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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

Colocalizationof FFSNPs (100 μg/mL) and lysosome after a 6 h incubation inDMEM + FCS (10%) + AB/AM (1%) at 37 °C. The images in panels(a–e) represent the merged fluorescence signals recorded inthe green (cytoskeleton), blue (LysoTracker), and red (FFSNPs) channels.The micrographs in panels (f–o) show the overlay of LysoTrackerand FFSNPs. In (f–j), the LysoTracker is shown with its originalblue fluorescence; therefore, the overlay with FFSNPs is indicatedby a magenta color, whereas in panels (k–o), the LysoTrackeris presented with a pseudo green color, in order to demonstrate theoverlapping with red NPs, which is observable as a yellow color. Theoverlays of cellular fluorescences for LysoTracker and FFSNPs, asindicated by white arrows, demonstrate the accumulation of FFSNPsinside the endolysosomal compartment. The images in panels (p–t)present the fluorescence signal from the FFSNPs in the single redchannel. Scale bars: 100 μm.
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fig4: Colocalizationof FFSNPs (100 μg/mL) and lysosome after a 6 h incubation inDMEM + FCS (10%) + AB/AM (1%) at 37 °C. The images in panels(a–e) represent the merged fluorescence signals recorded inthe green (cytoskeleton), blue (LysoTracker), and red (FFSNPs) channels.The micrographs in panels (f–o) show the overlay of LysoTrackerand FFSNPs. In (f–j), the LysoTracker is shown with its originalblue fluorescence; therefore, the overlay with FFSNPs is indicatedby a magenta color, whereas in panels (k–o), the LysoTrackeris presented with a pseudo green color, in order to demonstrate theoverlapping with red NPs, which is observable as a yellow color. Theoverlays of cellular fluorescences for LysoTracker and FFSNPs, asindicated by white arrows, demonstrate the accumulation of FFSNPsinside the endolysosomal compartment. The images in panels (p–t)present the fluorescence signal from the FFSNPs in the single redchannel. Scale bars: 100 μm.

Mentions: To investigate a potential intracellular colocalizationof FFSNPs with lysosmes, after exposure with FFSNPs for 0.5, 2, 4,or 6 h, the lysosomes were specifically stained with LysoTracker.Fluorescence microscopy for FFSNPs, actin cytoskeletons, and lysosomalcomponents was performed with appropriate specific channels, whichdetect the emitted fluorescence light in the red, green, and bluecolors, respectively. Due to similarities in the results for the differentincubation periods investigated, only representative fluorescencemicroscopy images for 6 h incubations of the HOBs with FFSNPs (100μg/mL)in DMEM + FCS (10%) + AB/AM (1%) are presented (Figure 4). Panels (a–e) show merged images of signals fromthe three fluorescence microscope channels. The micrographs in panels(f–o) reveal the combination of fluorescences originated fromLysoTracker and FFSNPs. In panels (f–j), the stained lysosomesare shown with their original blue color which merged to magenta inthe overlay with red fluorescing FFSNPs. In order to clarify the overlappingof both colors and to simplify the image analysis for colocalizationstudies, pseudo micrographs were prepared, in which the lysosomeswere shown with pseudo green color allowing the observation of thecolocalization with yellow color (panels k–o). Colocalizationof fluorescences from LysoTracker and NPs (magenta in panels (f–j)and yellow in panels (k–o)), as indicated by white arrows,clearly demonstrate the intracellular accumulation of FFSNPs insidethe endolysosome compartment. Fluorescence from the single red channeldenotes FFSNPs in panels (p–t). Analogously, colocalizationstudies for all FFSNPs (100 μg/mL) were performed in DMEM +AB/AM (1%) and representative results for 6 h incubations are presentedin Figure S2, Supporting Information.


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)

Colocalizationof FFSNPs (100 μg/mL) and lysosome after a 6 h incubation inDMEM + FCS (10%) + AB/AM (1%) at 37 °C. The images in panels(a–e) represent the merged fluorescence signals recorded inthe green (cytoskeleton), blue (LysoTracker), and red (FFSNPs) channels.The micrographs in panels (f–o) show the overlay of LysoTrackerand FFSNPs. In (f–j), the LysoTracker is shown with its originalblue fluorescence; therefore, the overlay with FFSNPs is indicatedby a magenta color, whereas in panels (k–o), the LysoTrackeris presented with a pseudo green color, in order to demonstrate theoverlapping with red NPs, which is observable as a yellow color. Theoverlays of cellular fluorescences for LysoTracker and FFSNPs, asindicated by white arrows, demonstrate the accumulation of FFSNPsinside the endolysosomal compartment. The images in panels (p–t)present the fluorescence signal from the FFSNPs in the single redchannel. Scale bars: 100 μm.
© Copyright Policy - editor-choice
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490775&req=5

fig4: Colocalizationof FFSNPs (100 μg/mL) and lysosome after a 6 h incubation inDMEM + FCS (10%) + AB/AM (1%) at 37 °C. The images in panels(a–e) represent the merged fluorescence signals recorded inthe green (cytoskeleton), blue (LysoTracker), and red (FFSNPs) channels.The micrographs in panels (f–o) show the overlay of LysoTrackerand FFSNPs. In (f–j), the LysoTracker is shown with its originalblue fluorescence; therefore, the overlay with FFSNPs is indicatedby a magenta color, whereas in panels (k–o), the LysoTrackeris presented with a pseudo green color, in order to demonstrate theoverlapping with red NPs, which is observable as a yellow color. Theoverlays of cellular fluorescences for LysoTracker and FFSNPs, asindicated by white arrows, demonstrate the accumulation of FFSNPsinside the endolysosomal compartment. The images in panels (p–t)present the fluorescence signal from the FFSNPs in the single redchannel. Scale bars: 100 μm.
Mentions: To investigate a potential intracellular colocalizationof FFSNPs with lysosmes, after exposure with FFSNPs for 0.5, 2, 4,or 6 h, the lysosomes were specifically stained with LysoTracker.Fluorescence microscopy for FFSNPs, actin cytoskeletons, and lysosomalcomponents was performed with appropriate specific channels, whichdetect the emitted fluorescence light in the red, green, and bluecolors, respectively. Due to similarities in the results for the differentincubation periods investigated, only representative fluorescencemicroscopy images for 6 h incubations of the HOBs with FFSNPs (100μg/mL)in DMEM + FCS (10%) + AB/AM (1%) are presented (Figure 4). Panels (a–e) show merged images of signals fromthe three fluorescence microscope channels. The micrographs in panels(f–o) reveal the combination of fluorescences originated fromLysoTracker and FFSNPs. In panels (f–j), the stained lysosomesare shown with their original blue color which merged to magenta inthe overlay with red fluorescing FFSNPs. In order to clarify the overlappingof both colors and to simplify the image analysis for colocalizationstudies, pseudo micrographs were prepared, in which the lysosomeswere shown with pseudo green color allowing the observation of thecolocalization with yellow color (panels k–o). Colocalizationof fluorescences from LysoTracker and NPs (magenta in panels (f–j)and yellow in panels (k–o)), as indicated by white arrows,clearly demonstrate the intracellular accumulation of FFSNPs insidethe endolysosome compartment. Fluorescence from the single red channeldenotes FFSNPs in panels (p–t). Analogously, colocalizationstudies for all FFSNPs (100 μg/mL) were performed in DMEM +AB/AM (1%) and representative results for 6 h incubations are presentedin Figure S2, Supporting Information.

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