title: Two-photon nano-PEBBLE sensors: subcellular pH measurements.
abstract: Intracellular pH mapping is of great importance as it plays a critical role in many cellular events. Also, in tissue, pH mapping can be an indicator for the onset of cancer. Here we describe a biocompatible, targeted, ratiometric, fluorescent, pH sensing nano-PEBBLE (Photonic Explorer for Biomedical use with Biologically Localized Embedding) that is based on two-photon excitation. Two-photon excitation minimizes the photobleaching and cell autofluorescence drastically, leading to an increase in the signal-to-noise ratio. PEBBLE nanosensors provide a novel approach for introducing membrane impermeant dyes, like HPTS, into cells. We use both non-targeted and F3 peptide targeted PEBBLE nanosensors for intracellular pH measurement of 9L cells. The intracellular measurements suggest that the non-targeted nanosensors are mostly trapped in endosomes, whereas the F3 peptide targeting enables them to escape/avoid these acidic compartments. Combining the advantages of pH sensitive PEBBLE nanoparticles, including their specific targeting, with the advantages of two-photon microscopy provides an attractive and promising prospect for non-invasive real-time monitoring of pH inside cancer cells and tissues.
authors.affiliation: Biophysics, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Aniruddha
authors.initials: A
authors.lastname: Ray
authors.forename: Yong-Eun
authors.initials: YE
authors.lastname: Koo Lee
authors.forename: Tamir
authors.initials: T
authors.lastname: Epstein
authors.forename: Gwangseong
authors.initials: G
authors.lastname: Kim
authors.forename: Raoul
authors.initials: R
authors.lastname: Kopelman
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D058967:Contactin 1 / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000737:chemistry*; D038761:Photobleaching; D017785:Photons; D051381:Rats; D014407:Tumor Cells, Cultured
chemical_list: C548671:Cntn1 protein, rat; D058967:Contactin 1; D005456:Fluorescent Dyes