The PEG is based on the following prior

The plan of using inverse microemulsion technique
to modulating the surface of magnetic nanoparticles with PEG is based on the
following prior observations: 1) Preparation of hydrophilic nanoparticles is done
in the aqueous cores of reverse micellar droplets. 2) The size of the particles
can be formulated  to 10-nm diameter by
regulating the size of the aqueous core of reverse micelles. 3) Since the
cross-linking and polymerization reactions occur in the aqueous core of reverse
micelles, it is available to coat the magnetic particles inside these
nanoreactors36 68 Highly monodispersed iron oxide nanoparticles were formed
by using the aqueous core of aerosol-(sodium dioctylsulphosuccinate)  (AOT) /n-Hexane reverse micelles (without
microemulsions) in N atmosphere. The reverse micelles have an aqueous inner
core, which can dissolve hydrophilic compounds, salts, etc. A deoxygenated
aqueous solution of the ferric and ferrous salts (molar ratio 2:1, 1 M) was
dissolved in the aqueous core of the reverse micelles formed by 0.05MAOT in
n-hexane. Chemical precipitation was done by using a 1 M deoxygenated solution
of sodium hydroxide. The reaction was performed in nitrogen atmosphere at low
temperature (4 C–6 C) with vigorous stirring. The hexane was evaporated and the
particles were recovered by precipitation in an excess of an acetone-methanol
mixture (9: 1 ratio), followed by dialysis using 12-kD cutoff dialysis membrane
against double-distilled water to remove unreacted iron salts. The surface of
the particles was neutralized with 0.01 M HCl, and the particles were dried in
a vacuum oven at 70 C–80 C. Particles were then coated with PEG to form the
stable dispersion of the magnetite nanoparticles.37 The magnetic
nanoparticles were prepared by coprecipitation of ferrous and ferric salts
solution by concentrated sodium hydroxide solution inside the aqueous cores of
reverse micellar droplets. Smaller and more uniform particles were prepared by
precipitation of magnetite at low temperature in the presence of nitrogen gas.
The synthesis of magnetic nanoparticles in oxygen-free environment prevents the
oxidation of iron oxide particles and decreases the size of the particles as
compared with methods without removing oxygen 38. Synthesis of hydrophilic
magnetic polymeric nanoparticles with magnetite core and polymeric shell is
possible using an inverse microemulsion polymerization process 39