RADIOPAQUE POLYMERS

Abstract

A polymer having a backbone comprising a polyhydroxylated polymer cross linked by a C3 to C8 diacid.

Claims

1. A polymer having a backbone comprising a polyhydroxylated polymer cross linked by a C3 to C8 diacid.

2. The polymer according to claim 1, wherein the C3 to C8 diacid is selected from a saturated diacid, a mono unsaturated diacid, and in the case of C6 to C8 unsaturated diacid, a diunsaturated diacid.

3. The polymer according to either of claim 1 or 2, wherein the unsaturated diacid is substituted by a group selected from —OH, ═O and —NH.sub.2.

4. The polymer according to any one of claims 1 to 3, wherein the polymer is cross linked by a C3 to C8 saturated diacid, preferably selected from malonic, succinic and glutaric acids.

5. The polymer according to claim 4, wherein the polymer is cross linked by a C4 or C5 alpha keto acid, preferably alpha ketoglutarate.

6. The polymer according to any one of claims 1 to 3, wherein the polymer is cross linked by a C4 to C6 unsaturated diacid, preferably selected from maleic, fumaric or cis or trans galaconic acids.

7. The polymer according to any of the preceding claims, wherein the cross linking groups are of the formula 1: ##STR00036## wherein * is the point of attachment to the polyhydroxylated polymer; and wherein Q is a group of the formula 1a: ##STR00037## wherein n is 1 to 5, preferably 1,2 or 3; or Q is a C.sub.1-6 alkylene or C.sub.2-6 alkenylene group.

8. A polymer formed by cross-linking a polymer comprising a polyhydroxylated polymer with a compound of the formula II wherein ester links are formed between the polyhydroxylated polymer and the compound of the formula 2; ##STR00038## wherein X is —OH or a suitable leaving group; and Q is a group of the formula Ia ##STR00039## wherein n is wherein n is 1 to 5, preferably 1 to 3; preferably 1 or 2; or Q is a C.sub.1-6 alkylene or C.sub.2-6 alkenylene group, wherein alkylene groups are optionally substituted by —OH or —NH.sub.2.

9. A polymer according to claim 8, wherein the suitable leaving group is selected from imidazolyl, mesylate, tosylate, —O-alkyl, chloride, bromide, fluoride and —O-acyl groups

10. A polymer according to any preceding claim, wherein the polyhydroxylated polymer is or comprises PVA.

11. A polymer according to any preceding claim, wherein the polyhydroxylated polymer is or comprises PVA and comprises cross linking groups of formula 3 which cross link the PVA ##STR00040## wherein Q is a group of the formula 1a ##STR00041## wherein n is wherein n is 1 to 5, preferably 1 to 3; preferably 1 or 2; or Q is a C.sub.1-6 alkylene or C.sub.2-6 alkenylene group, wherein alkylene groups are optionally substituted by —OH or —NH.sub.2.

12. A polymer according to claim 10 or 11, wherein the polyhydroxylated polymer is or comprises PVA and the PVA is cross linked by a C6 to C8 unsaturated diacid which is substituted by a group selected from —OH, ═O and —NH.sub.2.

13. The polymer according to claim 12, wherein the polymer is cross linked by a C4 or C5 alpha keto acid, preferably alpha ketoglutarate.

14. A polymer according to any of claims 10 to 13, wherein the PVA has a weight average molecular weight of 2000 kDa to 180,000 kDa.

15. A polymer according to any of claims 10 to 13, wherein the PVA has a weight average molecular weight of 10,000 MW to 32,000 MW.

16. A polymer according to any of claims 10 to 13, wherein the PVA has a weight average molecular weight of 2,000 kDa to 32,000 kDa.

17. A polymer according to any preceeding claim, wherein the polymer is a hydrogel.

18. A polymer according to any preceding claim, wherein the polymer further comprises an imageable agent.

19. A polymer according to claim 18 wherein the imageable agent is coupled to the polymer.

20. A polymer according to claim 18 or 19, wherein the imageable agent is imageable by X-ray, positron emission imaging, SPECT or magnetic resonance imaging.

21. A polymer according to claim 18, wherein the imageable agent is selected from iodine and bromine.

22. A polymer according to claim 19, wherein the imageable agent comprises an iodinated phenyl group.

23. A polymer according to claim 19 wherein the polymer comprises an iodinated phenyl group wherein the phenyl group additionally comprises one or two additional groups, W, wherein W is independently selected from —OH, —COOH, —SO.sub.3H, —OPO.sub.3H.sub.2, —O—(C.sub.1-4alkyl), —O—(C.sub.1-4alkyl)OH, —O—(C.sub.1-4alkyl)R.sup.2, —O—(C.sub.2H.sub.5O).sub.qR.sup.1 —(C═O)—O—C.sub.1-4alkyl and —O—(C═O)C.sub.1-4alkyl; or W is a zwitterionic group of the formula —BZ; wherein: R.sup.1 is H or C.sub.1-4 alkyl; R.sup.2 is —COOH, —SO.sub.3H, or —OPO.sub.3H.sub.2; preferably —COOH or —SO.sub.3H, q is an integer from 1 to 4; B is a bond, or a straight branched alkanediyl, oxyalkylene, alkylene oxaalkylene, or alkylene (oligooxalkylene) group, optionally containing one or more fluorine substituents; Z is a zwitterionic ammonium, phosphonium, or sulphonium phosphate or phosphonate ester group; and wherein —COOH, —OPO.sub.3H.sub.2, —SO.sub.3H and phenolic —OH maybe in the form of a pharmaceutically acceptable salt.

24. A polymer according to claim 22 or 23, wherein the iodinated phenyl group is coupled to the polymer backbone through an ether, ester, amide, carbonate, carbamate, 1,3 dioxolone or 1,3 dioxane groups; particularly an ether, ester or 1,3 dioxane.

25. A polymer according to any preceding claim, wherein the polymer is ionically charged at pH7.4.

26. A polymer according to any preceding claim, wherein the polymer comprises a covalently bound ionic group which is ionized at pH 7.4.

27. A polymer according claim 25 or 26, in which the ionic group comprises a charged species selected from sulphonate, phosphate, ammonium, phosphonium and carboxylate groups; preferably carboxylate or sulphonate groups.

28. A polymer according claim 25 or 26 wherein the charged group is selected from C.sub.1-6 branched or unbranched alkyl groups, C.sub.2-6 branched or unbranched alkenyl groups or C.sub.5-7aryl or heteroaryl groups, each independently substituted by 1 to 3 groups selected from the group consisting of —COOH, —OPO.sub.3H.sub.2 and —SO.sub.3H.

29. A polymer according claim 25 or 26, in which the ionic group is coupled to the polymer backbone through an ether, ester, amide, carbonate, carbamate, 1,3 dioxolone or 1,3 dioxane groups; particularly an ether, ester or 1,3 dioxane group.

30. A polymer according to claim 25 or 26, wherein the polymer has an overall negative charge.

31. A polymer according to claims 25 to 30, wherein the polymer is electrostatically associated with a drug carrying an opposite charge.

32. A polymer according to any preceding claim in the form of a microparticle or microsphere.

33. A microparticle or microsphere comprising a polymer according to any of claims 1 to 31.

34. A microparticle or microspshere according to either of claim 32 or 33 for use in the embolization of a blood vessel.

35. A pharmaceutical composition comprising one or more microparticles or microspheres according to either of claim 32 or 33 and a pharmaceutically acceptable carrier or diluent.

36. A method of making a biodegradable polymer comprising cross-linking polyhydroxylated polymer with a compound of formula 2 ##STR00042## wherein X is —OH or a suitable leaving group; and wherein Q is a group of the formula 1a: ##STR00043## wherein n is wherein n is 1 to 5; or Q is a C.sub.1-6 alkylene or C.sub.2-6 alkenylene group, wherein alkylene groups are optionally substituted by —OH or —NH.sub.2; to form ester linkages between the polyhydroxylated polymer and the compound of the formula 2 thereby cross linking the polymer.

37. A method according to claim 36, wherein the suitable leaving group is selected from imidazolyl, mesylate, tosylate, —O-alkyl, chloride, bromide, fluoride and —O-acyl groups.

38. A method of making a biodegradable polymer microsphere comprising: providing a first liquid, which is a solvent having dissolved therein (i) a polymer comprising PVA and (ii) a compound of the formula 2; ##STR00044## wherein Q is a group of the formula 1a ##STR00045## wherein n is 1 to 5; or Q is a C.sub.1-6 alkylene or C.sub.2-6 alkenylene group, wherein alkylene groups are optionally substituted by —OH or —NH.sub.2; and X is —OH or a suitable leaving group; providing a second liquid which is immiscible with the first liquid; bringing the first liquid into contact with the second liquid such that the first liquid forms a discontinuous phase within the second liquid; and crosslinking the PVA with the compound of the formula 2 within the discontinuous phase such as to form microspheres.

Description

FIGURES

[0142] FIG. 1 shows degradation of biodegradable polymers measured according to example 6.

[0143] FIG. 2 shows an image of biodegradable polymers (125-300 μm) in dry state (A) hydrated in saline (B) and after catheter delivery (C)

[0144] FIG. 3 shows a microCT image of microspheres prepared according to example 8

[0145] FIG. 4. illustrates drug loading curves for doxorubicin loading of 4 microsphere preparations.

EXAMPLES

Example 1. Synthesis of PVA-alpha-ketoglutarate Degradable Polymers as Microspheres

[0146] PVA (10 kDa Mw, 1.0 g, 0.1 mmol, 1 eq) was dissolved in 1-methyl-2-pyrrolidinone (4 ml) with gentle heating to 90° C. under inert atmosphere, then allowed to cool to room temperature. Alpha-ketoglutaric acid (KGA 0.06 g, 0.42 mmol, 4.2 eq) and 1,1′-carbonyldiimidazole (CDI, 0.15 g, 0.91 mmol, 9.1 eq) were dissolved in 1-methyl-2-pyrrolidinone (2 ml), respectively, followed by mixing the two solution to form an imidazole intermediate over 5 minutes at ambient temperature.

[0147] To a dried 1L round bottom flask, heavy or light mineral oil (500 ml) and surfactant Span20 (6 ml) were mixed with a mechanical stirring under a nitrogen blanket, and the reaction flask was heated to temperature 70° C. The PVA 1-methyl-2-pyrrolidinone solution was mixed with the CDI-activated alpha-ketoglutaric acid solution. The mixture was roller-mixed for about 20 to 30 minutes at ambient temperature. Then the brown coloured solution was added in to the mineral oil solution under a nitrogen blanket and with strong stirring. The suspended micro droplets gradually solidified into microparticles over the course of 1 to 10 hours at 70° C.

[0148] When the reaction stopped, the suspension was allowed to settle, and the mineral oil was aspirated and the resulting micro particles were washed with alkyl acetate (2×500 ml) and ethanol (2×500 ml) in sequence. The washed particles were transferred into saline solution at pH 3 and the swollen microparticles were sieved for the collection of fractions of different size range, 32-70 μm, 70-150 μm, 150-300 μm, 300-500 μm and 500 to 700 μm. The collected microparticles were placed into acetone to remove water, followed by vacuum drying at ambient temperature for 24 hour. Element analysis results showed that the nitrogen level of the dry microparticles was not detectable from the background, which is indicative of a clean wash of imidazole, a by-product. The microparticles were gamma-sterilized using a dose of 25 kGy.

##STR00021##

Example 2. Synthesis of Biodegradable PVA-Fumaric Acid Polymers

[0149] PVA (10 kDa Mw, 1.0 g, 0.1 mmol, 1 eq) was dissolved in 1-methyl-2-pyrrolidinone (4 ml) with gentle heating under inert atmosphere. Fumaric acid (0.08 g, 0.7 mmol) and 1,1′-carbonyldiimidazole (CDI, 0.22 g, 1.4 mmol) were dissolved in DMSO (2 ml), respectively, followed by mixing the two solutions to form an imidazole intermediate over 10 minutes at ambient temperature.

[0150] To a dried 1L round bottom flask, heavy or light mineral oil (500 ml) and surfactant Span20 (6 ml) were mixed with a mechanical stirring under a nitrogen blanket, and the reaction flask was heated to temperature 70° C. The PVA 1-methyl-2-pyrrolidinone solution was mixed with the CDI-activated fumaric acid solution. The mixture was roller-mixed for about 20 to 30 minutes at ambient temperature. Then the brown coloured solution was added in to the mineral oil solution under a nitrogen blanket and with strong stirring. The suspended micro droplets gradually solidified into microparticles over the course of 15 hours at 70° C.

[0151] The work up of the fumaric acid cross-linked beads was the same as in Example 1.

Example 3. Synthesis of PVA-Succinic Acid Biodegradable Polymers

[0152] PVA (10 kDa Mw, 1.0 g, 0.1 mmol, 1 eq) was dissolved in 1-methyl-2-pyrrolidinone (5 ml) with gentle heating under inert atmosphere. Succinic acid (0.08 g, 0.7 mmol) and 1,1′-carbonyldiimidazole (CDI, 0.24 g, 1.5 mmol) were dissolved in 1-methyl-2-pyrrolidinone (2 ml), respectively, followed by mixing the two solutions to form an imidazole intermediate over 5 minutes at ambient temperature.

[0153] To a dried 1 L round bottom flask, heavy or light mineral oil (500 mL) and surfactant Span20 (6 mL) were mixed with a mechanical stirring under a nitrogen blanket, and the reaction flask was heated to temperature 70° C. The PVA 1-methyl-2-pyrrolidinone solution was mixed with the CDI-activated succinic acid solution. The mixture was roller-mixed for about 20 to 30 minutes at ambient temperature. Then the mixture was added into the mineral oil solution under a nitrogen blanket with strong stirring at about 300 rpm. The suspended micro droplets gradually solidified into microparticles over the course of 2 to 10 hours at 70° C. The work up of the fumaric acid cross-linked beads was the same as in Example 1.

Example 4. Synthesis of Biodegradable PVA-KGA Polymers with High PVA Solid Content

[0154] Following the example 1, PVA (Mw 10 kDa, 1.50 g, 0.15 mmol, 1 eq) α-Ketoglutaric acid (0.15 g), 1,1′-Carbonyldiimidazole (0.38 g), were used to synthesis microparticles in heavy mineral oil 500 mL. Span 20 was used to stabilise the suspended droplets. The reaction was carried out at 70° C. for 15 hours, and the micrparticles generated were processed as per example 1.

Example 5. Synthesis Biodegradable PVA-KGA Polymers with 3 kDa PVA

[0155] Following the procedure in Example 1, PVA (3 kDa Mw, 1.00 g, 0.10 mmol, 1 eq) a-Ketoglutaric acid (0.10 g, 0.7 mmol, 7 eq), 1,1′-Carbonyldiimidazole (0.25 g, 1.5 mmol, 15.5 eq), were used to synthesize biodegradable microparticles in heavy mineral oil. Span 20 was used to stabilise the suspended droplets. The reaction was carried out at 70° C. for 2 to 15 hours, and the microparticles generated were processed as the example 1.

Example 6. Polymer Degradation Study

[0156] Three groups of 0.1 g of dry microparticles of size range 60 to 300 um were pre-weighed and placed into 100 mL of Phosphate Buffered Saline (PBS: NaCl 136.7 mM, KCl2.7 mM, Na2HPO4 10.1 mM, KH2PO4 1.7 mM) in a Duran® bottle (pH 7.4, in each group n=3). The microparticles in PBS were incubated at 37° C. with occasional agitation. Microparticles were periodically collected by filtration using a 40 um sieve, vacuum dried and weighed. The filtered solution was analysed by Gel Permeation Chromatography directly. A sample of raw material of PVA polymer used for microparticle synthesis was also analysed a as control. The Gel Permeation Chromatography of the samples were compared to PEG standards and PVA reference to determine the molecular weight and distribution of the degradation product. The weight change of the microparticles during degradation are shown in FIG. 1.

Example 7. Solid content, Suspension and Catheter Delivery Test

[0157] The solid content of biodegradable microparticles (PVA-KGA 8%) were tested with four size ranges 32 to 70 μm, 70 to 125 μm, 125 to 300 μm and 300 to 500 μm. The test was carried out by accurately weighing the dry microparticles, followed by saline hydration of the microparticles to saturation. To obtain the weights of hydrated microparticles, extra saline was removed by pipetting and tissue wicking. The solid content of the microparticles are listed in the Table 1.

TABLE-US-00001 TABLE 1 Solid content of hydrated microparticles Microparticle Solid content size range (% w/w) 32-70 μm  7.4 ± 0.7 70-125 μm 11.8 ± 0.2 125-300 μm 12.5 ± 1.2 300-500 μm 11.8 ± 0.8

[0158] Table 2 illustrates the effect of various KGA levels on the solid content of microspheres prepared according to the above examples

TABLE-US-00002 TABLE 2 Solid content (% w/w) of hydrated microparticles with varying KGA content. KGA level in beads 75-125 μm 125-300 μm 500-700 μm  6.5% 6.06 ± 0.94  6.61 ± 0.23  7.88 ± 0.61  8.0% 7.95 ± 1.26  7.81 ± 0.17 11.11 ± 0.31 10.0% 8.09 ± 0.79 10.14 ± 0.38 12.73 ± 0.21

[0159] For the suspension test, 50 mg dry microparticles were hydrated in 5 mL of saline and mixed with contrast medium, Omnipaque 350, to achieve stable suspensions over the course of 5 minutes. An optimal ratio of Omnipaque 350: saline was found around 4-5:5 (v/v, mL). Catheter delivery of the microparticles was carried out by injecting the microparticles suspension through a 2.4 Fr Progreat catheter. All four size ranges were delivered through the catheter without blockage. The ease of delivery of the microparticles increased with decreasing microparticle size, i.e. the 32 to 70 μm size range were the easiest to deliver, followed by 70 to 125 μm microparticles, 125 to 300 μm microparticles and 300 to 500 μm microparticles. After delivery, microscope images showed no evidence of microparticle damage.

Example 8. General Protocol for Coupling Iodinated Phenyl Aldehydes and Aldehyde Derivatives to PVA

[0160] To a pre-dried reactor under a nitrogen blanket is added PVA (typically 5-10 g) and anhydrous solvent (typically DMSO or NMP, 40 vol w.r.t. PVA mass) and catalyst (typically 2.2 vol w.r.t. PVA mass. eg methanesulphonic acid). The stirred suspension is heated to elevated temperature (ca 90° C.) to dissolve the PVA. When a homogeneous solution had been obtained, the mixture is cooled to the desired reaction temperature (typically 50-80° C.) the desired aldehyde substrate for the first and second pendant groups (typically 0.01 to 0.6 eq PVA diol functionalities) are added. The actual ratio of first and second pendant group aldehyde substrate to PVA 1,3-diol groups, and the ratio of first to second pendant groups, will depend on the tuning of hydrophilic to hydrophobic nature of the polymer required, but typically the first pendant group will be at a higher ratio than the second.

[0161] The reaction is then stirred under an N.sub.2 blanket and the reaction conversion is monitored by HPLC for consumption of substrate. At a pre-determined time (typically when consumption of the substrate has ceased) an anti-solvent is added (typically, acetone, DCM, MeCN or TBME, ca 40 vol) dropwise from a dropping funnel. The supernatant fluid is removed by aspiration through a filter membrane and further reaction solvent (typically 40 vol) is charged and stirred until the solids had fully dissolved. This solvent washing stage is repeated up to 3 times. Then the solid is re-dissolved in reaction solvent, and precipitated by the slow addition of water (typically up to 100 vol). The resulting aggregated solid is removed from the supernatant and homogenised in a blender in water. The suspension is filtered and re-suspended in water (typically 100 vol), slurried for up to 30 minutes and filtered. The water slurrying is repeated until pH neutral had been obtained, then the damp solids are slurried in acetone (100 vol, 30 mins stir, 2 repetitions), filtered and dried in a high vacuum oven at 30° C. for up to 24 hours.

Example 9. Coupling of 5-((2,2-Dimethoxyethyl)amino)-2,4,6-triiodo-isophthalic Acid

[0162] ##STR00022##

[0163] To a flame dried 500 ml rbf under nitrogen, was added solid 5-amino-2,4,6-triiodoisophthalic acid (46.95 g, 84.03 mmol, 1.0 eq), sodium bicarbonate (28.21 g, 335.8 mmol, 4.0 eq) and DMF (ca 400 ml) via cannula. To the resulting brown solution was added 2-bromo-1,1-dimethoxyethane (13 ml, 110.0 mmol, 1.3 eq) dropwise and the resulting solution heated to reflux for 18 h. After cooling to room temperature, the majority of DMF was removed by rotary evaporation under vacuum (9 mBar, 55° C.) and the resulting orange solid extracted with ethyl acetate (1L). This suspension was washed with saturated lithium chloride solution (7×400 ml) to remove residual DMF and salts, dried over magnesium sulfate, filtered and evaporated to dryness. The resulting solid was recrystallised from ethyl acetate, washed with i-hexane and filtered. This process was repeated a total of 3 times and the resulting orange solid dried under high vacuum to give the title compound (33.04 g, 61%, 91.7% HPLC purity). The product could be further purified via silica gel column chromatography (MeOH in DCM, 0-15%) (4.91 g, 82% yield, 96% HPLC purity); δ.sub.H (CDCl.sub.3, 500.1 MHz)/ppm; 8.01 (1H, s), 4.86 (2H, br s), 4.76 (1H, t, 5.5 Hz), 4.37 (2H, d, 5.5 Hz), 3.44 (6H, s); δ.sub.C NMR (CDCl.sub.3, 125.8 MHz)/ppm;

[0164] Dried microparticles prepared according to example 1(0.50 g) of various sizes, were added into a stirred solution of N,N-dimethylformamide (40 mL) to allow the microparticles to swell. Catalyst methane sulfonic acid (2.2 mL) and 5-((2,2-dimethoxyethyl)amino)-2,4,6-triiodoisophthalic acid (7.46 g, 11.5 mmol) were added into the reaction vessel. The temperature was raised to 70° C. under an inert atmosphere for 24 hours. After cooling to room temperature (approximately 15° C. to 25° C.), the microparticles were aspirated and then washed with dimethyl formamide (3×40 ml), ethanol (2×50 ml) and acetone (3×50 ml), respectively. After removing acetone, the microparticles were dried under vacuum at ambient temperature for 18 hours.

##STR00023##

[0165] The radiodensity of these microspheres was determined according to example 13 to be 6288±450 HU. The microspheres were suspended in contrast medium and saline mixture (2:0.5-2:1, v/v) in about 1 minute. The beads were successfully delivered through 2.4 Fr Progreat catheter.

[0166] FIG. 3 shows a microCT image of these microsphere.

Example 10. Synthesis of Polymers with Sulfonated and Iodinated Phenyl Group: Synthesis of 3-(3-formyl-2,4,6-triiodophenoxy)propane-1-sulfonate and 3-(1-formyl-3,4,5-triiodophenoxy)propane-1-sulfonate, Sodium Salt

[0167] ##STR00024##

[0168] In a 150 mL three-neck round bottom flask, 3-hydroxy-2,4,6-triiodobenzaldehyde (10 g, 20 mmol) was dissolved in 50 mL anhydrous Tetrahydrofuran (THF) by magnetic stirrer. 2.47 g (22 mmol) of potassium t-butoxide was mixed with 20 mL of THF and the suspension was added slowly into the flask under nitrogen atmosphere at room temperature, followed by increasing temperature to 40° C. to allow a fully dissolution of product. Then 15 g (120 mmol) of sultone was dissolved in 15 mL of THF and the mixture was added slowly to the reaction flask. A precipitation appeared almost immediately. After 3 hr reaction at 40° C., the reaction mixture were poured into 500 mL of ethyl acetate to receive solid raw product. The filtered solid was washed with 100 mL of ethyl acetate, and recrystallized in ethanol. After vacuum drying over 24 hr, 10.7 g product was received with 80% yield. SulfoTIBA proton Nuclear Magnetic Resonance (NMR) analysis, D.sub.2O solvent: δ (ppm) 2.24-2.34 (m, 2H), 3.12-3.25 (t, 2H), 3.88-4.02 (t, 2H), 8.18-8.25 (s, 1H), 9.42-9.50 (s, 1H). Element analysis result: C18.56, H 2.22, S 5.66, I 52.31, K 6.27. Cal: C 18.20, H 1.22, S 4.85, I 57.68, K 5.92.

[0169] 3-(1-formyl-3,4,5-triiodophenoxy)propane-1-sulfonate, sodium salt was synthesized analogously from 3,4,5-triiodosalicylaldehyde (see example 19).

[0170] PVA Modification with Sodium 3-(3-formyl-2,4,6-triiodophenoxy)propane-1-sulfonate (STIBA)

[0171] 6.56 g of STIBA and 3.98 g of PVA (Mw 10 kDa) were dissolved into 40 mL of Dimethyl sulfoxide (DMSO) in a reaction flask. Catalyst methyl sulfonic acid 8.8 mL was mixed with 20 mL of DMSO and added into the flask. After 24 hours reaction at 60° C., the reaction mixture was precipitated twice in 900 mL of acetone with stirring. The collected solid was dissolved in deionised water and placed in a dialysis bag (MWCO: 1000). The polymer was dialysed against water for three days to remove small molecular impurities, followed by freeze-drying with 1.55 gram of polymer received.

[0172] 3-(1-formyl-3,4,5-triiodophenoxy)propane-1-sulfonate prepared as above, may be coupled to PVA in an analogous manner. 2-sulfobenzaldehyde sodium salt, (Sigma Aldrich UK), 4-formylbenzene 1,3 disulfonic acid disodium-salt, (Sigma Aldrich UK), and 4-formylbenzoic acid (Sigma Aldrich UK) may also be coupled to PVA by using an analogous synthetic route.

[0173] Bead synthesis by using KGA cross-linker followed the same procedure in Example 1.

[0174] The STIBA-modified PVA obtained above was dissolved into 1-methyl-2-pyrrolidinone (5 mL). Alpha-ketoglutaric acid (0.06 g, 0.42 mmol) and 1,1′-carbonyldiimidazole (CDI, 0.15 g, 0.91 mmol) are dissolved in 2 mL 1-methyl-2-pyrrolidinone (2 mL), respectively, followed by mixing the two solution to form an imidazole intermediate over 5 minutes at ambient temperature. The PVA solution was then mixed with the CDI-activated alpha-ketoglutaric acid solution, followed by mixing with 500 mL of mineral oil and surfactant Span20 at 70° C. under mechanical stirring at 300 rpm. The suspended microdropletes gradually solidified into micro particles overnight. The received beads were then washed with ethyl acetate and ethanol to remove residual oil and reactants. The beads were vacuum dried.

##STR00025##

Example 11. Biodegradable Polymers with Pendant Carboxyl Groups

[0175] 0.5 g of PVA microparticles prepared according to example 1 were dispersed into 35 mL of Dimethylformamide (DMF), followed by addition of cis-aconitic anhydride (0.442 g, 2.8 mmol) and triethylamine (0.525 ml, 3.8 m mol.). Reaction temperature was kept at 60° C. and stirred at 350 rpm for 24 h. After the reaction stopped, the microparticles were washed with 30 mL of DMF and PBS, followed by acetone washing. The microparticles were then vacuum dried overnight at room temperature (approximately 15° C. to 25° C.).

##STR00026##

Example 12. Biodegradable Polymers with Pendant Sulphonyl Groups

[0176] 0.5 g of PVA microparticles were dispersed into 35 mL DMF, followed by adding chlorosulfoacetyl chloride (1.00 g, 5.6 mmol) and Triethylamine (1.65 ml, 11.8 mmol). Reaction temperature was kept at 60° C. and the reaction mixture was stirred at 350 rpm for 24 hours. After the reaction stopped, the microparticles were washed with 30 mL of DMF and PBS to remove residual reactant. The microparticles were further processed by washing with acetone and following that vacuum drying.

##STR00027##

Example 13. Microspheres with Pendant Propionic Acid Groups

[0177] Crosslinked PVA microparticles are dispersed into 35 mL DMF, 3,3-dimethoxy propionic acid and methanesulfonic acid is added to react with the diol groups on the polymers. The microparticles are aspirated and then washed with dimethyl formamide, ethanol and acetone, respectively. After removing the acetone, the microparticles are dried under vacuum at ambient temperature.

Example 14. Radiodensity Determinations

[0178] Micro-CT was used to evaluate the radiopacity (radiodensity) of samples of radiopaque embolic beads prepared according to general example 8 above. The samples were prepared in Nunc cryotube vials (Sigma-Aldrich product code V7634, 48 mm×12.5 mm). The beads were suspended in 1% agarose gel (prepared with Sigma-Aldrich product code A9539). The resulting suspension is generally referred to as a “Bead Phantom”. To prepare these bead phantoms, a solution of agarose (1%) is first raised to a temperature of approximately 50° C. A known amount of the beads is then added, and the two gently mixed together until the solution starts to solidify or gel. As the solution cools it gels and the beads remain evenly dispersed and suspended within the agarose gel.

[0179] Bead phantoms were tested for radiopacity using micro-Computer Tomography (Micro-CT) using a Bruker Skyscan 1172 Micro-CT scanner at the RSSL Laboratories, Reading, Berkshire, UK, fitted with a tungsten anode. Each phantom was analysed using the same instrument configuration with a tungsten anode operating at a voltage of 64 kV and a current of 155 μA. An aluminium filter (500 μm) was used.

TABLE-US-00003 TABLE 1 Acquisition parameters: SkyScan1172 Version 1.5 (build Software: 14) NRecon version 1.6.9.6 CT Analyser version 1.13.1.1 Source Type: 10 Mp Hamamatsu 100/250 Camera Resolution (pixel): 4000 × 2096 Camera Binning. 1 × 1 Source Voltage 65 kV Source Current uA 153 Image Pixel Size (um): 3.96 Filter A1 0.5 mm Rotation Step (deg) 0.280 Output Format 8 bit BMP Dynamic Range 0.000-0.140 Smoothing 0 Beam Hardening 0 Post Alignment corrected Ring Artefacts 16
A small amount of purified MilliQ® water was carefully decanted into each sample tube. Each sample was then analysed by X-Ray micro-computer tomography using a single scan, to include the water reference and the beads. The samples were then reconstructed using NRecon and calibrated against a volume of interest (VOI) of the purified water reference. A region of interest (ROI) of air and water was analysed after calibration to verify the Hounsfield calibration.
Radiodensity was reported in Hounsfield units from line scan projections across the bead. Values used for dynamic range for all samples in NRecon (thresholding): −0.005, 0.13 (minimum and maximum attenuation coefficient). The microspheres from example 5 measured according to this general protocol had a radiodensity of 6288±450 HU. The beads were suspended in contrast medium and saline mixture (2:0.5-2:1, v/v) in about 1 minute. The beads were successfully delivered through 2.4 Fr Progreat catheter.

Example 15: Synthesis of 3,5-Diiodo-2-(2-(2-methoxyethoxy) ethoxy) Benzaldehyde

[0180] ##STR00028##

[0181] To a HEL PolyBlock8 parallel synthesis 125 ml reactor fitted with a reflux condenser and suspended magnetic stirrer, was added 3,5-diiodosalicylaldehyde (13.9011 g, 37.72 mmol, 1.0 eq) and TBAI (2.7481 mg, 0.802 mmol, 0.2 eq). To this was added water and the pH adjusted to 9.5 with 1M NaOH (total aqueous volume 97 ml). The reactor was set to 500 rpm stirring until full dissolution to give a bright yellow solution and 1-bromo-2-(2-methoxyethoxy)ethane (5.00 ml, 37.17 mmol, 1.0 eq) was added. The reactor zone was set to heat to 120° C. The reaction was monitored by TLC (30% EA in i-hex) and after 2 h additional bromide was added (2.50 ml, 18.59 mmol, 0.5 eq). After a further 0.5 h, the pH was readjusted to 9.5 due to consumption of the bromide. After a further 2 h additional bromide (1.25 ml, 9.29 mmol, 0.25 eq) were added and the reactor turned down to 50° C. and left to stir overnight. After 19h, the resulting suspension was reheated to reflux for 1 h, cooled to RT and transferred to a separating funnel in ethyl acetate (400 ml). The organics were washed twice with sat. sodium bicarbonate, dried with magnesium sulfate, hot filtered from toluene, and recrystallised from toluene/isohexane to give, after filtration and hi-vacuum drying, the desired product as a yellow powder (15.2909 g, 86.4% yield); δ.sub.H (CDCl.sub.3, 500.1 MHz)/ppm; 10.31 (1H, s), 8.31 (1H, d, 2.2Hz), 8.09 (1H, d, 2.2Hz), 4.26 (2H, app. t, 4.5 Hz), 3.89 (2H, app. t, 4.5 Hz), 3.67 (2H, app. t, 4.6 Hz), 3.55 (2H, app. t, 4.6 Hz), 3.38 (3H, s); δ.sub.C NMR (CDCl.sub.3, 125.8 MHz)/ppm; 188.71 (CH), 161.55 (q), 152.43 (CH), 137.57 (CH), 131.75 (q), 94.07 (q), 89.19 (q), 75,56 (CH2), 71.90 (CH2), 70.79 (CH2), 70.06 (CH2), 59.13 (CH3).

Example 16: Synthesis of 3-Hydroxy-2,4,6-triiodobenzaldehyde

[0182] ##STR00029##

[0183] To a 2L 3-necked rbf with large oval stirrer bar was added 3-hydroxybenzaldehyde (10.007 g, 81.89 mmol), sodium iodide (0.614 g, 4.09 mmol, 0.05 eq) and sodium carbonate (93.028 g, 877.44 mmol, 10.7 eq), rinsed in with a total of 750 ml of DI water. When the benzaldehyde had dissolved to give a bright yellow stirred solution, iodine balls (70.008 g, 275.80 mmol, 3.37 eq) was added in 2 portions over 30 minutes rinsed in with 225 ml of water each time. The reaction is followed by TLC (60% DCM in i-hex) and over 3 h, the iodine almost completely dissolves resulting in a dark yellow/orange precipitate. The solid was isolated by Büchner filtration and washed with i-hexane to remove any residual iodine. The isolated solid was re-dissolved in warm water (2L, 45° C.) to give a clear brown solution to which 100 ml of sat. sodium thiosulfate solution were added to reduce any remaining iodine. The pH of the solution was cautiously reduced from 10.2 to 3.26 using 1M HCl (care due to evolution of CO.sub.2). The solid was isolated by filtration, washed with water (2×500 ml) and dried in a high vacuum oven at 30° C. to give the desired compound as a yellow solid (37.002 g, 90.3% yield, 97.2% HPLC purity); δ.sub.H (CDCl.sub.3, 500.1 MHz)/ppm; 9.65 (1H, s), 8.35 (1H, s), 6.42 (1H, s); δ.sub.C NMR (CDCl.sub.3, 125.8 MHz)/ppm; 194.90 (CH), 155.12 (q), 149.77 (CH), 135.69 (q), 88.78 (q), 87.66 (q), 85.70 (q).

Example 17: Synthesis of 2,4,6-triiodo-3-(2-(2-methoxyethoxy)ethoxy)benz Aldehyde

[0184] ##STR00030##

[0185] To a flame dried 250 ml 3-necked rbf under a nitrogen atmosphere containing a stir bar and fitted with a reflux condenser, were added 3-hydroxy-2,4,6-triiodobenzaldehyde (15.627 g, 31.3 mmol, 1.0 eq), sodium iodide (469 mg, 3.13 mmol, 0.1 eq), anhydrous sodium carbonate (3.981 g, 37.6 mmol, 1.2 eq) and anhydrous DMF (160 ml). The suspension was stirred until the aldehyde had completely dissolved, then 1-bromo-2-(2-methoxyethoxy)ethane (6.87 g, 37.5 mmol, 1.2 eq) was added by syringe and the reaction heated to reflux. After 2 h, TLC analysis (10% EA in i-hex) indicated the SM was consumed and the reaction was cooled to RT, transferred to a 250 ml rbf and evaporated to dryness under high vacuum. The resulting suspension was diluted with 500 ml of ethyl acetate, washed with 3×100 ml 1M NaOH, 2×100 ml sat. brine, decolourised with activated charcoal and dried with magnesium sulfate. The resulting solution was concentrated to dryness, and purified by silica column chromatography (2-20% ethyl acetate in i-hexane) and dried under high vacuum to give the desired compound as a yellow powder (7.556 g, 40.1%); δ.sub.H (CDCl.sub.3, 500.1 MHz)/ppm; 9.65 (1H, s), 8.44 (1H, s), 4.20 (2H, t, 6.4 Hz), 4.01 (2H, t, 6.4 Hz), 3.79 (2H, app. t, 5.8 Hz), 3.60 (2H, app. t, 5.8 H), 3.41 (3H, s); δ.sub.C NMR (CDCl.sub.3, 125.8 MHz)/ppm; 194.97 (CH), 159.10 (q), 150.83 (CH), 138.27 (q), 97.06 (q), 95.70 (q), 90.40 (q), 72.47 (CH2), 72.04 (CH2), 70.89 (CH2), 68.89 (CH2), 59.19 (CH3).

Example 18: Synthesis of 2,4,6-Triiodo-3-(2-(2-(2-methoxyethoxy)ethoxy) ethoxy)benz Aldehyde

[0186] ##STR00031##

[0187] To a flame dried 100 ml 3-necked rbf containing a stirrer under a nitrogen blanket, was added triphenylphosphine (1.7216 g, 6.502 mmol, 1.3 eq) and anhydrous THF (35 ml). The stirring was started and, after full dissolution of the PPh3, the reactor was cooled to ca 0° C. in an ice-bath. To the colourless solution was added DIAD (1.28 ml, 6.502 mmol, 1.3 eq) dropwise via syringe resulting in a persistent yellow solution. After stirring for 5 minutes, triethylene glycol monomethyl ether (1.04 ml, 6.502 mmol, 1.3 eq) was added dropwise by syringe. After stirring for a further 5 minutes, the 3-hydroxy-2,4,6-triiodobenzaldehyde (2.5077 g, 5.002 mmol, 1.0 eq) was added in one portion resulting in an immediate colour change. The reaction was monitored by TLC (5% Et.sub.2O in toluene) and left to stir overnight. The solution was diluted with ether to precipitate triphenylphosphine oxide and then concentrated to dryness. The resulting thick oil was purified by column chromatography (2-10% Et.sub.2O in toluene) to give, after concentration and high vacuum drying, the desired product as a yellow powder (3.2077 g, 99% yield, 94.4% HPLC purity); δ.sub.H (DMSO-D.sub.6, 500.1 MHz)/ppm; 9.58 (1H, s), 8.47 (1H, s), 4.08 (2H, t, 4.9 Hz), 3.57-3.53 (4H, m), 3.44 (2H, app. t, 4.8 Hz), 3.24 (3H, s).

Example 19: Synthesis of 3,4,5-Triiodosalicylaldehyde

[0188] ##STR00032##

[0189] To a 3-necked 2L rbf containing a large oval stirrer was added 4-iodo-salicilaldehyde (25.01 g, 100.86 mmol, 1.0 eq) and acetic acid (300 ml). After stirring for 5 mins to allow the solid to dissolve, pre-warmed liquid iodine monochloride (39.11 g, 2.4 eq) was diluted with AcOH (100 ml) and transferred to a dropping funnel on the rbf. This solution was added over 10 mins. The reactor was then placed in a large silicone oil batch a fitted with a 1L dropping funnel, thermometer and condenser and set to heat to 80° C. During the heat up, water (700 ml) was slowly added to the solution causing a yellow/orange precipitation. After 20 mins at 80° C., the heating was turned off. After a further the heating bath was removed and the black solution/yellow suspension allowed to cool to RT and stir for 65 h; the reaction was analysed by TLC (20% EA in iHex). The solid was isolated by Büchner filtration and washed with water (2×500 ml). To remove residual iodine crystals, the solid was repeatedly re-slurried with i-hexane (200 ml) until the i-hexane supernatant was no longer purple. The isolated solid was dried in a hi-vac oven overnight to give the desired product as a yellow crystalline solid (40.84 g, 81% yield, 93.2% pure by HPLC analysis). The product could be further recrystallised to higher purity from acetone:water (9:1); δ.sub.H (CDCl.sub.3, 500.1 MHz)/ppm; 12.15 (1H, s), 9.67 (1H, s), 8.09 (1H, s); δ.sub.C NMR (CDCl.sub.3, 125.8 MHz)/ppm; 194.53 (CH), 159.58 (C), 142.24 (CH), 133.39 (C), 120.87 (C), 101.68 (C), 94.02 (C).

Example 20: Synthesis of 3,4,5-Triiodo-2-(2-(2-methoxyethoxy)ethoxy) Benzaldehyde

[0190] ##STR00033##

[0191] (5 g scale): To a flame dried 3-necked 250 ml rbf containing a small octagonal stirrer bar under a positive pressure of nitrogen, was added triphenylphosphine (2.76 g, 10.5 mmol, 1.05 eq) and dry THF (70 ml) by syringe. The rbf was placed in a Dewer bath fitted with a low temperature thermometer and cooled to −68° C. with an EtOH/liquid nitrogen bath. Diethyl azodicarboxylate (1.65 ml, 10.5 mmol, 1.05 eq) was added dropwise by syringe over 1 min and left to stir for 5 mins to give a yellow suspension. Diethyleneglycol mono-methyl ether (1.77 ml, 15 mmol, 1.5 eq) was then added dropwise and left to stir for 5 mins. To this was added solid 3,4,5-triiodosalicylaldehyde (5.00 g, 10.0 mmol, 1.0 eq) in one portion. The initial dark orange/red suspension lightened to give a pale yellow solution which was allowed to stir for 2 h, monitored by TLC analysis (20% ether in toluene) and left to warm up to RT O/N. TLC indicated complete consumption of aldehyde starting material with a clean reaction profile. The resulting solution was transferred to a 500 ml rbf, diluted with ether (200 ml) and cooled in the freezer. The resulting suspension was filtered through a short silica plug to remove triphenylphosphine oxide and flushed with further ether (200 ml). The resulting solution was concentrated to dryness, and purified by column chromatography eluting with ether in toluene (2-20%) with product fractions concentrated to dryness and dried under high vacuum to give the desired product as a yellow amorphous solid (4.91 g, 82% yield, 96% HPLC purity); δ.sub.H (CDCl.sub.3, 500.1 MHz)/ppm; 10.26 (1H, s), 8.34 (1H, s), 4.22 (2H, t, 4.5 Hz), 3.90 (2H, t, 4.5 Hz), 3.90 (2H, t, 4.6 Hz), 3.55 (2H, t, 4.6 Hz), 3.38 (3H, s); δ.sub.C NMR (CDCl.sub.3, 125.8 MHz)/ppm;

Example 21. Biodegradable Polymers with Ether Bonded Carboxylic Acid Drug Binding Species

[0192] 1.0 g of PVA powder (10 kDa) is dissolved into 35 mL of 1-methyl-2-pyrrolidinone at 90° C. The temperature is then lowered to 50° C., followed by addition of 3-bromopropionic acid (0.42 g, 2.7 mmol) and sodium hydroxide powder (0.22 g, 5.4 mmol.). Reaction temperature is maintained at 50° C. and stirring continues at 350 rpm overnight. After the reaction has stopped, the solution is added dropwise into acetone (200 ml) to precipitate out the polymer. The polymer solid is then washed with methanol (100 ml) to remove the sodium hydroxide and the polymer dried under vacuum (24 hours). Following Example 1, biodegradable beads are then synthesized using the functionalized PVA polymer.

##STR00034##

Example 22. Biodegradable Polymers with Ester Bonded Radiopaque Groups

[0193] 2,3,5-Triiodobenzoic acid (5 g, 10 mmol) is dissolved in 25 ml NMP in a 100 mL three necked round bottom flask. Thionyl chloride (1.3 g, 11 mmol) is diluted into 5 ml NMP solution and added into the reaction vessel. The reaction mixture is heated to 70° C. for 3 hours. After reaction, the solution is placed onto a rotary evaporator to remove excess thionyl chloride and gas by products.

[0194] 1.0 g of PVA powder (10 kDa) is dissolved into 35 mL of 1-methyl-2-pyrrolidinone at 90° C. The temperature is then lowered to 50° C., followed by addition of the 2,3,5-triiodobenzoic chloride intermediate solution (7 ml, 2.3 mmol) to the PVA solution along with the triethylamine catalyst solution (1 ml). The reaction is stirred at 350 rpm overnight. After the reaction was stopped, the solution is added dropwise into acetone (200 ml) to precipitate out the polymer. This polymer is then re-dissolved in NMP and precipitated into acetone again to purify the polymer. The polymer is then dried under vacuum (24 hours). Following Example 1, biodegradable beads are then synthesized using the functionalized PVA polymer.

##STR00035##

Example 23: Drug Loading of Modified Microspheres

[0195] 1 mL of microspheres from examples 9, 10, 11 and 12 were suspended in 1.5 mL of doxorubicin solution (concentration 25 mg/mL) under constant agitation. At predetermined time points the supernatant solution was sampled and doxorubicin concentration determined at UV at 483 nm against a known reference.

[0196] The loading profiles are given in FIG. 4