Biomedical Engineering Reference
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a core of calcium phosphate surrounded by a lipid layer (Zhou
2010
). The
lipid-coated nano-calcium-phosphate (LNCP) particles were synthesized via etha-
nol injection: the lipid components (dimethyldioctadecylammonium bromide/
cholesterol/d-a-Tocopheryl Polyethylene Glycol-1000 Succinate) dissolved in
ethanol were injected into a solution containing a mixture of calcium acetate and
monosodium phosphate, sonicated and then dialyzed. The LNCP particles (on the
order of 100s of nanometers) demonstrate improved DNA transfection in a mam-
malian cell line as compared to the liposomal control (Zhou
2010
). The calcium
phosphate-liposomal systems have use in fluorophore (Chen
2010
) and drug delivery
(Schmidt
2002, 2004
) with applications in gene delivery (Zhou
2010
).
3.4
Layer by Layer Calcium Phosphates
Another approach to preparing calcium phosphate nanoparticles is the layer by
layer or multi-shell method in which molecules of interest are surface decorated on
a calcium phosphate core as opposed to encapsulated within the particle. In this
technique, calcium and phosphate solutions are coprecipitated and then stabilized
with DNA (Welzel
2004
; Sokolova
2006a, b, 2007a
) or oligonucleotides (Sokolova
2007b, 2010
).
The layer by layer method, with modifications, is also used to create double
and triple-shell layered nanoparticles (Sokolova
2006a, b
) as shown in Fig.
6
. For
the double-shell approach, a layer of calcium phosphate is precipitated on to the
Fig. 6
Schematic representation of the three different shell structures of calcium phosphate
nanoparticles synthesized by Sokolova
et al
.
The single-shell consists of a core of calcium
phosphate surrounded by a layer of DNA as a stabilizing agent. The double-shell structure has an
additional layer of calcium phosphate on top of the DNA layer of the single-shell method. The
triple-shell structure consists of the initial single-shell structure with an additional layer of calcium
phosphate stabilized with DNA (Reproduced from Sokolova (
2006a, b
). With permission)
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