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Surface treatment of silica nanoparticles for stable and charge-controlled colloidal silica.

Kim KM, Kim HM, Lee WJ, Lee CW, Kim TI, Lee JK, Jeong J, Paek SM, Oh JM - Int J Nanomedicine (2014)

Bottom Line: Amino acid coatings resulted in relatively stable silica colloids with a modified surface charge.The time dependent change in L-arginine coated colloidal silica was investigated by measuring the pattern of the backscattered light in a Turbiscan™.The results indicated that both the 20 nm and 100 nm L-arginine coated silica samples were fairly stable in terms of colloidal homogeneity, showing only slight coalescence and sedimentation.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Gangwon-do, Republic of Korea.

ABSTRACT
An attempt was made to control the surface charge of colloidal silica nanoparticles with 20 nm and 100 nm diameters. Untreated silica nanoparticles were determined to be highly negatively charged and have stable hydrodynamic sizes in a wide pH range. To change the surface to a positively charged form, various coating agents, such as amine containing molecules, multivalent metal cation, or amino acids, were used to treat the colloidal silica nanoparticles. Molecules with chelating amine sites were determined to have high affinity with the silica surface to make agglomerations or gel-like networks. Amino acid coatings resulted in relatively stable silica colloids with a modified surface charge. Three amino acid moiety coatings (L-serine, L-histidine, and L-arginine) exhibited surface charge modifying efficacy of L-histidine > L-arginine > L-serine and hydrodynamic size preservation efficacy of L-serine > L-arginine > L-histidine. The time dependent change in L-arginine coated colloidal silica was investigated by measuring the pattern of the backscattered light in a Turbiscan™. The results indicated that both the 20 nm and 100 nm L-arginine coated silica samples were fairly stable in terms of colloidal homogeneity, showing only slight coalescence and sedimentation.

No MeSH data available.


Chemical formula and positively charged groups of various coating reagents.Note: EUDRAGIT® E-100, Evonik Industries, Essen, Germany.Abbreviations: APTES, 3-aminopropyltriethoxysilane; EDA, ethylenediamine; TAEA, tris(2-aminoethyl)amine.
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f2-ijn-9-029: Chemical formula and positively charged groups of various coating reagents.Note: EUDRAGIT® E-100, Evonik Industries, Essen, Germany.Abbreviations: APTES, 3-aminopropyltriethoxysilane; EDA, ethylenediamine; TAEA, tris(2-aminoethyl)amine.

Mentions: To modify the surface charge of colloidal silica while maintaining particle size, coating experiments with various molecules were conducted (Figure 2), using established methodologies.26,33 Four different categories of coating reagents were utilized: amine containing molecules, multivalent metal cation, cationic polymers, and basic amino acids. All the coating agents had cationic centers to modify the highly negative surface charge of the silica nanoparticles. For the first step, the formation of gels that attributed to the strong interaction between the nanoparticles and the coating reagents were examined as the gelation indicated that the colloid had lost its stability.20 The results are summarized in Table 1. The degree of gelation was evaluated as the time required for complete gel formation after the addition of the coating agent to the colloidal silica while stirring. We determined that there was gelation when the inner substance of the colloid did not flow upon turning the container upside down. EDA, a divalent amine chelate, showed concentration dependent gelation upon mixing with colloidal silica, exhibiting immediate gelation in a high EDA concentration. TAEA, a tetravalent amine chelate, resulted in relatively rapid gelation compared with EDA, resulting in an immediate gelation even at a very low concentration (0.03 wt/v%). The APTES reagent, which together had an amine and silane moiety, also resulted in gelation within 2 hours. The gelation of colloidal silica was more accelerated with the multivalent metal cation Al3+, showing immediate gelation at a very low concentration (0.01 wt/v%). EUDRAGIT® E-100, a methacrylate based copolymer generally utilized for medical purposes, also showed gradual gelation when mixed with colloidal silica. Basic amino acids like L-ser, L-his, and L-arg also showed gelation according to increasing concentrations of silica and amino acids. Optimal conditions for amino acid coating were found by adjusting the concentrations and reaction ratios and observing the degree or absence of coagulation over a 48 hour period. The 3–10 wt/v% colloidal silica samples maintained their sol-like colloidal states with the addition of 0.3–1.0 wt/v% amino acids. The result shown in Table 1 is for SiO2EN20(−), but a similar gelation pattern was obtained with SiO2EN100(−).


Surface treatment of silica nanoparticles for stable and charge-controlled colloidal silica.

Kim KM, Kim HM, Lee WJ, Lee CW, Kim TI, Lee JK, Jeong J, Paek SM, Oh JM - Int J Nanomedicine (2014)

Chemical formula and positively charged groups of various coating reagents.Note: EUDRAGIT® E-100, Evonik Industries, Essen, Germany.Abbreviations: APTES, 3-aminopropyltriethoxysilane; EDA, ethylenediamine; TAEA, tris(2-aminoethyl)amine.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4279762&req=5

f2-ijn-9-029: Chemical formula and positively charged groups of various coating reagents.Note: EUDRAGIT® E-100, Evonik Industries, Essen, Germany.Abbreviations: APTES, 3-aminopropyltriethoxysilane; EDA, ethylenediamine; TAEA, tris(2-aminoethyl)amine.
Mentions: To modify the surface charge of colloidal silica while maintaining particle size, coating experiments with various molecules were conducted (Figure 2), using established methodologies.26,33 Four different categories of coating reagents were utilized: amine containing molecules, multivalent metal cation, cationic polymers, and basic amino acids. All the coating agents had cationic centers to modify the highly negative surface charge of the silica nanoparticles. For the first step, the formation of gels that attributed to the strong interaction between the nanoparticles and the coating reagents were examined as the gelation indicated that the colloid had lost its stability.20 The results are summarized in Table 1. The degree of gelation was evaluated as the time required for complete gel formation after the addition of the coating agent to the colloidal silica while stirring. We determined that there was gelation when the inner substance of the colloid did not flow upon turning the container upside down. EDA, a divalent amine chelate, showed concentration dependent gelation upon mixing with colloidal silica, exhibiting immediate gelation in a high EDA concentration. TAEA, a tetravalent amine chelate, resulted in relatively rapid gelation compared with EDA, resulting in an immediate gelation even at a very low concentration (0.03 wt/v%). The APTES reagent, which together had an amine and silane moiety, also resulted in gelation within 2 hours. The gelation of colloidal silica was more accelerated with the multivalent metal cation Al3+, showing immediate gelation at a very low concentration (0.01 wt/v%). EUDRAGIT® E-100, a methacrylate based copolymer generally utilized for medical purposes, also showed gradual gelation when mixed with colloidal silica. Basic amino acids like L-ser, L-his, and L-arg also showed gelation according to increasing concentrations of silica and amino acids. Optimal conditions for amino acid coating were found by adjusting the concentrations and reaction ratios and observing the degree or absence of coagulation over a 48 hour period. The 3–10 wt/v% colloidal silica samples maintained their sol-like colloidal states with the addition of 0.3–1.0 wt/v% amino acids. The result shown in Table 1 is for SiO2EN20(−), but a similar gelation pattern was obtained with SiO2EN100(−).

Bottom Line: Amino acid coatings resulted in relatively stable silica colloids with a modified surface charge.The time dependent change in L-arginine coated colloidal silica was investigated by measuring the pattern of the backscattered light in a Turbiscan™.The results indicated that both the 20 nm and 100 nm L-arginine coated silica samples were fairly stable in terms of colloidal homogeneity, showing only slight coalescence and sedimentation.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Gangwon-do, Republic of Korea.

ABSTRACT
An attempt was made to control the surface charge of colloidal silica nanoparticles with 20 nm and 100 nm diameters. Untreated silica nanoparticles were determined to be highly negatively charged and have stable hydrodynamic sizes in a wide pH range. To change the surface to a positively charged form, various coating agents, such as amine containing molecules, multivalent metal cation, or amino acids, were used to treat the colloidal silica nanoparticles. Molecules with chelating amine sites were determined to have high affinity with the silica surface to make agglomerations or gel-like networks. Amino acid coatings resulted in relatively stable silica colloids with a modified surface charge. Three amino acid moiety coatings (L-serine, L-histidine, and L-arginine) exhibited surface charge modifying efficacy of L-histidine > L-arginine > L-serine and hydrodynamic size preservation efficacy of L-serine > L-arginine > L-histidine. The time dependent change in L-arginine coated colloidal silica was investigated by measuring the pattern of the backscattered light in a Turbiscan™. The results indicated that both the 20 nm and 100 nm L-arginine coated silica samples were fairly stable in terms of colloidal homogeneity, showing only slight coalescence and sedimentation.

No MeSH data available.