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. 2007 Nov;28(31):4600-7.
doi: 10.1016/j.biomaterials.2007.07.029. Epub 2007 Aug 1.

Protein adsorption and cellular uptake of cerium oxide nanoparticles as a function of zeta potential

Swanand Patil  1 , Amanda Sandberg, Eric Heckert, William Self, Sudipta Seal
Affiliations

Protein adsorption and cellular uptake of cerium oxide nanoparticles as a function of zeta potential

Swanand Patil et al. Biomaterials. 2007 Nov.

Abstract

The surface chemistry of biomaterials can have a significant impact on their performance in biological applications. Our recent work suggests that cerium oxide nanoparticles are potent antioxidants in cell culture models and we have evaluated several therapeutic applications of these nanoparticles in different biological systems. Knowledge of protein adsorption and cellular uptake will be very useful in improving the beneficial effects of cerium oxide nanoparticles in biology. In the present study, we determined the effect of zeta potential of cerium oxide nanoparticles on adsorption of bovine serum albumin (BSA) and cellular uptake in adenocarcinoma lung cells (A549). The zeta potential of the nanoparticles was varied by dispersing them in various acidic and basic pH solutions. UV-visible spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS) were used for the protein adsorption and cellular uptake studies, respectively. Nanoceria samples having positive zeta potential were found to adsorb more BSA while the samples with negative zeta potential showed little or no protein adsorption. The cellular uptake studies showed preferential uptake for the negatively charged nanoparticles. These results demonstrate that electrostatic interactions can play an important factor in protein adsorption and cellular uptake of nanoparticles.

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Figures

Fig. 1
Fig. 1
Standard curve for BSA concentration measurements. UV–visible spectroscopy measurements were carried out for known concentrations of BSA at the absorbance maximum of 280 nm. The absorption coefficient, ε was determined to be 0.7224 mg ml−1 cm−1.
Fig. 2
Fig. 2
Bright field HRTEM images of (a) microemulsion nanoceria (particle size: 3–5 nm) and (b) hydrothermal nanoceria (particle size: 8–10 nm). Arrows indicate the dominant 111 planes of the nanoparticles on the TEM grid which are observed when the nanoparticles are oriented along the [1 1 0] direction. Such orientation can be useful in achieving better protein adsorption.
Fig. 3
Fig. 3
Variation in the zeta potential of the nanoceria samples as a function of the pH of the buffer solution. Inherent zeta potential was negative for microemulsion nanoceria and positive for hydrothermal nanoceria. The isoelectric points (IEP) of 4.5 and 9.5 were observed for the microemulsion and hydrothermal nanoceria, respectively.
Fig. 4
Fig. 4
Amount of BSA adsorbed on the (a) microemulsion and (b) hydrothermal nanoceria samples as a function of its zeta potential. * Indicates no significant protein adsorption was observed for the sample. Positively charged nanoparticles favored BSA adsorption and showed increased protein adsorption with increasing zeta potential.
Fig. 5
Fig. 5
Cellular uptake of the nanoceria samples in A549 cells for different concentrations of nanoceria treatment. Inset gives the expanded plot of the results at smaller concentrations of nanoceria. * Indicates no significant cellular uptake was observed for the sample (details of the samples are given in Table 1). Cells treated with concentrations lower than 1.72 μg/ml of ceria nanoparticles had little or no cellular uptake.
Fig. 6
Fig. 6
Cellular uptake of the (a) microemulsion and (b) hydrothermal nanoceria samples in A549 cells versus their zeta potential. Samples with negative zeta potential showed higher cellular uptake compared to the one with positive zeta potential.
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