Cell surface receptors distinguish specific stimuli from biological noise, and underlying mechanisms depend on the organization of plasma membrane components. We exploited the statistical robustness of multiplexed Imaging Fluorescence Correlation Spectroscopy (ImFCS), to evaluate subtle diffusion differences of key components in the early stage of mast cell signaling by measuring their diffusion in live cells: FcεRI receptor for immunoglobulin E (IgE), tyrosine kinase Lyn anchored to the membrane inner leaflet, and transmembrane phosphatase PTPα. Our results confirm that the nanoscale distribution of signaling proteins is coordinately rearranged after the receptor is stimulated, such that changes in relatively weak interactions serve to transmit the signal across the membrane.
We report on monodisperse fluorescent core-shell silica nanoparticles (C dots) with enhanced brightness and photostability as compared to parent free dye in aqueous solution. Dots containing either tetramethylrhodamine or 7-nitrobenz-2-oxa-1,3-diazole dyes with diameters ranging from tens of nanometers to microns are discussed. The benefits of the core-shell architecture are described in terms of enhanced fluorescent yield of the fluorophores in the quasi-solid-state environment within the particle as compared with parent free dye in water. Several applications of these particles in the fields of photonics and the life sciences are discussed. Specifically, fluorescent core-shell silica nanoparticles are investigated as an active medium for photonic building blocks assembled on zinc sulfide-based seed particles. Initial assembly results for these composite raspberry structures are shown. Finally, applications in the life sciences are explored, including targeting of specific antibody receptors using these single-emission nanoparticles. We expand on single-emission core-shell architecture to incorporate environmentally-sensitive fluorophores to create quantitative ratiometric nanoscale sensors capable of interrogating chemical concentrations on the sub-cellular to molecular levels and demonstrate initial results of intracellular pH imaging. The concept of a single particle laboratory (SPL) is introduced as an active investigator of its environment.
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