1. -Ratiometric Quantitation - By incorporating both sensitive and insensitive dyes into the same particle, each particle contains an internal standard, allowing quantitation of analyte concentration independent of the particle concentration.

  2. -Core-shell Separation - By placing the sensor dyes in the shell, rather than homogeneously dispersing them throughout the particle, these dyes will experience the same environment and thus will indicate the same concentration. Analyte exposure is maximized, while retaining the beneficial dye-silica matrix interactions leading to brightness enhancement.  Furthermore, the reference dye is sequestered in the particle core, protected from environmental influences that could complicate quantitation.

  3. -Silica Matrix - In addition to dye-matrix enhancement effects, the amorphous silica matrix provides sufficient porosity to allow analyte diffusion for small-medium ions, while preventing larger quenchers from accessing the sensor dyes. 


Core-shell pH sensitive particles have been demonstrated by our collaborators at Cornell for both intra- and extra-cellular imaging applications such as lysosomal imaging as shown below:

Biological Applications - Quantitative Chemical Sensing

C•spec™ sensor particles can help scientists visualize events and locations in and around cells with traditional fluorescence microscopes. Recent research at Cornell demonstrates the contribution of the C•spec™ platform to a new possibility with fluorescence imaging: highly resolved spatial and temporal quantitation of chemical concentration. In contrast to traditional C•spec™ architectures which incorporate a pure silica shell, the C•spec™ sensor particle incorporates a shell containing environmentally-sensitive fluorescent dyes. The particle core sequesters environmentally-insensitive dyes of a different wavelength. This architecture (shown at the right) provides a quantitative probe for intra- and extra-cellular analytes of interest. C•spec™ sensor particles provide additional benefits beyond those outlined for single color particles: In_Vitro_Imaging.htmlIn_Vitro_Imaging.htmlshapeimage_3_link_0shapeimage_3_link_1

Core-shell C•spec™ sensor particle incorporating a red reference dye in the particle core, and a green chemical sensor dye incorporated in the particle shell. 

70 nm diameter core-shell C•spec™ pH sensors endocytosed by Rat Basophilic Leukemia Mast cells, showing both sensor (green) and reference (red) confocal fluorescence images which were analyzed pixel-wise to generate the pH map of intracellular compartments shown on the right.