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

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

Interaction of the Physiological Tripeptide Glutathione with Colloidal Alumina Particles

Understanding of the molecular interactions of alumina particles with biomolecules is fundamental for a variety of biotechnological processes. To study the interactions of polypeptides with alumina particles, we have investigated the adsorption and desorption behavior of the physiologically relevant tripeptide glutathione (GSH, γ-glutamylcysteinylglycine) onto colloidal α-alumina particles (CPs). The adsorption of GSH to positively charged alumina particles was rapid, increased proportionally to the concentration of CPs, and shifted the isoelectric point of the CP to a less alcaline pH. Desorption of particle-bound GSH was achieved by increasing the ionic strength after adding salt to the suspension, suggesting that adsorption of GSH to alumina is governed by electrostatic interactions. The presence of negatively charged and GSH-structurally related molecules such as glutamate, γ-glutamylcysteine, γ-glutamylglutamate, or methyl-S-GSH prevented the binding of GSH to the positively charged alumina surface in a concentration dependent manner, while positively charged and net-uncharged molecules and GSH esters did not affect GSH adsorption to alumina CPs. These data suggest that exclusively electrostatic interaction via the carboxylate groups of GSH governs its binding to alumina particles

Enhancing Cellular Uptake and Doxorubicin Delivery of Mesoporous Silica Nanoparticles via Surface Functionalization: Effects of Serum

In this study, we demonstrate how functional groups on the surface of mesoporous silica nanoparticles (MSNPs) can influence the encapsulation and release of the anticancer drug doxorubicin, as well as cancer cell response in the absence or presence of serum proteins. To this end, we synthesized four differently functionalized MSNPs with amine, sulfonate, polyethylene glycol, or polyethylene imine functional surface groups, as well as one type of antibody-conjugated MSNP for specific cellular targeting, and we characterized these MSNPs regarding their physicochemical properties, colloidal stability in physiological media, and uptake and release of doxorubicin <i>in vitro</i>. Then, the MSNPs were investigated for their cytotoxic potential on cancer cells. Cationic MSNPs could not be loaded with doxorubicin and did therefore not show any cytotoxic and antiproliferative potential on osteosarcoma cells, although they were efficiently taken up into the cells in the presence or absence of serum. In contrast, substantial amounts of doxorubicin were loaded into negatively charged and unfunctionalized MSNPs. Especially, sulfonate-functionalized doxorubicin-loaded MSNPs were efficiently taken up into the cells in the presence of serum and showed an accelerated toxic and antiproliferative potential compared to unfunctionalized MSNPs, antibody-conjugated MSNPs, and even free doxorubicin. These findings stress the high importance of the surface charge as well as of the protein corona for designing and applying nanoparticles for targeted drug delivery

Adsorption and Orientation of the Physiological Extracellular Peptide Glutathione Disulfide on Surface Functionalized Colloidal Alumina Particles

Understanding the interrelation between surface chemistry of colloidal particles and surface adsorption of biomolecules is a crucial prerequisite for the design of materials for biotechnological and nanomedical applications. Here, we elucidate how tailoring the surface chemistry of colloidal alumina particles (<i>d</i>₅₀ = 180 nm) with amino (−NH₂), carboxylate (−COOH), phosphate (−PO₃H₂) or sulfonate (−SO₃H) groups affects adsorption and orientation of the model peptide glutathione disulfide (GSSG). GSSG adsorbed on native, −NH₂-functionalized, and −SO₃H-functionalized alumina but not on −COOH- and −PO₃H₂-functionalized particles. When adsorption occurred, the process was rapid (≤5 min), reversible by application of salts, and followed a Langmuir adsorption isotherm dependent on the particle surface functionalization and ζ potential. The orientation of particle bound GSSG was assessed by the release of glutathione after reducing the GSSG disulfide bond and by ζ potential measurements. GSSG is likely to bind via the carboxylate groups of one of its two glutathionyl (GS) moieties onto native and −NH₂-modified alumina, whereas GSSG is suggested to bind to −SO₃H-modified alumina via the primary amino groups of both GS moieties. Thus, GSSG adsorption and orientation can be tailored by varying the molecular composition of the particle surface, demonstrating a step toward guiding interactions of biomolecules with colloidal particles

Expression of Hepatoma-derived growth factor family members in the adult central nervous system-5

<p><b>Copyright information:</b></p><p>Taken from "Expression of Hepatoma-derived growth factor family members in the adult central nervous system"</p><p>BMC Neuroscience 2006;7():6-6.</p><p>Published online 23 Jan 2006</p><p>PMCID:PMC1363353.</p><p>Copyright © 2006 El-Tahir et al; licensee BioMed Central Ltd.</p> an adult mouse. Comparison of the double immunfluorescence demonstrates the lack of expression of HRP-3 in cells covering the ventricel wall of the hippocampal region (C, arrow), whereas HDGF is clearly expressed in this cell type. In contrast, hippocampal neurons coexpress both family members, but whereas HDGF is found to a similar extent in all neurons of the hippocampal formation (A), neurons of the dentate gyrus show only weak expression of HRP-3 when compared to the rest of the hippocampus (B). Higher magnification of this region demonstrates the existence of cells predominantly expressing HRP-3 (D, arrowheads) as well as a cell layer only positive for HDGF (D, arrows). CA: cornu ammonis; Sub: subiculum; DG: dentate gyrus; Bar in C is 80 μm; bar in D is 40 μm

Expression of Hepatoma-derived growth factor family members in the adult central nervous system-7

<p><b>Copyright information:</b></p><p>Taken from "Expression of Hepatoma-derived growth factor family members in the adult central nervous system"</p><p>BMC Neuroscience 2006;7():6-6.</p><p>Published online 23 Jan 2006</p><p>PMCID:PMC1363353.</p><p>Copyright © 2006 El-Tahir et al; licensee BioMed Central Ltd.</p>um of an adult mouse. To label the nuclei of all cells in the sections counterstaining with propidium iodide was performed (B,C and E,F). Double stained sections were used to calculate the percentage of cells positive for HDGF or HRP-3, respectively. Whereas HDGF is expressed in all cells, HRP-3 expression is much more restricted (for details see text). Cells labeled with arrows in D represent HRP-3 positive Purkinje cells. Asterisks in E mark most likely radial glia cells. MCL: molecular cell layer; PCL: purkinje cell layer; IGL: internal granular cell layer; Bars are 25 μm

Expression of Hepatoma-derived growth factor family members in the adult central nervous system-1

<p><b>Copyright information:</b></p><p>Taken from "Expression of Hepatoma-derived growth factor family members in the adult central nervous system"</p><p>BMC Neuroscience 2006;7():6-6.</p><p>Published online 23 Jan 2006</p><p>PMCID:PMC1363353.</p><p>Copyright © 2006 El-Tahir et al; licensee BioMed Central Ltd.</p>teins in brain slices of adult mice. Double stainings demonstrate that in contrast to HDGF and HRP-2, HRP-3 is not expressed in NeuN positive granular cells of the cerebellum. Distinct cells in the IGL detected by HRP-3 antibodies are most likely Golgi cells (I, arrowheads). In addition HRP-3 is also clearly expressed in the PCL and weakly in some cells of the MCL (I). MCL: molecular cell layer; PCL: purkinje cell layer; IGL: internal granular cell layer; WM: white matter. Bars are 80 μm

Expression of Hepatoma-derived growth factor family members in the adult central nervous system-3

<p><b>Copyright information:</b></p><p>Taken from "Expression of Hepatoma-derived growth factor family members in the adult central nervous system"</p><p>BMC Neuroscience 2006;7():6-6.</p><p>Published online 23 Jan 2006</p><p>PMCID:PMC1363353.</p><p>Copyright © 2006 El-Tahir et al; licensee BioMed Central Ltd.</p>pective proteins in brain slices of adult mice. In all cases a part of the hippocampal region is shown. Double immunfluorescence demonstrates that HDGF (C, arrows) and HRP-2 (F, arrows) are expressed in cells positive for GFAP. In contrast no costaining of cells containing both GFAP as well as HRP-3 could be detected (I). Bars are 40 μm

Expression of Hepatoma-derived growth factor family members in the adult central nervous system-6

<p><b>Copyright information:</b></p><p>Taken from "Expression of Hepatoma-derived growth factor family members in the adult central nervous system"</p><p>BMC Neuroscience 2006;7():6-6.</p><p>Published online 23 Jan 2006</p><p>PMCID:PMC1363353.</p><p>Copyright © 2006 El-Tahir et al; licensee BioMed Central Ltd.</p>x and cerebellum of an adult mouse. Comparison of the double immunfluorescence demonstrates the lack of expression of HRP-3 in cells building the pia mater at the surface of the cortex (PM in C) and some cells in layer I (C, arrows), whereas cells in the rest of the cortex show a high degree of coexpression of HDGF and HRP-3. A lower degree of coexpression is found in the cerebellum, where HRP-3 family member is only expressed in Purkinje cells and Golgi cells of the IGL. Some of these HRP-3 positive cells do not (E+F, asterisks) and some do also express HDGF (D-F, arrowheads). PM: Pia Mater; I+II: layer I and II; EGL: external granular cell layer; MCL: molecular cell layer; PCL: purkinje cell layer; IGL: internal granular cell layer; WM: white matter. Bars are 40 μm

Expression of Hepatoma-derived growth factor family members in the adult central nervous system-0

<p><b>Copyright information:</b></p><p>Taken from "Expression of Hepatoma-derived growth factor family members in the adult central nervous system"</p><p>BMC Neuroscience 2006;7():6-6.</p><p>Published online 23 Jan 2006</p><p>PMCID:PMC1363353.</p><p>Copyright © 2006 El-Tahir et al; licensee BioMed Central Ltd.</p>methods and subjected to Western blot analysis with antibodies against the proteins listed. Brain regions examined were as indicated above the figure. The Coomassie stained PVDF membrane is shown underneath the figure to demonstrate equal loading for the different brain regions. Molecular weights of marker proteins in kiloDalton are given on the right side of the figure