title: Portable oxidative stress sensor: dynamic and non-invasive measurements of extracellular H₂O₂ released by algae.
abstract: Reactive oxygen species (ROS) generated by aerobic organisms are essential for physiological processes such as cell signaling, apoptosis, immune defense and oxidative stress mechanisms. Unbalanced oxidant/antioxidant budgets are involved in many diseases and, therefore, the sensitive measurement of ROS is of great interest. Here, we present a new device for the real-time monitoring of oxidative stress by measuring one of the most stable ROS, namely hydrogen peroxide (H2O2). This portable oxidative stress sensor contains the heme protein cytochrome c (cyt c) as sensing element whose spectral response enables the detection of H2O2 down to a detection limit of 40 nM. This low detection limit is achieved by introducing cyt c in a random medium, enabling multiscattering that enhances the optical trajectory through the cyt c spot. A contact microspotting technique is used to produce reproducible and reusable cyt c spots which are stable for several days. Experiments in static and microfluidic regimes, as well as numerical simulations demonstrate the suitability of the cyt c/H2O2 reaction system for the real-time sensing of the kinetics of biological processes without H2O2 depletion in the measurement chamber. As an example, we detect the release of H2O2 from the green alga Chlamydomonas reinhardtii exposed to either 180 nM functionalized CdSe/ZnS core shell quantum dots, or to 10 mg/l TiO2 nanoparticles. The continuous measurement of extracellular H2O2 by this optical sensor with high sensitivity is a promising new means for real-time cytotoxicity tests, the investigation of oxidative stress and other physiological cell processes.
authors.affiliation: Nanophotonics and Metrology Laboratory (NAM), Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland.
authors.forename: Volodymyr B
authors.initials: VB
authors.lastname: Koman
authors.affiliation: Nanophotonics and Metrology Laboratory (NAM), Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland. Electronic address: christian.santschi@epfl.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Santschi
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10, route de Suisse, 1290 Versoix, Switzerland.
authors.forename: Nadia R
authors.initials: NR
authors.lastname: von Moos
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10, route de Suisse, 1290 Versoix, Switzerland.
authors.forename: Vera I
authors.initials: VI
authors.lastname: Slaveykova
authors.affiliation: Nanophotonics and Metrology Laboratory (NAM), Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland.
authors.forename: Olivier J F
authors.initials: OJF
authors.lastname: Martin
mesh_terms: D017209:Apoptosis; D015374:Biosensing Techniques; D016825:Chlamydomonas reinhardtii / Q000737:chemistry / Q000502:physiology; D045304:Cytochromes c / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000302:isolation & purification*; D053758:Nanoparticles / Q000737:chemistry; D018384:Oxidative Stress; D045663:Quantum Dots / Q000737:chemistry; D014025:Titanium / Q000737:chemistry
chemical_list: C009495:titanium dioxide; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D014025:Titanium
keywords: Cytochrome c; Hydrogen peroxide; Multiscattering; Optical detection; Toxicity