ISSN 0965545X, Polymer Science, Ser. A, 2010, Vol. 52, No. 9, pp. 907–913. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © E.V. Nam, A.E. Zhirnov, E.A. Litmanovich, N.S. MelikNubarov, I.D. Grozdova, 2010, published in Vysokomolekulyarnye Soedineniya, Ser. A, 2010,
Vol. 52, No. 9, pp. 1578–1584.
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1
INTRODUCTION
Block copolymers of ethylene oxide (EO) and pro
pylene oxide (PO) show amphiphilic characteristics: a
hydrophilic PEO block yields solubility in water,
whereas a hydrophobic PPO block is responsible for
interaction with lipid membranes [1]. As a result, these
polymers can interact with cells and change their
characteristics. For example, cancerous cells, which
are resistant to a broad range of drugs, perish under the
action of an antitumor vaccine when it contains the
added triblock PEO–PPO–PEO–Pluronic L61
copolymer [2]. A similar effect was also observed for
diblock copolymers; at the same time, the action of
these copolymers on model lipid systems appears to be
somewhat different, and this difference is likely related
to their block architecture [3].
The study of polymer and cell interaction usually
involves covalent modification with fluorescent labels.
However, introduction of labels can change the char
acteristics of the modified compound. For example,
addition of 2acetoxybenzoate to PEG changes its
ability to form complexes with PAA [4]. Introduction
of fluororescein isothiocyanate (FITC) even to a bulky
protein with М = 66 × 10
3
changes the overall charge
on the protein as well as its dimensions and isoelectric
point [5]. One can hardly exclude the possibility that
covalent addition of fluorescent labels to EO–PO
block copolymers, which are by an order of magnitude
lower (М ~2000), can also change the characteristics
of polymers. In the literature, no information of this
kind is available.
The objective of this work can be formulated as fol
lows: whether the characteristics of EO–PO block
1
This work was supported by the Russian Foundation for Basic
Research, project no. 090300445.
1
copolymers are changed due to the introduction of
fluorescent labels into their molecules. We studied two
copolymers: triblock pluronic L61 HO–
ЭО
2
ПО
30
ЭО
2
–H (M
w
= 1890, M
w
/M
n
= 1.14) and
diblock pluronic REP (CH
3
)
3
CO–ЭО
24
ПО
19
(M
w
=
2190, M
w
/M
n
= 1.05). Pluronic L61 contains two reac
tive OH groups at the ends of hydrophilic PEO blocks,
and diblock copolymer REP has one free OH group at
the end of the hydrophilic PPO block. Due to the long
length of the PEO block, REP seems more hydrophilic
as compared to pluronic L61.
As fluorescent labels, we used small hydrophobic
4chloro7nitrobenzo2oxa1,3diazole (NBDCl)
with М = 200 and FITC with M = 389, which was used
earlier for modification of pluronics [6]. In contrast to
NBD, FITC contains hydroxyl group and is negatively
charged at neutral pH. These compounds are widely
used in practice because they are characterized by a
high coefficient of molar absorption in the visible
spectral region and by high quantum fluorescence
yield; they also provide a weak background fluores
cence of biological samples [7].
N
O
N
Cl
N
+
O
O
-
N C S
HO
O
O
O
OH
NBDCl FITC (S=C=Nfluororescein)
The Effect of Modification with Fluorescent Groups
on the Physicochemical Characteristics of Poly(alkylene oxides)
1
E. V. Nam, A. E. Zhirnov, E. A. Litmanovich, N. S. MelikNubarov, and I. D. Grozdova
Faculty of Chemistry, Moscow State University, Moscow, 119991 Russia
email: grozdova@genebee.msu.ru
Received November 30, 2009;
Revised Manuscript Received March 15, 2010
Abstract—Covalent modification of poly(alkylene oxides), block copolymers of ethylene oxide and propy
lene oxide with M ~ 2000, with fluororescein isothiocyanate or 7nitrobenzo2oxadiazole taken in a ratio of
0.6–1.0 mol of label/mole of polymer leads to changes in the physical state of polymers and their solubility
in water decreases, as well as the partition coefficient in the hexane–water system and the critical concentra
tion of aggregation and dimensions of the formed particles.
DOI: 10.1134/S0965545X10090051
1
SOLUTIONS