‘Mammothfluidics’: Amino acid dating of fossil mammal tooth enamel using a modular microfluidic system

Dating fossil samples helps reconstruct evolutionary history, aiding conservation efforts and mitigating climate change impacts. Amino acid geochronology of tooth enamel using the intra-crystalline protein decomposition (IcPD) approach allows direct dating of mammal teeth over Quaternary timescales (∼2.5 million years), beyond the limits of radiocarbon dating (∼50,000 years). However current methods require specialist equipment and relatively lengthy processing times. We developed a modular microfluidic system for chiral amino acid analysis of tooth enamel samples, consisting of three sequential glass microfluidic devices for sample bleaching, release of hydrolysable amino acids, and biphasic separation. Relative concentrations and D/L values of key amino acids were measured using reverse-phase high performance liquid chromatography (RP-HPLC). The microfluidic method reduced sample amounts from ∼15 mg to ∼1 mg and bleaching time from 72 h to 2 h. Amino acid compositions of modern and fossil samples were similar between the microfluidic approach and standard IcPD method, with good agreement up to D/L values ∼0.5 for phenylalanine (Phe) and glutamic acid (Glx). The method worked successfully across various genera and operators, with reduced sample mass and analysis time. This approach results in less destructive sampling of precious fossil samples and enables preparation steps in non-specialist labs, potentially allowing IcPD dating within the fossils’ country.