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“angico” gum nanoparticles: Synthesis and characterization
Materials Science and Engineering C 29 (2009) 448–451
Contents lists available at ScienceDirect
Materials Science and Engineering C j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m s e c
Chitosan/“angico” gum nanoparticles: Synthesis and characterization Marilia A. Oliveira a, Priscila C. Ciarlini b, Judith P.A. Feitosa a, Regina C.M. de Paula a, Haroldo C.B. Paula b,⁎ a b
Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará – C. Postal 6021, 60.455-760, Fortaleza, CE, Brazil Departamento de Química Analítica e Físico-Química, Universidade Federal do Ceará-C. Postal 6021, 60.455-760, Fortaleza, CE, Brazil
a r t i c l e
i n f o
Article history: Received 6 June 2008 Received in revised form 28 August 2008 Accepted 30 August 2008 Available online 9 September 2008 Keywords: Nanoparticles Polyelectrolyte Chitosan Anadenanthera macrocarpa gum
a b s t r a c t Polyelectrolyte complex nanoparticles from chitosan (CH) and “angico” gum (AG) were synthesized with average particle size ranging from 18 to 33 nm and monomodal volume distribution. The effect of polymer concentration on particle size and stability was investigated. No flocculation was observed in the range of particle charge ratio (n+/n−) studied. When the same chitosan and “angico” gum solution concentration was used, the higher the polymer concentration, the smaller the particle size. AG/CH nanoparticles were stable for a storage time up to 26 days. By keeping the CH solution concentration at 10 g l− 1 and increasing the AG solution concentration from 0.25 to 10 g l− 1, reduction in particle size was observed for the n+/n− ratios of 0.1, 1.0 and 10. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Polyelctrolyte complexes (PEC) result from the interaction of oppositely charged polymers. PEC can be obtained as a precipitate, turbid colloidal system and also as homogeneous soluble systems, where the particles are present in submicron-dimension [1–4]. Tsuchida and Abe [5] and Kabanov and Zezin [6] were the first authors to report on soluble nanoparticle polylectrolyte complexes from synthetic polymers, whereby the condition for producing nanoparticles was the presence of polyelectrolyte with weak ionic groups and a large difference in molar masses at a non-stoichiometric mixing ratio. Stabilized nanoparticles were obtained when the neutralized, hydrophobic core was surrounded by a shell of excess polyelectrolyte. Dautzemberg and co-workers [7–8] produced soluble PEC with nearly spherical shape using large molar mass and/or strong ion groups, but at very diluted system (b10− 4 g/ml). Schatz et al. [9–10] and Drogoz et al. [11] produced nanoparticles by polylectrolyte complexation based on biopolymers using chitosan as a polycation and dextran sulfate as a polyanion. Schatz and co-workers proposed different mechanisms for formation of stable nanoparticles based on the polymer in excess, polymer molar mass and flexibility of polymer chains. In the present work, the effect of polymer concentration on the formation of nanoparticle by polyelectrolyte complexation of chitosan and a branched slightly acidic polysaccharide, obtained by exudation of Anadenanthera macrocarpa trees (“angico” tree), was investigated. A. macrocarpa gum (AG) is a polysaccharide composed of arabinose (67%), galactose (24%), rhamnose (2%) and glucuronic acid (7%) [12]. ⁎ Corresponding author. Tel.: +55 85 3366 9961; fax: +55 85 3366 9982. E-mail address: [email protected] (H.C.B. Paula). 0928-4931/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2008.08.032
Molecular characteristics of the whole polysaccharide and its fractions obtained by fractional precipitation have been investigated by static light scattering, dilute solution viscometry and gel permeation chromatography (GPC). Hydrodynamic properties of polysaccharide fractions indicated a highly branched structure and a dependence of molar mass (M) on intrinsic viscosity [η], expressed by the equation: [η] = 0.0145 M0.44, with intrinsic viscosity giving in ml/g. The gum was found to have a broad molar mass distribution with M = 3.7 × 106 g/mol and [η] = 11 ml/g in 1 M NaCl at 25 °C [12]. A. macrocarpa gum was also carboxymethylated with monochloroacetic acid (MCA) in alkaline aqueous medium. The degree of substitution (DS) varied from 0.11 to 1.10 depending on NaOH concentration, MCA/AG ratio and temperature used in the synthesis [13]. 2. Experimental 2.1. Materials Crude polysaccharide samples were collected from A. macrocarpa native trees at Fortaleza, Ceará, Brazil. They were purified as a sodium salt using the method previously described [14]. Nodules free of bark were selected and dissolved in distilled water at room temperature to give a 5% (w/v) solution. The solution pH was adjusted to approximately 7.0 by addition of diluted aqueous NaOH. The clear solution was successively filtered through sintered glass and the purified polysaccharide precipitated with ethanol, after NaCl addition. Chitosan samples were donated by Polymar Ind. Com. Imp. Ltda (deacetylation degree 82%, Mv = 1.8 × 105 g/mol). Chitosan was used as a polycation for the preparation of polyelectrolyte complexes (PEC). Solutions of CH on the concentration range of
M.A. Oliveira et al. / Materials Science and Engineering C 29 (2009) 448–451
0.25 and 10 g l− 1 were prepared by dissolving the desired amount of chitosan in 1% acetic acid. The ionic strength was adjusted to 0.01 with NaCl. AG was used as a polyanion. Solutions of AG on the concentration range of 0.25 to 10 g l− 1 were prepared by dissolving the gum in bidistilled water and the ionic strength was adjusted to 0.01 with NaCl. Prior complex formation, the solutions (CH and AG) were filtered in a 0.22 μm Millipore filter. 2.2. Complex formation PEC were prepared by mixing AG to CH solution in appropriated proportions, in order to obtain a desired n+/n− molar ratio (molar charge ratio of CH and AG). The AG was added to CH with low stirring rate and the mixture was kept resting for 24 h before particle size measurement. The particle size of PEC dispersion was also monitored up to 26 days of storage time. 2.3. Characterization of angico gum and chitosan nanoparticle (AG/CH NP) 2.3.1. Particle size measurement Particle size measurements of AG/CH NP were carried out in a Nano zetasizer from Malvern, Model Zen 3500. All measurements were carried out using 30 scans with 30 s of acquisition time for each scan. 2.3.2. Infrared spectral analysis The IR spectra of the gum, chitosan and PEC were recorded in solid state in KBr pellets using a Shimadzu IR spectrophotometer (model 8300) operating between 400 and 4000 cm− 1.
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3. Results and discussion AG is a high molar mass, low charged polysaccharide due the presence of glucuronic acid (7% w/w) [12]. Despite the low charge density, this polysaccharide exhibits a polyelectrolyte behavior [12]. Paula et al. [12] showed that at low salt concentration, such as 0.1 M NaCl, charges in AG polysaccharide were not screened, however by increasing the salt concentration to 1.0 M, linear plots in the light scattering experiments were obtained, indicating that the charges in the polysaccharide were screened. This unusual behavior for such low charge density polymer may point out to the fact that charges in AG gum chain are distributed such as in a micelle, where the charged monosaccharides are on the surface and the neutral monosaccharides are in the core of the micelle. Therefore it is expected that AG polysaccharide can complex with CH, forming stable nanoparticles (PEC). The volume distribution of PECs formed by the addition of AG solution at 0.25 g l− 1 to chitosan solution (0.25 g l− 1) at a n+/n− ratios of 0.1, 1 and 10 shows monomodal distributions (Fig. 1). Fig. 2 shows the effect of increasing both AG and CH polymer concentrations on particle size, a function of n+/n− ratio. A “U” shape curve was observed for n+/n− ratio between 0.1 and 0.6. This “U” shape behavior was also observed for PEC formed by chitosan and dextran sulfate in a n+/n− ratio of 0.1 and 0.7 [9–10]. Schatz et al. [9] proposed that by adding dextran sulfate to chitosan, where an excess of negative charges are present, colloidal stabilization occurs due the presence of residual anionic charge, leading to a decrease in particle size. As the n+/n− ratio increases, the free anionic charges are neutralized by chitosan and the particle tends to increase in size.
Fig. 1. Particle size distribution as a function of n+/n− charge ratio.
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M.A. Oliveira et al. / Materials Science and Engineering C 29 (2009) 448–451
Fig. 2. Effect of polymer concentration on particle size as a function of n+/n− ratio. (■) AG 0.25 g l− 1 and CH 0.25 g l− 1; (□) AG 10.0 g l− 1 and CH 10.0 g l− 1.
For AG/CH PEC at n+/n− ratio higher than 0.6, an increase in particle size is observed for both concentration. No flocculation was observed in the n+/n− range investigated. Flocculation occurred for complexation of dextran sulfate and chitosan in the n+/n− ratio close to 1 [9–10]. For PEC of dextran sulfate and chitosan, the range of n+/n− ratio where flocculation is observed depends on chitosan and dextran sulfate molar masses [9]. For those polymers, if the molar mass of chitosan is higher than the molar mass of dextran sulfate, flocculations occur in a wider range than if the dextran sulfate molar mass is higher than chitosan one. AG polysaccharide has a higher molar mass (3.7 × 106 g/ mol) and low charge density (7%, w/w) [12] than chitosan and those factors may be responsible for the absence of flocculation on AG/CH PEC. Similar behavior was also observed by adding a polyanion, such poly(maleic acid-co-propene) to polycation (polydiallyldimethyllammonium chloride) where no flocculation was observed for the n+/n− ratio ranging from 2.5 to 0.6 [1]. By increasing both AG and CH concentrations from 0.25 to 10 g l− 1 a decrease in particle size was observed. This data is different of that reported by Hajdu et al. [15] where an increase in particle size was observed when polymer concentrations increase. The effect of AG concentration, keeping CH at constant concentration (10 g l− 1), on particle size as a function of n+/n− ratio is depicted in Fig. 3. Three AG concentrations (0.1, 1.0 and 10 g l− 1) were used to investigate their effect on particle size. By increasing the AG concentration, a reduction in particle size was observed for all three n+/n− ratios. Keeping the AG concentration constant, small particle size was obtained for n+/n− ratio = 0.1, where an excess of negative charge is present.
Fig. 3. Effect of AG solution concentration, keeping CH solution concentration at 10.0 g l− 1, on particle size.
Fig. 4. Effect of storage time of CH/AG PEC at n+/n− charge ratio = 1 on particle size.
Particle size of AG/CH PEC produced at n+/n− ratio = 1.0 and CH and AG solution concentration of 0.25 g l− 1 were monitored for a period of 26 days (Fig. 4). A slight decrease on particle size on the first 5 days was observed followed by a stabilization of particle size. The average particle size in this period of time is almost constant (20.5 ± 1.7 nm). FT-IR spectroscopic analysis of AG, CH and PEC is shown in Fig. 5. The gum showed a broad band at 3379 cm− 1 due to the stretching vibration of O–H, a small peak at 2933 cm− 1, attributed to the C–H stretching vibration, and absorption at 1649 cm− 1, due to O–H scissor vibrations from bound water molecules [16]. Strong peaks at 1150, 1080 and 1030 cm− 1 are due to stretching vibrations of C–O–C from
Fig. 5. FT-IR spectrum of “angico” gum, chitosan and CH/AG PEC nanoparticle.
M.A. Oliveira et al. / Materials Science and Engineering C 29 (2009) 448–451
glucosidic bonds and O–H bending of alcohols. Specific bands for chitosan at 1652 and 1570 cm− 1 corresponding respectively to amide I and NH+3 deformations, as shown in Fig. 5. Most signal characteristics of both AG and CH were overlapped, however, upon complexation, a small change in the value of the assignments and a sharp increase in signal at 1564 cm− 1 characteristic of amine group can be clearly seen, which has been assigned as being due to AG carboxylated groups and CH amine groups interactions. This feature was also observed by Gao et al. [17]. 4. Conclusions CH/AG nanoparticles with narrow volume distributions and sizes in the range from 18 to 33 nm were successfully prepared. Unlike other polysaccharides, data obtained revealed that by increasing both polyanion and polycation concentrations up to 10 g l− 1, a decrease in particle size was observed. Those characteristics, as well as the fact that nanoparticles were shown to be stable for a storage time of up to 26 days, make the system a good candidate for drug delivery applications. Acknowledgement The authors gratefully acknowledge financial support from Rede Nanoglicobiotec/CNPq.
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References [1] H.-M. Buchhammer, M. Mende, M. Oelmann, Colloids Surf., A 218 (2003) 151. [2] B. Philipp, H. dauzenberg, K.J. Linow, J. Koetz, W. Dawydoff, Prog. Polym. Sci. 14 (1989) 91. [3] Q. Wang, Y. Dan, X.G. Wang, J.M.S- Pure Appl. Chem. A34 (1997) 1155. [4] L.M. Zhang, S.L. Huang, Polym. Int. 49 (2000) 528. [5] E. Tsuchida, K. Abe, Interaction between Macromolecules in Solution and Intermacromolecular Complexes (Chap.1), verlag, Berlin, 1981. [6] V.A. Kabanov, A.B. Zezin, Makromol. Chem. (suppl. 6) (1984) 259. [7] H. Dautzemberg, N. Karibyants, N, Macromol. Chem. Phys. 200 (1999) 118. [8] H. Dautzemberg, W. Jaeger, Macromol. Chem. Phys. 203 (2002) 2095. [9] C. Schatz, A. Domard, C. Viton, C. Pichot, T. Delair, Biomacromolecules 5 (2004) 1882. [10] C. Schatz, A. Bionaz, J.M. Lucas, C. Pichot, C. Viton, A. Domart, T. Delair, Biomacromolecules 6 (2005) 1642. [11] A. Drogoz, L. David, C. Rochas, A. Domard, T. Delair, Langmuir 23 (2007) 10950. [12] R.C.M. de Paula, P.M. Budd, J.F. Rodrigues, Polym. Int. 44 (1997) 55. [13] M.A. Oliveira, D.A. Silva, D.E. Uchoa, J.S. Maciel, J.P.A. Feitosa, H.C.B. Paula, R.C.M. de Paula, J. Appl. Polym. Sci. 103 (2007) 2985. [14] R.C.M. de Paula, S.A. Santana, J.F. Rodrigues, Carbohydr. Polym. 44 (2001) 133. [15] I. Hadju, M. Bodnár, G. Filipesei, J.F. Hartmann, L. Daróczi, M. Zrínyi, J. Borbély, Colloid Polym. Sci. 286 (2008) 343. [16] M.J. Zohuriaan, F. Shokrolahi, Polym. Test. 23 (2004) 575. [17] Y.Y. Gao, X.R. Chen, B. Liao, X.B. Ding, Z.H. Zheng, X. Cheng, H. Pang, Y.X. Peng, Polym. Bull. 56 (2006) 305.
Contents lists available at ScienceDirect
Materials Science and Engineering C j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m s e c
Chitosan/“angico” gum nanoparticles: Synthesis and characterization Marilia A. Oliveira a, Priscila C. Ciarlini b, Judith P.A. Feitosa a, Regina C.M. de Paula a, Haroldo C.B. Paula b,⁎ a b
Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará – C. Postal 6021, 60.455-760, Fortaleza, CE, Brazil Departamento de Química Analítica e Físico-Química, Universidade Federal do Ceará-C. Postal 6021, 60.455-760, Fortaleza, CE, Brazil
a r t i c l e
i n f o
Article history: Received 6 June 2008 Received in revised form 28 August 2008 Accepted 30 August 2008 Available online 9 September 2008 Keywords: Nanoparticles Polyelectrolyte Chitosan Anadenanthera macrocarpa gum
a b s t r a c t Polyelectrolyte complex nanoparticles from chitosan (CH) and “angico” gum (AG) were synthesized with average particle size ranging from 18 to 33 nm and monomodal volume distribution. The effect of polymer concentration on particle size and stability was investigated. No flocculation was observed in the range of particle charge ratio (n+/n−) studied. When the same chitosan and “angico” gum solution concentration was used, the higher the polymer concentration, the smaller the particle size. AG/CH nanoparticles were stable for a storage time up to 26 days. By keeping the CH solution concentration at 10 g l− 1 and increasing the AG solution concentration from 0.25 to 10 g l− 1, reduction in particle size was observed for the n+/n− ratios of 0.1, 1.0 and 10. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Polyelctrolyte complexes (PEC) result from the interaction of oppositely charged polymers. PEC can be obtained as a precipitate, turbid colloidal system and also as homogeneous soluble systems, where the particles are present in submicron-dimension [1–4]. Tsuchida and Abe [5] and Kabanov and Zezin [6] were the first authors to report on soluble nanoparticle polylectrolyte complexes from synthetic polymers, whereby the condition for producing nanoparticles was the presence of polyelectrolyte with weak ionic groups and a large difference in molar masses at a non-stoichiometric mixing ratio. Stabilized nanoparticles were obtained when the neutralized, hydrophobic core was surrounded by a shell of excess polyelectrolyte. Dautzemberg and co-workers [7–8] produced soluble PEC with nearly spherical shape using large molar mass and/or strong ion groups, but at very diluted system (b10− 4 g/ml). Schatz et al. [9–10] and Drogoz et al. [11] produced nanoparticles by polylectrolyte complexation based on biopolymers using chitosan as a polycation and dextran sulfate as a polyanion. Schatz and co-workers proposed different mechanisms for formation of stable nanoparticles based on the polymer in excess, polymer molar mass and flexibility of polymer chains. In the present work, the effect of polymer concentration on the formation of nanoparticle by polyelectrolyte complexation of chitosan and a branched slightly acidic polysaccharide, obtained by exudation of Anadenanthera macrocarpa trees (“angico” tree), was investigated. A. macrocarpa gum (AG) is a polysaccharide composed of arabinose (67%), galactose (24%), rhamnose (2%) and glucuronic acid (7%) [12]. ⁎ Corresponding author. Tel.: +55 85 3366 9961; fax: +55 85 3366 9982. E-mail address: [email protected] (H.C.B. Paula). 0928-4931/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2008.08.032
Molecular characteristics of the whole polysaccharide and its fractions obtained by fractional precipitation have been investigated by static light scattering, dilute solution viscometry and gel permeation chromatography (GPC). Hydrodynamic properties of polysaccharide fractions indicated a highly branched structure and a dependence of molar mass (M) on intrinsic viscosity [η], expressed by the equation: [η] = 0.0145 M0.44, with intrinsic viscosity giving in ml/g. The gum was found to have a broad molar mass distribution with M = 3.7 × 106 g/mol and [η] = 11 ml/g in 1 M NaCl at 25 °C [12]. A. macrocarpa gum was also carboxymethylated with monochloroacetic acid (MCA) in alkaline aqueous medium. The degree of substitution (DS) varied from 0.11 to 1.10 depending on NaOH concentration, MCA/AG ratio and temperature used in the synthesis [13]. 2. Experimental 2.1. Materials Crude polysaccharide samples were collected from A. macrocarpa native trees at Fortaleza, Ceará, Brazil. They were purified as a sodium salt using the method previously described [14]. Nodules free of bark were selected and dissolved in distilled water at room temperature to give a 5% (w/v) solution. The solution pH was adjusted to approximately 7.0 by addition of diluted aqueous NaOH. The clear solution was successively filtered through sintered glass and the purified polysaccharide precipitated with ethanol, after NaCl addition. Chitosan samples were donated by Polymar Ind. Com. Imp. Ltda (deacetylation degree 82%, Mv = 1.8 × 105 g/mol). Chitosan was used as a polycation for the preparation of polyelectrolyte complexes (PEC). Solutions of CH on the concentration range of
M.A. Oliveira et al. / Materials Science and Engineering C 29 (2009) 448–451
0.25 and 10 g l− 1 were prepared by dissolving the desired amount of chitosan in 1% acetic acid. The ionic strength was adjusted to 0.01 with NaCl. AG was used as a polyanion. Solutions of AG on the concentration range of 0.25 to 10 g l− 1 were prepared by dissolving the gum in bidistilled water and the ionic strength was adjusted to 0.01 with NaCl. Prior complex formation, the solutions (CH and AG) were filtered in a 0.22 μm Millipore filter. 2.2. Complex formation PEC were prepared by mixing AG to CH solution in appropriated proportions, in order to obtain a desired n+/n− molar ratio (molar charge ratio of CH and AG). The AG was added to CH with low stirring rate and the mixture was kept resting for 24 h before particle size measurement. The particle size of PEC dispersion was also monitored up to 26 days of storage time. 2.3. Characterization of angico gum and chitosan nanoparticle (AG/CH NP) 2.3.1. Particle size measurement Particle size measurements of AG/CH NP were carried out in a Nano zetasizer from Malvern, Model Zen 3500. All measurements were carried out using 30 scans with 30 s of acquisition time for each scan. 2.3.2. Infrared spectral analysis The IR spectra of the gum, chitosan and PEC were recorded in solid state in KBr pellets using a Shimadzu IR spectrophotometer (model 8300) operating between 400 and 4000 cm− 1.
449
3. Results and discussion AG is a high molar mass, low charged polysaccharide due the presence of glucuronic acid (7% w/w) [12]. Despite the low charge density, this polysaccharide exhibits a polyelectrolyte behavior [12]. Paula et al. [12] showed that at low salt concentration, such as 0.1 M NaCl, charges in AG polysaccharide were not screened, however by increasing the salt concentration to 1.0 M, linear plots in the light scattering experiments were obtained, indicating that the charges in the polysaccharide were screened. This unusual behavior for such low charge density polymer may point out to the fact that charges in AG gum chain are distributed such as in a micelle, where the charged monosaccharides are on the surface and the neutral monosaccharides are in the core of the micelle. Therefore it is expected that AG polysaccharide can complex with CH, forming stable nanoparticles (PEC). The volume distribution of PECs formed by the addition of AG solution at 0.25 g l− 1 to chitosan solution (0.25 g l− 1) at a n+/n− ratios of 0.1, 1 and 10 shows monomodal distributions (Fig. 1). Fig. 2 shows the effect of increasing both AG and CH polymer concentrations on particle size, a function of n+/n− ratio. A “U” shape curve was observed for n+/n− ratio between 0.1 and 0.6. This “U” shape behavior was also observed for PEC formed by chitosan and dextran sulfate in a n+/n− ratio of 0.1 and 0.7 [9–10]. Schatz et al. [9] proposed that by adding dextran sulfate to chitosan, where an excess of negative charges are present, colloidal stabilization occurs due the presence of residual anionic charge, leading to a decrease in particle size. As the n+/n− ratio increases, the free anionic charges are neutralized by chitosan and the particle tends to increase in size.
Fig. 1. Particle size distribution as a function of n+/n− charge ratio.
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M.A. Oliveira et al. / Materials Science and Engineering C 29 (2009) 448–451
Fig. 2. Effect of polymer concentration on particle size as a function of n+/n− ratio. (■) AG 0.25 g l− 1 and CH 0.25 g l− 1; (□) AG 10.0 g l− 1 and CH 10.0 g l− 1.
For AG/CH PEC at n+/n− ratio higher than 0.6, an increase in particle size is observed for both concentration. No flocculation was observed in the n+/n− range investigated. Flocculation occurred for complexation of dextran sulfate and chitosan in the n+/n− ratio close to 1 [9–10]. For PEC of dextran sulfate and chitosan, the range of n+/n− ratio where flocculation is observed depends on chitosan and dextran sulfate molar masses [9]. For those polymers, if the molar mass of chitosan is higher than the molar mass of dextran sulfate, flocculations occur in a wider range than if the dextran sulfate molar mass is higher than chitosan one. AG polysaccharide has a higher molar mass (3.7 × 106 g/ mol) and low charge density (7%, w/w) [12] than chitosan and those factors may be responsible for the absence of flocculation on AG/CH PEC. Similar behavior was also observed by adding a polyanion, such poly(maleic acid-co-propene) to polycation (polydiallyldimethyllammonium chloride) where no flocculation was observed for the n+/n− ratio ranging from 2.5 to 0.6 [1]. By increasing both AG and CH concentrations from 0.25 to 10 g l− 1 a decrease in particle size was observed. This data is different of that reported by Hajdu et al. [15] where an increase in particle size was observed when polymer concentrations increase. The effect of AG concentration, keeping CH at constant concentration (10 g l− 1), on particle size as a function of n+/n− ratio is depicted in Fig. 3. Three AG concentrations (0.1, 1.0 and 10 g l− 1) were used to investigate their effect on particle size. By increasing the AG concentration, a reduction in particle size was observed for all three n+/n− ratios. Keeping the AG concentration constant, small particle size was obtained for n+/n− ratio = 0.1, where an excess of negative charge is present.
Fig. 3. Effect of AG solution concentration, keeping CH solution concentration at 10.0 g l− 1, on particle size.
Fig. 4. Effect of storage time of CH/AG PEC at n+/n− charge ratio = 1 on particle size.
Particle size of AG/CH PEC produced at n+/n− ratio = 1.0 and CH and AG solution concentration of 0.25 g l− 1 were monitored for a period of 26 days (Fig. 4). A slight decrease on particle size on the first 5 days was observed followed by a stabilization of particle size. The average particle size in this period of time is almost constant (20.5 ± 1.7 nm). FT-IR spectroscopic analysis of AG, CH and PEC is shown in Fig. 5. The gum showed a broad band at 3379 cm− 1 due to the stretching vibration of O–H, a small peak at 2933 cm− 1, attributed to the C–H stretching vibration, and absorption at 1649 cm− 1, due to O–H scissor vibrations from bound water molecules [16]. Strong peaks at 1150, 1080 and 1030 cm− 1 are due to stretching vibrations of C–O–C from
Fig. 5. FT-IR spectrum of “angico” gum, chitosan and CH/AG PEC nanoparticle.
M.A. Oliveira et al. / Materials Science and Engineering C 29 (2009) 448–451
glucosidic bonds and O–H bending of alcohols. Specific bands for chitosan at 1652 and 1570 cm− 1 corresponding respectively to amide I and NH+3 deformations, as shown in Fig. 5. Most signal characteristics of both AG and CH were overlapped, however, upon complexation, a small change in the value of the assignments and a sharp increase in signal at 1564 cm− 1 characteristic of amine group can be clearly seen, which has been assigned as being due to AG carboxylated groups and CH amine groups interactions. This feature was also observed by Gao et al. [17]. 4. Conclusions CH/AG nanoparticles with narrow volume distributions and sizes in the range from 18 to 33 nm were successfully prepared. Unlike other polysaccharides, data obtained revealed that by increasing both polyanion and polycation concentrations up to 10 g l− 1, a decrease in particle size was observed. Those characteristics, as well as the fact that nanoparticles were shown to be stable for a storage time of up to 26 days, make the system a good candidate for drug delivery applications. Acknowledgement The authors gratefully acknowledge financial support from Rede Nanoglicobiotec/CNPq.
451
References [1] H.-M. Buchhammer, M. Mende, M. Oelmann, Colloids Surf., A 218 (2003) 151. [2] B. Philipp, H. dauzenberg, K.J. Linow, J. Koetz, W. Dawydoff, Prog. Polym. Sci. 14 (1989) 91. [3] Q. Wang, Y. Dan, X.G. Wang, J.M.S- Pure Appl. Chem. A34 (1997) 1155. [4] L.M. Zhang, S.L. Huang, Polym. Int. 49 (2000) 528. [5] E. Tsuchida, K. Abe, Interaction between Macromolecules in Solution and Intermacromolecular Complexes (Chap.1), verlag, Berlin, 1981. [6] V.A. Kabanov, A.B. Zezin, Makromol. Chem. (suppl. 6) (1984) 259. [7] H. Dautzemberg, N. Karibyants, N, Macromol. Chem. Phys. 200 (1999) 118. [8] H. Dautzemberg, W. Jaeger, Macromol. Chem. Phys. 203 (2002) 2095. [9] C. Schatz, A. Domard, C. Viton, C. Pichot, T. Delair, Biomacromolecules 5 (2004) 1882. [10] C. Schatz, A. Bionaz, J.M. Lucas, C. Pichot, C. Viton, A. Domart, T. Delair, Biomacromolecules 6 (2005) 1642. [11] A. Drogoz, L. David, C. Rochas, A. Domard, T. Delair, Langmuir 23 (2007) 10950. [12] R.C.M. de Paula, P.M. Budd, J.F. Rodrigues, Polym. Int. 44 (1997) 55. [13] M.A. Oliveira, D.A. Silva, D.E. Uchoa, J.S. Maciel, J.P.A. Feitosa, H.C.B. Paula, R.C.M. de Paula, J. Appl. Polym. Sci. 103 (2007) 2985. [14] R.C.M. de Paula, S.A. Santana, J.F. Rodrigues, Carbohydr. Polym. 44 (2001) 133. [15] I. Hadju, M. Bodnár, G. Filipesei, J.F. Hartmann, L. Daróczi, M. Zrínyi, J. Borbély, Colloid Polym. Sci. 286 (2008) 343. [16] M.J. Zohuriaan, F. Shokrolahi, Polym. Test. 23 (2004) 575. [17] Y.Y. Gao, X.R. Chen, B. Liao, X.B. Ding, Z.H. Zheng, X. Cheng, H. Pang, Y.X. Peng, Polym. Bull. 56 (2006) 305.