasting colors to sea urchin spines.
These remarkable properties are likely due to the encapsulation of the PHNQ molecules within the crystalline biogenic calcite, which protects the organic pigments from the external environment. The PHNQ encapsulation takes place during the coupled pigmentation and biomineralization processes.
PHNQ molecules are first localized in the so-called red-spherule cells (Figure C) and progressively integrate the growing mineral (=biomineralization) (Figure D). Biomineralization in sea urchin involves
the presence of amorphous calcium carbonate (ACC) precursors phases [2,3], which are thermodynamically unstable under ambient conditions but can be temporarily stabilized by inorganic ions such as Mg2+ and macromolecules, mostly N-glycosylated proteins [4]. During ACC
crystallization, Mg2+ as well as diverse macromolecules (proteins, lipids, polysaccharides, metabolites) and PHNQ are incorporated into the biogenic calcite.
This project aims at synthetizing colored hybrid CaCO3 based materials bio-inspired by the pigmentation and biomineralization processes occurring in sea urchin spines and therefore via the synthesis of ACC-PHNQ samples.

2. Specific techniques and methods

PHNQ molecules will be extracted from the red-spherules cells located in the coelomic fluid (≈blood) of the sea urchins by centrifugation techniques and osmotic shock approaches. The molecular structure of the PHNQ molecules will be elucidated by 1H/13C solution state NMR. Based on the literature, two strategies will be employed to synthetize colored CaCO3 crystals with occluded PHNQ via the formation of ACC particles. 1) Spontaneous precipitation by direct mixing of
CaCl2 into Na2CO3 solution [5] containing water soluble PHNQ will be performed (Figure E) with a dedicated automatic device that allows the simultaneous measurement of pH and Ca2+ activity during the ACC synthesis. 2) Slow carbonation diffusion methods [6] will be also performed in ethanol with the ethanol-soluble PHNQ fractions (Figure F). Crystallization of the samples will be induced under heating and/or controlled humidity. Due to the complexity of the natural PHNQ mixture, simplified and commercially available molecules (lawsone and naphthazarin) will also be considered.
The PHNQ-ACC hybrid samples will be characterized by ATR-FTIR and the incorporation of the PHNQ within the CaCO3 crystals will be studied by TG analyses and observed by optical microscopy.
The likely stabilization effect of the PHNQ on the ACC phases will be determined by DSC. Finally, ACC nanoparticles and faceted CaCO3 crystals will be observed by SEM and the nature of the crystalline polymorphs (calcite, vaterite, aragonite) will be determined by XRD.

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Stage Master 2 /janvier-juin 2020
Equipe ARNA (ChemBioPharm) / IMBE

Mots clés: larve éphyrule, écotoxicologie comportementale, bioindicateur, contaminants
aquatiques
Laboratoires: équipe ARNA (ChemBioPharm) / IMBE
Contacts : philippe.barthelemy@inserm.fr/alain.thiery@imbe.fr
Gratification: gratification de M2 statutaire (textes ?), soit 577.50 euros mensuel (non imposable)

Contexte scientifique et Objectif du stage
Dans le cadre de ce stage, le (ou la) candidat(e) sera chargé(e) de la détermination de la toxicité et de l’impact environnemental de nouveaux systèmes de décontamination développés au sein des laboratoires INSEM U1212 et LCPO (Université de Bordeaux) sur un biomarqueur Aurelia aurita ephyrea (Figure 1). Chaque constituant sera étudié seul et en mélange à
différentes concentrations en phase aqueuse. Ce travail permettra d’évaluer l’impact des systèmes de décontamination dans le but d’évaluer la toxicité et l’impact environnemental potentiel.
Figure 1: Gauche, cycle de vie pélagique et benthique. Droite, Les éphyrules sont incubées dans différentes conditions et filmées à l’aide de 2 cameras (haut). La mobilité et la fréquence de pulsations sont enregistrées en fonction de différentes conditions (concentration en polluants). Dans ce projet, les polluants seront remplacés par des systèmes bioinspirés formulés.
Ce nouveau modèle écotoxicologique (Aurelia aurita ephyrea) hautement sensible proposé dans le cadre de ce projet a été développé sur la base d’une collaboration entre les professeurs Alain Thiéry (IMBE) et Philippe Barthélémy (ARNA). Il met l’accent sur l’évaluation de la vulnérabilité et la résilience des eaux salées (estuaires, lagunes, eaux côtières). 

Encadrement : Le stage se déroulera en majeure partie à l’université de Bordeaux il sera coencadré par le professeur Philippe Barthélémy et Alain Thiéry

Profil recherché: étudiant(e) en écotoxicologie, présentant un intérêt certain pour la biologie/écologie des invertébrés marins.

Sélection de publications représentatives de l’équipe d’accueil :
Auffan et al., 2013. Role of molting on the biodistribution of CeO2 nanoparticles within Daphnia pulex. Water Res., 47: 3921-3930.
Patwa et al., 2015a. Accumulation of nanoparticles in ‘jellyfish’ mucus: a bio-inspired route to decontamination of nano-waster. Sci. Reports, 5:11387/DOI 10.1038/srep11387
Patwa et al., 2015b. Decontamination of nanoparticles from aqueous samples using supramolecular gels. Chem. Commun., 51: 2547-2550.

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