Conjugates, Complexes, and Interlocked Systems Based on Squaraines and Cyanines - Advanced Fluorescence Reporters in Chemistry and Biology - page 182

from the anticocaine aptamer was used for selective measurement of cocaine in presence
of other cocaine metabolites (benzoyl ecgonine and ecgonine methyl ester) [ 74 ].

6 Microporous Solid-Phase Encapsulated Dyes

The combination of dyes with microporous materials opens-up a way to develop
selective chemosensors: microporous zeolites with an anchored squaraine 27
(Fig. 13 ) and some other types of dyes can be used as chemosensors for the
chromogenic discrimination of amines [ 75 ]. These dye-zeolite hosts are expected
to be promising sensor materials allowing the visible discrimination of selected
target guests by size and/or polarity within families or closely related molecules. It
was found that the response of the solid to amines was basically governed by the
three-dimensional architecture of the solid material.
Encapsulation of organic dyes in polymeric , silica , calcium phosphate , and other
types of nanoparticles allows to overcome some of the shortcomings of these dyes
such as low fluorescent signal and insufficient chemical and photochemical stability.
The size of nanoparticles varies in general between 2 and 400 nm. These nanopar-
ticles contain a large number of dye molecules, yielding an intense fluorescence
signal that is several thousand times higher than that of conventional dyes. Also, the
matrix of a nanoparticle serves as a protective shell that protects the dye molecules
against environmental impact and increases stability of the encapsulated dyes. Silica
nanoparticles possess some advantages over other types of nanoparticles. They are
easy to separate via centrifugation during particle preparation and processing
because of the higher density of silica. Silica nanoparticles are hydrophilic and
biocompatible, they are not subject to microbial attack, and no swelling or porosity
change occurs with changes in pH. Because of these favorable properties, dye-
doped silica nanoparticles show great potential in various biomedical applications
(More detailed description of the properties of dye-doped nanoparticles can be
found in chapter of Liang et al. [ 100 ]).
To overcome photobleaching and the low signal intensities of cyanine dyes Cy3
and Cy5, these dyes were encapsulated in silica coreshell nanoparticles [ 76 ]. The
obtained dye-doped nanoparticles were applied in the DNA microarray-based

N

OO

O

HO OH

O

N

N

27

NMe 2

Fig. 13 Synthesis of squaraine-zeolite conjugate 27 [ 75 ]