Optical Reporting by Conjugated Polymers via Conformational Changes - Advanced Fluorescence Reporters in Chemistry and Biology - page 399

4 Noncovalent Ligand Sensors

The sensors discussed so far are based on ligands covalently bound to the polymer
backbone. Other methods of detection - often referred to as “mix and detect”
methods - work by simple noncovalent incorporation of the polymer with the
ligand of interest. Reichert et al. generated liposomes of polydiacetylene with sialic
acid for the same purpose of detection as Charych's surface-bound polymers, but
realized that covalent functionalization of the polymer was not necessary [ 17 ].
Through simple mixing of the lipid-bound sialic acid with the polymer before
sonication and liposome formation, they were able to form a functional colorimetric
recognition system (Fig. 8 ).
The surface glycogen was displayed easily enough for binding to the HA
lectin. This interaction sufficiently altered the conformation of the polymer,
resulting in an observable color change [ 17 ]. Using a similar concept and poly-
diacetylene as the signal transducing CP, Charych and Okada went on to develop
additional strategies for the molecular recognition of Escherichia coli entero-
toxin, cholera toxin, botulinium neurotoxin, and an assay for phospholipase A 2
inhibitors [ 7 , 18 ].

O
HO O
O

Aqueous
interior

HO

HN

O

HO
HO

O

Receptor binding ligand

Fig. 8 ( top ) Liposome with polydiacetylene linked monolayer mixed with ligand for receptor
detection. ( bottom ) Colorimetric detection of influenza virus using polymerized liposomes to
which have been added increasing amounts of influenza virus from left to right .[ 18 ]