3.1.3 Ceramic NPs
Ceramic materials such as silica, zirconium phosphate, cerium oxide (CeO 2 , ceria),
aluminium oxide (Al 2 O 3 , alumina), yttrium oxide (Y 2 O 3 , yttria), etc. have received
very little attention for gene delivery applications. Of the various ceramic materials,
silica NPs were shown to protect the loaded DNA against denaturation induced by
changes in the external pH and temperature and, thus, have potential for use as nonviral gene delivery vectors. Consequently, several authors have used surfacemodified (multifunctional) silica NPs to deliver DNA [28–31]. Kim et al. [32]
have used silicon nanowires to deliver GFP-encoding plasmid DNA (pDNA).
Organically modified silica (ORMOSIL) NPs have also been used as a non-viral
vector for gene delivery [28, 33]. Unfortunately, silica NPs showed cytotoxicity
that increases with increase in dose, exposure duration and metabolic activity of the
cell [34]. Exposure of cells to silicon oxide resulted in increased activity of reactive
oxygen species (ROS) and reduced glutathione levels, indicating an increased
oxidative stress [35].
3.1.4 Carbon Nanofibers and Nanotubes
Carbon nanofibers and nanotubes have also shown great promise for non-viral gene
delivery. Cai et al. [36] used a technique called “nanotube spearing” wherein DNA
can be attached to nickel-embedded, elongated, magnetic nanotubes that can be
aligned parallel, like spears, to penetrate the cell membrane along the lines of a
magnetic flux. The penetration of cell membrane helps in delivery of the genes into
the cells. With this method, nearly 100% cell viability was reported with high
transfection efficiency [36, 37]. Vertically aligned carbon nanofibers have also been
used to deliver multiple genes into the cell [38, 39]. However, others have shown
potential toxicity of carbon nanofibers and nanotubes.
3.2 Organic NPs
3.2.1 Polyionic Bioreducible Polymers
Polycationic polymers having disulfite linkages in their polymeric structures have
been extensively investigated for use as non-viral gene delivery systems. These
polycations not only polyplex the negatively charged DNA to condense and protect
them against nuclease digestion but also release the loaded DNA intracellularly
upon breakage of disulfite linkages by the reducing environment of the cytoplasm.
These polycationic bioreducible polymers show reduced cytotoxicity and controlled
intracellular release of DNA, leading to increased transfection efficiency. Examples
58
P. Pushp et al.
Ceramic materials such as silica, zirconium phosphate, cerium oxide (CeO 2 , ceria),
aluminium oxide (Al 2 O 3 , alumina), yttrium oxide (Y 2 O 3 , yttria), etc. have received
very little attention for gene delivery applications. Of the various ceramic materials,
silica NPs were shown to protect the loaded DNA against denaturation induced by
changes in the external pH and temperature and, thus, have potential for use as nonviral gene delivery vectors. Consequently, several authors have used surfacemodified (multifunctional) silica NPs to deliver DNA [28–31]. Kim et al. [32]
have used silicon nanowires to deliver GFP-encoding plasmid DNA (pDNA).
Organically modified silica (ORMOSIL) NPs have also been used as a non-viral
vector for gene delivery [28, 33]. Unfortunately, silica NPs showed cytotoxicity
that increases with increase in dose, exposure duration and metabolic activity of the
cell [34]. Exposure of cells to silicon oxide resulted in increased activity of reactive
oxygen species (ROS) and reduced glutathione levels, indicating an increased
oxidative stress [35].
3.1.4 Carbon Nanofibers and Nanotubes
Carbon nanofibers and nanotubes have also shown great promise for non-viral gene
delivery. Cai et al. [36] used a technique called “nanotube spearing” wherein DNA
can be attached to nickel-embedded, elongated, magnetic nanotubes that can be
aligned parallel, like spears, to penetrate the cell membrane along the lines of a
magnetic flux. The penetration of cell membrane helps in delivery of the genes into
the cells. With this method, nearly 100% cell viability was reported with high
transfection efficiency [36, 37]. Vertically aligned carbon nanofibers have also been
used to deliver multiple genes into the cell [38, 39]. However, others have shown
potential toxicity of carbon nanofibers and nanotubes.
3.2 Organic NPs
3.2.1 Polyionic Bioreducible Polymers
Polycationic polymers having disulfite linkages in their polymeric structures have
been extensively investigated for use as non-viral gene delivery systems. These
polycations not only polyplex the negatively charged DNA to condense and protect
them against nuclease digestion but also release the loaded DNA intracellularly
upon breakage of disulfite linkages by the reducing environment of the cytoplasm.
These polycationic bioreducible polymers show reduced cytotoxicity and controlled
intracellular release of DNA, leading to increased transfection efficiency. Examples
58
P. Pushp et al.