Uptake of silica-coated nanoparticles by HeLa cells

Nanoparticles have seen wide applications in cellular research and development. One major issue that is unclear is the uptake of nanoparticles by cells. In this study, we have investigated the uptake of silica-coated nanoparticles by HeLa cells, employing rhoadime 6G isothiocyanate (RITC)-doped nanoparticles as a synchronous fluorescent signal indicator. These nanoparticles were synthesized with reverse microemulsion. A few factors, such as nanoparticle concentration, incubation time and temperature, and serum and inhibitors in culture medium were assessed on the nanoparticle's cellular uptake. The experimental results demonstrated that uptake was maximum after a 6 h incubation and was higher at 37 degrees C than that at 4 degrees C. Nanoparticle uptake depended on the nanoparticle concentration and was inhibited by hyperosmolarity, K+ depletion. In addition, serum in culture medium decreased the cellular uptake of nanoparticles. The results indicated that the uptake of silica-coated nanoparticles by HeLa cells was a concentration-, time-, and energy-dependent endocytic process. Silica-coated nanoparticles could be transported into HeLa cells in part through adsorptive endocytosis and in part through fluid-phase endocytosis.     

Flow Rate Affects Nanoparticle Uptake into Endothelial Cells

Nanoparticles are commonly administered through systemic injection, which exposes them to the dynamic environment of the bloodstream. Injected nanoparticles travel within the blood and experience a wide range of flow velocities that induce varying shear rates to the blood vessels. Endothelial cells line these vessels, and have been shown to uptake nanoparticles during circulation, but it is difficult to characterize the flow-dependence of this interaction in vivo. Here, a microfluidic system is developed to control the flow rates of nanoparticles as they interact with endothelial cells. Gold nanoparticle uptake into endothelial cells is quantified at varying flow rates, and it is found that increased flow rates lead to decreased nanoparticle uptake. Endothelial cells respond to increased flow shear with decreased ability to uptake the nanoparticles. If cells are sheared the same way, nanoparticle uptake decreases as their flow velocity increases. Modifying nanoparticle surfaces with endothelial-cell-binding ligands partially restores uptake to nonflow levels, suggesting that functionalizing nanoparticles to bind to endothelial cells enables nanoparticles to resist flow effects. In the future, this microfluidic system can be used to test other nanoparticle–endothelial cell interactions under flow. The results of these studies can guide the engineering of nanoparticles for in vivo medical applications.     

Uptake of Cyclopentane Vapours in a Fullerite Powder

The isotherms of cyclopentane uptake in fullerite exhibit hysteresis which persists to low equilibrium pressures. Between 269.4 and 273.2 K a jump in the amount of cyclopentane retained in fullerite was observed.     

Physical Characterization and Macrophage Cell Uptake of Mannan-Coated Nanoparticles

Abstract

Previously, we reported on a cationic nanoparticle-based DNA vaccine delivery system engineered from warm oil-in-water microemulsion precursors. In these present studies, the feasibility of lyophilizing the nanoparticles and their thermal properties were investigated. Also, the binding and uptake of the nanoparticles by a macrophage cell line were studied. The nanoparticles (prior to pDNA coating) were freeze-dried with lactose or sucrose as cryoprotectants. The stability of lyophilized nanoparticles at room temperature was monitored and compared to that of the aqueous nanoparticle suspension. The thermal properties of the nanoparticles were investigated using differential scanning calorimetry (DSC). The nanoparticles, coated or uncoated with mannan as a ligand, were incubated with a mannose receptor positive (MR+) mouse macrophage cell line (J774E), at either 4°C or 37°C to study the binding and uptake of the nanoparticles by the cells. It was found that lactose or sucrose (1–5%, w/v) was required for successful lyophilization of the nanoparticles. After 4 months of storage, the size of lyophilized nanoparticles did not significantly increase while those in aqueous suspension grew by over 900%. Unlike its individual components, emulsifying wax (m.p., ?55°C) and hexadecyltrimethyl ammonium bromide, the nanoparticles showed a melting point of ?90°C. Moreover, the DSC profile of the nanoparticles was different from that of the physical mixture of emulsifying wax and CTAB. After 1 hour incubation at 37°C, the uptake of mannan-coated nanoparticles was 50% higher than that of the uncoated nanoparticles. At 4°C and after one hour, the binding of the mannan-coated nanoparticles by J774E was over 2-fold higher than that of the uncoated nanoparticles. This increase in J774E binding could be abolished by preincubating the cells with free mannan, suggesting that the binding and uptake were receptor-mediated. In conclusion, the nanoparticles were lyophilizable, and lyophilization was shown to enhance the stability of the nanoparticles. DSC provided evidence that the nanoparticles were not a physical mixture of their individual components. Finally, cell binding and uptake studies demonstrated that the nanoparticles have potential application for cell-specific targeting.     

Mechanotargeting: Mechanics‐Dependent Cellular Uptake of Nanoparticles

Targeted delivery of nanoparticle (NP)‐based diagnostic and therapeutic agents to malignant cells and tissues has exclusively relied on chemotargeting, wherein NPs are surface‐coated with ligands that specifically bind to overexpressed receptors on malignant cells. Here, it is demonstrated that cellular uptake of NPs can also be biased to malignant cells based on the differential mechanical states of cells, enabling mechanotargeting. Owing to mechanotransduction, cell lines (HeLa and HCT‐8) cultured on hydrogels of various stiffness are directed into different stress states, measured by cellular force microscopies. In vitro NP delivery reveals that increases in cell stress suppress cellular uptake, counteracting the enhanced uptake that occurs with increases in exposed surface area of spread cells. Upon prolonged culture on stiff hydrogels, cohesive HCT‐8 cell colonies undergo metastatic phenotypic change and disperse into individual malignant cells. The metastatic cells are of extremely low stress state and adopt an unspread, 3D morphology, resulting in several‐fold higher uptake than the nonmetastatic counterparts. This study opens a new paradigm of harnessing mechanics for the design of future strategies in nanomedicine.     

Uptake of trivalent chromium ions from aqueous solutions using kaolinite

The sorption of Cr(III) from aqueous solutions on kaolinite has been studied by a batch technique. We have investigated how solution pH, ionic strength and temperature affect this process. The adsorbed amount of chromium ions on kaolinite has increased with increasing pH and temperature when it has decreased with increasing ionic strength. The sorption of Cr(III) on kaolinite is endothermic process in nature. Sorption data have been interpreted in terms of Freundlich and Langmuir equations. The adsorption isotherm was measured experimentally at different conditions, and the experimental data were correlated reasonably well by the adsorption isotherm of the Langmuir, and the isotherm parameters (q(m) and K) have been calculated as well. The enthalpy change for chromium adsorption has been estimated as 7.0 kJ mol(-1). The order of enthalpy of adsorption corresponds to a physical reaction.     

Expansion or Contraction of Slit Pores Due to Gas Uptake

Adsorption inside a slit pore of flexible width w is explored, with a focus on how w varies as a function of the external pressure P of a gas in equilibrium with the adsorbate within the pore. The analysis is first carried out in general, using a minimization of the thermodynamic grand potential energy of the system. This leads to an equation predicting both the gas uptake N as a function of chemical potential ?? and the expansion (or contraction) of the pore in response to the adsorbate??s pressure. The resulting equilibrium behavior depends on the elastic parameters of the host material. Explicit results are derived for three adsorption systems: a low density fluid, Ar (a classical fluid at finite temperature T) in a graphite pore and ⁴He within a Au pore at T=0. The resulting behaviors include some situations where the pore expands and others for which it contracts. The difference arises from the sign of the thermodynamic response of the fluid as a function of slit width.     

碳污染对钛膜吸氢能力影响的研究

在钼基底上蒸镀钛膜，用乙炔（C2H2）在钛膜表面引入碳污染，用X射线光电子谱和俄歇电子谱研究钛膜表面的碳的化学状态，以及表面的碳污染对钛膜吸氢能力的影响。实验发现，碳在钛表面以两种到三种化学状态存在。碳在钛表面将使钛膜的吸氢能力下降，而且不同化学状态的碳对钛膜吸氢能力的影响也不同。实验结果表明，呈TiC状态的碳是降低钛膜吸氢能力的主要因素，其原因是它使解离吸附位置减少。     

Surface Functionality of Nanoparticles Determines Cellular Uptake Mechanisms in Mammalian Cells

Nanoparticles (NPs) are versatile scaffolds for numerous biomedical applications including drug delivery and bioimaging. The surface functionality of NPs essentially dictates intracellular NP uptake and controls their therapeutic action. Using several pharmacological inhibitors, it is demonstrated that the cellular uptake mechanisms of cationic gold NPs in both cancer (HeLa) and normal cells (MCF10A) strongly depend on the NP surface monolayer, and mostly involve caveolae and dynamin‐dependent pathways as well as specific cell surface receptors (scavenger receptors). Moreover, these NPs show different uptake mechanisms in cancer and normal cells, providing an opportunity to develop NPs with improved selectivity for delivery applications.     

Uptake Kinetics and Nanotoxicity of Silica Nanoparticles Are Cell Type Dependent

In this study, it is shown that the cytotoxic response of cells as well as the uptake kinetics of nanoparticles (NPs) is cell type dependent. We use silica NPs with a diameter of 310 nm labeled with perylene dye and 304 nm unlabeled particles to evaluate cell type‐dependent uptake and cytotoxicity on human vascular endothelial cells (HUVEC) and cancer cells derived from the cervix carcinoma (HeLa). Besides their size, the particles are characterized concerning homogeneity of the labeling and their zeta potential. The cellular uptake of the labeled NPs is quantified by imaging the cells via confocal microscopy in a time‐dependent manner, with subsequent image analysis via a custom‐made and freely available digital method, Particle_in_Cell‐3D. We find that within the first 4 h of interaction, the uptake of silica NPs into the cytoplasm is up to 10 times more efficient in HUVEC than in HeLa cells. Interestingly, after 10 or 24 h of interaction, the number of intracellular particles for HeLa cells by far surpasses the one for HUVEC. Inhibitor studies show that these endothelial cells internalize 310 nm SiO₂ NPs via the clathrin‐dependent pathway. Remarkably, the differences in the amount of taken up NPs are not directly reflected by the metabolic activity and membrane integrity of the individual cell types. Interaction with NPs leads to a concentration‐dependent decrease in mitochondrial activity and an increase in membrane leakage for HUVEC, whereas HeLa cells show only a reduced mitochondrial activity and no membrane leakage. In addition, silica NPs lead to HUVEC cell death while HeLa cells survive. These findings indicate that HUVEC are more sensitive than HeLa cells upon silica NP exposure.     

Size‐Dependent Cellular Uptake of DNA Functionalized Gold Nanoparticles

The extensive use of gold nanoparticles (AuNPs) in nanomedicine, especially for intracellular imaging, photothermal therapy, and drug delivery, has necessitated the study of how functionalized AuNPs engage with living biological interfaces like the mammalian cell. Nanoparticle size, shape, surface charge, and surface functionality can affect the accumulation of functionalized AuNPs in cells. Confocal microscopy, flow cytometry, and inductively coupled plasma mass spectrometry demonstrate that CaSki cells, a human cervical cancer cell line, internalize AuNPs functionalized with hairpin, single stranded, and double stranded DNA differently. Surface charge and DNA conformation are shown to have no effect on the cell‐nanoparticle interaction. CaSki cells accumulate small DNA‐AuNPs in greater quantities than large DNA‐AuNPs, demonstrating that size is the major contributor to cellular uptake properties. These data suggest that DNA‐AuNPs can be easily tailored through modulation of size to design functional AuNPs with optimal cellular uptake properties and enhanced performance in nanomedicine applications.     

Growth of Nanoscale Carbon Structures and Their Corresponding Hydrogen Uptake Properties

Carbon nanostructures have been synthesized using the chemical vapor deposition technique (CVD) on different catalysts, using ethylene, acetylene, or methane as the hydrocarbons. Morphological characterizations obtained using a scanning electron microscope (SEM) showed that the reaction products are carbon nanofibers (CNF) with an outer diameter that depends on the reaction conditions and nature of the reactants. Hydrogen uptake measurements, performed volumetrically in a Sievert-type installation, showed the quantity of desorbed hydrogen (for pressure intervals ranging from 1 to 100 bars) depends on the synthesis conditions and the treatment preceding the hydrogen absorption process. For carbon nanotubes that were preparedaccording to literature guidelines and obtained from ethylene on a Ni:Cu catalyst, the amounts of absorbed hydrogen were less than 1% by weight.

carbon nanostructures chemical vapor deposition hydrogen absorption SEM     

Growth of Nanoscale Carbon Structures and Their Corresponding Hydrogen Uptake Properties

Carbon nanostructures have been synthesized using the chemical vapor deposition technique (CVD) on different catalysts, using ethylene, acetylene, or methane as the hydrocarbons. Morphological characterizations obtained using a scanning electron microscope (SEM) showed that the reaction products are carbon nanofibers (CNF) with an outer diameter that depends on the reaction conditions and nature of the reactants. Hydrogen uptake measurements, performed volumetrically in a Sievert-type installation, showed the quantity of desorbed hydrogen (for pressure intervals ranging from 1 to 100 bars) depends on the synthesis conditions and the treatment preceding the hydrogen absorption process. For carbon nanotubes that were preparedaccording to literature guidelines and obtained from ethylene on a Ni:Cu catalyst, the amounts of absorbed hydrogen were less than 1% by weight. carbon nanostructures chemical vapor deposition hydrogen absorption SEM     

Uptake of dimercaptosuccinate-coated magnetic iron oxide nanoparticles by cultured brain astrocytes

Magnetic iron oxide nanoparticles (Fe-NP) are currently considered for various diagnostic and therapeutic applications in the brain. However, little is known on the accumulation and biocompatibility of such particles in brain cells. We have synthesized and characterized dimercaptosuccinic acid (DMSA) coated Fe-NP and have investigated their uptake by cultured brain astrocytes. DMSA-coated Fe-NP that were dispersed in physiological medium had an average hydrodynamic diameter of about 60 nm. Incubation of cultured astrocytes with these Fe-NP caused a time- and concentration-dependent accumulation of cellular iron, but did not lead within 6 h to any cell toxicity. After 4 h of incubation with 100-4000 μM iron supplied as Fe-NP, the cellular iron content reached levels between 200 and 2000 nmol mg?1 protein. The cellular iron content after exposure of astrocytes to Fe-NP at 4?°C was drastically lowered compared to cells that had been incubated at 37?°C. Electron microscopy revealed the presence of Fe-NP-containing vesicles in cells that were incubated with Fe-NP at 37?°C, but not in cells exposed to the nanoparticles at 4?°C. These data demonstrate that cultured astrocytes efficiently take up DMSA-coated Fe-NP in a process that appears to be saturable and strongly depends on the incubation temperature.