Surface-Enhanced Raman Scattering Microspectroscopy Enables the Direct Characterization of Biomineral-Associated Organic Material on Single Calcareous Microskeletons.

Alessandro Silvestri,Peter Fratzl,André Scheffel,Jürgen Pätzold,Damien Faivre

doi:10.1021/acs.jpclett.0c02041

Abstract

Biominerals are composite materials with inorganic and organic components. The latter provide insights into how organisms control mineralization and, if derived from micro/nannofossils, into past climates. Many calcifying organisms cannot be cultured or are extinct; the only materials available for their study are therefore complex environmental samples in which the organism of interest may only be a minor component. There is currently no method for characterizing the biomineral-associated organic material from single particles within such assemblages, so its compositional diversity is unknown. Focusing on coccoliths, we demonstrate that surface-enhanced Raman scattering microspectroscopy can be used to determine the origin and composition of fossil organic matter at the single-particle level in a heterogeneous micro/nannofossil assemblage. This approach may find applications in the study of micro/nannofossil assemblages and uncultivated species, providing evolutionary insights into the macromolecular repertoire involved in biomineralization.

Highlights

Biominerals are composite materials with inorganic and organic components
Raman microspectroscopy can characterize and identify organic and inorganic phases at the submicrometer scale,[16−19] making it an attractive tool for the analysis of samples that are not suited for biochemical analyses, such as calcareous micro/ nannofossil assemblages
Focusing on coccoliths, which are the calcitic scales of single-celled coccolithophorid algae[20] and prime components of calcareous micro/nannofossil sediments as well as interesting models in the context of biomimetic materials chemistry, we demonstrate that surface-enhanced Raman

Summary

Introduction

Biominerals are composite materials with inorganic and organic components. The latter provide insights into how organisms control mineralization and, if derived from micro/nannofossils, into past climates. We demonstrate the value of the SERS microspectroscopy approach with mixed-species micro/nannofossil samples, where we acquired biochemical information from coccoliths of Calcidiscus species and coexisting fragments of foraminifera skeletons individually, without separating them from each other and other calcareous particles contained in the ∼470000 years (470 ka) old calcareous raw material.

Results

Conclusion