Biomedical Engineering Reference
In-Depth Information
siRNA (Ashley et al. 2012). In this study, the protocells conjugated with a
peptide that specifically recognizes hepatocellular carcinomas gained a 106-
fold improvement in efficacy compared to corresponding liposomes.
The cell internalization is the key step for gene delivery. It contains two
kinds of process receptor-mediated or non-receptor-mediated path with the
former more powerful. The particle size, shape, and surface charge are the
important parameters for controlling the cell internalization. Preliminary
studies indicated that the SiO
2
particles with a diameter of 200 nm were taken
up by HepG2 cells with a faster rate than that of other sizes. As an effective
receptor-mediated molecule, the Tat peptide was taken up with SiO
2
submi-
cron particles demonstrating a significant fast rate of cell uptake (Mao et al.
2010).
Moreover, it maintained effectiveness in the low temperature of 4°C.
Interestingly, PEGylated mesoporous silica nanoparticles made codelivery
of chloroquine and the nucleic acids with a significantly increased transfec-
tion and silencing activity, which in turn pointed out the orientation for the
combination of drug-nucleic acid therapies (Bhattarai et al. 2010).
7.3.4 Quantum Dots-Based Hybrid Materials for Gene Delivery
Quantum dots (QDs) are inorganic nanoparticles that exhibit superior opti-
cal properties such as stability toward photobleaching, controllable emission
bands, broad absorption spectra, and high quantum yields, which in turn
were widely used in biolabeling and bioimaging (Medintz et al. 2005; Kim et
al. 2010). In addition, they have aroused interest for gene delivery owing to
their good biocompatibility and monodispersity (Medintz et al. 2005).
Surface functionalization was achieved to hit better gene delivery. To
condense plasmid DNA into nanocomplexes, poly(2-(dimethylami-no)ethyl
methacrylate), a polycation, was used to modify ZnO quantum dot (Zhang
and Liu 2010).
To reduce the quantum yields of the QDs drop and cytotoxic-
ity following the conventional ligand-exchange reactions, QD nanoparticles
were coated with b-cyclodextrin and then coupled to amino acids (Zhao et al.
2011). Commonly used PEGylated nanoparticles not only reduce their non-
specific cellular uptake, which was mostly caused by surface protein adsorp-
tion in the serum, but also showed significantly reduced extent of cellular
uptake to targeted cells (Malek et al. 2008; Jeong et al. 2009). The shielding/
deshielding of cell penetrating peptides (CPP) was regulated by morpho-
logical transform of poly (N-iso-propylacrylamide) due to the lower critical
solution temperature. Based on this principle, the complex of quantum dots
modified with CPP exhibit an “on-demand” cellular uptake behavior (Kim
et al. 2010).
7.3.5 Iron-Based Hybrid Materials for Gene Delivery
Iron-based nanoparticle as a kind of magnetic nanoparticles has gained
considerable attention due to their promising efficiency, nontoxicity,
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