title: Single Cell "Glucose Nanosensor" Verifies Elevated Glucose Levels in Individual Cancer Cells.
abstract: Because the transition from oxidative phosphorylation to anaerobic glycolytic metabolism is a hallmark of cancer progression, approaches to identify single living cancer cells by their unique glucose metabolic signature would be useful. Here, we present nanopipettes specifically developed to measure glucose levels in single cells with temporal and spatial resolution, and we use this technology to verify the hypothesis that individual cancer cells can indeed display higher intracellular glucose levels. The nanopipettes were functionalized as glucose nanosensors by immobilizing glucose oxidase (GOx) covalently to the tip so that the interaction of glucose with GOx resulted in a catalytic oxidation of β-d-glucose to d-gluconic acid, which was measured as a change in impedance due to drop in pH of the medium at the nanopipette tip. Calibration studies showed a direct relationship between impedance changes at the tip and glucose concentration in solution. The glucose nanosensor quantified single cell intracellular glucose levels in human fibroblasts and the metastatic breast cancer lines MDA-MB-231 and MCF7 and revealed that the cancer cells expressed reproducible and reliable increases in glucose levels compared to the nonmalignant cells. Nanopipettes allow repeated sampling of the same cell, as cells remain viable during and after measurements. Therefore, nanopipette-based glucose sensors provide an approach to compare changes in glucose levels with changes in proliferative or metastatic state. The platform has great promise for mechanistic investigations, as a diagnostic tool to distinguish cancer cells from nonmalignant cells in heterogeneous tissue biopsies, as well as a tool for monitoring cancer progression in situ.
authors.affiliation: Biomolecular Engineering Department, University of California Santa Cruz , 1156 High Street, Santa Cruz, California 95064, United States.|Department of Physics, Faculty of Philosophy, Science and Letters at Ribeirão Preto, University of São Paulo , Avenida Bandeirantes 3900, Ribeirão Preto, São Paulo 14040-401, Brazil.
authors.forename: Raphael A S
authors.initials: RA
authors.lastname: Nascimento
authors.affiliation: Biomolecular Engineering Department, University of California Santa Cruz , 1156 High Street, Santa Cruz, California 95064, United States.
authors.forename: Rıfat Emrah
authors.initials: RE
authors.lastname: Özel
authors.affiliation: Biomolecular Engineering Department, University of California Santa Cruz , 1156 High Street, Santa Cruz, California 95064, United States.
authors.forename: Wai Han
authors.initials: WH
authors.lastname: Mak
authors.affiliation: Biomolecular Engineering Department, University of California Santa Cruz , 1156 High Street, Santa Cruz, California 95064, United States.|Department of Physics, Faculty of Philosophy, Science and Letters at Ribeirão Preto, University of São Paulo , Avenida Bandeirantes 3900, Ribeirão Preto, São Paulo 14040-401, Brazil.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Mulato
authors.affiliation: Department of Chemistry and Biochemistry, University of California Santa Cruz , 1156 High Street, Santa Cruz, California 95064, United States.
authors.forename: Bakthan
authors.initials: B
authors.lastname: Singaram
authors.affiliation: Biomolecular Engineering Department, University of California Santa Cruz , 1156 High Street, Santa Cruz, California 95064, United States.
authors.forename: Nader
authors.initials: N
authors.lastname: Pourmand
mesh_terms: D015374:Biosensing Techniques; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation; D004800:Enzymes, Immobilized / Q000737:chemistry; D005260:Female; D005942:Gluconates / Q000737:chemistry; D005947:Glucose / Q000302:isolation & purification* / Q000378:metabolism; D005949:Glucose Oxidase / Q000737:chemistry; D006801:Humans; D061986:MCF-7 Cells; D009362:Neoplasm Metastasis; D010085:Oxidative Phosphorylation; D059010:Single-Cell Analysis
chemical_list: D004800:Enzymes, Immobilized; D005942:Gluconates; D005949:Glucose Oxidase; D005947:Glucose; C030691:gluconic acid
keywords: biosensor; cancer metabolomics; intracellular glucose; nanopipette; nanopore; single cell