Given that:

1. Once PEG is grafted on the GNPs surface, the cellular uptake

of the conjugate significantly decreases (Figure 4), and

2. The necessity of using PEG for in vivo GNPs application

Understanding the uptake mechanism is necessary to ultimately

enhance their uptake.

MOTIVATION

• Since uptake depends on energy, then the cellular

mechanism is RME.

• Compared with as made and RGD-PEG GNPs, it follows

the same trend.

Figure 5: An earlier model proposing that the low uptake is

due to inhibiting serum protein adsorption on the surface of

GNPs by PEG molecules [6].

• Using cell-targeting molecules (like RGD) is our best

option to enhance PEGylatd GNPs uptake.

DISCUSSION AND CONCLUSIONS

[1] Arnida, A. Malugin, and H. Ghandehari, “Cellular uptake and toxicity of gold nanoparticles in

prostate cancer cells: A comparative study of rods and spheres,” J. Appl. Toxicol., vol. 30, no. June

2009, pp. 212–217, 2010.

[2] B. D. Chithrani, A. a. Ghazani, and W. C. W. Chan, “Determining the size and shape

dependence of gold nanoparticle uptake into mammalian cells,” Nano Lett., vol. 6, no. 4, pp. 662–

668, 2006.

[3] B. Chithrani and W. Chan, “Elucidating the mechanism of cellular uptake and removal of

protein-coated gold nanoparticles of different sizes and shapes,” Nano Lett., vol. 7, no. 6, pp.

1542–1550, 2007.

[4] B. D. Chithrani, J. Stewart, C. Allen, and D. a. Jaffray, “Intracellular uptake, transport, and

processing of nanostructures in cancer cells,” Nanomedicine Nanotechnology, Biol. Med., vol. 5,

no. 2, pp. 118–127, Jun. 2009.

[5] H. Jin, D. a. Heller, and M. S. Strano, “Single-particle tracking of endocytosis and exocytosis

of single-walled carbon nanotubes in NIH-3T3 cells,” Nano Lett., vol. 8, no. 6, pp. 1577–1585,

2008.

[6] A. E. Carl D. Walkey, Jonathan B. Olsen, Hongbo Guo and W. C. W. and Chan, “Nanoparticle

Size and Surface Chemistry Determine Serum Protein Adsorption and Macrophage Uptake,” 2012.

[7] X. Liu, M. Atwater, J. Wang, and Q. Huo, “Extinction coefficient of gold nanoparticles with

different sizes and different capping ligands,” Colloids Surfaces B Biointerfaces, vol. 58, pp. 3–7,

2007.

[8] C. Cruje and B. D. Chithrani, “Integration of Peptides for Enhanced Uptake of PEGylayed

Gold Nanoparticles,” J. Nanosci. Nanotechnol., vol. 15, no. 3, pp. 2125–2131, 2015.

REFERENCES

MATERIALS AND METHODS

Measure dependence of cellular uptake of PEGylated GNPs on

energy:

• If it is directly correlated with the energy levels available to

cells, then the uptake mechanism is RME.

• Compare it with uptake of those that use RME, i.e as made

GNPs and Arginylglycylaspartic acid (RGD)-PEG GNPs.

HYPOTHESES AND OBJECTIVES

RESULTS

2227

573

835

243

43 130

1089

64

756

0

500

1000

1500

2000

2500

Control (37°C) Low temperature (4°C) ATP depletion

Nu

mb

er o

f G

NP

s p

er c

ell

GNPs PEG GNPs PEG-RGD GNPs

Figure 4: Number of GNPs entered HeLa cells under 3 different conditions overnight as assessed

by ICP-AES

BACKGROUND

Examining the Mechanism behind the Low Cellular Uptake of PEGylated Gold Nanoparticles : Is It Receptor Mediated Endocytosis?

By Rawan Ibrahem

Supervisor: Dr. B. Devika Chithrani Department of Physics, Ryerson University, Toronto, Ontario, Canada

• Visually examine cells under the low energy conditions.

• It was found that PEGylated GNPs uptake is cell line,

and GNP core size dependant [8]. So we need to extend

this experiment to include these parameters.

FUTURE WORK

Au

Citrate

stabilizing

layer

Au

Au Au

Gold Nanoparticles (GNPs) are:

• Easily tunable (size and shape)

• Easily modified/functionalized

• Easily imaged (due to high

contrast in TEM and HSI) and

detected.

• Biocompatible [1]

Figure 1: GNPs enter cells via RME with help from media

proteins adsorption on their surface[2]. RME is energy dependant

[3]. (Top figures from [4], ETM images from[5])

500 nm

Polyethylene Glycol (PEG) provides

GNPs with stealth property by

decreasing their uptake by macrophages

[6].

Au

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

450

469

488

507

526

545

564

583

602

621

640

Abso

rban

ce

Wavelength (nm)

GNPs

PEG GNPs

RGD-PEG GNPs

Figure 3:

Visualized

with Hyper

Spectral

Imaging System

GN

P S

UR

FA

CE

INC

UB

AT

ION

CO

ND

ITIO

N

×

ATP depletion

Low temperature

Normal temperature

(control) PEG-RGD

PEG

As made (Citrate)

30 µm

C B A

30 µm

C B A

DLS Mean

Diameter (nm)

53.5±1.3

58.4±1.4

59.1±1.6

GNPs PEG GNPs

RGD-PEG

GNPs

HeLa were incubated with GNPs overnight (8+hr)

Figure 2: GNPs

characterization

using UV-Vis

and DLS