European Cells and Materials Vol. 4. Suppl. 2, 2002 (pages 101-102) ISSN 1473-2262
SURFACE MODIFICATION OF SUPERPARAMAGNETIC IRON OXIDE
NANOPARTICLES AND THEIR INTRACELLULAR UPTAKE
Ajay K. Gupta and A. Curtis
Centre for Cell Engineering, IBLS, University of Glasgow, Glasgow, UK.
microemulsions) in N2 atmosphere. The
INTRODUCTION: The use of superparamag-
nanoparticles were coated with PEG and were
netic nanoparticles can contribute to a precise
characterized by various physico-chemical means.
delivery of drugs to an exact target site by
Lactoferrin was attached at the nanoparticle
application of external magnetic fields. Magnetic
surface by coupling the amine group of lactoferrin
nanoparticles having specific shape and size with
to the carboxyl group of MA-PEG coated particles
suitable surface chemistry can be used in numerous
in vivo applications such as drug delivery, cell
imide (EDCI). The effect of nanoparticles on cell
engineering, tissue repair or in diagnostics [1,2].
adhesion was determined with cell suspension
For these applications, the internalization of
incubated with/without nanoparticles. Infinity
nanoparticles into specific cells is the critical step
telomerase immortalized primary human
and severely limited by three factors: (a) a short
fibroblasts (h-TERT BJ1) cells were seeded with
blood half-life of the particles, (b) non-specific
nanoparticles for 24 hours onto 13mm coverslips.
targeting and (c) low efficiency of internalization
The cells were washed with PBS and stained for 2
of endocytosed ligands grafted on the
minutes in coommassie blue at room temperature.
nanoparticles. Rapid elimination of the
The cell populations were counted in three separate
nanoparticles from the blood stream after
light microscope fields with average normalized to
administration is due to their recognition by
control cell population.
macrophages of the mononuclear phagocyte
system (MPS). When the nanoparticles are covered RESULTS AND DISCUSSION: Magnetic
with adsorbed plasma proteins, they are quickly nanoparticle were synthesized in w/o micro-
cleared by macrophages before they can reach emulsions by using the inner aqueous core of the
target cells. One possible approach to increasing reverse micelles. The size and size distribution of
the blood circulation time of nanoparticles is to the particle was deter-mined by transmission
modify the surface of the nanoparticles by electron microscopy (TEM) studies (fig.1). The
hydrophilic polymers such as poly(ethylene glycol) picture shows that these particles have very small
(PEG). Nanoparticle surface covered with PEG is size (<10nm) with narrow size distribution.
biocompatible, i.e. non-immunogenic, non- The IR spectra of iron oxide is highly
antigenic and protein resistant . consistent with magnetite (Fe3O4) (bands at 408.9,
Iron can be transported in plasma complexed 560.0 and 585 cm-1). The spectra of PEG coated
with lactoferrin, a milk glycoprotein (Mw~90kDa), nanoparticles shows the small shift in the positions
having very high affinity for iron. The uptake of of the main peaks as compared to uncoated
iron by cells is mediated by cell surface receptors particles. This is due to the change in environment
and since, various cells have these type of of the particles after PEG coating. The size of the
receptors at their surface, the utilization of particles after coating is around 40-50nm as was
lactoferrin-nanoparticle complex seems to be a deter-mined by TEM and AFM studies. The core
promising pathway for the delivery of the drug/ shell structure of the nanoparticles can be seen
genetic material to different tissues of an organism. from AFM picture (fig.2).
In this study, PEG was coated on the surface of
Fig-3 shows the effect of magnetite and PEG
the magnetic nanoparticles, to disperse particles,
coated nanoparticles on the number of adhered
increase blood circulation times and improve their
cells after 24 hour incubation. It is evident from the
cell internalization. The particles were
figure that PEG coated magnetic nanoparticles did
characterized by various physicochemical means.
not appear to influence cell adhesion as compared
PEG coated nanoparticles were derivatized with
to control cell population. However cells exposed
lactoferrin to study their effect on cell adhesion.
to magnetite showed a reduction in adhesion to
METHODS: Highly monodispersed iron oxide glass of approximately 60%. This is because PEG
nanoparticles were synthesised by coprecipitation has uncharged hydrophilic residues and very high
of Fe3+ and Fe2+ salts (2:1 molar ratio) with sodium surface mobility leading to high steric exclusion
hydroxide by using the aqueous core of Aerosol- . In addition it has been demonstrated that
OT (AOT)/n-Hexane reverse micelles (w/o
particles with PEG-modified surface crosses cell
membrane in non-specific cellular uptake.
Lactoferrin is an iron binding protein, which has
major role in body’s defence mechanism through
its immune modulatory actions. It also has growth
regulatory functions in normal cells, coagulation
and cellular adhesion modulation. Figure-4 shows
the effect of lactoferrin binding at the surface of
uncoated particles on the number of adhered cells
as compared to control cell population.
CONCLUSIONS: Magnetic nanoparticles were
successfully prepared and modified with PEG and
characterized by FTIR and TEM studies. The
polyethylene glycol coated nanoparticles did not
appear to influence cell adhesion as compared to
control cell population. However the magnetic
particles showed a great decrease in cell adhesion
REFERENCES: (1) P.K. Gupta, C.T. Hung, Life
Sci.(1989), 44:175-186; (2) Gruttner C et al,
editors, Scientific and clinical applications of
magnetic carriers. New York: Plenum Press, 1997,
p53.; (3) S. Zalipsky, Bioconjugate Chem. (1995),
6:150-165. (4) M. Zhang et al, Biomaterials (1998)
ACKNOWLEDGEMENTS: This work was
supported by EC contract GRD5-CT2000-00375
project acronym: MAGNANOMED.