Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 11, pp. 1771−1779.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © T.L. Yurkshtovich, N.V. Golub, N.K. Yurkshtovich, V.A. Alinovskaya, R.I. Kosterova, 2012, published in Zhurnal Prikladnoi Khimii,
2012, Vol. 85, No. 11, pp. 1867−1875.
AND POLYMERIC MATERIALS
Synthesis, Structure, and Physicochemical Properties
of Gel-Forming Dextran Phosphates
T. L. Yurkshtovich, N. V. Golub, N. K. Yurkshtovich, V. A. Alinovskaya, and R. I. Kosterova
Research Institute of Physical Chemical Problems of the Belarusian State, Minsk, Belarus
Received June 26, 2012
Abstract—Dextran phosphates with the degree of substitution of 0.29–1.09 with phosphoric acid groups and
of 0.14–0.83 with carbamate groups were prepared in the orthophosphoric acid–urea system. The effect of the
component ratio in the esterifying mixture, temperature, and pressure in the reaction zone on the structure and
physicochemical properties of dextran phosphate hydrogels and on the gel fraction yield was examined.
Preparation of hydrogels based on synthetic and
natural polymers for use in medicine is a promising and
actively developing direction of macromolecular chem-
istry. Hydrogels are used in formulations for producing
soft contact lenses, drug forms with prolonged release
of the active substance, transdermal therapeutic systems,
sorbents, materials for fabricating endoprostheses, etc.
In the past decades, dextran occupied a particular place
among natural polymers for preparing hydrogels used
in medicine. Dextran is a water-soluble polysaccharide.
It consists of molecules containing D-glucose residues
linked mainly by the α-1,6-D-glucoside bond and, to a
considerably lesser extent, by the α-1,2 and α-1,3 bonds.
Growing interest in synthesis and physicochemical prop-
erties of hydrogels based on physically and chemically
cross-linked dextran and its derivatives (methacrylate,
hydroxyethyl methacrylate, dextran oligolactates, etc.)
is due to the possibility of using them in pharmacology
as carrier polymers for immobilization and controlled
release of drugs, including proteins [1−4].
This paper deals with preparation of gel-forming
dextran phosphates in the system orthophosphoric acid
] and with a study of their
structure and physicochemical properties.
The advantages of using phosphoric acid polysaccha-
ride esters for preparing hydrogels for medicine are that
they are nontoxic, meet the biocompatibility and resolu-
tion criteria, and exhibit cation-exchange and complexing
Numerous papers deal with the synthesis of poly-
saccharide phosphates [5−15]. One of the most widely
used procedures for polysaccharide phosphorylation
with pentavalent phosphorus derivatives is esteriﬁ ca-
tion with orthophosphoric acid in the presence of urea.
Relationships of polysaccharide esteriﬁ cation with or-
thophosphoric acid have been studied mainly for starch
and cellulose [7, 9−12]. Data on esteriﬁ cation of dextran
in the orthophosphoric acid–urea system are lacking.
There are data  on preparation of hydrogels based
on dextran phosphates using another reagent, phosphorus
oxychloride. However, the use in the reaction of an ag-
gressive agent and of a toxic organic solvent (pyridine
or benzene), and also degradation of the polysaccharide
restrict the possibilities of practical use of this procedure
for preparing hydrogels based on dextran phosphates.
As starting materials we used dextran [molecular
000 Da, ND RB (Standard Document of
Belarus Republic) 0221S-2008], orthophosphoric acid
[GOST (State Standard) 6552–80, ρ
= 1.698 g cm
с = 85.4%], and urea (chemically pure grade).