Incorporating α-allyl glucoside into polyacrylonitrile by water-phase precipitation copolymerization to reduce protein adsorption and cell adhesion

Article abstract of DOI:10.1021/ma021393k

α-Allyl glucoside (AG) was incorporated into polyacrylonitrile by water-phase precipitation copolymerization (WPPCP) for the first time with K₂S₂O₈-Na₂SO₃ as initiator system to improve the resistance

Full text of DOI:10.1021/ma021393k

Macromolecules 2003, 36, 2441-2447
2441
Incorporating R-Allyl Glucoside into Polyacrylonitrile by Water-Phase
Precipitation Copolymerization To Reduce Protein Adsorption and Cell
Adhesion
Zh i-Ka n g Xu ,* Ru i-Qia n g Kou , Zh en -Mei Liu , F u -Qia n g Nie, a n d You -Yi Xu
Institute of Polymer Science, Zhejiang University, Hangzhou 310027, P. R. China
Received August 27, 2002
ABSTRACT: R-Allyl glucoside (AG) was incorporated into polyacrylonitrile by water-phase precipitation
copolymerization (WPPCP) for the first time with K2S2O8-Na2SO3 as initiator system to improve the
resistance properties of protein adsorption and cell adhesion for acrylonitrile-based polymer. The effects
of initiator concentration, reaction time and temperature, and total monomer concentration on the
copolymerization were studied, and some results were compared with those of solution copolymerization
using AIBN as initiator. FT-IR, 1H NMR, and 13C NMR spectroscopes, element analysis, and DSC
measurement were used to characterize the copolymers. It was found that both the yield and molecular
weight for the WPPCP were higher than those for solution polymerization. The AG content in the resulting
copolymers and the AG conversion for WPPCP were also higher than those of solution polymerization.
The surface properties of the carbohydrate-containing copolymers were studied by pure water contact
angle, protein adsorption, and cell adhesion measurements. It was found that the contact angle of the
copolymer films decreased from 68° to 30° with the increase of AG content in the copolymer. The adsorption
amount of bovine serum albumin (BSA) and the adhesive number of macrophage on the film surface also
decreased significantly with increasing R-allyl glucoside content from 0 to 42 wt % in the copolymer.
These results revealed that both the hydrophilicity and biocompatibility of polyacrylonitrile-based
membranes could be improved by copolymerization acrylonitrile with vinyl carbohydrates.
In tr od u ction
colloids, microbes, and undissolved hydrocarbons, the
foulents are often adhesive and exhibit irreversible
fouling due to hydrophobic interactions, hydrogen bond-
ing, van der Waals attractions, extracellular macromo-
lecular interactions, and other effects.
Polyacrylonitrile and acrylonitrile-based copolymers
have been successfully applied as membrane materials
in the fields of dialysis, ultrafiltration, enzyme im-
mobilization, and pervaporation.1-11 However, the rela-
tively poor hydrophilicity and biocompatibility for this
type of membrane limit their further applications in
aqueous solution and biomedical usage. Ultrafiltration
membranes are widely used in the biotechnology indus-
try for the recovery of biological products in steps such
as cell broth clarification, cell harvesting, concentration
or diafiltration of protein solution prior to separation,
and final concentration.12 Nevertheless, one major
problem with ultrafiltration is the loss of permeation
flux caused by adsorptive fouling of biological molecules
such as proteins on the surface and even inside the
pores of typically used hydrophobic membranes such as
polyacrylonitrile. Fouling reduces productivity due to
longer filtration times and shortens membrane life due
to the harsh chemicals necessary for cleaning. What is
more, it can also alter membrane selectivity and lead
to significant product loss through denaturation. Gener-
ally, two distinct types of fouling phenomena are
considered:13 (1) macrosolute (such as proteins) adsorp-
tion, which refers to specific intermolecular interactions
between the macrosolute and the membrane that occur
even in the absence of filtration, and (2) filtration-
induced macrosolute or particle deposition, which is over
and above that observed in a static system. Filtration-
induced macrosolute or particle deposition is often
reversible, nonadhesive fouling. A variety of methods
have been reported to reduce this type of fouling for a
range of different applications, as summarized recently
by Ma et al.14 Macrosolute adsorption is generally
irreversible, adhesive fouling. In bioseparation and
water-treatment applications involving proteins, cells,
Increasing the hydrophilicity of the membrane surface
can reduce fouling and improve biocompatibility for the
membranes.11-16 Therefore, there are many surface
modification methods that have been reported to make
ideal hydrophilic and fouling-resistant surfaces. Among
them, the grafting of hydrophilic monomers on the
membrane surface shows some promise.10,12-16 However,
grafting polymerizations induced by radical, plasma,
electron-bean, γ-radiation, and ultraviolet may result
in production of a significant amount of homopolymer
or cross-linked polymer. The undesired homopolymer
wastes expensive starting materials, and cross-linked
polymer is detrimental to membrane filtration since the
membrane pores may become blocked. Moreover, the
grafting density (number of grafting sites per area) and
grafting polymer chain length cannot be determined
independently, much less controlled. Copolymerizing
hydrophilic monomers such as acrylic acid, acrylamides,
vinylpyrrolidone, 2-hydroxyethyl methacrylate, glycidyl
methacrylate, and 4-vinylpyridine with acrylonitrile
have also been used to improve the properties of
acrylonitrile-based polymeric membranes.3,5-8,11 How-
ever, much attention3,5-6,8 was focused on the pervapo-
ration properties and enzyme immobilization for these
copolymer membranes. Only fragmentary data11 were
reported concerning the improvement of fouling reduc-
ing.
The primary objective for our work is the preparation
of novel polyacrylonitrile-based membranes possessing
the properties of fouling reducing, especially the resis-
tance of protein adsorption and cell adhesion. Compared
10.1021/ma021393k CCC: $25.00 © 2003 American Chemical Society
Published on Web 03/15/2003

2442 Xu et al.
Macromolecules, Vol. 36, No. 7, 2003
removed. The acetone solution was concentrated in a vacuum,
seeded, and placed in refrigerator to crystallize. The crude
crystals were recrystallized three times with acetone. The
melting point was measured as 101.5 °C. Anal. Calcd for
C9H16O6: C, 49.09; H, 7.27; O, 43.64%. Found: C, 48.80; H,
with the above-mentioned hydrophilic monomers used
for surface modification and copolymerization, vinyl
carbohydrates may meet these demands. The funda-
mental concept was inspired by the fact that carbohy-
drates exist in many forms and play important roles in
natural living systems. Their highly hydrophilic char-
acteristics together with their innate compatibility with
biomolecules have led to considerable interest in their
polymers synthesis.17-27 Up to date, many artificial
carbohydrate-containing polymers (so-called glycopoly-
mers) have been prepared by means of the vinyl
polymerization17-23 or ring-opening polymerization24,25
of the corresponding monomers, where the carbohydrate
moieties are bound to the polymer chains by ester,
amide, ether, or glycoside bond. Some applications or
potential use of these polymers are hydrogels, surface
modification, biomolecule, or cell recognition.26-31 Al-
though the carbohydrate-containing homopolymers have
the properties of perfectly hydrophilicity and biocom-
patibility, they are also highly polar, water-soluble,
fragile, and biodegradable.32 Furthermore, because of
the incompatibility of hydroxyl groups from the carbo-
hydrate moieties with either initiators or normal organic
solvents for polymerization, the synthesis procedures
are relatively complex because all of these approaches
require the use of protected monomers and the subse-
quent deprotection of polymer chains to generate the
desired glycopolymers. Therefore, they cannot be used
directly as backbone of membranes.
To increase the hydrophilicity and reducing the foul-
ing of polyacrylonitrile-based membranes, it is one of
the most effective methods to copolymerize vinyl car-
bohydrates with acrylonitrile.33 In this paper, the co-
polymerization of acrylonitrile (AN) and R-allyl gluco-
side (AG) was carried out for the first time by water-
phase precipitation copolymerization (WPPCP) method
with K2S2O8-Na2SO3 as initiator system and water as
reaction medium. Because the carbohydrate monomer,
R-allyl glucoside, is highly soluble in water, the synthe-
sis procedure can be simplified by leaving out the
protection and deprotection steps. Pure water contact
angle, bovine serum albumin (BSA) absorption, and the
macrophage adhesion onto the films fabricated from the
AN/AG copolymers were studied to reveal the potential-
ity of the copolymerization acrylonitrile with vinyl
carbohydrates in improving both the hydrophilicity and
biocompatibility of polyacrylonitrile-based membranes.
1
7.42; O, 43.78%. H NMR of AG (500 MHz, DMSO-d6, TMS):
δ ) 3.27-3.31 (t, HOCH , 1Hf), 3.43-3.46 (m, HOCH , 1Hg),
3.58-3.60 (bd, HOCH2-, 2Hi), 3.62-3.66 (m, -CH , 1Hh),
3.73-3.76 (m, HOCH , 1He), 3.97-4.12 (dq, -CH2O-, 2Hc),
4.85-4.86 (d, -OCHO-, 1Hd), 5.14-5.28 (dd, CH2dCH-, 2Ha),
and 5.82-5.90 (m, CH2dCH-, 1Hb).
Cop olym er iza tion of AN a n d AG. Copolymerization of
AN and AG was performed by using varying molar ratios of
the two monomers. For 15/85 AG/AN feed, 100 mL of distilled
and deionized water, 9.50 g of AG, and 11.50 g of AN were
added into a four-necked round flask equipped with mechan-
ical stirrer, thermometer, and nitrogen inlet tube. 45.6 mg of
K2S2O8 and 21.2 mg of Na2SO3 were added into the stirring
solution while maintaining the reaction temperature at 60 °C
under
a nitrogen atmosphere. The copolymerization was
continued for a designated period of time, and the precipitated
copolymer was filtered and washed with excess distilled and
deionized water and ethanol to remove residual monomers.
The obtained copolymer was dried under vacuum at 60 °C to
constant weight. The yield (conversion of monomers) was
calculated by the mass ratio of the copolymer product to the
total monomers in the feed. The oxygen contents of the
copolymers were measured by elemental analysis (EA1110)
and used to calculate the weight fractions of AG in the
copolymers. The conversion of AG was calculated by the mass
ratio of the monomer existing in copolymer to the monomer
in the feed. The solution copolymerizations of AN and AG
initiated by AIBN in DMSO were carried out at 70 °C with
the usual procedure33 for comparison.
Ch a r a cter iza tion . IR spectra were measured on a Bruck
Vector 22 spectrometer. 1H and 13C NMR spectra were
measured on a Bruck (Advance DM×500) nuclear magnetic
resonance spectrometer. The solvent is dimethyl-d6 sulfoxide,
and three drops of D2O were added to the solution. The
composition of the copolymers was determined by element
analysis (EA1110). Differential scanning calorimetry (DSC)
analysis of the copolymers was conducted by a STA409PC
thermal analysis system. The measurements were run under
an Ar atmosphere at 10 °C/min heating rate to 500 °C. The
static contact angle of the copolymer films was determined on
a KRUSS DSA10-MK machine. Viscosity measurements were
made in a thermostatic water bath at 30 ( 0.1 °C using a
Ubbelchde viscometer. Copolymer was dissolved in DMSO that
had been exhaustively dried over molecular sieves. For each
copolymer, the viscosity of five concentrations was measured.
Intrinsic viscosity was obtained by extrapolation of a plot of
specific viscosity/concentration vs concentration to infinite
dilution using linear least squares. Such analysis yield regres-
sion coefficients g0.999. Estimates of the copolymer molecular
weight were obtained from the relationship for PAN in DMSO
at 30 °C:35
Exp er im en ta l Section
Ma ter ia ls. All chemicals were analytical grade. Acryloni-
trile (AN) and dimethyl sulfoxide (DMSO) were commercial
products and were purified by vacuum distillation before used.
Potassium persulfate (K2S2O8), anhydrous sodium sulfite (Na2-
SO3), and azobis(isobutyronitrile) (AIBN) were recrystallized
by usual procedures. Allyl alcohol, anhydrous glucose, and tris-
(hydroxymethyl)aminomethane were used as received without
further purification. Bovine serum albumin (BSA) was pur-
chased from Sino-American Biotechnology Co. and used as
received.
Mon om er Syn th esis. R-Allyl glucoside (AG) was synthe-
sized with the method reported by Talley et al.34 Dry hydrogen
chloride (24.00 g, 0.66 mol) was dissolved in 800 g (13.79 mol)
of dry allyl alcohol and then stirred with 400 g (2.22 mol) of
anhydrous glucose at 70 °C for 41/2 h. After cooling, the mixture
was treated with 92 mL of concentrated ammonium hydroxide
and then with decolorizing carbon. The solution was concen-
trated at reduced pressure to a thick sirup, which was
extracted by stirring vigorously with 2 L portions of dry
acetone at room temperature until no more glucoside was
0.768
[η] ) 2.865 × 10-2Mv
where [η] is the intrinsic viscosity and Mv is the viscosity-
average molecular weight.
P r ep a r a tion of AN/AG Cop olym er F ilm s. AN/AG co-
polymer films were prepared by casting the DMSO solution
of the copolymers (7 wt %) onto glass plates followed by drying
at 60 °C for 24 h and then at 150 °C under vacuum for a week
to completely remove the residual solvent. The copolymer films
thus obtained were removed from the glass plates by immers-
ing in water and followed by drying for another 24 h at 100
°C under vacuum. All films for contact angle, protein adsorp-
tion, and cell adhesion measurements were treated according
to the same procedure. The thickness of the dried film was
approximately 100 ( 5 µm.
Ad sor p tion of BSA. Bovine serum albumin (BSA) adsorp-
tion was carried out by the following method. BSA was

Macromolecules, Vol. 36, No. 7, 2003
Incoporating AG into Polyacrylonitrile 2443
dissolved in a Tris-HCl buffer (pH ) 8) that can facilitate the
hydrophobic interaction and inversely depress the electrostatic
binding between the protein and the polymer surface. To
perform equilibrium experiments, copolymer film with 44 cm2
external surface area was introduced into a tube containing 5
mL of Tris-HCl buffer at 30 °C, before being exposed to the
protein solution. Any air bubbles that would adhere to the
sample were removed by allowing the samples to cross the air/
buffer interface several times. 10 mL of BSA solution was then
introduced into the tube. After the protein solution remained
in contact with the sample for 24 h at 30 °C, the film was taken
out from the protein solution and was further rinsed gently
until the surface remained constant. The amount of adsorbed
protein was determined by measuring spectrophotometrically
the difference between the concentration of albumin in the
solution before and after contact with the polymer film. The
spectroscopic analytical method utilized in this work for
protein dosage was based on the reaction of albumin with
Coomassie brilliant blue (Fluka) dyestuff to record the absor-
bance of the albumin-Coomassie brilliant blue complex ac-
cording to Bradford’s method.36 The reported data were the
mean value of triplicate samples for each copolymer.
Ma cr op h a ge Ad h esion . The murine macrophage suspen-
sion was prepared with the method reported by Li et al.37 The
suspension was isolated from freshly killed mice using chlo-
roform. The skin was sprayed with alcohol and the abdomen
opened. 10 mL of Roswell Park Memorial Institute (RPMI)
1640 containing 10% foetal bovine serum (FBS), 100 g/mL
penicillin, and 100 µm/mL streptomycin was injected into the
peritoneal cavity, and then abdomen was gently massaged by
fingers for 5 min. The peritoneum was carefully punctured,
and then the washings were removed by a sterile pipet and
placed in a sterile container to be centrifuged at 1000 rpm for
10 min to collect the macrophages. The macrophages obtained
were grown in RPMI 1640 to obtain the macrophage suspen-
sion in which the cell concentration was 1 × 106 cells/mL.
The copolymer films (10 × 10 mm2) used were cleaned
sequentially in an ultrasonic bath of ethyl alcohol solution for
10 min and then rinsed in phosphate buffered saline (PBS).
Then the films were immersed in physiological saline (PH 7.4)
to recondition for several hours. The cell suspension was
inoculated on the surface of the films to assess the cell
attachment. The incubation period was 48 h for the cell
attachment test in a humidified atmosphere of 5% CO2 in air
at 37 °C. Then the supernatant was removed, and the films
were washed cautiously five times using PBS (pH 7.2) prior
to fixation. The adherent cell density on the films was
quantified on the basis of measurements obtained visually
from at least five randomly selected fields (0.75 × 1.00 mm2)
using an Olympus TE300 phase contrast optical microscope.
The mean values of triplicate samples for each polymer with
the standard deviation were reported.
Resu lts a n d Discu ssion
Cop olym er iza tion Beh a vior s of AN/AG. The ef-
fects of initiator concentration, reaction time and tem-
perature, and total monomer concentration on the
copolymerization in water were studied using an 85/15
AN/AG monomer feed ratio. The results are presented
in parts a, b, c, and d of Figure 1, respectively. It can
be seen that the copolymerization of AN and AG
behaved in a typical free radical chain polymerization
fashion. At a constant 20 wt % total monomer concen-
tration, the yield (overall monomer conversion) in-
creased rapidly with the initiator concentration and
reaction time as well as reaction temperature at first
and then became almost stable (Figure 1a-c). Increas-
ing the total monomer concentration raised the yield
remarkably at 60 °C and a constant initiator/monomer
ratio (1/500). On the other hand, the molecular weight
of the resultant copolymer decreased with the initiator
concentration and reaction temperature while it in-
F igu r e 1. Typical results for the water-phase precipitation
copolymerization of acrylonitrile/R-allyl glucoside. (a) Effects
of initiator concentration ([AN]/[AG] mole ratio ) 85/15, total
monomer concentration ) 0.20 g/mL, 60 °C, 6 h); (b) effects of
reaction time ([I]/[M] ) 1/500, [AN]/[AG] ) 85/15, total
monomer concentration ) 0.20 g/mL, 60 °C); (c) effects of
reaction temperature ([I]/[M] ) 1/500, [AN]/[AG] ) 85/15, total
monomer concentration ) 0.20 g/mL, 6 h); (d) effects of total
monomer concentration ([I]/[M] ) 1/500, [AN]/[AG] ) 85/15,
60 °C, 6 h).

2444 Xu et al.
Macromolecules, Vol. 36, No. 7, 2003
F igu r e 3. Effects of AG mole fraction in monomer feed on
AG content in the copolymer and AG conversion for both water-
phase precipitation and solution copolymerization.
F igu r e 2. Effects of AG mole fraction in monomer feed ([I]/
[M] ) 1/500, 60 °C, 6 h) on the yield and molecular weight of
the copolymer synthesized by water-phase precipitation and
solution copolymerization.
C bond of AG is linked with an alkoxy bond that has a
negative effect on the radical polymerization, which
leads to a low reactivity of AG. The low reaction ability
of AG also led to the decrease of the Mv of the copolymer
with increasing the AG content in feed.
creased slightly with reaction time and total monomer
concentration. From these results, the optimal condition
for AN/AG (85/15) copolymerization in water was ob-
tained as follows: total monomer concentration, 20
g/100 mL water; initiator/monomer ratio, 1/500; reaction
temperature, 60 °C; reaction time, 6 h.
As shown in Figure 3, increasing the mole fraction of
AG in monomer feed mainly increased the AG content
in the copolymers for both WPPCP and solution polym-
erization. Taking advantages of the WPPCP method,
both the AG content in the copolymers and the AG
conversion for WPPCP were higher than those of
solution copolymerization in DMSO. This might be
reasonable since AG was highly soluble and AN was
slightly soluble in water. As mentioned above, for the
WPPCP method, the initiator presented in water,
therefore, the highly soluble AG had more chance to be
initiated and polymerized than in the solution copolym-
erization method; in turn, the AG conversion and
content were higher than those of solution copolymer-
ization.
The influences of monomer feed ratio on the copoly-
mer yield and molecular weight are shown in Figure 2.
The results of solution copolymerization conducted in
DMSO using AIBN as initiator are also included for
comparison. It was found that both the yield and
molecular weight for the WPPCP were higher than
those for solution copolymerization. The Mv value for
the copolymers initiated by AIBN was all in the 104
g/mol range, while it increased to 105 when WPPCP
method was used, as is shown in Figure 2. Water-phase
precipitation polymerization is a unique process that
affords the advantage of increasing the molecular
weight of the AN-based polymers,38 which, in turn,
benefits the mechanical strength of corresponding mem-
branes.39 When the slightly water-soluble monomer AN
was added to the medium, a small fraction of AN
dissolved in the continuous aqueous phase where initia-
tor was present. Then, the polymerization was first
taken place in water. After the chains in water grew
big enough, they would precipitate from the water
medium. At this time the polymerizations were trans-
ferred from homogeneous polymerization to heteroge-
neous polymerization, which means that the polymer-
izations were taken place both in water and at the
surface of the microparticles precipitated from the
water. In this condition, the chances of the chain
termination and chain transfer became difficult; there-
fore, the molecular weight and the yield of the polymer
increased.
Ch a r a cter iza tion of th e Cop olym er s. The copoly-
mers of AN with AG were characterized by IR and NMR
spectra. The IR spectra of polyacrylonitrile and the
copolymers are shown in Figure 4. Compared with the
spectrum of polyacrylonitrile, several new absorption
bands appeared near 3400 and 1040 cm-1 for the
copolymers. These bands were due to the hydroxyl
(-OH) and the alkoxy bond (-O-CH2-) in the carbo-
hydrate moieties, respectively.
1
Figure 5 and Figure 6 are the H NMR and 13C NMR
spectra of the AG monomer and a typical AN-AG
copolymer. From these figures it can be seen that the
1H NMR and the 13C NMR all gave the information on
both AN and AG monomer unit in the polymer chain,
which confirmed that the sample was an AN-AG
copolymer. Compared with the spectrum of the R-allyl
glucoside monomer (Figure 5a, 1H NMR: δ ) 3.27-3.31
(t, HOCH , 1Hf), 3.43-3.46 (m, HOCH , 1Hg), 3.58-3.60
(bd, HOCH2-, 2Hi), 3.62-3.66 (m, -CH , 1Hh), 3.73-
3.76 (m, HOCH , 1He), 3.97-4.12 (dq, -CH2O-, 2Hc),
From Figure 2, it can be also seen that the yield of
the copolymer decreased obviously with increasing the
AG feed concentration. It might be due to that the Cd

Macromolecules, Vol. 36, No. 7, 2003
Incoporating AG into Polyacrylonitrile 2445
F igu r e 6. Typical 13C NMR spectrum of acrylonitrile/R-allyl
glucoside copolymer.
F igu r e 4. IR spectra of polyacrylonitrile and acrylonitrile/
R-allyl glucoside copolymers.
F igu r e 7. DSC curves of acrylonitrile/R-allyl glucoside co-
polymers.
tion of the copolymers can be calculated according to
the following equation:
AG (wt %) ) 220I4.70/(220I4.70 + 53I3.12-3.15) × 100
where I is the intensity of the peaks in the NMR
spectrum. The AG weight content value for the 85/15
monomers feed copolymer calculated by the 1H NMR
spectrum was 14.8 wt %, which was relatively consistent
with the value 17.4 wt % calculated by element analysis
method. The 13C NMR spectrum of the copolymer
(Figure 6) gave more information about the carbohy-
1
drate moieties than the H NMR spectrum. The desig-
nations (δ ) 60.72 (-CiH2O-), 68.00-69.50 (HOCgH2-),
70.04 (HOCcH ), 71.69 (HOCeH ), 72.87 (HOChH ), 73.15
(HOCfH ), and 98.92 (-OCdHO-)) revealed the exist-
ence of carbohydrate-carrying monomer in the copoly-
mer, while the -CH2-CH- (a and b carbons) of this
monomer on the polymer chain seems overlap with
those of acrylonitrile at 26.72-33.52 ppm.
F igu r e 5. 1H NMR spectra: (a, top) AG monomer; (b, bottom)
acrylonitrile/R-allyl glucoside copolymer.
DSC thermal diagrams of the AN homopolymer as
well as the AN/AG copolymers are shown in Figure 7.
Polyacrylonitrile showed a sharp exothermic peak at
269.7 °C, which was due to the cyclization reaction of
nitrile groups. No obvious changes were observed for
the copolymers. This could be ascribed to the relatively
low AG content and the monodistribution of AG in the
polymer chains.
Su r fa ce P r op er ties of th e Cop olym er F ilm s.
Figure 8 shows the contact angle curve of pure water
on the films fabricated from the acrylonitrile/R-allyl
glucoside copolymers. It was found that the contact
angle decreased gradually from 68.5° to 29.7° with
4.85-4.86 (d, -OCHO-, 1Hd), 5.14-5.28 (dd, CH2d
CH-, 2Ha), and 5.82-5.90 (m, CH2dCH-, 1Hb)), it is
obvious that the peaks of the vinyl group in monomer
disappeared, and fine structures could not be observed
for the corresponding copolymer. Other protons in the
main chain gave broad peaks from 1.97 to 2.17 ppm.
However, from this spectrum it was seen that the peaks
at 3.12-3.15 and 4.70 ppm could provide the quantita-
tive information about the AG content in the copolymers
because the proton of CH-CN showed broad peaks in
the range 3.12-3.15 ppm while the d proton in the AG
unit gave a single peak around 4.70 ppm. The composi-

2446 Xu et al.
Macromolecules, Vol. 36, No. 7, 2003
F igu r e 8. Relationship between the contact angle and AG
content of the acrylonitrile/R-allyl glucoside copolymer films
at 25 °C.
F igu r e 10. Relative macrophage number vs R-allyl glucoside
content in the copolymer films at 25 °C.
hered onto the materials surface indicates that the
better of blood compatibility for the material, which is
to say that the immunological reaction or immunological
rejection will decrease after the materials are planted
into the living body. The results of macrophages adhe-
sion on the acrylonitrile/R-allyl glucoside copolymer
surface are shown in Figure 10. It was clearly demon-
strated that the number of macrophages adhered on the
acrylonitrile/R-allyl glucoside copolymer was signifi-
cantly decreased when compared with that on the
polyacrylonitrile film, which means that the incorporat-
ing of R-allyl glucoside into polyacrylonitrile induced the
reduction of macrophage adhesion. However, it seems
that the macrophage adhesion number increased again
when the AG content in the copolymer was exceeded
around 20 wt %. This might be due to the cluster effect
of the carbohydrate moieties in the copolymer chains.
It was reported that the carbohydrate density strongly
affects the specific interaction between carbohydrate
moieties and cells, and the phenomenon that the binding
affinity is drastically enhanced by multivalent carbo-
hydrate ligands is called the cluster effect.26
F igu r e 9. Adsorption of BSA onto the acrylonitrile/R-allyl
glucoside copolymer films at 25 °C.
increasing the AG content in the copolymers from 0 to
42 wt %. This was due to the contribution of the
hydroxyl groups in AG moieties.27 The decreasing of the
contact angle indicated that a kind of highly hydrophilic
copolymer was obtained.
Con clu sion s
It is well-known that the hydrophobic interaction
between material surfaces and proteins plays a very
important role for nonselective adsorption of protein
onto biomaterials. Usually, materials possessing hydro-
philic surface show relatively low nonselective adsorp-
tion for proteins or cells. Carbohydrate-containing poly-
mers are highly hydrophilic materials; however, some
of them have the recognition function to the biomol-
ecules or cells because of the cluster effect.26,27 There-
fore, the hydrophilicity and the recognition function of
the carbohydrate moieties will have a different effect
on the biomolecules or cells adsorption. Figure 9 il-
lustrates the results of BSA adsorption on the AN/AG
copolymer surface. It can be seen that the adsorbed
amount BSA decreased almost linearly with the in-
crease of AG content in the copolymer, and the high BSA
concentration could lead to the larger amount of BSA
adsorbed onto the copolymer films. The decrease of the
BSA adsorption could be mainly ascribed to the im-
provement of the hydrophilicity by the carbohydrate
moieties for the copolymer surface.
Carbohydrate containing acrylonitrile-based copoly-
mers could be simply synthesized by water-phase pre-
cipitation copolymerization of R-allyl glucoside with
acrylonitrile. The contact angle of pure water, the
amount of BSA absorption, and macrophages adhesion
on the copolymer surface could be decreased to a certain
level by increasing the carbohydrate monomer content
in the copolymers. These preliminary results revealed
that both the hydrophilicity and biocompatibility of
polyacrylonitrile-based membranes could be improved
by copolymerization acrylonitrile with vinyl carbohy-
drates. Further work concerning the membrane fabrica-
tion, characterization (especially fouling resistance), and
applications from the resulted copolymers has been
carrying out in our lab.
Ack n ow led gm en t. The authors are grateful to the
National Natural Science Foundation of China for
financial support (Grant 50273032).
Macrophage is a kind of immune cell and performs
various functions such as migration, phagocytosis,
secretion, antigen presentation, and survival through
precisely modulated adhesion, in living bodies. However,
the molecular mechanism in macrophage adhesion is
complex, dynamic, and not yet fully understood. Gener-
ally speaking, the fewer amount of macrophages ad-
Refer en ces a n d Notes
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