Coating for substrate

1. A substrate with a surface having a hydrophilic coating comprising a cross-linked copolymer of components A and B, and optional components C and D; wherein

component A comprises one or more C 2 -C 16 hydrophilic monomers each bearing one or more alkene and/or alkyne groups;

component B comprises one or more hydrophilic polymers each bearing two or more alkene and/or alkyne groups;

component C, if present, comprises one or more beneficial agents each bearing one or more alkene or alkyne groups; and

component D, if present, comprises one or more low molecular weight cross-linking agents each bearing two or more functional groups independently selected from thiol, alkene and alkyne groups;

wherein the cross-linked copolymer is formed by radical polymerisation involving the alkene and/or alkyne groups of components A, B and C (if present) and involving the functional groups of component D (if present);

wherein the hydrophilic coating optionally comprises component E which comprises one or more beneficial agents, wherein component E does not form a copolymer with components A, B, C (if present) and D (if present);

and wherein the hydrophilic coating is covalently attached to the surface of the substrate.

2. A substrate according to claim 1 , wherein the covalent attachment between the surface of the substrate and the hydrophilic coating is formed via the reaction of surface-bound radicals on the surface of the substrate with a component of the hydrophilic coating, and wherein the surface bound radicals are generated via abstraction of hydrogen atoms from the surface of the substrate.

3. A substrate according to claim 1 , having a first surface priming coating of polydopamine, to which the hydrophilic coating is covalently attached.

4. A substrate according to claim 1 , wherein component A comprises one or more C 2 -C 16 hydrophilic monomers each bearing one or more alkene and/or alkyne groups, and also one or more groups selected from ester, ether, carboxyl, hydroxyl, thiol, sulfonic acid, sulfate, amino, amido, phosphate, keto and aldehyde groups.

5. A substrate according to claim 4 , wherein component A comprises acrylic acid and/or methacrylic acid.

6. A substrate according to claim 1 , wherein component B comprises one or more hydrophilic polymers each bearing two or more alkene and/or alkyne groups, wherein the hydrophilic polymer is independently selected from the group consisting of hyaluronic acid, a hyaluronic acid derivative, poly-N-vinylpyrrolidone, a poly-N-vinylpyrrolidone derivative, a polyether derivative, polyvinylalcohol, and a polyvinylalcohol derivative.

7. A substrate according to claim 6 , wherein component B comprises one or more PEG polymers each bearing two alkene groups.

8. A substrate according to claim 7 wherein component B comprises one or more diacrylate-functionalised PEG polymers.

9. A substrate according to claim 1 , wherein component B comprises one or more hydrophilic polymers each bearing two or more alkene and/or alkyne groups, and wherein each hydrophilic polymer independently has molecular weight of 600-40,000 Da.

10. A substrate according to claim 1 wherein said beneficial agent of component C is an agent having pharmacological activity, a conductive agent or an adhesive agent.

11. A substrate according to claim 10 , wherein the agent having pharmacological activity is an anti-thrombogenic agent, an anti-angiogenic agent, an anti-proliferative agent or an anti-microbial agent.

12. A substrate according to claim 1 , wherein component D comprises one or more low molecular weight cross-linking agents each bearing two or more thiol groups.

13. A substrate according to claim 1 , wherein said beneficial agent of component E is an agent having pharmacological activity, a conductive agent or an adhesive agent, wherein the agent having pharmacological activity is an anti-thrombogenic agent, an anti-angiogenic agent, an anti-proliferative agent or an anti-microbial agent.

14. A substrate according to claim 1 , wherein the hydrophilic coating is lubricious and has a lubricity of <100 g, using the Lubricity Test.

15. A substrate according to claim 14 , wherein the hydrophilic coating has durability of <50 g, using the Durability Test.

16. A substrate according to claim 1 , wherein the substrate is a medical device.

17. A method of forming a hydrophilic coating which is covalently attached to the surface of a substrate; wherein said method comprises the steps of:

(a) contacting the surface with a mixture comprising components A and B, optional component C, optional component D and a radical initiator; wherein

component A comprises one or more C 2 -C 16 hydrophilic monomers each bearing one or more alkene and/or alkyne groups;

component B comprises one or more hydrophilic polymers each bearing two or more alkene and/or alkyne groups;

component C, if present, comprises one or more beneficial agents each bearing one or more alkene or alkyne groups; and

component D, if present, comprises one or more low molecular weight cross-linking agents each bearing two or more functional groups independently selected from thiol, alkene and alkyne groups; and

(b) initiating radical polymerisation involving the alkene and/or alkyne groups of components A, B and C (if present) and involving the functional groups of component D (if present) in order to form a cross-linked copolymer of component A, component B, and optional components C and D; wherein said copolymer is covalently linked to the surface; and

(c) optionally incorporating into the hydrophilic coating a component E which comprises one or more beneficial agents, wherein component E does not form a copolymer with components A, B, C (if present) and D (if present).

18. A method according to claim 17 , wherein the substrate is a substrate having a surface comprising abstractable hydrogen atoms.

19. A method according to claim 17 , wherein component A comprises one or more C 2 -C 16 hydrophilic monomers each bearing one or more alkene and/or alkyne groups, and also one or more groups selected from ester, ether, carboxyl, hydroxyl, thiol, sulfonic acid, sulfate, amino, amido, phosphate, keto and aldehyde groups, and wherein component B comprises one or more hydrophilic polymers each bearing two or more alkene and/or alkyne groups, wherein the hydrophilic polymer is independently selected from the group consisting of hyaluronic acid, a hyaluronic acid derivative, poly-N-vinylpyrrolidone, a poly-N-vinylpyrrolidone derivative, a polyether derivative, polyvinylalcohol, and a polyvinylalcohol derivative.

20. A substrate with a hydrophilic coating obtainable according to the method of claim 17 .

21. A substrate according to claim 1 , wherein the ratio of component B to component A is between 2.5:1 and 0.5:1 w/w.

22. A substrate according to claim 6 , wherein the polyether derivative is polyethylene glycol (PEG), a polyethylene glycol (PEG) derivative, polypropylene glycol (PPG), or a polypropylene glycol (PPG) derivative.

23. A substrate according to claim 8 , wherein the one or more diacrylate-functionalised PEG polymers are of formula (I):

wherein n is 10-50,000 or

are of formula (II):

wherein n is 10-50,000.

24. A substrate according to claim 9 , wherein each hydrophilic polymer independently has a molecular weight of 4,000-16,000 Da.

25. A substrate according to claim 11 , wherein the agent having pharmacological activity is heparin.

26. A method according to claim 19 , wherein component A comprises acrylic acid and/or methacrylic acid and component B comprises one or more PEG polymers each bearing two alkene groups.

27. A method according to claim 19 , wherein the polyether derivative is polyethylene glycol (PEG), a polyethylene glycol (PEG) derivative, polypropylene glycol (PPG) or a polypropylene glycol (PPG) derivative.