1070-4272/01/7403-0519$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 3, 2001, pp. 519!521. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 3,
2001, pp. 507!510.
Original Russian Text Copyright + 2001 by Airapetyan, Balayan, Khachatryan.
Synthesis and Some Characteristics of Magnetic Matrices
for Fixation of Biologically Active Substances
S. S. Airapetyan, G. G. Balayan, and A. G. Khachatryan
Yerevan State University, Yerevan, Armenia
Received August 1, 2000
Abstract-A possibility of production of nonporous magnetic matrices with two-layer coating based on cobalt
ferrite with the aim to use these matrices for fixation of biologically active substances was considered. The
function of the first layer (silica coating) is to shield the cobalt ferrite surface and provide conditions for
applying the second (polymer) layer containing various functional groups.
With advances in modern procedures of recovery
and purification of various chemical compounds, par-
ticularly biologically active substances, the necessity
arises to produce matrices with a set of useful specific
characteristics. In this connection, production of mat-
rices that, among other things, are capable of mag-
netization is an urgent problem. These matrices can be
used for fixation in bioengineering and also for re-
covery and purification of enzymes and other biologi-
cally active substances, when the use of standard
matrices is impossible (e.g., in the case of highly vis-
cous homogenate of biologically active substances). In
addition, carriers based on magnetic matrices can be
recovered from a suspension by applying magnetic
fields instead of centrifuging .
At present, magnetic matrices for affine sorbents
and supports are produced by KLB Co. (Sweden), IBF
(France), etc. They consist of agarose and acrylamide
gels, swelling in solvents, with admixed magnetite
(up to 7 wt %).
However, these matrices do not fully meet the re-
quirements placed upon them; the main requirements
are mechanical strength of the matrix material, chemi-
cal resistance to biologically active substances and
chemical reagents, insolubility in a wide range of
solution pH, the features of wettability and swelling in
the eluent, and the reactivity providing the possibility
of chemical modification .
Instead of the above gels of the organic origin,
a silica gel shell having low nonspecific sorption,
ideal rigidity, and soft hydroxyl cover can be used .
However, it should be borne in mind that in modifica-
tion of these matrices with hydrophobic radicals (ethyl
, octyl C
, and others) only about 40% of silanol
groups at the matrix surface are involved in the modi-
fication. The residual silanol groups can cause un-
desirable silanol reactions deteriorating the quality of
the operations. To avoid this, after modification the
surface of these matrices is additionally treated with a
low-molecular-weight hydrophobic modifier, e.g.,
trimethylchlorosilane. However, in this case, too,
shielding of the residual silanol groups is incomplete.
Another drawback of silica gel matrices is their
operating range of pH restricted to neutral and acidic
solutions (pH 338).
To eliminate the above drawbacks and produce
magnetic matrices most fully meeting the imposed
requirements, it seems appropriate to apply two-layer
coatings on the surface of powdered magnetic materi-
als. As the first layer, silica having active silanol
groups at its surface can be used, owing to which a
great variety of chemical compounds with various
functional groups can be fixed at the silica surface.
The second layer can be formed by macromolecular
compounds chemisorbed at the SiO
shielding all the surface silanol gropus.
The possibility of applying silica coating on vari-
ous supports is described in sufficient detail in ,
where the application conditions and characteristics
of protecting silica coatings on the surface of nickel,
iron, aluminum, and other oxides, and also various
metals and alloys are presented.
Thus, the aim of this work is to study a possibillity
of production of nonporous two-layer magnetic mat-
rices based on cobalt ferrite for fixation of biological-
ly active substances.