RGDS-functionalized polyethylene glycol hydrogel-coated magnetic iron oxide nanoparticles enhance specific intracellular uptake by HeLa cells

Abstract

The objective of this study was to develop thin, biocompatible, and biofunctional hydrogel-coated small-sized nanoparticles that exhibit favorable stability, viability, and specific cellular uptake. This article reports the coating of magnetic iron oxide nanoparticles (MIONPs) with covalently cross-linked biofunctional polyethylene glycol (PEG) hydrogel. Silanized MIONPs were derivatized with eosin Y, and the covalently cross-linked biofunctional PEG hydrogel coating was achieved via surface-initiated photopolymerization of PEG diacrylate in aqueous solution. The thickness of the PEG hydrogel coating, between 23 and 126 nm, was tuned with laser exposure time. PEG hydrogel-coated MIONPs were further functionalized with the fibronectin-derived arginine-glycine-aspartic acid-serine (RGDS) sequence, in order to achieve a biofunctional PEG hydrogel layer around the nanoparticles. RGDS-bound PEG hydrogel-coated MIONPs showed a 17-fold higher uptake by the human cervical cancer HeLa cell line than that of amine-coated MIONPs. This novel method allows for the coating of MIONPs with nano-thin biofunctional hydrogel layers that may prevent undesirable cell and protein adhesion and may allow for cellular uptake in target tissues in a specific manner. These findings indicate that the further biofunctional PEG hydrogel coating of MIONPs is a promising platform for enhanced specific cell targeting in biomedical imaging and cancer therapy.

Keywords:

• PEG hydrogel
• surface-initiated photopolymerization
• nanoparticle encapsulation
• agglomeration

Acknowledgments

This study was supported by the College of Engineering at Koç University, Turkey, and by a Marie Curie international Reintegration Grant (FP7-IRG-239471) to SK. The authors would like to thank Dr Ugur Unal, Dr Ozgur Birer, Selcuk Acar, Ibrahim Hocaoglu, and Huseyin Enis Karahan for their help with XRD, SEM, ICP-OES, DLS, and AFM experiments. XRD and SEM analyses were performed at the Koç University Surface Science and Technology Center.

Disclosure

The authors report no conflicts of interest in this work.

Supplementary figures

Figure S1 Fourier transform infrared spectra of (1) acrylic acid N-hydroxysuccinimide, (2) acrylate-polyethylene glycol-N-hydroxysuccinimide, (3) acrylate-polyethylene glycol-arginine- glycine-aspartic acid-serine, and (4) arginine-glycine-aspartic acid-serine.

Figure S2 (A) Ultraviolet and visible spectra of (1) eosin only, (2) eosin-bound magnetic iron oxide nanoparticles (MIONPs), and (3) 3-aminopropylsilane-coated MIONPs; (B) Fourier transform infrared spectra of (1) 3-aminopropylsilane-coated MIONPs and (2) eosin-bound MIONPs.

Figure S3 Photobleaching of eosin after photopolymerization: (1) eosin only; (2) arginine-glycine-aspartic acid-serine-functionalized polyethylene glycol hydrogel-coated magnetic iron oxide nanoparticles (MIONPs); (3) polyethylene glycol hydrogel-coated MIONPs; (4) eosin-bound MIONPs in prepolymer solution before photopolymerization reaction.

Figure S4 (A) X-ray diffraction patterns of (1) lyophilized polyethylene glycol (PEG) hydrogel and (2) lyophilized PEG hydrogel-coated magnetic iron oxide nanoparticles (MIONPs); (B) lyophilized PEG hydrogel-coated MIONPs under the magnetic field of a magnet.

Figure S5 (A) Atomic force microscopy (AFM) height image of a 5 μm² area; (B) AFM height image of a 2 μm² area; (C) AFM phase image of a 5 μm² area; and (D) AFM phase image of a 2 μm² area.

Figure S6 HeLa cells stained with Prussian blue: (A) control; (B) 3-aminopropylsilane-coated magnetic iron oxide nanoparticles (MIONPs); (C) polyethylene glycol hydrogel-coated MIONP-60; (D) arginine-glycine-aspartic acid-serine-functionalized polyethylene glycol hydrogel-coated MIONP-60 (scale bar: 25 μM).

Note: Number in abbreviation MIONP-60 indicates corresponding illumination time in seconds.