Biomedical Engineering Reference
In-Depth Information
(Rosi et al. 2006 ). The researchers functionalized 13 nm gold particles with either
tetrathiol or monothiol-modified antisense ODNs. These nanoparticles showed
higher knockdown of EGFP gene expression when compared to antisense DNA
delivered by both commercial Lipofectamine and Cytofectin. Nagasaki et al.
reported gold nanoparticles complexed with PEG- b -PDMAEMA copolymers
(Oishi et al. 2006b ). These nanoplexes were then treated with either HS-siRNA or
siRNA, which attached to the particle through a thiol-Au linkage or electrostatic
interaction, respectively. All these nanoplexes showed the inhibition of luciferase
expression in human hepatoma cells, and the HS-siRNA-based vectors showed
more effective inhibition than the siRNA-based ones. Rotello et al. also reported the
inhibition of the DNA transcription of T7 RNA polymerase by gold particles with
terminal amine groups through Au-thiol linkage could be reversed by adding gluta-
thione in the system (Han et al. 2005 ).
5.2
Magnetic Nanoparticles
Magnetic nanoparticles (MNPs), such as magnetite and Fe 3 O 4 that have magnetic
properties and other functionalities have demonstrated to hold great promise as
multimodality imaging probes, and for tumor thermotherapy (Berry et al. 2003 ;
Hautot et al. 2003 ; Tartaj and Serna 2003 ). When their surfaces were multifuntion-
alized by biological or drug molecules, it is possible to achieve target-specific
diagnosis and therapy (Del Gaudio et al. 2005 ; Gupta and Gupta 2005 ; Neubergera
et al. 2005 ; Dobson 2006 ; Sunderland et al. 2006 ).
Numerous synthetic methods have been developed to synthesize MNPs (Laurent
et al. 2008 ), including co-precipitation (Jiang et al. 2004 ), sol-gel synthesis
(Solinas et al. 2001 ), microemulsion technique (Deng et al. 2003 ), sonochemical
reaction (Pol et al. 2005 ), hydrothermal reaction (Chen and Xu 1998 ), thermal
decomposition (Hyeon et al. 2001 ), electrospray synthesis (Basaka et al. 2007 ), and
laser pyrolysis approach (Veintemillas-Verdaguer et al. 1998 ).
The unfunctionalized iron oxide nanoparticles alone are cytotoxic. Therefore, a
suitable coating on the surface of MNPs is necessary to improve their biocompati-
bility and functionality. Silica-coated magnetite nanoparticles were prepared by
Bruce et al. and functionalized with amine groups (Bruce et al. 2004 ; del Campo
et al. 2005 ). In these studies, selected samples were comparatively examined for
their ability to adsorb, and subsequently elute, 2-deoxyguanosine-5-monophosphate
(GMP) and a range of sequence defined ODNs as well as sheared salmon sperm
DNA. It was found that magnetite could readily adsorb GMP via its phosphate
anion, whereas silica did not, due to the electrostatic repulsion between the nega-
tively charged surface of silica and the GMP. In comparison to commercially avail-
able silica-magnetite composite in terms of DNA adsorption and elution, the newly
fabricated material was observed to perform approximately 10% more efficiently.
Plank et al. have evaluated the viability of iron oxide nanoparticles as vehicles
for delivering nucleic acids into cells (Krotz et al. 2003 ; Plank et al. 2003a, b ).
They presented the concept of magnetofection and showed a strongly enhanced
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