Non-thrombogenic coating composition and methods for using same

The present invention provides an anti-thrombogenic coating composition for blood-contacting surfaces. The coating comprises a covalent complex of from 1 to 30 hydrophobic silyl moieties of Formula I: ##STR1## wherein R.sub.1 is a C.sub.1-8 alkyl or C.sub.6-32 aryl group, each R.sub.2 is independently selected from the group consisting of C.sub.1-8 alkyl and C.sub.6-32 aryl, R.sub.3 is N or O, and n is a number from 1 to 10, directly bound to a heparin molecule via covalent bonding.

BACKGROUND OF THE INVENTION 
The use of disposable medical devices derived from synthetic and natural 
polymers has grown in recent years. These devices include monitoring 
tubes, artificial organs, catheters, blood filters, oxygenators, tubing 
sets and other devices that come into direct contact with blood during 
surgical or other medical treatment procedures. Recently, certain 
synthetic plastics have come into common use due to their desirable 
properties. These plastic materials have increased the ease of device 
manufacturing and are frequently the preferred materials for certain 
applications in prosthetic device technology. 
One common property shared by all medical grade plastics is the possibility 
of the formation of thrombus on the surface when the plastic comes into 
direct contact with blood. The formation of thrombus or a clot creates the 
possibility of a number of serious complications. These include blood flow 
stoppage, pulmonary embolism, cerebral thrombosis or myocardial 
infarction. Traditionally, clinicians decrease the risk of thrombus by the 
administration of anticoagulants such as heparin, coumadin or other 
pharmacological agents. However, administration of these anticoagulants 
can be undesirable in some instances, because the anticoagulants may give 
rise to bleeding complications and because their anticoagulant effects are 
not easily reversed should bleeding complications such as gastrointestinal 
bleeding, occur. 
Heparin is one well known systemic anticoagulant. This sulfated amino 
glycan polysaccharide of variable molecular weight is known to increase 
the inactivation rate of serum proteases such as thrombin and Factor Xa in 
conjunction with the inhibitor antithrombin III. Consequently, in the 
presence of heparin, the blood is less likely to form a thrombus and 
thereby avoid serious life threatening sequela. A review of the clinical 
biochemistry of heparin and its anticoagulation effects can be found in 
HEIN: CHEMICAL AND BIOLOGICAL PROPERTIES, CLINICAL APPLICATIONS (1989) 
edited by D. Lane et al., CRC Press, Inc., Boca Raton, Fla. 
Due to the side effects resulting from direct systemic administration of 
sodium heparin, some researchers have sought to develop means for coating 
heparin onto those surfaces of medical devices that are intended to come 
into direct contact with blood. One example of a heparin coating is 
proposed in V. Gott, Science 142:1297 (1993). Gott proposes a coating for 
a graphite plastic surface which involves the cationic surfactant, 
benzalkonium chloride, complexed to the polyanion heparin. This ionic 
complex of cationic surfactant and heparin adheres to the surface of the 
plastic by virtue of the hydrophobic nature of the surfactant molecule and 
its attraction for the graphite surface. 
Other approaches for coating heparin on a surface were proposed in U.S. 
Pat. Nos. 3,810,781 and 4,118,485 which relate to the treatment of 
heparin-coated surfaces with dialdehyde in order to crosslink the heparin 
molecules. U.S. Pat. No. 4,265,927 proposes treating a charged surface 
with heparin by contacting the surface with a colloidal aqueous solution 
of a complex compound of heparin and a cationic surfactant. The use of the 
dialdehyde purportedly affords a more stabilized heparin coating. However, 
the crosslinking that occurs in the heparin results in a decrease in the 
anti-thrombogenic activity of the heparin. The decrease in 
anti-thrombogenic activity observed by crosslinked heparin coatings is a 
common result of attempts to chemically modify heparin. 
A number of heparin coatings based upon the formation of an ionic complex 
with sodium heparin or a heparin derivative are commercially available. 
Examples of such coatings include BENZALKONIUM HEIN.RTM. from 
Polyscience, Inc, TDMAC.RTM. heparin from Polyscience, Inc., and DUROFLOW 
II.RTM. from Baxter Biocompatible Technologies. These coatings are subject 
to leaching of the heparin due to the ionic nature of blood plasma. More 
specifically, heparin is lost from the surface as the cationic surfactant 
exchanges for other counterions present in the blood, such as sodium, 
potassium, and others. 
Other heparin coatings have been developed which utilize alkylammonium 
salts as the cationic portion of the complex. For example, U.S. Pat. No. 
4,046,725 proposes a polyurethane copolymer for use in the production of 
articles which contact the blood. The copolymer contains quaternary 
ammonium groups to which the heparin coating binds. U.S. Pat. No. 
5,391,580 proposes a poly(sulfone-alpha-olefin) composite article for use 
in blood oxygenation. The article includes a polypropylene tube, and a 
polysulfone perm-selective homogeneous layer directly adhered to the 
polypropylene tube. Heparin is covalently linked to the polysulfone 
perm-selective layer. 
There remains a need in the art for heparin coating compositions which can 
be applied to blood-contacting surfaces of medical devices. There further 
remains a need in the art for heparin coating compositions which do not 
lose their anti-thrombogenic effects over time. There remains a need in 
the art for heparin coating compositions which can be produced in a 
cost-effective and commercially feasible manner and which can be applied 
to blood-contacting surfaces of medical devices in a commercially feasible 
manner. 
SUMMARY OF THE INVENTION 
The present invention relates to new anti-thrombogenic coating 
compositions. According to the compositions of the present invention, 
hydrophobic moieties are covalently bound to a heparin molecule to form a 
covalent complex. 
As a first aspect, the present invention provides an anti-thrombogenic 
coating composition for blood-contacting surfaces. The coating comprises a 
covalent complex of from 1 to 30 hydrophobic silyl moieties of Formula I: 
##STR2## 
wherein R.sub.1 is an C.sub.1-8 alkyl or C.sub.6-32 aryl group, each 
R.sub.2 is independently selected from the group consisting of C.sub.1-8 
alkyl and C.sub.6-32 aryl, R.sub.3 is N or O, and n is a number from 1 to 
10, directly bound to a heparin molecule via covalent bonding. 
As a second aspect, the present invention provides a non-thrombogenic 
medical device comprising surfaces for contacting blood. The 
blood-contacting surfaces have coated thereon an anti-thrombogenic coating 
composition. The anti-thrombogenic coating composition comprises a 
covalent complex of from 1 to 30 hydrophobic silyl moieties of Formula I 
directly bound to a heparin molecule via covalent bonding. 
As a third aspect, the present invention provides a method for rendering 
blood-contacting surfaces of a medical device non-thrombogenic. The method 
comprises coating the surfaces with an anti-thrombogenic coating 
composition. The composition comprises a covalent complex of from 1 to 30 
hydrophobic silyl moieties of Formula I directly bound to a heparin 
molecule via covalent bonding. 
As a fourth aspect, the present invention provides a covalent complex of 
Formula II: 
##STR3## 
wherein R.sub.1 is an C.sub.1-8 alkyl or C.sub.6-32 aryl group, each 
R.sub.2 is independently selected from the group consisting of C.sub.1-8 
alkyl and C.sub.6-32 aryl, R.sub.3 is N or O, n is a number from 1 to 10, 
and x is a number from 1 to 30. 
These and other aspects of the present invention are described further in 
the description of the preferred embodiment and examples of the invention 
which follow. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Unless otherwise defined, all technical and scientific terms employed 
herein have their conventional meaning in the art. As used herein, the 
following terms have the means ascribed to them. 
"Alkyl" refers to linear branched or cyclic, saturated or unsaturated 
C.sub.1-8 hydrocarbons such as methyl, ethyl, ethenyl, propyl, propenyl, 
iso-propyl, butyl, iso-butyl, t-butyl, pentyl, cyclopentyl, hexyl, 
cyclohexyl, octyl, and the like. 
"Aryl" refers to unsaturated C.sub.6-32 hydrocarbon rings which may be 
substituted from 1-5 times with alkyl, halo, or other aryl groups. Aryl 
also includes bicyclic aryl groups. Specific examples of aryl groups 
include but are not limited to phenyl, benzyl, dimethyl phenyl, tolyl, 
methyl benzyl, dimethyl benzyl, trimethyl phenyl, ethyl phenyl, ethyl 
benzyl, and the like. 
The heparin coating compositions of the present invention comprise a 
covalent complex of one or more hydrophobic silyl moieties with heparin. 
Heparin is a mixture of variably sulfated polysaccharide chains composed 
of repeating units of D-glucosamine and either L-iduronic or D-glucuronic 
acids. 
Any suitable form of heparin may be employed in the reaction. Several salts 
of heparin and heparin derivatives are known in the art. For example, 
conventional salts of heparin include sodium heparin, calcium heparin, 
magnesium heparin, and potassium heparin. Heparin derivatives include, but 
are not limited to ammonium heparin, benzalkonium heparin, and the like. 
Sodium heparin is one preferred form of heparin for preparing the covalent 
complexes according to the present invention. For the sake of simplicity, 
the term "heparin molecule" refers to any of known forms of heparin 
including all salts and derivatives of heparin. 
The silyl moiety is represented by the general Formula I: 
##STR4## 
wherein R.sub.1 is an C.sub.1-8 alkyl or C.sub.6-32 aryl group, each 
R.sub.2 is independently selected from the group consisting of C.sub.1-8 
alkyl and C.sub.6-32 aryl, R.sub.3 is N or O, and n is a number from 1 to 
10. As will be apparent to those skilled in the art, R.sub.3 is an N or O 
atom on the heparin molecule, and the unoccupied bond from R.sub.3 
signifies the attachment of the silyl moiety to the heparin molecule. 
Thus, the hydrophobic silyl moiety is capable of attachment to the heparin 
molecule at either an O atom of an alcohol (i.e., hydroxyl) or a N atom of 
an amine. 
Heparin comprises many repeating units containing amine and hydroxyl 
functional groups which can be the site for attachment of the hydrophobic 
silyl moiety to the heparin molecule. Accordingly, one embodiment of the 
present invention contemplates the attachment of more than 1 hydrophobic 
silyl moiety to a single heparin molecule. As many as 30 hydrophobic silyl 
moieties of Formula I or more, and as few as 1 hydrophobic silyl moiety 
may be attached to a single heparin molecule to achieve the covalent 
complex employed in the heparin coating compositions of the present 
invention. In one embodiment of the present invention, between 2 and 25 
hydrophobic silyl moieties are attached to a single heparin molecule. In 
one embodiment, between 5 and 20 hydrophobic silyl moieties are attached 
to a single heparin molecule. In one embodiment, between 7 and 15 
hydrophobic silyl moieties are attached to a single heparin molecule. In 
one preferred embodiment, 7 or 8 hydrophobic silyl moieties are attached 
to a single heparin molecule. In another preferred embodiment 12 
hydrophobic silyl moieties are attached to a single heparin molecule. 
In those embodiments wherein more than one hydrophobic silyl moiety is 
attached to a single heparin molecule, the hydrophobic silyl moieties may 
be attached either through the amine of heparin (e.g., where R.sub.3 is N) 
or through the hydroxyl group of heparin (e.g., wherein R.sub.3 is O). In 
other words, some of they hydrophobic silyl moieties may be attached to 
the heparin molecule via bonding at the amine groups of heparin, while 
other hydrophobic silyl moieties are attached to the heparin molecule via 
bonding at the hydroxyl groups of heparin. It is also possible for all of 
the hydrophobic silyl moieties to be consistently attached to heparin via 
one or the other of the amine (e.g., R.sub.3 in all hydrophobic silyl 
moieties is N) or the alcohol (e.g., R.sub.3 in all hydrophobic silyl 
moieties is O). 
The bonds between the hydrophobic silyl moieties and the heparin molecule 
which effect the attachment of the moieties to the molecule are covalent 
bonds. Thus, the coating compositions of the present invention do not rely 
upon ionic interactions between heparin and the hydrophobic moiety. 
Rather, the hydrophobic moieties are bonded to the heparin molecule by 
covalent bonding through either the amine or hydroxyl groups (or possibly 
a combination of both amine and hydroxyl groups when two or more 
hydrophobic silyl moieties are attached a single heparin molecule). 
Because the hydrophobic silyl moiety is bound to the heparin molecule 
through covalent bonding, the present invention overcomes one weakness of 
conventionally known heparin coatings. Specifically, the problem of 
heparin leaching from the coating as a result of the breaking of the ionic 
bond between heparin and the group which attaches heparin to the surface 
is overcome by avoiding reliance upon ionic bonding interactions between 
heparin and the binding group. In the present invention, the covalent 
bonds between the hydrophobic silyl moieties and the heparin molecule in 
the coating composition are not disrupted by the presence of ionic species 
in the blood with which the coated surface will come into contact. The 
data demonstrate that this process of covalent modification also does not 
lead to detrimental loss of heparin activity as monitored by a Factor 
Xa/Antithrombin III chromogenic substrate assay on the surface of target 
substrates. 
The covalent complex according to the present invention can be prepared 
according to the following Scheme 1. 
##STR5## 
wherein R.sub.1 is an C.sub.1-8 alkyl or C.sub.6-32 aryl group, each 
R.sub.2 is independently selected from the group consisting of C.sub.1-8 
alkyl and C.sub.6-32 aryl, R.sub.3 is N or O, n is a number from 1 to 10, 
and x is a number from 1 to 30. 
Generally, the first intermediate, R.sub.1 (Si(R.sub.2).sub.2 
CH.sub.2).sub.n Cl wherein n is 1, is produced by reacting an alkyl or 
aryl magnesium chloride with a chloro(chloromethyl)-dialkyl silane or 
chloro(chloromethyl)diaryl silane in the presence of tetrahydrofuran 
(THF). The alkyl or aryl magnesium chlorides used as starting materials 
are commercially available, and include, for example benzyl magnesium 
chloride. The chloro(chloromethyl)dialkyl silane or 
chloro(chloromethyl)diaryl silanes are also commercially available and 
include, for example chloro(chloromethyl)dimethyl silane. The reaction is 
exothermic, and is typically conducted at temperatures of about 10.degree. 
C. or less. The reaction is carried out for a sufficient period of time to 
yield about 80-90% product. Typically the reaction is conducted over a 
period of from about 2 to about 24 hours. 
First intermediates wherein n is 2 or higher can be produced using a 
Grignard Reaction involving the reaction of the first intermediate wherein 
n is 1 with ClSi(R.sub.2).sub.2 CH.sub.2 Cl. This Grignard reaction can be 
repeated any number of times to achieve the desired value for n in the 
first intermediate. The reaction is carried out in the presence of a 
catalytic amount of iodine and THF. 
The first intermediate (wherein n is 1-10) is converted to the second 
intermediate, R.sub.1 (Si(R.sub.2).sub.2 CH.sub.2).sub.n OH, by reacting 
the first intermediate with potassium acetate (KOAc) in dimethyl formamide 
(DMF), at a temperature of above about 120.degree. C., and preferably 
about 135.degree. C. for between 12 and 24 hours. The product of this 
reaction is then reacted with sodium methoxide (NaOMe) in methanol (MeOH) 
under reflux for about 2 hours to achieve the second intermediate. 
The second intermediate is converted to the last intermediate, R.sub.1 
(Si(R.sub.2).sub.2 CH.sub.2).sub.n CO.sub.2 N(COCH.sub.2).sub.2, by a 
two-step reaction process. In the first step, the second intermediate is 
reacted with triphosgene and sodium carbonate in methylene chloride at a 
temperature of less than 10.degree. C., and preferably about 0.degree. C. 
The product of this reaction is reacted with N-hydroxysuccinimide and 
triethylamine (Et.sub.3 N) in methylene chloride at a temperature of less 
than 10.degree. C., and preferably about 0.degree. C. 
The final intermediate is covalently conjugated to heparin by reacting 
heparin with the final intermediate in a suitable solvent (e.g., 
water/dimethyl formamide) at a pH of about 8.0 to 9.0, and preferably 
about 8.5. The pH of the reaction is controlled by the addition of base 
such as sodium hydroxide, as needed. 
Using these general methods, the covalent complexes of the present 
invention can be produced. The covalent complexes have the general Formula 
II: 
##STR6## 
wherein R.sub.1 is an C.sub.1-8 alkyl or C.sub.6-32 aryl group, each 
R.sub.2 is independently selected from the group consisting of C.sub.1-8 
alkyl and C.sub.6-32 aryl, R.sub.3 is N or O, n is a number from 1 to 10, 
and x is a number from 1 to 30. 
Preferred complexes include those complexes wherein R.sub.1 of the 
hydrophobic silyl moiety is aryl. In one preferred embodiment, R.sub.1 is 
benzyl. In one preferred embodiment, each R.sub.2 is alkyl. In one 
particularly preferred embodiment, each R.sub.2 is selected from the group 
consisting of methyl, ethyl, propyl, and isopropyl, particularly methyl. 
In one preferred embodiment, n is a number from 2 to 3. 
Specific examples of covalent complexes according to the present invention 
include but are not limited to 
benzyl-bis(dimethylsilylmethyl)!-(N-heparinyl)-carbamate, 
benzyl-tris(dimethylsilylmethyl)!-(N-heparinyl)-carbamate, and 
dodecylbenzyl-bis(dimethylsilylmethyl)!-(N-heparinyl)-carbamate. Although 
these three specific covalent complexes are examples of currently 
preferred covalent complexes having the general Formula II above, other 
specific examples of such complexes will be apparent to those skilled in 
the art and are contemplated by the instant invention. 
The coatings of the present invention comprise the covalent complexes 
described above. In addition to the covalent complex, the coating 
composition may also include one or more solvents which facilitate the 
processes of applying the composition to the surface. Suitable solvents 
will be those which at least partially solubilize the covalent complex and 
which do not interfere with the anti-thrombogenic activity of heparin. 
Examples of solvents which may be employed in the coating compositions of 
the present invention include but are not limited to aqueous solvents, 
alcohols, nitriles, amides, esters, ketones, ethers, and the like. 
"Aqueous" with reference to solutions or solvents refers to solutions or 
solvents which consist primarily of water, normally greater than 90 weight 
percent water, and can be essentially pure water in certain circumstances. 
For example, an aqueous solution or solvent can be distilled water, tap 
water, or the like. However, an aqueous solution or solvent can include 
water having substances such as pH buffers, pH adjusters, organic and 
inorganic salts, alcohols (e.g., ethanol), sugars, amino acids, or 
surfactants incorporated therein. The aqueous solution or solvent may also 
be a mixture of water and minor amounts of one or more cosolvents, 
including agronomically suitable organic cosolvents, which are miscible 
therewith, or may form an emulsion therewith. Examples of suitable alcohol 
solvents include but are not limited to methanol, ethanol, propanol, 
isopropanol, hexanol, as well as glycols such as ethylene glycol, and the 
like. Examples of suitable nitriles include acetonitrile, propionitrile, 
butyronitrile, benzonitrile, and the like. Examples of suitable amides 
include formamide, N,N-dimethylformamide, N,N-dimethylacetamide, and the 
like. Examples of suitable esters include methyl acetate, ethyl acetate, 
and the like. Examples of suitable ketones include acetone, methyl ethyl 
ketone, diethyl ketone, and the like. Examples of suitable ethers include 
diethyl ether, tetrahydrofuran, dioxane, dimethoxyethane, and the like. 
Any two or more of any of the foregoing solvents may be utilized in the 
coating composition as well. Currently preferred solvents include water, 
particularly distilled water, isopropanol, acetonitrile, and combinations 
of any two or more of these solvents. 
In one preferred embodiment, the covalent complex is solubilized in solvent 
to achieve a concentration of between about 0.01 and about 10 percent by 
weight, preferably between about 0.1 and about 1 percent, and more 
preferably about 0.125 percent. 
In addition to the foregoing solvents, the heparin coating compositions of 
the present invention may also include therein various conventional 
additives. Examples of additives which may be incorporated into the 
compositions of the present invention include but are not limited to 
benzalkonium, 4-dimethylaminopyridinium, tetrabutylammonium halides, and 
the like. 
The coating composition may be coated onto any of a wide variety of surface 
materials to provide anti-thrombogenic effects when the coated surface is 
contacted with blood. Suitable surfaces which may be coated with the 
coating composition of the present invention include any surface which has 
an affinity or attraction to the hydrophobic silyl moiety. Such surfaces 
are typically hydrophobic surfaces. Examples of suitable surfaces include 
but are not limited to hydrophobic polymers such as polycarbonate, 
polyester, polypropylene, polyethylene, polystyrene, 
polytetrafluoroethylene, polyvinyl chloride, polyamide, polyacrylate, 
polyurethane, polyvinyl alcohol, and copolymers of any two or more of the 
foregoing; siloxanes such as 2,4,6,8-tetramethylcyclotetrasiloxane; 
natural and artificial rubbers; glass; and metals including stainless 
steal and graphite. 
The heparin coating composition can be applied to the surface to render the 
blood-contacting surface non-thrombogenic. Any suitable method for 
applying the coating composition to the surface may be employed. One 
suitable method for applying the coating composition to the 
blood-contacting surface to be treated is by dipping the blood-contacting 
surface into the coating composition containing the covalent complex of 
the present invention. A liquid coating composition containing the 
covalent complex of the present invention may be prepared using any of the 
solvents described above. The surface is dipped or immersed into a bath of 
the coating composition. Typically, the dipping process is carried out at 
elevated temperatures, such as between about 30.degree. C. and about 
80.degree. C. for a period of between about 5 and about 20 minutes, 
preferably about 10 minutes. Thereafter, the surface is allowed to remain 
in contact with the coating composition containing the covalent complex 
for a period of between about 15-60 minutes, preferably about 20 minutes, 
at room temperature. 
Another method which may be employed for coating or applying the heparin 
coating compositions of the present invention on to blood-contacting 
surfaces includes a pumping or spraying processes. According to the 
pumping process, the coating solution having a concentration of between 
0.05 and about 5 percent (w/v) is pumped through the device where the 
blood contact will occur for 30 minutes. Thereafter the excess coating 
materials is washed out with water or saline. The blood contacting surface 
can be coated by the material of the current invention simply by spraying 
with the above-mentioned coating solution as well. The coated surface is 
typically washed with water before drying. 
Following coating of the composition onto the surface, the surface is 
typically washed with water or saline prior to drying. Advantageously, the 
foregoing methods for applying the coating composition to a surface are 
relatively quick, commercially feasible and cost-effective. 
The hydrophobic interactions between the hydrophobic surfaces to be coated 
and the hydrophobic silyl moieties of the covalent complex form the bond 
between the covalent complex and the surface. This hydrophobic interaction 
is sufficiently strong so as to provide a stable bond between the covalent 
complex and the surface. The present inventors have now discovered a 
method for binding heparin to a surface by using hydrophobic binding 
interactions which provide certain advantages over the method relied upon 
in previous coating technologies. The presence of ionic species in blood 
does not disrupt the hydrophobic interaction between the covalent complex 
of the present invention and the surface. 
The coating compositions of the present invention can be applied to the 
blood-contacting surfaces of any of a wide variety of medical devices to 
provide a non-thrombogenic medical device. Examples of specific medical 
devices which may be advantageously treated with the coating compositions 
of the present invention include but are not limited to oxygenators, 
oxygenator circuits, heart-lung bypass circuits, blood gas exchange 
devices, blood filters, artificial blood vessels, artificial valves, 
prosthetics, stents, catheters, heat exchangers, and hypodermic needles. 
Other examples of medical devices which would benefit from the application 
of the non-thrombogenic coating compositions of the present invention will 
be readily apparent to those skilled in the art of surgical and medical 
procedures and are therefore contemplated by the instant invention. 
The following examples are provided to illustrate the present invention, 
and should not be construed as limiting thereof. In these examples, "ml" 
means milliliter; "L" means liter, "mg" means milligrams, "g" means grams, 
"mol" means moles, "M" means molar concentration, "Me" means methyl; "Bn" 
means benzyl, "nBu.sub.4 NI" means tetrabutyl-ammonium iodide, ".degree. 
C." means degrees Centigrade. All percentages are in percent by weight 
unless otherwise indicated.

EXAMPLE 1 
This example demonstrates the method for preparing the covalent complexes 
of the present invention. 
Synthesis of Benzyl(chloromethyl)dimethylsilane 
In a 2 L 3-necked flask equipped with a nitrogen inlet, a 500 ml dropping 
funnel and a thermometer, was placed 500 ml of tetrahydrofuran. 
Chloro(chloromethyl)-dimethylsilane (100 ml, 0.744 mol) was added by 
syringe and the colorless solution cooled to 0.degree. C. in an 
ice/acetone bath. Then benzylmagnesium chloride (2.0 M solution, 400 ml, 
0.8 mol) was transferred to the dropping funnel by syringe and added 
dropwise over 2 hours. A slightly exothermic reaction was observed and the 
temperature was maintained below 10.degree. C. After addition of the 
chloro(chloromethyl)dimethylsilane was complete, the ice bath was allowed 
to warm up to room temperature without heating, and the reaction mixture 
was stirred overnight. Thereafter hexane (300 ml) was added and the 
reaction mixture was worked up by dropwise addition of saturated aqueous 
ammonium chloride (300 ml) and transferred to a 2 L separatory funnel with 
additional hexane (300 ml). After partitioning, the organic layer was 
washed with saturated aqueous ammonium chloride (200 ml) and saturated 
aqueous sodium chloride (200 ml). The combined aqueous layers were 
backwashed with hexane (2.times.500 ml). The combined organic layers were 
dried over magnesium sulfate, evaporated on the rotovap, and finally 
evaporated with an oil pump to give a colorless oil 162.0 g (109.5% 
yield). A quantitative yield was assumed with a purity of the crude 
product as 91.3%. 
Grignard Reaction of Bn(SiMe.sub.2 CH.sub.2).sub.n Cl and ClSiMe.sub.2 
CH.sub.2 Cl to give Bn(SiMe.sub.2 CH.sub.2).sub.n+1 Cl 
In a 500 ml 3-necked flask equipped with a condenser-nitrogen inlet, a 
septum and a thermometer, was placed magnesium powder (7.5 g, 0.31 mol), a 
catalytic amount of iodine and tetrahydrofuran (100 ml). The brown mixture 
was heated to reflux briefly with a heat gun until the color of iodine 
disappeared. Bn(SiMe.sub.2 CH.sub.2).sub.n Cl (0.2 mol) was added by 
syringe and washed down with the tetrahydrofuran (2.times.25 ml). The 
reaction was initiated with a heat gun. An exothermic reaction was 
observed and the reaction flask was placed in a water bath until the 
exothermic reaction subsided. The resulting grey mixture was heated to 
reflux for 24 hours. The reagent was then cooled to room temperature and 
cannulated into a pressure filter funnel where it was added directly into 
another 500 ml round bottom flask in which was placed a solution of 
ClSiMe.sub.2 CH.sub.2 Cl (27.0 ml, 0.2 mol) in tetrahydrofuran (50 ml) at 
room temperature. The magnesium residue was washed down with 
tetrahydrofuran (2.times.25 ml). The reaction mixture was heated to reflux 
overnight. The resulting grey suspension was worked up by addition of 
saturated aqueous sodium bicarbonate (50 ml) and transferred to a 500 ml 
separatory funnel with hexane (200 ml). After partition, the organic layer 
was washed with saturated aqueous sodium bicarbonate (50 ml) and saturated 
aqueous sodium chloride (50 ml). Then the combined aqueous layers were 
back-washed with hexane (2.times.100 ml). The combined organic layers were 
dried over magnesium sulfate, evaporated on the rotovap, and finally 
evaporated on the oil pump to give an amber oil, which can be purified by 
distillation to give a colorless oil. Yield is approximately 80 percent. 
Conversion of Bn(SiMe.sub.2 CH.sub.2).sub.n Cl to Bn(SiMe.sub.2 
CH.sub.2).sub.n OH 
Bn(SiMe.sub.2 CH.sub.2).sub.n Cl (0.16 mol) was dissolved in 
dimethylformamide (300 ml) in a 1 L 3-necked flask. Potassium acetate (50 
g, 0.5 mol) was added followed by nBu.sub.4 NI (4.0 g, 0.01 mol) and the 
reaction mixture was stirred in a 135.degree. C. oil bath for 24 hours. 
The reaction mixture was worked up by cooling to room temperature, 
transferred to a 1 L separatory funnel with hexane (500 ml), and washed 
with saturated aqueous sodium chloride (3.times.100 ml). The combined 
aqueous layers were back-washed with hexane (3.times.300 ml). The combined 
organic layers dried over magnesium sulfate, and evaporated on the rotovap 
to give an amber oil. The oil was dissolved in methanol (400 ml). Then a 
generous amount of freshly prepared sodium methoxide was added to adjust 
the pH to &gt;10 and the reaction mixture was heated to reflux for 2 hours. 
The reaction mixture was worked up by neutralizing with acetic acid 
(AcOH), and evaporated to dryness. The dried mixture was chromatographed 
with silica gel in a 6.5.times.100 cm (height of silica 40 cm) flash 
column and eluted with 0-30% ethylacetate/hexane Rf (tlc with silica gel 
60 F.sub.254 on Al plates, eluted with 20% ethylacetate/hexane and 
observed as a darkened spot under UV lamp) of product=0.1! to give the 
desired product as a slightly yellow oil. The yield is approximately 80 
percent. 
Conversion of Bn(SiMe.sub.2 CH.sub.2).sub.n OH to Bn(SiMe.sub.2 
CH.sub.2).sub.n OCO.sub.2 N(COCH.sub.2).sub.2 
Triphosgene (60 g, 0.2 mol) was dissolved in methylene chloride (200 ml) 
and stirred at 0.degree. C. under nitrogen in a 1 L 3-necked flask 
equipped with thermometer, dropping funnel and nitrogen inlet. Sodium 
carbonate (65 g, 0.6 mol) was added followed by Bn(SiMe.sub.2 
CH.sub.2).sub.n OH (0.13 mol dissolved in 200 ml methylene chloride) 
dropwise over 30 minutes. Thereafter, the ice/acetone bath was allowed to 
warm to room temperature without addition of heat. The reaction mixture 
was allowed to stir overnight and worked up the next morning by filtering 
through a sintered glass funnel, which was washed down with toluene 
(PhCh.sub.3) (200 ml). Thereafter the filtrate was evaporated on the 
rotovap to give a colorless oil, which was dissolved in methylene chloride 
and stirred in an ice bath under nitrogen. N-Hydroxysuccinimide (30 g, 
0.26 mol) was added, followed by dropwise addition of triethylamine 
(Et.sub.3 N) (40 ml, 0.28 mol) over 15 minutes. The resulting cloudy 
mixture was stirred at room temperature for 1 hour. The reaction mixture 
was then worked up by diluting with hexane (600 ml), washed with saturated 
aqueous ammonium chloride (3.times.100 ml), and the combined aqueous 
phases backwashed with hexane (2.times.200 ml). The combined organic 
phases were dried over magnesium sulfate and evaporated to dryness on the 
rotovap to give an amber oil. The oil was chromatographed with silica gel 
in a 6.5.times.100 cm (height of silica 40 cm) flash column and eluted 
with 20-50% ethyl acetate/hexane Rf (tlc with silica gel 60 F.sub.254 on 
Al plates, eluted with 20% ethylacetate/hexane and observed as a darkened 
spot under UV lamp) of product=0.1! to give an amber syrup. The yield is 
approximately 70 percent. 
Conlugation of Heparin with Bn(SiMe.sub.2 CH.sub.2).sub.n OCO.sub.2 
N(COCH.sub.2).sub.2 
Heparin (ammonium free, average molecular weight 10,000; 100 g, 10 mmol) 
was dissolved in 500 ml of water in a 4000 ml beaker with stirring. DMF 
(400 ml) was added followed by DMAP (5.0 g, 40 mmol) and the pH was 
monitored by a 702 SM Titrino with program set at: end pont=8.50, max flow 
rate=1 ml/min., min. flow rate=10 .mu.l/min., pause time=60 sec., stop 
criteria=time (inf.) and connected to a reservoir of 1 M sodium hydroxide. 
Bn(SiMe.sub.2 CH.sub.2).sub.n OCO.sub.2 N(COCH.sub.2).sub.2 (10.times. 
mmol) in DMF (100 ml) was added and the pH began to drop. The program was 
started as soon as the pH dropped to just below 8.5. The resulting milky 
mixture was allowed to stir at room temperature while the pH of the 
reaction mixture was maintained at 8.5 by Titrino by automateic addition 
of 1M sodium hydroxide as necessary. The amount of 1 M sodium hydroxide 
used (in ml) was plotted against reaction time (in hours) as the reaction 
profile. The reaction mixture was worked up, when the reaction profile 
begins to flatten out, by trituration with acetone (2 l) and the white 
suspension is filtered through a sintered glass funnel to give a white 
solid residue, which was contaminated with DMF and some of the residual 
N-hydroxy-succinimide. This crude material can be purified by soxhlet 
extraction with acetone overnight to give a white powder. The yields are 
gernally in the high 90's. 
Procedure for Coating the Complexes onto the Surface 
The complex is completely dissolved in 1/3 volume of distilled water with 
gentle stirring. A solvent such as isopropyl alcohol or acetonitrile is 
added in the amount of 2/3 volume and the solution is mixed. The thus 
prepared coating solution has a complex concentration of between 0.01 and 
10 percent based upon the weight of the solution. The material to be 
coated is dipped in the coating solution at elevated temperatures usually 
ranging from 30.degree. C. to 50.degree. C. for about 10 minutes, followed 
by standing in room temperature for about 20 minutes. The coated material 
is taken out of the coating solution and rinsed thoroughly with distilled 
water or saline solution prior to drying. 
EXAMPLE 2 
This example demonstrates one technique for applying the coating 
compositions of the present invention to surfaces intended to directly 
contact blood. 
The covalent complex (100 mg) produced according to Example 1 above is 
solubilized in 1/3 volume, 27 ml of distilled water with gentle stirring. 
Thereafter 2/3 volume, 53 ml of isopropyl alcohol or acetonitrile is 
added. The resulting concentration of the covalent complex in solution is 
about 0.125 percent by weight. The blood-contacting surface to be coated 
with the coating composition is dipped into the coating composition for 10 
minutes at a temperature of between 30.degree. C. to 50.degree. C. 
Thereafter, the surface is allow to remain in contact with the coating 
composition for approximately 20 minutes, at room temperature. Thereafter, 
the coated surface is removed from the coating composition and rinsed 
thoroughly with distilled water or saline solution. 
EXAMPLE 3 
This example demonstrates the stability of the heparin coating compositions 
of the present invention on surfaces exposed to ionic environments. 
Various surfaces coated according to Example 2 were evaluated for heparin 
activity after washing with 3 percent (by weight) sodium chloride 
solution. Surface heparin activity is measured in mIU/cm.sup.2 according 
to the technique described in Sigma Diagnostics, Heparin, Procedure No. 
CRS 106. 
Results obtained from the evaluation of heparin activity on a polycarbonate 
surface after washing with sodium chloride are set forth in Table 1 below. 
TABLE 1 
______________________________________ 
Concentration of 
Percent by volume of isopropyl alcohol 
covalent complex in 
In IPA/H.sub.2 O solvent 
solution (% w/v) 
50 55 60 65 70 75 
______________________________________ 
2 21.8 
1 21.6 24.5 
0.5 9.9 23.2 20.7 23.4 18.0 5.2 
0.25 6.8 8.0 17.6 16.3 14.7 14.9 
0.125 7.1 10.3 5.4 13.0 13.1 11.3 
______________________________________ 
Results obtained from the evaluation of heparin activity on a siloxane 
surfaces (TMCTS) after washing with sodium chloride are set forth in Table 
2 below. 
TABLE 2 
______________________________________ 
Concentration of 
Percent by volume of isopropyl alcohol 
covalent complex in 
In IPA/H.sub.2 O solvent 
solution (% w/v) 
50 55 60 65 70 75 
______________________________________ 
2 9.0 
1 4.9 
0.5 
0.25 0.4 3.8 3.5 2.0 1.1 2.4 
0.125 4.4 1.6 2.5 4.8 1.0 1.9 
______________________________________ 
Results obtained from the evaluation of heparin activity on a polyester 
surface after washing with sodium chloride are set forth in Table 3 below. 
TABLE 3 
______________________________________ 
Concentration of 
Percent by volume of isopropyl alcohol 
covalent complex in 
In IPA/H.sub.2 O solvent 
solution (% w/v) 
50 55 60 65 70 75 
______________________________________ 
1 
0.5 
0.25 4.5 4.4 5.5 3.7 5.3 
0.125 2.1 2.5 2.9 1.3 2.0 1.7 
______________________________________ 
Results obtained from the evaluation of heparin activity on a polyvinyl 
chloride surface after washing with sodium chloride are set forth in Table 
4 below. 
TABLE 4 
______________________________________ 
Concentration of 
Percent by volume of isopropyl alcohol 
covalent complex in 
In IPA/H.sub.2 O solvent 
solution (% w/v) 
50 55 60 65 70 75 
______________________________________ 
1 
0.5 
0.25 2.6 2.9 10.0 6.5 4.0 2.8 
0.125 1.8 2.1 1.0 2.1 2.1 2.1 
______________________________________ 
Results obtained from the evaluation of heparin activity on a stainless 
steel surface after washing with sodium chloride are set forth in Table 5 
below. 
TABLE 5 
______________________________________ 
Concentration of 
Percent by volume of isopropyl alcohol 
covalent complex in 
In IPA/H.sub.2 O solvent 
solution (% w/v) 
50 55 60 65 70 75 
______________________________________ 
1 
0.5 
0.25 12.9 13.1 8.3 11.0 12.9 13.8 
0.125 10.6 12.3 10.4 10.2 8.8 11.8 
______________________________________ 
The combined results demonstrate that the heparin coating compositions of 
the present invention exhibit improved heparin activity on a wide variety 
of surface materials. 
The foregoing is illustrative of the present invention and is not to be 
construed as limiting thereof. The invention is defined by the following 
claims, with equivalents of the claims to be included therein.