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Modulation of Silica Nanoparticle Uptake into Human Osteoblast Cells by Variation of the Ratio of Amino and Sulfonate Surface Groups: Effects of Serum.

Shahabi S, Treccani L, Dringen R, Rezwan K - ACS Appl Mater Interfaces (2015)

Bottom Line: Irrespective of the original surface charge, serum proteins adsorbed onto the surface, neutralized the zeta potential values, and prevented the aggregation of the tailor-made FFSNPs.In contrast, in serum-containing medium, anionic FFSNPs were internalized by HOB cells more strongly, despite the similar size and surface charge of all types of protein-covered FFSNPs.Thus, at physiological condition, when the presence of proteins is inevitable, sulfonate-functionalized silica NPs are the favorite choice to achieve a desired high rate of NP internalization.

View Article: PubMed Central - PubMed

Affiliation: †Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, 28359 Bremen, Germany.

ABSTRACT
To study the importance of the surface charge for cellular uptake of silica nanoparticles (NPs), we synthesized five different single- or multifunctionalized fluorescent silica NPs (FFSNPs) by introducing various ratios of amino and sulfonate groups into their surface. The zeta potential values of these FFSNPs were customized from highly positive to highly negative, while other physicochemical properties remained almost constant. Irrespective of the original surface charge, serum proteins adsorbed onto the surface, neutralized the zeta potential values, and prevented the aggregation of the tailor-made FFSNPs. Depending on the surface charge and on the absence or presence of serum, two opposite trends were found concerning the cellular uptake of FFSNPs. In the absence of serum, positively charged NPs were more strongly accumulated by human osteoblast (HOB) cells than negatively charged NPs. In contrast, in serum-containing medium, anionic FFSNPs were internalized by HOB cells more strongly, despite the similar size and surface charge of all types of protein-covered FFSNPs. Thus, at physiological condition, when the presence of proteins is inevitable, sulfonate-functionalized silica NPs are the favorite choice to achieve a desired high rate of NP internalization.

No MeSH data available.


Related in: MedlinePlus

Fluorescenceintensity of cellular FFSNPs after incubation of HOB cells with 100μg/mL of the FFSNPs for the indicated incubation times in serum-free(a) or in serum-supplemented medium (b). Cell viability measured bythe WST-1 assay after incubation in medium without (c) or with FCS(d). The data are given as the percentage of the control (cells incubatedwithout NPs). Extracellular LDH activity (given as percent of totalLDH in cells and media) released from HOBs after exposure to FFSNPsin serum-free (e) or serum-containing medium (f). All data are expressedas mean ± SD of values obtained in three independent experiments.In (c–f), asterisks (∗) indicate significant differencescompared to the control (p < 0.05).
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fig5: Fluorescenceintensity of cellular FFSNPs after incubation of HOB cells with 100μg/mL of the FFSNPs for the indicated incubation times in serum-free(a) or in serum-supplemented medium (b). Cell viability measured bythe WST-1 assay after incubation in medium without (c) or with FCS(d). The data are given as the percentage of the control (cells incubatedwithout NPs). Extracellular LDH activity (given as percent of totalLDH in cells and media) released from HOBs after exposure to FFSNPsin serum-free (e) or serum-containing medium (f). All data are expressedas mean ± SD of values obtained in three independent experiments.In (c–f), asterisks (∗) indicate significant differencescompared to the control (p < 0.05).

Mentions: Fluorescence microscopy revealed an intracellular presenceof all types of FFSNPs investigated in HOBs after exposure to theparticles in both serum-free and serum-containing incubation media(Figure 3). As a quantification of particleuptake from such images will not generate reliable data, uptake ofFFSNPs after application of 50 and 100 μg/mL into HOB cellswas quantified by determining cellular FFSNP fluorescence in a fluorimeterfor the cells harvested after the respective incubations (Figure S3a,b, Supporting Information, and Figure 5a,b). In serum-free medium, the uptake of positively chargedsilica NPs (100A and 75A + 25H) was significantly higher than thatof anionic and neutral NPs at all four exposure times (Figure S3a, Supporting Information, and Figure 5a). In contrast, higher amounts of cellular fluorescence wereobserved for cells that had been exposed in the presence of serumto anionic FFSNPs (100H and 25A + 75H) (Figure S3b, Supporting Information, and Figure 5b) compared to the other three types of particles (100A, 75H + 25Hand 50A + 50H). Statistical comparison of the results obtained forcells exposed to FFSNPs in the absence or presence of FCS (FigureS3a,b, Supporting Information, and Figure 5a,b) revealed significantly increased (p < 0.05) accumulation of the negatively charged (100H and 25A+ 75H) and neutral FFSNPs (50A + 50H) in the presence of serum. Incontrast, cellular uptake of the positively charged FFSNPs did notdiffer between incubations in the absence or the presence of serum.In addition, for serum-free conditions, hardly any increase in cellularFFSNP fluorescence was observed between 0.5 and 6 h of incubation,regardless of their surface charge (Figure S3a, Supporting Information, and Figure 5a), while in serum-containing medium the cellular fluorescence wasincreasing at least between the incubation periods of 0.5 and 2 h(Figure 5b).


Modulation of Silica Nanoparticle Uptake into Human Osteoblast Cells by Variation of the Ratio of Amino and Sulfonate Surface Groups: Effects of Serum.

Shahabi S, Treccani L, Dringen R, Rezwan K - ACS Appl Mater Interfaces (2015)

Fluorescenceintensity of cellular FFSNPs after incubation of HOB cells with 100μg/mL of the FFSNPs for the indicated incubation times in serum-free(a) or in serum-supplemented medium (b). Cell viability measured bythe WST-1 assay after incubation in medium without (c) or with FCS(d). The data are given as the percentage of the control (cells incubatedwithout NPs). Extracellular LDH activity (given as percent of totalLDH in cells and media) released from HOBs after exposure to FFSNPsin serum-free (e) or serum-containing medium (f). All data are expressedas mean ± SD of values obtained in three independent experiments.In (c–f), asterisks (∗) indicate significant differencescompared to the control (p < 0.05).
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Related In: Results  -  Collection

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fig5: Fluorescenceintensity of cellular FFSNPs after incubation of HOB cells with 100μg/mL of the FFSNPs for the indicated incubation times in serum-free(a) or in serum-supplemented medium (b). Cell viability measured bythe WST-1 assay after incubation in medium without (c) or with FCS(d). The data are given as the percentage of the control (cells incubatedwithout NPs). Extracellular LDH activity (given as percent of totalLDH in cells and media) released from HOBs after exposure to FFSNPsin serum-free (e) or serum-containing medium (f). All data are expressedas mean ± SD of values obtained in three independent experiments.In (c–f), asterisks (∗) indicate significant differencescompared to the control (p < 0.05).
Mentions: Fluorescence microscopy revealed an intracellular presenceof all types of FFSNPs investigated in HOBs after exposure to theparticles in both serum-free and serum-containing incubation media(Figure 3). As a quantification of particleuptake from such images will not generate reliable data, uptake ofFFSNPs after application of 50 and 100 μg/mL into HOB cellswas quantified by determining cellular FFSNP fluorescence in a fluorimeterfor the cells harvested after the respective incubations (Figure S3a,b, Supporting Information, and Figure 5a,b). In serum-free medium, the uptake of positively chargedsilica NPs (100A and 75A + 25H) was significantly higher than thatof anionic and neutral NPs at all four exposure times (Figure S3a, Supporting Information, and Figure 5a). In contrast, higher amounts of cellular fluorescence wereobserved for cells that had been exposed in the presence of serumto anionic FFSNPs (100H and 25A + 75H) (Figure S3b, Supporting Information, and Figure 5b) compared to the other three types of particles (100A, 75H + 25Hand 50A + 50H). Statistical comparison of the results obtained forcells exposed to FFSNPs in the absence or presence of FCS (FigureS3a,b, Supporting Information, and Figure 5a,b) revealed significantly increased (p < 0.05) accumulation of the negatively charged (100H and 25A+ 75H) and neutral FFSNPs (50A + 50H) in the presence of serum. Incontrast, cellular uptake of the positively charged FFSNPs did notdiffer between incubations in the absence or the presence of serum.In addition, for serum-free conditions, hardly any increase in cellularFFSNP fluorescence was observed between 0.5 and 6 h of incubation,regardless of their surface charge (Figure S3a, Supporting Information, and Figure 5a), while in serum-containing medium the cellular fluorescence wasincreasing at least between the incubation periods of 0.5 and 2 h(Figure 5b).

Bottom Line: Irrespective of the original surface charge, serum proteins adsorbed onto the surface, neutralized the zeta potential values, and prevented the aggregation of the tailor-made FFSNPs.In contrast, in serum-containing medium, anionic FFSNPs were internalized by HOB cells more strongly, despite the similar size and surface charge of all types of protein-covered FFSNPs.Thus, at physiological condition, when the presence of proteins is inevitable, sulfonate-functionalized silica NPs are the favorite choice to achieve a desired high rate of NP internalization.

View Article: PubMed Central - PubMed

Affiliation: †Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, 28359 Bremen, Germany.

ABSTRACT
To study the importance of the surface charge for cellular uptake of silica nanoparticles (NPs), we synthesized five different single- or multifunctionalized fluorescent silica NPs (FFSNPs) by introducing various ratios of amino and sulfonate groups into their surface. The zeta potential values of these FFSNPs were customized from highly positive to highly negative, while other physicochemical properties remained almost constant. Irrespective of the original surface charge, serum proteins adsorbed onto the surface, neutralized the zeta potential values, and prevented the aggregation of the tailor-made FFSNPs. Depending on the surface charge and on the absence or presence of serum, two opposite trends were found concerning the cellular uptake of FFSNPs. In the absence of serum, positively charged NPs were more strongly accumulated by human osteoblast (HOB) cells than negatively charged NPs. In contrast, in serum-containing medium, anionic FFSNPs were internalized by HOB cells more strongly, despite the similar size and surface charge of all types of protein-covered FFSNPs. Thus, at physiological condition, when the presence of proteins is inevitable, sulfonate-functionalized silica NPs are the favorite choice to achieve a desired high rate of NP internalization.

No MeSH data available.


Related in: MedlinePlus