Design and Synthesis of Monofunctionalized, Water-Soluble
Conjugated Polymers for Biosensing and Imaging Applications
- Publication date
- Publisher
Abstract
Water-soluble conjugated polymers with controlled molecular weight
characteristics, absence of ionic groups, high emission quantum yields,
and end groups capable of selective reactions of wide scope are desirable
for improving their performance in various applications and, in particular,
fluorescent biosensor schemes. The synthesis of such a structure is
described herein. 2-Bromo-7-iodofluorene with octakis(ethylene glycol)
monomethyl ether chains at the 9,9′-positions, i.e., compound <b>4</b>, was prepared as the reactive premonomer. A high-yielding
synthesis of the organometallic initiator (dppe)Ni(Ph)Br (dppe = 1,2-bis(diphenylphosphino)ethane)
was designed and implemented, and the resulting product was characterized
by single-crystal X-ray diffraction techniques. Polymerization of <b>4</b> by (dppe)Ni(Ph)Br can be carried out in less than 30 s,
affording excellent control over the average molecular weight and
polydispersity of the product. Quenching of the polymerization with
[2-(trimethylsilyl)ethynyl]magnesium bromide yields silylacetylene-terminated
water-soluble poly(fluorene) with a photoluminescence quantum efficiency
of 80%. Desilylation, followed by copper-catalyzed azide–alkyne
cycloaddition reaction, yields a straightforward route to introduce
a wide range of specific end group functionalities. Biotin was used
as an example. The resulting biotinylated conjugated polymer binds
to streptavidin and acts as a light-harvesting chromophore to optically
amplify the emission of Alexa Fluor-488 chromophores bound onto the
streptavidin. Furthermore, the biotin end group makes it possible
to bind the polymer onto streptavidin-functionalized cross-linked
agarose beads and thereby incorporate a large number of optically
active segments