AU631903B2 - A method for producing a biocompatible surface - Google Patents

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.I [i DPI DATE 06/02/91 AOJP DATE 21/03/91 APPLN IU 59502 PCT NUMBER PCT/AU90/00292

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INTERNATIONAL pirr1 j1j, u u ji l r V (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 91/00745 A61,33/00 AlI (43) International Publication Date: 24 January 1991 (24.01.91) (21) International Application Number: PCT/AU90/00292 (74) Agent: GORDON, Glen, Howard; Arthur S. Cave Co., Level 10, 10 Barrack Street, Sydney, NSW 2000 (AU).

(22) International Filing Date: 6 July 1990 (06.07.90) (81) Designated States: AT, AT (European patent), AU, BB, BE (30) Priority data: (European patent), BF (GAPI patent), BG, BJ (GAPI PJ 5139 7 July 1989 (07.07.89) AU patent), BR, CA, CF (OAPI patent), CG (OAPL patent), CH, CR (European patent), CM (GAPI patent), DE*, DE (European patent)*, DK, DK (European patent), (71) Applicant (for all designated States except US): MAC- ES, ES (European patent), Fl, FR (European patent), NAUGH: PTY. LIMITED [AU/AU]; 47-49 Henderson GA (GAPI patent), GB, GB (European patent), HU, IT Street, Turrella, NSW 2205 (European patent), JP, KP, KR, LK, LU, LU (European patent), MC, MG, ML (GAPI patent), MR (GAPI pa- (72) Inventor; and tent), MW, NL, NL (European patent), NO, RO, SD, Inventor/Applicant (for US only) HILLS, Brian, Andrew SE, SE (European patent), SN (GAPI patent), SU, TD [AU/AU]; "West Tree", Dumaresq Road, Dumaresq Via (GAPI patent), TG (GAPI patent), US.

Armidale, NSW 2350 (AU).

Published With international search report.

(54) Title: A METHOD FOR PRODUCING A BIOCOMPATIBLE SURFACE (57) Abstract The inven:ion relates to methods for producing biocompatible surfaces by coating them with phospholipid and binding the phospholipid to the surface by means of ultrasonication.

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1 *See back of page WO 91/00745 PCT/AU90/00292 1 A METHOD FOR PRODUCING A BIOCOMPATIBLE SURFACE TECHNICAL FIELD The present invention relates to methods for producing biocompatible surfaces by coating them with phospholipid and binding the phospholipid to the surface by means of ultrasonication.

BACKGROUND ART A major problem experienced with medical equipment and devices that comes into contact with the blood flow, such as cannulae, in dwelling-electrodes and catheters, is that blood clots may form on their surfaces. The formation of blood clots on the surfaces of these instruments is dangerous and may prove fatal if the clots are washed off by the blood flow into the vascular system.

It has been reasoned that the best non-thrombogenic surface model is provided by the lining of blood vessels themselves the endothelial lining. Some blood vessels, such as the aorta and cerebral vessels, have extremely hydrophobic inner surfaces. Electron microscopic studies of the inner surface of these vessels has revealed that they are lined with an oligolamellar lining of phospholipid. It is thought that mimicking the lining of the blood vessels on artificial surfaces should substantially overcome the abovementioned problems.

Early attempts at coating surfaces with phospholipid proved unsuccessful. Surfaces were left in contact with phospholipid or phospholipid/hyaluronic acid suspensions and then tested in blood stirred by a magnetic stirrer to mimic flowing blood. However, blood clots still developed on these surfaces.

US Patent 4 426 330 (Sears) discloses a chemically modified phospholipid for more stable coatings. US Patent 4 438 329 (Chapman) discloses a phospholipid chemically bonded to a polymer for coating surfaces. However, the introduction of new, chemically modified phospholipids into a human body or blood stream may have unforseen LU90/00292 WO 91/00745 PCT/AU90/00292 -2 W results. Also, the expense and difficulty of preparing these modified phospholipid substances is a disadvantage for their use.

There is therefore an advantage in finding a way to coat surfaces with natural phospholipids on which flowing P Sblood does not coagulate or form clots. A method of coating with phospholipids to produce non-thrombogenic c surfaces has therefore been developed. c

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DISCLOSURE OF INVENTION N It is therefore an object of the present invention to s is provide a method for producing a biocompatible surface by N coating it with phospholipid. g The present invention concerns a method for producing ,ts a biocompatible surface, by coating the surface with m phospholipid characterised by immersing the surface to be coated in a bath containing a suspension of phospholipid 0 in a liquid in which it is sparingly soluble, and then .s, ultrasonicating the bath to coat the surface with i phospholipid.

g Another aspect of the invention concerns pre-treating g the surface to be coated. The surface is firstly immersed in a phospholipid solution. The solution comprises fphospholipid substantially dissolved in a solvent in which d it is soluble, such as methanol or chloroform. The

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surface is then removed from the solution and the solvent allowed to evaporate off. The dry surface is then a )id h subjected to the ultrasonication process described above.

s Any suitable surface may be coated, such as metal, to glass, plastics or ceramics. Any phospholipid may be used c )ped and some examples are described in Table 1. c ped C 7 WO 91/00745 P~/AU90/00292 -3- TABLE 1 Phosphoalyerides phosphatidic acids cytidylic phosphoglycerides (CDP diglyceride) choline phosphoglycerides ethanolamine phosphoglycerides N-methylethanolamine phosphoglycerides N,N-dimethylethanolamie phosphoglycerides N-acylethanolamine phosphoglyceride serine phosphoglycerides N-2-(hydroxyethyl)alanine phosphoglyceride glycerol phosphoglycerides glycerophosphate phosphoglycerides phosphatidyiglycerol phosphoglyceride (diphosphatidylglycerol) mono and diacylglycerol phosphoglycerides (lysobisphosphatidic acids) glucosaminylglycerol phosphoglyceride 0-amino acid esters of glycerol phosphoglycerides inositol phosphoglyceride inositol monophosphate phosphoglyceride inositol diphosphate phosphoglyceride monomannosyl-hexamannosyl inositol phosphoglycerides glucose phosphoglyceride 0-diglucosylglycerol phosphoglyceride Phosphoglvcolipids diacyl (glyceryiphosphoryldiglucosyl) glycerol Phosphodiol lipids acyl dihydroxyacetone phosphate alkyl dihydroxyacetone phosphate Phosphosphingolipids sphingomyelin (ceramide phosphorylcholine) ceramide phophorylethanolamine ceramide phosphorylglycerol ceramide phosphoryiglycerophosphate ceramide phosphorylinositol-containing lipids The preferred phospholipid is phosphatidylcholine, (lecithin).

The ultrasonic treatment is conducted in the normal manner using commercially available ultrasonic equipment.

a. a^ ^i ^iM iia,«~l -I-m^~-~I~UPI~II~LI~rOCU~ U90/00292 WO 91/00745 PCT/AU90/00292 4 The suspension of phospholipid used in the bath comprises preferably finely divided phospholipid suspended in a liquid in which it is only sparingly soluble. The suspension is preferably an aqueous suspension. d Phospholipid is added to the suspension in solid form e and is suspended by an initial ultrasonication to form liposomes. The phospholipid is preferably suspended at a e concentration of 0.1 to 10% w/v, most preferably 1 to 2% p w/v. The liquids that may be used to suspend the b phospholipid in accordance with the present invention t include water and physiological saline solutions.

Any ultrasound device can be used in accordance with the present invention, such as the Model G112SPIT (serial No. 11254) produced by Laboratory Supplies Co. Inc., New York.

The method of coating a surface with phospholipid may t also comprise a pre-treatment step, which involves a dissolving phospholipid in a solvent; placing the surface to be coated into the phospholipid/solvent solution to allow initial gross deposition of phospholipid onto the s surface; removing the coated surface from the phospholipid 1 solvent solution; evaporating off residual solvent on the coated surface; placing the coated surface into the suspension; and ultrasonicating the coated surface as described previously.

Surfaces that may be coated and phospholipids that c may be used in accordance with the present invention are t as described above. The phospholipid is suspended in the c solvent by stirring. Any solvent that dissolves f phospholipid may be used in accordance with the present invention, such as chloroform or methanol. Alternatively the pre-treatment by immersion in the dissolved phospholipid may involve the gross deposition of phospholipid from a solution with a low degree of supersaturation. The ultrasonication of the coated

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surface orientates and consolidates the phospholipid that c l was deposited on the surface to be coated from the it. solution.

wn ol/nn7d~ PCr/AU90/00292 WO 91/00iI745 C/I9/09 5 The slow deposition of the phospholipid from the solution with a low degree of supersaturation onto the surface to be coated enables the phosphol..pid to be deposited with a better orientation and thus gives an effective coating.

Surprisingly, the methods of the present invention enable the rapid and successful coating of surfaces with phospholipid. As such, in one application the methods may be used to coat the surfaces of medical instruments, thereby making the surfaces non-thrombogenic.

The present invention is particularly applicable for the production of coated catheters for which the surfactant properties of lubrication and release are ideal. It may also be used to produce pacemakers and prosthetic devices which are less likely to be rejected by the body's immune system. The invention may also be applied to ceramic prosthesis to reduce their permeability.

In addition to the anti-friction properties of the phospholipids the present invention has found that surfaces having phospholipid adhered to them seem to be less likely to generate an antibody response than uncoated materials. Similarly, the formation of blood clots is greatly reduced on such coated surfaces. In this respect it is to be noted that by far the most successful anti-coagulent is heparin which can now be grafted to certain surfaces to render then non-thrombogenic. One of the features of grafted heparin is the number of negative charges which they impart, indicating that they might function by providing a site most conducive to the adsorption of the endogenous surfactants, such as phospholipids, which are then the true interface with blood or other body fluids. When such surfaces are removed they are more hydrophobic than before implantation. Hence it would seem better to proceed directly to the phospholipid surface rather than risk desorption of heparin or adjuvant heparin which inhibits coagulation of the blood in general, causing problems to the surgeon.

i~ rr~u I~ar WO 91/00745 PCT/AU90/00292 -6- MODES FOR CARRYING OUT THE INVENTION The invention will now be described by way of various examples.

EXAMPLE 1 Clean glass rods were placed in a bath of water containing 2% egg lecithin and ultrasonicated in the apparatus for 75 minutes. The glass rods were then allowed to drain for 135 minutes and suspended in 125 ml of blood in a beaker. The blood was kept flowing past the rods by a magnetic stirrer. Uncoated, clean glass rods were used as controls in the same blood at the same speed. At intervals of 30 seconds both sets of rods were checked for build up of coagulated material. Within minutes there was appreciable build up of clotted blood on the control rods whereas those rods coated with phospholipid were clean.

COMPARATIVE EXAMPLE 2 The experiment was repeated by solvent depositing the egg lecithin from a solution in methanol) which was allowed to evaporate for two and a half hours. Although the coated rods initiated less clotting than the uncoated control rods, the incidence of clotting was still markedly more than seen for the rods coated in Example 1.

COMPARATIVE EXAMPLE 3 The experiment was performed by solvent depositing soya lecithin in chloroform. Whilst these rods showed less clotting than the uncoated control rod, they were found to be less effective than the rods of comparative example 1 and markedly less effective than the rods coated using ultrasound.

EXAMPLE 4 The Experiments 2 and 3 were repeated, but the surfaces were allowed to dry before being placed in the bath and ultrasonicated as described in Example 1. The glass rods resulting were placed in blood as described in Example 1. The rods thus treated were clean of blood, amd the incidence of clotting was less than in Example 2 or 3.

It will be obvious to those skilled in the art that ~s I Fb WO 91/00745 PCT/AU90/00292 -7numerous variations and modifications could be made to the method of the present invention as described, with reference to the examples, without departing from the overall scope or spirit of the invention.

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Claims (4)

1. 2. The method according to claim 1 further characterised in that before immersing the surface in the bath the surface is pre-treated by being immersed in a solution of phospholipid dissolved in a solvent, removed from the solution and allowed to dry.
2. 3. The method according to claim 1 wherein the bath contains an aqueous suspension of phospholipid.
3. 4. The method according to claim 1 wherein the phospholipid in lecithin. The method according to claim 2 wherein the solvent is methanol or chloroform.
4. 6. The method of claim 1 wherein the surface is that of a catheter, prosthetic device or a heart pacemaker. J INTERNATIONAL SEARCH REPORT International AppLication No. PCT/AU 90/00292 I. CLASSIFICATION OF SUBJECT MAlTER (if several classification symbols apply, indicate all) 6 According to International Patent Classification or to both National Classification and IP- 5 Int. Cl. A61L 33/00 II. FIELDS SEARCHED Minimum Documentation Searched 7 SClassification System CLassification Symbols IPC A61L 33/00, A61 Keywords: Phospholipid, Lecithin, Biocompatible Non-thrombogenic, Anti-thrombogenic Documentation Searched other than Minimum Documentation to the Extent that sucn Documents are Included in the Fields Searched 8 MEDLINE, BIOSIS III. DOCUMNTS CONSIDERED TO BE RELVA2T 9 Category* Citation of Document, with indication, where appropriate, Relevant to I of the relevant passages 12 Claim No 13 P,Y Biochem. Soc. Trans., Vol. 17, No. 6, published 1989, D. Chapman and (1-4) P.I. Haris "Biomembrane structures. Fourier transform infrared spectroscopy and biomenbrane technology", pages 951-3 P,Y Prog. Clin. Biol. Res., Vol. 292, published 1989, D. Chapman et al. (1-4) "Biomembranes: basic science and future technology" pages 3-12 Y US,A, 4426330 (SEARS) 17 January 1984 (17.01.84) (1-4) Column 3 lines 7-45 and 54-68, Column 4 lines 1-18 SY US,A, 4803075 (WALLACE et al) 7 February 1989 (07.02.89) i (1-4) Column 2 lines 42-68, Column 3 lines 20-68, Column 4 lines 1-7 SY US,A, 4725442 (HAYNES) 16 February 1988 (16.02.88) (1-4) (continued) S Special categories of cited documents: 10 later document published after the international filing date or priority date document defining the general state of the and not in conflict with the application but art which is not considered to be of cited to understand the principle or theory particular relevance underlying the invention earlier document but published on or document of particular relevance; the after the international filing date claimed invention cannot be considered novel document which may throw doubts on priority or cannot be considered to involve an claim(s) or which is cited to establish the inventive step publication date of another citation or document of particular relevance; the other special reason (as specified) claimed invention cannot be considered to document referring to an oral disclosure, involve an inventive step when the document use, exhibition or other means is combined with one or more other such document published prior to the documents, such combination being obvious to international filing date but Later than a person skilled in the art. the priority date claimed document member of the same patent family IV. CERTIFICATION Date of the Actual Completion of the Date of Mailing of this International International Search j Search Report 17 October 1990 (17.10.90) I 20 c~>tb4r- ~o International Searching Authority I Signat A ozed Officer Australian Patent Office I RON EVANS Form PCT/ISA/210 (second sheet) (January 1985) Ii I L~C~k I International Applc.ation No. PCT/ 90/00292 FURTER INFORMATION CONTINUED FROM THE SECOND SHEET Y US,A, 4348329 (CHAPMAN) 7 September 1982 (07.09.82) (1-4) Y WO,A1, 87/02684 (BIOCOMPATIBLES LTD) 7 May 1987 (07.05.87) (1-4) V. OBSERVATIONS WHERE CERTAIN CLAIMS WERE FOUND UNSEARCHABLE 1 This international search report has not been established in respect of certain claims under Article 17(2)(a) for the following reasons: Claim numbers because they relate to subject matter not required to be searched by this Authority, namely: comply with the prescribed requirements to such an extent thatno meaningful international search can be carried out, specifically: Claim numbers because they are dependent claims and are not drafted in accordance with the second and third sentences of PCT Rule 6.4 I VI. OBSERVATIONS WHERE UNITY OF INVENTION IS LACKING 2 This International Searching Authority found multiple inventions in this international application as follows: I I j As all required additional search fees were timely paid by the applicant, this international search report covers all searchable claims of the international application. As only some of the required additional search fees were timely paid by the applicant, this international search report covers only those claims of the international application for which fees were paid, specifically claims: No required additional search fees were timely paid by the applicant. Consequently, this international search report is restricted to the invention first mentioned in the claims; it is covered by claim numbers: 4. As all searchable claims could be searcned without effort justifying an additional fee, the International Searching Authority did not invite payment of any additional fee. Remark on Protest The additional search fees were accompanied by applicant's protest. No protest accompanied the payment of additional search fees. Form PCT/ISA/210 (supplemental sheet (January 1985) 4_ ANNEX TO THE INTERNATIONAL SEARCH REPORT ON INTERIfATIONAL APPLICATION NO. AU 90/-0292 This Annex lists the known publication level patent family members relating to the patent documents cited in the above-mentioned international search report. The Australian Patent Office is in no way liable for these particulars which are merely given for the purpose of information. Patent Document Cited in Search Patent Family Members Report US 4426330 EP 72111 AT 38039 CA 1240692 DE 3474667 EP 118316 JP 59204198 US 4803075 AU 74671/87 EP 251695 JP 63119772 US 4725442 CA 1242645 EP 153926 JP 60501557 WO 8500011 US 4348329 DE 3070993 EP 32622 JP 1158013 WO 8702684 DK 3398/87 EP 247114 GB 8527071 END OF ANNEX