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Updated: Sep 29, 2025
Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging
Published on: January 5, 2015
Development of a liposomal near-infrared fluorescence lactate assay for human blood
Simon Matoori1, David J Mooney2
1John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA; Wyss Institute Biologically Inspired Engineering, Harvard University, Boston, MA, 02115, USA; Faculté de Pharmacie, Université de Montréal, Montreal, QC H3T 1J4, Canada.
Abstract:
In emergency medicine, blood lactate is a commonly used biomarker of hypoxia (e.g., sepsis, trauma, cardiac arrest) but the median time to obtain the results from a clinical lactate test is 3 h. We recently developed a near-infrared fluorescent blood lactate assay based on a two-step enzymatic cascade in a vesicular reaction compartment. Previously, we reported a response of this assay to lactate-spiked bovine blood after 10 min. To develop a point-of-care test, we optimized this assay in commercial human blood, validated it in fresh capillary blood of healthy volunteers in an institutional review board-approved study, and improved the stability of the formulation. External pH and luminal enzyme concentrations were identified as key parameters of sensor response and kinetics, as they impact transmembrane lactate diffusion and turnover rate. The preparation process was also simplified and the stability was improved to allow storage at 4 °C for at least 5 days. The final formulation exhibited a strong and linear response to lactate-spiked human blood in a clinically relevant range, and accurately quantified a lactate standard at a clinically used cut-off in fresh capillary blood after 2 min. These findings motivate a clinical evaluation of this rapid and easy-to-use lactate assay.
