DD296220A5 - METHOD FOR PRODUCING SURFACE MODIFIED CELLULOSE MEMBRANES WITH IMPROVED BLOOD CONTRASTING - Google Patents

Abstract

The invention relates to a process for the preparation of surface-modified cellulose membranes having improved blood compatibility for use in blood detoxification, in particular in hemodialysis, haemodiafiltration and haemofiltration. The process described is characterized by a two-stage derivatization, wherein the primary halogenation achieved on the membrane surface for reaction with halocarboxylic acid halides is subsequently used for a partial application of sulfonate groups. Under observance of defined reaction conditions, this polymer-analogous reaction is localized on the membrane surface, whereby the morphological basic structure of the molding is maintained without reducing the separation efficiency. With the present invention, it is possible to make available modified cellulose surfaces which, when in contact with blood, have a complement activation which is markedly reduced compared to the starting membrane or decreased leukopenia. Oberflaechenmodifizierung; Chloroacetylation / sulfonation; Blutvertraeglichkeit; detoxification of blood}

Description

Field of application of the invention

The invention relates to a process for producing surface-modified cellulose membranes which have a significantly improved blood compatibility compared to the non-treated molded body. Thus, such modified cellulose moldings, when used as a dialysis membrane, lead to a complement activation which is markedly reduced compared to the starting membrane or to a severely weakened leukopenia. The performance of the unmodified dialysis membrane is maintained by the modification.

Characteristic of the known state of the art

The availability of polymeric biomaterials for clinical use is a requirement urgently demanded by the medical community for improved patient care. Also in the field of extracorporeal blood detoxification there has been no lack of attempts to equip the worldwide because of their excellent dialysis characteristics still preferred in the artificial kidney used Regeneratcellulosemembran by modification for increased blood compatibility. Cellulosic modifications of this kind are therefore absolutely necessary, since the phenomena of complement activation and leukopenia triggered upon contact with blood / foreign surfaces are particularly pronounced for this type of membrane and can be attributed to a considerable degree to the presence of cellulose-resistant hydroxyl groups. (D.E. Chenoweth: Compliment activation during hemodialysis, Artificial Organs 8,1984,281). For this reason, the previously approached approaches are directed to a physical or chemical masking of the hydroxyl groups on the blood contact side of the cellulose membrane. The modifications used for this range from polymer and biomolecule coatings, from admixtures of hemocompatible additives into the membranes to be formed from the spinning solutions, chemical OH group crosslinking, and even derivatizations (DE-OS 3742072 and 3814326, EP-PS 0319862, EP-A). PS 0330106, EP-PS 0339200, DE-OS 3805992, DE-OS 3840175, DD-PS 243643, DE-OS 3430503, DE-OS 3524596, JP-PS 82/095375, EP-PS 53473, US-PS 4210529, US-PS 4051040, WO 88/06476) and graft modifications (EP-PS 266795, DE-OS 3410133, DE-OS 3438531, US-PS 4280970, DE-OS 3341113, DD-PS 260930, DD-PS 260932, DD PS 136702). In principle, the requirements of a high sterilization and storage stability are met comparatively better than with physical masking via covalent bonding of the modifying agent to the molding. On the basis of covalent linkages, cellulose graft copolymer modifications have proven particularly effective at lowering complement activation because of the variety of functionalities available over the chemical structure of the copolymer - but because of multi-step operations and extremely high purity bids (protection of reactive function), this variation is very high Process engineering effort marked. Because of the simplified technical feasibility of cellulose derivatizations, patent applications based on this modification take the greater part. Thus, in the patents DE-OS 3524596 and DD-PS 243643 a

modified cellulose of the general formula Cell-R'-x-y presented with significantly improved Blutverträglichkelten. In addition to diethylaminoethylcellulose as the most striking representative of this structural class, sulfonate, phosphonate, carboxyl and silicotoalkyl groups have been proposed in the abovementioned inventions for the end group-determining γ in addition to the -NfV group. The most significantly reduced level of complement activation is achieved when the average degree of substitution - defined as the average number of substituents per glucose anhydride unit - of the final cellulose emulsion is within a range of 0.02 to 0.07. To set such degrees of substitution, the cellulose derivative is mixed with an initial DS of about 0.4 in the appropriate proportions with the Cuoxamträgerlösung. However, due to this combined derivatization / incorporation variant, the disadvantage of the leachability of the derivatized modifying agent is not eliminated.

In the patent DE-OS 3814326 the object of a covalent fixation is achieved in that the modifying agents, dissolved in polar solvents, optionally passed with the catalysts required for the reaction and auxiliaries, on a surface of the dialysis membrane. The spectrum of modifying agents used for this heterogeneous one-step reaction is extremely extensive and leads to cellulose ester and / or ether adducts. In principle, however, after the covalent OH group masking, either an unfunctionalized or an ionic / polar-functionalized membrane surface structure is present, since the one-step reactions used preclude a combination of both.

Object of the invention

It is an object of the invention to develop a method which decisively improves the blood compatibility of regenerated cellulose membranes by substantially preventing leukopenia and complement activation. In this case, the morphological basic structure of the membrane should be largely retained, so that their dialysis performance is not reduced.

Explanation of the nature of the invention

The object is to provide via a two-stage heterogeneous cellulose derivatization a hydrophobically / hydrophilically active surface structure covalent and with complete masking dor near-surface hydroxyl groups by aftertreatment of the molding to achieve a comparison with the unmodified starting membrane significantly improved blood compatibility.

According to the invention the object is achieved in that the surface of the cellulosic! Shaped body with an inert inert in the reaction medium Halogencarbonsäurehalogenid, preferably chloroacetyl chloride, reacted heterogeneously and then partially sulfonated. To introduce the halogen function, the Cellulosemembraneri be conditioned on an aprotic-polar reaction medium, such as dimethylformamide (DMF) and reacted at temperatures of 2O ⁰ C to 80 ° C within a time of 2 to 600min base catalysis with the Halogencarbonsäurehalogenid. As a result, after a surface-covering hydrophobizing masking of the cellulosic hydroxyl groups, a partial re-hydrophilization of the surface is achieved via the subsequent sulfonation.

For this reaction, a 0.1 to 4-fold molar acyl group concentration of the halogenating agent is suitably used with respect to the total supply of cellulosic hydroxyl groups and supported by a 1- to 2-fold molar triethylamine (TEA) concentration with respect to the acyl group concentration of the halogenating agent, the absolute concentration of the halogenating agent should be within a range of 0.05 to 0.2 mol / l. Within the limits set by the reaction conditions, the average degree of halogenation DS, defined as the hydroxyl groups substituted per glucose anhydride moiety, is determined to be in the range of from 0.1 to 0.4 with respect to the total molding, with near complete substitution of the near-surface hydroxyl groups from ESCA moieties. Measurements were detected.

For the downstream sulfonation of the halogen-functionalized membrane, a cold-saturated aqueous bisulfite solution is used, so that there is a high molar excess of the sulfonation component compared to the carrier-fixed halogen groups. For this purpose the halogenated cellulosic molded bodies were umkonditioniert water and contacted with the aqueous bisulphite solution at temperatures from 6O ⁰ C to 80 ° C within a time of 1 to 12 hours with addition of a Lewissäiire-catalyst. The sulfonating agent is the hydrosulfite resulting from the hydrolysis of the bisulfite.

Since the present in the aqueous medium equilibrium of the two tautomeric boundary structures of the hydrogen sulfite accordingly

© G?

 -Ο I ·· * -. - '-

- ~ - - sI s .-

O &'

is shifted significantly to the left, the competing sulfitation compared to the sulfonation clearly pushed back. The modification process is summarized by the following reaction steps:

TEA (OH) .3-, n

I. CeIl- (OH) ₃ + mXi -CR-X- ₃ . > Cell

G - (TiHX ₁ (OC-RX =) ,,,

II, 1/2 KaSaO ₀ + 1/2 HsD> KHSO,

(OH

_e - _m

τη jS * - * /

CeI I + π © | 3ς ^ ~ θ] ^θ > Cell - (OC-RX =) _m _ _r ,.

^Χ (OC-RX ₃ ) _m ^X 0 -ί% -η) χ _ζ ⁰ \ δ

ο\ / y °

(OC-R-S 1

Ii ν. 0 Ό

Xi = halogen

X ₂ = halogen

R = (-CH ₂ -Ip

ρ = 1-5

m, η = effective for derivatization effective mole fraction of the derivatizing agents, where η <m <3

The hydrophilic / hydrophilic surface-modified flat or hollow membranes of cellulose combined in this way are characterized by an almost complete restriction of leukopenia and complement activation, without impairing the dialysis performance of the cellulose membrane.

embodiment

Alcohol-depleted flat membranes of regenerated cellulose were reconstituted to DMF and reacted with the 4-fold molar excess of chloroacetyl chloride and triethylamine in proportion to the total molar hydroxyl group concentration of the cellulosic membrane at 50 ° C for 15 min in DMF.

The absolute concentration of chloroacetyl chloride is 0.14 mol / l. A corresponding device allowed the all-round overflow of the membrane with the Modltlzierungslösung so that a uniform surface modification was ensured.

Subsequently, the membranes were washed thoroughly with water and with cold saturated aqueous K2S ₂ O6 solution E h at 80 ⁰ C flows over. The catalyst used was AICI ₃ . After lOmaliger water wash the membranes were partly

vacuum dried, z.T. subjected to water swelling of the characterization.

The end-modified membrane has a mass increase of 6.2%. The IR spectroscopic studies confirm the modification effect by band vibrations of the carbonyl ester group at 1745 cm ^-1 and the sulfonic acid group in the range from 1200 to 1300 cm ^-1 . The equilibrium contact angle of the membrane / water / air system undergoes, after chloroacetylation, a marked increase from 12.0 ° to 56.7 ° relative to the regenerated cellulose, while the sulfonation again causes a significant drop in the angle to 19.1 ° due to rehydrophilization. A pronounced hysteresis of the contact angle measurements combined with excludable roughness effects makes it possible to clearly combine hydrophilic / hydrophobic surface areas. Biomedical testing revealed an increase in total protein adsorption of HSA and HFB from 1.2 μg / cm ^{^} for cellulose to 4.1 μο / cm ² for the so-modified surfaces.

The dialysis performance of the starting membrane for urea of P _u = 37.0 x 10 ^-3 cm / min was not affected by the modification made.

By means of C 3a of the Arg studies, a decrease in complement activation was registered to 10% of the value measured for unmodified cellulose.

The electrophoresis mobility test demonstrated a 90% reduction in cytokine release compared to the standard. The haemolysis test for acute in vitro toxicity was based on the provisions of

2. Pharmacopoeia toxic harmlessness.

Claims (8)

1. A process for the preparation of surface-modified cellulose membranes having improved blood compatibility, characterized in that a cellulosic molded body with the inert in an aprotic-polar reaction medium halocarboxylic halide bason catalyzed at 2O ⁰ C to 8O ⁰ C within 2 to 600 min heterogeneously reacted, and The introduced halogen function is then partially sulfonated with bisulfite and then subjected to a washing / rinsing process in a known manner. 2. The method according to claim 1, characterized in that the halocarboxylic acid halides are chloroacetyl chloride, bromoacetyl chloride or bromoacetyl bromide. 3. The method according to claim 1, characterized in that dimethylformamide, cyclohexanone or acetone is used as the reaction medium. 4. The method according to claim 1, characterized in that the acyl group concentration of the halogenating agent is 0.05 to 0.2 mol / l. 5. The method according to claim 1 and 4, characterized in that is used as the base triethylamine in a 1 to 2-fold molar concentration with respect to the acyl group concentration of the halogenating agent. 6. The method according to claim 1,4 and 5, characterized in that a 0.1 to 4-fold molar acyl group concentration of the halogenating agent with respect to the total concentration of cellulosic hydroxyl groups in the molding is used. 7. The method according to claim 1, characterized in that the sulfonation is carried out within a temperature range of 60 ⁰ C to 80 ⁰ C for 1 to 12 hours Lewis acids catalysed. 8. The method according to claim 1 and 7, characterized in that the sulfonation in the form of a cold saturated aqueous Bisulf itlösung in a high molar excess over the concentration of carrier-fixed halogen groups with a degree of substitution DS of 0.1 to 0.4 is used.