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Binding of d -mannose to hydrogel matrix using isothiocyanate derivatives
EUROPEAN POLYMER JOURNAL
European Polymer Journal 42 (2006) 209–212
www.elsevier.com/locate/europolj
Binding of D-mannose to hydrogel matrix using isothiocyanate derivatives Jirˇ´ı Labsky´
*
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic Received 24 November 2004; received in revised form 8 December 2004; accepted 12 April 2005 Available online 6 October 2005
Abstract Crosslinked hydrogels from 2-hydroxyethyl methacrylate (HEMA), ethylene dimethacrylate and polymerizable active esters based on N-methacryloylated x-amino acids were prepared and modified with excess of ethane-1,2-diamine or hexane-1,6-diamine. 4-Isothiocyanatophenyl mannopyranoside or 6-(4-isothiocyanatobenzamido)hexyl mannopyranoside were used to bond D-mannose to hydrogel matrix through thioureylene groups. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Mannose; Hydrogels; Mannose rich hydrogels; 4-Isothiocyanatophenyl mannopyranoside; Spacer; Active esters; Thiophosgene
1. Introduction Biological systems, such as some cell types, lectins and cell toxins, possess receptors, which enable temporary immobilization on the surface of polymer matrix with appropriate covalently bonded ligands. The temporarily formed receptor–ligand bond enables manipulation with the thus formed complex, such as separation, purification, cultivation or transport. Appropriate ligands for biological receptors are chemically bound saccharides, such as glucose, mannose, galactose or disaccharides (lactose). The type of saccharide, length of the spacer or structure of the matrix influence the formation of complex. Frequently are used polymerizable derivatives of mono- or disaccharides, where the hydroxy groups are protected, e.g., by acetylation, benzoylation or benzylation. Acetal derivatives of saccharides or, *
Tel.: +420 296 809 339; fax: +420 296 809 410. E-mail address: [email protected]
specifically, analogous O-isopropylidene derivatives prepared by condensation with acetone can be converted by a suitable chemical modification to polymerizable derivatives. A variety of polymers with covalently bound saccharides are described, where polymerizable derivatives of saccharides are homopolymerized or copolymerized with hydrophilic (2-hydroxyethyl methacrylate, acrylamide, methacrylamide, 1-vinylpyrrolidin-2-one) or hydrophobic monomers (styrene, methyl methacrylate) [1–8]. Binding of 2-amino-2-deoxysaccharides to soluble drug carriers [9–11] or insoluble hydrophilic matrix is described in literature [12–16]. Isothiocyanate derivatives of D-mannose, with or without protective groups, suitable for binding to hydrophilic matrix are described in this article. 2. Methods and materials 2-Hydroxyethyl methacrylate, ethylene dimethacrylate, x-amino acids, methacryloyl chloride, 4-nitrobenzoyl
0014-3057/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2005.04.015
210
J. Labsky´ / European Polymer Journal 42 (2006) 209–212
chloride, 6-aminohexan-1-ol, N-hydroxyphthalimide, D-mannose, 4-nitrophenyl a-D-mannopyranoside, mercury(II) cyanide, ammonium formate, 10% palladium on activated charcoal, silica gel (catalog No. 60741) and solvents were Fluka products. UV initiator Darocur 1173 is from Ciba. The instruments used were: UV lamp Philips 20 W, UV–vis Perkin Elmer Lambda 20 spectrometer, gas chromatograph Perkin Elmer autosystem XL and XL turboMass MS detector, NMR spectrometer Bruker Avance DPX 300. Foils for thin layer chromatography with UV detection, were from Fluka. 2.1. 4-Isothiocyanatophenyl a-D-mannopyranoside (1) A solution of 4-nitrophenyl 2,3,4,6-tetra-O-acetyl-awas reduced with a mixture of ammonium formate and palladium on activated charcoal in boiling methanol under argon. The resulting 4-aminophenyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranoside was deacetylated in methanol containing sodium methanolate. The title compound was prepared by adding excess of thiophosgene to a magnetically stirred solution of 4-aminophenyl a-D-mannopyranoside in 80% ethanol/water mixture [18–20]. D-mannopyranoside
2.2. 6-(4-Isothiocyanatobenzamido)hexyl a-Dmannopyranoside (2) The title compound was prepared by condensation of 6-(4-nitrobenzamido)hexan-1-ol in the presence of mercury(II) cyanide with 2,3,4,6-tetra-O-acetyl-D-mannopyranosyl bromide. The resulting 6-(4-nitrobenzamido)hexyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranoside was reduced with a mixture of ammonium formate and palladium on activated charcoal in boiling methanol to 6-(4-aminobenzamido)hexyl 2,3,4,6-tetra-O-acetyl-a-Dmannopyranoside [15]. Thiophosgene (1.1 g, 9.0 mmol) was added to a magnetically stirred solution of 2 g (4.6 mmol) of 6-(4amino-benzamido)hexyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranoside in 80% ethanol/water (100 ml). The reaction mixture was allowed to stand at room temperature for 3 h. TLC (benzene/methanol 4:1) showed that all the starting material reacted and a single product formed. Evaporation of the reaction mixture almost to dryness left a semisolid amber-like material. (Rf of starting material 0.60, Rf of product 0.74). 1H NMR in DMSO-d6: –CH2–NH– 3.20; >CH–O–CH2– 3.37; –CH2– 1.29– 1.59. The product was used without any purification. 2.3. Copolymers HEMA 2.3.1. Copolymers HEMA with active esters of methacryloylated x-amino acids (3) [17] A mixture of 20 ml of HEMA, 3 mmol of N-{x-[(1, 3-dioxoisoindolin-2-yl)oxy]x-oxoalkyl}methacrylamide
(n = 1, 2, 3, 5, 11), 0.2 ml of ethylene dimethacrylate and 0.5 ml of Darocur 1173 was bubbled with argon for 10 min, and then transferred to transparent mold enabling preparation of films 1.5 mm thick. The monomer mixture was irradiated for 10 min with six UV lamps (20 W) from a distance of 20 cm. The films were extracted three times with 30% ethanol. Disks 21 mm in diameter were cut from the copolymer equilibrated in distilled water and dried. 2.3.2. Modification of HEMA/active esters copolymers with alkane-1,m-diamines (m = 2, 6) (4), Scheme 1 Five disks (total weight 1.38 g, diameter 21 mm) were immersed in a solution of 0.02 mol of alkane-1,m-diamines (m = 2, 6) in 10 ml of 30% ethanol for 1 h. The reaction was stopped by washing the disks with excess of dilute acetic acid (3%) and water and the disks were dried. 2.3.3. Reaction of HEMA—alkane-1,m-diamine-modified (m = 2, 6) copolymers with saccharide isothiocyanates (6,7) Five disks of HEMA—alkane-1,m-diamine-modified (m = 2, 6) copolymers were immersed in 10 ml of an 30% acetonitrile/water solution containing 2 mmol of a saccharide isothiocyanate (NaHCO3, TEA, pH 9). After 3 h the disks were washed 3 times with excess of a 25% ethanol/water mixture, water and then dried.
3. Results and discussion 3.1. Preparation of isothiocyanato derivatives of mannose Reduction of aromatic nitro compounds using ammonium formate as a source of hydrogen and Pd on charcoal as a catalyst for hydrogenation was smooth with almost quantitative yields. The saccharide can be deprotected with sodium methanolate in methanol (Zemplen reaction) before preparation of isothiocyanato derivative or after binding to hydrogel matrix. The reaction with thiophosgene is a standard operation. Precursor for compound 2, a mannose isothiocyanate, was obtained after long standing in refrigerator as a semisolid material. 3.2. Preparation of copolymers 3.2.1. Preparation of copolymers with active esters Crosslinked HEMA copolymers with polymerizable active esters were prepared by UV-initiated polymerization without solvent of 2-hydroxyethyl methacrylate and 0.3 wt% of ethylene dimethacrylate as crosslinker. As UV initiator were used CIBA product Darocur 1173 (2-hydroxy-2-methyl-1-phenylpropan-1-one) in concen-
J. Labsky´ / European Polymer Journal 42 (2006) 209–212 CH3
CH3
CH3
CO
CO
CO
O
O CH2CH2O CO
NH
CH2CH2OH
CH3
(CH2)n n =1, 2, 3, 5, 11 CO
a
CH3
211
O
CO N CO
3
CO 4
NH
CH3
CH3 b
CO
CO
(CH2)n CO
(CH2)n
(CH2)n
NH CH2 NH2 m m = 2, 6
NH
5
NH
OH O
HO HO
CO
CO
OH O
NH
NCS
CH2
NH m
1 c
CH3
CO
d
NH
HO HO
OH OH O
(CH2)n NH CS NH
O
NH CO
CH2 m
6 CH3
CO
OAc OAc O
AcO
O (CH2)6 NH CO
NCS
NH
HO
2 (CH2)n
CO
HO HO
OH OH O
NH O (CH2)6 NH CO
NH CS NH
CH2
m
7
Scheme 1. (a) Diamine (excess), 30% EtOH, 1 h. (b) Crosslinking. (c) 4-Isothiocyanatophenyl-a-D-mannopyranoside (excess), 30% acetonitrile/H2O, NaHCO3, TEA, pH 9, 1 h. (d) (i) 6-(4-Isothiocyanatobenzamido)hexyl a-D-mannopyranoside (excess), (30% acetonitrile/H2O, NaHCO3, TEA, pH 9), 3 h; (ii) Zemplen deacetylation, MeOH, MeONa, 3 h.
trations 0.50–0.80 wt%. Darocur 1173 was selected for preparation of hydrogels owing to its good solubility in the polymerization mixture. As reactive monomers were used esters of N-hydroxyphthalimide and methacryloylated derivatives of x-amino acids, giving compounds N-{x-[(1,3-dioxoisoindolin-2-yl)oxy]x-oxoalkyl}methacrylamide (n = 1, 2, 3, 5, 11) [17]. All reactive monomers, in a concentration of 2 mol % well soluble in polymerization mixture, were copolymerized with HEMA monomer without difficulties [14,15,17]. The idealized structure of the resulting copolymers is presented in Scheme 1 (3).
A mixture of monomers and a UV initiator was bubbled with argon or carbon dioxide for 10 min in the dark and then transferred to a transparent mold enabling preparation of 1.5-mm-thick polymer films. UV irradiation gave brittle, transparent films of copolymers. The resulting modified hydrogels, after swelling in water, were suitable for aminolysis. 3.2.2. Modification of reactive matrix with alkane-1, m-diamines (4) The reaction of active ester copolymers with alkane1,m-diamines (m = 2, 6) was carried out in a 30%
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J. Labsky´ / European Polymer Journal 42 (2006) 209–212
ethanol/water mixture with excess of diamines (20-fold, 1 h) followed by extraction with a 30% ethanol/water mixture and distilled water, and drying. The reaction time is sufficient for complete aminolysis of all active ester groups in the matrix (comparison of UV spectra of polymer). The probability of side reaction—Scheme 1, (5)—is very low, because the mobility of reactive ends is restricted.
Acknowledgement The author thanks the Grant Agency of the Academy of Sciences of the Czech Republic (Grant No. A4050301) for financial support and Dr. Z. Noha´cˇ (Ciba Specialty Chemicals) for generous gift of UV initiator.
References 3.2.3. Modification of hydrophilic matrix after treating with alkane 1,m-diamines with saccharide isothiocyanates The reaction of aromatic isothiocyanates with aliphatic diamines bonded to hydrophilic matrix usually made in alkaline conditions (NaOH, TEA, DIPEA), can be monitored by IR spectroscopy at 2130 cm 1, but the spectra of aromatic thioureylene groups are inappropriate for quantitative estimation. The yield of the reaction is usually better than 80% [18–20]. Idealized structures of copolymers after the reaction of excess of the isothiocyanate derivatives of D-mannose with aliphatic amines bonded to polymer matrix are given in Scheme 1 (6,7). Compound 2 was deacetylated after binding to a polymer matrix using Zemplen deacetylation.
4. Conclusion Crosslinked copolymers HEMA with polymerizable active esters were transformed with excess of alkane1,m-diamines to polymer matrix with free amino groups. The isothiocyanate derivatives of D-mannose with and without protective groups were used for the preparation of the carriers with a-D-mannose chemically bonded to the matrix via spacers of different lengths and structures. The amount of active ester controls the amount of a saccharide bonded to the polymer matrix. The resulting matrixes are transparent, brittle polymers in dry state; swollen polymers are homogenous, elastic and transparent materials.
[1] Yoshida T. Prog Polym Sci 2001;26:379–441. [2] Iwakura Y, Imai Y, Yagi K. J Polym Sci, Part A-1 1968;6:1625–32. [3] Kimura S, Hirai K. Makromol Chem 1962;58:232. [4] Imoto M, Kimura S. Makromol Chem 1961;50:155–62. [5] Black WAP, Colquhoun JA, Dewar ET. Makromol Chem 1968;117:210–7. [6] Okada M. Prog Polym Sci 2001;26:67–104. [7] Klein J. Makromol Chem Rapid Commun 1985;6:675–7. [8] Kimura S, Imoto M. Makromol Chem 1961;50:155–61. 1962;53:210–216. [9] Solovskij MV, Ulbrich K, Nazarova OV, Zubko NV, Panarin EF, Kopecˇek J. Makromol Chem Phys 1989; 190:2245–54. [10] Bridges JF, Woodley JF, Duncan R, Kopee`ek J. Int J Pharm 1988;44:213–22. [11] Rejmanova´ P, Labsky´ J, Kopee`ek J. Makromol Chem 1977;178:2159–68. [12] Sharan MAE, Podolsky DK, Jeanloz RW. Carbohydr Res 1976;52:129–35. [13] Weigel PW, Naoi M, Roseman S, Lee YC. Carbohydr Res 1979;70:83–91. [14] Labsky´ J, Dvorˇa´nkova´ B, Smetana K, Holı´kova´ Z, Brozˇ L, Gabius HJ. Biomaterials 2003;24:863–72. [15] Labsky´ J. Biomaterials 2003;24:4031–6. [16] Labsky´ J. Czech Patent Application PV 2003-251; PCT/CZ 2004/000005. [17] Labsky´ J, Ka´lal J. Eur Polym J 1979;15:603–5. [18] Kieburg C, Lindhorst TK. Tetrahedron Lett 1997; 38: 3885–8. [19] McBroom CR, Samanen CH, Goldstein IJ. Methods Enzymol 1972;28:212–9. [20] Smith DF, Zopf D, Ginsburg V. Methods Enzymol 1978; 50:163–75.
European Polymer Journal 42 (2006) 209–212
www.elsevier.com/locate/europolj
Binding of D-mannose to hydrogel matrix using isothiocyanate derivatives Jirˇ´ı Labsky´
*
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic Received 24 November 2004; received in revised form 8 December 2004; accepted 12 April 2005 Available online 6 October 2005
Abstract Crosslinked hydrogels from 2-hydroxyethyl methacrylate (HEMA), ethylene dimethacrylate and polymerizable active esters based on N-methacryloylated x-amino acids were prepared and modified with excess of ethane-1,2-diamine or hexane-1,6-diamine. 4-Isothiocyanatophenyl mannopyranoside or 6-(4-isothiocyanatobenzamido)hexyl mannopyranoside were used to bond D-mannose to hydrogel matrix through thioureylene groups. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Mannose; Hydrogels; Mannose rich hydrogels; 4-Isothiocyanatophenyl mannopyranoside; Spacer; Active esters; Thiophosgene
1. Introduction Biological systems, such as some cell types, lectins and cell toxins, possess receptors, which enable temporary immobilization on the surface of polymer matrix with appropriate covalently bonded ligands. The temporarily formed receptor–ligand bond enables manipulation with the thus formed complex, such as separation, purification, cultivation or transport. Appropriate ligands for biological receptors are chemically bound saccharides, such as glucose, mannose, galactose or disaccharides (lactose). The type of saccharide, length of the spacer or structure of the matrix influence the formation of complex. Frequently are used polymerizable derivatives of mono- or disaccharides, where the hydroxy groups are protected, e.g., by acetylation, benzoylation or benzylation. Acetal derivatives of saccharides or, *
Tel.: +420 296 809 339; fax: +420 296 809 410. E-mail address: [email protected]
specifically, analogous O-isopropylidene derivatives prepared by condensation with acetone can be converted by a suitable chemical modification to polymerizable derivatives. A variety of polymers with covalently bound saccharides are described, where polymerizable derivatives of saccharides are homopolymerized or copolymerized with hydrophilic (2-hydroxyethyl methacrylate, acrylamide, methacrylamide, 1-vinylpyrrolidin-2-one) or hydrophobic monomers (styrene, methyl methacrylate) [1–8]. Binding of 2-amino-2-deoxysaccharides to soluble drug carriers [9–11] or insoluble hydrophilic matrix is described in literature [12–16]. Isothiocyanate derivatives of D-mannose, with or without protective groups, suitable for binding to hydrophilic matrix are described in this article. 2. Methods and materials 2-Hydroxyethyl methacrylate, ethylene dimethacrylate, x-amino acids, methacryloyl chloride, 4-nitrobenzoyl
0014-3057/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2005.04.015
210
J. Labsky´ / European Polymer Journal 42 (2006) 209–212
chloride, 6-aminohexan-1-ol, N-hydroxyphthalimide, D-mannose, 4-nitrophenyl a-D-mannopyranoside, mercury(II) cyanide, ammonium formate, 10% palladium on activated charcoal, silica gel (catalog No. 60741) and solvents were Fluka products. UV initiator Darocur 1173 is from Ciba. The instruments used were: UV lamp Philips 20 W, UV–vis Perkin Elmer Lambda 20 spectrometer, gas chromatograph Perkin Elmer autosystem XL and XL turboMass MS detector, NMR spectrometer Bruker Avance DPX 300. Foils for thin layer chromatography with UV detection, were from Fluka. 2.1. 4-Isothiocyanatophenyl a-D-mannopyranoside (1) A solution of 4-nitrophenyl 2,3,4,6-tetra-O-acetyl-awas reduced with a mixture of ammonium formate and palladium on activated charcoal in boiling methanol under argon. The resulting 4-aminophenyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranoside was deacetylated in methanol containing sodium methanolate. The title compound was prepared by adding excess of thiophosgene to a magnetically stirred solution of 4-aminophenyl a-D-mannopyranoside in 80% ethanol/water mixture [18–20]. D-mannopyranoside
2.2. 6-(4-Isothiocyanatobenzamido)hexyl a-Dmannopyranoside (2) The title compound was prepared by condensation of 6-(4-nitrobenzamido)hexan-1-ol in the presence of mercury(II) cyanide with 2,3,4,6-tetra-O-acetyl-D-mannopyranosyl bromide. The resulting 6-(4-nitrobenzamido)hexyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranoside was reduced with a mixture of ammonium formate and palladium on activated charcoal in boiling methanol to 6-(4-aminobenzamido)hexyl 2,3,4,6-tetra-O-acetyl-a-Dmannopyranoside [15]. Thiophosgene (1.1 g, 9.0 mmol) was added to a magnetically stirred solution of 2 g (4.6 mmol) of 6-(4amino-benzamido)hexyl 2,3,4,6-tetra-O-acetyl-a-D-mannopyranoside in 80% ethanol/water (100 ml). The reaction mixture was allowed to stand at room temperature for 3 h. TLC (benzene/methanol 4:1) showed that all the starting material reacted and a single product formed. Evaporation of the reaction mixture almost to dryness left a semisolid amber-like material. (Rf of starting material 0.60, Rf of product 0.74). 1H NMR in DMSO-d6: –CH2–NH– 3.20; >CH–O–CH2– 3.37; –CH2– 1.29– 1.59. The product was used without any purification. 2.3. Copolymers HEMA 2.3.1. Copolymers HEMA with active esters of methacryloylated x-amino acids (3) [17] A mixture of 20 ml of HEMA, 3 mmol of N-{x-[(1, 3-dioxoisoindolin-2-yl)oxy]x-oxoalkyl}methacrylamide
(n = 1, 2, 3, 5, 11), 0.2 ml of ethylene dimethacrylate and 0.5 ml of Darocur 1173 was bubbled with argon for 10 min, and then transferred to transparent mold enabling preparation of films 1.5 mm thick. The monomer mixture was irradiated for 10 min with six UV lamps (20 W) from a distance of 20 cm. The films were extracted three times with 30% ethanol. Disks 21 mm in diameter were cut from the copolymer equilibrated in distilled water and dried. 2.3.2. Modification of HEMA/active esters copolymers with alkane-1,m-diamines (m = 2, 6) (4), Scheme 1 Five disks (total weight 1.38 g, diameter 21 mm) were immersed in a solution of 0.02 mol of alkane-1,m-diamines (m = 2, 6) in 10 ml of 30% ethanol for 1 h. The reaction was stopped by washing the disks with excess of dilute acetic acid (3%) and water and the disks were dried. 2.3.3. Reaction of HEMA—alkane-1,m-diamine-modified (m = 2, 6) copolymers with saccharide isothiocyanates (6,7) Five disks of HEMA—alkane-1,m-diamine-modified (m = 2, 6) copolymers were immersed in 10 ml of an 30% acetonitrile/water solution containing 2 mmol of a saccharide isothiocyanate (NaHCO3, TEA, pH 9). After 3 h the disks were washed 3 times with excess of a 25% ethanol/water mixture, water and then dried.
3. Results and discussion 3.1. Preparation of isothiocyanato derivatives of mannose Reduction of aromatic nitro compounds using ammonium formate as a source of hydrogen and Pd on charcoal as a catalyst for hydrogenation was smooth with almost quantitative yields. The saccharide can be deprotected with sodium methanolate in methanol (Zemplen reaction) before preparation of isothiocyanato derivative or after binding to hydrogel matrix. The reaction with thiophosgene is a standard operation. Precursor for compound 2, a mannose isothiocyanate, was obtained after long standing in refrigerator as a semisolid material. 3.2. Preparation of copolymers 3.2.1. Preparation of copolymers with active esters Crosslinked HEMA copolymers with polymerizable active esters were prepared by UV-initiated polymerization without solvent of 2-hydroxyethyl methacrylate and 0.3 wt% of ethylene dimethacrylate as crosslinker. As UV initiator were used CIBA product Darocur 1173 (2-hydroxy-2-methyl-1-phenylpropan-1-one) in concen-
J. Labsky´ / European Polymer Journal 42 (2006) 209–212 CH3
CH3
CH3
CO
CO
CO
O
O CH2CH2O CO
NH
CH2CH2OH
CH3
(CH2)n n =1, 2, 3, 5, 11 CO
a
CH3
211
O
CO N CO
3
CO 4
NH
CH3
CH3 b
CO
CO
(CH2)n CO
(CH2)n
(CH2)n
NH CH2 NH2 m m = 2, 6
NH
5
NH
OH O
HO HO
CO
CO
OH O
NH
NCS
CH2
NH m
1 c
CH3
CO
d
NH
HO HO
OH OH O
(CH2)n NH CS NH
O
NH CO
CH2 m
6 CH3
CO
OAc OAc O
AcO
O (CH2)6 NH CO
NCS
NH
HO
2 (CH2)n
CO
HO HO
OH OH O
NH O (CH2)6 NH CO
NH CS NH
CH2
m
7
Scheme 1. (a) Diamine (excess), 30% EtOH, 1 h. (b) Crosslinking. (c) 4-Isothiocyanatophenyl-a-D-mannopyranoside (excess), 30% acetonitrile/H2O, NaHCO3, TEA, pH 9, 1 h. (d) (i) 6-(4-Isothiocyanatobenzamido)hexyl a-D-mannopyranoside (excess), (30% acetonitrile/H2O, NaHCO3, TEA, pH 9), 3 h; (ii) Zemplen deacetylation, MeOH, MeONa, 3 h.
trations 0.50–0.80 wt%. Darocur 1173 was selected for preparation of hydrogels owing to its good solubility in the polymerization mixture. As reactive monomers were used esters of N-hydroxyphthalimide and methacryloylated derivatives of x-amino acids, giving compounds N-{x-[(1,3-dioxoisoindolin-2-yl)oxy]x-oxoalkyl}methacrylamide (n = 1, 2, 3, 5, 11) [17]. All reactive monomers, in a concentration of 2 mol % well soluble in polymerization mixture, were copolymerized with HEMA monomer without difficulties [14,15,17]. The idealized structure of the resulting copolymers is presented in Scheme 1 (3).
A mixture of monomers and a UV initiator was bubbled with argon or carbon dioxide for 10 min in the dark and then transferred to a transparent mold enabling preparation of 1.5-mm-thick polymer films. UV irradiation gave brittle, transparent films of copolymers. The resulting modified hydrogels, after swelling in water, were suitable for aminolysis. 3.2.2. Modification of reactive matrix with alkane-1, m-diamines (4) The reaction of active ester copolymers with alkane1,m-diamines (m = 2, 6) was carried out in a 30%
212
J. Labsky´ / European Polymer Journal 42 (2006) 209–212
ethanol/water mixture with excess of diamines (20-fold, 1 h) followed by extraction with a 30% ethanol/water mixture and distilled water, and drying. The reaction time is sufficient for complete aminolysis of all active ester groups in the matrix (comparison of UV spectra of polymer). The probability of side reaction—Scheme 1, (5)—is very low, because the mobility of reactive ends is restricted.
Acknowledgement The author thanks the Grant Agency of the Academy of Sciences of the Czech Republic (Grant No. A4050301) for financial support and Dr. Z. Noha´cˇ (Ciba Specialty Chemicals) for generous gift of UV initiator.
References 3.2.3. Modification of hydrophilic matrix after treating with alkane 1,m-diamines with saccharide isothiocyanates The reaction of aromatic isothiocyanates with aliphatic diamines bonded to hydrophilic matrix usually made in alkaline conditions (NaOH, TEA, DIPEA), can be monitored by IR spectroscopy at 2130 cm 1, but the spectra of aromatic thioureylene groups are inappropriate for quantitative estimation. The yield of the reaction is usually better than 80% [18–20]. Idealized structures of copolymers after the reaction of excess of the isothiocyanate derivatives of D-mannose with aliphatic amines bonded to polymer matrix are given in Scheme 1 (6,7). Compound 2 was deacetylated after binding to a polymer matrix using Zemplen deacetylation.
4. Conclusion Crosslinked copolymers HEMA with polymerizable active esters were transformed with excess of alkane1,m-diamines to polymer matrix with free amino groups. The isothiocyanate derivatives of D-mannose with and without protective groups were used for the preparation of the carriers with a-D-mannose chemically bonded to the matrix via spacers of different lengths and structures. The amount of active ester controls the amount of a saccharide bonded to the polymer matrix. The resulting matrixes are transparent, brittle polymers in dry state; swollen polymers are homogenous, elastic and transparent materials.
[1] Yoshida T. Prog Polym Sci 2001;26:379–441. [2] Iwakura Y, Imai Y, Yagi K. J Polym Sci, Part A-1 1968;6:1625–32. [3] Kimura S, Hirai K. Makromol Chem 1962;58:232. [4] Imoto M, Kimura S. Makromol Chem 1961;50:155–62. [5] Black WAP, Colquhoun JA, Dewar ET. Makromol Chem 1968;117:210–7. [6] Okada M. Prog Polym Sci 2001;26:67–104. [7] Klein J. Makromol Chem Rapid Commun 1985;6:675–7. [8] Kimura S, Imoto M. Makromol Chem 1961;50:155–61. 1962;53:210–216. [9] Solovskij MV, Ulbrich K, Nazarova OV, Zubko NV, Panarin EF, Kopecˇek J. Makromol Chem Phys 1989; 190:2245–54. [10] Bridges JF, Woodley JF, Duncan R, Kopee`ek J. Int J Pharm 1988;44:213–22. [11] Rejmanova´ P, Labsky´ J, Kopee`ek J. Makromol Chem 1977;178:2159–68. [12] Sharan MAE, Podolsky DK, Jeanloz RW. Carbohydr Res 1976;52:129–35. [13] Weigel PW, Naoi M, Roseman S, Lee YC. Carbohydr Res 1979;70:83–91. [14] Labsky´ J, Dvorˇa´nkova´ B, Smetana K, Holı´kova´ Z, Brozˇ L, Gabius HJ. Biomaterials 2003;24:863–72. [15] Labsky´ J. Biomaterials 2003;24:4031–6. [16] Labsky´ J. Czech Patent Application PV 2003-251; PCT/CZ 2004/000005. [17] Labsky´ J, Ka´lal J. Eur Polym J 1979;15:603–5. [18] Kieburg C, Lindhorst TK. Tetrahedron Lett 1997; 38: 3885–8. [19] McBroom CR, Samanen CH, Goldstein IJ. Methods Enzymol 1972;28:212–9. [20] Smith DF, Zopf D, Ginsburg V. Methods Enzymol 1978; 50:163–75.