Optical Reporting by Conjugated Polymers via Conformational Changes - Advanced Fluorescence Reporters in Chemistry and Biology - page 398

Fig. 7 PDA-OTS viral
detection systems
incorporating OTS monolayer
with polydiacetylene linked
backbone, lipid side chains,
and surface ligand for
receptor binding [ 14 ]

receptor-binding
ligand

HO O HO O HN O HO O HO

O

chromatic
detection
element

monolayer
support

solid support

These glass slides, which appear blue upon fabrication, turned red upon interac-
tion or exposure to the influenza virus. As evident in Fig. 7 , any change in packing,
conformation, or position of the receptor-binding ligand translates into a similar
change in the packing of the polydiacetylene side chains. This, in turn, results in a
change in polymer backbone configuration and therefore both conjugation length
and color. In addition, the resultant color change was directly proportional to the
amount of virus present, allowing for possible quantification of viral load.
First, the above-mentioned sensors have major drawbacks, as the detection and
recognition event is a function of the nature and characteristics of the side chains,
and the side chain functionalization of the CP requires advanced synthesis and
extensive purification of numerous monomeric and polymeric derivatives. Second,
this generation of sensors primarily employed optical absorption as the source for
detection, resulting in lower sensitivity when compared with other sensing systems
for biological processes. However, the use of fluorescence detection within these
sensing systems could justify continued development. More recent examples
include a fluorescent polythiophene derivative with carbohydrate functionalized
side chains for the detection of different bacteria [ 15 ] and novel synthesis schemes
for ligand-functionalization of polythiophenes [ 16 ].