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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.


Suggested schematic illustration of the interaction between the silica nanoparticles and the amino acids.
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f7-ijn-9-029: Suggested schematic illustration of the interaction between the silica nanoparticles and the amino acids.

Mentions: As shown in Figure 3, the L-ser coated silica nanoparticles showed an increase in zeta potential even though L-ser was in neutral zwitterionic form at pH 5.5–6.5. Some L-ser moieties can directly coordinate with the silicon atoms through the exposed carboxylate groups while much of the L-ser interacts via electrostatic interaction between the negative silica surface and the positive ammonium group (Figure 7).47 L-ser, however, does not have a strong cationic center, and thus, the zeta potential increase was quite limited. On the other hand, L-his and L-arg, which had additional cationic centers (imidazolium and guanidinium, respectively), showed clear zeta potential increases of 15–20 mV in the 5.5–6.5 pH range. The pKa values of imidazolium and guanidinium revealed that both amino acids had obvious positive charges at the above pH region, resulting in an increase in the zeta potential of the colloidal silica. The interaction between the positive centers of the coated amino acids with the neighboring silica particles, however, could be accelerated, giving rise to the formation of agglomeration or gelation, according to the coating conditions, such as the type of amino acid used for coating, the pH, and the amount of coating materials used (Figure 4B and D, Table 1). Taking into account all the coating experiment results of the three amino acids, the optimal candidate, which showed not only a clear increase in zeta potential (difference of approximately 15 mV) but also colloidal stability, was L-arg.


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)

Suggested schematic illustration of the interaction between the silica nanoparticles and the amino acids.
© Copyright Policy
Related In: Results  -  Collection

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

f7-ijn-9-029: Suggested schematic illustration of the interaction between the silica nanoparticles and the amino acids.
Mentions: As shown in Figure 3, the L-ser coated silica nanoparticles showed an increase in zeta potential even though L-ser was in neutral zwitterionic form at pH 5.5–6.5. Some L-ser moieties can directly coordinate with the silicon atoms through the exposed carboxylate groups while much of the L-ser interacts via electrostatic interaction between the negative silica surface and the positive ammonium group (Figure 7).47 L-ser, however, does not have a strong cationic center, and thus, the zeta potential increase was quite limited. On the other hand, L-his and L-arg, which had additional cationic centers (imidazolium and guanidinium, respectively), showed clear zeta potential increases of 15–20 mV in the 5.5–6.5 pH range. The pKa values of imidazolium and guanidinium revealed that both amino acids had obvious positive charges at the above pH region, resulting in an increase in the zeta potential of the colloidal silica. The interaction between the positive centers of the coated amino acids with the neighboring silica particles, however, could be accelerated, giving rise to the formation of agglomeration or gelation, according to the coating conditions, such as the type of amino acid used for coating, the pH, and the amount of coating materials used (Figure 4B and D, Table 1). Taking into account all the coating experiment results of the three amino acids, the optimal candidate, which showed not only a clear increase in zeta potential (difference of approximately 15 mV) but also colloidal stability, was L-arg.

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.