Egg per day is helpful for weight loss, because the egg white in the development of amino acids to help muscle tissue, thereby enhancing the body's metabolism function. Add a little time to eat egg white cheese, not only add flavor. And more conducive to weight loss.
Polymer International Polym Int 53:1994–2000 (2004) DOI: 10.1002/pi.1611 Functionally-modiﬁed egg white albumen hydrogels GVN Rathna, J Li and S Gunasekaran∗ Food and Bioprocess Engineering Laboratory, University of Wisconsin-Madison, 460 Henry Mall, Madison, WI 53706, USA Abstract: Hydrogels were prepared by using egg white albumen (EWA) before and after chemical modiﬁcation of its lysyl residues with ethylenediamine tetraacetic dianhydride (EDTAD) to incorporate carboxylic groups. This resulted in an increase in swelling ratio of the EWA hydrogels. The swelling ratio increased dramatically in deionized water substantially, more than in pH 7.4 buffer solution. The effects of medium pH, temperature and swelling were investigated, along with crosslinking of the gel network by glutaraldehyde (GLA), as well as acetone treatment. The gels denatured by acetone showed an insigniﬁcant increase in swelling ratio for the gels crosslinked with GLA during gel preparation, which is in contrast to the gels crosslinked subsequent to gel formation. The swelling behavior was positively affected by temperature and time. However, an insigniﬁcant effect of pH was observed due to electrostatic screening of the carboxylic groups by sodium ions in the buffer solution. Availability of various functional groups on EWA has resulted in adsorption of metals (Cu+2 ions) and non-metals (PO4 −2 anions). 2004 Society of Chemical Industry Keywords: egg white albumen; hydrogel; chemical modiﬁcation; swelling ratio; chelation INTRODUCTION contains various functional groups such as –NH2 , Hydrogels are three-dimensional hydrophilic networks –COOH, –SH and –OH. Therefore, modiﬁcation of with an ability to absorb large quantities of water. A these functional groups without altering the structural considerable amount of research has been performed properties could enable us to develop a novel on the properties of hydrogels made from synthetic and hydrogel with improved properties. The lysyl residues natural polymers. These investigations have focused (–NH2 ) of proteins can be modiﬁed with carboxylic on the effects of composition,1 temperature,2,3 pH,2 – 5 groups by reacting with ethylenediamine tetraacetic ionic strength, magnetic properties,6 electric ﬁelds, dianhydride (EDTAD).8 – 10 Such a modiﬁcation added additives, etc. Many synthetic polymers have of the lysyl residues of proteins can improve limited structural and functional properties, while the the swelling properties and transparency of the natural polymers are unique, with various functional hydrogel formed. Therefore, the developed gels and structural properties.7 The mechanical properties may be suitable for several potentially ‘value- and swelling properties of hydrogels made by using added’ biomedical or biotechnological applications. natural polymers can be improved by chemical or Additionally, an interesting aspect of EDTA-like physical modiﬁcation of the functional groups.8 – 10 chelating groups in the modiﬁed polymers has Modiﬁcation does not alter the biodegradable and provided an ability to form anionic complexes which biocompatible characteristics of the proteins. There- show adsorption to metal cations.12,13 fore, if suitable functionalities can be imparted, the Our objectives were to (1) chemically modify the natural polymers could replace some potentially toxic lysyl residues of EWA, (2) prepare various EWA synthetic polymers, which are unsuitable for many hydrogels, (3) determine the swelling behavior of biological applications. different EWA hydrogels, and (4) study the ability Egg white albumen (EWA) protein is widely used of EWA hydrogels to adsorb metal and non-metal for various food applications.11 However, the use of ions. EWA for ‘value-added’ non-food applications has received little attention. The EWA has an ability to form a non-reversible gel at temperatures above EXPERIMENTAL 80 ◦ C due to covalent disulﬁde (S–S) bond formation. The EWA powder was obtained from the Oskaloosa Nonetheless, the so-formed EWA gels are opaque with Food Products Corporation (Oskaloosa, IA, USA), minimum swelling ability. The EWA, being a protein, while EDTAD, cupric sulfate, glutaraldehyde (GLA), ∗ Correspondence to: S Gunasekaran, Food and Bioprocess Engineering Laboratory, University of Wisconsin-Madison, 460 Henry Mall, Madison, WI 53706, USA E-mail: email@example.com (Received 18 July 2003; revised version received 11 February 2004; accepted 9 March 2004) Published online 13 October 2004 2004 Society of Chemical Industry. Polym Int 0959–8103/2004/$30.00 1994 Modiﬁed egg white albumen hydrogels sodium phosphate (monobasic), trinitrobenzenesul- spectrophotometer (UV/Vis-1601PC, Shimadzu), at a fonic (TNBS) acid, sodium potassium tartarate wavelength of 415 nm against a blank. The percentage and dialysis membranes (molecular weight cutoff, of lysyl residues modiﬁed (PLRM) in the EWA was 6000–8000 g mol−1 ) were obtained from the Sigma- determined as follows:14 Aldrich Company (St Louis, MO, USA). All reagents OD × number of dilutions were of analytical grade. Synthesis of EDTAD- PLRM = 1.5 × 107 × number of moles of protein modiﬁed EWA was performed according to the method of Hwang and Damodaran.10 Samples of × 100 (1) 100 ml of 5 % EWA solution were adjusted to pH where OD is the optical density of the protein solution. 12, and measured amounts of EDTAD were then added incrementally while stirring and maintaining Preparation of EWA hydrogels the solution at pH 12. After complete addition of The EWA and modiﬁed EWA powders were used for the EDTAD, the stirring was continued for 3 h. The hydrogel preparation. Additional experimental vari- reaction mixture was dialysed overnight and ﬁnally ables during gel preparation were GLA addition (for freeze-dried to obtain the dry modiﬁed EWA product. crosslinking) and acetone treatment (for denatura- The experimental steps for EWA modiﬁcation and tion). The latter treatment can denature the protein, hydrogel formation are illustrated in Fig 1. leading to conformational changes of the protein and thus enhance the rate and extent of swelling of the Estimation of modiﬁed lysyl residues hydrogels.8,9 The lysyl contents of the modiﬁed and unmodiﬁed The gels were prepared by dissolving the calculated EWA were determined by the TNBS method in amounts of protein in water (15 % (w/v)), and the triplicates as described by Hall et al.14 According solutions were heated to, and held at, 80 ◦ C for to this procedure, 0.5 ml of protein is added to 1 h. The gels were then cooled to room temperature 1.0 ml of 4 % NaHCO3 solution, followed by the (∼25 ◦ C) and ﬁnally further cooled at −20 ◦ C for 1 h. addition of 0.2 ml TNBS solution (12.5 mg ml−1 ). For crosslinking the gels, GLA was added either This solution mixture was incubated at 40 ◦ C for 2 h, during gelation (ie to the 15 % protein solution—a followed by the addition of 3.5 ml of concentrated 1 % GLA solution was added before it was heated) HCl, and further incubated at 110 ◦ C for 3 h. The or subsequently to gel formation (ie by immersing solution was cooled and made up to 10 ml, extracted thin gel disks in 1 % GLA solutions overnight). The twice with equal amounts of ether, from which the crosslinked gels were washed thoroughly and ﬁnally aqueous solution was separated and left at 40 ◦ C to dried at 30 ◦ C to constant mass. Prior to drying, remove traces of ether. The absorbency of the resulting some of the uncrosslinked gels and gels crosslinked yellow solution was measured by using a UV–visible with GLA during gelation were also treated with acetone for 3 h. All gel samples were dried to constant Protein solution mass in a desiccator. The various hydrogels prepared NaOH solution were denoted differently for easy reference in the subsequent tables and ﬁgures, as listed in Table 1. PH 12, protein Swelling experiments Incubate for 30 min at 60 °C The hydrogel samples were swollen in deionized water EDTAD and/or in phosphate buffer solution at 37 ◦ C. Their Modified protein Table 1. Abbreviations used to refer to the different EWA hydrogels Dialysis prepared for investigation Lyophilization Abbreviation Description EDTAD modified AC Albumen control Water AA Acetone-treated albumen AG Crosslinked albumen during gel preparation Modified protein ACG Cross-linked albumen after gel preparation MAC Modiﬁed-albumen control Incubate for 60 min at 80 °C MAA Acetone-treated modiﬁed albumen MAG Crosslinked modiﬁed albumen during gel Hydrogel preparation MAAG Acetone-treated crosslinked modiﬁed Dried hydrogel Acetone treatment albumen during gel preparation MACG Crosslinked modiﬁed albumen after gel preparation Dried hydrogel MAAC Modiﬁed-acetone-treated-albumen control MAACG Acetone-treated crosslinked modiﬁed Figure 1. Flowchart for lysyl residue modiﬁcation and preparing albumen after gel preparation different modiﬁed EWA hydrogels. Polym Int 53:1994–2000 (2004) 1995 GVN Rathna, J Li, S Gunasekaran masses were measured periodically until equilibrium Adsorption of phosphate anions and copper ions was achieved (ie the mass change between two The hydrogels of modiﬁed and unmodiﬁed EWA were consecutive measurements over 6 h was within used to determine their chelating abilities of phosphate ±0.1 g). Since we suspected a possible interaction anion (PO4 −2 ) and copper ion (Cu+2 ). between the phosphate buffer and the gel, for a selected Stock solutions of sodium phosphate (monobasic) condition the hydrogel samples were also swollen in were made in water at different concentrations of Tris buffer solution at various pH levels at 25 ◦ C. 5, 10, 20, 40, 80 and 160 mg l−1 . Dry pellets of The swelling experiments were performed in 48 %-modiﬁed and unmodiﬁed EWA were weighed duplicate. The swollen masses of the hydrogels were and immersed in the stock solutions in duplicate for measured gravimetrically after wiping off any excess 2 h. The amount of phosphate anion adsorbed by the water on the surfaces with ﬁlter paper. The swelling swollen hydrogels was estimated by using a Lachat ratios (SR, g g−1 of dry gel mass) were calculated by UV/Visible spectrophotometer operating at 880 nm using the following equation: (Zellweger Analytics, Lachat Instrument Division, Milwaukee, WI, USA). mt − mf A limited study was carried out to investigate SR = (2) the adsorption of copper by the EWA gels. Copper mf sulfate (CuSO4 ) solution was prepared in water at a concentration of 5 mg l−1 : 20 ml samples of CuSO4 where mt is the mass of swollen gel at time t and mf is solutions were taken in duplicate. Dry pellets of the mass of ﬁnal dried gel after swelling and drying to 48 %-modiﬁed and unmodiﬁed EWA dry pellets constant mass. were immersed in these solutions. The EWA pellets A ‘24 ’ unreplicated factorial experimental design were removed from the CuSO4 solutions after 0.5, was used for evaluating the effects of PLRM, pH, 2 and 24 h of reaction time and the amounts of temperature and swelling time on the swelling behavior Cu+2 adsorbed by the hydrogels were estimated by of modiﬁed albumen control (MAC) hydrogels in using a ﬂame atomic absorption spectrophotometer. phosphate buffer solution. The experimental variables A ‘standard curve’ was established by using copper are described in Table 2. The initial factorial design solutions with concentrations of 1, 3 and 5 mg l−1 considering all of these effects assumes the following to estimate the amounts of Cu+2 adsorbed by the model: EWA gels. A B C D AB y=η+ x1 + x2 + x3 + x4 + x1 x2 2 2 2 2 2 RESULTS AND DISCUSSION AC AD BC BD Modiﬁcation of lysyl residues + x1 x3 + x1 x4 + x2 x3 + x2 x4 2 2 2 2 The extent of lysyl residue modiﬁcation increased CD ABC ABD linearly (R2 = 0.9769) with increasing EDTAD to + x3 x4 + x1 x2 x3 + x1 x2 x4 2 2 2 EWA ratio, as shown in Fig 2. Based on the reaction ACD BCD conditions, EDTAD has introduced about three + x1 x3 x4 + x2 x3 x4 carboxylic groups for each lysyl residue.10 The reaction 2 2 scheme is shown in Fig 3. ABCD + x1 x2 x3 x4 + ε (3) 2 Swelling ratios The swelling ratios of MAC hydrogels prepared where y is the swelling ratio, η the grand mean, A the under different ‘24 ’ unreplicated factorial experimental PLRM, B the pH, C the temperature and D the time. Multiple parameters (AB, AC, . . ., ABCD) indicate interaction effects. The analysis was performed by 120 using Yates algorithm in the ‘XLISPSTAT’ statistical 100 package, and the signiﬁcant effects were determined by using Loh’s method for the treatment of unreplicated 80 PLRM (%) factorial experimental data.15 60 y = 483.56x + 1.1191 40 Table 2. The unreplicated ‘24 ’ factorial design used for investigating R 2 = 0.9769 the swelling behavior of EWA hydrogels 20 Treatment factor Variable Low-level (−) High-level (+) 0 0 0.05 0.1 0.15 0.2 0.25 Modiﬁed lysyl residue (%) A 0 28 pH B 4.6 9.7 EDTAD/EWA (wt/wt) Temperature (◦ C) C 25 37 Time (min) D 30 60 Figure 2. Percentage of lysyl residues modiﬁed (PLRM) in EWA as a function of the EDTAD/EWA ratio. 1996 Polym Int 53:1994–2000 (2004) Modiﬁed egg white albumen hydrogels CH2COO− at pH 12 H 2N + EDTAD HN N COO− Room C N NH2 NH2 temperature CH2COO− O Egg white albumen EDTAD− egg white albumen Figure 3. Lysyl residue modiﬁcation reaction scheme in EWA. conditions are listed in Table 3. The results of the The swelling kinetics of uncrosslinked hydrogels statistical analysis of these data are presented in (in deionized water), prepared from EWA after Table 4. From the statistical analysis, the model for the different lysyl residue modiﬁcations, is presented swelling ratio of EWA hydrogels in 0.1 M phosphate in Fig 4. The swelling ratios of these hydrogels buffer solution can be written as follows: increased with the PLRM. Due to the competition between expansion and contraction (disulﬁde bonds A C D and hydrogen bonds), the EWA hydrogels prepared y=η+ x1 + x3 + x4 + ε (4) 2 2 2 with a PLRM of 100 % disintegrated after 3 h, while those prepared by using EWA with a PLRM of 83 % In the above model, all of the coefﬁcients (x1 , x3 collapsed after 5 h. and x4 ), η (grand mean) and ε (distributed normal The proﬁles displayed in Fig 5 represent the swelling variable) are positive, hence indicating the positive behavior in phosphate buffer of pH 7.4 at 37 ◦ C for effects of the different treatments, ie PLRM (A), temperature (C) and time (D). The positive value Table 4. Effects calculated by the Yates algorithm and Loh’s of x1 associated with the PLRM clearly indicates that method15 (the conditions having a signiﬁcant effect are indicated by introducing carboxylic groups into EWA increases the ‘bold script’) gel SR. In addition, judging from the relative values of x1 , x3 and x4 it is clear that the effect of the PLRM on Effect Value Signiﬁcant? the SR is about twice that of the effects of temperature η 15.08 No and time. The positive effect of temperature on the A 18.14 Yes SR of the hydrogel may be related to an increase B 0.11 No in the degree of expansion. When the levels of all AB 1.95 No three factors are high (ie modiﬁcation ratio, 28.5 %, C 8.12 Yes at 37 ◦ C over 60 min), a maximum SR of EWA will be AC 3.48 No expected. It is worth noting that the results indicate an BC −0.49 No insigniﬁcant effect of pH (see Table 4), which may be ABC 0.19 No due to electrostatic screening of the carboxyl groups D 7.27 Yes by sodium ions in the buffer solution. AD 1.40 No BD −0.41 No ABD 0.47 No Table 3. Swelling ratio values obtained by the unreplicated ‘24 ’ CD 2.24 No experimental design ACD 0.19 No BCD 0.41 No Treatment factora ABCD 0.22 No Swelling Number Run order A B C D ratio (%) 1 9 − − − − 1.83 180 2 5 + − − − 13.77 Unmodified 160 3 1 − + − − 1.73 36% 4 11 + + − − 16.69 140 56% Swelling ratio (wt/wt) 83% 5 15 − − + − 5.29 120 100% 6 12 + − + − 23.87 100 7 6 − + + − 3.44 8 2 + + + − 24.93 80 9 7 − − − + 6.70 60 10 10 + − − + 20.58 40 11 8 − + − + 4.49 12 3 + + − + 22.36 20 13 16 − − + + 13.89 0 14 13 + − + + 34.29 0 2 4 6 8 10 15 4 − + + + 10.67 Time (h) 16 14 + + + + 36.73 Figure 4. Swelling behavior of hydrogels made from unmodiﬁed EWA aA, percentage-modiﬁed lysyl residue; B, pH; C, temperature; D, time: and EWA with different extents of percentage of lysyl residues ‘+’ indicates ‘high-level’ and ‘−’ indicates ‘low-level’ (see Table 2). modiﬁed (PLRM) in deionized water as a function of time. Polym Int 53:1994–2000 (2004) 1997 GVN Rathna, J Li, S Gunasekaran 3.5 14 3.0 12 Swelling ratio (wt/wt) 10 Swelling ratio (wt/wt) 2.5 8 2.0 6 1.5 4 MAC MAA 1.0 2 MACG AC MAAG MAG AA 0 0.5 AG 0 20 40 60 80 100 120 140 ACG Time (h) 0.0 0 20 40 60 80 100 120 140 Figure 7. Swelling behavior of 48 %-modiﬁed EWA hydrogels in a pH Time (h) 7.4 buffer solution (see Table 1 for legend description). Figure 5. Swelling behavior for unmodiﬁed EWA hydrogels (see Table 1 for legend description). 20 18 unmodiﬁed EWA hydrogels with or without GLA 16 crosslinking, during and after gel preparation, and Swelling ratio (wt/wt) with acetone treatment. For a given PLRM, the SR is 14 higher in deionized water than in the buffer solution 12 by several orders of magnitude. An increase in SR 10 for the acetone-treated EWA hydrogels was expected, as per earlier reports on other proteins.8 However, in 8 MAC MAAC this case the acetone treatment did not improve the 6 MACG SR, possibly due to the effect of temperature (80 ◦ C) 4 MAACG MAG at which the gels were prepared. At this temperature, MAAG 2 the EWA is completely denatured, hence countering 0 5 10 15 20 any positive effects of the acetone treatment. The SR Time (h) decreased when the gels were crosslinked with GLA after the gels were formed. However, the SR increased Figure 8. Swelling behavior of 63 %-modiﬁed EWA hydrogels in a pH7.4 buffer solution (see Table 1 for legend description). when GLA was added during gelation. The higher swelling for gels crosslinked during gelation may be due to the hydrolysis of EWA in the presence of GLA at Figures 7 and 8 present the swelling behavior for 80 ◦ C. The scheme for this hydrolysis is given in Fig 6. modiﬁed EWA, with and without cross-linking, and The aldimine bond (–HC=N–) is unstable at high after acetone treatment in a pH 7.4 buffer at temperatures, and tends to hydrolyse. Free EWA 37 ◦ C, respectively, for PLRMs of 48 and 63 %. chains are formed after hydrolysing, and the crosslink- When comparing Figs 5, 7 and 8, it is clear that ing density is decreased, and, therefore, the swelling the lysyl-residue modiﬁcation of the EWA resulted of EWA is increased. in an increase in swelling by several orders of C HO H N C NH2 + C HO H N C Egg white albumen Glutaraldehyde Hydrolysis 80 °C C HO H2N C HO H2N Free albumen chains Figure 6. Scheme of the proposed hydrolysis of the EWA hydrogel prepared with GLA addition during gelation. 1998 Polym Int 53:1994–2000 (2004) Modiﬁed egg white albumen hydrogels magnitude, regardless of the gel preparation protocol, 100 when compared to their unmodiﬁed-EWA-hydrogel Deionized water 90 counterparts. The increase in swelling is due to an phosphate buffer solution (pH 7.4) increase in number of carboxylic groups, which do 80 Tris buffer solution (pH 7.2) not participate in the crosslinking step. In addition, 70 Swelling ratio (w/w) as stated previously, the higher the PLRM, then the higher the SR, regardless of the gel preparation 60 protocol, because at a higher PLRM the crosslink 50 density is lower. Figure 9 illustrates the swelling behavior for 36 %-modiﬁed EWA hydrogels and 40 unmodiﬁed EWA hydrogels in Tris buffer solutions. 30 There is no signiﬁcant difference for the unmodiﬁed EWA hydrogels in the pH range 7.0–8.9, while 20 swelling of the modiﬁed EWA hydrogels increased 10 when the pH increased in the Tris buffer solution. Figure 10 clearly illustrates these effects for MAC gels, 0 36% 48% 56% 63% both in deionized water and in pH 7.4 buffer. There PMRL is no signiﬁcant difference in swelling between the Tris buffer solution (pH 7.2) and the phosphate buffer Figure 10. Comparison of the swelling ratios of EWA hydrogels as a solution (pH 7.4), while the swelling in deionized function of percentage of lysyl residues modiﬁed (PLRM), in deionized water is much higher than those in buffer solutions. water, in pH 7.4 buffer solution and in Tris buffer solution (pH 7.2) (bars represent standard deviations). Adsorption of phosphorous anions and copper Table 5. Phosphorous adsorption over 2 h by hydrogels made with ions 63 %-lysyl-residue-modiﬁed egg white albumen Table 5 shows the amounts of phosphorous anion adsorbed onto the modiﬁed and unmodiﬁed EWA Initial Modiﬁed Unmodiﬁed EWA hydrogels. The adsorption of phosphorous anion is concentration (mg l−1 ) EWA (mg g−1 ) (mg g−1 ) not affected by lysyl-residue-modiﬁcation of EWA. 5 4.5 4.08 This is because, apart from amino groups, there are 10 9.00 9.47 other positive sites, such as hydroxyl (–OH) and 20 16.79 15.36 –SH groups, which are involved in adsorption of the 40 18.93 21.18 phosphorous anions. Hence, an increase in the PLRM 80 32.97 34.92 has no effect on the phosphorous anion adsorption. 160 69.94 70.8 Theoretically, there should not be any difference in the phosphorous anion adsorption ability between the modiﬁed EWA hydrogel and the unmodiﬁed 5 to 160 mg l−1 of sodium phosphate resulted in EWA hydrogel, because the modifying protein is an increase in phosphorous adsorption from 4 to actually adding more carboxylic groups into the 70 mg g−1 of dry hydrogel for both modiﬁed and protein. (PO4 −2 is an anion and so is the carboxylic unmodiﬁed EWA proteins. It seems that the gels have group (COO− )). An increase in concentration from not reached the maximum extent of possible PO4 −2 absorption but only that of ‘slowly saturating’ available sites—the binding was 80 %, equivalent to a solution 25 concentration of 5 mg l−1 , compared to about 45 % at a concentration of 160 mg l−1 . 20 The results obtained from the limited studies on pH 7.2 copper ion adsorption indicated that 63 %-PLRM Swelling ratio (wt/wt) pH 8.0 gels adsorbed 2.25 mg g−1 , compared to 1.87 mg g−1 15 pH 8.9 of the unmodiﬁed gel. This increase, due to EWA pH 7.2 modiﬁcation, is attributed to an increase in carboxylic 10 pH 8.0 groups, which are the negative sites for adsorption of pH 8.9 positively charged copper (Cu+2 ) ions. 5 CONCLUSIONS 0 The swelling ratios (SR) of gels made from egg white 0 5 10 15 20 25 30 albumen (EWA) can be increased by modifying its Time (h) lysyl residues and incorporating carboxylic groups. An Figure 9. Swelling behavior of 36 %-modiﬁed EWA hydrogels increase in the extent of lysyl residue modiﬁcation (closed symbols) and unmodiﬁed EWA hydrogels (open symbols) in resulted in an increase in the SR, both in deionized Tris buffer solution (at pH 7.2). water and in pH 7.4 buffer solutions. In addition, Polym Int 53:1994–2000 (2004) 1999 GVN Rathna, J Li, S Gunasekaran the temperature (25 ◦ C versus 37 ◦ C) also had a 5 Wang T, Turhan M and Gunasekaran S, Selected properties of positive effect on the SR. For a given amount of a pH-sensitive, biodegradable chitosan–PVA hydrogel. Polym Int 53:911 (2004). modiﬁcation, the SR is higher in deionized water 6 Xulu PM, Filipcsei G and Zrinyi M, Preparation and responsive than in the buffer solutions by several orders of properties of magnetically soft poly(N-isopropylacrylamide) magnitude. The SR decreased when the gels were gels. Macromolecules 33:1716 (2000). crosslinked with glutaraldehyde after the gels were 7 Amiya T and Tanaka T, Phase transitions in crosslinked gels of formed, but increased when glutaraldehyde was added natural polymers. Macromolecules 20:1162 (1987). 8 Rathna GVN and Damodaran S, Swelling behavior of protein- during gelation. Acetone treatment of the EWA did based superabsorbent hydrogels treated with ethanol. J Appl not have any effect on the SR. The EWA gels can Polym Sci 81:2190 (2001). chelate some metals (Cu+2 ) and non-metals (PO4 −2 ). 9 Rathna GVN and Damodaran S, Effect of nonprotein polymers The extent of lysyl residue modiﬁcation seems to have on water-uptake properties of a ﬁsh protein-based hydrogel. J a positive effect on the absorption of Cu+2 ions but Appl Polym Sci 85:45 (2002). 10 Hwang DC and Damodaran S, Chemical modiﬁcation strate- not PO4 −2 anions. gies for synthesis of protein-based hydrogels. J Agric Food Chem 44:751 (1996). 11 Lu GH and Chen TC, Application of egg white and plasma REFERENCES powders as muscle food binding agents. J Food Eng 42:147 1 Ashbaugh HS, Piculell L and Lindman B, Interactions of (1999). cationic/nonionic surfactant mixtures with an anionic hydro- 12 Hwang DC and Damodaran S, Metal-chelating properties gel: absorption equilibrium and thermodynamic modeling. and biodegradability of an ethylenediaminetetraacetic acid Langmuir 16:2529 (2000). dianhydride modiﬁed soy protein hydrogel. J Appl Polym Sci 2 Zhang XZ, Yang YY, Chung TS and Ma KX, Preparation 64:891 (1997). and characterization of fast-response macroporous poly(N- 13 Bicak N, Senkal BF and Melekaslan D, Poly(styrene sulfon- isopropylacrylamide) hydrogels. Langmuir 17:6094 (2001). amides) with EDTA-like chelating groups for pemoval of 3 Zhang J and Peppas NA, Synthesis and characterization of pH- transition metal ions. J Appl Polym Sci 77:2749 (2000). and temperature-sensitive poly(methacrylic acid)/poly(N- 14 Hall RJ, Trinder N and Givens DI, Observations on the use isopropylacrylamide) interpenetrating polymeric networks. of 2,4,6-trinitrobenzenesulphonic acid for the determination Macromolecules 33:102 (2000). of available lysine in animal protein concentrations. Analyst 4 Torres-Lugo M and Peppas NA, Molecular design and in vitro 98:673 (1973). studies of novel pH-sensitive hydrogels for the oral delivery of 15 Loh WY, Identiﬁcation of active contrasts in unreplicated calcitonin. Macromolecules 32:6646 (1999). factorial experiments. Computat Stat Data Anal 4:135 (1992). 2000 Polym Int 53:1994–2000 (2004)
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