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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.


Time dependent turbidity of silica nanoparticles coated with L-arginine.Notes: (A) Silica nanoparticles with 20 nm diameter and (B) hydrodynamic size of colloidal silica nanoparticles with 100 nm diameter at pH (a) 5.5, (b) 6.0, and (c) 6.5 depending on the time. The measurement data for 48 hours are represented by arrows. Gradations in color from dark grey (0 hours) to black (48 hours).
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f6-ijn-9-029: Time dependent turbidity of silica nanoparticles coated with L-arginine.Notes: (A) Silica nanoparticles with 20 nm diameter and (B) hydrodynamic size of colloidal silica nanoparticles with 100 nm diameter at pH (a) 5.5, (b) 6.0, and (c) 6.5 depending on the time. The measurement data for 48 hours are represented by arrows. Gradations in color from dark grey (0 hours) to black (48 hours).

Mentions: To evaluate in detail the colloidal stability of colloidal silica upon L-arg coating, the time dependent turbidity was measured utilizing the Turbiscan™ apparatus.34–39Figure 6 shows the time dependent backscattering difference between the L-arg coated silicas and noncoated silicas at pH 5.5, 6.0, and 6.5 for 48 hours. Turbiscan™ measured the backscattered light (near infrared), which was irradiated to the colloidal sample placed in a 55 mm tall vial containing a colloidal sample. The x-axis of the graphs stands for the location where the backscattering occurred, and the y-axis indicates the difference between the backscattered light before and after coating. The measurements were carried out every 1.5 hours for 48 hours, and all the graphs were reflected on one sheet, with the changing pattern indicated with arrows in Figure 6. The SiO2EN20(R) at pH 5.5 showed an increase in backscattering in the lower (height: 0–5 mm) and upper (height: 50–55 mm) parts of the vial, and a decrease in backscattering in the middle part (height: 5–50 mm) of the vial (Figure 6A). Generally, the enhancement in backscattering is attributed to the increase in particle size or number resulting from flocculation or particle migration. Similarly, the decrease in backscattering is related to the reduced size or particle number. Therefore, it was considered that the 20 nm colloidal silica particles flocculated to a certain degree and migrated to a lower or higher position. These results corresponded well with the particle size increase of SiO2EN20(−) after L-arg coating at pH 5.5, which was measured by dynamic light scattering (Figure 5B). On the other hand, no significant backscattering change was observed in SiO2EN20(R) at pH 6.0 and 6.5, which indicates that the colloid was stably preserved under such coating conditions (Figure 6A). SiO2EN100(−) showed a similar time dependent backscattering change pattern upon L-arg coating regardless of the pH condition. It exhibited a backscattering increase in the lower (height: 0–5 mm) region and a decrease in the upper (height: 50–55 mm) region at all the pH conditions tested while there was almost no change in backscattering in the middle region (height: 5–50 mm) of the vial (arrows in Figure 6). These results signify possible sedimentation; however, the colloidal solution exhibited sufficient stability in accordance with previous reports.34–38


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)

Time dependent turbidity of silica nanoparticles coated with L-arginine.Notes: (A) Silica nanoparticles with 20 nm diameter and (B) hydrodynamic size of colloidal silica nanoparticles with 100 nm diameter at pH (a) 5.5, (b) 6.0, and (c) 6.5 depending on the time. The measurement data for 48 hours are represented by arrows. Gradations in color from dark grey (0 hours) to black (48 hours).
© Copyright Policy
Related In: Results  -  Collection

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

f6-ijn-9-029: Time dependent turbidity of silica nanoparticles coated with L-arginine.Notes: (A) Silica nanoparticles with 20 nm diameter and (B) hydrodynamic size of colloidal silica nanoparticles with 100 nm diameter at pH (a) 5.5, (b) 6.0, and (c) 6.5 depending on the time. The measurement data for 48 hours are represented by arrows. Gradations in color from dark grey (0 hours) to black (48 hours).
Mentions: To evaluate in detail the colloidal stability of colloidal silica upon L-arg coating, the time dependent turbidity was measured utilizing the Turbiscan™ apparatus.34–39Figure 6 shows the time dependent backscattering difference between the L-arg coated silicas and noncoated silicas at pH 5.5, 6.0, and 6.5 for 48 hours. Turbiscan™ measured the backscattered light (near infrared), which was irradiated to the colloidal sample placed in a 55 mm tall vial containing a colloidal sample. The x-axis of the graphs stands for the location where the backscattering occurred, and the y-axis indicates the difference between the backscattered light before and after coating. The measurements were carried out every 1.5 hours for 48 hours, and all the graphs were reflected on one sheet, with the changing pattern indicated with arrows in Figure 6. The SiO2EN20(R) at pH 5.5 showed an increase in backscattering in the lower (height: 0–5 mm) and upper (height: 50–55 mm) parts of the vial, and a decrease in backscattering in the middle part (height: 5–50 mm) of the vial (Figure 6A). Generally, the enhancement in backscattering is attributed to the increase in particle size or number resulting from flocculation or particle migration. Similarly, the decrease in backscattering is related to the reduced size or particle number. Therefore, it was considered that the 20 nm colloidal silica particles flocculated to a certain degree and migrated to a lower or higher position. These results corresponded well with the particle size increase of SiO2EN20(−) after L-arg coating at pH 5.5, which was measured by dynamic light scattering (Figure 5B). On the other hand, no significant backscattering change was observed in SiO2EN20(R) at pH 6.0 and 6.5, which indicates that the colloid was stably preserved under such coating conditions (Figure 6A). SiO2EN100(−) showed a similar time dependent backscattering change pattern upon L-arg coating regardless of the pH condition. It exhibited a backscattering increase in the lower (height: 0–5 mm) region and a decrease in the upper (height: 50–55 mm) region at all the pH conditions tested while there was almost no change in backscattering in the middle region (height: 5–50 mm) of the vial (arrows in Figure 6). These results signify possible sedimentation; however, the colloidal solution exhibited sufficient stability in accordance with previous reports.34–38

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.