ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 5, pp. 802!805. + Pleiades Publishing, Inc., 2006.
Original Russian Text + G.U. Ostrovidova, E.V. Zamyslov, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 5, pp. 812!815.
AND POLYMERIC MATERIALS
Sorption of Trypsin on the Polysiloxane Rubber Surface
G. U. Ostrovidova and E. V. Zamyslov
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received February 1, 2006
Abstract-The sorption kinetics of trypsin on medical polysiloxane rubber and polysiloxane rubber modified
with graphite was studied. The effect of the nonuniformity and hydrophilicity of the rubber surface on
the trypsin immobilization rate was analyzed.
In contact of protein-containing biological solu-
tions with foreign solids, the process occurring first
is the sorption of protein. This process is mainly
responsible for biocompatibility of medical materials
. In this study we examined the interaction of
proteolytic enzyme trypsin with the polysiloxane
rubber surface. The positive effect of trypsin on the
hemocompatibility of medical materials was reported
in [2, 3].
The initial polysiloxane rubber of medical purity
(M = 60000) and polysiloxane rubber
modified in the bulk with graphite [20350 wt % rela-
tive to rubber, SKTV
composite material (CM)]
 were used as sorbents. Trypsin (proteolytic en-
zyme) was purchased from Spofa (Czechia). Other
chemicals were of ultrapure, analytically pure, and
chemically pure grade.
The surface trypsin concentration was determined
spectrophotometrically (l = 280 nm) . The pro-
teolytic activity was determined with casein as a sub-
strate. The contact angles were measured with a hori-
zontal microscope. The free surface energy was calcu-
lated by the equation 
I = I
(1 + cosG)
= 72.5 mJ m
is the water surface tension.
The X-ray photoelectron spectra of trypsin immobi-
lized on both the initial and modified polysiloxane
rubber were recorded on a PH1 5400 spectrophotom-
eter (Perkin3Elmer, the United States) using MgK
radiation (1253.6 eV) at a pressure in the spectro-
photometer chamber of 1.3 0 10
Pa. The binding
energy was measured with an accuracy of +0.1 eV.
The trypsin determination error was 10 rel. %. The
spectrophotometer was calibrated relative to the C1s
line of residual hydrocarbons (electron binding energy
285.0 eV) taking into account the sample charging.
The X-ray photoelectron spectra were processed with
the Perkin3Elmer program.
Figure 1 shows the kinetic curves of trypsin sorp-
tion on the initial polysiloxane rubber and composite
material with varied graphite content. It is seen that,
for all the materials tested, the sorption saturation is
attained within 30360 min. At high graphite content
in the modified rubber, its surface becomes mosaic
and acquires a negative charge. Owing to the presence
of graphite, the modified rubber surface contains
specific sorbing groups influencing the trypsin im-
mobilization. The shape of the kinetic curves (Fig. 1)
shows that the sorption of trypsin on the initial rubber
Fig. 1. Kinetic curves of trypsin sorption on polysiloxane
rubber. (m) Trypsin surface concentration and (t) time.
(1) Initial polysiloxane rubber (SKTV
); graphite content
in composite material, wt % relative to rubber: (2) 20 and