Transfection
System of Amino-Functionalized Calcium Phosphate Nanoparticles: In
Vitro Efficacy, Biodegradability, and Immunogenicity Study
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Abstract
Many methods have been developed
in order to use calcium phosphate (CaP) for delivering nucleotides
into living cells. Surface functionalization of CaP nanoparticles
(CaP NPs) with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was
shown recently to achieve dispersed NPs with a positive surface charge,
capable of transfection (<i>Chem. Mater.</i> <b>2013</b>, <i>25</i> (18), 3667). In this study, different crystal
structures of amino-modified CaP NPs (brushite and hydroxyapatite)
were investigated for their interaction in cell culture systems in
more detail. Qualitative (confocal laser scanning microscopy) and
quantitative (flow cytometry) transfection experiments with two cell
lines showed the higher transfection efficacy of brushite versus hydroxyapatite.
The transfection also revealed a cell type dependency. HEK293 cells
were easier to transfect compared to A549 cells. This result was supported
by the cytotoxicity results. A549 cells showed a higher degree of
tolerance toward the CaP NPs. Further, the impact of the surface modification
on the interaction with macrophages and complement as two important
components of the innate immune system were considered. The amine
surface functionalization had an effect of decreasing the release
of proinflammatory cytokines. The complement interaction investigated
by a C3a complement activation assay did show no significant differences
between CaP NPs without or with amine modification and overall weak
interaction. Finally, the degradation of CaP NPs in biological media
was studied with respect to the two crystal structures and at acidic
and neutral pH. Both amino-modified CaP NPs disintegrate within days
at neutral pH, with a notable faster disintegration of brushite NPs
at acidic pH. In summary, the fair transfection capability of this
amino functionalized CaP NPs together with the excellent biocompatibility,
biodegradability, and low immunogenicity make them interesting candidates
for further evaluation