Immobilised biological entities

1. A device having a surface comprising a layered coating wherein the outer coating layer comprises a plurality of cationic hyperbranched polymer molecules characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and (iv) functional end groups, whereby one or more of said functional end groups have an anti-coagulant entity covalently attached thereto, wherein the hyperbranched polymer is a polyamidoamine (PAMAM)dendrimer, wherein the layered coating comprises one or more coating bilayers of cationic polymer and anionic polymer, the innermost layer being a layer of cationic polymer, wherein one or more of the layers of the layered coating other than the outer coating layer comprises a cationic hyperbranched polymer molecule which is a PAMAM dendrimer characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and (iv) functional end groups which are optionally derivatised.

2. A device according to claim 1 wherein the anti-coagulant entities are heparin moieties.

3. A device according to claim 2 wherein the heparin moieties are single point attached to the hyperbranched polymer molecules.

4. A device according to claim 2 , wherein the heparin moieties are attached to the hyperbranched polymer molecules via the reducing end of the heparin moiety.

5. A device according to claim 1 , wherein the hyperbranched polymer has a molecular weight of 25,000 to 200,000 Da.

6. A device according to claim 1 , wherein the hyperbranched polymer molecules are cross-linked to form aggregates of two or more hyperbranched polymer molecules.

7. A device according to claim 1 which is a medical device.

8. A device according to claim 1 wherein the layered coating of the device comprises one or more beneficial agents besides the anti-coagulant entities.

9. A process for the manufacture of a device according to claim 1 , the process comprising, in any order:

i. reacting a plurality of functional end groups of hyperbranched polymer molecules with anti-coagulant entities such that each hyperbranched polymer molecule is covalently linked to a plurality of anti-coagulant entities; and

ii. attaching the hyperbranched polymer molecules to the surface of a device.

10. A non-thrombogenic device which is obtainable by a process comprising:

(a) treating a device to present a surface coating comprising an outer coating layer comprising cationic hyperbranched polymer molecules characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da and (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and bearing functional end groups;

(b) reacting at least one or more of said functional end groups with molecules of an anti-coagulant entity which is functionalized to bear groups which are capable of reacting with the reactive functional groups on the hyperbranched cationic polymer;

thereby to attach the anti-coagulant entity to the hyperbranched cationic polymer, wherein the hyperbranched polymer is a PAMAM dendrimer, wherein the coating comprises one or more coating bilayers of cationic polymer and anionic polymer, the innermost layer being a layer of cationic polymer, wherein one or more of the layers of the layered coating other than the outer coating layer comprises a cationic hyperbranched polymer molecule which is a PAMAM dendrimer characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and (iv) functional end groups which are optionally derivatised.

11. A non-thrombogenic device which is obtainable by a process comprising:

(a) treating a device to present a positively charged polymer surface layer; and

(b) associating with said polymer surface layer functionalized cationic hyperbranched polymer molecules characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da and (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and bearing a multiplicity of negatively charged anti-coagulant entities such as heparin moieties and wherein said functionalized hyperbranched cationic polymer has a net negative charge and is a PAMAM dendrimer, wherein the coating comprises one or more coating bilayers of cationic polymer and anionic polymer, the innermost layer being a layer of cationic polymer, wherein one or more of the layers of the layered coating other than the outer coating layer comprises a cationic hyperbranched polymer molecule which is a PAMAM dendrimer characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and (iv) functional end groups which are optionally derivatised;

or

(a) treating a device to present a negatively charged polymer surface layer;

and

(b) associating with said polymer surface layer functionalized cationic hyperbranched polymer molecules characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da and (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and bearing one or more negatively charged anti-coagulant entities such as heparin moieties and wherein said functionalized hyperbranched polymer has a net positive charge and is a PAMAM dendrimer, wherein the coating comprises one or more coating bilayers of cationic polymer and anionic polymer, the innermost layer being a layer of cationic polymer, wherein one or more of the layers of the layered coating other than the outer coating layer comprises a cationic hyperbranched polymer molecule which is a PAMAM dendrimer characterized by having (i) a core moiety of molecular weight 14-1,000 Da (ii) a total molecular weight of 1,500 to 1,000,000 Da (iii) a ratio of total molecular weight to core moiety molecular weight of at least 80:1 and (iv) functional end groups which are optionally derivatised.

12. A device according to claim 1 , wherein the ratio of total molecular weight to core moiety molecular weight is at least 100:1.